DEPARTMENT OF THE INTEBIOK

BULLETIN

OF THE

GEOLOGICAL SURVEY

ISTo. 199

F f B, DESCRIPTIVE GEOLOOY, 19 

81 I O, UKDEROROUWD WATERS, 18

WASHINGTON

GOVERNMENT POINTING OFFICE 

1902
X

 s,
UNITED STATES GEOLOGICAL SURVEY

CHARLES D. WALCOTT, DIRECTOR

GEOLOGY

AND

WATER RESOURCES

OF THE

> SNAKE RIVER PLAINS OF IDAHO

BY

ISRAEL O. RUSSELL

WASHINGTONGOVERN MENT PRINTING OFFICE

1902

CONTENTS.

PAKT I. PHYSIOGRAPHY AND GEOLOGY. 

1 Page.

\ Introduction............................................................. 13

v/ Nature and object of the reconnaissance................................ 13

Topography.......................................................... 14

;< Climate........... 1.....;..............................'................ 17

Vegetation.............................. I............................. 22

Fauna ................................................................ 24

Soil ................................................................. 24

Streams.............................................................. 25

Springs................................................................ 26

^ Water power......................................................... 28

vt Irrigation and agriculture.......................... ................... 28

Stock raising........................................................'. 31

**' Mining ........................................._.................... 32

Towns............................................................. 32

Railroads............................................................ 33

^ Highways ..............................:...-.-..............-........ 33

Big, Middle, and East buttes .......................................... 34

^ General geology.......................................................... 38

Previous investigations ..................................... . 38

jrJf Pre-Tertiary formations............................................... 39

Granite........................................ .................. 39

Rhyolite.......................................................... 42

Quartzite ........................................................ 45

w Limestone .................................................:..... 46

Eocks of southeastern Idaho ...................................... 46

-^ Leading features of the geological structure......................... 46

i jC Early geological history of the Snake River Basin .................. 48

Tertiary and recent lacustral formations................................ 50

 i~ Payette formation................................................ 50

Idaho formation.................................................. 51

> ' Fossils............................................................ 56

Summary of lacustral conditions................................... 57

^ Economic problems .............................................. 58

, Possible eastward extension of the Tertiary sedimentary beds ....... 59

Snake River lava ..................................................... 59

 Extent and thickness............................................. 59

Relation to the Columbia River lava............................... 60

-i Hypothesis of fissure eruptions.................................... 61

Source of the lava ................................................ 63

5
6 CONTENTS.

General geology Continued. . Page. 1

Volcanoes among the mountains....................................... 66

Black Butte...................................................... 66 j

Martin lava stream............................................... 68 TrLittle Canyon lava stream ............ '. ........................... 69 '

King Hill lava stream ............................................ 70 ;

Blanche crater ................................................... 70

Summary............ ............................................ 71

Volcanoes on the Snake River Plains................................ v.. 71 t.

Cinder Buttes......_............................................. 72

Location.............:.-...........-..---...........-....-... 72

Tuff cones and craters ........................................ 72 <

Characteristics of ejected fragments............................ 74

Dust and lapilli ...................................... 74

Clots................................................ 75

Scoria............................................... 75

Bombs ..- -'....._....--.-.--..--.....-.....-...-...-. 75

Lava cakes........................................... 79 i<-

'Parasitic cones............................................... 80 v

Lava streams. .................................................. 82

Chemical composition.'.................................... 87 T

Surface features.......................................... 89 ^

Pahoehoe............................................ 91

Corrugations and arches.............................. 92 -*-

Aa .................................................. 97 ,'N

Lava caves. ................................................... 98 ^"

Depressions in the surfaces of lava sheets....................... 101

Margins of lava flows terminating on a plain.................... 102

Margins of lava flows terminating at the mountains............. 102

Relative age of the later lava flows ............................ 105

Relation of the Cinder Buttes to older volcanic eruptions........ 107 W.

Market Lake craters.................................. 108

Kuna Butte.......................................... 109 ^

Crater rings near Cleft................ ................ 110

Older craters and lava flows....................................... 112 ' x

Lava cones................................................... 112

Lava sheets.................................................. 112

Lava streams that flowed into water............................ 113 . y

Irregularities in the thicknesses of lava sheets .................. 117

Changes produced in lava sheets after cooling ...................... 118

Open fissures and faults. .....................................i 118 

Rock disintegration and decay ................................ 122 f^,

Canyons and waterfalls ....................................... 123

Spring-formed alcoves on the sides of canyons.................. 127

Lost rivers....................................................... 130

Upgrading streams............................................... 133

Soils...................................................................... 135 ^

Alluvial soils......................................................... 135

JEolian soils............'............................................. 136 v

Sand dunes.......................................................... 140

Residual soils.......................................'...-....-........ 141 V

Summary ........................................................... 141

Chemically-formed subaerial deposits................................. '..... 141

Recent soil erosion ....................................................... M5
CONTENTS. 7 

PART II. WATER RESOURCES.

Page..

Introduction............................................................. 147

Surface and subsurface water.......................................... 147

Springs.......................................................... 148

Hillside springs .............................................. 149

Canyon springs............................................... 150

Fissure springs............................................... 151

Cavern springs.................................... .......... 152

Temperature................................................. 152

Similarity between springs and wells .......................... 154

Relation of springs to climate, topography, and geology......... 154

Development of springs....................................... 156

Artesian wells.................................................... 156

Requisite conditions.......................................... 156

Available water on Snake River plains..................................... 158

. Surface streams ...................................................... 159

Springs .....................................-......-. - -------- ---- 162

Canyon springs................................................... 162

Fissure springs.................................................... 168

Wells................................................................. 171

Surface wells .................................................... 172

Rock wells....................................................... 172

Artesian wells.................................................... 174

Boise........................................................ 174

Bruneau Valley .............................................. 1.74

Little Valley.................................................. 175

Rock Creek Hills............................................. 176

Unsuccessful wells. .......................... ^................ 177

Imperfect casings.............................................. 178

Lewis artesian basin.......................................... 178

Shoshone artesian slope....................................... 180

Possibility of obtaining flowing wells in alluvial deposits........ 181

Probability of the presence of water beneath.the eastern portion

. of the Snake River Plains................................... 183

Conclusion..................................".........-.................... 184

Index ................................................................... 187
Vr 
ILLUSTRATIONS.

Page. 

PLATE <L Sketch map of southern Idaho, showing approximate extent of

Snake Ei ver lava.............................................. 13

*' . II. A, Snake River Canyon below mouth of Rattlesnake Creek, looking west; B, Snake River Canyon near Hagerman, Idaho, looking

northwest..................................................... 24

~frj III. The Thousand Springs, Snake River Canyon, Idaho............... 26

' IV. Shoshone Falls, Snake River, Idaho.............................. 28

V. A, East Butte, Idaho an old rhyolitic volcano surrounded by basalt; 

B, Big Butte, Idaho an old rhyolitic volcano surrounded by

* . basalt .......:-................................................ 34

VI. North wall of Snake River Canyon, Ada County, Idaho ........... 52

VII. South wall of Snake River Canyon, Halls Ferry, Idaho ........... 54

.^ VIII. A, Remnant of Snake River lava, King Hill Creek; B, Block of

columnar lava, Snake River Canyon ............................ 60

IX. A, Wall of Canyon Creek Canyon near Mountain Home, Idaho; 

B, North, wall of Snake River Canyon near mouth of Little Canyon, Idaho..................................................... 64

X. Cinder Buttes, Idaho, looking southeast.......................... 72

~* .XI. Sections of volcanic bomb, Cinder Buttes, Idaho ....'.............. 76

XII. Volcanic bombs, Cinder Buttes, Idaho ........................... 78

XIII. Blistered lava surface and corrugations on lava stream, Cinder 

^ Buttes, Idaho.................................................. 90

XIV. A, Lava expanded by steam on entering water; B, Pressure folds,

surface of recent lava flow, Cinder Buttes, Idaho ................ 92

XV. .4, Pressure ridge in Snake River lava near Market Lake Craters,

* Idaho; B, Pressure ridges in Snake River lava near Big Butte,

Idaho ....................................................... 94

-7 XVI. A, Market Lake Crater, Idaho; B, Stratified lapilli, Market Lake

, ., Crater, Idaho................................................. 108

' v n XVII. A, Kuna Butte, near Cleft, Idaho; B, Crater rings near Cleft, Idaho,

Kuna Butte in the distance ..................................... ] 10

X VIII. Lava cone, Snake River Plains, near Arco, Idaho.................. 112

s, XIX. A, Pillow-like folds in lava stream that entered water; B, Section of

spindle-like roll of lava from a lava stream that entered water ... 114

XX. Section of a lava stream that entered water, Bliss, Idaho .......... 116

XXI. Lava resting on undisturbed lake beds, Canyon Creek, Idaho....... 118

^ XXII. Twin Falls, Snake River, Idaho .................................. 124

XXIII. A, Fault scarp of basalt near Cleft, Idaho; B, Little Canyon, looking

south into Snake River Canyon, Idaho.......................... 126

XXIV. Blue Lake alcove, looking south into Snake River Canyon, Idaho.. 128 

XXV. A, Recent stream erosion near Howell, Idaho; B, Waterworn masses 

^ of basalt in Snake River Canyon near Hagerman, Idaho ......... 146

9
10 ILLUSTEATIONS.

Page.

Fig. 1. Map of crater rings near Cleft, Idaho ............................... 110

2. Section showing relation of hillside springs to water table............ 149

3. Section showing conditions favoring the occurrence of canyon springs. 150

4. Section of an artesian basin ........................................ 157

5. Section of an artesian wedge ....................................... 157

6. Section of an artesian slope ...................................... ^. 158

-
LETTER OF TRANSMITTAL.

-^ DEPARTMENT OF THE INTERIOR,

UNITED STATES GEOLOGICAL SURVEY,

Washington, D. 0., May U, 190*2.

SIR: I have the honor to transmit herewith the manuscript of a 

report on the geology and water resources of the Snake River Plains 

of Idaho, by-Israel C. Russell, with recommendation that it be pub- 

^»N Fished as a bulletin of the Survey.

The field work on which the report is based was done under the 

' supervision of the Division of Hydrography, and the paper was originally intended as a water-supply paper. Mr. Newell has decided, however, that the geological portions of the paper so far outweigh in 

importance and extent those relating strictly to hydrography that he 

^ recommends its publication as a bulletin rather than a water-supply 

paper.

Very respectfully,

C. W. HAYES, 

Geologist in Charge of Geology.

* Hon. CHARLES D. WALCOTT,

Director United States Geological Survey.

11

,U. S. GEOLOGICAL SURVEY BULLETIN NO. 199 PLATE I

SKETCH MAJ* OF SOTJTHEJROST IDAHO

Stowing ap.projcimate ex.ten.t of Snalce River lava

BY I.C..B.USSEI/L,

Scale 

10 o 10 20 so 40 sonnies
GEOLOGY AND WATER RESOURCES OF THE SNAKE 

RIVER PLAINS OF IDAHO.

Bv ISRAEL C. RUSSELL,.

i PART l-PHYSIOGRAPHY AND GEOLOGY,

INTRODUCTION.

NATURE AND OBJECT OF THE RECONNAISSANCE.

- The field work which furnished the basis for this report was carried 

on from July 5 to September 12, 1901, under the general direction of 

Mr. F. H. Newell, hydrographer of the United States Geological 

'Survey. The region examined is in southern Idaho, and is included

( for the most part in the area that is commonly termed the Snake 

River lava plains. On account of the general absence of water this 

region is also frequently designated the Snake River Desert. As

~>- the vast tract of approximately level country referred to is not 

entirely occupied by lava and as by far the greater portion of it is 

clothed with vegetation, and includes large tracts of open forest, it is

-~» evident that neither of the names just mentioned is appropriate, and 

to avoid conveying false impressions it will be termed in this report 

the Snake River Plains. The region does not constitute a single level

- plain, but exhibits considerable variation in altitude, slope, and character of surface, etc., in its various, although indefinitely bounded, 

parts. In a general way it may be considered as a series of plains

-* which merge one with another and have many characteristics in 

common. 

The main objects of the reconnaissance were to ascertain how far

r,- the geological conditions, particularly beneath the broad lava-floored 

plains bordering Snake River, favor the hope of obtaining flowing 

water by drilling wells, and where test wells should be put down in

-> order to determine the correctness of inferences based on geological 

and other conditions. As is well known, in order to ascertain the -~

artesian conditions in any region, it is necessary to have an intimate

V knowledge of the physical condition of the rocks below the surface,

especial!}' as regards the presence of alternate pervious and impervious

13
14 SNAKE RIVER PLAIN'S OF IDAHO. [BULL. 199.

beds and the position they occupy that is, whether they are horizontal, inclined, folded, broken, or in any way displaced. To obtain 

data of this nature in reference to the Snake River Plains, it is necessary to study the geolog}^ of a region having an area of 25,000 square 

miles, but owing to the limited time available only a small part of 

this task was undertaken.

Work was begun in the region about Boise, Idaho, which had pre- ^ 

viously been studied in detail by Dr. Waldemar Lindgren/' and carried 

eastward across Elmore, Lincoln, and Blaine counties and into Bingham 

County as far as Blackfoot. The route traversed was as follows: 

Snake River from near the mouth of Bruneau River to Shoshone 

Falls, with excursions southward into Owyhee and Cassia counties; 

from Shoshone Falls northward through Shoshone, and up Big Wood * 

River, for about 20 miles; northeastward along the west border of the 

Snake River Plains from Carey to Arco, thence eastward across the 

broad plain surrounding Big Butte and its two lesser companions to 

Blackfoot. At Blackfoot the party was disbanded. Included in this 

report also are certain observations made a year before, during a journey from Market Lake westward to Big Lost and Little Lost rivers, 

Birch Creek, etc., and back by the way of Mud Lake. :

The general routes followed during the two journeys outlined above 

are indicated on PL I. The distance traveled was about 550 miles v 

without reckoning numerous side excursions. The area more or less 

thoroughly examined includes about 1,200 square miles. As may be 

judged from these facts, the aim in view was a. geological reconnaissance, and not a detailed survey. It is hoped, however, that the main k,- 

object of the examination was accomplished, and that the numerous 

observations made will be of value, if for no other reason, because 

they pertain to a region the geology of which was previously almost ^.,

entirely unknown.

TOPOGRAPHY.

The Snake River Plains consist of a generally flat area bordered by * 

rugged mountains, and extend in a curved course concave to the 

north entirely across the southern portion of Idaho. The length of 

this belt measured along its medial line is about 350 miles and the 

width is generally from 50 to 75 miles. Its area, as estimated by * 

Lindgren, is 34,000 square miles. Snake River traverses this rudely 

crescent-shaped plain throughout its length in a great curve concave <r 

to the north, which .has a radius of some 175 miles. In a far-reaching 

view the flat country through which the Snake River finds its way 

presents the broader features of a vast level-floored stream-eroded " 

valley. A nearer acquaintance, however, shows that it is a built-up 

plain, formed principally of lava sheets, and does not owe its major 

surface features to erosion. v

a Geologic Atlas U. S., folio -15, Boise, Idaho, 1898. ' **
RUSSELL.] TOPOGRAPHY. 15

The best way, perhaps, to convey to the reader an idea of the leading topographic features of the country discussed in this report, and 

at the same time prepare the way for a more detailed study, is to sketch 

in outline the leading events in its geological history.

Southern Idaho is a region composed of geologically old rocks 

which formed an ancient land surface having a rugged relief. In the 

depressions of this surface during later geological time extensive lake 

and stream deposits and vast lava floAvs were spread out. The older 

rocks, sharply separated from the younger by a long time-interval, 

during which extensive movements in the earth's crust and deep 

erosion took place, are mainly granite, rhyolite, quartzite, and limestone. The youngest of these is probably the limestone, which is 

thought to be of Carboniferous age. These rocks were variously 

folded, faulted, and upheaved into prominent mountains, and deeply 

dissected by a large river with many tributaries which was long lived. 

The valley of the main stream, the ancient representative of Snake 

Eiver, became broad and had many important tributary valleys opening from it and extending far into the bordering mountains. The 

sharp-crested mountain spurs between the lateral valleys are in some 

instances prolonged far into the main depression.

After the topography had passed maturity that is, after the streams 

had excavated deep valleys, leaving sharp-crested and frequently serrate divides between them the main stream was obstructed, possibly 

by lava flows, but as seems more probable, by an upward movement 

of the rocks athwart its course in the region now included in western 

Idaho and eastern Oregon, and a lake was formed which occupied a 

large portion of the country now included in the Snake River Plains. 

This water body, named by Lindgren Lake Payette, received the sediment brought in by tributary streams and the dust blown out by 

volcanoes, and became deepty filled. These sediments, with a known 

depth of over 1,000 feet, are now well exposed, particularly in southwestern Idaho. In places they contain impressions of leaves of trees 

which grew on the borders of the old lake, the shells of fresh-water 

mollusks, the bones of land mammals, and other remains. The fossils 

record a Tertiary (Miocene) age.

Before Lake Payette came to an end the vast lava flows which now 

form such a conspicuous feature of the Snake River Basin began to be 

outpoured. In fact, the lava and the sediments of Lake Payette and 

of a later lake in the same basin, were contemporaneous, the lava and 

lake sediments being interbedded. Some of the lava flows entered the 

lake, and the occurrence of thick beds of volcanic fragments (lapilli), 

and of scoriaceous, glassy lava, with a torn and slag-like structure at 

the base of thick sheets of usually compact basalt, record the energy 

of the steam explosions that followed. Highly liquid lava continued 

to be poured out at various intervals from a large number of volcanic
16 SNAKE EIVEE PLAINS OF IDAHO. [BULL. 199.

vents, and spread out in the previously formed basin, making, in truth, 

lakes of molten rock. Besides these two processes of upbuilding, that 

is, sedimentation in lakes and the outpouring of lava which spread 

widely, there was a third, namely, the washing of debris from the 

uplands and its deposition in alluvial cover and widely extended sheets 

of sand, gravel, and silt in the valleys. In addition, there are widespread teolian deposits. The volcanic eruption continued after the 

lakes were either filled or drained, so that by far the larger portion 

of the Snake River Plains is directly underlain by sheets of basalt. 

The last of the extensive volcanic discharges happened in very recent 

times, and the process of stream deposition still continues.

The leading characteristics of the Snake River, Plains at the time of 

their formation still remain, but the sheets of lacustral and streamdeposited sediments, and the equally well-stratified layers of hardened 

lava, although for the most part still horizontal, have in places, more 

particularly in southwestern Idaho, been gently flexed and in certain 

instances, near the bases of the bordering mountains, broken and 

faulted. The principal changes in the surface features of the plains 

since their floors of lava were formed are due to erosion. These 

changes in general, however, have not been sufficiently pronounced to 

greatly alter the character of the broad, flat bottoms of the valleys, and 

to-daj7 , especially when viewed in the strong side light of early morning, or in the greatly lengthened purple shadows of evening, the plains 

seem to be absolutely level, and from many points of view of oceanlike extent.

The statement that the broad, lava-covered area on each side of 

Snake River throughout its course across southern Idaho is a plain is 

strictly true, so far as its prevailing and most impressive features are 

concerned, but it is a dissected plain. In places its surface is mildly 

uneven, and in other places excessively rough, owing to the character 

of the naked lava of which it is in part composed. It is marked also, 

as the practiced eye readily discerns, by many volcanic cones, and by 

broad, low elevations, formed of lava which was poured out from 

wi'dely separated vents and spread in various directions. In the central portion of the northeastern extension of the plains, midway 

between Snake and Big Lost rivers, there are three prominent buttes, 

two of which, Big and East buttes, are ancient rhyolitic volcanoes 

which rise as islands through the surrounding basalt.

The channels cut by streams-in the Snake River lava and the elevations that rise above its surface are in reality all minor features of the 

topography and do not detract from the impression, which is strengthened by familiarity, that the country bordering Snake River is essentially one vast plain from near the eastern border of Idaho to beyond 

the Oregon boundary.

The northern and southern borders of the Snake River Plains, or
KUSSEU,] TOPOGKAPHY. 17

more correctly, so far as the southeastern portion of Idaho is concerned, the east and west borders, are defined bjT rugged mountain 

ranges, several of which extend into the lava-covered country for a 

score or more miles in much the same manner that headlands and 

capes on a ragged coast project into the ocean. In several instances 

the lava poured out in the great central plain entered tributary 

stream-cut valleys and flowed up them from 20 to 30 miles, or until 

the rising gradient checked the advance of the tide of molten rock. 

The upstream ends of these lateral tongues from the main lava sheets 

are now usually covered with alluvium brought down by streams from 

higher portions of their courses. Alluvial fans and talus slopes are 

conspicuous features about the bases of the mountains, and chronologically both preceded and followed the widely extended lava sheets. 

This is an instructive fact, as the buried alluvial fans favor the passage of water from the mountains to the strata beneath the lava sheets 

flooring the plains.

The mountains to be seen from the Snake River Plains are bold and 

rugged, and as a whole present exceedingly sharp and serrate sky 

lines. The main range in south-central Idaho, known as the Sawtooth 

Mountains, expresses both in its name and its salient features the prevailing characteristic of the mountain crests throughout a large portion of the State. These pinnacled mountain tops are to a great extent 

composed of quartzite, but granite spires and prominent limestone 

ridges are in numerous instances nearly as sharply defined. The 

granite, even in valleys and on the immediate borders of the central 

lava plains, as, for example, between Boise and Mountain Home, presents a vast number of monumental and spire-like forms, which rise 

from widely expanded talus slopes.

The leading topographic features of southern Idaho may be summarized as deeply sculptured mountains surrounding a vast, nearly 

level, plain. The mountains rise boldly to a height varying from a 

few hundred to over 6,000 feet above the plain, and to elevations 

ranging very commonly from 7,000 to 10,000 or more feet above the 

sea. In its western part the plain has a general elevation of from 

2,900 to 3,200 feet, and in its broadest and most characteristic portion 

about Big Butte or between Blackfoot and the "Lost River country" 

ot: in general from 4,500 to 6,000 feet above the sea.

CLIMATE.

The climate of the Snake River Plains has for its leading characteristics aridit}^, prevailing high temperatures in summer, and severe cold 

in winter. One of the most marked features in the atmospheric conditions at nearly all seasons is the great range in temperature between 

day and night.

Bull, 199 02 2
18 SNAKE EIVEB PLAINS OF IDAHO. [BULL. 199.

The mean annual precipitation is about 13 inches, but many local 

variations occur. Nearly all the water that reaches the thirsty lands 

comes in winter and spring. During the growing season the soil is 

invariably parched, and successful agriculture without irrigation is 

seemingly impossible.

The summers are decidedly hot. Not infrequently for many consecutive days and even for weeks at a time the temperature during 

the hours of sunshine is over 100° F. and frequently reaches 105° F., 

and reports by local observers of 110° to 115° in the shade are not 

rare. Owing to the dryness of the atmosphere, however, the heat is 

seldom oppressive, and sunstroke is said to be unknown. Under the 

prevailingly clear skies in summer radiation is rapid and the nights 

are nearly always cool. Exceptionally warm nights occur when the sky 

is clouded, and radiation from the heated soil and rocks is checked.

In winter the atmosphere is even clearer than in summer, as the 

rain and snow remove the dust which is ever present when the soil is 

dry. The air is cold and the temperature has a greater daily range in 

winter than in summer, frequently falling far below zero, Fahrenheit. 

During the winter of 1898-99 the minimum temperature at Blackfoot 

was 30° F. and at Minidoka 28° F., while the year following, 

at Lost River, situated on the western border of the plains, in the 

entrance to a tributary valley, a temperature of 41° was recorded. 

During the year 1898 the last "killing frost" in spring at Blackfoot 

was on June 5, and the first frost during the succeeding fall was 

on September 29; at Minidoka the corresponding conditions occurred 

on May 14 and September 4. The snowfall, while aggregating during 

certain winters from 30 to 45 inches or more, varies greatly from 

year to year and from place to place, but seldom remains long on the 

ground. The sudden snowstorms are usually succeeded quickly by 

thaws during the hours of sunshine, and sleighing is seldom practicable. Warm winds, termed "Chinook winds," frequently occur in 

winter, during the prevalence of which snow, if present, disappears as 

if by magic, leaving the plains and the lower slopes of the bordering 

mountains bare. Large numbers of horses, cattle, and sheep are 

pastured on the plains throughout the winter, and require to be fed 

only during the more severe storms. In winter the skies, although 

frequently clouded, are usually clear, especially at night, and the stars 

are of phenomenal brillianc}^.

The prevailing winds, often heavily dust-laden, are from the west, 

and at many times, especially in the fall, blow with such strength and 

constancy as to become trying to a person's nerves. In summer and 

fall strong afternoon winds frequently occur, which die away at sunset; these are almost invariably from the west. These strong breezes 

are nearly as regular in their periods as the sea breezes on lands 

bordering warm seas, but instead of bringing a refreshing coolness
BUSBEU..] CLIMATE. 19

they are frequently hot, and to one facing them seem the breath of 

a furnace. On the broad plains miniature whirlwinds are of frequent occurrence, particularly on hot afternoons, and the dust carried 

upward by them forms tall columns with hollow centers, in which, 

when the}"- are near the observer, a spiral motion can be discovered. 

These dust columns are sometimes 2,000 or 3,000 feet high, and are a 

characteristic feature of the parched desert-like plain when heated by 

the intense summer sun.

Owing to the great extent of the plains, their variations in altitude, 

the influence of the adjacent mountains, and other factors, there are 

many local variations in the climatic conditions. The most marked 

differences are in temperature and in the length of time the land is 

snow-covered. These variations are most marked in the broad, nearly 

flat areas forming the general surface and in the limited tracts of level 

land in the canyons and canyon-like valleys. In the canyon of Snake 

River and its tributaries below Shoshone Falls the atmospheric conditions are markedly different from those on the surfaces of the adjacent 

plains. In the canyons the temperature in summer, owing to the 

shelter from the winds .afforded by the bordering precipices and the 

reflected and radiated heat from the black rocks, is usually much 

higher than on the open plains. Cool breezes frequently blow along 

the river, however, tempering the intense heat. Again, in winter, 

owing largely to the ameliorating influence of tho river, as well is the 

protection afforded by the bordering cliffs from the freezing blasts 

that sweep over the plains, the mean daily and monthly temperatures 

in the canyon are considerably higher than on the neighboring undissected plain. Snow seldom lies on the ground in the canyon bottoms 

for more than a few days at a time.

The canyons furnish many favorable places for orchards, vineyards, 

and gardens, not only on account of the intense heat and strong light 

during the growing season, when they are essentially hothouses, but 

because water from springs with a temperature of about 60° F. can 

frequently be had for irrigation.

In brief, the Snake River plains present a typical illustration of an 

insular or continental climate, such as is characteristic of regions of 

mild relief, remote from the tempering influences of the ocean, and 

deprived of their requisite share of moisture by the presence of lofty 

mountains in the path of the prevailing winds.

One result of the climatic conditions, and especially of the drjmess 

of the air, is the healthfulness of the land. So far as I am able to 

judge, it is a region exceedingly favorable to persons suffering from 

disease of the lungs.

To lovers of nature and all who rejoice in scenes of natural wildness 

unmodified, or what is too frequently essentially the same thing, 

unmarred by the hand of man, the plains of southern Idaho present
20 SNAKE KIVER PLAINS OF IDAHO. [BULL. 199.

exceptional attractions. One must become familiar with their characteristics, however, and learn to judge them by their own standard 

before their beauties are fully revealed. To the traveler from humid 

lands, where every hillside is clothed with verdure and every brook 

flows through a shadowy vale, they will at first seem repellent deserts, 

on which a long sojourn would be intolerable. This, I think, will be the 

first impression, especialty if beheld at noontide in summer or beneath a 

gray wintry sky. But to one who rides for weeks or months across 

their seemingly boundless surfaces, sleeping at night beneath the stars, 

they are found to have charms unthought of by the casual passer-by. 

In the glare of the unclouded summer sun the plains are featureless, 

or perhaps their expression is distorted and rendered grotesque or 

vague and meaningless by the deceptive mirage. At such .time the 

flat land vanishes in distant haze, and the bordering mountains, if visible at all, are but uncertain flickering shadows on a glowing sky. In 

the clear side lights of early morning, however, all uncertainty and 

indefiniteness vanish. The flat land has details everywhere on its surface. The mountains stand boldly forth as sculptured forms of amethyst and sapphire, every line on their deeply engraved slopes, 

although leagues distant, clearly visible. When the sun is high in 

the cloudless heavens the plains are gray, russet brown, and faded 

yellow, but with the rising of the sun and again near sunset the}'" 

become not only I illiant and superb in color, but pass through 

innumerable variations in tone and tint. When the approaching 

dawn is first perceived, the sun seemingly a great fire beneath the 

distant edge of the plain, a curtain is quickly drawn aside, revealing a 

limitless picture suggestive of the view a mariner sometimes has on 

approaching a bold coast while the actual shore line is still below the 

horizon. The distant mountains, rising range above range and culminating in some far-off sun-kissed peak, are of the most delicate blue, 

while all below is dark and shadowy. As the sun mounts higher the 

colors deepen, becoming A'iolet and purple, of a strength and purity 

never seen where rain is frequent. Purple in all its rich and varied 

shades is the prevailing color imparted to arid lands when the sun is 

low in the heavens. As the dawn passes and the light becomes 

stronger the rich hues fade, the mountains recede and perhaps vanish 

in the all-pervading haze, details become obscure even in the immediate foreground, and the eye is pained by the penetrating light. The 

shadows, if canyon walls are near, are sharply outlined and appear 

black in contrast with the intense light reflected from the sun-bathed 

surfaces.

As evening approaches there is a gradual change from glare to 

shadow. The broad plains become a sea of purple on which float the 

still shimmering mountains. The shadows creep higher and higher, 

until each serrate crest becomes a line of light, margining rugged
RUSSELL.] CLIMATE. . 21

slopes on which every line etched through centuries by rills and 

creeks reveals its history. The mountains seemingly grow in stature 

and unfold ridges and buttresses separating profound depths. One 

marvels at the diversity and strength of the sculpturing on what but 

a few moments before appeared flat, meaningless surfaces.

As the sun sinks lower there are, perhaps, a few clouds near at 

hand which are seemingly burned or rendered molten by the intense 

heat, but more frequently only a nebulous glory appears in the vaporless air. The violet and purple shadows creep higher and higher on 

the mountain slopes, and at last each crest and pinnacle, still sharply 

outlined, becomes but a shadow. During the cloudless summer the 

glories of sunset are on the earth, not in the sky. As the sun disappears a well-defined twilight arch arises in the east, the shadow of the 

earth on the dust particles in the air. The upper margin of the arch 

is at first well-defined, but fades as it rises and is lost when the stars 

begin to gleam in the dark heavens. The cool, star-lit summer nights 

are wonderfully magnificent. The heavens, without a cloud, are filled 

from horizon to zenith with stars which burn with a steady planetary 

light, such as is seen in our eastern humid lands only during clear 

winter weather.

Although the summers in southern Idaho, in common with the rest 

of the great arid region of which it is a part, are characteristically 

cloudless, sometimes completely so for many days and even a week or 

two, yet as fall approaches vapor banks appear and the glory in the 

heavens and the magnificence of the earth increase a thousand fold, 

surpassing the ability of even a poet to describe. One feature of the 

weather in early fall is the gathering of thunder storms about the 

mountains and their advance with fierce lightning and' deep-toned 

thunder over the plains, where they melt away and disappear ineffectually in the drier air. At times these struggles of opposing forces are 

repeated daily, and a more advanced position is gained each afternoon 

by the invading storm, until a few pattering rain drops fall, or perchance a brief drenching downpour occurs on the thirsty sagebrush 

lands. More often, however, the vast banks of brilliantly illuminated 

cumulus clouds are festooned belowv with descending rain sheets 

which fail to reach the earth. Accompanying these inefficient thunder squalls there sometimes comes a heavily dust-laden wind which 

advances across the land like a wall of blackness, obscuring the landscape, and as it passes the observer producing a twilight even when 

the sun is high in the heavens. At such times the eyes are blinded 

and the throat is choked \>y the all-penetrating dust particles. These 

dust storms, unaccompanied b}^ rain, explain the origin of the fine 

yellow soil which covers much of the plains, mantles the sides of isolated volcanic hills, and extends far up the neighboring mountain 

slopes.
22 StfAKE RIVER PLAINS OF IDAHO. [BULL. 194.

The reader will perhaps think that I have devoted too much space 

in attempting- to record some of the leading features of the climate 

and weather of this region, but it is to be remembered that there is an 

intimate connection between the surface features of a region and the 

climatic conditions to which it is exposed. Not only is the nature and 

origin of the soil of the Snake River Plains to be looked for in part at 

least in the work of the winds, but the canyon walls, the widely 

spreading alluvial fans, and the details in the bordering mountains 

would not be what we now find if humid instead of arid conditions had 

long prevailed. Still more quickly responsive to climatic conditions 

is the vegetation which soils are permitted to produce.

VEGETATION.

The ever-present and characteristic plant of the Snake River Plains 

is the sagebrush (Artemisia tridentatd), which grows abundantly and 

we might say luxuriantly in the dry soil, from the bottom of the 

Snake River Canyon up to an elevation of some 2,000 or 3,000 or more 

feet on the mountains bordering the plains. It covers the broad arid 

valleys almost complete^ and is seldom lacking over any extensive 

area, except where fires have recentty occurred or cultivated fields 

supplanted it. On the plains in summer fire sometimes sweeps 

through the sagebrush in much the same manner that it does over the 

prairies, and "burns" are produced. The "sage," in the localities 

most favorable to its growth, attains a height of about 10 feet, but 

usually is not over 3 feet high, the clump of bushes being commonly 

6 to 8 feet apart. One can ride or walk over the sagebrush plains 

with but little difficult}^. The light grayish-green leaves of this 

ubiquitous plant give color, or perhaps more properly lack of color, 

to the plains and enhance their monotony. Although the Snake 

River Plains are frequently termed a desert, the name is true only in 

the sense that they are practically without water. There is comparative^ little of the surface that is entirely destitute of plant life. In 

fact the flora is found to be abundant and varied, if one examines it 

closely. There are many lovely plants that blossom in early spring, 

filling the air with fragrance, and in summer and fall the yellow of 

sunflowers and of the still more plentiful "rabbit brush" (Bi.gelomci 

graveolens), a relative of the goldenrod, frequently give broad dashes of 

brilliant color. Beneath the sagebrush in a state of nature nutritious 

bunch grass grows abundantly and still furnishes pasturage where 

sheep have not ravished the land. Where the plains are broadest, 

that is to the north of the Oregon Short Line Railroad and especially 

in the vicinity of the three steptoes, Big, Middle, and East buttes, 

much of the land is without sag'ebrush and in the condition of a rolling 

prairie which supplies excellent winter pasturage.

One of the surprises met with during the reconnaissance which fur-
RUSSELL.] VEGETATION. ; -23

nished the basis of this report was the finding of a true forest over 

several hundred square miles of the surface which is designated on 

many maps as the "Snake River Desert." On the three prominent 

buttes situated in the central part of the plain between Blackfoot 

and Big Lost River there is a thrifty growth of junipers. This 

forest extends far out on the plain lying east of the buttes, and 

covers in all about 175 square miles. The trees, although small, seldom, in fact, attaining a height of over 15 or 20 feet, are thrifty and 

are valuable for fence posts, firewood? etc. On Big Butte there is, in 

addition to a few junipers, a vigorous growth in the most favorable 

places of pine and young firs. An older forest, destroyed by fire, is 

still standing, the trees, principally pines and firs, being from 30 to 40 

feet high. The most thoroughly tree-covered portion of the plains, 

however, is situated near their western border, and extends from a 

point a few miles south of Arco southwestward about 50 miles, in 

an irregular belt from 10 to 15 miles broad. This tract, about 800 

square miles in area, is an open forest, consisting principally of pine 

and fir. This forested area embraces the Cinder Buttes, and there 

touches the mountains bordering the Snake River Plains on the west. 

In all other portions of the west border of the tree-covered region it 

is separated from the mountains by black, barren lava flows of recent 

date. Where the trees grow there is a fine, rich soil covering old lava 

sheets, and among the trees luxuriant bunch grass clothes the ground. 

This tree- and grass-covered region, instead of being a desert, is parklike in appearance, and, in reality, is a beautiful and attractive country.

Like many other extensive portions of the Snake River Plains, this 

region would become highly fruitful if water could be had for irrigation, and it is by no means certain that wheat and other grain will not 

grow without artificial watering. It is remote from streams and 

springs, however, and owing to this fact it has been saved from the 

destructive inroads of domestic sheep and its primitive wildness has 

been preserved.

To the west of East and Middle buttes there is a tract of about 200 

square miles which is without trees or bushes, even the sagebrush 

being absent, but it is clothed with luxuriant bunch grass, and furnishes iis typical an example of a rolling prairie as one can find in the 

far West. 

During the winter months, when snow lies on the Snake River 

Plains, tens of thousands of sheep are driven there for pasturage, and 

thrive on the withered grass and nutritious shrubs. Snow supplies 

the place of water, or else, on melting, fills small depressions and forms 

water pockets. The area of these natural pastures is so great, however, that but little damage has as yet been done, except in the neighborhood of the streams which flow down from the mountains.
2 SNAKE BIVER PLAINS OF IDAHO.

FAUNA.

On the plains, more especially in the broader portions in.the vicinity of the three prominent buttes that break their monotony, big 

game is still to be found. Antelope roam over them throughout the 

year, while deer and elk find there a safe winter range. The mountain sheep is also present in winter, and the mountain goat is reported '» 

to have been met with. The great horn cores of the mountain sheep 

are occasionally to be seen bleaching among the clumps of sage bushes. 

Occasionally, also, the horns and bones of the bison are found, show- i* 

ing that southern Idaho was within the former range of that species. 

Besides the animals just mentioned, the plains are visited by bears, 

wolves, lynxes, foxes, skunks, etc., and the coyote is only too abundant. Ducks, geese, and other birds visit the occasional ponds and 

streams, particularly along Snake River and on the west side of the 

plain in the Lost River country. Grouse of several species are com- *" 

mon, and smaller birds are by no means rare. The life of the isolated 

timbered region referred to, and in fact of the Snake River Plains 

generally, has not been critically studied, and no doubt has many 

novelties with which to reward the naturalist. t

SOIL.a v

Although the soil of the Snake River Plains has well-marked variations, it may be said that in general, and in fact almost everywhere, it 

is fertile and needs but the requisite moisture to enable it to produce 

a strong growth of either native or cultivated plants. So generally is ^ 

the condition of the soil favorable to agriculture that it is easier to v 

designate the exceptions than to describe the favored localities. About 

the border of the plains the material washed down by streams from >* 

the mountains is in numerous localities a coarse gravel, but although 

requiring much water when irrigated such land is not infertile. Over 

large areas the soil covering is thin and rock fragments are so numerous that under the most favorable conditions for irrigation the land 

could not be economically cultivated. Portions of the plains, too, are ' 

covered with recent lava on which practically no soil has accumulated. +.. 

Examples of such black, rugged surfaces may be seen along the Oregon 

Short Line Railroad between American Falls and Miriidoka, and again 

to the north of Shoshone, but the largest tract of recent lava occurs 

on the west side of the plains opposite Blackfoot, near the Cinder 

Buttes. Comparatively small areas of a similar character .occur near 

Market Lake and between Big and Middle buttes. In the western (^ 

portion of the Snake River Plains, south of Snake River, extensive 

areas of white lake beds are present, but are usually covered with 

yellowish, quartzite cobbles. Drifting sand occurs, particularly to the ^

d See also pp. 135-141.
U. S. GEOLOGICAL SURVEY BULLETIN NO. 199 PL. I

A. SNAKE RIVER CANYON BELOW MOUTH OF RATTLESNAKE CREEK, LOOKING

WEST.

K. SNAKE RIVER CANYON NEAR HAGERMAN, IDAHO, LOOKING NORTHWEST.
BUSSELL.] STREAMS. 25

northeast of Market Lake, and small tracts of dunes are present elsewhere. In general, however, the soil of the plains is a fine, yellowishwhite, silt-like material, largely a dust deposit, which mantles the surface not only on level tracts but covers hills and broad depressions 

alike. This material is similar to the celebrated loess of China, except 

that it usually occurs as a comparatively thin layer, and resembles 

also the deposit bearing the same name in the Mississippi Valley. Like 

each of these formations, it is of exceptional fertility if properly 

irrigated.

STREAMS.a

The Snake River Plains lie entirely within the hydrographic basin 

of Snake River, or the Lewis Fork of the Columbia, as it is sometimes 

termed. It is much to be desired that this great stream might be 

named Lewis River, in honor of one of the two bold explorers who 

secured the far northwest for the United States. The Snake or Lewis 

River has its headwaters in Wyoming, near the Yellowstone National 

Park, and drains all of southern and central Idaho. It flows across 

the southern part of the State in a great curve, concave to the north, 

to the Idaho-Oregon boundary, where it turns abruptly northward, as 

is indicated on the map (PI. I). Its mean discharge, as determined by 

trie hydrographic division of the United States Geological Survey in 

1897, at Montgomery Ferry, midway between American Falls and 

Shoshone Falls, is 10,064: cubic feet per second; the maximum being 

in May and June, when it reaches about 26,000 cubic feet per second, 

and the minimum in August, September, or October, during which 

months its volume is approximately 4,400 cubic feet per second. 6

In southeastern Idaho many streams join the Snake on the east. Of 

these the South Fork and Blackfoot River are the most important. 

Several perennial tributaries come to the main river from the south, 

such as the Portneuf, Salmon, and Bruneau rivers, besides a number 

of creeks which flow only during the winter or in May and June, when 

the snow on the mountains is melting. All of the tributaries from the 

south are small in volume, particularly in summer. The Bruneau 

would be an important exception to this rule, as it is supplied mainly 

by springs, if its waters were not so largely used for irrigation.

One of the most significant peculiarities of Snake River is the fact 

that between Henrys Fork, on the extreme northeast, and the mouth of 

Boise River, at the Idaho-Oregon boundary, a distance measured along 

the general course of the river of about 350 miles, it does not receive 

a single perennial tributary from the mountains to the north of the

a See also p. 159.

6 Such accurate data as are available concerning the hydrography of Snake River and its tributaries 

in the portion of its course bordered by the plains of southern Idaho, may be found in the reports of 

the hydrographic division of the U. S. Geological Survey, particularly in the Twentieth Annual Report 

of that survey, pages 61,469-491; and in the reports of the State engineer of Idaho, especially the biennial report for the years 1899-1900, published at Boise.
26 SNAKE EIVER PLAINS OF IDAHO. [BULL. 199.

bordering plains. A possible exception to this statement is furnished 

by Malade River, which would perhaps reach the Snake in summer if 

its waters were not used for irrigation. The fact that Snake River 

does not receive a perennial tributary from the north throughout the 

portion of its course just indicated is the more remarkable when it is 

remembered that this part of its basin is largely occupied by lofty 

mountains, on which the mean annual precipitation is probably greater 

than on the less extensive and lower mountains, in which the streams 

coming from the south, such as the Portneuf, Salmon, and Bruneau, 

have their sources. The principal reason for the absence of surface, 

tributaries to the Snake on the north is that broad lava plains intervene 

between it and the mountains, and all of the water which flows down 

to the plains or falls on their surfaces is either evaporated or lost in 

the cellular and fissured lava.

Some of the streams flowing southward from the mountains of central Idaho, as Camas Creek and Little Lost and Big Lost rivers, form 

temporary lakes on the lava plains, from which the water is removed 

by evaporation, or descends into fissures in the underlying rocks and 

joins the underflow. To a large extent, however, the disappearance 

of streams from the mountains on reaching the plains is due, as just 

suggested, to the descent of the water into fissures and cellular lava, 

or into beds of gravel and sand that underlie the lava sheets. The 

streams, to be sure, tend to fill the openings in their beds with silt, 

but the extent of the lava-covered country they have to cross in order 

to reach the master stream to which they would be expected to flow 

is so great that the task of filling the cavities in the rocks is as yet incomplete. The water which disappears below the surface, particularly 

on the northern border of the Snake River Plains, to a large extent 

emerges again in the canyon of Snake River.as springs.

SPRINGS."

One of the remarkable features of Snake River Canyon is the 

abundance of large springs which pour out from its northern wall, 

especially in the portion of its course between Shoshone Falls and 

Bliss. The aggregate volume of these springs is many thousand cubic 

feet per second. They flow steadily without observed fluctuations in 

volume throughout the year. During August and September, when 

the Snake is low, their combined volume is estimated to be equal 

to if not greater than that of the river itself where it passes over 

Shoshone Falls. Perhaps the finest known exhibition of cataracts 

formed by springs of large volume issuing from rocks far up the 

faces of nearly vertical precipices is furnished at what is known as 

The Thousand Springs, situated on the northern side of Snake River

« See also pp. 162-171.
U. S. GEOLOGICAL SURVEY lULLETIN NO. 199 PL. I

THE THOUSAND SPRINGS, SNAKE RIVER CANYON, IDAHO.
RUSSELL.] SPRINGS. 27

Canyon, near the town of Hagernian, between Salmon Falls and the 

point where Salmon River enters from the south. Views of a portion 

of the springs, which leap from the canyon wall at this locality and 

descend as white sheets of foani and spray over the verdure-covered 

precipices below, are shown on PI. III. The more general of the two 

views (PL III, _Z?) was taken before attempts had been made to utilize 

the springs, and indicates the natural conditions; PI. Ill, A, is from a 

photograph taken in August, 1901, and shows a portion of the springs 

where their waters had been concentrated by a flume. In recent 

years tunnels and flumes have been constructed, which concentrate the 

waters and make their volume appear even greater than is suggested 

by the first of the views here presented. Most of the water descends 

over the face of a vertical wall of clay and lapilli from the cut edge of 

a layer of cellular scoriaceous basalt, which has an elevation of about 

185 feet above the base of the precipice. The water does not make 

the descent in a single leap, but makes cascades of remarkable beauty 

and novelty and is churned into foam by its contact with the rocks. 

The volume of water has never been accurately measured, but within 

a space about half a mile in length at The Thousand Springs proper is 

estimated by Mr. A. Ferguson, a hydraulic engineer familiar with the 

locality, at 20,000 miner's inches (or approximately 500 cubic feet) per 

second.

West of The Thousand Springs the water-bearing layers which 

furnish water at this place are inclined and pass below the level of the 

river, but another similar but higher layer appears which continues 

to Bliss, a distance of about 18 miles. Throughout the length of its 

outcrop in the canyon wall copious springs are abundant. At many 

other localities between The Thousand Springs and Shoshone Falls 

there are water-bearing layers in the canyon wall and large springs 

pour out. The greatest of these fountains are situated at the heads of 

lateral alcoves or small side canyons opening into Snake River Canyon, 

such as Little and Box canyons, on the north side of the river just 

above the mouth of Salmon River, and Blue Lakes alcove, about 6 miles 

below Shoshone Falls. As will be explained later, the remarkable side 

.alcoves, or short "blind" canyons opening into the main canyon, owe 

their existence to the great springs feeding the streams which flow 

from them. Another similar u spring alcove," but at first view not so 

clearly the result of springs undermining the cliffs, is furnished by the 

lower portion of the canj^on of Malade River.

The water of the springs between Shoshone Falls and Bliss has an 

essentially uniform temperature of about 60° F. throughout the year. 

The water is clear, but of a bluish color, due to fine particles in suspension. Several of these spring-fed streams are inhabited by trout. It 

is indeed a surprise to find beautiful trout streams in the central part 

of a flat, arid plain.
28 SNAKE EIVEE PLAINS OF IDAHO. [BULL. 190.

The temperature of the water pouring out of the walls of Snake 

River Canyon shows that it is not derived from deep fissure springs, 

and, in fact, has not made a deep descent into the earth. The water 

no doubt comes from the mountains lying north of the Snake River 

Plains, and is supplied mainly by the subterranean now of "Jost 

rivers."

Besides the springs in the canyons already referred to, there are a 

few fissure springs on the Snake River Plains, usually near the bordering mountains, which have a high temperature, but their combined volumes make but slight addition to the surface run-off. Possibly hot 

springs rise beneath the lava sheets flooring the plains and influence the 

temperature of the canyon springs, but there is no direct evidence that 

such is the case, although the temperature of the canyon springs shows 

some variation which can not be due to the depth of the sheets of rock 

from which they appear to issue.

The springs along Snake River and at a few localities near the mountains bordering the Snake River Plains have been utilized for irrigation.

WATER POWER.

The amount of water power available along Snake River in its passage across southern Idaho is practically unlimited, but as yet is not 

utilized. The most important falls and their height are as follows: 

Idaho Falls, 30 feet; American Falls, 50 feet;« Twin Falls, 180 feet« 

(PI. XXII); Shoshone Falls, 210 feet« (PL IV); Salmon Falls, about 

25 feet. Besides these there are many localities where "vertical 

leaps are made in many cases from 20 to 50 feet, all suggesting, in 

addition to the natural grandeur and sublimity of the surroundings, 

the wonderful possibilities through their utilization in the industrial 

development of the State." 6

Besides Snake River itself, the great volume of water at The Thousand Springs and at the mouth of Malade River could be easily and 

cheaply utilized. as sources of power. The future greatness of the 

State certainly depends largely on the proper development and use 

of this branch of her great resources.

IRRIGATION AND AGRICULTURE.

With the small mean annual precipitation on the Snake River Plains, 

practically all of it falling during the winter season, agriculture without irrigation is seemingly impossible. As previously suggested, however, over the higher portion of the plains lying southwest of Big 

Butte the rainfall may be sufficiently above the average, or the soil 

may retain enough moisture, or possibly the slow melting of the winter

a From biennial report of the State engineer of Idaho, 1899-1900, pp. 8, 9. 

*>0p. cit., p. 9.
U. 8. GEOLOGICAL. SURVEY .ULIETIN NO. 199 PL. IV

SHOSHONE FALLS, SNAKE RIVER, IDAHO.
BUSBELL.] IRRIGATION AND AGRICULTURE. 29

snow may furnish the proper conditions "to permit the growing of 

wheat and other cereals without irrigation. This experiment is at 

least worth trying.

As agriculture is at present entirely dependent on irrigation, cultivated land occurs only where water from streams and springs can be 

obtained. Not only is the presence of sufficient water a controlling 

factor, but the topography and the nature of the soil must also be taken 

into account. The portions of the Snake River Plains first brought 

under irrigation are those where the conditions are most favorable 

for small enterprises. These are the flood plains of the small streams 

from the mountains, and points where springs can be utilized. Later, 

came more extensive systems, involving the construction of extensive 

canals and necessitating the employment of a large amount of capital 

and labor. The small ditches were constructed by individuals, or by 

small groups of ranchers, and the canals by communities or incorporated companies. One result of the conditions met with is the isolation of many individual ranches and of small groups of ranches 

situated along a single stream. The construction of canals led to an 

increase in the size of the communities, and in some instances to the 

growth of considerable towns.

The widely separated individual ranches or small groups of ranches 

are situated mostly where the streams from the mountains emerge onto 

the plains, and frequently extenc as far up the mountain valleys as 

flood plains occur. In a similar way the springs in Snake River Canyon 

have in several instances been utilized, and single ranches or small 

groups of ranches forming a fringe along the river's banks, mostly on 

its northern side, occur from near Shoshone Falls westward.

The most important communities have grown up along irrigation 

canals. T}^pical illustrations of the results of a favorable combination 

of conditions in this connection occur near the junction of the North 

and South forks of Snake River, in the northeastern portion of the 

Snake River Plains, where the streams are upbuilding their channels 

and spreading out broad alluvial fans. The South Fork, before its 

waters were so largely diverted into canals, divided into several 

branches, the positions of which were liable to change during each 

high-water stage, and furnished unusual facilities for irrigation. In 

the region referred to, or in a general way, between St. Anthony and 

Idaho Falls, including lands on each side of Snake River in the vicinity 

of Market Lake and extending far up the South Fork, there are a 

large number of ranches on which grain and hay are successfully cultivated, as well as orchards and gardens. There are several flourishing villages in this section also, and evidence of prosperity and thrift 

are abundant. By no means all of the good land that can be irrigated 

is under cultivation, however, and still greater results can be confidently predicted.
30 SNAKE EIVER PLAINS OF IDAHO. [BULL. 199.

Although Snake River makes a sharp descent over lava at Idaho 

Falls, the stream a short distance below has again a low gradient and 

is upbuilding its channel. The gravel flood plain of the river and portions of former flood plains, now forming gravel terraces, are available 

for agriculture. Although to a considerable extent the soil is loose 

textured and requires much water to insure good crops, it is easily 

irrigated, and an abundance of water is available. Farms border the 

river on each side all the way to American Falls, where the canyon 

begins which extends to the Idaho-Oregon boundary. Projects have 

been matured looking toward the irrigation by means of canals, at 

higher levels than those now in use, of great areas of fine land extending from some distance above St. Anthony to the Salmon River." 

Lower down, where the river is upgrading its channel and forming a 

flood plain, and the large canals are needed for irrigating the surface 

of the broad plains bordering Snake River Canyon, the most favorable 

localities for diverting the waters are at places where the canyon walls 

are not high and rapids or falls occur. In the canj^on of Snake River 

in the vicinity of Hagerman the river makes a sharp turn to the 

south and west and then to the north, thus forming a conspicuous bend 

concave to the northeast. Here there is a precipice formed of soft 

clay and unconsolidated sand, about 600 feet high on its southern and 

western border, as is shown on PI. II. The land on the northeastern 

side of the river at this exception* ^ bend, about 10 square miles in 

area, slopes gently toward it, but is bordered to the northward by a 

lava rim rock, from beneath which issue large springs which are utilized for irrigation. In addition to the natural springs tunnels or horizontal wells have been excavated in the basal portion of a lava sheet 

where it forms a rim rock and abundant water has been obtained. A 

large part of the land in the Hagerman Bend is now under cultivation, 

and much more of it can be utilized. This isolated area, sloping to the 

sun and sheltered on all sides by canyon walls, is one of the most promising for agriculture in southern Idaho. Below Hagerman copious 

springs are of frequent occurrence on the right side of the river as far 

as Bliss, a distance of about 8 miles, and a narrow strip of land in the 

canyon's bottom is under irrigation. All of the land now under cultivation from Shoshone Falls to Bliss, embracing by estimate about 

8,000 acres, is watered from springs. This is the most conspicuous 

example of the use of spring water for irrigation to be found in Idaho.

A flourishing farming community exists on the borders of Bruneau 

River, near its mouth, where the stream has broadened its valley in 

soft beds. The Bruneau, near its mouth, cuts one of the lower sheets 

of basalt, which extends farther south than the surface sheets forming

«Maps showing the lands which can be irrigated at a reasonable expense along the Snake in the 

portion of its course which crosses Idaho have been published by the State engineer of Idaho. See 

Biennial Report of the State Engineer, 1899-1900, Boise (1901).
RUSSELL.] IRRIGATION AND AGRICULTURE. 31

the plains on the north side of Snake River, and for a few miles flows 

through a narrow, steep-sided canyon. The fact that Bruneau Valley 

is comparatively wide above the narrow canyon in basalt through 

which it enters Snake River is due to the check in downcutting 

afforded by the basalt, which permitted the stream above the obstruction to meander and broaden its valley. In this broader portion farm 

lands form a belt averaging about a mile wide and about 9 miles 

long. Water for irrigation is, for the most part, derived from the 

river by means of canals, but warm springs, and to a small extent 

artesian wells, are also utilized.

The variations in geological conditions and in topographical development which favor the utilization of streams for irrigation are again 

illustrated along the lower portion of Boise River. This river, on 

leaving its narrow and rather high-grade canyon in the mountains and 

entering the comparatively wide valley it has excavated in the soft 

rocks of the plain, where its gradient is low, is unable to bear along 

the cobbles, gravel, sand, and other material brought from above and 

has spread out a wide flood plain bordered by terraces, through which 

it flows with many curves and frequently divides and reunites so as to 

inclose islands. These conditions have favored the construction of 

irrigating ditches and high-level canals, and a large area has been 

brought under cultivation. From the hills near Boise, a thousand feet 

in height, one may look down on that beautiful city embowered in 

trees, and toward the west, as far as the eye can reach, behold green 

fields and orchards surrounding comfortable farm houses. Owing to 

the abundance of water available for irrigation, as well as the favorable 

soil conditions, this region has become the most extensive of the highly 

fruitful areas of Idaho.

The most valuable crop cultivated on the Snake River Plains, where 

water is now available for irrigation, is hay, principally alfalfa. 

Cereals, including maize, are also grown, but in minor quantities. 

Orchards and vineyards thrive and yield abundant returns, especially 

along Snake River below Shoshone Falls, and in Bruneau Valley, 

where shelter is afforded by the neighboring canj^on walls. Owing to 

the isolation of the orchards in many instances, the injuries caused by 

insects are much less severe than in more generally cultivated regions. 

The greatest obstacle that fruit raisers have to contend with is the late 

frosts in spring or early summer.

STOCK RAISING.

The greatest of the industries as. yet established on the Snake River 

Plains is stock raising. To this a large part of the cultivation of the 

soil, the raising of grass, is incidental. In the counties of Idaho which 

include within their borders portions of the Snake River Plains there
32 SNAKE EIVEE PLAINS OF IDAHO. [BULL. 199.

are over 1,000,000 sheep, nearly 200,000 cattle, and about 34,000 

horses. a But little of this stock is fed in barns during the winter and 

by far the greater part is fed hay only during severe storms. The 

winter pastures.are on the broad sagebrush-covered plains.

MINING.

The Snake River Plains themselves are destitute of metal and ores 

of economic importance, but the bordering mountains contain rich 

mines. Along Snake River fine placer gold occurs in considerable 

quantity, but is difficult to procure. Placer mining has been carried 

on, in a small way, continuously for many years, however, and the 

annual production of gold is a considerable addition to the wealth of 

the State. A large portion of the mining -that has been done is a loss 

to the State, however, as rich agricultural lands which could be made 

to yield harvests for an indefinite time are ruined by the operation. 

The single crop of gold obtained is far less in value than the many 

crops of hay, grain, fruit, etc., which could be secured if the land 

were tilled.

TOWNS.

The wants of the people engaged in stock raising, ranching, and 

agriculture on the Snake River Plains or amid the bordering mountains has led to the springing up of several small towns. These towns 

were first established at localities where water could be easily obtained for irrigation, and later received a new impetus when railroads 

were built, which increased their importance as shipping centers. In 

addition to the needs of agriculture and stock raising, the mining 

interests have also exerted an influence on the growth of certain towns 

and villages of the plains.

The population, in 1900, of principal towns situated in the portion of Idaho to which attention is here invited is as follows: 6 Boise, 

5,557; Pocatello, 4,046; Idaho Falls, 1,262; Mountain Home, 529; St. 

Anthony, 411.

Boise is the capital of the State, and the center of a large stockraising, agricultural, and mining region. Pocatello, the second city 

of the State in number of population, owes its growth principally to 

the fact that it is an important railroad center. "Besides the cities and 

towns named there are many boroughs or villages, numbering from a 

very few to perhaps a score of houses. The largest of these unincorporated villages is Blackfoot, which has about 1,500 inhabitants. On 

maps of Idaho many names of post-offices appear which a person not 

familiar with the State might assume to be settlements of some importance, but which in a large number of instances are simply post-offices 

housed in some isolated farm-house or cross-roads store.

a First Ann. Kept. State Bureau of Immigration, Labor, and Statistics. Boise, 1900, 

6Twelfth Census of the United States, Bull. No. 8.
RUSSELL.] KAILKOADS AND HIGHWAYS. 33

The total population .of Idaho in 1900 was 161,772, or 1.9 to the 

square mile. In the region embraced in the Snake River Plains the 

people are, to a great extent, segregated in communities where water 

can be had for irrigation, leaving vast tracts entirely uninhabited. 

The counties which include portions of the plains Avithin their border, 

however, contain more than half of the population of the State and 

represent about one-half its area. The leading topographic feature of 

southern Idaho is the great plains, and of its central and northern 

parts, rugged mountains. The influence on the density of population 

of barren, uninhabitable plains, encroached upon by agriculture and 

stock growing, and of mountains where mining industries have been 

established, is thus seen to be about the same.

RAILROADS.

As is indicated on the map forming PL I, the Snake River Plains 

are traversed throughout their entire length by the Oregon Short Line 

Railroad. One division of this road, starting from Pocatello, leads 

westward, and traverses the plains all the way to the Idaho-Oregon 

boundary, with one branch leading northward to the mining regions 

about Hailey and another terminating at Boise. A branch about 50 

miles long leads southward, crossing Snake River to Murphy. Another 

division of the road, starting also from Pocatello, leads northward and 

traverses the northeastern border of the plains to the Idaho-Montana 

boundary. An important branch of this northern division, built in 

1901, begins at Blackfoot and crosses the widest part of the plains, 

passing between Big and Middle buttes and reaching the region drained 

by Big Lost River.. The aggregate length of- the railroads now in 

operation across the Snake River Plains is about 500 miles. Travelers 

over these two divisions and various branches of the "0. S. L.," as it 

is familiarly termed, will be enabled to see nearly all the variations that 

the plains present and to obtain an idea of their vast extent. To 

travelers who make such a journey, the most pronounced need of the 

country namely, water will become painfully apparent.

HIGHWAYS.

Owing to the flatness of the Snake River Plains and the fact that the 

lava rocks when present are generally covered with at least a few feet 

of fine soil, traveling is easy in all directions, except where canyons 

break the surface. Roads lead across the plains in various directions, 

and all parts of them can be reached by wagons. The exceptions in 

this connection are the fresh lava flows, sometimes hundreds of square 

miles in area, and the portions of the canyons bounded by precipitous 

walls. In several instances, however, good roads, or "grades," as thej7" 

are termed, have been constructed which lead into the canyons where

Bull. 199 02- 3
34 SNAKE EIVEE PLAINS OF IDAHO. [BULL. 199.

the walls seem to be almost vertical precipices. The main difficulty 

in crossing the plains is the scarcity of water. As in most flat regions 

where stock raising is a leading industry riding is largely practiced.

BIG, MIDDLE, AND EAST BUTTES.

An account of the Snake River Plains, however brief, would not be 

complete unless it directed special attention to three conspicuous mountain-like elevations that break their monotony. These elevations, known 

in their order from southwest to northeast as Big, Middle, and East 

buttes, are situated in the central part of the vast lava-covered region 

of southeastern Idaho, about 25 miles northwest of Blackfoot. Their 

location is indicated on the map forming PL I. Owing to the apparently perfect flatness of the surrounding plain they are prominent 

objects in the, landscape when seen from distances of 100 or more miles, 

and are no doubt familiar to many persons who have passed over 

either of the two divisions of the Oregon Short Line Railroad which 

diverge at Pocatello, one going northward and the other westward. 

Owing to the isolation of the buttes and the absence of water in summer anywhere in their vicinity, with the exception of a small spring at 

the northeast base of Big Butte, they are seldom visited. For these 

and other reasons it seems appropriate to close this introductory chapter with an account of these three most interesting and instructive 

elevations.

Two of the buttes, namely, Big and East buttes, are rhyolitic volcanic cones of ancient date, which are completely surrounded by Snake 

River lava and furnish admirable examples of steptoes, as such islands 

in a once molten sea of lava have been termed. Middle Butte differs 

from its companions, being an upraised block of stratified basalt.

The elevation Of Big Butte above the surrounding plain, as determined by aneroid measurements, is 2,350 feet, and by estimate the 

height of Middle Butte is 400 and that of East Butte about 700 feet. 

Big Butte, as may be judged from PI. V, rises as a deepty sculptured 

mountain precipitously from the nearly flat plain surrounding its 

base, and terminates in two ridges about a mile apart, with a deeper 

depression between, which is apparently a remnant of a crater. At its 

base the mountain is 5 or 6 miles in diameter, and is somewhat elongated in a northwest-southeast direction. To reach its summit, no 

matter how carefully the trip may be planned, true mountain climbing 

is necessary, and the steepness of the slopes will be forcibly impressed 

on the climber's mind before he reaches the top. From whatever 

direction the mountain is ascended the abruptness with which it rises 

from the plain, without gradual approaches or foothills, becomes 

impressive. In the gulches and deeply cut ravines there are alluvial 

fans which extend out onto the surrounding plain for 2 or 3 miles,
U. S. GEOLOGICAL SURVEY BULLETIN NO, 199 PL. V

A. EAST BUTTE, IDAHO, AN OLD RHYOLITIC VOLCANO SURROUNDED BY BASALT.

Ji. o,va tSOl i E, , UArlO, AW OLD RHYOLITIC VOLCANO SURROUNDED BY BASALT.
RUSSELL.] BIG, MIDDLE, AKD EAST BUTTES. . 35

expanding and becoming indefinite at their lower extremities and 

clearly indicating the amount of erosion that has occurred since the 

encircling basalt was poured out. Equally apparent is the fact that 

the mountain was deeply seamed b}r erosion before the basalt flowed 

about it. The land surface on which the old volcano was built and 

the streams of acid lava which it may have sent out are buried from, 

sight by the basalt, and no inequalities of the present surface suggest 

hills or hollows beneath the deep covering of black lava. These contrasts in topography coincide with even more sharply denned differences in the rocks. The mountain is composed mainly of nearly white 

rhyolitic lava, which presents many variations from compact, banded, 

and spherulitic layers to light pumice and black glass or obsidian. 

The encircling basalt is black, with but a single neighboring area at 

the north base of the white butte, where a remnant of a small basaltic 

cinder cone reveals a uash of dark red. The ancient steptoe is built 

of highly acid lava and the surrounding plain is composed of basic 

lava.

An exception to the statement that there are no exposures of the 

land surface on which the ancient rhyolitic mountain was built may 

perhaps occur about 5 miles to the east of its base, where a group 

of hills, clothed in part with juniper trees, rise to a height of about 

300 feet above the recent basalt that intervenes between the two. An 

examination of this group of hills was cut short hy the coming of 

darkness, but the occurrence of obsidian and pumice in what seemed 

to be a remnant of a lapilli cone suggested that a small volcano, similar 

to the greater one which formed Big Butte, may there be represented.

Big Butte, like the surrounding plain, is grass covered, and the 

numerous deer trails, on which the imprint of the foot of a wolf or a 

wildcat may occasionally be noticed, show that it is a favorite feeding 

ground for big game. Elk resort there in winter and bears are common visitors. An arrow point, of obsidian, picked up on the summit 

of the mountain, suggested that this was formerly an Indian hunting 

ground. Just before my visit it had rained, and on the plain about 

3 miles to the south of the butte there was a small water pocket from 

which trails radiate in various directions, showing that year after year 

the same depression had been occupied by water and for a long time 

had been resorted to by wild animals. Besides grasses and flowers, 

the mountain is covered in certain favored places on its northern slopes 

with a young and thrifty growth of pines, firs, and juniper, and much 

of the si dniit portion is occupied b}^ a dead forest of coniferous trees, 

many of them 30 to 40 feet high, which were killed by fire about eight 

or ten years ago. Over the greater porti8n of the burnt area, which 

includes nearty the entire mountain, no young trees have sprouted. 

There is so little moisture that the forest will never be renewed. It
3.6 SNAKE EIVEE PLAINS OF IDAHO. [BULL. 199.

is only in the ravines on the northern slope, where snow accumulates 

most deeply and remains longest, that conditions are favorable to the 

growth of young trees. The vegetation, if studied critically, would 

evidently furnish a delicate index to the climatic conditions.

On reaching the summit ofc Big Butte on a clear daj^ there is a farreaching view in all directions, and much of the history of the Snake 

River Plains may be easily read in the splendid panorama.

In attempting to understand the features of a landscape when beheld 

from an elevated station, it is necessary to have in mind the scale on 

which the relief map, for such it appears, which is spread before one, 

is constructed. In arid regions, in spite of the haze usually present, 

distances are deceptive. Objects leagues distant seem only miles away.

The mountains to the east are fully 50 miles distant, and the nearest 

peaks to the west are from 30 to 40 miles away; to the southwest and 

northeast the flat plain extends indefinitely, and' no bordering shore is 

in sight. In spite of their remoteness, the Lost River Mountains to 

the west are clearly and even sharply denned. The upward sweep of 

alluvial fans can be easily traced to where they narrow at the mouths 

of strongly cut gorges. Above their summits are the outlines of bare 

crags, where angular rocks form bold convex curves, which replace 

the concave curves due to stream deposition on the lower slopes. 

Still higher is a dark band of forest which encircles the mountain like 

a shadowy wreath. Far above the timber line are bare serrate peaks, 

all of them light gray and suggesting the presence of limestone or 

quartzite, except the highest pinnacles of all, which gleam silver white. 

A recent storm, which brought light showers to the plains, covered the 

higher mountains with snow. Roads on the plain appear as fine lines 

radiating from the spring at the northern base of the mountain. Each

curve in the yellow line leading west can be clearly followed to Arco,

24 miles distant, where clumps of bushes and a few houses tell of the 

presence of water. Other clumps of bushes and here and there a field 

of alfalfa, a rectangular patch of green on the vast gray expanse, 

reveal the curves of Big Lost River as it flows through the plain, 

bends northward, and in winter maintains its existence for about 50 

miles to where it spreads out in a small lake. To the northeast, and 

seemingly close at hand, although 15 and 20 miles distant, Middle and 

East buttes rise abruptly. The nearer butte is black, its sloping 

surface is inclined to the southeast, in conformity with the dip of the 

hard rock layers of which it is composed. The western border is 

abrupt at the summit, but below it has much more gently inclined 

lines, due to talus slopes. East Butte is white, rises sharply on all 

sides, is without conspicuous talus slopes, and terminates above in two 

sharp, angular peaks, between which there is a smooth, saddle-shaped 

depression, suggestive of a broken crater. A view of this remarkable 

steptoe, taken from near Middle Butte, is presented in PL V.
RUSSELL.] BIG, MIDDLE, AND EAST BUTTES. 37

Still farther to the northeast, and, as one is surprised to learn on 

referring1 to a map, 46 miles away, the outlines of Market Lake craters 

are clearly visible. Their characteristic conical forms, with flat summits, leave no doubt that they are extinct volcanoes. From personal 

examination I know they are tuff cones with craters in their tops. 

When the eye has become adjusted to the novel conditions it perceives that the vast plain is not absolutely flat and featureless, and as 

evening approaches and a strong side light causes even small elevations to cast shadows, many cone-shaped prominences rise from the 

previously flat surface. That these are extinct volcanoes is clearly 

shown by an example, only 3 or 4 miles distant to the southeast, from 

which a black stream of lava with a bare, rough surface, evidently of 

recent date, extends northward, and expands into a belt a mile or 

more wide before terminating. This recent addition to the rocks of 

the plain resembles a great withered and blackened leaf, with its petiole 

still attached, laid on the flat surface. Another black lava stream, 

starting from an elevation a few miles to the eastward, also flowed 

northward and expanded into a leaf-like form several square miles in 

area. These two recent lava streams indicate that the plain of which 

they form a part has not been produced by a single vast outpouring of 

molten rock, but is in reality highly compound and consists of many 

widely expanded and overlapping lava sheets. A small elevation, the 

summit of a low cone with an immensely expanded base, occurs about 

8 miles to the south. It is similar to those from which lava was 

recently poured out, but is much older. The lava has evidently flowed 

away from a small opening in all directions so as to form a cone, with 

a diameter at the base of certainly 8, and probably as much as 10 miles. 

When this old volcano is seen in profile from the surface of the 

surrounding plain it presents the appearance of another similar cone, 

shown on PL XVIII, about 15 miles to the west of Big Butte. The 

cone just referred to, together with two companions, is also in sight 

from the summit of Big Butte, and still others of similar shape, all 

broad, low cones, usually with flat summits, may likewise be distinguished. Most of the small volcanoes are situated south of an eastwest line drawn through Big Butte, but to the northeast there is 

one prominent brown crag only a short distance north of the wagon 

road leading to Blackfoot. Still farther north, and beyond the 

. straight line formed by the railroad now in process of construction, 

are two other low mounds, which from near inspection I found to be 

remnants of basaltic craters. Far to the south, and nearly lost in the 

dim distance, are still other elevations, which have the same topographic forms as those nearer to hand, and which I believe are also 

old craters, although as yet unvisited and undescribed. To the west, 

close to the far more prominent mountains, j^ellow with withered 

grass, are the Cinder Buttes, among which a score or more volcanic
38 SNAKE BIVEE PLAINS OF IDAHO. [BULL. 199.

cones are known to exist. Not including the Cinder Butte, or East 

Butte, about twenty craters can be counted on the broad plain, and still 

others occur which can not be readily recognized from a distance. 

Evidently a very large portion of the lava occurring as a surface 

covering on the Snake River Plains came from small and inconspicuous 

craters, many of which have escaped burial b}7 later eruptions and 

still exist as elevations.

After climbing Big Butte I rode across the plain, in part occupied 

by recent lava, but mostW a grass and sagebrush covered region, to 

Middle and East buttes, but owing to lack of time did not climb either 

of them. Middle Butte, as already stated, is composed of stratified 

basalt, and does not} present evidence of being a cinder or lava cone, 

and does not mark a site from which cither scoria or liquid lava was 

extruded. About in a line betAveen Middle and East buttes, however, 

and overgrown with juniper trees, is a low elevation of scoriaceous 

lava, which appears to be a remnant of a basaltic crater.

East Butte has preserved its original shape much more completely 

than Big Butte, probably for the reason that it presents much less 

surface on which water might collect into streams, and also because 

of its less height. It rises precipitously from the surrounding basalt 

on all sides (PI. V, A) and is free from conspicuous talus slopes and 

alluvial fans. The rock is a white rhyolite, and what is clearly a 

remnant of a crater still exists at the summit.

Middle and East buttes are covered with an open forest of small 

juniper trees, which extends far over the plain to the east. To the 

west of them there is a broad, rolling prairie. No water is to be had 

except in winter, when an occasional depression may perhaps be filled 

by the melting snow. Except for the absence of water, the region is 

as fair and inviting1 as the most favored 'portions of the prairie States.

The chief lesson learned by a visit to the "Three Buttes" is that 

two of them are ancient rhyolitic volcanoes, entirely surrounded by 

the Snake River lava; and that on the encompassing plain there are 

many extinct volcanoes which poured out basaltic lava.

GENERAL GEOLOGY.

Previous investigations. Southern Idaho is to'a great extent an 

untrodden field to geologists. The most detailed survey that has been 

made within its extensive area embraces a region of about 864 square 

miles in the vicinity of Boise, which has been described and mapped 

by Waldemar Lindgren in what is known as the Boise folio, published 

by the U. S. Geological Survey." This folio furnishes an admirable 

beginning for the stiuty of the geology of the region surrounding the

a This folio measures 18£ by 21 J- inches, contains 7 pages of descriptive text, 4 full-page maps, sections, etc., and is sold by the Survey for 25 cents per copy.
RUSSELL.] PBE-TEKTIABY FORMATIONS. 39

9

area of which it treats, and should be carefully studied not only by 

professional geologists, but more particularly by the people of Idaho.

A considerable portion of the Snake River Plains lying south of the 

area embraced in the Boise folio has also been explored by Lindgren 

in connection with detailed studies of neighboring mining ^districts, 

and the results have been presented by him in a paper published by 

the United States Geological Survey." In this paper there is a summary of the observations made by other geologists who have visited 

southern Idaho.

From the reports just mentioned, as well as my own explorations, 

it is evident that the geological discussion of the Snake River Plains 

may be consistently divided into two portions, the first dealing with 

the older rocks which were upraised into mountains and deeply eroded 

before the partial filling ~of the Snake River Basin, and the second

with the lacustral and stream deposits, lava sheets, etc., now forming 

the plains themselves. The former, in geological language, embraces 

mostly if not entirely, Paleozoic rocks; and the second, Tertiary and 

Recent rocks. Between the formation of these two great rock divisions, there was a long interval, during which deep erosion and the 

development of a rugged topography took place.

PRE-TERTIARY FORMATIONS.

The rocks of which the mountains surrounding the Snake River 

Plains are most largely composed are granite, rhyolite, quartzite, and 

limestone.

GRANITE.

The terrane named the "Boise granite" by Lindgren, from which 

the rugged mountains which lie to the north and east of Boise have 

been sculptured, extends eastward from this area and occupies an extensive and exceedingly rugged region lying north of Mountain Home. 

The eastern border of this area forms a moderately irregular line with 

an approximately north-south direction, situated between the canyons 

of Ditto and Syrup creeks. On this dividing ridge the granite passes 

beneath extensive surface flows of rhyolitic lava which form the mountains drained principally by Syrup and Long Tom creeks, as well as 

Mount Bennett, and other high land still farther east. The junction 

of the granite and rhyolite is sharply defined and is easily traced, 

owing, principally, to the light color of the'granite and the dark 

browns, purples, and reds of the later-formed terranes. The granite 

is massive, without bedding planes, while the rhyolite is in distinct 

layers, which are sharply tilted. Near the "Overland road," which 

skirts the base of the mountains lying northwest of Mountain Home,

a Eighteenth Ann. Kept. U. S. Geol. Survey, Pt. Ill, pp. 617-719. This report is accompanied by a 

geological map of a portion of the western part of the Snake River Plains.
40 SNAKE KIVEE PLAINS OF IDAHO. [BULL. 199.

and at a distance of 3 to 4 miles west of Canyon Creek, small exposures 

of granite occur on the border of the lava forming the plain. Rising 

steeply from these isolated outcrops, which are significant in reference 

to the relative age of the two classes of rock forming the mountains, 

are bold ^precipices of dark rhyolite. Significant, too, in respect to 

the geological structure of the region and the relation the plains bear 

to the mountains, is the fact that the precipitous escarpment bordering 

the plain on the northeast, between Mount Bennett and Boise, is composed to the eastAvard of rhyolite and to the westward of granite, but 

the alignment is unbroken at the junction of the two formations. 

The major features of this great escarpment, about 50 miles in length, 

are due to faulting or to the uplifting of the mountains along a line of 

fracture.

The Boise granite, as has been stated by Lindgren, is intrusive and 

of ancient date (perhaps pre-Algonkian) that is, the great granitic 

area referred to, embracing several hundred square miles, is composed 

of rocks which were forced upward in a molten condition from deep 

within the earth's crust, but, so far as known, failed to reach the surface so as to produce volcanic eruptions. The rising magma uplifted 

the rocks beneath which it was intruded, probabty into the form of a 

dome, which has since been removed by erosive agencies, and, cooling 

slowly under great pressure, produced a massive, coarsely crystalline 

rock. Not only has the thick cover beneath which the granitic magma 

was intruded been worn awa}r , but streams have cut deeply into the 

intrusive rock itself, and probably many hundreds of feet of its upper 

portion have been removed. This process of denudation is still going 

on, as is shown by the soft, broken, and deeply decayed conditions of 

the portion of the granite now exposed, arid by the nearly universal 

mantle of fragments that covers its surface and extends far clown the 

channels of the draining streams. Owing principally to the decay of 

its constituent crystals, mica and feldspar, the granite is usually 

altered to a depth of 100 feet or more below the surface, and exposures of fresh rock, compact enough to be used in finished masonry, are 

not to be seen. Decay, disintegration and erosion have given to the 

granitic area an exceedingly rugged surface, the.major features of 

which are deep, generally smooth-sided valleys and bold, rounded 

hills. One characteristic is the frequent presence of great numbers of 

crags and castle-like forms of bare rock which project through the 

nearly universal covering of surface debris.

The stream channels in the granite, and far down their courses after 

reaching the Snake River Plains, are deeply filled with rock Avaste. 

The disintegration of the rocks is evidently progressing rapidly and 

furnishing more fragments, mostly of the nature of coarse, angular 

sand and gravel, than the streams are able to cariy away. In many 

depressions, and even in valleys of considerable size, the accumulation
BUSSKU,] PRE-TERTIAEY FORMATIONS. 41

of rock fragments has become so deep that rain water is not retained 

at the surface, and no stream channels are in sight. The concave surfaces of these partially filled depressions meet the convex curve of the 

bordering uplands, and where the mantle of rock waste is not broken 

by residual crags the landscape has broadly undulating outlines.

Traversing the Boise granite in the region to the north of Boise, 

and described by Lindgren, there are numerous dikes of both acid and 

basic rock which form long narrow outcrops, differing from the inclosing granite. As is well known, they are due to the filling of fissures 

with molten material injected from below and to the hardening and 

crystallizing of the intruded magma on cooling. To the east of the 

portion of the granitic area included in the "Boise folio dikes are 

less common, although several conspicuous examples occur in the 

mountains drained by Slater, Ditto, and Indian creeks. These dikes

are composed of purplish rhyolite, trend nearly due north and south, 

and have a width of from 30 to 80 feet or more. The dikes are vertical, and owing to the greater resistance they offer to erosion, stand 

in bold relief above the surface of the inclosing granite. The most 

characteristic examples thus far examined occur in the mountains 

adjacent to the border of the Snake River Plains, between Black and 

Slater creeks; others, but less numerous and less bold and conspicuous, 

were seen in the mountains between Indian and Ditto creeks. The 

rock forming these dikes is of the same general character as the 

rhyolite occurring in well-defined sheets in the mountains to the 

northeast of Mountain Home and in Mount Bennett, etc.,'and suggests 

that much of the granite now7 exposed was formerly covered with 

rhyolitic flows, which have been eroded away. The rhyolite is 37 ounger 

than the granite, and an epoch of erosion intervened between the 

formation of the two terranes.

An outcrop of granite about 5 or 6 square miles in area occurs on the 

west side of the Snake River Plains, about 75 miles west of Blackfoot, 

and near the Cinder Buttes. This small'isolated area is surrounded 

by quartzite on all sides except the eastern, where it is bordered by 

a recent flow of lava which came from the Cinjier Buttes. The contact of the granite with the surrounding quartzite is sharply defined, 

and at one locality on its southern margin a mining shaft has been 

sunken to a depth of 80 feet, following the plane of contact, which is 

inclined southward at an angle of about 80°. The bedding planes in 

the quartzite also dip southward, but at an angle of only 15° to 18°. 

There is no evidence of an alteration of the quartzite at its junction 

with the granite, and the contact is evidently a result of faulting. 

The diverse dips observable in. neighboring quartzite ridges show 

that much movement has occurred along fault planes in the hills about 

the granite, and it seems evident that the granite itself has been elevated by this process high enough to be exposed by erosion. The
42 SNAKE KIVEE PLAINS OF IDAHO. [BULL. 199.

granite is light-colored, coarse-grained, and resembles the Boise 

granite, but there is no evidence of a connection between the two. It 

it possible, however, that the}'' are of the same age, and perhaps portions of a single intrusion.

As stated by Lindgren in the Boise folio, granite is present in the 

Owyhee Mountains, in southwestern Idaho to the south of Snake 

River, but little is known of that region. No other granitic areas are 

reported to occur in the part of Idaho here considered, but it is to be 

remembered that large portions of that region have never been visited 

by geologists, and even the general nature of many of the mountain 

ranges is unknown. Certain bold peaks to the south of Snake River, 

to the east of Albion, rise well above timber line, and when seen from 

a distance present the appearance of weathered granite, but were not 

visited by me.

EHYOLITE.

The extensive area of rhyolite whose western border, as stated 

above, is on the divide between Ditto and Syrup creeks, extends southeastward to the vicinity of King Hill Creek, a distance of about 30 

miles. The width of the area is 6 or 8 miles, but its full extent to the 

northward is unknown. It forms Mount Bennett, which rises 5,000 

feet above the adjacent portion of the Snake River Plains, as well as the 

rugged country drained by Syrup and Long Tom creeks, lying north 

of Mountain Home. On the south it is bordered by the Snake River 

lava, and on the north, at the head of Long Tom Creek, by a quartzite 

ridge which slopes steeply on its northern side to the South Fork of 

Boise River, where granitic outcrops occur.

The rocks in this extensive area are stratified and present two welldefined varieties, one a compact, light-purplish rock with a granular 

structure and conspicuous crystals of feldspar, and the other a black, 

vitreous rock which also contains large feldspar crystals. In each 

variety there is frequently present a pronounced flow structure, which is 

especially well shown on weathered surfaces. This structure was produced by the flow of the still plastic magma after crystals had formed 

in it. In many instances parallel laminae were produced in this manner, 

which are a small fraction of an inch thick, but may be traced laterally 

for several feet. An alternation of beds of granular rocks with a dull 

fracture and of black, vitreous layers gives the formation a distinctly 

bedded structure. Some of the light purplish beds, particularly near 

the base of the formation, on the divide between Dry and Syrup 

creeks, are of the nature of a tuff that is, they consist of consolidated 

dust-like fragments, but contain distinct crystals of feldspar. This formation, which may be termed provisionally the Mount Bennett rhyolite, 

is tilted in various ways, but usually dips toward the northeast. From
PBE-TERTIABY POBMATIONS. 43

commanding summits it is easily seen that the tilting is due to movements of large blocks, bounded by faults. The larger features in 

the relief are produced by fault scarps, but great erosion has also 

occurred. The faults have a general southeast-northwest trend, but 

while nearly parallel in several instances they frequently branch and 

diverge at low angles from the main belt of displacement which 

determines the bold southwest border of the mountains, overlooking 

the Snake River Plains. The precipitous southwest escarpment of 

Mount Bennett is a fault scarp, from which a step-like recession of 

cliffs has occurred and on which there are prominent talus slopes. 

The leading features of the structure, as well as of the relief of 

the Mount Bennett rhyolite area, as is also the case on a yet larger 

scale in the Lost River country, are due to normal faults. The.mountains are of the Great Basin type, but instead of trending northeast

and southwest, as is the case in much of Utah and Nevada, they have 

a direction about at right angles to that course.

Rocks similar to those forming Mount Bennett and the dark brown 

and purple mountains north of Mountain Home occur also in Snake 

River Canyon at Shoshone Falls. Beginning on the west, in the 

bottom of Snake River Canyon near the mouth of the lateral alcove 

leading to the Blue Lakes, this rock is exposed almost continuously 

on each side ot: the river up to Shoshone Falls and for a short way 

above, a total distance of about 7 miles. The surface of the formation is irregular. In places horizontally bedded basalt rests directly 

on the terrane referred to, but usually there intervenes a sheet of 

coarse unconsolidated breccia, made up of angular fragments, frequently 6 to 8 feet in diameter, of the lower formation, loosely united 

by an earthy connecting material. The thickness of this irregular 

sheet of angular fragments varies, but in some instances is fully 70 

feet. The breccia is not stratified and does not present other evidence 

of the action of water, but is overlain in places by well-stratified layers of sandy material from a few inches to 20 or 30 feet thick, which 

usually has the color and texture of a red brick, especially at its upper 

surface. The color is due to the heat of the overlying basalt. This 

sheet of moderately metamorphosed sedimentary material, possibly 

in part composed of volcanic dust and lapilli, is well exposed in the 

sides of the canyon below the falls, and can be easily traced for a distance of at least a mile. Other similar layers, from a few inches to 5 

or 6 feet thick in the central part, but thinning toward each end of the 

exposed portion, and having a length of a few hundred feet, are to be 

seen at several localities, interbedded with the basalt forming the walls 

of the main canyon and of the Blue Lakes alcove.

The rock exposed in Snake River Canyon and forming the precipice 

over which the river plunges at Shoshone Falls, as well as the fragmental material resting on it, exhibits both the massive, granular,
44 SNAKE BlVEft PLAINS OF IDAHO. [BULL. 199..

purplish variety and the glossy, black variety, each porphyritic, 

observed in the Mount Bennett rhyolite. Both varieties also show 

well-defined flow structure. My observation shows that the Mount 

Bennett rhyolite and the rock forming the lower portions of the cliffs 

at Shoshone Falls are essential^ identical, but no critical examination 

of the rocks of either terrane has been made. In the reports of the 

Fortieth Parallel Survey n the rock beneath the basalt at Shoshone 

Falls is termed trachyte, and no mention is made of the conspicuous 

layer of coarse breccia between the older massive igneous rock at the 

base and the basalt which forms the upper portion of the cliffs.

In the hills drained in part by Kock Creek, and situated between 

12 and 20 miles south of Shoshone Falls, rocks of the same general 

character as those forming the mountains to the northeast of Mountain Home, and similar also to the lower terrane at Shoshone Falls, 

again appear at the surface and form an extensive range of hills or 

low mountains. These hills, judging from their form, color, etc., 

when seen from a distance, are formed of the same kind of rock, prob-' 

ably throughout an area of between 150 or 200 square miles, but 

were not examined by me except for a distance of about 8 miles along 

Rock Creek to the south of Rock Creek post-office. In the Rock Creek 

Hills, as on the mountains to the northeast of Mountain Home, the 

rhyolite is in well-defined layers, and exhibits diverse dips ranging 

from 10° to 20° in adjacent ridges.

On Rock Creek two flowing wells have been obtained, and will be 

described more fully in the second part of this report, and springs are 

numerous. These wells and springs indicate that the rocks are composed of alternating layers of pervious and impervious material, and 

that when penetrated by the drill or broken by faults, water may rise

to the surface. There are reasons, however, for the suggestion that, 

the sheet of rhyolite forming the surface portion of the Rock Creek 

Hills is comparatively thin and rests on Tertiary sedimentary beds. 

Should this surmise be sustained by future studies, the hope of obtaining flowing water over a wide extent of country to the south of Shoshone Falls will be greatty enhanced. Springs are also numerous in 

the mountains composed of rhyolite to the northeast of Mountain 

Home, and the success attending the drilling of wells in the similar 

formation on Rock Creek suggests that favorable artesian conditions 

exist there also. Success in drilling artesian wells in a region of volcanic rocks like that drained by Rock Creek is unusual and inspires 

a hope that much of the country underlain by stratified rhyolite will 

be found to be water bearing.

Two of the three prominent buttes described on a previous page, 

situated in the central part of the Snake River Plains about 25 miles

a Vol. I, pp. 592-593.
RUSSELL.] PRE-TEETIAEY FORMATIONS. 45

northwest of Blackfoot, namely Big and East buttes, are composed of 

rhyolite, and are the weathered remnants of ancient volcanic cones. 

The rock of which each of these buttes is composed, as shown by field 

examinations simply, is mainly a very light-colored rhyolite, which is 

frequently highly vesicular, and at times becomes a true pumice. On 

Big Butte fragments of pumice and also of black obsidian occur, and 

the rock is in places spherulitic.

QUAKTZITE.

As is well known, the rocks designated by this name have resulted 

from the consolidation of sandstone, owing mainly to the deposition 

of silica from solution in water, between the grains. When this process has been associated with a high temperature, or by movements 

which produce a shearing of the material under great pressure, a 

foliated rock, usually containing mica, is° produced, which is termed 

quartz-schist.

Quartzite which in part had the characteristic of quartz-mlca-schist 

has already been referred to as occurring in the hills at the head of 

Long Tom Creek, overlooking the South Fork of Boise River. The 

only portion of this formation examined is situated in the northeastern 

portion of the Mountain Home quadrangle. It extends westward 

from its eastern border for a distance of 6 miles, forming a range of 

conspicuous peaks with rounded summits. These peaks with curved 

saddles between are thickly sheathed with fragments of their own rock. 

Their northeastern slopes descend precipitously to the South Fork of 

Boise River, but near the river granite outcrops. It is probable, 

judging from the topography, that the quartzite occurs to the north 

of the river and has a wide development in the rugged mountains in 

that region.

The bold mountains bordering the Snake River Plains on the northwest, between Big Wood and Little Lost rivers, are composed largely 

of quartzite. Indeed, so far as can be judged from the observations 

made by me in that region these mountains, with the exception of the 

small area of granite near the Cinder Buttes and certain limestone 

outcrops on Lava Creek near Martin, seem to be composed entirely of 

light-colored quartzite, which extends far to the northwest toward 

the Sawtooth Range.

The bold mountains between Big Lost and Little Lost rivers, and 

also the similar range to the northeast of Little Lost River, are in 

either case sharply defined monoclinal ridges, rising some 5,000 or 6,000 

feet above the adjacent valleys, and composed of stratified rocks which 

dip northeastward. Quartzite and limestones occur in three. ranges, 

but even the prevalent character of the rocks composing them is 

unknown.
46 SNAKE EIVEE PLAINS OF IDAHO. [BULL. 199.

LIMESTONE.

The first limestone noticed in my journey from Boise eastward was 

at Martin post-office, where there are ledges of this rock, of a bluish 

color, changing locally to nearly pure white and containing crinoid 

stems. The strike is southwest and the dip 15° northwestward. 

About 3 miles to the west of the locality just referred to and on the 

west side of the valley of Lava Creek a conspicuous ridge of bluish 

limestone, bearing about northeast and southwest, was in view, but was 

not visited. - In the valley of Little Lost River, near Howe, other outcrops of bluish limestone occur.

The age of the limestone and of the associated and apparently far 

more abundant quartzite is not known, but judging from their location and their relation to terranes occurring farther north, in the 

vicinity of Hailey, Challis, etc., examined b}7" G. H. Eldridge,ft and from 

their resemblance to other formations of known age in southeastern 

Idaho and the adjacent portion of Utah, it is probably Paleozoic. It 

seems likely that future studies will show that they range in age from 

the Silurian to the Carboniferous.

ROCKS OF SOUTHEASTERN IDAHO.

The geology of the extreme southeastern portion of Idaho, lying 

east and southeast of Snake River, was studied by the geologists of 

the "Hayden survey "in 1871 and subsequent years, and is represented on a "geological map of portions of Wyoming, Idaho, and 

Utah" which accompanies the twelfth annual report of that-survey. 6 

The portion of Idaho referred to has not been examined by me, but 

judging from the map mentioned above and the information contained 

in the itinerary reports by F. M. Endlich, F. H. Bradley, A. C. Feale, 

and Orestes St. John, published in the sixth and eleventh annual 

reports of the survey just referred to, it has a close resemblance in 

the nature of its rocks, structure, topography, etc., to the region to 

the west of the Snake River Plains, known as the Lost River country. 

The rocks forming the prominent mountains to the east of Snake 

River are largely limestone and quartzite of Silurian and Carboniferous age, while the valleys, beginning on the east, near Soda Springs, 

and extending northwestward to the Snake River Plains, are mostly 

floored with basalt. In addition to basalt, the valleys contain deep 

accumulations of de*bris swept down from the neighboring uplands 

and deposited as alluvial fans.

LEADING FEATURES OF THE GEOLOGICAL STRUCTURE.

The general trend of the mountains in southeastern Idaho, as is 

indicated on the maps published by the Hayden survey referred to

a Sixteenth Ann. Kept. U. S. Geol. Survey, 1895, pp. 226-230.

&U. S. Geological and Geographical Survey of the Territories; a report of progress of the explorations in Wyoming and Idaho for the year 1878, Washington, 1883.
RUSSELL.] PEE-TERTIAEY FORMATIONS. 47

above, is northwest and southeast. On the west side of the Snake 

River Plains, in the Lost River country, the ranges, judging from distant views, are prevailingly raonoclinal; that is, they are formed by 

the upturned edges of large blocks of the earth's crust, in which the 

bedding planes dip in one direction. Under the generally accepted 

explanation of the origin of ridges of the nature of those just cited, 

they are considered as having been produced by breaks along which 

differential movements on the two sides have occurred. The rocks on 

one side of a break have been elevated or those on the opposite side 

depressed, producing what is termed a fault. The steeper sides of 

the ranges are fault scarps more or less eroded and perhaps largely 

concealed beneath rock waste in the form of talus slopes and alluvial 

fans. The monoclinal ridges forming the Lost River Mountains are 

seemingly of the Great Basin type, but, unlike the representatives of 

that type in Utah, Nevada, southeastern California, etc., trend northwest and southeast instead of at right angles to that course, as is common throughout much of the Great Basin."

The geological structure of the various ranges and ridges composed 

principally of quartzite situated southwest of the Lost River Mountains is little known, except that the presence of faults is indicated by 

the diverse inclination of the strata in neighboring ridges and that 

much movement along breaks trending in general northwest and 

southeast has taken place. Farther west, from near Shoshone to 

beyond Boise, as previously stated, extensive faulting has occurred, 

as may be readly seen in the portion of that region which is composed of stratified rhyolite. Near Boise, where the nearly level 

Snake River Plains meet the mountains on their northern border, the 

bold mountain front, composed principally of granite, has been ascribed 

by Lindgren 6 to faulting. My studies in the same region and in 

the area east of it to King Hill Creek and near Shoshone, serve to confirm this view. The leading facts tending to support this conclusion 

are: First, the alignment of the steep precipices which descend from 

the mountains to meet the plain, and the fact that both the granite and 

the rhyolite of which' the mountains are principally composed terminate abruptly at the escarpment referred to; second, from this line of 

escarpments branching faults extend into the mountains formed of 

rhyolite; these branching faults form in fact the main escarpment for 

a distance sometimes of several miles before departing from it sufficiently to become individualized; third, the presence of recent faults 

at and near the base of the mountain in the vicinity, of Mountain 

Home, and in the basalt covering the adjacent depression; fourth, the 

presence of hot springs along the base of the straight mountain face 

where it meets the plain and where evidence of recent movement

a A comprehensive account of the leading structural features of the Great Basin may be found in 

G. K. Gilbert's Lake Bonneville: Mon. U. S. Geol. Survey, Vol. 1,1890, pp. 340-392. 

f>Geol. Atlas U. S., Boise folio, 1898.
48 SNAKE EIVEK PLAINS OP IDAHO. [BULL. 199.

occurs. All of these several lines of evidence when studied in the 

field lead to the same conclusions, and, I think, prove that the striking 

change in topography at junction of the Snake River Basin with the 

mountain to the northeast, in the vicinity of Shoshone, Mountain 

Home, Boise, etc., is due primarily to faulting. This fault, however, 

is not a single, definite fracture, but a series of irregular and branching fractures, the rocks on the northern side of which have been 

upraised or those on the southern side depressed. In the mountains 

composed of rhyolite, north of Mountain Home, the several faults are 

readily seen from many commanding summits. The trend of these 

breaks, which define the borders of prominent monoclinal ridges, 

is in general from N. 20° to N. 40° W. The strata composing the 

blocks between the faults are in most instances inclined downward 

to the northeast at angles of from 15° to 20°. .Certain of these fault 

scarps, when traced southward, merge into and form a part of the 

general line of bluffs bordering the Snake River Plains. The conspicuous mass of stratified rhyolite forming Mount Bennett, is, so far 

as can be judged from its leading topographic features, a representative example of a tilted fault block of the nature just referred to^ but 

the secondary elements in the structure of the mountains are unknown. 

This block presents its bolder escarpment to the southwest, and the 

beds of which it is composed dip toward the northeast. The extremely 

bold southwest face of the mountain is a part of the general line of 

escarpments which descends to and defines the northern border of the 

Snake River Plains in Elmore and Ada counties.

Practically nothing is known of" the structure in the mountainous 

region bordering the Snake River Plains on the south, except that in 

the Rock Creek Hills a monoclinal structure similar to that of the 

Mount Bennett region is present.

The occurrence of folds in the rocks of southern Idaho is not denied, 

but as structural features influencing the present topography, they are 

believed to be subordinate to the faults.

Although the details in the structure of the rocks, even along the 

best known portion of the border of the Snake River Plains, Avith the 

exception of the area included in the Boise folio, remain to be studied, 

and even the major features in the relief are, to a great, extent, 

unmapped, it seems safe to conclude, at least provisionally, that the 

great depression through which Snake River flows is due in part and 

mainly to displacements along "lines of fracture and an upward bending in'the region occupied by the Owyhee Mountains.

EARLY GEOLOGICAL HISTOEY OF THE SNAKE RIVER BASIN.

While the great depression in southern Idaho occupied by the Snake 

River Plains is primarily due to the upheaval of the bordering mountains, it is probable that a large amount of erosion has taken place and 

that the depression was thus broadened and deepened previous to its
RUSSELL.] PEE-TEETIARY FORMATION. 49

becoming partially filled with the lacustral and stream sediments and 

lava flows which now occur in it and give it an essentially level floor. 

In traveling through that region nothing in reference to the present 

relief of the surface is more prominent than the fact that the leading 

features in the topography, excepting the broad plains, were in existence previous to the deposition of the sediments and the outpouring of 

the lava which had upgraded the great central depression.

The mountains of central and southeastern Idaho, so far as known, 

are composed mainly of Paleozoic or older rocks. The exceptions are 

certain Mesozoic formations described by the geologists of the Hayden 

survejr , which occur in the extreme southeastern portion of the State, 

and tilted Tertiary beds mapped by Lindgren, in the mountains near 

Boise. The Tertiary beds referred to, however,' and perhaps the 

Mesozoic (Juratrias) beds to the east of Blackfoot are of fresh-water

origin. The general interpretation to be put on these facts seems to be 

that southern Idaho has been a land surface, in part occupied by lakes, 

since the close of the Paleozoic. Although up and down movements 

have occurred since the Mesozoic and are, no doubt, still in progress, 

the mountains were formed mainly previous to the beginning of that 

era, and were deeply eroded previous to the beginning of the Tertiary. 

The great valley now occupied by the Snake River Plains, with its 

many lateral branches, was in existence previous to the Tertiary, and 

owes its dominant features to the upheaval of its bordering mountains, 

and the accompanying depression of the larger valley areas, together 

with long-continued erosion. During Mesozoic time a river no doubt 

flowed through the Snake River Valley, which received tributaries 

from the secondary valleys leading to it, and the land was deeply 

dissected and was of mature and even old topograph}^ previous to 

the Tertiary. The direction of flow of the stream which preceded the 

present Snake River is unknown, but was most probably westward. 

This river continued its work of removing the debris produced by the 

disintegration and decay of the bordering mountains for a very long 

period. No attempt will be made at this time to determine the details 

of the earlier portion of the geographic history of southern Idaho, but 

the general conclusion that we have there a land surface Avhich has 

been in existence since near the beginning of the Mesozoic era is one 

of much interest, on which must be based many conclusions of both 

purely scientific and economic importance.

As has been stated several times, the valle}7 s of southern Idaho have 

become deeply filled in many instances with alluvium deposited by 

streams, the sediments of lakes, and the lava and other products of 

volcanoes. These deposits demand special consideration, as they are 

intimately associated with the problem of obtaining artesian water, 

the development of springs, the desirability of excavating horizontal 

wells, etc.

Bull. 199 02 4
50 SNAKE EIVEE PLAINS OF IDAHO. [BULL. 199.

TERTIARY AND RECENT LACUSTRAL FORMATIONS.. 

PAYETTE FORMATION.

During the earlier part of the Neocene (Miocene) period, as determined by Lindgren that is, during Middle Tertiary time a large 

fresh-water lake occupied the Snake River Basin, and the sediments 

deposited in it are now a prominent feature of the country, especially 

to the west of Salmon and Malade rivers (PL I). These lacustral 

deposits have been named the Payette formation, for the reason that 

they are well exposed along the lower courses of Patyette River." The 

formation is extensive. As stated by Lindgren, it lies mainly to the 

south and west of the Boise Mountains, and occupies the whole of the 

lower part of the ridge between Boise and Payette rivers, and occurs 

throughout an extensive area in Oregon to the northwest of the mouth 

of the Owyhee River.

The rocks of the Payette formation are mainly sands, clays, and volcanic lapilli, with occasional beds of coarse gravel, especially near the 

bases of the bordering mountains. The strata have in many instances 

been consolidated, so as to form sandstone and soft shale, but to a 

great extent they are still soft, loose sands and slightly compacted 

sandy clays. At several localities in the Boise quadrangle, and again 

on Schaffner and Indiana creeks, I found the ordinar}' sedimentary beds 

to be interstratih'ed with layers of white volcanic dust several feet in 

thickness. The thickness of the Payette formation, as stated by Lindgren, is over 1,000 feet in the vicinity of Boise, but owing to lack of 

exposures and to the scarcity of deep borings, its maximum depth 

remains to be determined. Its extent, as well as its thickness, suggests that it is widely spread beneath the Snake River Plains, but 

although it was traced by me eastward from Boise to the region 

crossed by King Hill and Clover creeks, it there disappeared beneath 

lava flows and alluvial deposits and its presence beneath the central 

and eastern portions of the plain remains to be ascertained. In the 

mountains to the north of Boise, Lindgren found several detached areas 

of the Payette formation in which the strata were variously inclined, 

sometimes as much as 50°, showing that there have been extensive

«On the map forming PI. I no attempt has been made to separate the Payette and the Idaho 

formations. West of Mountain Home and north of Snake River lake beds and lava sheets arc 

interstratified in such a manner that it is impossible to represent them separately on a map of the 

scale used. The great preponderance at the surface of lake beds over lava sheets, in the region 

referred to, has led to my giving the entire region the color indicating the sedimentary formation. 

South of Snake River the area colored to represent lake beds is mostly without lava sheets.

The extension of the Snake River lava, shown on the map referred to, eastward from Blackfoot, is 

sketched from geological maps accompanying the Twelfth Annual Report of the United States Geological and Geographical Survey of the Territories, by F. V. Hayden, Washington, 1883. All of the 

geological data represented to th'e west of Garnet are from geological maps published by Waldemar 

Lindgren in the Eighteenth Annual Report, United States Geological Survey, Pi. Ill, Washington, 

1S98, PI. LXXXVII, and in the Twentieth Annual Report, Pt. Ill, of the same survey, Washington, 

1900, PI. Vill.
RUSSELL.] IDAHO FOKMATION. 51

earth movements and deep denudation since the time the sands, etc., 

were laid down in horizontal sheets in the old lake. No such detached 

areas have been discovered in the mountains to the east of the Boise 

quadrangle.

From what is known of the Pa}^ette formation, it seems that it has 

its greatest extent in southwestern Idaho and neighboring portions of 

Oregon, and while probabty present beneath the main portion of the 

Snake Elver Plains that is, to the east of Malade and Salmon rivers 

is there deeply buried, but little disturbed from its original horizontal 

position and not laid bare by erosion.

The upper limit of the beds deposited in Lake Payette is stated by 

Lindgren to be about 4,000 feet above the sea, but as quite extensive 

movements have occurred since they were laid down, the precise 

horizon of the surface of the old lake is difficult to determine. During 

the later portion of the Tertiary the waters of Lake Payette seem to 

have subsided, and possibly a new lake was formed in the same basin, 

principally in southwestern Idaho, in which sedimentation occurred, 

without, so far as is now known, a well-marked, if any, period of erosion intervening. The beds laid down in this younger lake and by 

streams discharging their sediments into the same basin, are less consolidated than those of the typical Payette formation, and are mostly 

loose sands and soft calcareous clays, with minor quantities of volcanic 

lapilli and dust and well-rounded gravel.

IDAHO FORMATION.

The presence of lacustral deposits in Snake liiver Canyon of younger 

date than the Payette is thus referred to by Lindgren in the Boise 

folio:

During the eruptions of the Pliocene basalt the extensive Payette Lake had dwindled to smaller dimensions. Its shore line for some time probably remained stationary at an elevation of 2,700 or 2,800 feet, but in this quadrangle [the area 

described in the Boise folio] there are few marks left of its existence, as most of 

these later lake beds have been obliterated by Pleistocene river wash. Along Snake 

River, from above Glenns Ferry down to near Nampa, late Neocene (Pliocene) lake 

deposits are found as white clays and sands interbedded with thin basalt flows, and 

well exposed in the river bluffs.

I make the above quotation not for the purpose of controverting 

the conclusion stated, but to record the fact that the observations presented below pertain to what Lindgren has decided are the deposits of 

a Pliocene lake, to which the name Lake Idaho was given by E. D. 

Cope. My observations of the abundant exposures of the Idaho formations on the borders of Snake River Canyon began on the west at the 

southeastern corner of Ada County and were continued eastward to 

Shoshone Falls. A few typical sections in this region will serve to 

show the nature of the deposits and their relation to the associated 

lava sheets,
52 SNAKE RIVER PLAINS OF IDAHO. [BULL. 199.

In the region examined below the mouth of Bruneau River the lava 

sheets forming the rim rock of Snake Elver Canyon on the north side 

do not extend south of the river. The south wall of the canyon is comparatively low and composed of soft, white, horizontally stratified sediments, which extend southward to the base of the mountains which 

define the border of the Snake River Basin in Owyhee County. A 

portion of the border of Lake Idaho is marked by the junction of its 

sediments with the rocks which formed its shore. The broad tract of 

-exposed lake beds in Owj^hee County is deepty sculptured and presents 

typical examples of "bad-land topography."

The precipitous northern wall of Snake River Canyon near the 

boundary between Ada and Elmore counties is about 4-50 feet high, 

and is composed of three principal varieties of rock, namely, in 

descending order, basalt, lapilli, and lacustral clay and sand. In 

general, the upper portion of the canyon wall is the edge of a lava 

sheet which underlies in part the thin covering of soil on the adjacent plain, and in part another similar lava sheet. In at least one 

locality the lapilli, which usually occurs below the basalt, rises higher 

than its surface, and forms the actual summit of the escarpment. The 

usual thickness of the basalt is from 20 to 40 feet. The thickness of 

the yellowish, earthy lapilli beneath the basalt is variable, in places 

being 180 feet, and at a distance of perhaps a mile from where the 

maximum exposure occurs, thinning out to but a few feet and even 

vanishing, the lake beds below thickening and occupying its place. 

From the locality referred to all the way to Shoshone Falls, the presence of three stages in the filling of the basin is frequently clearly 

exposed. All of the members of the series vary in thickness, and 

above the mouth of Bruneau River several sheets of basalt are sometimes present and the lapilli are wanting. The records of a few of 

the numerous sections examined will serve to illustrate these features 

in detail.

At a locality in Ada County, about 7 miles below the mouth of Canyon Creek, shown on PI. VII, the wall of Snake River Cairyon reveals 

the following section:

Section of watt of Snake River Canyon 7 miles below mouth of Canyon Creek.

Feet.

1. Black, compact, but somewhat scoriaceous basalt.......................... 20

2. Yellowish, slightly compacted lapilli, with angular fragments of scoriaceous

basalt sometimes 2 inches in diameter, and reddish pebbles of granitic rock.. 100

3. Thinly laminated lacustral clay............................'............... 180

4. Not exposed to the river, about. .......................................... 150

Total................................................................ 450

A mile farther west the rim rock of basalt is absent, and the bed of 

lapilli, there about 180 feet thick, rises above the level of the basalt 

in the adjacent portions of the canyon wall. The lapilli here contain
U. S. GEOLOGICAL SURVEY BULLETIN NO. 199 PL. VI

NORTH WALL OF SNAKE RIVER CANYON, ADA COUNTY, IDAHO.
RUSSELL.] IDAHO FORMATION. . 53

blocks of basalt 10 to 14 inches in diameter. In places the bed of lapilli 

is compact and stands in vertical walls from 20 to 30 feet high, more or 

less sculptured by wind erosion. In this stratum, also, there are at 

times local beds, usually less than a foot thick, of thinly laminated soft 

sandstone. About 2 miles east of the locality first mentioned, and at 

the end of a prominent bluff (PI. VI, J?), still more conspicuous variations wer-e observed in the strata forming the canyon wall, as is shown 

by the following section:

Section of wall, of Snake River Canyon 5 miles below mouth of Canyon Creek.

Feet.

1. Coarse basaltic breccia, fragments 3 feet in diameter ....................... 40

2. Compact, columnar basalt................................................ 6

3. Coarse volcanic breccia................................................... ° 20

4. Evenly laminated volcanic sand ........................................... 9

5. Yellowish stratified lapilli.............................................- -. 70

6. Fine, white, laminated calcareous clay..................................... 2

7. Yellowish stratified lapilli ............................................;.. 7

8. Fine, white, horizontally laminated clays, interbedded with fine, loose, 

cross-bedded, light-colored sand, becoming pebbly and cross-stratified at 

the top................................................................ 120

9. Unexposed to the river, about............................................ 100

Total ............................................................... 374

The highest rim rock of basalt, usually present in the portion of the 

canyon here referred to, is absent from above the summit of the promontory at which the section just given was observed, but is present 

near at hand. A capping of some 20 to 30 feet of basalt above the 

highest bed of breccia observed may at one time have existed, but has 

crumbled and fallen away.

From the mouth of Bruneau River upstream for about 6 or 8 miles 

the Snake flows between precipitous walls capped on each side by a 

conspicuous rim rock, as is illustrated on PI. VI, A. This view was 

taken from the summit of the northern wall of the canyon, just below 

the mouth of the Bruneau, looking downstream to the southwest, and 

into the broader portion of the canyon, which is excavated in soft sediment. Beneath the thick sheets of basalt, of which four are easily 

recognized in the lower part of the canyon of Canyon Creek, there 

are thick beds of gravel, sand, and clay, but lapilli are seemingly 

absent. At a locality on the left bank of the river near where it 

enters the wider portion of its canyon the following section is revealed:

Section of Snake River Canyon near mouth of. Bruneau River.

Feet.

1. Compact columnar basalt ................................................ 40

2. Stratified unconsolidated white sand ...................................... 30

3. Waterworn pebbles. .........................^........................... 15

4. Fine unconsolidated white sand .....:.................................... 12

5. Finely laminated, horizontally bedded sandy clay ......................... 250

Total ............................................................... 347
54 SNAKE RIVER PLAINS OF IDAHO. [BULL. 199.

In the vicinity of Leveridges Ferry, just above the mouth of Rattlesnake Creek, the canyon of Snake River is 6 or 8 miles broad, with a 

steep wall capped with basalt on the northern side and a less precipitous 

slope formed entirely of soft sediments on the southern side. As is 

commonly the case throughout the course of Snake River below Glenns 

Ferry, the plain bordering the canyon on the north rises gently northward, and is covered with fine, yellowish-white soil. In the precipitous and in part vertical escarpment forming the northern side of the 

canyon the following section was obtained, but the details change in 

a conspicuous manner, owing principally to variations in the number 

of sheets of basalt present, when the cut edges of the strata are followed even short distances, either up or down stream:

Section of Snake River Canyon near mouth of Bruneau River.

Feet

1. Columnar basalt, compact, contains numerous flattened steam holes an inch

in length, but is not glassy, and does not rest on a bed of lapilli or breccia.. 25

2. Horizontally and even-bedded sandy clay, in part clean, loose sand, largely

concealed beneath talus from basalt cliff above ........................ 210

Terrace about 1,000 feet wide, covered with well-rounded quartzite cobbles 

and sand; surface irregular. This layer of cobbles is from 5 to 15 feet 

thick, but is not a part of the section, having been deposited during the 

excavation of the canyon.

3. Fine, grayish-white, evenly laminated clay.............................. 35

4. Parting of white sand, uncon soli dated; can be traced along the face of the

bluffs for a mile or more ............................................. \

5. Fine, grayish-white clay, like No. 4 ..................................... 20

6. Fine, evenly laminated pinkish clay .................................... 30

7. Clean, well-rounded pebbles............................................ 1

8. White "sandy clay or silt.... .........^.............^.................... 4-5

Terrace, 200 to 300 feet wide, covered with cobbles.

9. Basalt, highly scoriaceous, glassy (lower rim rock)....................... 40

10. Fine, unconsolidated sandy clay, base concealed ......................... 35

11. Old flood plain, surface level, composed of fine silt ...................... 35

12. Modern flood plain, overflowed during high water ....................... 15

Total, about........................................................ 400

The conspicuous variations which occur in the number and thickness of the lava sheets exposed near the mouth of Rattlesnake Creek 

will be noted later, as well as the significance of the striking differences between the basalt which forms the two rim rocks present where 

this section was observed. The numerous minor variations exhibited 

by the sedimentary beds in this same region might be shown by many 

sections, but space will permit of but one more.

On the south side of Snake River Canyon, at a locality termed Shell 

Mountain, about 10 miles below Glenns Ferry and nearly opposite the 

mouth of Bennett Creek, the bold bluffs immediately bordering the 

river are composed almost entirely of fine, unconsolidated, nearly
U. S. GEOLOGICAL SURVEY BULLETIN NO. 199 PL. VII

SOUTH WALL OF SNAKE RIVER CANYON, HALLS FERRY, IDAHO.
RUSSELL.} IDAHO FOBMATIOtf. 55

white sand and evenly laminated nearly white clays, together with a 

thin sheet of basalt, which soon disappears when traced southward. 

The section observed at this locality is as follows:

Section of Snake River Canyon 10 miles l>eloio Glenns Ferry.

Feet.

1. Light-gray, laminated, fine-grained clay or silt, changing to white below.

By estimate ....................................................... 150-170

(This stratum forms the surface for many miles south of Snake 

River, and rises into low hills; at the border of the canyon it is deeply 

notched and well exposed.)

2. Scoriaceous basalt ..................................................... 4-lu

(Near at hand two sheets of basalt are present at this horizon; the 

upper are 6 and the lower are 10 feet thick, with 10 inches to 2 feet of 

sandy sedimentary material between; this layer is of a brick-red color 

and is traversed by vertical but tortuous steam holes.)

3. Associated with No. 2 is a bed of coarse, well-worn gravel................ 4-6

(This bed possibly indicates the summit of the Payette formation, 

as the beds below contain an abundance of Miocene fossils; those above, 

so far as known, are barren of fossils.)

4. Loose, well-worn pebbles, of a variety of rocks, including basalt, cross bedded,

ferruginous, in part loosely cemented ................................. 3T10

5. Unconsolidated, fine, nearly white sand, with occasional shaly layers, 

cemented at times into irregular concretionary bands, charged with 

fresh-water shells throughout.« Thickness above the river............. 300

Total, about ....................................................... 050

The basalt exposed at Shell Mountain is the attenuated margin of a 

widely extended sheet which underlies the plain to the north of Snake 

River, but which has been removed by the erosion of Bennett and other 

creeks, as Avell as by the main stream to which they are tributary. 

This is the only layer in the section that reveals the inclination of the 

beds composing it; it dips very gently southward.

The facts briefly presented in the last few pages and others that 

might be recorded, did space permit, show that Snake River in its 

course for at least 50 miles below the mouth of Salmon River, in general skirts the southern margins of lava sheets which underlie the plain 

to the north, but occasionally cuts across portions of the lower sheets 

which extend farthest southward. Where the river crosses a portion 

of a lava sheet and has cut a channel in it its canyon becomes narrow 

with steep walls. ' In such localities, if the basalt is thick, the canyon 

walls are nearly vertical; and if thin, a conspicuous rim rock appears 

above steeply sloping bluffs in part concealed by talus and landslides. 

When two or more sheets of basalt are present, rim rocks occur below 

the highest one, which forms the rim or "break"of the canyon. 

When only soft sedimentary beds are present, and this is only on the 

south side of the river, except in the vicinity of Glenns Ferry, the

«A list of the shells collected ut this locality is given on p. 56.
56 SNAKE RIVKJl PLAINS OF IDAHO. [BULL. 199.

canyon widens into a valley, frequently 6 or 8 miles broad, with a 

precipitous escarpment on the northern side and a less steep and less 

regular line of bluffs forming1 its southern border.

FOSSILS.

A

At Shell Mountain and near Glenns Ferry a large number of freshwater shells were collected, which, as determined by W. H. Dall, 

belong to the following species: 'Lithasia antiqua Gabb; Melania 

taylori Gabb; Corbicula idahoensis Meek; Bythinetta, species indeterminate; Flwninicola, species indeterminate but like Amnicola 

(Fluminicola) longinqua Gould, and fragments of Anodonta. The 

Anodonta shells occur whole in the deposits, but, on account of their 

extreme fragility, the specimens collected were much broken.

From lake beds higher in the series than those from Avhich the shells 

named above were obtained, well exposed in Little Valley, 9 miles 

west of Bruneau, internal casts of a large indeterminate species of 

Cannifett were obtained.

While the precise position of these fossils in the geological time 

scale has not been determined, they are certainly of Tertiary age, and, 

as stated by Dall, probably belong to the Miocene.

In the lake beds so well exposed in the northern portion of Owyhee 

County the frequent occurrence of fossil bones, some of them of large 

size, has been reported by ranchmen and others, but only a few individual bones and fragments of bones were collected. These were 

obtained from the surface portion of the lake beds exposed at the head 

of Little Valley, and although not sufficiently complete to permit 

specific determination, are stated by F. A. Lucas to consist of "a 

portion of the left scapula of a large cam el, one of the toe bones of 

a small camel, and a toe bone of Morotherium." ff Besides these 

mammalian remains, the vertebra, teeth, etc., of a fish related to the 

carp, Anchybopsis fasciolatus Cope, and the vertebra of a salmonoid 

fish, of the genus Rhabdofario Cope, Avere found in considerable numbers. In reference to the age of these fossils Lucas says: "They are 

all typical Pliocene species, such as are found in the Pliocene of 

Washington, Oregon, and Idaho."

Although the number of vertebrate remains obtained was small 

and of little scientific interest, there are indications, especially in the 

admirable state of preservation of the bones, that the beds from which 

they came will yield most important results in this connection when 

carefully searched.

At a locality near the head of Little Valley and in soft white lake 

beds belonging to the same formation as the neighboring la}T ers from

"An early representative Of the Edentates, including Megatherium, etc., which inhabited both North 

and South America in post-Tertiary times, and are remotely related to the living sloths and armadillos.
KUSSELL.] LACUSTKAL CONDITIONS. 57

which the fossil bones just referred to were obtained, fossil wood 

occurs in abundance. The wood is in. fragments, and was evidently 

waterwonij as if rolled up and down a beach before being buried, 

and replaced by silica. Mingled with the fossil wood are occasionally 

found silicified pine or spruce cones in an admirable state of preservation.

The meager data furnished by the fossils referred to above seems 

to indicate that the lower portion of the lacustral deposits cut through 

in forming Snake River Canyon belong to the Miocene and the upper 

part to the Pliocene, but at present it is impracticable to draw a line 

of division between the two. A summary of the evidence furnished 

by previous collections from'the lacustral deposits of southwestern 

Idaho has been given by Lindgren" and need not be reviewed at this 

time.

SUMMARY OF LACUSTKAL CONDITIONS.

The general succession of events recorded by the sedimentary beds 

considered above seems to be as follows: A large lake or possibly two or 

more successive lakes in- the same depression, the boundaries of which 

are known only in part, existed in the Snake River Basin in Tertiary 

times. In this lake several hundred feet of fine, evenly laminated clay 

or silt and volcanic dust and lapilli were laid down. The fact that loose 

sand in places 300 feet or more thick rests on the clays previously 

deposited suggests that the lake became shallow,-and the presence of 

beds, usually thin, of well-worn pebbles consisting of a variety of rock 

fragments indicates the occurrence of strong currents in a shallow 

water body, or else that the lake was drained and its exposed bed 

crossed by streams. These sediments, which in the most typical 

instances are clearly lacustral, contain beds of coarse, well-rounded 

gravel, such as is laid down by streams, and it is impracticable at 

present to determine just what part is the result of still-water and 

what part of flowing-water deposition. The occurrence of 150 feet 

or more of fine, evenly laminated sediments above the medial sand 

and gravel, as at Shell Mountain, shows that the lake after its lowwater stage again became broad and deep. So far as known, the lava 

flows which have produced such marked features in the walls of the 

Snake River and its tributary canyons were poured out during the 

middle and later stages in the history of the old lake. Some of these 

lava streams entered water and flowed over an irregular bottom, as 

will 1 e described later, while others show no evidence of such an 

occurrence. These facts seem to indicate that in some instances the 

lava entered a lake, filling the inequalities in its bottom, or flowed over 

an exposed and eroded lake bottom and into streams which occupied

^'Eighteenth Ann. Kept. U. S. Geol. Survey, Part III, 1889, p. 628, and Twentieth Ann. Kept., 

Part III, 1900, pp. 98-99.
58 SNAKE KIVEK PLAINS OF IDAHO. [BULL. 190..

the depressions. There is evidence tending to show that lacustral conditions continued after the highest sheet of lava in the region bejow the 

mouth of Bruneau River was poured out, but these higher beds, being 

unprotected by a hard cover, have been to a great extent eroded away. 

The volcanic eruptions were accompanied by the blowing out of large 

quantities of volcanic dust and lapilli; other fragmental deposits were 

produced when the lava flows, which, as is presumed, followed the 

explosive eruptions, entered water bodies.

ECONOMIC PROBLEMS.

As to the economic importance of the sedimentary beds just considered, I may say briefly that possibly some of the clays may be found 

suitable for brickmaking, should commercial conditions make this 

desirable. It has been suggested that the abundant outcrops of fine 

clay near Hagerman can be utilized in the manufacture of aluminum, 

the waterfalls near at hand furnishing the necessaiy power for electric 

smelting. The feasibility of such a plan, however, remains to be 

ascertained.

The principal interest, from an economic point of view, at present 

attached to the sedimentary beds referred to is in reference to the 

possibility of obtaining artesian water. As has been stated, these 

beds are in part close-textured clays and in part loose sands and 

gravel. The beds of lapilli are in general compact and do not allow 

the free percolation of water through them. One of the requisite 

conditions for the storage of subterranean water under pressure is 

thus present; that is, an alternation of pervious and impervious strata. 

Another requisite is that the succession of water-bearing and nonwater-bearing beds should be inclined, or, best of all, so bent as to 

form a basin. In the portion of the Snake River Plains to the west 

of Salmon Falls the strata are not horizontal, but inclined gentry 

downward from the bases of the bordering mountains toward the 

center of the plains; that is, the central part of the basin has been 

depressed, or its border raised, in reference to a nearly east-west axis, 

so as to give the strata a trough-like form. The longer axis of this 

trough below Salmon Falls has a gentle downward inclination or pitch 

to the northwest. This trough has the structural features of what is 

known as an artesian basin, but in the region thus far explored is only 

a portion of a completely inclosed basin, the location of its western 

margin being as yet unknown. Whether or not the major axis of 

the trough rises again to the west can not be told at present, but 

from such general knowledge as is in hand concerning the western 

portion of the Snake River Plains and the occurrence of pre-Tertiary 

rocks in the canyon of Snake River below Weiser, it is presumed that
SNAKE RIVER LAVA. '59

a completely inclosed basin exists. Other facts in this connection, the 

best method of testing the artesian conditions of this basin, etc., will 

be considered in the second part of this report.

POSSIBLE EASTWARD EXTENSION OF THE TERTIARY SEDIMENTARY BEDS.

The wide extent of the exposed portions of the lacustral deposits in 

.the western part of the Snake River Plains, and the absence of exposures of such rocks in their eastern portion, is seemingly to a great 

extent in the nature of an accident. In the region below the mouth of 

Salmon River, lava sheets are less thick and probably less numerous 

than east of that locality. Below Shoshone Falls the Snake has cut 

deeply into the beds beneath the plains, and each tributary stream, 

at least near its mouth, is also in a canyon; but upstream from the 

locality mentioned the plains. are much less dissected, and over vast 

areas they are uneroded. The presence of extensive sedimentary beds 

beneath the lav.a flooring the broad eastern division of the plains can 

not now be determined from direct evidence. What is known of the 

pre-Tertiary topography of the Snake River Basin, however, and the 

extent and thickness of the sedimentary deposits in its western portion, etc., favor the hypothesis that beneath the surface lava sheets in 

its eastern part extensive beds of clay, sand, etc., do occur. This is 

an important question in reference to the possibility of obtaining water 

in the broad, unbroken "portion of the plains, but one that can be 

definitely answered only by drilling.

SNAKE RIVER LAVA.

The name Snake River lava is here proposed as a general term by 

which to designate the basaltic rocks that underlie by far the larger 

part of the Snake River Plains, and to a great extent form their actual 

surfaces. It includes, also, the lava streams and -associated cinder 

cones, etc., which have descended lateral valleys or adjacent mountain 

slopes, and united with the sheets of similar material extruded from 

numerous craters on the plains. When this extensive formation is 

studied in detail, it will, I judge, be found practicable to separate it 

into several distinct portions, and to correlate some of these with sedimentary beds containing fossils, and thus determine their precise geological age.

EXTENT AND THICKNESS.

The extent of the Snake River lava is represented approximately on 

the map (PI. I), on which the boundaries of the lava-covered country 

where known are indicated by a broken line, and where merely inferred 

the shading is not definitely margined. The area shaded by single lines
60 SNAKE RIVER PLAINS OF IDAHO. [BULL. 199.

on the map represents the region where lava sheets, and, to a minor 

extent, beds of scoriae and lapilli, occur at the surface, or are present 

beneath a thin covering of soil. In certain localities in the western 

portion of the Snake River Plains lava sheets are more or less completely covered by sedimentary deposits, and hence are not indicated 

on the map, which represents only the formations on the surface. The 

change is gradual from where the lava is the most prominent surface 

feature in southeastern Idaho to where, at the west, sedimentary deposits greatly predominate, but it was found impracticable to represent this on the accompanying map.

The estimated area covered by the Snake River lava is in the 

neighborhood of 20,000 square miles. So far as is now definitely 

known, there is but one lava field in North America of greater extent, 

namely, the Columbia River lava, the estimated area of which is about 

200,000 square miles. In Snake River Canyon, below Shoshone Falls, 

nearly 700 feet of lava in horizontal sheets are exposed, but whether 

this is the maximum thickness or not can not be told.. ° As a rule, the 

various sheets of lava are relatively thin, averaging perhaps 50 to 80 

feet, and widely extended. That many independent outflows of lava 

have occurred is easily seen, but in the walls of Snake River Canyon, 

where the best sections are exposed, it is difficult to determine their 

number, unless lacustral deposits, beds of lapilli, etc., occur between 

them. Near the mouth of Rattlesnake Creek four separate sheets are 

present, and others not represented at that locality.occur but a few 

miles away. In no single vertical section along Snake River could 

more than four sheets be definitely recognized; but this number will 

no doubt be increased when an opportunity is afforded for detailed 

examination.

While the various sheets of lava are in general essentially horizontal 

and in the position in which they were spread out, there are interesting exceptions to this rule. Over an area beginning near The Thousand Springs and extending westward the lava sheets have been gently 

folded, and near Salmon Falls there is a suggestion that the lowest 

sheet of lava exposed was gently folded before the thick bed of clay 

and the lava sheets above it were spread out. These deformations, 

however, are so gentle and extend over such large areas that much 

more extended and accurate data than could be obtained during a 

reconnaissance are needed for their study.

RELATION TO THE COLUMBIA RIVER LAVA.

The lava occurring on the Snake River Plains is so similar in nearly 

all its features to the still more extensive formation known as the 

Columbia River lava, through which Snake River has cut a magnificent 

canyon in western Idaho, near Lewiston, and from there to its junction
U. 8. GEOLOGICAL SURVEY BULLETIN NO. 199 PL. VII

,. « . .. .'..:*£&

A. REMNANT OF SNAKE RIVER LAVA, KING HILL CREEK.

Ji. BLOCK OF COLUMNAR LAVA, SNAKE RIVER CANYON.
RUSSELL. I TWO TERTIAKY LAVAS. 61

with the Columbia, that the relation of the two becomes of interest. a 

The country separating these two areas of basaltic rock has not as yet 

been geologically explored, and while it is .possible that a direct connection between them may be discovered, it seems more probable that 

they are distinct and have somewhat different histories. From the evidence now in hand, it appears that the Snake River lava is in general 

much younger than the related formation to the westward, although 

its basal members seem to be of about the same age. The principal 

part of the Columbia River lava, as shown by fossil leaves contained in 

the associated sedimentaiy beds, is of Miocene age. & The older portion of the Snake River lava, as indicated by its relation to the Payette 

formation, etc., as stated on a previous page, is also of Miocene age. 

Much reliance should not be placed in this correlation, however, until 

it is sustained by additional evidence. Although the first-formed 

sheets of the Snake River lava are perhaps of about the same age as 

the main mass of the Columbia River lava, by far the greater part of 

it is much younger. The latest outpourings of molten rock over the 

Snake River Plains, as will be described later, occurred probably 

within recent historical times, and are perhaps not over 100 to 150 

years old. While the Columbia River lava is deeply decayed and over 

large areas changed to a soft clay-like soil having a depth of 60 feet 

or more, the lava sheets on the Snake River Plains are still fresh, and 

even in the case of the exposed portions of the older sheets show but 

slight changes. These older sheets may have been covered for a long 

time by sedimentary deposits which have since been washed away, and 

thus preserved from decay, but this explanation can not be made to 

appl}7 to the greater part of the lava. The evidence furnished by a 

comparison of the state of preservation of the Snake River and the 

Columbia River lavas shows conclusively that the Snake River lava 

is in general much the younger of the two.

HYPOTHESIS OF FISSURE EKUPTIONS.

There is but little literature relating to the Snake River lava, but 

what has been published in reference to its origin (except by Lindgren)

"Descriptions of the Columbia Riverlava may be found in the following publications:

Geoige Gibbs, Report on the geology of the central portion of Washington Territory: Pacific 

Railroad Reports, Vol. I, 185-1, pp. 473-48G.

F. von Richthofen, The natural system of volcanic rocks: Mem. Cal. Acad. Sci., Vol, I, Part 

II, 1868. 

. Joseph Le Conte, Am. Jour. Sci., 3d series, Vol. VII, 1874, p. 168.

.T. W. Symons, Report on an examination of the Upper Columbia River, Senate Ex. Doc. No. 186, 

Forty-seventh Congress, first session, 1882.

I. C. Russell: A geological reconnaissance in central Washington, Bull. U. S. Geol. Survey, No. 

108,1893; A reconnaissance in southeastern Washington, Water-Supply and Irrigation Papers U.S. 

Geol. Survey, No 4, 1897; Volcanoes of North America; The Macmilian Co.. New York, 1897; 

Geology and water resources oi Nez Percc County, Idaho, Water-Supply and Irrigation Papers, U.S. 

Geol. Survey, Nos. 53 and 54,1901

(>F. H. Knowlton, Bull. U. S. Geol. Survey, No. 108, 1893, pp. 103-104,
62 SNAKE EIVEE PLAINS OF IDAHO. [BULL. 199.

favors tne view that the lava came to the surface through, fissures and 

was poured out after the manner termed by Richthofen fissure or 

massive eruptions, in distinction from the extrusion of molten rock, 

lapilli, etc., from well-defined vents, as in the case of Vesuvius and 

other well-known volcanoes.

The view that the lava forming so large a part of the Snake River 

Plains was supplied by fissure eruptions, interwoven with a graphic 

description of the leading scenic features of the region, is expressed 

in the folio wing quotation from Sir Archibald Geikie's charming book, 

entitled Geological Sketches at Home and Abroad : a

Never shall I forget an afternoon in the autumn of last year [1879] upon the great 

Snake Biver lava desert of Idaho. * * * We rode for hours by the side of that 

apparently boundless plain. Here and there a trachytic spur projected from the 

hills, succeeded now and then by a valley up which the black flood of lava would 

stretch away into the high ground. It was as if the great plain had been filled with 

molten rock which had kept its level and wound in and out along the bays and 

promontories of the mountain slopes as a sheet of water would have done, * * * 

I looked round in vain for any central cone from which this great sea of basalt could 

have flowed. It assuredly had not come from the adjacent mountains, which consisted of older and very different lavas, round the worn flanks of which the basalt 

had eddied. A few solitary cinder cones rose at wide intervals from the basalt plain, 

as piles of scoriae sometimes do from the vapor vents on the surface of a Vesuvian 

lava stream, and were as unequivocally of secondary origin. Hiding hour after hour 

among these arid .wastes, I became convinced that all volcanic phenomena are not 

to be explained by the ordinary conception of volcanoes, but that there is another 

and grander type of volcanic action where, instead of issuing from a local vent, 

whether or not along a line of fissure, and piling up a cone of lava and ashes around 

it, the molten rock has risen in many fissures, accompanied by the discharge of little 

or no fragmentary material, and lias welled forth so as to flood the lower ground with 

successive horizontal sheets of basalt. Recent renewed examination of the basalt 

plateaux and associated dykes in the west of Scotland has assured me that the view 

of their origin and connection which first suggested itself to my mind on the lava 

plains of Idaho furnishes the true key to their history.

The reference in the above quotation of "a few solitary cinder cones 

at wide intervals" is accompanied by a picture-showing three conical 

mounds rising from a broad plain. This sketch is evidently intended 

to represent the three prominent elevations in the central part of the 

great plain to the northwest of Blackfoot, known as Big, Middle, and 

East buttes. As previous!}" stated, these buttes were visited by me 

and found to be older than the Snake River lava, and entirely surrounded and separated one from another by it. Big and East buttes 

are the crumbling remnants of rhyolitic cones which rise as steptoes 

through the encircling basalt. Middle Butte is of stratified basaltic 

rock, and although its history was not definitely determined, it is certainly not a cinder cone and does not mark a center from which the 

surrounding basalt came. The elimination of these three buttes from 

the list of cinder cones seems to make Geikie's conclusion as to the

a Few York, 1882, pp. 237-238, 242-245.
RUSSELL.] MANY SMALL CRATERS. 63

absence 01 centers of eruption still more secure, as they are the most 

conspicuous elevations to be seen throughout the entire extent of the 

lava plains. Although the idea that the lava reached the surface as 

immense fissure eruptions has perhaps gained general acceptance, my 

observations failed to sustain it, but, on the contrary, led me to conclude that many local eruptions from distinct vents are accountable for 

the origin of the extensive sheets of once molten rock. While future 

studies may perhaps show that actual fissure eruptions have occurred, 

I know of no facts to sustain such a hypothesis.

SOURCE OF THE LAVA.

It is true there is an absence of conspicuous cinder cones on the 

Snake River Plains, and, as stated by Geikie, there is certainly no 

" centralcone from which this great sea of basalt could have flowed." 

Yet a more intimate acquaintance with the region shows that there 

are several localities at which lava was outpoured from local vents of 

the ordinary volcanic type, about which scoria and cinder cones were 

formed. Besides these more conspicuous monuments of local eruptions, there are many broad, low elevations built of lava of a type not 

seen by me elsewhere, and, so far as I can judge, not clearly recognized 

by other observers, which may, for convenience, be designated as lava 

craters." Instead of an absence of local eruptions from definite vents, 

my examination showed that there are scores of such localities still 

recognizable, and suggestions of many-other more or less completely 

buried beneath more recent effusions of molten rock. The welldefined cinder cones referred to, with more or less perfect craters in 

their summits, are represented by two buttes, each between 500 and 

600 feet high, situated on the lava plain about 6 miles northeast of 

Market Lake (PL XVI). About 20 similar elevations occur in what 

are known as the Cinder Buttes, on the west side of the Snake River 

Plains, approximately midway between Little Wood River and Big 

Lost River (PL X), and again by Kuna Butte, 15, miles northwest of Mountain Home (PL XVII). These well-defined cinder cones, 

described more in detail below, grade into another variety of elevations, which are still more common, but may pass unnoticed until one 

becomes familiar with their characteristic forms. The elevation of this 

second variety is due to the emergence of vast quantities of highly 

liquid lava from a comparatively small and in most instances a decidedly circumscribed opening, and to its outflow in all directions, except 

when it met older uplands, so as to form a low elevation with exceedingly gentle slopes and widely expanded base. These elevations are

«The nearest approach in form and structure of any volcanic pile yet described to those referred 

to above are, so far as I can judge, the great volcanic mountains of the Hawaiian Islands. There is 

too great a discrepancy in size, as well as other features, however, between thesy two classes of 

examples to admit o£ their being referred to the same type
64 SNAKE RIVER PLAINS OF IDAHO. [BOIL. 199.

frequently 8 to 10 miles or more in diameter at the base, and perhaps 

only 200 or 300 feet high. In fact, their bases merge so gradually 

with the surrounding plain that no eye can recognize where the ascending surface actually begins. The sides of the elevations, although 

gentle throughout, increase in slope as the center is approached, and 

rise more perceptibly to meet the usually flat-topped summit portion. 

The profile of one of these broad, gently sloping elevations is shown 

on PI. XVIII. The most noticeable portion of the surface descent 

from the central flat area seldom has an inclination over 10°, while 

the long slopes farther away are so gentle that the angle they make 

with a horizontal line can scarcely be measured with an ordinary 

clinometer. These broad, low elevations are composed of black lava 

all the way from their indefinite margin to the flat area forming the 

summit, which is usually composed of highly scoriaceous, with at 

times minor quantities of fragmental material (lapilli, etc.). The 

fragmental material of the nature here considered is absent from the 

older elevations, or easily passes unnoticed, owing to the effects of 

weathering and the growth of grass, sagebrush, etc.

The history of these elevations, as recorded in their form and in the 

nature of the material composing them, is briefly as follows: They 

represent volcanic vents, from which highly liquid lava in vast quantities flowed away in all directions, and on their outer borders came to 

rest and hardened in a horizontal position. When the vents opened 

on a plain, the requisite slope for the outward flow of the lava was 

obtained by the thickening of the lava sheet itself, and it is this 

increase in thickness that produced the low elevation still remaining. 

These outwellings did not occur along the general course of a fissure, 

but from local vents. These were not accompanied by explosions, or 

the explosions were of a mild character, and but little fragmental 

material was produced. Judging from the sequence of events recorded 

in the Cinder Buttes, described below, the volcanoes of the type here 

considered probably built cinder cones during the earlier stages of 

their eruptions, which were carried away and perhaps buried by the 

subsequent effusion of lava. As stated above, the summits of the low 

lava volcanoes are characteristically flat when seen in profile. When 

visited, the flat portion of the fresher cones is found to be composed 

of highly scoriaceous lava, and may contain a depression. About 15 

miles north of Pocatello, a flat-topped butte of the nature just 

described has a small lake in the bowl at the summit during the rainy 

season. It is probable that man}'' of the similar elevations once had 

craters, but in most instances their rims have been broken and the 

depression within has been filled. It fact, a succession of examples 

illustrating this process might easily be obtained.

The number of lava craters of the nature just described has not 

been determined, as they are widely distributed over the lava plains.
U. S. GEOLOGICAL SURVE ULLETIN NO. 199 PL. IX

.-1. WALL OF CANYON CREEK CANYON NEAR MOUNTAIN HOME, IDAHO.

£. NORTH WALL OF SNAKE RIVER CANYON NEAR MOUTH OF LITTLE CAN YON, IDAHO,
RUSSEU-] 80UECE OF THE LAVA. 65

Several examples may be seen from the trains of the Oregon Short 

Line while passing between American Falls and Mountain Home. 

One of the elevations on the plain between Shoshone and Shoshone 

Falls, known as Flat Top Butte, displa}rs evidence of a former crater 

perhaps more conspicuously than usual. From the summit of one of 

the craters under consideration, situated about 20 miles north of 

Shoshone, between Little Wood and Big Wood rivers, I counted eight 

similar elevations, but others known to be present on the vast plain 

tying to the east were obscured by the desert haze. Several others were 

in view from the summit of Big Butte, on the plain to the west and 

south. The elevations referred to are so broad at the base, and so low, 

that when looking down upon them, as, for example, from the neighboring mountains, their presence might easily pass unnoticed, except 

when illuminated by a strong side light, although they are easily 

recognized from lower points of view, when seen in profile against 

the even sky line.

Not all of the volcanoes that supplied the lava forming the Snake 

River Plains, however, are situated on their surface. Several craters 

which sent long streams of lava down tributary valleys have been 

mentioned by previous observers, and some of these were seen by 

myself. Several craters composed largely of scoriaceous basalt are 

known to exist in the valleys to. the southeast of the Snake River 

Plains, as, for example, in Basalt Valley, Blackfoot Valley, etc., in the 

vicinity of Soda Springs. They have been described b}^ the geologists 

of the Hayden survey. Extensive lava streams came from these craters and followed the valleys, principally in a northwesterly direction, 

to where they open out into the broad Snake River Plains. Certain 

of the geologists referred to suggest that these lava flows, which gave 

several extensive valleys level floors, reached the greater valley bordering the Snake and assisted in the formation of its present surface, 

but that this really occurred is left undecided. In this connection 

F. H.Bradley a states that the basalt bordering Snake River may have 

come in part from the crater near Soda Springs, but remarks: "It 

hardly seems possible that after flowing 70 or 80 miles the lava sheets 

could still have retained sufficient fluidity to be spread out in a solid 

layer over the plain."

The craters and lava flows just referred to have not been critically 

studied by me, but what is known concerning them, when viewed in 

the light of other and similar occurrences, certainly suggests that the 

lava streams originating at the craters in the vicinity of Soda Springs 

:and descending the valle37 s occupied by the Portneuf and Blackfoot 

rivers, Willow Creek, etc., may have retained sufficient fluidity on reachIng the Snake River Plains to enable them to spread widely. These

a Sixth Ann. Kept. U. S. Geol. and Geog. Surv. Terr., Washington, 1873, p. 204.

Bull. 199 02 5
66 SNAKE RIVEK PLAINS OF IDAHO. [BULL. 199.

lava streams unite with the still more extensive sheets of similar rock 

along the border of Snake River without any marked topographic or 

other contrast to indicate that they are not portions of a single series. 

As will be shown below, lava sheets originating from volcanoes in the 

broad central basin in certain instances entered the mouths of lateral 

valleys and extended up them, as the waters of a lake would do, for a 

score or more miles. The direction from which the lava in the lateral 

valleys flowed can in many instances be readily determined and the 

extent of the individual lava sheets ascertained and mapped, but this 

does not seem to have been attempted by the survey referred to above.

The most definite and, as it seems to me, the most accurate statement in 

reference to the sources of the Snake River lava to be found in geological literature occurs in the text of the Boise folio, by Lindgren/' He 

says: "The basalts were erupted from a great number of inconspicuous craters, both in the plains and in the adjoining mountains. Their 

fluidity was remarkable, continuous flows of 50 miles or more being 

noted. One flow, for instance, followed the South Fork of Boise 

River for that distance down to its mouth." The lava just referred 

to was seen by me, and there is no doubt that after flowing fulry 50 

miles as a stream from 1 to 3 miles wide, and in general about 300 

feet deep, it retained sufficient fluidity after emerging from the valley 

through which it descended and entering the Snake River Plains to 

spread Avidely. This lava stream since it cooled and hardened has 

been dissected throughout its length by the river it displaced, leaving 

flat-topped terraces at numerous localities.

The sources from which the Snake River lava came are, as stated by 

Lindgren, in part in the mountains bordering the plains and in part 

on the plains themselves. It Avill be instructive, I think, if the volcanoes furnishing these two sources of supply be considered separately.

VOLCANOES AMONG THE MOUNTAINS.

The fact has already been mentioned that a portion of the lava now 

covering the Snake River Plains came as a narrow stream which 

descended the valley of the South Fork of Boise River for fully 50 

miles and that other and larger streams probably originated in the 

craters near Soda Springs. These examples need not be considered 

further, as I have no information to present concerning them in addition to what has already been referred to.

BLACK BUTTE.

The fact that volcanoes situated in the mountains bordering the 

Snake River Plains poured out lava in much the same manner as

"See also papers by the same author in Eighteenth Ann. Kept, U, S. Geol. Survey, Pt. Ill, pp. 635- 

G3C, and Twentieth Ann. Kept., Pt. II, pp. 99-100.
BUSSKLL.] BLACK BUTTE. 67

mountain springs supply creeks and rivers, and that the molten rock 

flowed clown valleys leading to the central depression, where it 

spread out in lake-like sheets, in a similar way to the downward flow 

and expansion of streams of water under analogous conditions is 

well illustrated by a volcano of recent date, and the lava poured out 

from it, situated on Big Wood River, about 20 miles to the north of 

Shoshone.

This volcano has no name, but in my notes I have designated it as 

Black Butte, on account of the color of the bare lava of which it is composed. It is situated about 20 miles from the general border of the 

Snake River Plains, and rises in the center of a valle}^ at a locality 

where, previous to its formation, the valley bottom was about 500 feet 

above the level of the neighboring portion of the plains. The volcanic 

mound is only about 300 feet high, with a base measuring, perhaps, 

2 miles in diameter. It is composed of highly scoriaceous lava, which 

flowed away in all directions in thin sheets. The copious outflow of 

molten rock was apparently continuous from the beginning of the 

eruption to its close, and the appearance of thin sheets is due to 

the manner in which cooling and the consequent stiffening of the 

material occurred. While the butte is composed of vesicular lava, 

there is no evidence from the presence of lapilli, cinders, etc., of an 

explosive eruption. There is no crater at the summit, such as explosive volcanoes build, although a deep, wide gulf at the top of the butte 

at first suggests such a depression. This-gulf, however, is of subsequent origin, due to fractures and the subsidence of a large mass of 

material, and connects with similar irregular breaks on the sides of 

the butte, due in part to the falling in of the roofs of lava tunnels.

The fact that this fresh and uneroded volcanic mound, without soil 

and almost entirely bare of vegetation, is not a cinder cone, but is composed of lava that hardened about the vent from which it was extruded, 

places it in the same category as the low, flat-topped lava buttes 

referred to on a previous page as being characteristic of certain of the 

older volcanoes on the Snake River Plains.

Black Butte is, as stated, situated in a valley, and the lava poured out 

by the volcano which formed it had greater freedom to flow down the 

valley than in other directions. Although the conduit leading down 

into the earth was certainly small, a vast volume of highly liquid rock 

was poured out and flowed down the valle}^ of Big Wood River for a 

distance of 35 to 40 miles, and spread out in a sheet from 2 to fully 6 

miles broad. The area covered by this single eruption is about 150 

square miles. The lava is black, with an exceedingly rough surface, 

and can be distinguished at a glance from the older sheets of similar 

material over which it flowed. About 3 miles below its source it passed 

between two lava volcanoes of the same general type as the one from 

which it came, but of much older date, and now covered with soil of
68 SNAKE EIVEE PLAINS OF IDAHO. [BULL. 199.

teolian origin from base to summit and clothed with vegetation. 

Although black and rugged and not jret dusted over with sufficient 

soil to support vegetation, except in the cracks and smaller depressions, 

the age of the lava stream is certainly considerable as measured in 

years. Big Wood River, after being displaced by the lava stream, 

continued to flow after the lava cooled, and throughout its length has 

cut a steep-sided canyon which is, in general, from 20 to 40 feet deep. a 

The walls of this. canyon are composed for the most part of hard, 

columnar basalt, and its excavation must certainty have required 

several centuries. This is interesting, when taken in connection with 

the absence of soil on the lava, as illustrating the slowness with which 

the soil of the Snake River Plains was accumulated. Extensive lava 

flows, the boundaries of which can not now be definitely traced, were 

poured out by the two older volcanoes just referred to, and the manner in which they are crossed and in part buried by the recent flow 

serves to show the manner of formation of the Snake River lava plains, 

into which the region here referred to merges by insensible gradations 

and of which it is, in fact, a part.

MARTIN LAVA STREAM.

The descent of lava streams from the mountains bordering the Snake 

River Plains and the expansion of the-lava so as to form a part of the 

plains themselves are again illustrated ~hy a flow of molten rock, which 

welled out from two openings in mountains of quartzite in the region 

drained by Lava Creek, about 5 miles southwest of Martin post-office, 

in Blaine Count}^. Martin is about 60 miles west of Blackfoot, on the 

west border of the Snake River Plains in their widest part.

In the bold mountains, at the locality referred to, an exceptional 

feature in the relief is furnished by a steep conical elevation from 600 

to 700 feet high, composed principally of basaltic scorise, the weathered 

sides and summit of which are conspicuous on account of their reddish 

color. At the base of this butte, on the northern and eastern sides 

and at an approximate elevation of 500 feet above-the level of the adjacent portion of the Snake River Plains, two streams of lava were 

poured out, which cascaded down the steep slopes below and united to 

form a trunk lava stream about 400 yards wide, which flowed northa An interesting feature connected with the erosion accomplished by Big Wood River is the presence in the walls of its canyon at a locality about 2 miles northeast of Black Butte of characteristic 

potholes. These potholes, of which a score or more were examined, are from a few inches to 10 feet 

or more deep, and in the larger examples about 20 inches in diameter. They have been excavated 

in compact basalt by the grinding of sand and pebbles, caused to rotate by a swift current, and have 

smooth, nearly vertical walls. The only peculiar feature presented by them is the presence in certain instances of central conical elevations at the bottom from a few inches to fully a foot high, 

which have spiral grooves on their sides. On looking down into a pothole exhibiting this feature, the 

seemingly spirally twisted elevation at the bottom has the appearance of the end of a large screw. 

So far as I am aware, the only other observed remnants of cores cut by revolving stones during the 

formation of potholes have been noted by G. K. Gilbert, Explorations and Surveys West of the one 

hundredth Meridian, Vol. HI, Washington, 1875. p. 73.
RUSSELL'.] LAVA STEEAMS. 69

ward with well-defined banks. On reaching the lower portion of the 

valley of Lava Creek, this lava stream expanded to a width of about 1 

mile, and continuing on to the Snake River Plains spread out still more 

widely, forming a thin sheet with an exceedingly rough surface. The 

length of this stream is not accurately known, but is probably about 

10 miles. . Where the lava came to the surface there are no elevations, but 

instead two circular depressions now overgrown with aspens which 

make them conspicuous. These depressions are small, probably not 

over 300 feet in diametev, but discharged a large amount of molten 

rock. The absence of elevations about the summits of the conduits 

is due to the fact that explosive eruptions did not occur, and owing 

to the steepness of the slopes on which the vents were situated the 

the lava flowed away immediately on emerging and did not cool and 

thicken about them. The lava, in descending the steep slopes below, 

where it came to the surface, formed veritable cascades, and on cooling 

was left with an excessively rough surface. The crust first formed 

was broken and the fragments were cemented together by still plastic 

lava, so as to make a coarse breccia. Many masses, composed of united 

fragments of all dimensions up to 20 feet or more in diameter, were 

floated far down the stream and out on to the border of the Snake River 

Plains. The contrast between the rough surface of this high grade, 

and consequently swift lava stream, and the smooth surfaces formed on 

sluggish lava streams on hardening, will be referred to later.

Although the lava stream just described is comparatively small and 

made but a moderate contribution to the filling of the Snake River 

Basin, it illustrates one of the methods by which the broad plains of 

that great depression were formed.

The Martin lava stream is black and has but little soil or vegetation 

on its surface, and is plainly much }rounger than the lava sheets it 

crossed and partially buried after emerging on the plain. It has lost 

much of its freshness, however, and is certainly much older than the 

lava which came from Black Butte, and is much older, also, than the 

several lava streams described below, which came from the neighboring Cinder Buttes.

LITTLE CANYON LAVA STREAM.

Little Canyon Creek rises in the rugged mountains about 20 miles 

northeast of Mountain Home, flows southward for about 20 miles, 

through a deep, narrow canyon cut in lava and associated sedimentary 

beds forming the Snake River Plains, and joins Snake River at Glenns 

Ferry.

After a stream older than the present Little Canyon Creek had 

excavated a valley in the mountains, it was displaced by a flow of basalt 

which came to the surface about 5 miles or more to the north of the
70 "SNAKE RIVER PLAINS OF IDAHO. [BULL. 199.

border of the Snake River Plains and approximately 1,000 feet higher 

than their present surface. The lava descended a slope which rises 

from the plain with an estimated gradient of about 200 feet to the 

mile, and on leaving the mountains spread far and wide on the adjacent plains. The sheet of lava thus formed reached the site of Snake 

River and appears as a rim rock in the bluffs at Glenns Ferry. In 

the mountains the lava stream cooled with a rough surface, but on the 

plain became quite smooth. Its surface is no longer fresh in appearance, and where not covered with soil it is much broken and a sheet of 

loose, weathered stones and bowlders, with dark soil in the crevices, has 

been formed. That this lava is of comparatively ancient date is shown 

also by the amount of work that has been accomplished by the creek 

that flowed over it. Little Canyon Creek, although now dry during the 

summer season, and thus evidently a weak stream, has excavated a 

remarkably rugged canyon in the basalt and underling rhyolite to 

a depth of 200 feet where it leaves the mountains. The lava sheet cut 

through is compact, and at the locality just referred to is about 50 

feet thick and nearly a mile broad.

KING HILT, LAVA STREAM.

In the region drained by King Hill Creek (the next creek east of 

Little Canyon Creek), as was observed from a distance, there is a large 

lava flow, which descended the mountains at about the same time the 

Little Canyon flow occurred, and spread widely on the plain to the 

south. The appearance of a remnant of this lava sheet, left as an 

outstanding" butte by the erosion of King Hill Creek, is shown on 

PI. VIII, A.

BLANCHE CRATER.

In the canyon of Clover Creek, about 1 mile south of Blanche postoffice, there is a black cone which rises about 60 feet above the adjacent 

flood plains of Clover Cveek and has a perfect crater in its summit. 

The conical pile is composed principally of thin cakes of highly vesicular black lava, some of which are strewn about on the surrounding 

stream-formed sediments and were evident!}' blown out by the volcano in a highly plastic or actually liquid condition. Within the 

relatively large conical depression in the summit of the volcanic 

pile there is a shallow lake of intensely alkaline water, which is supplied by small, warm springs. The concentration of the water by 

evaporation has led to the precipitation of alkaline salts mingled with 

organic matter. Forming the shores of the lake and underlying it 

there is a bed of alkaline salts having an average depth, as reported 

by Mr. B. C. Brey, who owns a neighboring ranch, of about 15 feet, 

and an area of 3 acres. This deposit has been utilized in a small way 

in the manufacture of soap. From the base of the crater a small
RU88EI.T..J VOLCANOES. ' l

lava stream extends southward about 1 mile. This stream crossed the 

valley diagonally and formed a dam that checked the flow of Clover 

Creek and caused it to spread.out a broad gravel deposit, which is 

now rich meadow land. About a mile north of this interesting crater 

there arc copious springs with a temperature of 117° F.

This crater is one of the latest and possibly the youngest of those 

visited by me in southern Idaho, and is situated in the bottom of a 

canyon about 500 feet deep, excavated in Snake River lava and associated beds of lacustral sediment and lapilli belonging to the Payette 

formation.

SUMMARY.

The lava streams which are known to have originated in the mountains lying north of the Snake River Plains, and which descended to 

them, are, in their order from west to east, the one which descended 

the canyon of the South Fork of Boise River and the Little Canyon, 

the King Hill, Black Butte, and Martin lava streams. These observations abundantly confirm the conclusion reached by Lindgren, already 

cited, and expressed in part as follows: a

The largest flows, however, originated in the foothills north of Glenns Ferry, or 

in fact all along a line extending from Smiths Prairie on the South Fork of the Boise 

to a point northeast of Shoshone. Along this distance of 80 miles the granitic foothills are completely flooded by heavy masses of black basalt flows, which extend 

far out into the valley and are here beautifully exposed interbedded with lake beds 

along the canyon of Snake River.

As previously stated, it is probable that the several craters in the 

neighborhood of Soda Springs furnished similar contributions, which 

reached the Snake River Plains from the southeastward. Lava is also 

reported to occur in the Owyhee Mountains, and it is to be expected 

that other additions to the Snake-River Plains from that source will 

be discovered.

VOLCANOES ON THE SNAKE RIVER PLAINS.

A critical str.dy of the numerous extinct volcanoes of southern Idaho 

would no doubt show that they may be divided, for convenience, into 

two classes, namely, those which built up cinder and lapilli cones of 

the ordinary type, and those which gave origin to but little fragmental 

material, but formed low, usually flat-topped mounds with immensely 

expanded bases. This classification, while indicating the present condition of the volcanoes in question, is not strictly^ogical, as the lava 

mounds were preceded in many and perhaps all instances by cinder 

and lapilli cones, which were either destroyed or buried by the great 

effusion of liquid lava which marked the later stages in the eruptions 

of the volcanoes which built them. In fact, a gradation can be found

"Twentieth Ann. Kept. U. S. Geol. Survey, Pt. IK, 1900, pp. 99-100.
72 SNAKE RIVER PLAINS OF IDAHO. [^ULL.199.

between normal cones built of cinders, lapilli, etc., with well-defined 

craters, and other examples of a similar nature partially destroyed by 

lava flows which came later, and including, as the other extreme of the 

series, low, broad mounds, without craters, apparently formed entirely 

of lava flows. For this reason, and also because a sufficient number of 

the volcanoes have not as yet been studied, the classification suggested 

above will not be attempted. The study of the volcanoes of the Snake 

River Plains is best begun by a visit to the most recent and freshest 

of the series. None meet these requirements better than a group of 

volcanic cones termed the Cinder Buttes.

CTNDEK BUTTES. 

LOCATION.

Close to the west border of the Snake River Plains, in their widest 

part, midway between Cary and Martin, and nearly 70 miles due west 

of Blackfoot, there is a group of cinder cones surrounded by vast lava 

flows. These now extinct volcanoes are of recent date, are remarkably fresh in appearance, and furnish most instructive illustrations of 

the nature of the eruptions which deluged such a large part of southern Idaho with lava. The most conspicuous of the cinder and lapilli 

cones in the group of elevations here referred to is indicated on the 

General Land Office map of Idaho as "Old crater." To the residents 

of the region this conspicuous cone is known as Cinder Butte, arid J 

have thought best to term the entire group of volcanoes, of which it 

is a part, Cinder Buttes.

The most conspicuous of the Cinder Buttes (see PL X) rises with 

steep slopes to a height of 600 feet above the surrounding plains and 

is distant about 5 miles from the base of the bold mountains, composed 

of granite and quartzite, to the west, which sharply define the west 

border of the northeastern extension of the Snake River Plains. The 

volcanic mounds and cones comprising this group form a well-defined 

belt 3 or 4 miles wide, which begins abruptly at the base of the adjacent mountains and extend out on the vast plains in a southeasterly 

direction for from 10 to 15 miles. The buttes are most closely placed, 

and in fact much crowded at the western end of the belt, and become 

wider apart and even isolated in its eastern part. Detached from the 

main group, and about 5 miles southward from the highest of the 

buttes, are two small elevations, probabty lapilli cones.

TUFF CONES AND CRATERS.

The elevations comprising the Cinder Buttes are "composed, to a 

large extent, of angular fragments, such as dust and lapilli, blown out 

during violent eruptions. Lapilli, being a technical term, is used to
U. S. GEOLOGICAL SURVEY 

CINDER BUTTES, IDAHO, LOOKING SO
HUSSEU..I TUFF CONES ANT) CRATERS. 73

designate what may be said to be sand and gravel produced by volcanic explosions. This finer and usually exceedingly rough material, 

when more or less consolidated, passes under the general name " tutf." a 

Mingled with the tuff, and also due to explosions, are fragments and 

rough masses of scoriae, volcanic bombs, and thin, irregular, cake-like 

forms of lava.

The number of elevations composed of fragmental material of the 

nature just referred to can not be definitely stated, as the older ones 

have to a great extent been broken and more or less completely 

destroyed by the explosions to which the younger ones owe their existence. Several of the more perfect cones and craters stand on the ruins 

of older volcanoes, and many rounded hills of lapilli, smoothed by the 

wind, are evidently portions of craters which have lost their characteristic shape. Possibly there are 20 craters either complete or in what 

may be termed a fair state of preservation, but portions of perhaps as 

many more maybe seen, either isolated or partly buried beneath laterformed piles of fragments. In one place, about a mile northwest of the 

highest of the buttes, more than half of a crater approximately 150 

feet high has been removed, probably by explosions, and three conical 

depressions, with circular rims of lapilli, have been formed on the site 

of the ruined part. In certain instances, also, large portions of once 

perfect craters have been floated away by the lava which flowed from 

them. About the more conspicuous cones and craters still remaining, 

and especially to the north of the most prominent butte, there are 

extensive fields and rounded hills of lapilli which were evidently formed 

by showers of fragments carried to a distance from the volcanoes which 

produced them and deposited in broad undulating heaps. These 

smooth fields and low, rounded hills are in striking contrast with the 

frequently rough and angular surfaces of adjacent lava streams, and, 

like the tuff cones, present many pleasing variations in color, ranging 

from deep red through brown and purple to lusterless black. The older 

members of the Cinder Buttes are covered with grass and support an 

open forest of pine and fir, but the }^ounger ones and the younger lava 

streams which flowed from them are entirely bare. The trees in most 

instances are rooted in loose deposits of lapilli which have not decayed 

sufficiently to form what may be termed soil, but this deficiency has 

been supplied by dust brought by the wind, or by-the volcanic dust 

showered on the coarser deposits during late eruptions.

The highest of the Cinder Buttes rises as a prominent conical mass 

of reddish and black lapilli to a height of 600 feet above the surrounding plain and is far more prominent than any of its neighbors. About 

its base the rims of some five or six older volcanoes may still be seen.

«The term tuff, as here defined, is to be distinguished from tufa, the deposit formed by certain 

springs.
74 SNAKE E1VER PLAINS OF IDAHO. [BULL. 199.

Like several of the associated cones, it has no crater at the summit, 

but terminates in a rounded weather curve, the symmetiy of which is 

somewhat broken by crags of dark-red tuff.

The remnants of crater walls in several instances frequently exhibit 

well-defined stratification, the layers in the outer portion of the once 

conical pile dipping away from its center in all directions at low 

angles. An increase in dip occurs from the first-formed or lowest 

laj^ers to the higher ones, owing to the greater thickness of material 

deposited immediately about the orifice than at a distance from it. In 

the best section of a ruptured tuff and cinder cone observed the lower 

beds are nearly horizontal, while those about 80 feet above dip 

outward at an angle of 20°. The inward-dipping beds forming the 

funnel within the rim of a crater dip much more steeply than the outer 

layers, but are usually not well preserved. In the section of a crater 

just referred to the position of the former opening is shown by a confused mass of tuff and cinders which, in part, seems to have reached 

its present position by falling from above.

CHARACTERISTICS OP THE EJECTED FRAGMENTS. 

I

The fragments of volcanic rock which occur in such abundance at the 

Cinder Buttes, and of which the walls of the craters themselves are 

built, may be classified as dust, lapilli, scorite, clots, bombs, and lava 

cakes. To classifj^ it in still more general terms, this material may 

be divided into two classes: First, lava Avhich cooled and hardened in 

the crater from which it was ejected and was broken into fragments by 

steam or gaseous explosions, the fragments being sufficiently rigid 

not to undergo a change of shape during their aerial flight except, 

perhaps, by fracture on coming in contact with other fragments in 

the air or on striking the ground; and, second, lava which was projected into the air in a plastic and even liquid condition and assumed 

various shapes either during its passage through the air or on falling. 

There is no sharp division between these two classes, however, and a 

series of specimens grading from angular fragments to rounded bombs 

and thin, flat lava cakes formed by the spreading and cooling of 

splashes of highly liquid lava on striking the earth, might easily be 

collected.

Dust and lapilli. The material which presumably hardened-on the 

surface of liquid lava within a crater and was broken and blown out 

by steam or other explosions and fell about the opening from which 

it came or was widely distributed by the wind, consists mainly of 

angular fragments of highly scoriaceous lava which vary in size from 

dust particles to irregular masses several inches, and in some instances 

1 or 2 feet in diameter. The most common product of this process is 

highly vesicular lapilli, composed of rough, angular fragments ranging
RUSSELL.] NATURE OF THE VOLCANIC MATERIAL. 75

from a quarter of an inch up to an inch or more in diameter. This 

material was blown out in abundance and assorted more or less througho

the action of the wind, so that large surfaces are covered with fragments, of a nearly uniform size. The fragments are usually black or 

various shades of red, and in certain instances have a brilliant iridescence due, I presume, to changes which have occurred since they 

were exposed to the air, and which resulted in the formation of thin 

films on their surfaces.

About the Cinder Buttes, so far as observed, there is a notable 

absence of compact, rounded kernels and stratified beds of granular 

lapilli, such as form a large portion of the Market Lake crater and 

occur in stratified sheets, associated with lacustral sediments, in the 

western part of the Snake River Plains, as for example, near Glenns

Clots. The lava ejected in a highly viscous or nearly solid condition took on various shapes, depending on its degree of plasticity, 

and perhaps also the length of its aerial flight. This lava seems to 

have been principally in the form of ragged clots, which were blown 

out by mild explosions with low initial velocities, and which fell about 

the orifices from which the}^ came, and built up scoria cones with but 

small admixtures of lapilli and dust. At times these clots adhered 

one to another or to the surface on which they fell, but more frequently they were sufficiently rigid on striking to maintain their 

shapes, and fell so gently that the rqpgh projections were not broken. 

Evidently these masses, although solid, were not cold and brittle when 

they came to rest. They are always rough and irregular, and sometimes have a length of a foot with a transverse diameter of only 

2 or 3 inches, but more frequently they are excessively irregular but 

not markedly elongate, and of all sizes up to 40 inches or more in 

circumference.

Scoria. Numerous masses of scoria occur also, especially in the 

walls of certain small parasitic cones. These masses present the 

appearance of having been blown out of the craters in a highly plastic 

or semifluid condition, and of having become highly scoriaceous and 

rudely spherical during their short journeys through the air. These 

rough, ball-like masses, usually 8 to 16 inches in diameter, were sufficiently soft to adhere slightly one to another on coming to rest. Their 

exteriors are rough, usually brown or reddish, but not conspicuously 

scoriaceous, while within they are coarsely vesicular and at times 

nearly hollow, as is shown in the photograph, PI. XI, A. In one of 

these spherical masses, in the crust of which a hole had been broken, 

I found a bird's nest securely sheltered.

Itoiribs. Portions of the highly viscous and fluid lava in the throats 

of the volcanoes were in many instances thrown high in the air, and
76 SNAKE EIVEE PLAINS OF IDAHO. [BUM, 199.

on account of rotation during their flight assumed more or less regular spherical forms. Of these volcanic bombs, several varieties were 

recognized, the differences they present being due to variations in the 

degree of plasticity of the lava as it left the pool of molten rock from 

which it was blown and the length of its flight.

The most characteristic of the bombs are oval and in size and shape 

frequently resemble a modern football with a projection at each end of 

its longer axis. These characteristic projections, or "ears," show a 

well-defined spiral twist, as is illustrated on PI. XII. The surfaces 

of these bombs are black and glossy when fresh, and without vesicles 

visible to the eye, but sometimes exhibit more or less spiral lines in 

relief, which are in a general way parallel with their longer axis and f 

unite with or are prolonged into the twisted ridges on the projections 

at their extremities. At times also their surfaces are crossed by shallow cracks, as is shown in PI. XII, which appear to have formed in a 

thin outer crust, and to have been widened by a slight subsequent 

swelling of the still viscous mass within. In size they vary from less 

than 1 inch to several feet in length, not including the projections at 

the ends, which are usualty broken, but in some instances are 3 'or 4 

inches long. Some examples are nearly spherical, and the '' footballs " 

are sometimes slightly flattened parallel to the longer axis. The one 

shown at the bottom of PL XII is 13 inches long, including the remnants of the projections at the ends, and 7.9 by 4.7 inches, respectively, 

in its two diameters at right angles to the axis about which it was 

rotated." The largest specimen of this shape seen measured 9 feet in 

length and 12 feet in circumference. The nearly spherical bomb 

represented on PL XII measures 5.5 by 4.5 by 4.3 inches. In some <, 

instances the bombs, whether nearly spherical or markedly ovoid, 

appear to have been formed by the rolling together of irregular cakes 

of plastic lava, the edges of which form ridges and curved lines on 

the surface of the infolded mass, as may be seen in the photograph 

to which attention has been directed. f

Of the bombs having the external characteristics just described there 

are at least two well-marked varieties, as is discovered on breaking 

them. In certain instances there is a distinct outer crust or rind, 

composed of compact black basalt, measuring in general from a 

tenth to a fifth of an inch in thickness, and inclosing a highly vesicular interior; in other examples there is no outer rind, and the mass is < 

compact, or nearly so, throughout.

In the case of the bombs having a rind and cellular interior there is 

sometimes a thin outer layer, perhaps a third of an inch thick, which 

is scoriaceous and merges with the still thinner compact crust inclosed

aThis specimen is not from the Cinder Buttes, but from a much older crater, only a portion of w 

which remains, near the north base of Big Butt'e.
U. S. GEOLOGICAL SURVEY BULLETIN NO. 199 PL. XI

*...,-.,. »* .«^-~^»ato^araste;3

SECTIONS OF VOLCANIC BOMB, CINDER BUTTES, IDAHO.
in:ssEi.i..] VOECANIC BOMBS. 77

by it, but more frequently this outer cellular layer is absent. Within 

the thin crust the hollow vesicles or steam cavities are small and 

increase in size toward the center, where the}^ frequentty measure half 

an inch in diameter. A photograph of the broken surface of such a 

bomb, showing about one-fourth of its circular cross section, is'reproduced on-PL XI, B. The appearance of some of the vesicular bombs 

when seen in section is almost precisely.the same as the interior of 

a similar body from Ascension Island, a drawing of which has been 

published by Charles Par win. a It has been suggested by Darwin 

that the gradation in the size of the vesicles in the bombs found on 

Ascension Island, from large at the center to small near the inner 

surface of the inclosing rind, is due to the rapid rotation of the material while in the air, the " centrifugal force" thus generated tending 

to relieve pressure at the center and to permit the steam-filled vesicles 

inclosed in that part of the body to expand more than those near the 

surface. The bombs from - the Cinder Buttes having the internal 

structure described and figured by Darwin, were found near the 

craters from which they came, in several instances lying on their 

inner slopes, and do not seem to have made long aerial flights. 

Besides they are nearly spherical and without the spindle-like form 

with projecting ears, such as characterize associated bombS'Avhich 

cooled while rotating. For these reasons it does not seem that Darwin's explanation is applicable to the examples observed, and as an 

alternative I venture to suggest the following hypothesis:

As has been observed, metals on cooling from fusion give out gases 

which were previously dissolved or occluded in the molten mass, and 

it may reasonably be supposed that lava, especially if basic and rich 

in iron, would behave in a similar way. If, then, a mass of highly 

heated, viscous lava should be thrown out from a volcanic crater 

and its surface cooled quickly so as to form a crust, the vapors and 

gases given off by the mass within as it cooled would be retained 

and tend to form vesicles. As cooling progressed the vapors and 

gases would be forced toward the. center and there form the largest 

vesicles, room being furnished in part by the shrinkage of the magma. 

This supposed process, by which the vesicles are produced and 

increased in size from the rind toward the center of a bomb, is analogous to the formation of a crust on a loaf of; bread with a highly 

vesicular interior. In this connection attention may be again directed 

to the second figure on PI. XII, which shows the appearance of the 

surface of a bomb which became cracked, and the cracks widened 

owing to expansion from within. This is analogous to the widening 

of a cut on the surface of a loaf of. bread as it bakes. In brief, both

a Geological observations on the volcanic islands visited during the voyage of H. M. S. Beagle. 

London, 1844, p. 36.
78 SNAKE KIVEK PLAINS OF IDAHO. [BUM,. 199.

the absence of evidence of rapid rotation on the surfaces of the vesicular bombs in question and the correspondence of their internal structure with what should be expected to occur if lava on cooling from 

fusion extrudes previously dissolved vapors or gases favor the hypothesis here suggested.

The compact bombs usually, and, as it seems, invariably, have oval 

forms and twisted and projecting ends, and are composed of black 

stony lava throughout, but are never entirely free from steam cavities. 

The openings are irregular in size and shape and are frequently much 

distorted, but when seen in sections made at right angles to the longer 

axis of the projectile are many times arranged in rudely concentric 

bands. In these same sections, also, there are concentric lines or 

cracks produced by a rolling up of the material, or developed by 

weathering. The variations in form from globular to ovoid, and 

more or less irregular, and in internal structure from highly vesicular to compact and stony, with but few irregular and frequently much 

elongated vesicles, appear to be due to variations in .plasticity or 

liquidity of the material at the time it was projected into the air, and 

variations also in the length of its flights. The more plastic the lava 

and the longer its flight, the greater its tendency to assume a spherical form. So far as I am aware, the bombs exhibiting a gradation in 

the size of the vesicles occupying the interior are nearly spherical, 

while the oval or spindle-shaped examples with projecting ends are, 

as a rule at least, compact in the interior and contain relatively few 

and frequently unsymmeirical cavities. The absence of scorise in the 

compact bombs is seemingly accounted for on the assumption that the 

lava was without a high percentage of contained steam or gases, or 

that the liquidity of the material was such that they escaped before 

consolidation was far advanced. There are large quantities of thin, 

nearly flat cakes of compact or but slightly vesicular lava strewn 

about the Cinder Buttes, which will be described below, and which 

were, I suppose, formed by the cooling of liquid lava blown out of the 

volcanoes, after coming to rest. The compact bombs, with more or 

less spiral bands or vesicles in their interior and spiral and curved 

ridges on their surfaces, seem to have originated from masses of viscous lava, similar to those which formed the flat cake, but which 

cooled in the air and, after losing their previously contained steam, 

were rolled together on account of their rotation so as to assume 

more or less football-like shapes.

In this connectidn, however, it should be noted that no forms intermediate between the flat cakes produced apparently by the ejecting 

highly liquid lava and the well-defined globular or ovoid bombs were 

noted. There is, so far as I am aware, an absence of bombs which 

were sufficiently plastic to become conspicuously flattened on striking,
U. S. GEOLOGICAL SURVEY BULLETIN NO. 199 PL. XII

VOLCANIC BOMBS, CINDER BUTTES, IDAHO.
CAKES OF LAVA. 79

although still retaining something of their spherical form, such as 

occur abundantly about the Ice Spring crater in Utah."

'Lava cakes. The thin, flat cakes of compact lava, mentioned above, 

occur in abundance on the side of some of the cones and crater walls 

forming the Cinder Buttes. They may be seen especially on the 

southwest slope of the highest cone, where they occur in thousands. 

These lava cakes, as I term them for lack of a better name, are usually 

composed of compact or but slightly vesicular black lava, but at 

times, they are scoriaceous; although usually flat, they frequently 

have thin inclined ridges or offshoots on their upper surfaces; in 

thickness they vary irregularly from perhaps a fourth to half or, in 

the larger pieces, two-thirds of an inch. Their margins are usually 

broken, but sometimes thin out to a sharp edge. They are of all sizes, 

up to 14 inches or more across. On their under surfaces there are

sometimes adhering fragments of lapilli, and occasionally similar 

fragments are inclosed between projecting ridges, or in the center of 

a mass composed of two or more adhering cakes. These thin lava 

cakes occur in abundance not only on the lapilli cones among the Cinder Buttes but on the adjacent lapilli fields and hills, where no distinct crater can now be seen. Similar cakes were observed, also in 

abundance, around a small and very recent volcanic cone about 10 miles 

north of Bliss, named on a previous page the Blanche crater. Their 

abundance in the instances mentioned indicates that they form no 

inconsiderable part of the fragmental or quasi-fragmental material 

thrown out by volcanoes of a certain type, namely, those which are 

supplied with highly liquid lava. In some instances the splashes of 

lava, after striking the earth, were still sufficiently fluid to flow and 

united one with another so as to form irregular sheets. Compact layers, usually of a reddish color, seen in vertical sections of some of the 

cones of lapilli and scorise were found to have originated in this manner. 

Only the more conspicuous variations exhibited by the fragmental 

material, including bombs, so abundant about the Cinder Buttes have 

been noted, but it would not be difficult to select a series showing a 

complete gradation from angular scoriaceous fragments produced by 

the breaking and ejection of a frothy, brittle crust, formed on the 

surface of the lava within a crater, to the irregular lava cakes resulting 

from, the hardening of material blown out in a liquid condition. Such 

a series would illustrate the fact that the Avide variations presented by 

the material blown from volcanoes depend principally on its degree 

of rigidity or fluidity on leaving the parent crater. The range is from 

brittle scoria to highly fluid lava. The variations in shape assumed 

by lava ejected in a plastic or fluid condition depend on the length of 

its aerial flight and on the manner in which it rotates.

aThese flattened bombs are referred to by G. K. Gilbert, in his monograph on Lake Bonneville, 

Mon. U. S. Geol. Survey, Vol. 1,1890, p. 321.
80 SNAKE RIVER PLAINS OF IDAHO. [BULL. 199.

It may be noted that no foreign or included rocks, such as fragments 

of granite, quartzite, etc., or pebbles.derived from older terranes, 

except a single fragment of obsidian, were observed about the Cinder 

Buttes. The buttes are built entirely of basaltic lava..

PARASITIC CONES.

The eruptions to which the Cinder Buttes are due were characterized in their earlier stages by explosive violence, during which comparatively small cones of lapilli, scoria, bombs, etc., were formed, and 

later by an outpouring of immense volumes of liquid lava. When the 

lava ceased to flow, the portions remaining in the. conduits through 

which it rose cooled and hardened, and the lives of the volcanoes ceased 

without a renewal of the steam explosions which accompanied their 

birth. In one instance, however, there was a partial exception to this 

rule.

About 2 miles northwest of the highest of the Cinder Buttes, and 

on the surface of a bare, corrugated lava stream near where it came 

to the surface, there is a row of seven steep-sided and remarkably regular cones, composed principally of rough ball-like masses of highly 

vesicular or scoriaceous lava (PI. XI, -A). These balls or imperfectty 

formed bombs are usually from 8 to 14 inches in diameter, and when 

they fell were sufficiently plastic to adhere one to another, so as to 

form what at first were nearly vertical walls. The sides of these 

cones near their summits now have slopes of from 50 to 56 degrees, 

but decrease below to 34 degrees or less, owing to the accumulations 

of small quantities of fragmental material about them. Their steep, 

upper slopes are angular and rough, but the lower slopes, when seen 

in profile, present curves such as are characteristic of lapilli cones.

Not only were the spherical masses plastic when they fell, but in one 

observed instance a splash of lava tossed out and falling on the exterior 

of a cone ran down several feet before cooling. In addition to the pasty 

and liquid material ejected, there is a minor quantity of angular fragments, but these were not thrown far, and the surface of the lava 

stream on which the cones stand is entirely bare at a distance of but a 

few score feet from their bases. The cones are symmetrical and the 

distribution of the lapilli about them shows no evidence of a strong 

wind blowing at the time they were formed.

The craters, with one exception, range in height from about 40 to 

60 feet. The exception is furnished by the most westerly in the 

series, which is much lower than its companions and does not rise 

more than 15 feet above the surface of the adjacent portion of the 

lava stream on which it stands. The trend of the line of cones is about 

southeast, or in the same general direction as that of the belt of volcanoes with which they are associated. The cones are located at quite
RUSSELL.] PARASITIC CONES. 81

regular intervals of approximately 70 feet, although in some instances 

the bases of two adjacent cones touch each other. Each of these cones 

is of the nature of a chimney-built about a small vent from which 

steam was issuing with considerable force and throwing out clots of 

plastic and even liquid lava. In most instances the chimney-like 

openings through which steam escaped have been closed by the falling 

in of the summit portions of their walls, but at the west end of the 

series there are two craters still complete and having vertical shafts 

in their interior. The openings referred to are nearly circular in 

horizontal sections and about 30 feet in diameter at the top and 50 to 

60 feet deep; midway down they contract, and expand again below, 

giving to them in vertical section an hour-glass form. In the smaller 

cone at the west end of the series the opening in its most constricted 

part is rudely elliptical, the principal axes measuring about 8 and 12

feet. Its companion is somewhat larger and less regular. The walls 

above the constrictions midway down are nearly vertical and overhang 

their lower portions. On the sides there are adhering clots and splashes 

of lava which ran down before cooling and now occur in part as pendent, 

stalactite-like forms. When seen from above the walls appear smooth, 

but on descending part way and looking up the irregularities due to 

the pendent clots become conspicuous.

At the bottom of- the smaller of the two openings there are two 

chambers or enlargements, looking like the mouths of tunnels, one to 

the northwest, one to the northeast. These openings are about 15 feet 

wide and 10 to 12 feet high. The other open shaft has but one 

expansion at the bottom similar in size to those just mentioned and 

leading toward the northeast. The enlargements in these two instances 

are at about the same depth below the summits of the vertical shafts 

with which they communicate, but owing to the greater height of the 

pile of lava balls, etc., about one opening they are not at the same 

depth below the surface of the lava stream on which the cones stand. 

The chamber at the bottom; of the smaller cone is about 20 or 30 feet 

below that at the bottom of its companion. At the bottom of the shaft 

in the smaller cone at the time of my visit (September 4, 1901) there 

was a conical mass of white ice, about 10 feet thick in its central part 

and about 15 feet in diameter at the base; adjacent to its northern side 

was a pool of clear water. The ice was exposed to the sky, but could 

not be reached \>y the direct rays of the sun even in midsummer. 

Ice and water are also present at the bottom of the large shaft. 

These are about the simplest examples of "ice wells" that can be 

imagined. Clearty the ice is a remnant of the previous winter's snow, 

compacted b\r the freezing of percolating water."

« An instructive account of " ice caves," "ice wells," etc., may be found in a book by Edwin Swift 

Balch, entitled "Glacicres, or Freezing Caverns." Philadelphia, 1900.

Bull. 199 02 6
82 SNAKE EIVEE PLAINS OF IDAHO. [BULL. 199.

The linear arrangement of the scoria cones just described, on the 

otherwise bare surface of a broad lava stream, and the nature of the 

material of which they are composed indicate that they were built 

along a fissure formed in the hardened surface of a lava stream while 

its lower portion was still plastic or liquid. They are thus of the 

nature of parasitic cones formed about steam blowholes, from which 

clots of viscous and splashes of still liquid lava, together with some 

lapilli, were blown out. The shafts of the chimney- like piles formed 

about the openings in the surface of the frozen lava stream were never 

occupied by liquid lava, as their walls are far too weak to sustain such 

a pressure and no streams of lava Avcre given off by them.

LAVA STKEAMS.

Reference has already been made to the wide extent of the lava 

streams which flowed awaj^ from the Cinder Buttes, but it is difficult 

to convey in words an adequate impression of their magnitude, such as 

is derived from traveling over their surfaces or along their margins, 

or from a view from the neighboring mountains.

There are six principal lava flows of recent date Avhich have their 

origin in these buttes, and several more of considerable antiquit}r , the 

sources of which are now more or less indefinite. Comparati vely little 

"old lava," as it may be termed, is exposed about the bases of the 

young volcanoes, except far out on the plain, and some of it may have 

come from other and distant centers of eruption.

The place of origin of each of the six recent lava streams referred 

to is plainly distinguishable, but the best defined of all is the crater 

from Avhich a lava stream that flowed northwestward welled out. This 

is the first fresh'lava met with on leaving the road which skirts the

west border of the Snake Kiver Plains and taking a dim trail leading 

eastAvard among the Cinder Buttes. This northwest floAv came from 

a crater composed of reddish tuff, the portion of Avhich remaining has 

a height of about 200 feet. The lava rose within the tuff crater, 

breached the western side of its encircling wall, and the fragments 

floated aAva}7 on its surface. The top of the congealed lava column in 

the conduit of the volcano is a semicircular plain of rop}7 and scoriaceous basalt 500 feet across, Avhich is continuous with the nearly level 

surface of the great sheet of lava that flowed from it and expanded on 

the plain to the northward. The place of emergence of the lava is 

surrounded on all sides, except Avhere the breach formed by its discharge occurs, by ragged cliffs of reddish tuff. The lava not only 

broke the cone in which it rose, but it tore away the base of the outer 

slope for a distance of fully a mile before expanding on the plain to the 

northward. On each side of the hardened lava stream for about half a 

mile below its source there are precipices, similar to those partially 

inclosing the congealed pool whence it came. The right or eastern
RUSSELL. J LAVA 8TBEAM8. 83

bank of the stream is of reddish tuff and is a part of the parent cone; 

the left bank is composed of large angular blocks of black lava, and is 

due to the subsidence of the central part of the stream, which left its 

border stranded.

One of the most striking, if not the most novel of the man}' interesting features connected with the occurrence just mentioned, is the 

fact that large masses of tuff torn from the crater's walls were floated 

down the lava stream for at least 3 or 4 miles, and carried in large 

numbers far out on the adjacent plain. The floated masses are rough 

crags, frequently measuring from 20 to 60 feet in diameter and rising 

15 to 20 feet above the bare, black, corrugated surface in which they 

are partially embedded. About the base of each of these masses which 

was closely examined there is a depression in the surface of the lava, 

forming a moat-like trough 4 to 6 feet deep. It is plainly evident 

that the masses of loosely compacted lapilli and scoria^ were of less 

specific gravity than the molten lava on Avhich they fell, and therefore* 

floated on its surface. How deep below the surface of the surrounding lava the bases of the crags are sunken is not definitely known, but 

in one instance fissures formed since the lava hardened reveal a downward extension of the tuff to a depth of 10 or 12 feet. That these 

floated masses came from the tuff cone from which the lava stream 

emerged is plainly evident, not only on account of the material composing the masses themselves, which is the same as that of the cone, 

but for the reason that certain of the crags are near their place of 

origin, having boon carried but a few hundred yards, while others 

form a continuous train reaching faraway and expanding to the northward. Not only were masses of relatively light tuff floated away, but 

blocks of compact basalt which fell from the precipitous western bank 

after the central part of the lava stream subsided Avere carried several 

hundred feet on the flow during its later stage, when the molten rock 

had become exceedingly viscous.

Another feature in this connection is of interest. The lava which 

flowed away from the Cinder Buttes was at first highly liquid, as will 

be shown more fully later, and spread widely on the adjacent plain, 

but as the supply lessened the lava thickened, becoming exceedingly 

viscous before it finally ceased to flow. The rate of flow toward the 

end of an eruption was characterized by a slowness as well marked as 

was the rapidity of the current during its earlier stages. The floating 

fragments on the lava, described above, fell upon it late in its liquid 

state, when it had become viscous and was partially submerged, pressing down the stiff plastic material about them in the same way that a 

block of stone would indent the surface of a mass of highly viscous 

pitch or asphaltum. Whether the material that was carried away 

earlier was floated or sank is not known, as the broadly expanded 

distal extremity of the lava stream has not been examined.

Although it frequently appears that lava streams in various regions
84 SNAKE EIVER PLAINS OF IDAHO. [BULL. 199.

have eroded their banks, the instance just cited is the only one that 

has come under my notice where the evidence of such an occurrence 

was conclusive. Evidently a stream of lava in this respect partakes 

of the character of both a river and a glacier. When the lava is liquid 

it erodes like a stream of water, with the added advantage of greater 

specific gravitj'; and when viscous, it floats away rock masses that fall 

on its surface in a manner analogous to the way morainal material is 

carried by a glacier. No evidence was obtained to show that lava 

from the Cinder Buttes melted or changed in any conspicuous way the 

rocks with which it came in contact. Such action may have occurred 

during the earlier stages of the eruption, but does not sesm probable.

The rupturing of cinder cones by outflowing lava is a common feature of the Cinder Buttes, and is well illustrated by an isolated volcano 

which built a complete crater, situated about a mile northeast of their 

highest peak. From this volcano the lava flowed westward in a strong 

'stream, which made a wide breach in the wall of the crater from which 

it came, leaving the remainder intact. The lava descended a steep 

slope before reaching the plain, and is now covered with soil and vegetation. In this instance, as in so many others near at hand, it is evident that the eruption was at first violent and characterized by steam 

explosions which threw out lapilli and scoria, but did not give origin 

to a lava stream; later, Avhen a perfect cone with a deep crater in its 

summit had been formed, lava rose from the conduit within, bleached 

the crater's walls, and flowed quietty away without a renewal of the 

explosive eruptions. This isolated cone with a single lava flow 

extending from it and expanding on the plain recalls forcibly some 

of the illustrations contained in Scrope's" classical book on the extinct 

volcanoes of central France.

At the locality where the northwest lava stream came to the surface there is an amphitheater, with rough walls, embracing a generally 

flat but undulating and corrugated area about 200 yards across, floored 

with scoriaceous and ropy lava, which looks not unlike, a great spring 

suddenly congealed. The evidence of flow and of viscosity in the 

now hard material is everywhere conspicuous. The surface is entirely 

bare of vegetation and without lapilli or other deposits. It is apparent at a glance that this is the hardened surface of the conduit from 

which the lava stream leading from it was poured forth. One is 

impressed with the smallness of the source in comparison with the 

vast volume of material that came from it. The lava stream at first 

went westward, then, curving, took a northern course about the base of 

the portion of its crater still remaining, and at a distance of a mile is 

about 500 yards wide; it continued to expand and reached a distance, 

by estimate, of 6 or 8 miles, and has a width in its expanded distal 

extremity of some 4 or 5 miles. These are rough estimates and are

aThe Geology of the Extinct Volcanoes of Central France, by 0. P. Scrope. London, 1858,
RUSSELL.] LAVA STEEAMS. 85

probably below rather than above what an actual survey would show. 

The area covered by the lava stream is not less than 20 square miles, 

and may be twice that amount.

The absence of angular f ragmental material and of volcanic bombs, 

clots of lava, etc., on the surface of the congealed lava pool, other than 

fragments near the borders which have fallen from its inclosing walls, 

is evidence that the later stages of the eruption were not attended by 

explosions. The lava seems to have been poured out quietly and in 

immense volume, in much the same manner that a spring of water sometimes comes to the surface and flows down a gently inclined channel. 

This is more than a casual simile, for the lava during the earlier stages 

of the eruption was certainly highly liquid, and was in reality a spring 

of molten rock which was caused to flow, as we have reason for believing, 

by pressure on a reservoir deep below the surface, which thus formed 

a stream that flowed far and spread wide on a nearly level surface.

The outwelling of the molten rock was so quiet that not only were no 

volcanic bombs projected into the air, but no pasty clots or drops of 

liquid lava were spattered onto the bordering walls.

The surface of the lava at the immediate summit of the material filling the conduit is vesicular, and in part highly scoriaceous, but there 

is nothing approaching pumice or congealed frost to be seen. In fact, 

but little material of that nature was observed about the Cinder 

Buttes. The steam which rose with the lava seems to have escaped 

quietly before the magma became sufficiently cooled and stiffened to 

retain it until its pent-up energy resulted in explosions. That steam 

or gases were present in considerable quantity, however, is evident 

from the fact that nearly all the lava in sight is more or less vesicular 

and in many instances highly scoriaceous.

The northwest lava stream, and the same is in general true of all 

the recent lava flows about the Cinder Buttes, came to rest and finally 

hardened with such a low surface slope that from a little distance no 

eye can distinguish it from a perfect plain. For the first mile or so 

below the fountain-like source from which it came there is, it is true, 

a perceptible northward slope, but it is so gentle that a casual observer 

would scarcely note its presence.

But a few rods south of the congealed lava pool just described and 

separated from it by a fragment of a tuff cone, a pc..tion of which was 

undermined by the lava flowing past its base and broken away after 

the manner of a landslide, another and larger lava stream carne to the 

surface and flowed southward. This southwest lava flow had its source 

in two lava pools, but the molten rock discharged by them soon united 

so as to form one stream, which, at a distance of perhaps a mile, was 

joined by another and still larger river of lava having its source about 

a mile to the west of the base of the highest of the Cinder Buttes, and 

the united flow continued southward for a distance of between 25 and
86 SNAKE EIVEK PLAINS OF IDAHO. [BULL. 199.

30 miles/' The descent of the surface of the lava in this distance is 

about 1,000 feet, more than one-half of which is, I judge, within the 

first 10 miles. In the portion nearest the Cinder Buttes the descent 

of the surface toward the south can be detected by the eye, but beyond 

a distance of about 10 miles, the rough lava sheet seems to be level. 

The fact that the lava flowed so far on such a gentle gradient shows 

that it was highly fluid and spread almost with the freedom of water. 

The sheet produced must, in consequence, be thin, unless depressions 

were present in the surface of the plain over which it spread itself. 

All these features are such as pertain to yet other lava streams about 

the Cinder Buttes, as well as to the older lava sheets beneath the Snake 

River Plains, exposed in part in section in the walls of Snake River 

Canyon.

In addition to the lava streams briefly described above, there is 

another irnmediatel^v at the west base of the highest of the Cinder 

Buttes, which went southward, and is somewhat older than the neighboring stream on the west. Two other streams, differing in age, went 

northward from near the same portion of the belt of craters. One of 

these is comparable in extent and volume with the lava sheet which 

flowed southward. There are thus at least six recent lava flows about 

the Cinder Buttes which spread widely on the adjacent plain and in 

fact nearty surround the most prominent portion of that belt of Volc.inoes. Other lava flows from craters farther eastward were seen, but 

all of them are apparently older than those just noted, although in 

certain instances they are sufficiently fresh to be easily traced to the 

craters from which thej^ emerged.

The area occupied by the recent lava forming the six flows described 

above is by estimate between 250 and 300 square miles. There is no 

ready means of accurately measuring the thickness of these sheets, but 

the}^ are certainly comparatively thin, as is apparent from the fact that 

they spread widely on a nearly level plain and cooled with essentially 

flat surfaces. Judging from the thickness of the various sheets at their 

margins and the gradients of their surfaces, their average thickness 

seems to be between 50 and 100 feet, or approximately 75 feet. On 

this basis the volume of lava they contain is between 7 and 8 billion 

cubic feet.

In reference to certain general hypotheses concerning the origin of 

volcanoes, the static equilibrium of the earth, etc., it is of interest to 

note that the lava poured out by the volcanoes which formed the Cinder Buttes was forced up to a horizon about 6,000 feet above the sea,

"While my observations show that the northwest and southwest flows, starting from within a distance of a few rods of each other, were contemporaneous and united with each other, the place of 

junction of the southwest flow with the next lava stream to the east has not been examined, and 

from what source the vast lava sheet to the south of Cinder Buttes was mainly derived is not known. 

Seemingly the southwest flow, and the next one to the east, are of the same age, and unite to form 

one sheet OH the plain to the south.
RUSSELL.] COMPOSITION OF THE LAVA. 87

and at a locality far distant not only from the ocean but frorn all surface-water borders, and in. a region where erosion and deposition practically counterbalance each other.

CHEMICAL COMPOSITION.

A characteristic sample of the lava from near the source of the 

stream that flowed northwest from the Cinder Buttes that is, the one 

nearest the mountains on the northern side of the range of craters 

has been analyzed with the following results:

Analysis of recent lava from the Cinder Buttes, Idaho.

[Analyst, W. F. Hillebrund.]

Per cent.

Silica, SiOj.............................................................. 51.14

Titanium dioxide, Ti02 .................................................. 2.41

Zirconium dioxide, Zi(',................................................. 0.12

Alumina, A12O3 ......................................................... 13, 05

Chromic oxide, Crj03 .................................................... None.

Vanadium trioxide, V2 0;( ................................................ Trace.

Ferric oxide, Fe2 03 ...................................................... 2.15

Ferrous oxide, FeO...................................................... 12. 97

Manganous oxide, MnO.......................................... ........ 0. 44

Nickelous oxide, NiO .................................................... Trace.

Calcium oxide, CaO ..................................................... 6. 56

Strontium oxide, SrO............................................... Faint trace.

Barium oxide, BaO....................................................... 0. 25

Magnesium oxide, MgO.................................................. 2. 21

Potassium oxide, K2 0 .............. .................................... 2. 33

Sodium oxide, Na2 0..................................................... 3. 59

Lithium oxide, Li 2 0 ..................................................... None.

Water below 105° C, H2 0 ................................................ 0.12

Water above 105° C, H,0 ................................................ 0. 22

Phosphoric oxide, P2 05 .....:............................................ 1. 59

Carbon dioxide, C02 ..................................................... None.

Chlorine, Cl ............................................................ Trace.

Fluorine, Fl ............................................................ 0.10

Iron disulphide, FeS, (S=O.OS) .......................................... 0.15

100.30 

Less oxygen computed in place of fluorine ................................ .04

Total............................................................. 100. 26

Specific gravity=2.907 at 24° C.

This analysis shows the composition of a large lava flow as nearly 

as a single well-selected sample can be expected to indicate the average 

of a seemingly homogeneous terrane, and probably indicates also about 

the average composition of all the recent lava discharged from the 

Cinder Buttes. It was made with much detail, with the view not only 

of meeting present needs but of furnishing accurate data for use in 

future discussions of volcanic phenomena.
88 SNAKE RIVER PLAINS OF IDAHO. . [BULL. 199.

The rock analyzed, as is shown by its composition and also by its 

physical and mineralogical characteristics, is a typical basalt, with 

perhaps a slightly higher percentage of silica than is normal to such 

rocks. The ratio of acids and bases present, as I am assured by Prof. 

E. D. Campbell, of the University of Michigan, an expert metallurgist, is such as to favor easy fusibility. From analogy with the composition and behavior of the slag produced in iron smelting furnaces, 

the fusing points of which are known, the rock would probably melt 

at about 2,250° F., and yield a highly liquid product, which on 

cooling would pass slowly from a liquid to a solid state through an 

intermediate highly viscous condition. This opinion was expressed by 

Professor Campbell without a knowledge of the physical characteristics of the lava, and serves to increase my confidence in the deductions made from field observations in reference to the highly liquid 

condition of the lava when extruded and its slow passage through an 

intensely viscous condition before final consolidation. The gradual 

change from a plastic to a rigid state was no doubt prolonged, owing 

to the slow rate of cooling incident to a large mass of fused material, 

but this is not of necessity the sole cause. In this connection it may 

be suggested that the ready fusibility of a lava is not entirely dependent on the presence of a high percentage of basic material, as is commonly stated, a basic lava usually being considered easily fusible and 

an acid lava (one rich in silica) refractoiy; neither does the behavior 

of a rock in this respect depend necessarily on the fusibilit}7 of the 

individual mineral present, as claimed b}^ J. D. Dana, but rather on the 

ratio of the constituent acids and bases. With lavas, as with furnace 

slags, an excess of either acid or basic material might produce difficult 

fusibility, while an intermediate condition in which the acids and bases 

were adjusted to one another in certain definite ratios would produce

an easily fusible compound. In the case of furnace slags, as I am 

informed by Professor Campbell, the time required for the passage 

from a liquid to a solid condition, or the time required for the material 

to "set," is regulated not only by the rate at which heat is lost, but 

by chemical composition. Slags rich in silica pass from a liquid to a 

solid state, or set much more quickly than basic slags, the conditions 

favoring the escape of heat being the same. Applying this principle 

to molten lavas we would expect highly acid lavas to congeal more 

quickly than basic lavas, even though their temperatures at the time 

of extrusion and other conditions were the same. As is well known, 

this agrees with what is found in nature, since streams of acid lavas 

have frequently come to rest and terminated with precipitous frontal 

slopes on steep gradients, which has not been observed in the case of 

basic lava. To be sure, this is not a crucial test, since the acid lavas 

in general require a greater degree of heat to cause fusion than the 

more basic varieties, and on reaching the surface may not have been
RUSSELL.] . SURFACE FEATURES AROUND CINDER "SUITES. 89

liquid, but only viscous, and indeed in some observed instances nearly 

solid. The quicker setting of siliceous than of basic slags suggests 

also a reason why the surfaces of acid lavas are so frequently broken 

and consist of masses of angular fragments, without the smooth, oval, 

and flowing forms that basic lava frequently presents.

SURFACE FEATURES.

All of the recent lava streams about the Cinder Buttes, as previously 

stated, are similar in their general characteristics, but when examined 

in detail they present interesting variations in surface features, not 

only in individual streams, but in different portions of the same 

stream.

In general, the lava at a distance of from 5 to 10 or more miles from 

its place of emergence is less vesicular than at the summits of the 

conduits from which it came. The reason for this is, evidently, that

the steam occluded in the molten rock had greater facility to escape 

when the lava flowed far than when its journey was short. More 

than this, the lava first extruded from a ve$t and now found at the 

distal extremity of the stream it formed flowed much more rapidly 

than that which came later, either because of a higher temperature 

and consequently greater liquidity, or by reason of larger volume. 

To these two alternatives a third may be postulated, namely, a variation in the composition of the lava, which caused it to become viscous 

near the close of the discharge without a diminution of temperature. 

While analyses of the lava that flowed far have not been made, the 

physical appearance of the distal and proximal extremities of the 

streams do not suggest a difference in composition, and this third 

alternative can seemingly be disregarded. Between the remaining 

hypotheses there is an easy choice, namely, that the rate of flow of 

the lava diminished without a decrease in the initial temperature. 

This is evident, since if the rate of flow had remained essentially the 

same from the beginning to the close of a discharge, and the lava had 

become viscous toward the end of an eruption, it would have acquired 

a corresponding increase in depth near its source, and if as viscous as 

the lava now remaining at the summits of the conduits was before 

hardening, it would have been piled high above the opening from 

which it was extruded. On the contrary, we find but a slight increase 

in surface gradient on ascending any one of the lava streams near its 

source. All the evidence indicates that the volume of the lava toward 

the close of an eruption gradually diminished until the outflow ceased. 

The last lava to reach the surface cooled and hardened without lateral 

motion.

These considerations have a bearing on the theories of the causes of 

volcanic eruptions. Of these there are two that have claimed special 

attention. One is, in brief, that steam is the main motive power
90 SNAKE RIVER PLAINS OF IDAHO. [BULL. 199.

which causes lava to rise, and the other that the. .lava is forced to the 

surface by pressure on the reservoirs from which it is derived. In 

the lava streams among the Cinder Buttes, there is no evidence of a 

diminution in the amount of steam occluded in the molten rock 

toward the end of an eruption, but rather the reverse, if account is not 

taken of the greater freedom of its escape from lava that flowed far 

as compared with that which cooled without motion, the lava at the 

immediate source of a stream being, as alread}r stated, in all cases 

highly vesicular, and in part even highly scoriaceous. There is thus 

no reason for assuming a decrease in steam tension within the lava 

itself. On the other hand, the hypothesis that there was a gradual 

diminution in the pressure on the lava still remaining below the surface meets all the requirements of the facts observed. There still 

remains another alternative, namely, that the supply of material in a 

condition to be extruded gradually diminished. This condition need 

not be considered at this time, however, as it does not seem to have a 

bearing on one's choice between the steam and pressure hypotheses. 

The facts now to be observed indicate that the decrease in the rate of 

flow was due to decrease in volume, and that the more slowly moving 

material retained its steam and gases so as to become highly vesicular, 

while that which flowed far congealed to a more compact rock.

On the rate of flow, or, more definitely, on the ratio of rate of flow 

to rate of surface cooling, depend certain marked contrasts in the 

resultant surface features. When motion was slow and continued 

after the lava had become viscous, the stiffened crust was left with 

either a generally smooth, flat surface, or acquired oval, stream-like 

ridges, bulging mounds and dome-like swells, while the crust formed 

where motion was more rapid or had continued after the surface had 

passed to a rigid condition became broken and the blocks were variously 

displaced and heaped up so as to produce excessive roughness. These 

two leading varieties of surface features correspond with what Dana ft 

has termed pahoehoe and aa in the case of the lavas of the Hawaiian 

Islands. His description of what may be termed the generic characteristics of these two strongly contrasted lava surfaces is as follows:

Lava streams are of two kinds. (1) There is the ordinary smooth-surfaced lava 

of volcanoes. It is the pahoehoe o.f Hawaii, the term signifying "having a satinlike aspect." The surface of the lava shows, by the fine and coarse flow lines over 

it, that it cooled as it flowed. Through one means and another the surface is usually 

uneven, being often wrinkled, twisted, ropy, billowy, hnmmocky, knobbed, and 

often much fractured. *' * * The streams have sometimes a firm, glassy exterior 

half an inch or less in thickness. When lava overflows from a boiling lava lake it 

carries along a surface scum 1 to 3 or 4 inches thick, which is a glassy scoria, usually easily separable from the more solid and chief part of the lava stream.

The crusting over of a stream while it is still flowing, owing to contact with the 

air above, results in the leaving of empty tunnel-like caverns, which are sometimes 

hung with stalactites.

«J. D. Dana, Characteristics of Volcanoes. New York, 1390, p. 9.
U. S. GEOLOGICAL SURVEY BULLETIN NO. 199 PL. XIII

(A)

BLISTERED LAVA SURFACE AND CORRUGATIONS ON LAVA STREAM, CINDER BUTTES,

IDAHO.
KDSSELL.] PAHOEHOE. 91

(2) The other most prominent kind of lava stream is the aa. The aa streams 

have no upper flow-like surface; they are beds of broken-up lava, the breaking of 

which occurred during the flow. They consist of detached masses of irregular 

shapes, confusedly piled together to a height sometimes of 25 to 40 feet above the 

general surface. The size of the masses is from an inch in diameter to 10 feet and 

more. The lava is compact, usually less vesiculated than the pahoehoe, not scoriaceous; but exteriorly it is roughly cavernous, horridly jagged, with projections often 

a foot or more long that are bristled all over with points and angles. In some cases 

ragged spaces extend along planes through the large masses, like those of the exterior; but in these, as in other parts, it is evident that the agency was tearing and 

upploughing and cavity making in its action, and not vesiculating.

Palioelioe. The lava surface having the characteristics included 

under the term pahoehoe occurs especially near the sources of the 

lava streams, and in some instances continue for several miles down 

their courses, and in certain cases are not entirely absent even at their 

distal extremities. The leading1 features are broad, generally smooth 

swells and stream-like ridges with convex surfaces, which cross each 

other as if braided together, but begin and end indefinitely. Some 

one has compared the appearance of such confluent outflows of lava to 

a mass of giant slugs, crawling over each other. The simile is certainly suggestive. Slow motion of many, generally parallel, but occasionally diagonal and recrossing streams, from 2 or 3 to 10 or 15 feet 

in width, united into a single generally flat sheet, with perfect preservation of form in their central parts, convey some idea of the general appearance of much of the pahoehoe about the Cinder Buttes.

The origin of the peculiar and highly characteristic pahoehoe surface 

is due to the flow of viscous lava, which in consistency resembled 

asphaltum or pitch. The onward motion was not a continuous flow, 

as in the case of thorough^ liquid substance, but the surface and front 

of the advancing stream stiffened and bulged upward, and the more 

thoroughly molten material within broke through the tenacious but 

still plastic surface portion and advanced as a well-defined stream for 

perhaps a few yards or rods, and in turn stiffened at the surface and 

expanded on account of pressure from within and halted with a curved 

front bulging outward. These slow-moving, viscous streams crossed 

one' another, but became more or less thoroughly intermingled. This 

manner of progression, accompanied by many variations in detail, 

can be plainly seen on the congealed surfaces now remaining, espcciallx^ 

near the sources of the lava stream.

While the curved and swelling forms so characteristic of pahoehoe 

surfaces are apparently smooth when seen from a distance of a few 

rods or a few yards, they are rough to the tread, and on close examination are found to be braided over with low ridges and string-like forms 

inclosing or bordering shallow depressions, as is well shown on PI. 

XIII, A. The origin of this coarse lace work on the surface of lava 

which cooled slowly, becoming highly vesicular before its sluggish
92 SNAKE EIVEE PLAINS OF IDAHO. [BULL. 199.

motion finally ceased, is easily explained. Where the lava cooled 

without motion, the vesicles once occupied b}7 streams are spherical or 

nearly so. Where the lava cooled and stiffened while still slowly flowing, the vesicles are elongated. In such instances one may frequently 

find cavities which were drawn out until the wall at the top became 

exceedingly thin and was finally ruptured, the material that formed 

it spreading and leaving an elliptical blister-like depression. Much of 

the lava with extended cavities has the appearance of molasses candy 

that has been pulled until it became fibrous. When motion continued 

after many of the vesicles at the surface of the lava had become 

ruptured, the material forming the elevated boundaries of the numerous blisters was extended into long, sinuous ridges, and the surfaces 

assumed the appearance shown in the photograph referred to. This 

process took place not only at the surface, but at intervals within 

the mass, as the lower part continued to flow after the surface had 

stiffened and ceased to move; or what seems to have been frequent^ 

the case, successive layers, each a few inches thick, acquired different 

rates of motion, increasing with depth, owing to increase in plasticity, 

so that the surface portion of a sheet became more or less completely 

fibrous throughout a thickness of several feet.

Corrugations and arclies. The wrinkling of the surface of a lava 

stream after it became stiff and viscous, owing to the flow of the more 

plastic material beneath in the manner well known in the case of many 

recent lava streams, is abundantly illustrated about the Cinder Buttes, 

where several novel variations of the process were observed.

The simplest corrugations occur on nearly flat or bulging pahoehoe 

surfaces, and appear as a series of concentric ridges an inch or two 

high, with a flat space perhaps 3 inches wide between them. The 

corrugations number possibly 10 and'possibly 50 individuals. They 

are drawn out into the form of half an ellipse, or appear as a concentric series of parabolic ridges, which are highest and best defined 

at the front, where the curvature is sharpest, and which fade at the rear, 

where the figure is open. These series of ridges are sometimes 10 or 

20 feet in length, are sometimes gently curved, but more frequently 

are long drawn out and reveal the course of a narrow, sluggish stream. 

Where the motion was greater the spaces between the ridges became 

narrower and curved downward, forming small troughs or synclines. 

Frequentl}7 the ridges adjoin one another, and are even tightly compressed and inclined in the direction of flow of the plastic material 

beneath, as is illustrated by the photograph reproduced in PL XIII, B 

and G. That a flowing motion occurred in nearly solid lava which was 

yet capable of yielding to a strong force slowly applied is show7 n by the 

fact that in some instances the surfaces of the various laj^ers distinguishable in the folds are smooth and polished, having, in fact, the color and 

appearance of highly burnished blue steel. This polish implies that
U. S. GEOLOGICAL SURVEY 1ULLETIN NO. 199 PL. XIV

A. LAVA EXPANDED BY STEAM ON ENTERING WATER. 

B. PRESSURE FOLDS. SURFACE OF RECENT LAVA FLOW, CINDER BUTTES, IDAHO.
BDSSBLL.J CORRUGATIONS AND AECHES. 93

the lava was nearly solid at the time the motion producing the folds 

took place.

Not only simple but compound ridges were frequently formed in 

the manner just stated. In the case of the compound ridges it is 

apparent that a congealing of the surface, accompanied b}r the formation of a series of small wrinkles, was followed by the stiffening of a 

thicker kyer as cooling progressed. This thicker sheet in turn became wrinkled, the larger folds carrying on their surface the smaller 

wrinkles, similar to the occurrence of small waves on the surface of 

a larger one. In these instances, also, the larger folds are frequently 

inclined forward. Still other complexities occur, as when after a 

series of simple or compound wrinkles had been formed the direction 

of the underflow changed and a new series of wrinkles and folds was 

produced which cross the earlier series diagonally.

The corrugated like the adjacent unwrinkled portions of the pahoehoe surfaces are blistered, as explained above, by the breaking of the 

thin surfaces of steam cavities, and cord-like ridges produced by the 

elongation of the material between the shallow depressions. In such 

instances the ridges between the blisters were still more elongated and 

frequently pass from side to side over the curved crest of a fold, producing elevations that suggest the appearance of the thread on a screw. 

The ridges are parallel, however, and notPspiral.

Selecting other examples to illustrate the series, we find that many 

folds rise sharply from the general surface to a height of 10 to 20 or 

more inches. In these instances the sides of an individual fold are 

compressed, while the top may be expanded, so as to reveal in cross 

section much the appearance of the end of a rail road, rail, as is shown 

in PI. XIV.' At times each member of a series of ridges of this nature 

is inclined forward in the direction of flow. The expansion of the 

summit portion of a fold of the nature just referred to is the first in 

a series of changes that produced surprising results. The next variation is where the stiffened crown of a fold has separated from the 

more plastic material in its inner portion and been torn away from it, 

leaving a hollow space, as is shown on PI. XIV. The expanded summits of such ridges are long, hollow tubes. A still greater movement 

resulted in the formation of larger folds, in which the hollows are 6 to 

10 inches or more in height and 3 to perhaps 5 inches across, as is 

shown on PI. XIV, B. The inner surfaces of these hollow folds present the appearance produced when a high viscous substance is pulled 

asunder, as, for example, when a loaf of bread not completely baked is 

broken apart. In these instances the inner walls of the cavities are 

exceedingly rough, presenting numerous sharp ridges and projecting 

points, and are frequently crossed by rods and filaments of brittle 

lava, Avhich are small in the center where most elongated and expand 

where they merge with the walls. This appearance is imperfect!}'
94 SNAKE EIVER PLAINS OF IDAHO. [BULL. 199.

shown in the illustration just referred to. All the forms mentioned 

above, from simple corrugations or ropy forms, as they are frequently 

termed, up to hollow folds 20 or more inches high, occur in abundance, 

especially near the sources of the lava streams. It needs no argument 

to convince the visitor to the Cinder Buttes that various forms wore 

produced by the subsurface flow of the lava, which caused its highty 

viscous surface to become corrugated and folded. The most interesting fact is the tearing away of the nearly rigid crust from the more 

viscous portion below and its upward bending into hollow folds. In 

all these instances the direction of the force acting on the stiffened 

but still yielding crust was horizontal and slowly applied. Variations 

in the results dependent on the degree of rigidity of the crust, its 

thickness, the rate of motion, etc., are numerous.

In all of the examples thus far referred to the crust was only 1 or 2, 

or perhaps 3 inches thick and still plastic and yielding to a slowly 

acting force. Instances are also numerous where the crust was 2 or 3 

feet thick, but still not brittle, and was pressed up into folds that are 

0 to 10 feet high and perhaps 15 or 20 feet across at the base. Ridges 

of this nature form a characteristic feature of the topography of the 

lava surfaces, and frequently have caverns beneath them through which 

a person can walk with freedom. The sides and roofs of the caverns 

are exceedingly rough and frequently bear evidence that the lava was 

still sufficiently mobile to flow after they were formed. The roofs in 

many instances are fretted with stalactite-like pendents of congealed 

lava. The sharpness of the projections is sometimes blunted by the 

subsequent flow of the lava and its gathering into more or less distinct drops. In one instance I found the floor of such a cavern to be 

corrugated for a distance of 20 feet or more, showing that there had 

been a flow of the lava along it. This occurrence suggests that corrugation in the case of old lava flows is not a positive indication that such 

markings belong to the actual surface.

The ridges and domes just referred to sometimes have cracks along 

their summits parallel with their larger axes, which it Avill be remembered are transverse to the direction of the force that produced them. 

In some instances the sides of such a ridge slope sharply, like thereof 

of a house, and there is a break on each margin where the descending 

slope meets the adjacent flat or nearly flat surface. In these cases it 

is evident that the crust had become too rigid to yield to the tangential 

pressure applied to it Avithout breaking, and fracture and displacement resulted. The lower surfaces of these inclined blocks present 

the characteristic "pulled dough" forms referred to in the case of the 

hollow folds, showing that owing to lateral pressure the rigid crust 

had been forced or pulled away from the more viscous material 

beneath.

Openings in lava similar to those just described are mentioned by
U. S. GEOLOGICAL SURVEY BULLETIN NO. 199 PL. XV

PRESSURE KlDGE IN SNAKE RIVER LAVA NEAR MARKET LAKE CRATERS, IDAHO,

PRESSURE RIDGES IN SNAKE RIVER LAVA NEAR BIG BUTTE, IDAHO.
HUSSEM..] CORRUGATIONS AND ARCHES. 95

J. D. Dana as occurring in the lava flows of the Hawaiian Islands, 

and the explanation is suggested that they are due to the force of steam 

or gases generated beneath a still plastic crust. This explanation is 

not favored in the instances observed about the Cinder Buttes, although 

it might secmingty apply to the larger hollow ridges or elongated 

domes if they did not form part of a series. The transition from 

simple corrugations to those having cavities in them, and from these 

to arches with caves beneath, is complete, and includes also the ridges 

with sloping roofs Avhich have cracks along the top. The generation 

of steam or gases beneath a crust can not be accepted as explaining 

the origin of either the earlier or later members of the series and is o

unnecessary for explaining the origin of the intermediate forms. 

That steam may cause arches to rise in the manner referred to by 

Dana may be true, but it does not seem to have been the cause of the

arching seen in the lava streams about the Cinder Buttes.

The ridges with caves beneath, as stated, are frequently from 15 to 

20 feet across and rise from 5 to 10 feet above the bordering surfaces; 

their arched roofs are between 1 and 2 feet thick. Still larger swells 

on the surface of the pahoehoe lava were observed, but as they were 

unbroken, it was not evident that openings occur beneath them, and 

it is possible they arc hardened streams of lava instead of pressure 

ridges.

It is but a step from the larger ridges on the fresh lava streams, 

just described, to similar but frequently much larger ridges, which 

form a characteristic feature of many portions of the older sheets of 

Snake River lava. The forms referred to are dome-like ridges, commonly from 10 to 30 feet high, 20 to 70 feet wide, and from 50 to pos- 

 sibly 500 feet long, which are usually cracked open at the top throughout their length, the cracks being open fissures, usually 3 to 4 feet wide, 

but sometimes as much as 10 feet (PL XV). The fissures referred 

to narrow downward, and the basalt forming their Avails is frequently 

columnar, the columns being at right angles to the outer surfaces of 

the ridges. Where these "cracked ridges," as I have termed them in 

my notes, are in groups, as is frequently the case, their longer axes are 

nearly parallel, but this is not an invariable rule. In some instances 

the sides of the ridges, instead of forming an arch in cross section, 

as is commonly the case, present flat slopes like the roof of a house, 

Avith an open fissure along the top. The steeply inclined sides of these 

A-shaped ridges frequently carry well-defined corrugations, Avhich A\Tere 

formed Avhen the surface of the cooling lava Avas horizontal.

The similarity between the large ridges on the surfaces of the older 

sheets of the Snake River lava and the hollow folds, corrugations, 

etc., observed at the Cinder Buttes, leaves no room for doubting that
96 SNAKE EIVER PLAINS OF IDAHO. [BULL. 199.

the former, like the latter, were produced by lateral pressure in the 

surface portion of a lava flow. The ridges on the old flows are large 

because they were formed in lava that had flowed far over a nearly 

level plain, and had formed thick crusts before they were forced up 

into ridges. As is shown by the small corrugations, hollow ridges, 

etc., on the surface of the recent lava flows, there is a direct relation 

between the thickness of the stiffened crust that forms as lava cools 

and the size of the arches that may be produced in it by lateral pressure. In the case of the old lava flows referred to the crust had become 

 10 feet or more thick before the arching occurred, and correspondingly broad ridges were produced. When the lava at the surface was 

still sufficiently yielding to be stretched by a force slowly applied, it 

was not ruptured, but by far the greater number of the large ridges 

are cracked, showing that the surface had become too rigid to yield 

by stretching to the force applied. The extreme case, where the crust 

had become solid, is illustrated by the flat-sided or roof-like ridges.

The large ridges and dome-shaped elevations on the surface of the 

older sheets of the Snake River lava have attracted the attention of 

previous observers. They are referred to as follows by "F. H. Bradley: a " Whatever the source [referring to the lava of the Snake River 

Plains], the material had evidently become quite viscid; for, at some 

points, where it ran over small inequalities of the surface beneath, it 

now stands in low mounds, which could not have been the case if it 

had been very fluid. That these mounds were not all formed by an 

undermining and sinking of the surrounding masses, to which some of 

them have very properly been referred, is proven by the tapering 

shapes of the closely fitting blocks which form the arch. But there 

is still room, for study on all these points."

That the explanation suggested in the above quotation is not admissible, at least in a large proportion, and, I believe, in all the instances 

observed by me, will appear, I think, from the comparison with the 

more recent forms of a similar nature presented above. Moreover, 

characteristic domes and ''cracked ridges" occur near Shoshone Falls, 

etc., on the immediate border of Snake River Canyon, where the lava 

is from 500 to 700 feet thick. In the walls of the canyon, as already 

stated, sections of the ridges are exposed, which show that they are 

either hollow arches above flat lava sheets, or else the folds die out 

gradually below. No clearer evidence could be presented to show 

that they were not produced by viscid lava being drawn over eminences, even if such an occurrence was known to be possible.

In the production of wrinkles, corrugations, hollow ridges, etc., as 

just described, we have examples of the changes produced in a stillyielding crust under the influence of a force slowly applied, arising

a Sixth Ann. Kept. U. S. Geol. and Geog. Surv. Terr.. Washington, 1873, pp. 20-1-205.
RUSSELL.] AA. 97

from the flow of the subcrustal lava. Cases where the crust became 

fractured have also been cited. All this implies slow cooling and a 

gradual passage of the lava from a fluid through a viscid to a solid 

state, accompanied by a gentle flowing motion in the more slowly 

cooled subsurface portions of the lava streams. Should the crust congeal rapidly so as to form a thin or comparatively thin rigid sheet, 

while motion still continues, it is evident that it would become fractured and the blocks thus formed variously displaced; that is, an aa 

surface would be produced.

Aa. The presence on the Martin lava stream of angular blocks of 

basalt frequently united into a coarse breccia has already been mentioned. In that instance an example is furnished of a lava stream 

having swift motion, owing to a high gradient. A similar occurrence 

throughout areas of many square miles, where the surface is generally 

level, may be seen over the lava streams which flowed away from the 

Cinder Buttes, and especially in the middle portions of their course. 

The areas here referred to have the characteristics included by Dana 

under the term aa.

On the great lava flood which spread northward from near the 

northern base of the highest of the Cinder Buttes, but not from the 

volcano which built that eminence, the breaking of the surface begins 

within less than a mile of its source, and continues broadening to the 

northward as far as the eye can reach from the most commanding of 

the neighboring elevations. The surface of this stream is a chaos of 

angular blocks of scoriaceous lava, which at times are heaped in piles 

10 to 15 or more feet in height. In many instances large cakes of 

lava stand on edge, and are prominent landmarks from afar. The 

blocks of lava sometimes have wrinkled and corrugated surfaces, 

showing that they existed as pahoehoe before they were broken and 

displaced. In some places, in the midst of a broad area composed of 

fragments, there will be a small tract, usually depressed below the 

level of the general surface, which is smooth and unbroken and presents 

the features due to motion while yet plastic.

The general explanation of the origin of the aa surfaces, as is well 

known, is that a hard crust was formed on the lava while yet in motion, 

and that the friction of the still liquid portion beneath caused the crust 

to break. The fragments, being in most cases vesicular, were lighter 

than the liquid lava and were carried along by it. The analogy between 

such a lava stream and a river covered with cakes of ice is very close. 

In the case of a gently flowing lava stream, like a broad river covered 

with cakes of ice, the floated lava blocks are generally horizontal and 

only occasionally turned on edge. When the flow is stronger, as when 

the gradient down which the lava progresses is moderately steep, the 

lava cakes become heaped together and great confusion results. In 

such instances the piled-up lava blocks resemble an ice jam or an ice 

Bull. 199 02 7
98 SNAKE EIVEE PLAINS OF IDAHO. [BULL. 199.

pack on arctic seas. The congealing of a lava stream when covered 

with floating blocks of its own disruptured crust is similar to the 

refreezing of a river on which there are ice flows and ice jams. The 

submerged -portions of the lava blocks are thus united by the hardening of the liquid or plastic lava in which they are immersed, and a 

breccia is formed. This second crust, however, is sometimes ruptured 

and the fragments of breccia are displaced and tossed about.

The fact that in the production of an aa surface a hard crust is first 

formed, which is ruptured owing to the flow of still liquid lava beneath 

it, is again indicated by striations or grooves on the under surface of 

the crust fragments. These markings are frequently several feet long, 

have a width of several inches, and are usuall}7 straight. At first 

glance they resemble glacial scorings, but there is no polishing. The 

origin of these grooves can be traced to hard fragments carried by the 

underflow and pressing against the still plastic lower surface of the floating crust. At times a ragged kernel or fragment of rock is found at 

the end of a groove, showing that at last its motion was arrested and it 

stuck fast.

As already suggested, whether a pahoehoe or an aa surface will be 

produced on a lava stream is determined by the ratio between rate 

of cooling and the rate of motion. But this ratio is not the same for 

different lavas. When a lava sheet cools without motion, neither a 

characteristic pahoehoe nor an aa surface is produced. Many of the 

older sheets of Snake River lava illustrate this; they are sirnpry plane 

surfaces, composed of either vesicular or compact granular basalt.

The explanation of the origin of aa adopted above was not accepted 

by Dana, a who suggests that the breaking of a lava crust may be due 

to moisture derived from the rocks over which lava flows and leading

to quicker cooling in certain areas than in others. Such an occurrence, however, even if proved to exert an influence, seemingly introduces a variation into a more general process, without supplanting 

the controlling conditions.

LAVA CAVES.

In the production of an aa surface, as already stated, a rigid 

crust formed on the surface of a lava stream, becomes broken by the 

flow of the still liquid lava beneath. If the crust is of sufficient 

strength, however, not to be broken by the underflow, the lava beneath 

may flow out so as to leave a cavern. As is well known, this has 

occurred in many instances. Examples of this class of caverns occur 

in the lava that came from Black Butte, near its source, where it had 

formed by its own upbuilding a considerable gradient, but none were 

observed intact in the nearly flat lava fields about the Cinder Buttes,

 '.'I. P. Dana, Characteristics of Volcanoes. New York, 1890, pp. 242-24-1.
.RUSSELL.] LAVA CAVES. 99

although certain steep-sided depressions are there present which perhaps represent such caverns, whose roofs and sides have fallen in. 

These sunken areas vary in length up to 200 or 300 feet, and are from 

50 to perhaps 70 feet wide, and 40 to 50 feet deep. Their bottoms and 

sides are strewn with large blocks of their fallen roofs. Lava caves of 

the nature here considered occur at several localities in the older sheets 

of Snake River lava, but are not known where the Snake River and 

its tributaries have excavated canyons in the nearly level sheets. One 

was visited by me, on the eastern slope of Notched Butte, about 4 

miles south of Shoshone, and several of large size are reported to 

occur about 6 miles northwest of the same town, where lava descended 

from the mountains before reaching the adjacent plain. The cavern 

on the side of Notched Butte was entered through an opening formed 

by the falling in of a part of its roof. The portion open to inspection 

is 300 to 400 feet long, 25 to 30 feet wide, and is partially filled with 

blocks that have fallen from the under surface of its cover. The 

height of the opening at present is from 6 to 10 feet. In continuation of the portion of the cavern still remaining, there is a depression 

about 15 feet deep which is crossed at one locality by a natural bridge 

formed of a portion of the roof still in place.

The interiors of such caverns present various details, due principally 

to the drip of the lava while yet hot and mobile. The falling in of 

the thick roofs of this variety of lava caverns is evidently not. in all 

cases due to a sudden collapse. The cave referred to, on Notched 

Butte, has been enlarged upward by the falling of blocks from the 

under side of its roof, and I think none of the original under surface 

of the arch remains. This process continuing, openings will finally 

be made to the surface, and'more or less gradually the entire roof will 

fall. The cause of the displacement of blocks from time to time from 

the roof of such a cavern is difficult of explanation. The only agency 

that can be appealed to as generally active is change of temperature, 

but this can not be considered as important in caves with roof 20 to 40 

or more feet thick, as is frequently the case, until openings have been 

made. The temperature of caverns situated at such depths is generally uniform. The only other Agency that I can suggest is earthquake shock. That earthquakes may have occurred in the region 

where Notched Butte is situated is shown by the presence of faults 

in the Snake River lava, as will be described later.

From what is known concerning lava caves due to outflow of still 

liquid or plastic material from beneath a rigid crust, it appears that 

the controlling condition favorable to their formation is a sufficient 

gradient to permit the subsurface lava to flow, but yet not of such 

steepness as to cause a current which would shatter the crust in the 

earlier stages of its formation. A delicate adjustment, between rate 

of cooling and rate of flow is also necessary. The caves should be
100 SNAKE RIVEE PLAINS OF IDAHO. [BULL. 199.

expected to occur where the gradient is gentle, but still sufficient to 

insure a draining away'of the lower portion of a lava stream after a 

crust too thick and strong to be wrinkled or broken by the friction of 

the underflow has formed. The underflow must evidently produce a 

current of restricted width, for if broad, the arch left would fail to 

support its own weight and subsidence would occur, probably resulting 

in the production of a more or less characteristic aa surface. The 

length of the tunnel does not seem to be confined within narrow bonds, 

and it may extend for miles, in the direction in which the lava stream 

flows. The presence of the caves is not suggested at the surface 

unless a sagging of their roofs has occurred. The caves in cross 

section show a flat arched roof resting on vertical side walls and nearly 

flat floors.

The formation of lava caves of considerable size by the arching of 

a still somewhat plastic lava crust, due to lateral pressure caused by an 

underflow, has already been described. Their presence is indicated at 

the surface by an arched ridge, rising above the adjacent and usually 

flat surface. Within the caves, as a rule perhaps, the arch of the roof 

springs from the flat floor and vertical side walls are absent; there 

are exceptions to this, however, and in such instances there has probably been an outflow of material as in the formation of the variety of 

caverns noted above. The roofs are relatively thin from having been 

forced up into true arches, which are more perfect structures from an 

engineering point of view than the flat-topped roofs left by an outflow of lava from beneath a thick crust. These caverns are elongate, 

their length being at right angles to the direction of flow of the lava 

stream which produced them. A characteristic feature of the interiors 

is the roughness of their roofs, which, as already stated, have the 

appearance which is produced by the pulling apart of a highly viscous

substance. This appearance is more pronounced on the roofs than on 

the floors, owing to the fact that the separation took place when the 

nearly solid crust rested on still plastic material below, which settled to 

an even surface. In addition to the "pulled-dough" forms in the 

roof, there are sometimes pendent stalactite-like masses formed by the 

congealing of lava, which was at first sufficiently fluid or plastic to 

drip.

There is still another variety of lava caverns due to the blowing out 

by escaping steam of still liquid or highly plastic lava through openings in a solid crust. The chimney-like openings in the parasitic 

cones described on a previous page are examples of " vertical caverns" which have recesses opening from them at their bottoms. 

The claim that the horizontal enlargements are due to the cause 

suggested requires confirmation, but the cones built of clots of lava, 

scoriaceous bombs, etc., contain far more material than the vertical 

openings within them could have furnished. This is apparent when
RUSSEI.I..] HOLES IN LAVA SHEETS. 101

it is remembered that the vertical shafts are principally in the builtup portions of the "chimneys," and hence the material blown out 

must have been supplied in large part by the horizontal galleries to 

which the vertical shafts lead.

In some instances parasitic or "driblet" cones, are closed at the top 

so as to form beehive-like piles. These peculiar structures, built of 

adhering clots of lava, sometimes contain circular rooms that are 15 to 

20 feet in diameter and 15 or more feet high. Their floors are usually 

flat and their arched sides and ceilings are hung with pendent masses 

of lava which cooled as it dripped.

DEPRESSIONS IN THE SURFACES OP LAVA SHEETS. (

The falling in of cavern roofs so as to produce open depressions in 

the surface of a lava stream has already been referred to. This has

been a common occurrence on the younger flows, such as those about 

the Cinder Buttes, Black Butte, etc. These holes, pits, trenches, etc.,. 

are frequently 15 to 20 feet in diameter and 10 to 20 or perhaps 50 

feet deep, but ragged gulfs of much greater dimensions are also present, especially on Black Butte. In some instances they are several 

times as long as wide, or have a linear arrangement showing that the 

roof of a long subterranean gallery has fallen in throughout a considerable part or perhaps the whole of its length, or else given way in 

places, producing several pits. When the fall of a cavern roof has 

occurred recently its fragments may be recognized in the confused 

pile of debris at the bottom of the depression left, but more frequently 

quantities of dust or soil have been blown and washed in, and bushes, 

taking root, conceal the dislodged fragments.

In a few instances the roofs of caverns have been known to fall, 

and the liability of such an. occurrence makes traveling over the 

younger lava fields somewhat dangerous. I have been informed that 

only a few years ago, in the portion of the lava flow south of Cinder 

Buttes, a team of horses and a wagon broke through a cavern roof and 

went down with the blocks that fell.

On the surfaces of the older lava flows, now mostly covered with a 

fine yellowish soil, pits and steep-sided depressions of the nature just 

described are rare and seemingly wanting. The reason for this is, 

apparent!}7 , that they have been filled with wind-borne debris. On the 

surf aces of the older flows there are, however, occasional shallow depressions from a fraction of an acre to several acres in extent which are 

bordered in part or wholly by ridges of lava. These depressions are, 

in many instances, occupied by water during the rainy season and 

transformed into shallow, ephemeral pools, of the variety termed 

playa lakes. In summer the water evaporates, leaving mud flats or 

playas. The depth of the fine silt-like material occupying these oppressions is known from borings, in one instance, to be about 40 feet. It
102 SNAKE EIVER PLAINS OF IDAHO. [BULL. 199.

thus appears that there are depressions in the surfaces of the older 

lava sheets which are analogous to those in the younger lavas, and are 

probably also of similar origin.

MARGINS OF LAVA FLOWS TERMINATING ON A PLAIN.

The principal variations in the character of the margins of lava 

sheets which expand on a plain are determined by the plasticity or 

rigidity of the lava. If the lava is highly plastic, or liquid, it terminates in a low frontal slope, having the characteristics of pahoehoe; 

in such instances it may thin out to a feather edge, only a few inches 

thick, with local extensions here and there, which are highly scoriaceous within and have oval and frequently wrinkled surfaces. When 

lava becomes thick and viscous, and especially if blocks formed by the 

breaking of a rigid crust are inclosed by it, its flow is retarded and its 

margin presents a steep slope. In such instances the distal end of a 

lava stream frequently terminates in a nearly vertical escarpment 20 

to 30 feet or more high. Each of these variations is admirably illustrated about Black Butte, in the valley of Big Wood River, where in 

places the lava advanced onto a plain and terminated in a feather edge 

of pahoehoe; again, to the northeast of the butte, the side of a lava 

flow when seen from below appears as a rugged wall of angular blocks, 

about 30 feet high. From a comparison of numerous examples which 

have come under my notice it appears that streams of acid lava usually 

terminate in steep frontal slopes, while basic lavas, if in the condition 

to produce pahoehoe, have thin margins, and if aa is present, form 

rugged bordering slopes.

MARGINS OF LAVA TERMINATING AT THE MOUNTAINS.

Where the great southward-flowing lava stream from the Cinder 

Buttes met the deeply indented border of the mountains, interesting 

topographic changes resulted. The lava, as previously stated, was 

highly fluid when extruded, and flowed with 'almost the freedom of 

water. On the plain it spread out and formed what may be termed a 

lake of liquid rock. The western shore of this lake for a distance of 

fully 30 miles in a straight line is formed by steep mountain slopes 

and presents the general features that would be seen along the shore 

of a lake occupying the Snake River Plains. The margin of the lava 

is approximately a contour line. The difference in elevation of the 

surface of the lava in a distance of 30 miles is about 1,000 feet. Probably considerably more than one-half of the descent occurs in the first 10 

miles after leaving the Cinder Buttes. In the southern two-thirds of the 

flow no eye can observe that it is not a perfect plain. The liquid rock 

entered the mouths of the valleys in the mountains which open out 

into the Snake River Plains and extended up them various distances,.
RUSSELL.] MABGINS OF LAVA SHEETS. 103

dependent on their gradients. Where the ascent was gentle it flowed 

up them 5 or 6 miles before being checked by the rise of the land. 

The ridges between the mountain valleys became capes and headlands, 

and the peaks at their extremities were, in a few conspicuous instances, 

converted into islands. About 10 miles southwest of the Cinder Butte 

the lava was partially checked by a ridge of quartzite projecting well 

into the plain, but crossed it at a saddle and descended as a cascade 

about 200 feet high on its southern side. This lateral offshoot of lava 

formed a stream which, at the crest of the cliff down which it cascaded, 

was about 600 feet wide. During its maximum it was 30 to 35 feet 

higher than the surface now remaining, and left a ridge of angular 

fragments resembling a lateral moraine on each side of its course. 

Below the cascade, the lava expanded and reunited wi'th the portion of 

the main flow which went around the end of the cape and extended a 

mile dr more up a lateral valley. An elevation near the end of the 

ridge across which the lava flowed was left as an island or a steptoe. 

Another saddle, now crossed by a wagon road, about 500 feet farther 

up the crest of the ridge than the lava cascade, was barely reached by 

the lava, which, however, did not flow down the southwest slope, but 

congealed after forming tongues of pahoehoe, which had started to 

descend. In a few other instances, between the Cinder Buttes and 

the southward-projecting mountain spur south of Carey, islands of 

quartzite rise through the fresh black lava.

The wagon road between Carey and Martin follows for nearly the 

entire distance about 40 miles in a straight line the immediate border of fresh lava fields, including all its sinuosities. This road, between 

the two places named, is fully twice as long as a straight line connecting them. It enters nearly all of the lateral valleys as far as the 

lava extended, and winds about the ends of nearly all the mountain 

spurs that project into the plain. The highway is held rigidly to this 

course- almost a contour line by the precipitous mountain slopes on 

one side, and by a wall of rugged lava, frequently 15 to 20 feet high, 

on the other. In this narrow, trench-like depression some fine material, together with fallen blocks of stone, has served to grade the 

roadway. As the Cinder Buttes are approached, the material forming 

the roadbed shows a change in character, becoming finer and consisting mainly of lapilli and volcanic dust. Between the Cinder Buttes 

and the neighboring mountain the road passes over an extensive bed 

of coarse, scoriaceous lapilli or "cinders," which from its appearance 

has been reported to be "natural coke." The dust and lapilli were 

ejected from the Cinder Buttes during their explosive eruptions, and 

showered down on the adjacent mountains within a radius of about 10 

miles, but are wanting on the more recent lava flows. The thick 

accumulation of dust in the roadway was washed down from the adjacent mountain sides.
104 SNAKE KIVEE PLAINS OF IDAHO. [BULL. 199.

Where a tongue of lava extended up a lateral valley it frequently presents a ridge of aa on its immediate border, and, in numerous instances, 

all along its margin there are ridges with open fissures in their crests, 

produced by lateral pressure on a thick and nearty rigid crust. In 

numerous instances, also, the lava, after entering the mouth of a lateral valley and perhaps extending 3 or 4 miles from the border of the 

main flow, and hardening at the surface, receded, there being an outward underflow. In such instances broad, shallow basins, with rough 

surfaces, were formed, margined on their border adjacent to the older 

rocks (mostly quartzite) by ridges 10 to 15 feet high. These ridges 

are usually arches, or inclined blocks, produced by lateral thrust, but in 

addition there has been a withdrawal of the lava from beneath the 

floor of the basins. The explanation of this phenomenon seems to be 

that the lava after entering a lateral valley, and cooling so as to form a 

crust usually 3 to 5 or more feet thick, receded, being allowed to flow 

out, because the main lava flow across the mouth of the valley had been 

lowered by its onward progress.

In some instances lava streams originating in the mountains, as 

described on a preceding page, and flowing down lateral valleys before 

reaching the Snake Eiver Plains, expanded in the broader portions of 

their courses, and were .later, in part, drawn oft' by an underflow, 

leaving their hardened crusts stranded. An example of this nature 

occurs in the valley of Lava Creek, about 1 mile above Martin. The 

lava stream which came down the valley of Lava Creek, as already 

described, formed cascades in the upper part of its course, but farther 

down expanded and became about 1 mile wide. About the western 

margin of this broader portion of the lava stream there is now a 

ridge consisting of pressure domes and tilted lava blocks, bordering a 

broad, flat-bottomed depression. In this instance also there was a withdrawal of ,the still-molten rock from beneath the rigid crust, the edge 

of the crust being left stranded. The phenomenon here referred to is 

similar to that which produces lava caves by the outflowing of liquid 

lava from beneath a rigid crust, but the area of hardened lava left 

unsupported from beneath was so great that it could not sustain its 

own weight, and it collapsed and became broken.

The basins just described might become occupied by water and thus 

be transformed into lakes, but I am not aware of an instance in which 

this has happened. Apparently the bottoms of the basins are too much 

fissured to retain water, unless a considerable amount of silt were 

deposited on them. ,-

The encroachment of recent lava flows on the bases of the mountains 

has exerted an important influence on the surface drainage. The lava 

entering the mouths of valleys sometimes formed dams, which held 

their waters in check and caused lakes to form. An instance of this 

nature is furnished by Lava Lake, situated at the entrance of Fish
RUSSELL.] AGE OF THE LATEK LAVA FLOWS. 105

Creek Valley. The eastern wall of this water body, which is about 

200 or 300 acres in area, is formed by a wall of aa and pressure ridges; 

its western shore is composed of alluvium washed from the mountains.

When the lava that entered a lateral valley terminates in a thin edge 

the alluvium from the mountains usually extends out upon it, concealing its actual margin, and no lake results.

The reason why more lakes are not present about the border of the 

lava is twofold: First, on account of the small rainfall the streams are 

usually weak and disappear in summer, and are unable to form perennial lakes even under favorable conditions; and, second, the lava is 

fissured and nonretentive.

As will appear later, the changes produced in the topography where

the recent lava flows from the Cinder Buttes meet the mountains

seem to explain many similar changes, frequently on a far grander

. scale, produced by the lava flows which came from much older craters.

RELATIVE AGE OF THE LATER LAVA FLOWS.

As has been stated, at least six large streams of lava flowed from 

the Cinder Buttes at a recent date. Among these certain differences 

in age are readily distinguished. In reference to three of the main 

flow, namely, the two .most westerly on the north side and the great 

stream which was supplied from two sources on the south side of the 

buttes, no tangible differences in age have been recognized. Each of 

these three great flows is as fresh as if it had congealed and come to 

rest but yesterday. The lava appears black to one walking over it, 

but at a little distance, and in certain stages of illumination, has a 

light-gray appearance as if uniformly and lightly covered with dust. 

That this appearance is due to dust, however, seems improbable, as it 

does not reveal itself on close inspection. This surface "bloom," 

whatever its cause, is certainly an indication of youth, as it is absent 

on lava flows known from other reasons to be older. These recent 

flows are totally bare of soil, lapilli, volcanic dust, etc., and only to a 

slight extent have lichens taken root upon them. No positive evidence 

was obtained to show that the dead trees which occur along their borders in certain instances were killed by their heat. The remnants of 

the craters from which the lava was poured out are tree clothed, and 

on the supposition that the lava outflows immediately followed the 

explosive eruptions which built the craters, the lava is older than the 

trees, many of which are fully 20 inches or 2 feet in diameter. 

Although it is impossible to make a well-founded estimate of the time 

that has elapsed since the last eruption, it seems probable that it is no 

more than one hundred or possibty one hundred and fifty years.

Next older than the three lava streams just referred to, so far as one 

can judge, is a stream which skirts the base of the highest of the buttes 

on its western side and expands on the plain to the southward. This
106 SNAKE KIVEE PLAINS OF IDAHO. [BULL. 199,

was a strong flow, although smaller than the ones just referred to as 

being of decidedly recent date, and presents remarkable examples of 

large swells and stream-like pahoehoe ridges crossing one another. 

The lava, although bare and still fresh in general appearance, has 

evidently lost the bloom of youth, and its surface shows some indications of weathering. The most interesting feature in this connection 

is the presence on the surface of the smooth pahoehoe swells of a thin, 

deep-blue incrustation or film of the nature of '' desert varnish. "a The 

thin films designated by this term occur on rocks which are exposed 

to an arid climate, and seem to be due to the solution by absorbed 

water of some of the material forming them, and to its transfer, 

through the action of capillarity as surface drying takes place, to the 

surface, where it is precipitated. The examples of desert varnish 

described by Gilbert and Diller are of various shades of brown deepening to black, and are due to a film of iron and manganous oxides. In 

the present instance the surface film is a strong, deep blue, closely 

similar to earthenware colored with cobalt. The color is a decided 

cobalt blue, but, as chemical tests show, is not due to that metal. 

Attempts to separate enough of the film to serve for analysis have 

failed, and it may be a physical rather than a chemical phenomenon. 

That the color is of the nature of a desert varnish and not due to 

oxidation as the lava cooled, in a way similar to the changes occurring 

on the surface of steel and other metals when highly heated and allowed 

to cool, is seemingly shown by its presence on exposed surfaces and the 

upper portions of the sides of fissures and its absence on the walls 

of cavities unless they were broken at about the time the lava hardened. The color is deepest near the borders of crevices and becomes 

lighter on the surfaces between the cracks. In many instances long, 

sinuous, stream-like ridges emerge indefinitely on the surface of the 

lava stream, become prominent for a distance of perhaps 10 to 30 feet 

and then disappear beneath other ridges or swells formed b}^ similar 

local outbreaks of viscous lava. These ridges are covered with a network of small shrinkage cracks, the borders of which are deep blue and 

the central parts of the interspaces light blue or gray. The appearance of these tessellated serpent-like forms is frequently striking. 

Their comparison to scaled reptiles, although fanciful, is suggestive 

of their appearance. In my notes I have termed the lava stream bearing these unique forms the Blue Dragon lava flow.

The opposite neighbor of the Blue Dragon lava flow, or the third 

recent lava stream on the north side of the Cinder Buttes, counting 

from the west, is not as extensive as the other streams which went 

northward, although it presents a typical pahoehoe surface fully half 

a mile in length. This stream, although still young, bears evidence of

a A. term proposed by G. K. Gilbert, and more fully explained by J. S. Diller in The Educational 

Series of rock specimens, Bull. U. S. Geol. Survey No. 150, Washington, 1898,'pp. 389-391.
RUSSELL.] EELATIONS OF THE SEVEEAL ERUPTIONS. . 107

having been longer exposed to the atmosphere than any of those mentioned above. The smooth swells and ridges are still bare and preserve all their corrugations, pressure ridges, etc., intact, but their 

surfaces have lost their freshness-, and a little soil has been concentrated in the hollows and crevices. A striking feature of this generally bare lava surface is the presence upon it of pine trees, which seem 

to spring from the naked rock. The trees, some of which are 20 feet 

high, are gnarled and deformed, showing plainly in their contorted 

forms that their struggle for existence is severe. In many instances 

the cracks in which the trees have taken root are so small that they 

escape notice unless searched for. The trees are immediately surrounded on all sides by bare corrugated lava. In some examples a 

tree rises from the intersection of two cracks, where the opening is 

a little larger than elsewhere and a little more soil has been caught, 

showing how persistently the vegetation has sought for a foothold. 

The pines are scattered at intervals over an area of several square 

miles, being- grouped in small groves in the hollows. They extend to 

the bordering banks of lapilli where, finding less adverse conditions, 

they are of larger size.

The soil gathered in the crevices and depressions of the lava is 

evidently not derived from the disintegration of the lava itself, which, 

as stated, still retains even the smaller details of its original surface, 

and is hard and black. A surface covering of lapilli and volcanic dust 

is absent, although the bordering hills are composed of such material, 

and it is evident that no explosive eruptions have caused showers of 

rock fragments to fall on the lava stream. This is a suggestive fact, 

as the volcanoes a mile or two to the west sent out their great lava 

streams after the one here considered was formed. The tuff cones 

from which they came, and the widely extended surface sheet of lapilli 

and dust on the adjacent mountains, so far as can be judged, must also 

be of much later date. The reason why the tree-covered lava stream 

escaped receiving a shower of lapilli and dust seems to be that the wind 

carried the material, which was blown out by what must be considered 

more recent volcanoes, in'other directions.

The soil in the crevices and hollows, in which the pines referred to 

have taken root, is apparently composed of ordinary atmospheric dust 

brought by the wind, a process which is still operative.

RELATION OF THE CINDER BUTTES TO OLDER VOLCANIC ERUPTIONS.

To the east of the tree-covered lava streams described above, still 

other local lava flows are present. Some of these can be readily traced 

to the craters from which they came, but they are now almost completely soil covered and clothed with shrubs and grass, and in part 

with trees. About these and extending far beyond the reach of vision, 

even to an observer standing on the highest of the Cinder Buttes, are 

the vast plains underlain by still older lava sheets, but now completely
108 SNAKE BIVEK PLAINS OF IDAHO. . [BULI,. 199.

soil covered over hundreds of square miles. The occasional dome and 

pressure ridges on these older lava flows are black, the edges of the 

fissures in them yet sharp, and the corrugations on their surfaces still 

clearly distinguishable. It is evident, therefore, that the soil concealing all but their more prominent rugosities is not derived from the 

disintegration and decay of the underlying lava. The nature, mode of 

origin, etc., of this widely extended surface sheet will be discussed 

later.

The phenomena connected with Cinder Buttes which are comparatively small volcanic cones, or fragments-of cones, built of scoria, 

lapilli, bombs, etc., by explosive eruptions, and which later sent out 

truly immense volumes of highly liquid lava, which spread widety 

over the adjacent plain, and added another sheet of basalt to those 

previously formed, etc. are all of recent date, and assist in interpreting the records of the still greater and much older eruptions, which 

formed by far the larger part of the -Snake River Plains. Additional 

assistance in this same connection is furnished by other but less 

remarkable volcanoes, also of recent date, which rise above the surface 

of the same vast lava plains.

Market Lake craters. About 6 miles northeast of the town, known 

as Market Lake there are two conspicuous buttes, which rise from 

500 to 600 feet above the surrounding plain. The smaller of the two, 

situated to the north of its companion, shown in PI. XVI, A, has an oval 

base measuring, approximately, 1 by 2 miles, in its principal diameters, and at the top is about 3,000 feet across from north to south and 

2,000 feet in a transverse direction. It has a well-defined crater in its 

summit, still about 150 feet deep, although containing much material 

blown or washed from the encircling wall. A secondary crater is 

stated by Bradley" to occur on the northwest portion of the main 

crater, which has a diameter of 200 or 300 feet. The cone is grass 

covered and bears a scattered growth of small juniper trees. It is 

composed almost entirety of }? ellowish lapilli, now loosely consolidated 

into tuff, which is well stratified, as is shown in PI. XVI, B, and has 

both the inward and outward dips so common in tuff cones. The beds 

forming the outer slopes are well exposed on account of wind erosion 

and dip away in all directions from the crater's rim, at angles in general of about 20°, but flatten near the base, where they appear to 

become nearly horizontal. On the inner side of the craters the beds 

of lapilli are inclined downward toward its center at angles of from 

25° to 30°. b Contained in the tuff are a few angular masses of scori-

«F. H. Bradley: Sixth Ann. Kept. U. S. Geol. and Geog. Surv. Terr., 1873, p. 210.

6Bradley suggests that the material composing these volcanic cones was deposited in water, and 

that a lake formerly existed on the Snake River Plains. My own observations failed to confirm 

either of these suggestions. The stratification of the tuff forming the craters is of the same character 

as that which is known to occur in many other cinder and tuff cones not formed in water, and calls for 

no special explanation. No evidence of the presence of a lake on the surrounding plains since the 

craters were built has been obtained.
BULLETIN NO. 199 PL. XVI

A. MARKET LAKE CRATER, IDAHO.

B. STRATIFIED LAPILLI, MARKET LAKE CRATER, IDAHO.
RUSSELL.] KUNA BUTTE. 109

aceous basalt and occasionally waterworn pebbles of quartz and of 

dense igneous rock resembling diorite. In certain layers of the tuff 

and intimately mingled with small .angular fragments of scoriaceous, 

glassy basalt, there are large quantities of angular quartz grains 

and other fragments, which appear to be feldspar. In some layers 

the sand grains far outnumber the lapilli fragments, and if the material 

did not occur in the walls of a crater it would certainly be taken for a 

bed of sandstone containing a limited amount of lapilli.. The nonvolcanic included material indicates that the conduit of the volcano 

was opened through coarse gravel, such as Snake River is now spreading out near at hand, and finer sediments, probably lake beds, consisting largely of sand.

The moderately compact tuff is sufficiently soft at a depth of a few 

feet below the surface to be cut with an ax and has been quarried at an

adjacent locality on the bank of Snake River for building purposes. 

There are several houses in Menan built of rough-dressed blocks of 

this stone.

The plain about the base of the butte is smooth for a distance of 

1,000 to 2,000 feet, on account of the lapilli blown and washed down 

from its sides; outward from this belt, except on the south, where 

alluvial deposits laid down by Snake River have modified the surface, 

is a rough plain of basalt with only a thin covering of wind-deposited 

material in the depressions.

The crater of the larger of the two cones, as stated by Bradley, is of 

somewhat greater size than that of the one just described, but is not 

so deep. The two volcanic cones are united at their bases and are 

undoubtedly of about the same age and moderate^ recent. Although 

comparatively young lava flows form the neighboring plain, it is not 

apparent that either of the volcanoes gave origin to a lava stream.

Kima Butte. Rising from the Snake River Plains about 17 miles 

northwest of Mountain Home, and 7 miles west of Cleft, as indicated 

on fig. 1, is an isolated cinder cone, 230 feet high, known as Kuna 

Butte, shown on PI. XVII. This conical elevation, rising from a 

nearly level and seemingly limitless plain, is a conspicuous object 

and a prominent and well-known landmark throughout a region several 

hundred square miles in area.

The butte is composed mainly of scoria; and lapilli, but, so far as 

can be distinguished beneath the soil and drifting sand about its base, 

did not give origin to a lava flow. Lava was blown out in a bighty 

plastic condition, however, as is shown by irregular, flattened cakes 

of highly scoriaceous basalt at the summit, which are 3 or 4 feet 

across and several inches thick. At the top of the cone there is a 

remnant of a once comparatively large crater, the walls of which 

have now fallen in, and its crest has become rounded and notched by 

erosion. There is a suggestion of compact lava in a gully on the
110 SNAKE EIVEB PLAINS OF IDAHO. [BULL. 199.

northeast slope, and possibly a summit overflow of liquid lava did 

occur, but the subsequent downwashing of lapilli has concealed the 

evidence in this connection which may formerly have been present.

From the summit of Kuna Butte four other similar but smaller 

conical elevations may be seen on the plain to the southwest, at distances of 4 to perhaps 10 miles. These appear to be cinder cones 

marking the sites of once active volcanoes.

Crater rings near Cleft. Three miles south of Cleft, and, as indicated on the map forming h'g. 1, at the top of a broad, low elevation

J

FIG, 1. Map of crater rings near Cleft, Scale, 1 inch = 2 miles; contour interval, 50 feet. Dotted

lines indicate stream channels; figures give elevation above the sea.

on the featureless plain, there are two circular depressions with vertical inclosing walls, but without elevated rims. These pits are evidently 

to be classed as crater rings," which are generally considered by 

geologists to owe their origin to volcanic explosions.

Each of these rings has a level floor composed of fine yellowish soil, 

like that covering the adjacent plains, and no crags or solid rock of 

any kind occur within them.

The smaller of the two pits, situated to the west of its companion, 

has a diameter, measured across its level floor, of about 800 feet. The 

inclosing cliffs, with conspicuous talus slopes, are 200 feet high, and 

present the appearance of the wall of a canyon cut in horizontally 

bedded sheets of massive and, in part, columnar basalt. The summit 

of the wall of the depression is surrounded, to use an expressive term 

current in the Far- West, by a "rim rock" of black lava. Some of

« J. W. Judd, Volcanoes. New York, 1881, pp. 170-176.
BULLETIN NO. 199 PL. XVII

A. KUNA BUTTE NEAR CLEFT, IDAHO.

CRATER RINGS NEAR CLEFT, IDAHO. 

Kuna Butte in the distance.
BUSSELL.] CEATER KINGS NEAE CLEFT. Ill

these features may be distinguished in the photograph reproduced in 

PI. XVII, B.

The larger of the pits is less markedly circular than its neighbor 

and about 1,100 feet in diameter at the bottom. Its walls are approximately of the same height as those of the smaller pit, but less continuous. There are two breaks in the rim rock, one on the northeast 

and the other on the southwest, down which a horseman can easily 

ride to the plain at the bottom. About the outer border of the larger 

pit, and in general a few rods away from its brink, there are irregular piles of lapilli with indefinite shapes, the higher ones forming 

broad hills that rise perhaps 50 feet above the adjacent plain.

The fact that these circular pits are depressions in a broad plain, 

composed of horizontally bedded and relatively thick sheets of basalt, 

indicates that they were formed after the basalt had cooled and 

hardened. The presence near them of considerable but not conspicuous deposits of lapilli although there are no cinder cones or other 

evidence of explosive volcanic eruption nearer than Kuna Butte, 7 

miles distant indicates that the fragmental material was blown out 

of the pit near which it occurs. The amount of this material in sight, 

however, is far too small to refill the adjacent depression if transferred to it; and is absent or concealed by more recently deposited 

soil from about the smaller depressions. The tentative explanation 

that these facts indicate is that two small volcanoes formerly existed 

where the crater rings now occur, and probably built cinder cones 

similar to Kuna Butte, and that later explosions occurred, which blew 

away the piles of fragments and enlarged the conduits above which 

they have been deposited. This suggested explanation, adopted from 

the studies of others in reference to similar crater rings elsewhere, is 

not entirely satisfactory, however, as in case such explosions as suggested did occur, we should expect to find blocks of lava torn from 

the walls of the conduits in the process of enlarging them, scattered 

over the surrounding surface. More than this, the two circular pits 

are less than 1,000 feet apart, and unless the explosions which produced them occurred simultaneously, one would be expected to be 

more or less completely filled by the debris from its neighbor. That 

an explosive eruption occurred in the case of the larger pit, however, 

is evident from the lapilli piles referred to. The only alternative 

hj^pothesis suggested by these depressions, and by others elsewhere, 

some of them several miles in diameter, is that the walls of the volcanoes broke away and fell in.on account of the withdrawal of the supporting lava formerly filling their conduits, after the manner in 

which the great crater-like depressions in the summits of certain 

Hawaiian volcanoes are known to have been enlarged.

Although it is necessary at present to leave these crater rings without a definite explanation, it is hoped that the facts recorded may
112 SNAKE KIVEE PLAINS OF IDAHO. [BULL. 199.

supplement observations in other similar instances, and thus assist in 

a small way in reaching a proper understanding of the series of similar 

depressions in volcanic regions in various countries.

OLDER CEATERS AND LAVA FLOWS. 

LAVA CONES.

The occurrence of low cones with immensely broad bases on the 

Snake River Plains- has already been referred to. These elevations 

are composed almost entirely of lava extruded in a molten and highly 

fluid condition, seemingly from a comparatively small vent, and owe 

their height mainly to the cooling and thickening of the lava about 

the place of emergence, so as to form the necessary slope down which 

it could continue to flow. As these mounds or low buttes are distinct 

from cinder cones, I venture to suggest the name "lava cones." An 

example of recent date is furnished by Black Butte, described on a 

previous page. Their characteristic shapes (PL XVIII) have already, 

perhaps, been sufficiently well described not to require repetition. 

They occur usually at wide intervals over the Snake River Plains, 

especially to the east of Shoshone and to the south of Big Butte. 

Owing to their distance apart and the absence of water in the region 

where they occur, only three were visited by me. The most characteristic of these is Notched Butte, 4 miles south of Shoshone.^ This is a 

conical elevation with gently sloping sides, 250 feet high, with a nearly 

flat top, but broken so as to present notches when seen from a distance. 

The sides are formed of lava sheets in which there are caves due to the 

flowing out of still molten rock from beneath a thick, rigid crust, as 

alread}r explained. The summit is formed of highly scoriaceous lava. 

There is evidence of considerable explosive violence at the top in the 

form of scoria in clot-like masses, mingled with thin sheets of vesicular lava. Evidently a shallow crater once existed at the summit. 

A connection between cinder and lava cones is thus shown, and the two 

are but extremes of a single process. When explosions predominated 

cinder cones were built, either with or without lava flows; and when 

the lava predominated a lava cone resulted.

Lava cones are evidently more enduring structures than cinder 

cones, and for this reason perhaps seem to have been the type of volcanoes that furnished most of the old lava sheets now occurring 

beneath the Snake River Plains.

LAVA SHEETS.

The fact that the Snake River Plains are underlain by lava sheets 

throughout perhaps eight-tenths of their area is indicated on the map 

forming PL I. The number of sheets can not be even approximately 

determined, but at several localities in Snake River Canyon four have
LJ. S. GEOLOGICAL SURVEY 

LAVA CONE, SNAKE RIVER PLAINS NEAR AR
RUSSELL.] LAVA STREAMS THAT ENTERED WATER. . 113

been seen in single vertical sections, with lake beds or other deposits 

between. The total, however, considering the whole area, is no doubt 

many times this number. The various sheets are not of the same 

extent, but overlap. The thicker portion of the pile is seemingly in 

the broadest part of the basin to the south of Big Butte, but this can 

not be proved, as no canyons exist there, and no drill holes have as 

yet been put down. From the mouth of Salmon River westward, the 

manner in which various sheets terminate unequally is well shown. 

That is, the lower sheets which extend farther south than the southern 

margin of the surface sheet are exposed in the canyon walls. 

X The sheets cut through by Snake River are, in general, compara-^ 

tively thin, the range in thickness being from 20 to 40 feet; but in 

the deeper portion of the canyon, for about 10 miles beloAV Shoshone 

Falls, about 500 to TOO feet of basalt are exposed, in which the thickness of the individual sheets seem to be greater, in general, than the

measures just stated, but the various layers are united in such a way 

as to render it difficult to determine their precise number.

The basalt shows considerable variation in its physical condition, 

being at places vesicular and again compact. Usually, the layers are 

obscurely jointed and columnar, the columns being vertical, but at 

times the columnar structure is pronounced, as is shown on Pis. VIII, .5, 

and IX, A. No doubt some variation in mineralogical and chemical 

composition occurs, but enough study has not been given to this phase 

of the subject to permit of drawing general conclusions.

LAVA STREAMS THAT FLOWED INTO WATER.

In the north wall of Snake River Canyon, from Bliss upstream to 

above the mouth of the Salmon River, there are abundant exposures 

of the eroded border of a lava sheet and at certain localities near 

Hagerman, of two lava sheets, which present conspicuous contrasts 

between the basal and central or upper portions. In these instances, 

while the upper and central parts of a lava sheet are granular, compact, or perhaps moderately vesicular, its lower portion is open in 

texture and composed of irregular fragments, some of which are 

extremely rough on the surface and within are open and cellular, 

resembling somewhat a mass of irregular twigs of glassy lava compressed into a moderately compact mass. This peculiar structure, 

incapable of being accurately described, and presenting many variations, is imperfectly shown on PI. XIV, A. In many instances this 

material forms rounded masses resembling a pillow folded on itself, as is 

shown on PL XIX, A. The lower surface of such a "pillow" is sometimes nearly flat, but more frequently it is concave and when found in 

place is seen to have taken the form of the upper surface of a similar 

mass on which it rests. These folded masses clearly indicate a rolling 

Bull. 199 02 8
114 SNAKE KIVEE PLAINS OF IDAHO. [BULL. 199.

up of the still plastic lava. Another step in this process is illustrated by 

spindle-shaped bodies 6 to 8 inches in diameter and a foot or more 

long, which in some examples have a scoriaceous core, involved in 

several layers of stony or glassy lava (PI. XIX, J5). The concentric 

white lines in this example are due to involved grains of sand. A more 

pronounced occurrence of the same nature is shown by oval or nearly 

spherical bowlder-like masses from a few inches to 2 or more feet in 

diameter, which are excessively hard and compact. The inner portions of these spherical masses are composed of ston}*- basalt, usually 

containing kernels of olivine, which are covered with a coating varying from half an inch to an inch or two in thickness, of black, 

glassy lava. The outer crust in some places has a smooth, black, .glittering surface, like bottle glass which while fused was poured over 

an irregular surface and allowed to cool quickly. In other places 

the surface coating of glass is rough and of a dull-brownish color. 

These balls, together with the less completely rolled-up pillow-like 

masses, are embedded in a coarse breccia consisting mainly of irregular glassy kernels, but frequently containing also angular fragments 

of compact granular basalt (PI. XX). The spherical masses of basalt 

just described appear to be analogous to certain "lava balls" observed 

by Dana a in lava streams of the Hawaiian Islands. These lava balls 

are stated to be commonly from 3 to 5 feet in diameter, but one contains at least a thousand tons of rock. Even the normal Hawaiian 

examples, however, are larger than the largest specimen seen by me 

in the walls of Snake River Canyon.

While the upper and central portions of the lava sheets referred to 

are composed of compact, granular, and frequently columnar basalt, 

usually more or less vesicular, their basal portions have an open texture, and consist mainly of glassy material. This contrast shows .that

the upper portion cooled slowly so as to form what may be termed 

normal basalt, while the basal portion cooled quickly. The glass}7" 

portion is not scoriaceous and has the appearance of obsidian, especially when examined under a microscope with reflected light. While 

this glass is characteristicalty cellular, the openings are not like those 

produced in scoriaceous lava by the expansion of steam or gases contained in the magma while still hot and plastic, but they are irregular 

cavities due to a force acting from without. The walls of the cavities 

and the rough, glassy offshoots and the extremely irregular branches 

about them are not vesicular, but are composed of black glass.

Another instructive fact is that the cellular, excessively irregular 

masses of glass, although black within, are nearly white at the surface. This is due to a thin incrustation which can not be washed off 

or removed with strong acids. Under a microscope, using reflected 

light, the incrustation is seen to be composed of white sand grains,

c J. P. Dana, Characteristics of Volcanoes, New York, 1890, pp. 10-11, 24J,
BULLETIN NO. 199 PL. XIX

A. PILLOW-LIKE FOLDS IN LAVA STREAM THAT ENTERED WATER

B. SECTION OF SPINDLE-LIKE ROLL OF LAVA FROM A LAVA STREAM THAT ENTERED

WATER.
RUSSELL.] LAVA STREAMS THAT ENTERED WATER. 115

partially embedded in the black glass. In many instances, also, the 

interiors of cavities are lined with similar material, and at times masses 

of sand or clay are completely inclosed in the cellular, glassy lava.

All of the facts enumerated unite in indicating that the lava while yet 

molten entered water and was quickly cooled, hardening to a glass, 

and that the steam generated blew the still plastic material into shreds, 

and excessively irregular branching forms. As the upper surfaces 

of the lava sheets are not glassy and do not show the other characteristics referred to, it appears that the waters which the still hot lava 

entered were shallow. The still plastic material in numerous instances 

was rolled or folded into spindle-shaped and pillow-like forms, and 

even into spherical and oval balls, the surfaces of which in contact with 

water cooled quickly to a glass and the part within developed large 

crystals of olivine and other minerals. All stages in this rolling-up 

process, from folded masses to complete spheres, are illustrated. The 

still plastic lava, coming in contact with the sand at the lake bottom, 

adhered to it, thus giving the black glass a white surface, and in many 

instances masses of sand and claj^ became involved in the basal portion 

of the flow* The characteristics here accounted for pertain to the 

lava which was fluid or plastic on entering water and was distended 

and variously modified by the steam generated, but not shattered. In 

other instances the rock was broken into angular fragments and a 

breccia produced. When this occurred it appears that the lava, 

although still hot, had lost its plasticity on entering the water and was 

fractured instead of being blown into shreds and similar branching 

forms.

When a lava stream enters water it is evident that a connected series 

of products should be expected, ranging from compact or what may 

be termed normal lava to lava that has been shredded, as it were, by 

steam explosions acting on it from the exterior, and from normal lava 

again to coarse and fine breccia, the controlling condition being the 

degree of plasticity or rigidity of the magma. Between basic and 

acid lava it is to be expected that the former would be the more apt to 

furnish cellular, torn, and ragged masses or be rolled into balls; while 

the latter, owing to its less fusibility and greater brittleness when 

solid, would be the more apt to become shattered.

The coarser breccia observed in connection with the steam-blown 

basalt in the walls of Snake River Canyon is composed of angular fragments of normal granular basalt, but the smaller fragments are glassy. 

The finer breccia resembles closely the tuff formed of lapilli blown 

out by steam explosions from volcanoes, but there seems to be a difference between the two, although I am not sure it can be readily 

recognized. Lapilli are characteristically and perhaps always scoriaceous, while the fragments produced by the contact of hot lava with 

water may not be scoriaceous, and in the case of lava streams that
116 SNAKE RIVER PLAINS OF IDAHO. [BULL.199.

have progressed far are normally compact. Either lapilli or the fragments produced by contact of hot lava with water may be glassy, but 

such fragments, at least in the tuff cones of Idaho that have been 

examined, are rare, while in the breccias produced by hot lava entering 

water they are common.

-> In association with the lava sheets cut through by Snake River there 

are immense beds of f ragmental material sometimes 100 to 160 or more 

feet thick, and traceable for several miles, which resemble closely the 

tuff about the Market Lake and other craters. In fact, they seem to 

have the characteristics of compacted lapilli or tuff, but again simulate the fragments produced by contact of hot lava with water. In 

which of these two ways the material referred to was principally produced I am not sure, but incline to the opinion that in the main it 

resulted from volcanic explosions and is a true tuff.

When a breccia is produced, including at times cellular lava and the 

"lava balls" referred to, the interspaces are completely filled with 

what was once sand or mud, and the mass is, as a whole, compact and 

essentially impervious to water; but when the cellular and steam-torn 

rock occurs, it is open in texture and in a condition to permit of the 

flow of water through it. These differences are significant in connection with the occurrence of springs and in reference to the possibility 

of obtaining artesian water. The truly wonderful springs at what is 

termed The Thousand Springs (PI. Ill), for example, pour out of a 

cellular lava of the nature described above. Near Hagerman, at two 

localities, tunnels or horizontal wells have been excavated in the basal 

portion of the lava flow and a strong outflow of water has been obtained.

The facts presented above seem to indicate that whenever a lava 

stream flows into water there will be steam explosions and a great disturbance of the bottom over which the lava flows. Remarkable examples of results of this nature may be seen in the northern wall of Snake 

River Canyon, about a mile upstream from the mouth of Salmon River, 

and near the Riverside ranch, where the involved and steam-torn lava 

and the associated breccia contain fragments of clearly recognizable 

stratified clay and masses of sand of all sizes up to 5 or 6 feet in diameter. Other exposures of the bases of lava streams, however, seem to 

show that lava may flow over a lake bottom without disturbing it or 

producing scarcely any discernible change in it.

An instance of the nature just referred to occurs in the east wall of 

the canyon of Canyon Creek, about a mile above its junction with 

Snake River. At this locality the rim rock of the canyon is formed by 

a lava sheet between 30 and 40 feet thick, which rests on fine, white, 

thinly laminated lake beds, of which about 12 feet in thickness are exposed. The lava, owing to wind erosion, projects about 10 feet be}rond 

the soft beds beneath, and its bottom is well exposed. The base of 

the lava is a flat, but moderately rough, surface, composed of cellular,
U. S. GEOLOGICAL SURVEY 

SECTION OF A LAVA STREAM THAT ENTERED WATER
RUSSELL.] IBBEGULAR THICKNESS OF LAVA SHEETS. 117

glassy basalt, while the upper part is granular and irregularly columnar. Involved in the glassy material forming the base of the sheet 

of basalt are a few small masses of soft, white, sandy clay, like the 

bed beneath. This indicates that the basalt flowed into a lake, and at 

its base was quickly cooled to a glass, which was expanded and made 

cellular by the steam generated. The striking feature of the exposure 

is that the soft white lake beds on which the lava rests are not hardened 

and are undisturbed, the lamina being still horizontal, even to the contact with the lava. Some of these features may be recognized in the 

photograph reproduced on PI. XXI. The only change is a slight 

yellow stain, perceptible to a depth of 5 or 6 inches from the. surface 

of the contact downward. This discoloration may have been produced 

subsequent to the coming of the lava and due to weathering.

The characteristics just described occur not at one small exposure 

only, but at several throughout a distance of about 600 or 800 feet. 

How a sheet of lava 30 to 40 feet thick could advance over a bed 

of soft unconsolidated sandy clay, which was evidently covered with 

water, without disturbing it in the least degree, is difficult to explain. 

Possibly the lava sheet may have advanced by sending out small thin 

streams of liquid rock of too little weight to disturb the beds on which 

they rested, which were later overridden by the main flow, but that 

such was the case is not apparent in the internal structure of the lava 

itself.

IRREGULARITIES IN THE THICKNESSES OF LAVA SHEETS.

An interesting fact in connection with the lava sheets exposed in 

section in the walls of Snake River Canyon below Shoshone Falls is 

that in several instances they exhibit conspicuous variations in thickness while their surfaces remain essentially horizontal. The obvious 

explanation of this is that the surfaces over which the lava flowed were 

irregular.

Examples of the phenomena referred to occur in the north wall of 

Snake River Canyon in the southeast portion of Ada County, where, 

as already stated, the rim rock forming the brink of the canyon, and 

usually having a thickness of 30 to 40 feet, thins to a few feet, and 

for a space a mile or more long is wanting. The beds of lapilli which 

occur normally below the sheet of basalt rise and protrude through it 

.so as to form low mounds which rise higher than the adjacent surface 

of the lava. In this instance the lava flowed against a hill of lapilli, 

probably completely surrounding it, and became thin and finally failed 

to cover the lower terrane on account of an elevation on the general 

surface over which it advanced.

Again, in the neighborhood of the mouth of Rattlesnake Creek 

there is a sheet of lava 40 feet thick which for a distance of 2 or more 

miles forms a conspicuous terrace on the north side of the canyon.
118 SNAKE EIVEK PLAINS OF IDAHO. [BULL. 199.

Farther downstream, just below the mouth of Rattlesnake Creek, 

this sheet of lava thickens abruptly to at least 175 feet the river 

having not as yet cut through its entire depth and south of the 

river it thins abruptly to a feather edge" and disappears. This lava sheet 

must have advanced over a generally plane surface in which there was 

a depression at least 135 feet deep. The depression was filled by the lava 

which flowed beyond it, and an essentially level surface was produced. 

The lava where it is thin has a glassy structure and bears other evidence of having flowed into water, but where it is thick such characteristics are wanting in the part exposed. From the facts observed, it 

is surmised that the lava entered a lake, in the bottom of which there 

was a marked depression which became filled with lava, or else flowed 

over an eroded land surface the hollows in which were occupied by 

water. Where the lava sheet was thin the changes produced on coming in contact with water affected it throughout its entire depth, but 

where it was thick the upper portion cooled slowly and assumed the 

appearance of lava which has cooled on land.

The study of the lava sheets that advanced over surfaces having 

hollows or depressions in them has not been carried far enough to 

show whether they entered lakes in all instances or not. Sometimes 

the lava rests on waterworn, gravel, and this and other facts suggest 

that it advanced over a previously stream-eroded land surface and 

entered the valleys where it became thicker in case the depressions 

were filled, and also came in contact with the waters of streams. The 

results of these two sets of conditions would be much the same, so far 

as -the appearances to be observed in the walls of can}'ons subsequently 

excavated through the lava and associated beds are concerned. In 

the case of a lava sheet entering a broad lake, however, one would

expect that the beds beneath it would be fine clays or sand, and in the

case of a lava-filled stream valley coarse gravel and bowlders would 

be apt to be present. But such a correlation can not be relied upon 

implicitly, since lakes may have broad areas of pebbles and bowlders 

adjacent to their margins and bars of similar material extending far 

from shore, while rivers may flow through broad valleys floored with 

fine flood-plain deposits which are indistinguishable in most ways from 

even the finest sediments of lakes.

CHANGES PRODUCED IN LAVA SHEETS AFTER COOLING. 

OPEN FISSURES AND FAULTS.

The surfaces of the recent lava sheets about the Cinder Buttes are 

crossed in several instances by open fissures, from a fraction of an 

inch to several inches and in some cases a foot or more wide, which 

have opened since the lava hardened. Possibly these are due to 

stresses generated by the 'contracting of the lava on cooling, but at
U. S. GEOLO'ICAL SURVEY

LAVA RESTING ON UNDISTURBED LAKE BEDS, CANYON CREEK, IDAHO.
RUSSKLI,.] . OPEN FISSURES : AND FAULTS. 119

one locality to the north of the highest of the buttes a block of recent 

lava measuring several hundred feet in diameter has been elevated and 

sharply tilted, thus indicating that movements in the older rocks 

beneath the recent surface sheets have taken place.

In the summit of Black Crater there is a gulf, not of the nature of 

a crater, but of an open cleft, in the walls of which the edges of thin 

layers of lava are broken across and well exposed. This gulf is by 

estimate 300 feet across and 100 feet deep, and traverses the summit 

of the butte in a northeast-southwest direction. In its bottom there 

is black, scoriaceous lava which rose after the fissure was opened, and 

now forms a pahoehoe floor. This large fissure joins another, or, perhaps more accurately, two others at its southwest extremity. These 

branching fissures, 20 to 30 feet across, traverse the flanks of the butte 

irregularly and in their walls expose admirable sections of the thinbedded, highly scoriaceous lava of which the crater is composed.. In 

this case it is evident that the crater has been badly shattered, not b}^ 

a steam explosion, for there are no blocks of lava or fragments of the 

nature of lapilli scoria, etc., about the openings, but owing to an overflow of still liquid lava from beneath, or by an earthquake.

Similar open fissures occur also in certain instances in the older 

sheets of Snake River lava, and are evidently of recent origin.

At Cleft the surface of the surrounding nearly featureless plain is 

formed by a sheet of massive, vesicular lava-having a rudely columnar 

structure, which is broken by a fissure having several branches that 

run nearly east and west and can be traced for fully a mile. The 

fissure is from 5 to 10 feet wide, and is loosely filled with large 

blocks of basalt which have fallen from its side. The blocks rest 

against the sides of the cleft and support one another, leaving large 

open spaces into Avhich a person may easily descend at least 40 feet, 

' and it is evident that the opening is much deeper. The supported 

lava blocks in places form a series of floors, beneath which a person 

can clamber for distances of several hundred feet, as in a long, narrow 

cave; light from above being excluded by the roof formed of dislodged blocks. Other similar open fissures of still greater extent and 

depth are reported as occurring about 2 miles west of Cleft. In each 

of these instances there has been no displacement of the rocks forming 

the walls of the fissures, and to a person standing even a few yards to 

one side of a break no suggestion of its presence is visible on the surface of the plain. These fissures are of the same character as those 

sometimes formed during earthquakes, but instead of being due to 

earthquake shocks, they were produced, I am inclined to believe, by 

other causes, and at the time of their formation caused shocks or 

vibration in the rocks beneath the adjacent region.

About 1 mile east of Cleft the principal open fissure changes to a 

fault, the heaved side of which stands on a vertical escarpment of
120 SJSTAKE RIVER PLAINS OF IDAHO. [BULL. 199.

basalt from 10. to 25 feet high. It trends east and west and can be 

distinctly traced for half a mile or more. A view of a portion of this 

wall is shown on PL XXIII, A. This fault scarp faces south, and the 

adjacent portion of the sheet of obscurely columnar basalt that was 

broken across, and upraised, has a slight dip to the north. There is 

no open fissure at the base of the escarpment, for the reason, probably, 

that the change in the topography produced by the fault caused the 

line of fracture to become occupied by a small stream which flows. 

during the winter or when snow is melting.

The open fissure at Cleft, which changes to a fault when traced eastward, belongs to a series of recent faults, which are best displayed in 

the portion of the Snake River Plains that lies between 5 and 9 miles 

north of Mountain Home and between Canyon Creek on the west and 

Rattlesnake Creek on the east. The northern margin of this broken 

tract of old lava is formed by the precipitous southern or southwestern border of rugged mountains of rhyolite. In the area just referred 

to there are five principal faults, each trending about east and west, 

and presenting steep and ,in part vertical scarps of basalt facing south. 

The heaved block, the broken edge of which forms a bold escarpment, 

looking like a wall when seen from the south, is in each case inclined 

downward to the north and maintains a uniform or slightly decreasing 

dip to the foot of the next escarpment. The height of these walls 

varies from a few feet at their ends to 40 or 50 feet and in several 

localities reaches 150 feet or more. The most northerly of the series 

is close to the base of the mountains, and appears in the wall of the 

canyon cut by Canyon Creek as a broad, irregular cleft. The mountain face is itself a vast fault scarp, as has already been stated, and it 

is probable that a recent movement along this break in the nature of 

an elevation of the block forming the mountains has caused the comparatively small faults in the lava forming the adjacent portion of the 

plain.

The displacements to the north of Mountain Home are admirable 

examples of step faults, as they are termed that is, a series of nearty 

parallel breaks or cracks separating the rocks they traverse into long 

narrow blocks which are tilted in one direction. The breadth of the 

gently tilted blocks in the instance before us is in general about 1,000 

feet. The faults are not perfectly parallel, but in some instances unite 

or branch, maintaining, however, a general east-west direction, and 

generally coincide in trend with the great escarpment forming the 

border of the adjacent mountains. Some of the faults in the basalt 

extend east of Rattlesnake Creek, but were not followed in that direction. On the west the escarpments decrease gradually in height, and 

in most, if not all, instances die out on reaching a dome-like elevation 

in the basalt, described below, through which Canyon Creek has cut a 

narrow, steep-walled canyon.
RUSSELL. J t< OPEN FIS9UEE9 AND FAULTS. 121

Other faults, belonging to the series briefly described above and 

connecting it in a general way with the fault and open fissures near 

Cleft, occur on the west side of Canyon Creek, 5 miles northwest of 

Mountain Home. At the locality referred to there is an irregular but 

rudely triangular hill, as it would appear on a map, measuring about 

a mile on each side, the surface of which is inclined to the northwest. 

It is bounded b}r precipitous escarpments from 300 to 400 feet high on 

its eastern and southern border. The form of this prominent elevation and the character of its .precipitous borders facing eastward and 

southward show that it is an elevated block bounded in part by faults. 

The elevated tract is composed of stratified basalt, as is shown particularty in its southern escarpment, which is more clearly due to faulting 

than its steep eastern face. The fault scarp on the south side of the 

hill dies out when traced westward, but is succeeded b}7 other escarpments bordering another and lower hill, the structure of which is 

obscure.

The fault scarps to the north of Mountain Home are associated with 

other topographic forms, due to movements in the lava beneath that 

portion of the Snake River Plains.

South of the locality .where Ca^^on Creek leaves the mountains of 

rh^yolite, in which its two principal branches have excavated deep, 

flaring canyons, and enters a narrow gorge with vertical walls of columnar basalt (PI. X, J3), there has been an upward bending of the 

sheets of lava so as to form what may be described as half of a low, 

elongated dome or broad-pitching anticline. The longer axis of this 

elevation runs approximately northeast and southwest, or, in a general 

way, at right angles to the great escarpment forming the border of 

the adjacent mountains, and also normal to the direction of the small 

faults in the basalt between Canyon and Rattlesnake creeks. The 

arching of the basalt is most pronounced at the base of the mountains, 

where it is perhaps 3 miles broad, and dies out southward in a distance of about 4 miles, where it meets the triangular hill referred to 

previously. Canyon Creek follows the longer axis of the elevation 

and has cut a canyon in it which is 150 feet deep adjacent to the mountains and which decreases southward. On leaving the short canyon 

cut in the dome the creek becomes a surface stream and is spreading 

out an alluvial fan. The nature of the pressure which arched the lava 

in the manner just described was not determined. Seemingly it had 

no clear relation to the movements which produced faulting in the 

adjacent portion of the plain. Relief from pressure in one instance 

was obtained by an arching of the strata, while in the other instance 

breaks occurred. One of these breaks, however, as noted above, 

cut the fold near its northern end and was certainly of later date 

than the upraising of the arch. Then, too, the longer axis of the 

fold is at right angles to the trend of the neighboring faults, which
122 SNAKE EIVEB PLAINS OF IDAHO. [BULL. 199.

would not be expected if one movement was responsible for each class 

of deformations.

The broad gentle depression of the strata beneath the Snake River 

Plain, previously referred to as the Bruneau artesian basin, involved 

several sheets of lava, which were gentty bent in common with the 

associated beds of lacustral and perhaps in part river sediments. 

Further attention will be given this broad syncline in the second part 

of this paper.

ROCK DISINTEGRATION AND DECAY.

Under the climatic conditions now prevailing, which no doubt with 

minor variations have been in continuance for a long period of time, 

rock decay is progressing but slowly, while rock disintegration, through 

the action of changes of temperature, freezing of water, etc., is much 

more rapid. Mountains of quartzite are practically buried beneath 

their own debris, the fragments showing but little change from the 

unaltered parent rock. Mountains of granite are still more deeply 

sheathed with fragments of their own rock, but in this case much 

chemical alteration is manifest. The surfaces of basaltic lava sheets 

long exposed are covered with loose, rounded stones, usually of a rich- > 

brown color, to a depth in most instances of not more than a foot 

or two. Between the weathered stones there is in certain regions, 

but not generally, a soft, rich-brown soil that has resulted from the 

decay and disintegration of the basalt itself, together with fine dust 

deposited by the wind. The amount of decay, however, that even the 

oldest sheets of basalt now exposed have undergone is but small. 

Many old lava sheets, owing in part, perhaps, to their having been 

covered by protecting layers now removed, still retain their characteristic surface markings, such as corrugations, pressure ridges, etc,,

in what may be termed a legible condition. While such markings are 

perhaps not an infallible sign that they were formed at the actual 

surface of a lava flow as already noted, their presence over large 

areas must be taken as evidence that such is the case. Perhaps the 

most conspicuous and general change that the exposed crags and rim * 

rocks of basalt have experienced is due to the action of wind-carried 

dust and sand. The rocks usually have a smoothed appearance, 

approaching a polish, and their surfaces are characteristically pitted 

with small, somewhat shell-like hollows, or shallow depressions, with 

smooth interiors. The depressions are probably due in part to the 

flaking of the rocks on account of sudden changes of temperature, but x 

the polishing is to be ascribed to the friction of wind-blown particles. 

These surface features, however, are never so conspicuous or well 

executed, one may say, as many well-known examples where quartzite, 

fine-grained limestone, etc., have been long exposed to the drifting

sands of deserts. V-
RUSSELL.] STREAM-CUT LAVA SHEETS. 123

The general conclusion In this connection is that the Snake River 

lava has suffered but slight changes, far too slight in fact to account 

for the presence of even the thin layer of soil that forms the actual 

surface over the several thousands of square miles of the lava-floored 

plains. The comparatively slight alterations referred to seem to mean 

either a very slow rate of change in response to atmospheric agencies, 

or else but a short exposure of the rock. The first of these reasons is 

not certainly true, but the second is plainly evident in a large number 

of instances.

In reference to progress made in disintegration and decaj^ a comparison of the Snake River lava with the Columbia River lava is of 

interest. The lower sheets of lava beneath the Snake River Plains, as 

previously stated, are of approximately the same geological age as 

the main mass of the Columbia River lava, but the upper sheets of 

the Snake River lava are very much younger than any part of the 

basalt included in the Columbia River lava. In harmony with this 

conclusion is the fact that the extensive sheets of basalt in southern. 

Idaho, although exposed to essentially the same climatic conditions that 

exist on the plains of the Columbia, are but slightly decayed; while 

the Columbia River lava at many localities and over areas embracing 

hundreds of square miles is so decayed to a depth of 40 to 60 or more 

feet that it is in the condition of clay, and can be molded in the fingers/' These facts sustain the conclusion derived from fossils, that 

the Columbia River lava is far older than the main portion of the 

similar formation in southern Idaho.

CANYONS AND WATERFALLS.

The streams which rise among the mountains bordering the Snake 

River Plains and flow across them bring silt, sand, gravel, and other 

deposits from their upper courses, and with these have cut deep channels even in the hard and nearly level lava sheets.- The master stream 

is Snake River. As that strong stream lowered its bed the rate of 

flow of its tributaries was increased and they deepened their channels also, but could not cut below the level of the controlling stream. 

While the stronger tributaries, such as Salmon and Bruneau rivers, 

were enabled to deepen their channels at the same rate as the master stream, and at their mouths have essentially the same surface 

level as the Snake, and enter it as slack-water streams, the weaker 

tributaries, like the numerous creeks in Elmore and adjoining counties, 

could not work so fast, and now in several instances enter the master 

stream with swift currents, and have falls near their mouths. The 

weaker streams, however, which flow through soft material near their

a The surface changes of the Columbia Kiver lava are described in the following reports: I. G. Rus_ 

sell, Water-supply and Irrigation Paper U. S. Geol. Survey No. 4,1897, pp. 57-68; Water-supply and 

Irrigation Paper U. S. Geol. Survey No. 63, Washington, 1901, pp. 42-51.
124 SNAKE EIVEE PLAINS OF IDAHO. [BULL. 199.

mouths, like Bennett, King Hill, and other creeps, have been able to 

keep pace with the down-cutting of the Snake, which is still working 

on hard basalt at several localities below the point where these tributaries enter.

The result of the concentration of energy in narrow belts at the bottoms of the streams has been to dissect the portion of the Snake River 

Plains situated west of American Falls, and to form a great system of 

canyons, with broad uneroded and nearly flat areas between. This 

portion of the region furnishes admirable examples of what has been 

termed young topography. Within this region, however, where the 

soft lake beds are not protected by a surface sheet of lava, as over 

great areas in the northern portion of Ow}7 hee County, even weak and 

ephemeral streams have been able to advance rapidly with their work, 

and much more mature topographic forms occur.

In the broader and most characteristic portion of the Snake River 

Plains, lying north and west of Snake River and east of Little 

Wood River, the surface is uncut by streams, and is still a vast 

uneroded plain. This tract, about 10,000 square miles in area, is an 

admirable illustration of a new land formed by lava outflows. It has 

been left with its original or constructional surface, in part because 

of its actual youthfulness, as measured in years, but it also owes its 

preservation more definitely to the small rainfall, which fails to supply 

the streams coming from the north and west with sufficient water to 

enable them to reach Snake River. This failure is due in part to the 

open structure of the lava itself, which favors subterranean rather 

than surface drainage. In this connection consideration must be 

given to the fact that the Snake in its upper course is supplied with 

more sand, gravel, and other material than it can carry across the 

plains, where its gradient becomes less than in the mountains to the

east, and deposition and the formation of broad alluvial fans and 

gravel flood plains on the surface of the lava are in progress.

As the portion of the Snake in southwestern Idaho, where it flows 

over soft sands and clays, is from 2,200 to 2,500 feet above sea level, 

it is evident that a sill of hard rock exists lower down stream, which 

has regulated the depth to which the river has been able to deepen its 

channel in these soft deposits. Below the mouth of the Pa}^ette the 

Snake flows through one of the most magnificent canyons in North 

America, one exceeded in grandeur of scenery only by the Grand 

Canyon of the Colorado. Although this region has not been carefully 

studied and is, in fact, almost entirely unknown to geologists, such 

information as is in hand indicates that a mass of resistant rock has 

been elevated athwart the course of the Snake, and that the task of 

sawing a canyon through the obstruction is still,in progress.

Without wishing to invite the reader to take too comprehensive a view 

of the later geographical history of the region under discussion, one
U. S. GEOLOGICAL SURVEY

TWIN FALLS, SNAKE RIVER, IDAHO.
RUSSELL.] STEEAM-CUT LAVA SHEETS. 125

other general principle which has influenced the erosion of the Snake 

River Plains may perhaps be cited.

 Snake River, as stated, is spreading out coarse deposits in the portion of its course above American Falls, and it may reasonably be 

asked why is it that the same stream lower down its course has been 

enabled to excavate a deep canyon. The reason is evident!3^ that owing 

to an increase in gradient in the portion of its channel below where it 

is laying aside its load, its rate of flow is increased and its capacity for 

work consequently augmented.

The scenery of Snake River Canyon presents many variations, 

dependent largely on the nature of the rocks cut through and especially on the presence or absence of lava sheets. Where alternating, 

nearly horizontal layers -of soft lake beds and hard lava occur, the 

deepening of the canyon has been retarded by the hard layer and 

accomplished mainly by the recession of cascades and waterfalls. It 

happens that the river in its course across southern Idaho passes from 

a region where lava sheets are thick with but little soft material 

between them as, for example, from American Falls to the foot of the 

deep, narrow canyon below Shoshone Falls to a region where the lava 

sheets in general become thinner and are separated one from another 

by soft lake beds. When the stream in its downcutting flowed over 

a nearly level sheet of basalt to its edge it quickly deepened its channel in the soft beds' encountered and a fall was produced. Such a fall 

would recede at a rate dependent on several conditions, but mainly on 

the thickness of the lava sheet and the depth of the channel below the 

cascade. In the main, the canyon of Snake River has been produced 

by the recession of a series of waterfalls of the nature just cited, and 

the process is still continuing. Each of the falls " nd rapids in the 

river is due to the presence of a resistant sheet of lava, in the border 

of which a notch of greater or less length has been cut. Where the 

lava sheet is thick, as at Twin Falls and Salmon Falls, a precipitous 

descent results; where the lava sheet is thin or composed of several 

thin layers of varying resistance, a succession of small leaps or a rapid 

is produced, as is the case to-day at several localities.

An exception to the rule just stated occurs in the case of Shoshone 

Falls, the highest and grandest of all the leaps Snake River makes. 

The river is here deepening its channel, mainly through horizontally 

bedded basalt, with a mass of rhyolite beneath. The surface of the 

lower and harder rock was not a plane, as are the lava sheets, but is 

irregular, and a series of rapids was probably formed which developed into a single great fall. The fall has receded about 5 miles in the 

rhyolite and at present, judging from the height to which the rhyolite above the falls rises into the lava, is as high as it will ever become. 

As the fall continues to recede it will probably decrease in height, and 

when the obstruction that causes it is cut across, will resume the 

characteristics due to thick lava sheets,
12(5 SNAKE EIVEE PLAINS OF IDAHO. [BULL. 199.

The principal variations in the topography of the canyon walls, from 

Shoshone Falls westward, depend on the relation of the lava sheets to 

associated clays, sand, etc., interstratified with them. Where the lava 

predominates the canyon is narrow with precipitous walls, as in the 

portion of its course for about 15 miles below Shoshone Falls. When 

only a thin surface sheet of lava is present the canyon has flaring sides, 

margined above by a vertical rim rock. If two or more sheets of lava 

are present, with soft beds of considerable thickness between the adjacent sheets, two or more rim rocks similar to the higher one will 

occur, their strength depending on the thickness of the lava. If a 

sheet of lava separated from the highest sheet of the same nature by 

a thick deposit of soft beds is present, a broad outer canyon, with 

flaring sides, and a summit rim rock will usually be developed, in the 

bottom of which there will be a smaller, inner canyon. When, as 

most frequently happens, the lava sheets occur only on one side of the 

canyon, i. e., on the northern side, the characteristics just referred to, 

with numerous variations, are there present, while the other side is 

less definitely canyon-like and usually presents less Avell-defined topographic forms.

The slopes formed of soft material below the broken edge of a thin 

lava sheet are usually strewn with blocks of lava that have fallen from 

above, and may be completely sheathed with such talus (PL VII, A): 

The profiles of these slopes are sometimes concave" as when the talus 

is too thin to preserve the soft beds beneath and erosion curves are 

produced, but may be nearly straight when the slope of the talus is 

the predominant factor, or become convex when the material beneath 

is resistant and weather curves predominate.

The broken edges of thick sheets of basalt resting on soft deposits, 

especially if the latter are also thick, are apt to break away in larger

blocks than in the formation of a talus, and landslides result. Excellent examples of landslides of the nature just referred to occur for 

several miles on each side of Snake River above the mouth of Canyon 

Creek.

The principal features of the walls of Snake River Canyon, described 

in the last three paragraphs, it must be remembered, are such as are 

most pronounced and become accentuated owing to the prominent part 

played by certain special conditions, but many other variations occur 

which are not essentially different from those known elsewhere in the 

arid region, except in detail. There is one class of exceptional topographic forms, however, which becomes especially conspicuous in the 

wall of the Snake River Canyon, the like of which, so far as I am 

aware, has not been observed in other regions. I refer to certain 

remarkable alcoves or branches from the main canyon which are not 

due to the work of surface streams.
U. S. GEOLOGICAL SURVEY BULLETIN NO. 199 PL. XXIII

A. FAULT SCARP OF BASALT NEAR CLEFT, :LArl'J.

11. LITTLE CANYON, LOOKING SOUTH INTO SNAKE RIVER CANYON, IDAHO.
RUSSELL, j CHANGES MADE IN LAVA SHEETS AFTEE COOLING. 127

SPRING-FORMED ALCOVES ON THE SICES OF CANYONS.

At Blue Lakes, about 5 miles below Shoshone Falls, where the walls 

of Snake River Canyon are about 700 feet high, and nearly vertical, 

except for the talus lodged against their bases, there is a tributary 

cany on-like alcove in the north wall which is about 2 miles long, and 

about 2,000 feet across at the top and which heads in a semicircular 

amphitheater with vertical walls about 300 feet high. There is no 

stream entering the alcove from the surface of the neighboring plain, 

but springs discharging probably several hundred cubic feet of water 

per second boil up in the amphitheater at its head. One of the striking features in this alcove is the small quantity of talus at the bases of 

the bordering cliffs. This is most noticeable in the semicircular 

expansion of the alcove at its head. In the view of the Blue Lakes 

alcove presented on PI. XXIV some of the features referred to may

be recognized.

On the north side of Snake Elver Canyon, about 2 miles above the 

mouth of Salmon River, which comes into the Snake from the south, 

the canyon wall is again nearly vertical and about 300 feet high, and 

there are two side branches, known as Little and Box canyons. These 

are similar in all their leading features to the Blue Lakes alcove, arid, 

like it, are lateral openings from the main can}^on. They are also 

without surface streams entering them from the plain above. Box 

Canyon is approximately 3 miles long, and Little Canyon is perhaps a 

mile less in length. Each of these secondary canyons or alcoves has 

vertical walls about 200 feet high. There are comparatively small 

talus slopes along their sides and practically none at the base of the 

wall encircling their heads. At the head of each alcove there is again 

an immense spring. The stream issuing from Box Canyon has a volume of about 1,000 cubic feet per second, and the stream from Little 

Canyon is perhaps one-third as great. A view in Little Canyon looking out into Snake River Canyon is reproduced on PI. XXIII, B.

Malade River, Avhich is formed by the union of Big Wood and Little 

Wood rivers, in recent years has become dry in summer, owing to the 

demands made on its tributaries for irrigation. The river, as I was 

informed, was dry a few miles below where its two branches unite, 

late in August, 1901, but on crossing its canyon, where it emerges into 

Snake River Canyon, I found a roaring stream of clear water 8 feet 

wide and fully 4 feet deep discharging by estimate about 3,000 cubic 

feet of water per second. All of this water is contributed by springs 

in the lower 4 miles of the canyon. The main supply, as I have 

been informed by Mr. N. Uhrlaub, comes from a great spring which 

rises at the foot of a precipice in the canyon, and which causes a cascade in .the Malade when water comes from the upper part of its 

course in winter and spring.' The volume of the spring referred to is
128 SNAKE EIVEK PLAINS OF IDAHO. [BULL.199.

reported to be not less than 1,500 cubic feet per second. The canyon 

of the Malade throughout the lower 4 miles of its course is similar to 

the Box and Little Canyon alcoves, but its walls are higher, and during portions of each year, and perhaps continuously during certain 

years, it receives a stream at its head from the plain above.

; The water flowing from each of the four alcoves just described is 

clear, but has a bluish color and a slight opalescence, due to finely 

divided white silt-like material in suspension. It is this fact which 

has suggested the name for the small spring-fed lakes in Blue Lakes 

alcove. These pools and others fed by springs in and near the four 

alcoves referred to have white bottoms composed of clean white sand, - which is brought to the surface of the springs themselves.

The four side canyons or alcoves referred to thus have many similar 

features and without question have been produced by similar agencies. 

One conspicuous feature in each is a sheet of basalt from 200 to 300 

feet or more thick. No exposures of the material on which the basalt 

rests are known to me, but as the springs are bringing out white silt 

and fine white quartz sand it is evident that beds of similar material 

exist beneath the basalt.

The origin of the side canyons which receive no surface streams, 

such as Little and Box canyons and the one in which the Blue Lakes 

are situated, is plainly due to the action of the great springs which 

come out at their heads. The lower portion of the canyon of. the 

Malade has a like history, modified by the fact that a surface stream 

is also concerned in the work. The great springs undermine the 

basalt by removing the soft material on which it rests. Thus blocks 

of the usually more or less vertically jointed rock break awa}7 and fall 

into the spring, and sooner or later sink into the soft bed beneath, as 

the emerging waters remove the silt and sand from beneath them,

By this process vertical walls without talus slopes are produced. This 

process continuing, the cliff recedes, leaving a side cut or alcove in 

the wall of the main canyon, which becomes lengthened into a lateral 

canyon. The process would seem to be cumulative, as the farther the 

head of a side canyon receded the greater would be the tendency of 

the escaping waters to converge toward it. The marked tendency to 

an enlargement into an amphitheater, observable especially at the 

head of the Blue Lakes alcove, is apparently due to this cause.

It is to be expected, under the hypothesis just suggested, that as the 

head of a spring-formed alcove recedes the wall formed would be 

always vertical and kept fresh in appearance by the fall, from time to 

time, of portions of its face; while the sides of the older portion of 

the cut produced would become more or less encumbered with talus. 

The truth of each of these inferences is abundantly sustained by 

observation. The precipices partially encircling the great springs at 

the heads of the alcoves visited are not onlv vertical and either without
U. S. GEOLOGICAL SURVEY 

LAKE ALCOVE, LOOKING bOUTH INTO SNAKE RIV
RUSSELL.] SPEING-FOBMED ALCOVES IN CANYONS. 129

or nearly free from talus, but are so fresh in appearance that the last 

blocks to fall from them must have been detached during the past few 

years, while the sides of the canyons through which the great springs 

discharge their waters have at their bases talus slopes (PL XXIII) 

which extend well toward the centers of the gulf between them. The 

Blue Lakes are retained by darns composed of talus blocks.

In considering the origin of alcoves of the type of Little Canyon, 

etc., the question arises, Why should not landslides be caused by the 

undermining of thick sheets of basalt by springs in the same manner that a river cuts under the border of a similarly .thick sheet of 

resistant rock? The answer to this query is that the fall of individual 

blocks of .comparatively small size, so as to form a talus, and the 

breaking away and descent of large masses, as in landslides, are in 

reality but extremes of a single process. Large blocks of such dimensions as to be termed landslides are not caused to fall b}^ the undermining performed by springs, evidently because the action is too local. 

The fact that large alcoves are not more frequent along the side of 

Snake River Canyon, as at The Thousand Springs, etc., where water is 

pouring out, is because only exceptionally strong springs can undermine thick lava sheets so as to initiate and continue the process 

described when the other essential conditions are most favorable. At 

The Thousand Springs the water emerges from the open basal portion 

of a lava sheet and above a thick layer of compact tuff which stands in 

a vertical cliff, and no approach to the formation of an alcove is to be 

seen. Several of the smaller springs which come to the surface in the 

canyon wall from beneath relatively thin sheets of lava, as in the vicinity of Hagerman, are situated at the heads of reentrants in the canyon 

walls. These reentrants are of the same general character as the larger 

alcove, being produced by large springs, but the extension headward 

has been small. In these instances the water-bearing layer is cellular 

basalt and the beds beneath stratified clay.

The necessary conditions, then, for the production of large alcoves 

which have otherwise a generally straight alignment, and which 

furnish no surface tributaries to the stream in the main canyon, 

are the presence of a surface or superior sheet of compact rock of 

very considerable thickness, and beneath this a stratum of unconsolidated fine sand, silt, etc., of fully as great thickness as the overlying stratum, and an abundant water supply in the unconsolidated 

stratum. The conditions are still more favorable if the superior sheet 

of compact rock is vertical^ jointed. The initial step in the process 

is the escape of the water at some locus of discharge forming a spring 

sufficiently powerful to carry away the material composing the porous 

stratum. The necessitj^ for a thick bed of fine sand or other similar 

material beneath the can}7 on-forming layer is shown by the fact that 

blocks falling from the cliff's in order to form an alcove are not carBull. 199 02 9
SNAKE KIVEJR PLAINS OF IDAHO. [BULL. 199.

ried away, but are engulfed in the stratum beneath, space being furnished by the removal of the fine material by the spring. .

In the process now going on in the enlargement of the Blue Lakes 

alcove, etc., a portion of a thick stratum of sand is being replaced by 

a deposit of angular blocks of lava. Possibly the mode of origin of 

certain ancient breccias may here be indicated.

The spring-formed alcoves on the side of Snake River Canyon are 

unique topographic features, because the combination of conditions 

necessary for the production of such recesses or lateral cuts in the 

border of a plateau is of rare occurrence.

LOST KLVEHS.

In connection with the following brief account of a striking peculiarity in the hydrography of the Snake River Plains, the reader is 

invited to refer to the map forming PI. I. As there indicated, not a 

single tributary reaches Snake River from the high and rugged mountains lying west of its course between Malade River and Henrys Fork, 

a distance in a straight line of 200 miles. Several of the eastward - 

flowing streams which rise in the mountains referred to are of considerable volume and reach the margin of the lava-covered plain bordering 

Snake River, but fail to cross it. Examples of such streams, named 

in order from northeast to southwest, are Camas, Beaver, Medicine 

Lodge, and Birch creeks and Little Lost and Big Lost rivers. When 

the snow is melting each of these streams advances onto the plain for 

distances varying, in the several cases cited, from 10 to 50 miles, but 

shrinks back in summer and ends indefinitely soon after leaving the 

valley tracts. In certain instances, as in the case of Camas and Birch 

creeks and Little Lost and Big Lost rivers, the waters spread out on 

the marginal portion of the plain during the period of their greatest 

elongation and form shallow lakes. These lakes are ephemeral, however, and although renewed each spring, with one exception become 

dry each summer, leaving smooth mud plains or playas. The exception is furnished by Camas Creek, which expands to form Mud Lake, 

which fluctuates in area from month to month and when largest is 

from 40 to 50 square miles in area. It was dry in the summer of 1891 

and lower during the summer of 1900 than at any time during.the 

preceding nine years. In September, 1900, the bed of Camas Creek 

was dry for a distance of 20 or 30 miles adjacent to its distal extremity, 

although, as indicated by a well, there was an underflow beginning at 

a depth of 20 feet. Mud Lake was then shrunken so as to leave a mud 

flat from a few to several miles broad about its borders.

The streams just referred to emerge from valleys deeply filled with 

alluvial material and during high-water stages bring to the plain large 

quantities of material held in suspension or rolled along their bottoms. 

The coarser portions of this, the "visible loads" of the streams, are
KUSSKLL.] LOST K1VEKS. 131

deposited in the .mouths of the tributary valley a and on the border of 

the great plain, so as to form alluvial fans; 'while the finer portion is 

carried farther, and, in case of the stronger streams, deposited principally over the bottoms of temporary lakes. The weaker streams, 

which disappear either by evaporation or by percolation, deposit the 

fine sand and silt they bring- down from the mountains in a broad fringe 

about the outer margins of their low, widely expanded alluvial fans. 

In these several ways an attempt is being made, as one may say, to 

upgrade the lower portions of the stream channels, so as to enable the 

waters flowing down them to cross the plain. The principal reason 

why the streams have clone this is because their water supply is insufficient. But, if properly graded water-tight channels could be provided there is no doubt but that the stronger streams, such as Cam as 

Creek and Big Lost River, would be enabled to reach Snake River during the time the show is melting on the mountains from Avhich they 

flow and perhaps live throughout the summer. In addition to the light 

rainfall, therefore, other adverse conditions must be present. Chief 

among these is the fact that the lava covering the plain across which 

the streams naturally tend to flow is not smooth and levej as it appears 

to be when seen from a distance, but rough, irregular, and undulating.

The waters are ponded, and before they can accumulate in sufficient 

volume to overflow the obstructions and continue on their course their 

expansion to form lakes leads to an increase in evaporation, which at a 

certain stage equals the inflow. That is, the inflow is spasmodic, but 

evaporation continues so long as the lake basins contain water, although 

fluctuating with temperature, strength of the wind, etc., and the quantity of water delivered to the lake basins each year, or during a period 

of several years, is all evaporated or lost by percolation. Allowing 

for the conditions just mentioned, however, there is still evidence that 

the popular belief that the waters sink into the lava and that the 

streams are "lost" beneath the surface is well founded. When the 

waters of Little Lost River are expanded so as to form a lake, I have 

been informed by observant residents of the region that there is at a 

certain stage an escape through fissures.

The surface portions of the lava sheets covering the plains are 

broken and jointed, so that water if spread over the land would immediately sink from sight. This is indicated also by the fact that few if 

any surface rills or brooks are formed on the plains during rains or 

when their covering of snow is melting, but this may be due to the 

absorbent nature of the soil. In order that streams may cross such a 

surface it is necessary that the openings in the rocks should first be 

closed. The streams are active in this direction, as is to be seen where 

they are spreading out alluvial fans and silting up lake beds, but the 

task is not far advanced. The processes now in action, given time 

enough, will lead to the upgrading of the plain so as to fill the cavities
132 SWAKE KIVER PLAINS OF IDAHO. [Kuuul99.

and fissures in the lava and enable the stronger streams to advance 

over it and possibly to reach Snake River. As is well known, a stream 

charged with sediment will seal the openings in its channel, even if 

flowing over a thick stratum of bowlders and loosely compacted stones, 

and form for itself an aqueduct through which it can flow witrhout material loss by percolation. Admirable illustrations of this process are 

furnished by the "lost rivers," but the difficulties to be overcome are 

great, and the task undertaken is not far advanced.

The sources of supply of the large number of strong springs referred 

to on a previous page, which gush out from the north wall of Snake 

River Canyon between American Falls and Bliss, are the streams which 

come from the mountains to the north and are "lost" on reaching the 

plains, together with the rain and water furnished by melting snow 

which comes directly to the broken surfaces of the plains themselves.

The environment of the "lost rivers" which, coming from the west, 

reach the Snake River Plains to the easjt of the Malade but fail 

to pass them, is not conspicuously different from the combination 

of conditions influencing the lives of the streams to the west of the 

Malade which do reach the Snake during a portion of each year, 

except as noted below. To the east of the Malade the lava sheets 

forming the surface of the plains are in part of recent origin and a 

sheet of soil has not as yet been spread uniformly over them, and 

besides, they are still in the position in which they were spread out; 

that is, their surfaces, although rough, are essentially horizontal. -To 

the west of the Malade, however, the lava sheets are comparatively 

old, are covered quite uniformly with soil, and besides have been bent 

into a broad, gentle trough, the axis of which runs in a generally 

east-west direction. The streams from the mountains to the north 

emerge upon a smooth plain, which is tilted gently in their direction

of flow, and which in a large number of instances they have been 

enabled to cross. Another favorable condition is that the mountains 

northwest of Mountain Home are composed largely of granite, which 

furnishes an abundance of material of such size that it can be transported \)y even weak streams, and which are then in. a condition to 

upgrade their course across the plain.

An important factor, however, .which determines the existence of 

lost rivers is climate, as is shown by the fact that none of the streams 

to the west of the Malade until Boise River is reached, in spite 

of their favorable environments, are perennial. The}^ all shrink in 

summer to such an extent that they barely emerge from their mountain valleys. The Malade is the only stream in the whole of southern 

Idaho from Henrys Fork, within 12' miles of the west boundary of 

the Yellowstone Park, to the Idaho-Oregon line, a distance measured 

along Snake River of fully 450 miles, which, rising in the mountains 

to the north, reaches that river in summer. Even the Malade, on
BUBSELL.] UPGRADING STREAMS. 133

account of the demands made on its tributaries for purposes of irrigation, how becomes dry for a period each year.

The marked exception furnished by the Malade to the prevailing 

character of the neighboring streams, when the influence of irrigation is not considered, at once suggests that some exceptional circumstance favors it. The reason for this exception is not difficult to 

discover. The Malade is formed by the union of Big Wood and Little 

Wood rivers. Each of these streams has been turned aside in recent 

times by a lava flow, and the two caused to unite. By their union 

they form for the region in which they flow an exceptionally strong 

river. The fact that each of the main branches of the Malade has 

been turned aside from what we are justified in assuming would be its 

natural course is at once suggested by an inspection of a map on 

which the drainage of southern Idaho is shown. On leaving the

mountains they turn abruptly south westward instead of continuing

southeastward, as would seem to be their natural course. The reason 

for this in the case of Little Wood River is the presence of a recent 

lava flow in the mountains across the mouth of the valley down which 

the stream flows. In the case of Big Wood River the lava stream 

from Black Butte filled its former channel and caused it to take a new 

course. Had it not been for these "accidents" each of the streams 

would have maintained its independence, and most probably would 

have been "lost" on the plains in the same manner as in the other 

instances cited.

The region that the two streams just referred to would have crossed 

in order to reach Snake River had thej^ not been turned aside has as 

yet not been closely examined, and it will be of interest to discover 

whether abandoned channels or alluvial deposits occur there to confirm 

the hypothesis of recent deflections here presented.

UPGRADING STREAMS.

In the case of the "lost rivers" of the Snake River Plains, instances 

are furnished of upgrading in which the process has not advanced far 

enough to permit the streams engaged in the work to cross the flat 

tract they invade and reach larger drainage channels. On the east 

side of the same flat region, however, there are numerous streams 

that have been more successful. Examples of this are furnished by 

the South Fork of Snake River, the Blackfoot, and Portneuf rivers, and 

probably other streams, which have their sources in the mountains of 

southeastern Idaho and adjacent portions of Wyoming and flow northwestward. There are no "lost rivers" in this region, although man}^ 

of the smaller streams become dry in summer. The reason for this 

contrast between the streams reaching the Snake River Plains from 

the north and those coming in from the southeast is twofold the 

former are not only smaller as a rule than the latter, but have a far
134 SNAKE RIVER PLAINS OF IDAHO. [BULL. 199.

broader tract of flat land to cross before reaching the main waterway. 

The streams from the southeast, corning from high mountains, are 

well supplied with material in suspension, and have been enabled to 

upgrade their courses across the comparatively narrow tract of flat 

country, and 'thus reach the main channel of discharge without being 

ponded. Perhaps the best illustration of this, and the only one which 

can here be noticed, is furnished by the South Fork of Snake River.

As may be seen on inspecting the map forming PI. I or better, the 

General Land Oitice map of Idaho, from which it was in the main 

compiled the South Fork on emerging from the mountains, to the 

east of Market Lake, splits up into a number of distributaries, which 

join the North Fork independently. The meaning of this is that the 

South Fork, being overloaded, has buildup an immense alluvial fan on 

the border of the Snake River Plains, on which it subdivides. Theconditions, as previously remarked, are unusually favorable for irrigation, and the natural subdivision of the river has been increased in 

recent years by the construction of canals. The alluvial fan built by 

the South Fork has not only.deflected the North Fork and caused it to 

make a curve to the west, but has checked its flow and compelled it to 

drop the material it was previously enabled to carry and so assist in 

forming a broad alluvial deposit. The North Fork has been partially 

dammed by the material deposited in its course, and now widely overspreads its banks during high-water stages. This tendency to form a 

lake was greater before the construction of extensive irrigating Avorks 

and railroad embankments than it is now, for a lake was formed each 

year, which during certain periods was perennial. This Market Lake, 

as it was named early in the exploration of Idaho on account of the 

abundance of game in its vicinity, in now prevented from becoming 

flooded, and its bed is under cultivation.

Miich more space could be, given to the study of the upgrading 

being carried on by the streams that join the Snake from the southeast, 

but enough has probably been stated to illustrate the marked contrast 

that exists between them and the "lost river" on the western portion 

of the basin which they enter. The conspicuous difference in these 

two representative instances, it will be seen, is one of degree. Of the 

many factors involved in a river's development, a few or perhaps some 

definite one controls the result in certain instances, while others become 

prominent and perhaps assume the lead in other cases.

In reference to the' process of upgrading, it will be rightly assumed 

from the statements already made that all the streams emerging from 

the mountains onto the lava-formed portions of the Snake River Plains 

are now or at some time in their history have been engaged in spreading out gravel, sand, silt, etc., over the surfaces of the nearly flat lava 

sheets that they have to cross. In this manner much of the soil of 

the plains has been formed.
HCSSELL.] ALLUVIUM.' 135

SOILS.

As was stated in the introductory portion of this paper, the Snake 

River Plains are, as a rule, soil covered. The principal exception is 

where the recent lava is present. Where lava sheets of considerable 

antiquity are still at the surface, however, their roughness, especially 

the pressure domes and ridges which occur upon them, is not always 

concealed by the nearly universal sheet of fine debris in which the 

desert shrubs arc rooted.

ALLUVIAL SOILS.

One source of the soil covering the lava sheets has already been 

described, namely, the alluvial deposits made by streams flowing down 

from the mountains. About the border of the plains, and extending

out for many miles toward their central part in certain instances, the 

surh'cial covering is composed of coarse material of the same lithological character as the rocks forming the neighboring mountains. A 

gradation from coarse to fine is easily traced as one leaves the mountains and journeys out upon the plain. In making such a journey it 

will be noticed that at first the alluvial fans, stream terraces, etc., are 

pronounced, but as one proceeds they flatten out and become more and 

more indistinct, and at a distance, in general, of 8 or 10 miles from the 

bordering upland the plain is flat and has an even surface of soft 

yellowish-white silt-like material, broken only by occasional crags of 

basalt, or the summits of pressure ridges. Far from the channels of 

streams, and where even the courses of the ephemeral distributaries 

of wet-weather creeks and brooks are no longer distinguishable, the 

light-colored soil continues, and not infrequently and over continuous 

areas embracing several hundred square miles forms an even, unbroken 

surface. The origin of the soil at localities distant from all stream 

channels is the most interesting problem that this surface covering 

presents.

The surface of the plains at a distance from the mountains, and from 

the channels of streams, inclusive of those dependent on unusually 

heavy rains, presents two'quite well-marked characteristics. To the 

west of Malade River the broad, seemingly level interstream spaces 

are smooth and have a gentle downward inclination to the south. It is 

evident that if the ephemeral streams from the mountains to the north 

had sufficient volume they might easily continue across this space, 

which varies in width from 10 to 20 or more miles, and deposit fine 

sediment upon it. To the east of the Malade, and over nearly all of 

the eastern half of the Snake River Plains, the surface is undulating, 

and there is no direction in which surface water could flow for many 

miles without being ponded. This rolling surface, however, is covered 

with a sheet of soil similar in its physical characters to that forming
136 SNAKE RIVER PLAINS OF IDAHO. [BULL. 199.

the surface of the smoother plains lying farther west. Although 

there is a suspicion that the soil on the smooth plains, especially when 

their surfaces are inclined in the direction in which streams from the 

mountains would flow if precipitation were sufficiently abundant, was 

deposited b}r the distributaries of ephemeral streams, it is evident that 

the rollingplains could not have been covered with a sheet of fine material 

in this manner. As is explained below, the soil on the rolling plains, 

which have in fact the typical aspect of rolling prairies, is decidedly 

different from the rocks beneath, and, as is plainly apparent, has not 

been formed by the disintegration and decay of the underlying basalt. 

It has manifestly been deposited on the lava from above, and must 

therefore have been spread out beneath a lake which occupied the 

Snake River Basin at a recent date, or else it was laid down under conditions essentially the same as those now existing. That a lake has 

not been present over the greater part of the lava-covered region 

lying east of the Malade since the surface lava sheets were spread out 

is shown by the absence of beach lines and other similar phenomena. 

The soil must therefore have been deposited from the atmosphere.

J&OLIAN SOILS.

One method of studying the nature of soils is to sift them and thus 

separate the grains of uniform size. The results obtained in this 

manner from two samples of soil from the Snake River Plains are 

presented below. No. 1 is from a locality about 8 miles southeast of 

Shoshone Falls and is a representative of the soil covering the smooth 

plains. No. 2 is from a locality about midway between Arco and Big 

Butte, where the surface is rolling and has never been crossed by 

streams. Each sample was taken about 1 foot below the surface. No. 3 

is a sample of the lacustral deposit which covers a great area in the

northern part of Owyhee County, and is introduced here for comparison. It will be referred to later.

Mechanical analyses of soils and lacustral deposit from Snake River Plains.

Retained on a 20-mesh sieve ....... ..............

Retained on a 50-mesh' sieve .....................

Passing through 200-mesh sieve ..................

No. i.

Per cent. 

0.0

5.0

6.5

4.5

82.8

No. 2.

Per cent.

5.7

4.0

5.5

8.5

76.0

No. 3.

Per cent. 

0.0

4.5

10.5

6.0

79.0

"Number of meshes per linear inch.

The material retained on a 20-mesh sieve, in the case of sample No. 2, 

contains about 5 per cent of easily recognizable vegetable fibers, and 

in the fractional parts of each sample coarser than that which passed
MJSSELL.J ^OLIAN SOILS. 137

through a 200-rnesh sieve similar vegetable fragments are present. 

Probably 3 to 4 per cent of each sample consists of vegetable debris. 

The soil represented by sample No. 1 is of a light-yellowish, nearly 

white color, and resembles the loess of the Mississippi Valley and 

other regions. The particles composing this sample, larger than those 

passing through a 200-mesh sieve, when examined with the aid of a 

microscope, are seen to consist of small grains loosely united and well 

rounded, probably on account of the slight attrition necessary' to 

cause the material to pass through the sieves used. When these 

rounded grains are lightly rubbed in water, they immediately disintegrate. The same result is attained by placing them in weak hydrochloric acid, the spontaneous separation being accompanied by a brisk 

effervescence. The residue obtained after treating with acid, when 

examined under a microscope, is indistinguishable from the grains 

composing 82.8 per cent of the original sample, which pass through a 

200-mesh sieve. The coarser particles are thus shown to be aggregations of the finer grains present, loosely cemented by some carbonate, 

probably of calcium. The grains which pass through a 200-mesh 

sieve, as well as those obtained by treating the larger particles present 

in the original sample with acid, when examined under a microscope, 

are seen to be angular and subangular and mostly without color. 

From their appearance, resistance to acids, and other tests, they have 

been shown to be almost entirely grains of quartz. No shreds of 

glass, such as are characteristic of volcanic dust, were observed. 

Thus, as indicated by a mechanical analysis, the soils are composed 

essentially of exceedingly fine quartz sand, with a minor amount of 

some cementing material, probably calcium carbonate. This conclusion is sustained by a chemical analysis, the results of which are here 

presented.

Chemical analysis of soil from near Shoshone Falls, Idaho.

[Analyst, W. P. Hillebrand.]

Per cent.

Silica, Si02 .............................................................. 52. 43

Alumina, A12 08 ..................:......-...............-...-............ 7.10

Ferric oxide, Fe203 ....................................................... 2. 63

Titanium dioxide, Ti02 ................................................... .38

Manganous oxide, MnO.................................................. Trace.

Calcium oxide, CaO ..................................................... 14. 60

Potassium oxide,KaO ................................................... 1.7

Sodium oxide, Na20 ....................................................... .93

Magnesium oxide, MgO.................................................. 2. 93

Carbon dioxide, C02 ..................................................... 12.40

Phosphoric oxide, P2 05 ...........................................'....... .20

Water, H2 0 ..................................................:.......... 4.96

Total............................................................. 100. 31
138 SNAKE RIVER PLAINS OF IDAHO. [BULL. 199.

Judging from both the mechanical and chemical analyses just given, 

it seems that the soil consists essentially of exceedingly fine quartz 

sand, to which a small percentage of calcium carbonate, together with 

some vegetable matter, has been added. One interesting result of the 

chemical analysis is the small amount of sodium found.

The soil represented by sample No. 2 is brown in color. This is due 

in part to organic matter, but does not wholly disappear when a sample is heated to redness. The particles which will not pass through a 

200-mesh sieve are aggregations of smaller grains, but are not readily 

disintegrated by rubbing and do not fall to pieces when treated 

with hydrochloric acid, and besides there is but slight effervescence 

when acid is used. The material passing through a 200-mesh sieve 

and that obtained by the partial breaking up of the coarser particles 

when rubbed appear under the microscope to be about the same as the 

grains composing sample No. 1, but are much more frequently colored. The larger part of the grains consists of quartz, but a considerable number are dark colored or opaque and indeterminate. Judging fr.om these facts, the soil represented by sample No. 2 consists 

mainly of fine quartz sand, colored and in part cemented into grains 

by some substance not readily soluble in acid, and, as indicated by 

qualitative chemical tests, consisting probably of ferric oxide. The 

opaque indeterminate grains are possibly volcanic lapilli.

Near each of the localities where the samples referred to above 

were taken, as is the case throughout the soil-covered lava sheets 

beneath the Snake River Plains, there is an abrupt and conspicuous 

change from the soil to the lava and not a gradual transition from one 

to the other. It is evident from this, as well as from the mechanical 

and chemical analyses given above, and the composition of the lava, so

far as known, that the soil is not derived, to an appreciable extent,

from the rocks on which it rests. In many sections seen the soil is 

essentially homogeneous from top to bottom, excepting that much 

more organic matter, usually in the form of readily recognizable vegetable fibers, is present at the surface than at a depth of a few feet. 

Also, as previously stated, the soil mantles both the smooth and the 

rolling portions of the plains, and occurs also on the sides and summits of ancient lava craters.

Judging from all the facts in hand, it is evident that the fine, usually 

light-j^ellow soil covering the Snake River Plains at a distance from 

the mountains is inanity and essentially a dust deposit laid down by 

the wind. The dust is derived to some extent from the mountains, 

.where naked cliffs, bare talus slopes, etc., furnish material for wind 

transportation, but of more importance is the fine sediment deposited 

by ephemeral streams which spread out on the marginal portions of 

the plains and leave all of the debris brought by them from the mountains. Another and possibly the source of the most abundant supply
RUSSELL.] JLOLIAN SAND. 139

is the bare surface of the extensive lacustral deposits in southwestern 

Idaho. The prevailing- winds, which are westerly, on crossing- these 

lake beds, cut as they are into bad lands: become charged with dust, 

which is carried eastward and finally deposited. That much of the 0eolian sand was derived from this source is also indicated by a comparison 

of it with the material forming- the lake beds. A characteristic sample of the finer of the lacustral deposits, when subjected to a mechanical analysis in the manner already described gave the results presented 

in column No. 3 of the table given on page 136. As respects the size 

of the constituent particles, it will be seen that there is no conspicuous 

difference between the soils numbered 1 and 2 and the lacustral deposit. 

When the latter is examined under a microscope it is seen to be composed 

largely of fine angular and subangular grains of quartz sand, identical 

with those composing the principal part of the soils; the portions 

caught on 50- and 100-mesh sieves also are loosely cemented fragments 

of the same material, as in the case of the soil sample No. 1. This similarity is, in -fact, so close that it suggests another hypothesis, and one 

which I considered and abandoned while in the field, namely, that 

the waters of the Pliocene lake which occupied the western part of the 

Snake River Plains extended far eastward, and that much of the fine 

yellow soil to the east of Malade River is a remnant of the sediment 

deposited in it. To what extent the soil in question is realty lacustral 

sediment not removed and redeposited by the wind is difficult to determine, as the passage is indefinite from the area where lacustral conditions were clearly present at the west to the area at the east where there 

is an absence of evidence of the former presence of a lake after the 

surface lava sheets were spread out.

No doubt much of the dust derived from the lake beds referred to, 

and from the fine alluvial deposits is carried far beyond the borders of 

the Snake River Plains, but it is only in situations where other deposits 

are not being formed and where freedom from removal by rain wash is 

assured that the characteristic jeolian soil can be expected to occur. 

The grasses, sagebrush, etc., growing on the plains serve to entrap the 

dust and preserve it from being again removed by the wind.

In addition to the sources of supply of dust cited above, the fact 

needs to be borne in mind that volcanoes of the type, of the Cinder 

Buttes, Market Lake crater, Kuna Butte, etc., contributed large quantities of volcanic dust and lapilli to the surface covering of the neighboring portions of the plains. Where this material is present in considerable quantity the soil is brown, but when neolian dust or lake 

beds predominate the soil is a characteristic light yellow, and is frequently nearly white. It is the fine, homogeneous, light-yellow soil 

that is generally present on the broad plains at a distance from the 

mountains.
140 SNAKE RIVEB PLAINS Otf IDAHO. [MULL. 199..

SAND DUNES.

In general, sand dunes are absent from the Snake River Plains, but 

at a few localities some notable examples are present. In Snake River 

Canyon, to the south of the river and about 8 miles below Glenns 

Ferry, there are sand drifts of considerable size, which are conspicuous 

on account of their gray color, smooth bare slopes, and undulating 

crest lines. Again, in the extreme northeastern portion of the plains, 

between Camas Creek and Henrys Fork, there is an area of many 

square miles occupied by drifting sand which has partially buried a 

range of hills known as the Sandhill Mountains. This great deposit 

of wind-blown sand was visited by F. H. Bradley" in 1872, who 

described it as reaching a height of 250 to 300 feet on the hills and 

forming a barren belt about their sides and bases. To the west of the 

hille it covers a tract of country several miles wide, some of the drifts 

being from 100 to 150 feet high. This interesting region still awaits 

careful study.

In many localities on the Snake River Plains where conspicuous 

sand drifts do not appear there is evidence that considerable surface 

material, mostly quartz sand, is traveling in the direction of the prevailing winds. The roads are sometimes rendered impassable by 

these small dunes. The manner in which the sagebrush checks the 

force of the wind and causes sand, drifts to start suggests that if a 

tract about 100 feet wide should be cleared of brush on each side of 

a road, so as to give the winds a.clear sweep, the sand obstructions 

would be removed.

It is a noticeable fact that the well-defined dunes on the Snake River 

Plains are composed of sand from which practically all fine particles 

have been removed. The dust does not collect in drifts and ridges to 

a notable extent, 'but is deposited as an even sheet which, although 

thickest in the depressions, occurs on hillsides as well. The reason 

for this difference in the manner in which dust and sand is laid down 

is not apparent and would be an interesting subject for investigation.

Along the border of flood plains of streams tributary to Snake 

River, and also on the surfaces of abandoned flood plains now forming 

terraces along the larger stream, water-laid soils occur. They are 

coarse or fine, according to the strength of the currents to which their 

deposition is due. Usually a variety of rock fragments is present, as 

along Snake River, but in the case of small streams there is less 

diversity and the debris is of the same character as the rocks forming 

the region whence the streams flow. Between Mountain Home and 

Boise the flood plains of the streams flowing from the mountains to 

the north are composed of angular granitic sand. Far out on the plain, 

where ephemeral streams expand and at times form playa lakes, the

« Sixth Ann. Kept. U. S. Geol. and Geog. Surv. Terr., 3873, pp. 211-212.
 RUSSELL, j' CHEMICALLY FORMED DEPOSITS. 141

surface is covered with tine yellowish silt, composed almost entirely of 

fragments of quartz, and not distinguishable from true Eeolian soil.

 - RESIDUAL SOIL'S.

On the mountains of southern Idaho and on the steptoes which rise 

through the lava of the Snake River Plains there is usually an abundance of tine material forming a soil mantle which agrees in the nature 

of its constituent fragments with the rocks on which it rests. In many 

instances there is a gradation from fine soil, with occasional angular 

rock fragments into the solid rock beneath. These are typical examples of residual soils.

SUMMARY.

The soils of southern Idaho are of two classes sedentary and transported. Of the transported soils, there are again two principal subdivisions wind deposited and water deposited. Of the wind-carried 

or teolian soils there are two principal varieties, one consisting mainly 

of tine quartz sand and the other of volcanic dust and lapilli. Of the 

water-deposited soils there are again two varieties those laid down in 

lakes, principally in southwestern Idaho, and those deposited by 

streams. The principal part of the soil covering the plains at a distance from the mountains and outside the canyons is of seolian origin, 

and consists mainly of fine quartz particles.

CHEMICALLY FORMED STJBAERIAL DEPOSITS.

A. surface efflorescence of alkaline salts, etc., is unknown on the 

Snake Elver Plains. In a few localities, however, on the flood plains 

of streams as, for example, along the border of Snake River to the 

west of Shoshone Falls the nature of the plants indicates an alkaline 

soil, and in a few instances white surface incrustations are formed 

during the summer season. These incrustations, as is well known, are 

due to surface evaporation. The water from below rises, owing to 

capillary attraction, as the surface is dried, and being in turn evaporated, leaves its contained saline matter. Without attempting an 

extended discussion in this connection, it may be stated from observations made in Idaho and elsewhere that soils do not become alkaline 

if well underdrained; but if there is an abundance of subsoil water it 

will be drawn to the surface during long-continued droughts and evaporated, leaving the salts it previously held in solution at the surface. 

The obvious suggestion furnished in this connection by natural conditions is that irrigated land should be well underdrained.

Although what are commonly termed alkaline incrustations are 

absent from the soils occurring on the Snake River Plains, there is an 

analogous substance frequently present. I refer to the white deposit 

to be found almost everywhere on the under sides of loose atones or in
142 SNAKE KIVEE PLAINS OF IDAHO. [BOLL. 199.

the upper portions of basaltic outcrops when covered with loose stones, 

sand, soil, etc. These incrustations are perhaps most commonly only 

an inch or two thick, but at times have a depth of several inches, and 

not infrequently a layer of rock fragments 6 to 8 or more feet thick 

will be solidly cemented with similar material, forming a breccia. In 

some localities the surface portion of a bed of pebbles is similarly 

cemented into a conglomerate. Less frequently the white deposit is 

largely free of other material, visible to the eye, and forms a subsur-. 

face layer of hard, yellowish-white rock 3 to 4 or more feet thick. In 

certain instances, again, the cavities in the surface portion of a sheet 

of lava will be filled with similar material.

The most striking peculiarity of these deposits, aside from their white 

or yellowish-white color, is their occurrence just below the surface, and 

their absence at a depth of a few feet. As they occur on loose stones, 

and in surface deposits generally, it is obvious that they are of recent 

origin, and are probably still forming. This material, as shown by 

partial analysis, consists essentially of calcium carbonate, and agrees 

both chemically and in mode of occurrence with similar deposits widely 

distributed in arid regions.

As to the way in which these lime deposits are formed, it is evident 

from their mode of occurrence, composition, etc., that they are of the 

nature of efflorescences. Rain water on percolating downward and 

more or less completely saturating the soil and upper portion of the 

rocks beneath is drawn upward again by capillary attraction as the 

surface dries. Why the deposit formed should consist principally of 

calcium carbonate is less clear, but the. fact seems to be due to the 

removal and carrying to a distance of the more soluble salts during 

the downward passage of water. The lime incrustations occur where 

there is free underdrainage, and the water drawn to the surface is the 

portion supplied by the occasional rains, which was absorbed by the 

rocks. The lime deposit is thus washed during each rain and a part, 

no doubt, removed, but in. arid regions a residue remains. Similar 

incrustations occur, especially in gravel deposits in humid regions, but 

they are thin and by no means of as common occurrence as in arid 

regions. There is thus a delicate balancing of conditions: With slack 

underdrainage, alkaline efflorescences are formed when surface evaporation is active; with free underdrainage, the more soluble salts are 

removed, and if surface evaporation is active, lime incrustations are 

deposited; with more abundant rainfall and less surface evaporation, 

all the material dissolved by percolating waters is carried away.

That the lime deposits referred to are derived in part from the soil 

is shown by the presence of cemented grains, as has been described in 

connection with the two soil samples, of which mechanical analyses 

have been given. In fact deposits of lime 3 or 4 feet thick, which 

seem to be homogeneous throughout, when digested in acid leave a
HUSSEM..] CHEMICALLY FORMED DEPOSITS. 143

residue consisting of tine grains of quartz sand, like that composing 

the bulk of the aeolian soils. In such instances it seems that the 

deposit formed has become so great that the fragmental character of 

the subsoil is obscured and it appears to be a compact, homogeneous 

bed of lime.

Not all of the lime deposited as a surface incrustation, however, 

comes from the soil. The cavities in the outcrops of basalt are frequently filled with similar material, as well as the spaces between 

blocks of basalt where no soil or but very little is .present. Much of 

the lime in such situations must have come from the basalt itself.

An interesting result of the concentration of lime near the surface, 

suggested by the occurrence of loosely cemented kernels and sand 

grains in the samples mechanically analyzed, is that by this process 

the soil is rendered more resistant to wind erosion, and therefore has 

a greater tendency to remain in place. The chemical precipitates 

thus assist vegetation in holding the dust which is spread over the 

land by the wind.

The surface incrustation just described is sometimes in sufficient 

abundance to be of commercial importance, and would yield a good 

lime on calcination, but would probably in all cases contain considerable quantities of sand or rock fragments. Unless these foreign 

bodies Avere in considerable abundance, however, they would not 

detract from the value of the lime for all purposes for which it is 

ordinarily used.

The deep-blue film described on a former page as occurring on the 

surface of one of the less recent lava Hows among the Cinder Buttes 

may here be referred to as being due to the process just considered. 

The blue substance is apparently of the nature of a "desert varnish," 

and owes its presence on the surface of the lava to the evaporation of 

water drawn from within the lava itself. The evaporation of the 

water has seemingly brought about a chemical precipitation of some 

of the material leached out of the lava and produced a deposit that is 

practically insoluble in water and hence is not removed by rain. By a 

similar process the upper surfaces of many of the millions of smooth 

cobbles of quartzite strewn over the surface of the lake beds in the 

northern portion of Owyhee County have been rendered dark yellow 

or brown and occasionally black. This is also a desert varnish, which 

no doubt is due to a precipitation of salts of iron or manganese on 

the upper surfaces of the stones; their lower surfaces are not "varnished."

It thus appears that two varieties of surface deposits resulting 

from the same general process must seemingly be recognized; one 

produced below the actual surface exposed to the sky and the 

other on the exposed surface. The deposits produced below the 

surface, in many instances at least, consist of substances (most
144 SNAKE K1VEE PLAINS OF IDAHO. [BULL. 199..

frequently calcium carbonate) which are sparingly soluble and which 

most probably, owe their accumulation to direct precipitation of 

material previously held in solution, while the deposits produced 

on exposed surfaces result from chemical precipitation and are not 

dissolved by beating rain. These two varieties of surh'cial deposits, 

due most conspicuously to the action of atmospheric agencies, frequently occur together, but the most characteristic examples are 

found in separate localities. The far-reaching process here touched 

upon, by which a concentration of sparingly soluble substances is 

brought about on rock surfaces or in their surficial portions while 

more soluble substances are carried away in solution, produces various changes dependent on the resultant, so to speak, of the several 

conditions or agencies involved. Not only do soils and flat-rock surfaces experience the changes referred to, but talus slopes and the faces 

of precipices are similarly acted on. In some instances along the border of the canyon of Idaho the aprons formed of dislodged fragments 

at a depth of a foot or two below the surface are firmly united with a 

calcareous cementing material, which includes dust particles. The 

faces of bold escarpments of tuff, consisting largely of fragments of 

glassy basalt, which occur on each side of Snake River from 1 to 2 

miles above the mouth of Salmon River exhibit a surface hardening 

which has led to conspicuous changes through the erosive action of 

dust- and sand-charged winds. The resistant surface has been broken 

in many places, and the softer material beneath scooped out so as to 

form alcoves and grotto-like recesses of various shapes and sizes. 

The appearance of the rugged grotto cliffs, as they might be termed, 

is most peculiar and interesting. 

Possibly a suggestion in reference to the wide influence of the process

of subaerial precipitation just referred to may not be out of place.

The formation of subsurface deposits, desert varnishes, etc., depends, 

as has been stated, on atmospheric conditions, and occurs, as might 

easily be shown, on a large variety of rocks. Probably there is no 

rock that is sufficiently resistant'not to yield to the action of percolating water and, under the requisite climatic conditions, become hardened 

at the surface. The marked difference in results produced in arid and 

humid climates has been referred to. . In arid climates absorbed water 

is drawn to the surface on account of capillary attraction induced by 

surface evaporation, and precipitation results, but when there is free 

underdrainage the more soluble portions of such precipitates are 

removed in solution. In humid climates all the material dissolved out 

of the rocks is norrnalty carried away in solution, and rock decay 

progresses with comparative rapidity. In regions having an arid climate, as is well known, rock decay progresses slowly, and the principal 

method by which denudation is initiated is rock disintegration, or the 

breaking of the rocks into fragments through the influence of changes
HUSSELL.] EECENT EROSION OF SOILS. 145

of temperature, freezing of absorbed water, etc. The conspicuous 

differences resulting from the same process when the conditions are 

varied, so frequently exhibited in the delicate adjustment observable 

throughout nature, are here well illustrated. Under humid climates 

rock solution leads to widespread and frequently deep rock decay, 

and surface terranes are rendered soft and readily crumble. The ultimate result, so far as most rock species are concerned, is a reddish clay 

or terra rossa. Under an arid climate most rocks become hard at the 

surface and not only do not crumble on account of the removal of 

material in solution, but by its reprecipitation at or near the surface 

are rendered resistant to mechanical agencies, such as the wind, which 

tend to wear them away. The colors of the rocks are not generally 

conspicuously altered by this process, and the color of the fragmental 

products are such as are inherent to the parent rocks. The soils are 

light colored, usually light yellow, and terra rossa is absent.

RECENT SOIL EROSION.

Reference has been maae on a previous page to small valleys in the 

area underlain by the Boise granite, which are so deeply filled with 

debris that they have no surface streams, all of the water that comes 

to them being absorbed by the tlnconsolidated material forming their 

floors. The valleys of this description were, up to within about 15 or 

20 years, much more numerous than at present. A recent change has 

occurred which has caused fresh stream channels to appear in previously streamless depressions, gulches, etc., and even on hillsides 

formerly completely soil-covered. The change referred to is well 

known to ranchers and others, and is said to have been begun about 

1880. At present there are numerous lateral depressions and gulches, 

branching from the larger vallej^s, which have fresh channels cut in 

their doors and in the sides of the adjacent hills, that are from 10 to 

15 or more feet deep and a mile or more long, with perhaps several 

branches, but which previous to the date .just given are known to 

have had smooth, unbroken contours. In several instances welltraveled roads have been crossed by these gullies, necessitating a wide 

detour to get about a steep-sided gulch from 10 to 15 feet deep. It 

does not require historical evidence, however, to show that the gullies 

referred to are recent. They are fresh cuts, with nearly vertical walls 

of loose earth, and at their heads begin abruptly. Each rain that 

comes is assisting in their extension and enlargement. At certain 

localities, which are unfortunately numerous, cultivated fields have 

been cut across by gulches formed during the last few years, which 

are still being enlarged. A photograph of one of these is presented 

on PI. XXV, A. One conspicuous result of the more complete drainage of valley bottoms by modern rill channels is the dying out of 

Bull. 199 02 10
146 SNAKE EIVER PLAINS OF IDAHO. [BULL. 199.

formerly luxuriant meadows of wild grasses and their replacement by 

sage brush. The rapid erosion in progress is destroying much of the 

finest land in the mountain valleys lying north of the Snake River 

Plains, and its prevention is an exceedingly important problem, which 

demands immediate attention.

The beginning of this recent erosion is correlated with the introduction of sheep in large numbers into the country, and is but another 

phase of the widespread destruction for which sheep raising on a 

large scale is responsible. The cause of the washing is mainly, the 

destruction of the once abundant bunch grass by the close grazing of 

sheep.

It might, perhaps, be thought that if sheep raising could be discontinued or properly controlled the destructive washing of the land incident to it under certain combinations of soil and climatic conditions 

would be arrested, but the process of erosion once started is difficult 

to stop, and will continue even if the sheep were removed. Successful attempts to check the work of rills Avhere they are rapidly deepening their channels have been made b}^ a method that is simple and 

efficient. Near the barrack at Boise small dams placed in the streams, 

with suitable precautions against erosion on account of the plunge of 

the water, have led to the deposition of gravel and sand and caused it 

to form broad fields, which will no doubt in time be cultivated. 

Under this method, however, erosion still progresses above where the 

water is ponded and the destruction continues, and will necessitate the 

building of additional dams lower down the stream courses or an 

increase in the height of those already constructed. Probably the 

best method of checking the work of the rills and brooks is to plant 

trees in them, and especially the planting of cottonwood, willows, etc.,

in belts across the channels where widest. By systematic attempts of

this character much of the damage that threatens can be cheaply and 

efficiently checked.

One result of the cutting ot channels through previously completed 

flood plains which are under cultivation, as in the example shown on 

PI. XXV, is the more complete subdrainage of the .portions of the 

fields remaining, thus necessitating additional irrigation. In many 

such instances the construction of willow dams sufficient to check the 

flow of the water and cause deposition would also lead to lateral percolation from the streams, which would be equivalent to subirrigation. 

The destruction by recent rill erosion is not confined to the upland 

valleys, but, by reason of the immense amounts of gravel and sand 

swept down to the larger streams, causes them to spread out sheets of 

this material on their flood plains, which bury the vegetable mold and 

greatly impair and even destroy the agricultural value of the land.
U. S. GEOLOGICAL SURVEY BULLETIN NO. 199 PL. XXV

A. RECENT STREAM EROSION NEAR HOWELL, IDAHO.

/,'. WATER-WORN BASALT IN SNAKE RIVER CANYON NEAR HAGERMAN, 

IDAHO.
PART IT WATER RESOURCES,

INTRODUCTION.

SURFACE AND SUBSURFACE WATER.

The water supplied to land areas comes from the atmosphere and in 

part flows over the surface and in part sinks below the surface. What 

relation the surface " run-off" shall bear to the underflow depends on 

a variety of climatic, topographic, and geologic conditions.

Of climatic conditions one of the most important is the rate at which 

water is supplied. If, for example, the same amount of water is precipitated in an hour, as during1 a torrential rain, that at another time 

falls in several hours during a gentle rain, the ratio of the run-off to 

the amount of water sinking into the earth is far greater in the first 

than in the second instance. The length of the periods between rains, 

rate of evaporation, etc., are also important factors in the process of 

dividing the water that reaches land areas into surface and subsurface 

portions, but need not be discussed at this time.

Among topographic and geologic conditions of interest in this connection the principal ones are surface slope and the porosity or fissured condition of the surface rocks, including the sheet of rock waste 

which generally forms the surficial layer of the land. The degree of 

slope varies from vertical to horizontal. On cliffs and steep slopes 

generally the run-off is large in proportion to the amount of water 

that is absorbed, while on plains there may be no means of surface 

escape and all of the water precipitated may sink into the rocks or be 

evaporated. The degree of porosity varies from that of compact rocks, 

which are practically nonabsorbent, to that of loose soils, sands, etc., 

which drink in all the water that falls upon them. The more compact 

rocks are frequently fissured or jointed and thus afford an easy downward passage for all of the water reaching their surfaces.

In southern Idaho the annual precipitation is small and occurs at intervals, and although in part descending as torrential rains, a much 

larger portion is furnished by gentle rains and by the melting of 

snow. The climatic conditions thus favor the absorption of the water 

by the rocks rather than surface run-off. The same result is favorfd 

also by the presence generally of a thick sheet of porous rock waste, 

especially in the mountains and foothills, and by the porous or fissured 

condition of the rocks forming the surfaces of the plains. On the 

Snake River Plains there is practically no run-off, all the water

147
148 SNAKE RIVER PLAINS OF IDAHO. [BULL. 199.

reaching them from the atmosphere not evaporated or absorbed by 

plants disappears below the surface.

The run-off is contributed directly to surface streams, but these 

would be intermittent, flowing only during and immediately followingrains or the melting of snow and ceasing to flow during interveningperiods, were it not for the return to the surface of previously subsurface waters. This return is accomplished in part by seepage from 

the sides and bottoms of valleys, and in part by springs. The manner 

in which water is retained for a greater or less time by porous and 

fissured rocks and rock waste and returned more or less gradually to 

the surface thus becomes important in the study of both the surface 

and subterranean water supplies. It is to the subsurface or subterranean waters that attention is here invited.

The water absorbed by porous material, such as constitutes soils, 

sand dunes, etc., is in part returned to the surface by passing upward, owing to what is termed capillary attraction, as the surface 

dries, and in part through the action of plants in absorbing water 

through their roots and transpiring it through their leaves. The 

latter process is an important adjunct to direct evaporation, and in 

densely plant-covered regions the quantity of water so passing into 

the air is frequently greater than that escaping by direct evaporation, 

even from freely exposed water surfaces. The water not removed 

by evaporation or by plants is in part retained as soil moisture, and 

if there is an excess above what the soil can permanently hold as a film 

on the .surface of the particles composing it, such excess descends or 

moves laterally, under the influence of gravity, to a lower position and 

is available for the supply of springs. Water entering fissures in 

rocks evidently has, in general, greater freedom to flow than that in 

porous material, and in many instances is also an important source for 

the supply of springs.

The force which causes subterranean water to flow is the same that 

controls the movements of surface streams, namely, gravity, but certain modifications due to difference in temperature, capillarity, etc., 

fully discussed by King/' will not be considered at this time.

SPRINGS.

Four varieties of springs may for convenience be recognized, 

namely, hillside, canyon, fissure, and cavern springs, the classification 

being by reference to types and with the understanding that more or 

less intermediate gradations occur between well-characterized examples. In the case of each variety there is a wide range in volume, the 

minimum in each case being what is termed seepage.

a A. highly instructive discussion of the way in which water percolates through porous material 

may be found in a paper on the " Principles and conditions of the movements of ground water," by 

F. H. King, in'the Nineteenth Ann. Kept. U. S. Geol. Survey, Pt. IV, 1899, pp. 59-294,
KUSSELL.] SPEINGS. 1 49

HILLSIDE SPRINGS.

Examples of this type occur where thick beds of porous material, 

such as sand, loose-textured soil, disintegrated rock, etc., occur on 

the border of valleys or form uplands on which precipitation takes 

place and the water percolating downward through the interspaces in 

the receiving laj^er meets a less pervious layer and flows laterally along 

its surface, becoming more or less concentrated, and emerges at or 

near the base of an escarpment as a stream. The presence of a retentive layer in the uplands bordering a depression, at a horizon above its 

bottom, however, is not essential. As is well known, when precipitation is sufficiently abundant the subsoil is saturated below a certain 

horizon. During heavy or long-continued rains the soil and subsoil 

may be saturated from the surface downward, although under certain 

conditions there is a lower limit to saturation above the base of the 

porous layer. After the supply of water at the surface ceases the 

upper limit of saturation or the "water table," as it is termed, subsides. The water table is not a plane, but an undulating surface, 

which rises beneath hills and is depressed beneath valleys. As water 

escapes by seepage, or when more concentrated, as springs, the water 

table is lowered and at the same time flattens, tending to become a 

plane surface where it subsides below all surface depressions. So long 

as the water table is above the bottom of a surface depression, such as 

a valley, hillside springs are possible.

These conditions are indicated in fig. 2, which is an ideal vertical 

section across a valley with a stream flowing down it, excavated in 

porous material.

FIG. 2. Section showing relation of hillside springs to water table.

The water falling on the surface aa penetrates downward, and at a 

certain stage after the supply ceases the upper surface of the saturated 

subsoil may be assumed to have the position l)b. At such a stage the 

water flows toward the valley along the courses indicated by the dotted 

lines and escapes most commonly by seepage, but if concentrated in more 

definite channels forms springs. Should the water table be depressed 

to the line cc, the springs would cease to flow and lateral seepage from 

the stream occupying the valley would occur. Under these conditions 

the surface of saturation is higher beneath the valley than beneath the 

adjacent uplands. So long as a stream continues to flow, unless its bed 

is impervious, the water table can not be depressed below its bottom.
150 SNAKE KIVER PLAINS OF IDAHO. [BULL. 199.

When the stream bed is dry, however, as so frequently happens in arid 

regions, the water table may subside below the bottom of its bed, or 

to del, and become a plane surface; or, as really 

happens for various reasons, ma.y disappear, there 

being no saturated subsoil layer.

Owing to variations in the conditions on which 

the lives of hillside springs depend, thej^ commonly 

exhibit seasonal variations in volume, and perhaps 

also in temperature..

CANYON SPRINGS.

When water disappears beneath the surface of the 

land, it may enter pervious stratified rocks and flow 

through them for long distances, finally emerging 

where the water-carrying beds have been cut across 

by erosion or in other ways furnished with openings 

through which water may escape from them. One 

of the most common methods by which this result 

is attained and one abundantly illustrated in southern Idaho is by the excavation of canyons in nearly 

horizontal stratified rocks, some of the larger of 

which are water charged. Although at times having essentially the same characteristics as hillside 

springs, the type here referred to, in numerous conspicuous examples, depends on markedly different 

conditions. The water is conducted to a distance 

through pervious beds having impervious floors, 

and may or may not be covered by impervious laj7 -

ers. Owing to freedom of escape even when an

impervious cover is present, the water is not usually 

under pressure except such as results from retardation due to friction of flow. There is no storage 

reservoir as in the case of fissure springs, described 

below, and if the source of supply fails the springs 

run dry.

While the underground courses of the waters supplying hillside springs are commonly short, being 

measured usually by rods, the journeys of the waters 

feeding canyon springs may be long, and in many 

instances are measurable in miles or tens of miles.

The conditions favoring the occurrence of canyon 

springs are illustrated by the section forming fig. 3, 

which, although ideal, indicates in a general way

the mode of origin of the copious springs in Snake River Canyon,

which are the type of the class under consideration.

FIG. 3. Section showing 

conditions favoring 

the occurrence of canyon springs.
RUSSELL.] SPEINGS. 15.1

At the left of the diagram an attempt has been made to indicate the 

presence of a mountain valley deeply filled with alluvium, beyond 

which rises a deeply sculptured, bordering- mountain spur. The gravel 

in the valley extends beneath the plain, perhaps merging with lake 

beds, and forms a porous layer which is underlain by an impervious bed and covered by a lava sheet. This is a special case, to be 

sure, but the beds beneath the plain may be of any nature, the essential feature being that one of them is so situated as to become water 

charged and to slope toward a canyon which is cut below its base. The 

bed above the pervious layer in the' case of the Snake River Plain is 

composed of fissured lava, and permits all the water falling on it to have 

ready access to the porous bed beneath. In fact the fissured basalt at 

times furnishes the pervious bed, being underlain by a water-tight 

stratum. Water coming to the exposed portion of the pervious bed

in the mountains descends into it, as does also the water supplied to

the surface of the plain, as is indicated by arrows. Where the pervious bed appears in the side of a canyon, springs emerge.

The lost rivers of southern Idaho contribute to the support of the 

springs in Snake River Canyon, but this source of supply is augmented 

by the precipitation on the adjacent plain. The flow is constant, owing 

to the retention of the waters in porous beds, being in part supplied 

by hillside springs in the mountains, but the flow is regulated more 

largely by the extent of the water-charged beds. In general, canyon 

springs are perennial and exhibit no seasonal changes in volume or 

temperature.

FISSURE SPRINGS.

If a pervious layer of the nature of those supplying cai^on springs 

is not cut by erosion, or in some other way furnished with means of 

escape for its contained waters, it is evident that it may become water 

filled. The water at any point in the porous bed will then be subject 

to the pressure of water at higher levels, and be forced in any direction in which an opening may occur. In nature such means of escape 

are sometimes provided by fissures. If a fissure leads from such a 

reservoir to the surface and the pressure on the water is sufficient, a 

fissure spring results. The conditions which lead to the occurrence of 

fissure springs are seldom, if ever, exposed so as to be studied in detail, 

and are presumably varied. In many instances it is probable that a 

porous stratum is absent, and the water finds its way through intersecting fissures. However diverse the conditions, it is evident that the 

water which rises and overflows is under pressure, and that a reservoir 

is present, By this it is not meant that anything like a cavern necessarily or commonly occurs. Usually porous rocks play the r61e of a 

reservoir. Fissure springs, like all other springs, are dependent on 

precipitation for their water supply, but owing usually to the small
152 SNAKE RIVER PLAINS OF IDAHO.

size of the conduits leading to the surface, in comparison to the volume 

of the reservoir, they are perennial and do not fluctuate in volume or 

temperature with seasonal changes. Like canyon springs, those of 

the type here considered are supplied from a distance and may exist in 

arid regions. They are frequently of common occurrence where broad 

sheets of stratified rock have been broken, and especially where faults 

occur. Owing to the depth from which their water frequently rises 

its temperature is often high. Springs of this type are common in the 

Great Basin, and occur also throughout the similarly disturbed region 

about it. In southern Idaho numerous examples are present, as is 

shown by the several warm and hot springs known.

CAVERN SPRINGS.

In limestone regions especially, water percolating through the 

rocks, on finding its way initially through fissures and joints, dissolves 

the rocks and opens out galleries. These galleries, such as Mammoth 

Cave in Kentucky, for example, may have lakes in them, or the water 

may flow freely; in either case a spring is formed where the water 

emerges in a neighboring valley. If a subterranean lake is present it 

may supply a conduit with water under pressure, and give origin to a 

fissure spring. With or without a lake present, springs in the sides of 

valleys may be found which simulate canyon springs. Caverns originating in any manner may exert an influence on subterranean drainage in the ways just suggested.

Cave springs are not known in southern Idaho, and further discussion of the conditions on which they depend need not be indulged in 

at this time.

Similar to cave springs are the streams which sometimes gush out

of glaciers, but these have no connection with the subject in hand.

TEMPERATURE.

In all springs the temperature of the water is regulated by the temperature of the rocks from which it is derived.

In this connection certain well-known facts ma}7 be restated. The 

seasonal variations in temperature in temperate regions extend downward into the earthJx> a depth of about 50 feet, and at that depth there 

is a horizon of no seasonal variation which has a temperature corresponding with that of the mean annual temperature at the surface. 

Below this stratum of no seasonal variation the temperature increases 

with increase in depth, at the rate in general of about one degree 

Fahrenheit for each 60 feet.

Hillside springs, being of local origin and the waters supplying them 

not descending deeply, usually have about the mean annual temperature of the region where they occur. At Boise this is approximately 

50° F. In summer such springs are colder and in winter warmer than
RUSSELL.J TEMPERATUBE OF SPKINGS. . 153

the air. They may'in fact have a temperature even in summer but 

little, if any, above that of freezing water, as, for example, where 

a soil or the surface sheet of rock waste becomes deeply filled with 

ice during winter, which melts slowly during summer, and yields 

nearly ice cold water. Hillside springs supplied with water which 

descends to a depth oif less than about 50 feet may be expected to fluctuate somewhat in temperature from season to season, but are not 

quickly responsive to surface changes. Those which derive their 

water from a depth of approximately 40 to 60 feet and are of sufficient volume not to be sensibly altered in temperature on nearing the 

surface will show no seasonal variation. Canyon and cave springs 

perhaps, as a rule, are supplied with water which has descended more 

than 50 feet into the earth and possibly may have reached a depth of 

several hundred feet, and their temperatures should, therefore, be 

somewhat higher than the mean annual temperature of the region 

where they emerge, but they will not be characterized by a high degree 

of heat unless they come from abnormally warm or hot rocks. In the 

t}rpical canyon springs in southern Idaho the temperature is about 

6)° F., or 10° above the mean annual temperature, and shows no 

seasonal variation. In these and other similar instances, however, 

in which springs are supplied by subterranean drainage, particularly 

of broad sheets of pervious rocks, there may be some addition of hot 

water rising through fissures in the rocks beneath. That is, fissure 

springs may contribute to the supply of subterranean streams in the 

same w&y that they do to surface streams.

Fissure springs are supplied from depths ranging from a few 

score feet, or even less, to hundreds of feet, and come to the surface with all variations in temperature, from that of the mean annual 

temperature of the region where they occur up to the boiling point 

for the elevations where they emerge. Those of sufficient volume and 

manifest freedom of flow indicate closely the temperature of the rocks 

from which they are supplied, and the depth of their source can thus 

be approximately determined, if the rate of 'increase of temperature 

with depth for the locality is known. The rise of temperature with 

increase in depth below the stratum of no seasonal variation, however, 

is not the same in different regions, and may be greatly modified by 

local causes, such, for example, as the presence of still hot volcanic 

rocks below the surface. The hot springs in Clover Creek Valley, 

near Blanche, and again the hot springs at Soda Springs, Bannock 

County, Idaho, are situated near volcanic craters that were recently 

active, and no doubt derive their heat from hot volcanic rocks at no 

great distance below the surface. The temperature gradient beneath 

the Snake River Plains, as indicated by the meager data in hand, is 

above the normal. . As will be shown later (p. 173) the wells along the 

Oregon Short Line Railroad give an increase in temperature of 1° F.
154 SNAKE EIVEE PLAINS OF IDAHO. [BULL. 199.

for each 45 feet below the stratum of no seasonal variation. The canyon springs also, on the supposition that the rate of increase of heat 

with depth is normal, indicate a higher temperature than Avould be 

expected from the depth of the localities where they emerge below 

the level of the adjacent plains.

Chemical changes, as well as movements in rocks, may also produce 

abnormally high temperatures, which might be imparted to the waters 

of any of the types of springs enumerated above, but which are most 

apt to be felt by fissure springs.

The phenomenon of a hot and a cold spring near each other, which 

sometimes occurs, can be easily explained by reference to the diagrams given above. A hot fissure spring supplied from a deep source 

may evidently occur near a cold hillside spring, the association of the 

two being simply accidental.

There is much that is interesting in the chemistry of spring water, 

and in the way in which hot springs especialty deposit material most 

commonly calcium carbonate and silica on reaching the surface, but 

this phase of the study can not be considered at present.

SIMILARITY BETWEEN SPRINGS AND WELLS.

Each of the varieties of springs enumerated above is represented by 

wells.

The ordinary wells, especially in humid regions, are supplied by 

percolation from the adjacent portions of the porous beds they penetrate, and are similar to hillside springs. When they are supplied at 

a depth of about 50 feet below the surface their temperature, when 

inclosed, is approximately that of the mean annual temperature of the 

locality where they occur. The water in them rises and falls with 

variations in the position of the water.table, and if the surface of saturation sinks below their bottoms they become dry. Deep wells, 

usually obtained by drilling, which penetrate pervious strata in which 

the water stands at a definite horizon and which in many instances, as 

is frequentty stated, can not be lowered by pumping, are homologous 

to canyon and cave springs. The water is either not under pressure or 

not under sufficient pressure to cause it to rise to the surface, and has 

a constant temperature which is somewhat higher than the mean 

annual temperature of the locality. Artesian wells are essentially 

artificial fissure springs, and have a constant and frequently a high 

temperature.

RELATION OF SPRINGS TO CLIMATE, TOPOGRAPHY, AND GEOLOGY.

In addition to the fact that all springs are dependent on precipitation for their water supply, there is a relation between the amount of 

water supplied and the topographic and geological conditions which 

determines what variety of spring will result.
RUSSELL.] EELATION OF SPRINGS TO CLIMATE, ETC. 155

In humid regions the subsoil is normally saturated below a certain 

depth (the water table) and hillside springs are of common occurrence. 

In such regions, also, water is nearly everywhere obtainable by means 

of wells of small depth. In arid regions the subsoil is, as a rule, not 

saturated, owing not only to downward percolation, but also to the drying of the surface and the passage upward of absorbed water, through 

capillary action; and surf ace wells are not successful and hillside springs 

are practically absent. In both humid and arid regions either canyon 

or cave springs are possible, the control passing to topographic conditions; that is, the depth to which the rocks are cut by canyons and 

valleys determines whether the water contained in previous strata or 

caverns shall outflow or not. In humid regions the general lowering 

of the surface b^v denudation keeps pace more or less closely with the 

downcutting of stream channels, and deep canyons do not result, 

except under certain highly special conditions. The valleys, as a rule,

have flaring sides, and are encumbered with debris which tends to 

mask the presence of springs. Although springs of the type of canyon springs do occur in wet regions, they arc not common or characteristic. In arid regions, however, high above sea level, which are 

crossed by rivers rising in Avell-watered uplands, deep canyons with 

vertical or nearly vertical walls may be produced, and it is in such 

instances that canyon springs reach their most typical development. 

In a large section of the arid region, namely, the Great Basin, canyon 

springs are absent for the reason that the streams are not permitted 

to excavate deep channels. In the Great Basin the valleys are being 

filled or upgraded, and 116 removal of material from the basin occurs, 

except in a small way through the agency of wind, and this is probably 

compensated for by the dust brought in in a similar manner.

Fissure springs are possible when- water exists in pervious rocks 

under sufficient pressure to force it to the surface if an opening is provided. Such openings are produced by movements in the earth's crust, 

and regions not affected by breaks or faults, although water-charged 

beds maj7 exist beneath them, are without fissure springs. Fortunately the rocks beneath large portions of the arid region have been 

broken, and the characteristic springs, particularly in the Great Basin, 

are due to this cause.

The favorable result of a combination of climatic, topographic, and 

geologic conditions is illustrated by the fact that canyon and fissure 

springs are not dependent on the precipitation in the immediate vicinity 

of the localities where they occur, but their waters are conducted 

underground perhaps for hundreds of miles without loss by evaporation, and may rise in a desert local \ty and give origin to an oasis. But 

for the fortunate combination of conditions referred to, much of southern Idaho, in common with nearly all of the arid region west of the 

Kocky Mountains, would be far less suitable for habitation than it
156 SNAKE EIVEE PLAINS OF IDAHO. [BULL. 199.

is at present, and much of it would be practically impassable to 

travelers.

DEVELOPMENT OF SPRINGS.

The conditions on which the several varieties of springs described 

above depend at once suggests methods by which their flow ma}7 be 

increased, or new springs produced. This matter will be considered 

later in more detail, but I may call attention briefly to the self-evident 

fact that to increase the flow of a hillside or canyon spring the proper 

method would be to imitate nature and excavate tunnels or horizontal 

wells. As fissure springs rise through more or less vertical openings, 

it is obvious that in order to obtain water from subterranean sources 

where it exists under pressure vertical wells must be put down. Such 

artificial fissure springs are termed artesian wells.

ARTESIAN WELLS.

REQUISITE CONDITIONS.

The governing and qualifying conditions pertaining to artesian wells 

have been described b}' many writers, and are noted in a previous 

report relating to Idaho/' and need not be repeated here except in a 

very general way, to serve as an introduction to what follows.

The presence of water in a pervious stratum is usually dependent 

on the exposure of a portion of the bed at the surface, so that it ma}r 

receive the direct precipitation from the atmosphere or be charged by 

percolation from surface rock waste, seepage from streams, etc. A 

pervious bed may also become water charged by leakage from other 

beds, as has been explained by Chamberlin. 6 The geological conditions which lead to the filling of pervious beds so inclosed that the 

water can not escape from them, at least not freely, are various. The 

conditions most frequently occurring are illustrated by whaii are known 

as artesian basins and artesian slopes.

. In an artesian basin the strata containing one or more pervious beds 

we will assume, for simplicit}r, that but one is present, with a watertight bed above and below have the form of a basin, at some portion 

of the rim of which the pervious bed comes to the surface and receives 

sufficient water to saturate it. An illustration of this structure may 

be had by spreading a layer of sand over the interior of a saucer and 

placing another saucer within it, both vessels being in an upright 

position. If water is poured into the lower saucer until the spaces 

between the sand grains are filled and a hole is drilled in the bottom

«I. C. Russell, Water-Supply and Irrigation Papers U. S. Qeol. Survey No. 54,1891. Bibliography 

on p. 130-131.

6T. C. Chamberlin, The requisite and qualifying conditions of artesian wells: Fifth Ann. Kept. U. S. 

Geol. Survey, 1885, pp. 125-173.
RUSSELh.J ARTESIAN WELLS. 157

of the upper dish, the water will rise through it. In such an experiment the saucers represent the impervious and the layer of sand 

between them the pervious beds in an artesian basin. These conditions are indicated in the following ideal cross section of an artesian 

basin, in which the pervious bed A is water charged from the rain falling on its exposed rim and percolates downward until the bed is saturated to the impervious rocks B. A hole drilled at any point, as D 

or E, within the basin will permit the water to rise, owing to the presence of water at higher levels, and to overflow at the surface, providing the elevation where the hole is made is below the level of the 

lowest point in the rim of the basin by means of which the water is 

enabled to overflow. The upper limit of saturation in the pervious 

bed is termed the artesian head. In the diagram this horizon is indicated by the line OF, and water will rise and overflow within the basin 

at an)7" locality where the surface is below this level.

B A

FIG. 4. Section of an artesian basin.

Artesian basins are "usually produced by a gentle downward bending 

of rocks containing alternating beds of pervious material, such as sand 

or sandstone, and impervious beds, such as clay and shale. There are 

many qualifying conditions, however, as has been shown by Chamberlin in the article referred to above.

The essential condition which causes water to rise and overflow in 

the case of an artesian well is that it shall be under sufficient pressure. 

In order to insure this condition, however, a complete basin need not 

be present. This is indicated in fig. 5, showing wedge-shaped pervious beds so exposed at the top as to become water charged and inclosed 

below in impervious material. Such an occurrence might be termed 

an " artesian wedge."

PIG. 5. Section of an artesian wedge.

In each of the two illustrations just given the pervious beds are 

saturated and the water contained in them is essentially at rest; that is, 

hydrostatic pressure is what causes a portion of the water to .rise. In 

order that a well may continue to flow with undiminished pressure, it 

is evident that the supply must be renewed.

Hydrostatic pressure in a saturated stratum, or reservoirs, is not the 

only cause, however, by which wells may flow. Another method of 

flow is illustrated by what is known as an artesian slope.
158 SNAKE KIVEE PLAINS OF IDAHO. [BOLL. 199.

Water flowing through an inclined pervious bed meets with resistance due to friction of flow. If the pervious bed is included between 

tAVO impervious beds, as, for example, in the ideal section shown in fig. 

6, and a hole is drilled from the surface down to the water-charged 

layer, as at x, the friction of flow between x and g, 

where the water naturally escapes, may be sufficient 

to retard the current and cause the water to rise in 

the hole and possibly overflow. The reason is simply 

that the resistance met by water rising in the hole 

drilled at x is sufficiently less than the resistance 

between x and g to permit it to rise to the surface. 

The moving force in this instance, as in an artesian 

basin, is hydrostatic pressure. This matter has been 

discussed in the report on Nez Perce County, referred to above, where reference to other papers on the 

same subject may be found.

In the case of an artesian basin the pervious layer 

is essentially a filled reservoir, and the water is at rest 

until an opening is made in drilling a well; in the artesian slope the water is flowing. These statements, to 

be sure, need to be qualified to be strictly accurate, 

but they express the leading difference referred to. 

The success of wells drilled so as to tap an artesian 

slope depends not only on the quantit}' and permanence of the water supply, but on the degree of resistance the water meets with in passing through the 

permeable stratum. The greater the resistance within 

certain limits, the higher the water will rise in wells

leading to the surface.

It is not to be understood that all of the various 

ways in which subterranean water may be brought 

under pressure so as to be available for artesian wells 

have been enumerated. On the contrary, the only 

attempt here made, is to cite certain well-known 

principles for use later.

AVAILABLE WATER ON 

PLAINS.

SNAKE RIVER

The most serious economic problem which confronts the people of southern Idaho is how to obtain 

water for irrigation and for town and household purposes. The soil is almost universally of good quality, level land that could be easily tilled is abundant, 

the sunshine is brilliant, the temperature favorable, but the critical

FIG. 6. Section of an 

artesian slope.
RUSSELL.] SURFACE STREAMS. 159

condition, and the one that controls not only agriculture, but settlement for any object, is the prevalent scarcity of water. Under these 

conditions, water is more valuable than land. In fact, land, however 

well situated and however rich, is valueless for farming purposes 

unless water can be brought to it.

The water available for irrigation may be conveniently classified 

under, three heads, namely, surface streams, springs, and wells. 

Direct precipitation, averaging as it does less than 3 inches during the 

growing season, is too small to permit successful agriculture without 

irrigation, except, possibly, in certain localities where the soil is of 

such nature as to absorb and retain the winter supply.

SURFACE STREAMS:

The greatest source of water supply for the Snake River Plains, and 

the one first to be utilized, is to be found in the streams which, rising 

in the neighboring mountains, flow to or across them. The quantity of 

water reaching the plains in this manner and the various ways it can be 

most economically diverted and used for irrigation have been investigated by the State engineer of Idaho, and the conditions existing are 

described and discussed in a series of reports. One of these, the biennial 

report for the years 1899 and 1900, by D. W. Ross, a is remarkable for its 

breadth of view and thoroughness, and will prove invaluable not only 

to individuals and companies directly interested in irrigation, but 

should serve as a guide to the legislature of Idaho in framing wise 

laws to govern the uses to be made of the scant water supply.

The central plain of southern Idaho has an extent of about 20,000 

square miles. The surface streams available for irrigating this great 

tract are Snake River and its tributaries, together with the "lost 

rivers " which fail to reach the main drainage channel. While considerable portions of the plains are rocky and entirely unsuited for agriculture, and other portions, also large, are too high above the streams 

to be irrigated, there remains more good land which can be reached 

by canals than can be brought under cultivation by the use of the 

water carried by all the streams during the growing season.

"All of the smaller streams that reach the Snake River Plains from 

either the north or south have been fulty utilized, except the Bruneau 

River, which in summer still discharges about 400 cubic feet per second 

into Snake River. The waters of Snake River above American Falls 

are largely utilized, about 211,000 acres being irrigated, of which 

about 200,000 acres are in the valley proper. The great waste of 

water that accompanies the irrigation of this land is forcibly stated b}^ 

Ross. In spite of the large demands made on Snake River in the

"Biennial Report of the State Engineer to the Governor of Id ah of or the year 1899-1900; [Boise] 1901, 

pp. 1-101, 6 plates nncl 3 maps.
160 SNAKE RIVER PLAINS OF IDAHO. [BULL. 199.

portion of its course -referred to, a minimum of over 5,000 cubic 

feet per second continues on below Montgomery Falls. From American Falls westward to the Idaho-Oregon boundary Snake River is in a 

canyon, and practically no use is made of its waters for irrigation. 

On Boise River, from the point where it emerges from the canyon portion of its course, just above Boise, to its mouth, many canals have been 

constructed for the diversion of its water, and 61,000 acres of land are 

irrigated, but much good land remains for which there is at present no 

 water available. This is the largest tract of land under irrigation in 

Idaho. Payette River is utilized in a similar way and made to water 

28,000 acres of land.

The utilization of the easily available water supply of the surface 

streams has thus far been made principally by individuals and small 

companies. The development of this branch of the water resources 

in a more comprehensive and economical way, based on a thorough 

understanding of the conditions, has recently attracted attention, but 

is not yet fully initiated. This broader view of the problem has been 

grasped by the State engineer, and comprehensive plans for its elaboration have been outlined. The larger tract of land, which, so far as engineering questions are concerned, can be watered by diverting Snake, 

Boise, and Payette rivers, as shown on the maps accompanying the 

report of the State engineer just referred to, is about 1,800,000 acres. 

Such measurements of these rivers as are available, however, indicate 

that not over half of this area, or, in round numbers, 1,000,000 acres, 

can be supplied with the requisite amount of wate' 1 during years of 

average precipitation. Great fluctuations in the amount of water flowing through the river channels during the growing season, however, 

occur from year to year, and the amount of land that can be continuously cultivated without loss during years of minimum precipitation is

probably much less than the area just stated. Including also the 

smaller streams, an estimate shows that when all available water in 

surface streams is economically used about one-twelfth, or, we will 

assume, 8 per cent of Snake River Plains can be cultivated. It must 

be remembered that this is a rough estimate, based on insufficient data, 

but I believe it is too liberal. A safer estimate, considering all the 

difficulties and uncertainties attending large irrigation schemes, is probably that one-twentieth, or 5 per cent of the portion of the Snake 

River Plains where favorable soil conditions occur, may ultimately be 

irrigated from surface streams.

The lessons of public interest which the study of the surface streams 

clearly indicates may be briefly stated as follows:

First. Water being highly valuable and an inheritance of the people in common, the strictest economy in its use should be obligatory. 

No more water should be used than is essential to proper cultivation; 

but in this connection a natural adjustment will no doubt in part be
KTJSSELL.] SURFACE STEEAMS. 161

reached, since water above a certain definite quantity skillfully applied 

is injurious to crops, and brings about cumulative difficulties in the 

way of concentrating alkaline salts in the soils.

Second. The canals and ditches, and in fact the entire practice of 

irrigation, should be under the control of a skilled and efficient engineer, in order that water may be applied to the best land in proper 

quantity, all of the available supply utilized, and loss by evaporation 

and seepage reduced to a minimum.'

These conclusions, although sufficiently obvious in the abstract, 

become painfully apparent to one traveling through even the most 

productive portion of southern Idaho. It is safe to say that less than 

one-half of the service is obtained that the waters now flowing through 

canals and ditches might render under skillf ul management. Waste is 

everywhere conspicuous. The ignorance, carelessness, and greed of 

the people are disheartening to one who endeavors to point out additional sources of water supply. Obviously the first and paramount 

duty of the people, not only in Idaho, but generally throughout the 

arid regions, is to employ economically the water now available in 

surface streams.

An increase in the supply of water flowing through'surface streams 

during the growing season, as has been pointed out by Ross and others, 

may be had by storing the water which runs to Avaste between the 

seasons when it is needed for irrigation. It is in this direction that 

the greatest addition to the amount obtainable by diverting streams is 

to be expected. For this purpose suitable reservoir sites must be 

available, situated where they can be filled during the Avinter season, 

and Avhere desirable land exists at lower levels over which the Avater 

can be spread. This again is an engineering problem of high order, 

and one beset with difficulties and dangers. Some attempts have 

already been made in the direction of storing the winter flow of the 

streams, but not always wisely or Avell, and much more is to be expected. 

The cost of such enterprises is usually great, and it is evident that 

many favorable plans will have to Avait until increase in population 

and greater demand for farm products justify the large initial expense.

When all of the water furnished by streams during the growing 

season has been judiciously applied in irrigation, and all of the flood 

water that it is practicable to store in reservoirs is made available, 

there will still remain extensive tracts of excellent agricultural land 

unprovided for. Besides the need of water for irrigation, there is a 

great and constantly increasing demand for Avater for toAvn and household purposes. With the hope of supplementing the surface supply 

attention has been directed to subsurface waters. The chief purpose 

of the reconnaissance here reported on Avas to ascertain, so far as the time 

available Avould permit, what can be expected from this source. The 

Bull. 199 02 11
162 SNAKE EIVEE PLAINS OF IDAHO. [BULL. 199.

water supply beneath the surface may for convenience be considered 

under two separate headings;, namely, springs and wells.

SPRINGS.

The water reaching the surface from subterranean sources through 

natural conduits within the area embraced in the Snake River Plains 

forms canj^on springs and'fissure springs. Hillside springs are practically absent, and cave springs are unknown.

CANYON SPRINGS.

Springs of this type occur on Snake River principally between Shoshoiie Falls and the mouth of Bruneau River, where the stream has cut 

deeply into the lava sheets and associated sedimentary beds across 

which it flows. They are confined to the northern side of the river 

for the reason that the geological conditions on which their existence 

depends are not present on its southern side. Although much use is 

now being made of these springs for irrigation, far more water is supplied than is utilized, and the vast source of power they furnish is 

entirely unemployed. More than this, by excavating horizontal wells 

or tunnels the water may in numerous instances be made to flow at 

localities where it will be of greater service than at present.

An attempt to indicate the value of the numerous springs that gush 

from the north side of Snake River Canyon in their order from Shoshone Falls westward is here presented, but their full importance can 

only be determined by a detailed survey.

At Blue Lakes the water issuing from large springs situated principally at the head of a side alcove opening from the main canyon is, 

as already explained, 'utilized for the irrigation of extensive orchards, 

which are highly productive.

Below Blue Lakes to the point where the surprisingly great outflow of 

water occurs at The Thousand Springs, a distance of about 18 miles, there 

are a few small ranches, which are watered from springs. Although 

this portion of the canyon was seen by me only from above, I judge 

there are a number of localities where the water supply could be 

greatly increased or made to issue at a higher level, and thus be of 

greater service than at present. This means that not only the flat 

land due to deposits from the river can be irrigated, but also much of 

the rough talus slopes. The planting of trees and vines, not in straight 

rows, but here and there among the fallen blocks of rock, must be 

practiced in order that the great possibilities of the canyon may 

be fully developed.

The most remarkable springs of Snake River Can}^on begin about 

2 miles above where the Salmon River comes in, and extend westward to Bliss, a distance of about 18 miles. Throughout this por-
RUSSELL.] ' CANTON SPEINGS. 163

tion of the canyon springs occur in large numbers, and many of them 

are of great size. The astonishing volume of the springs which have 

led to the existence of Box, Little, and Malade canyons has already 

been referred to. From a locality about 1 mile up the canyon of 

Snake River, about the mouth of Box Canyon, numerous springs gush 

out at various elevations up to about 220 feet. It is probable that all 

of the water issues from a single pervious stratum beneath the rim 

rock which sharply defines the brink of the canyon, and in descending 

through the abundant talus appears and disappears perhaps several 

times. The position of'the highest line of springs is plainly marked 

by the upper limit of vegetation. Half a mile below the mouth of 

Little Canj^on, near the level of the river at its lowest stage, an 

immense spring of wonderfully clear water of a delicate bluish 

color rises through a bed of clear white sand, and for this reason is 

named Sand Spring. This great spring is situated in a slight reentrant 

of the canyon wall, which indicates the nature of the beginning of a 

spring-formed alcove.

Opposite the mouth of Salmon River, springs which come to the 

surface from beneath a lava sheet which has been weathered back from 

the canyon wall about half a mile have been diverted and are now 

used to irrigate several small ranches. A picturesque fall which these 

waters make in descending into the canyon is known as the Snow Bank. 

This is the east end of the truly marvelous Thousand Springs, where 

in the space of about half a mile countless streams of water gush out 

from the canyon wall, in part at an elevation of 185 feet, but decreasing when traced westward to about 75 feet. The aggregate discharge 

of "these springs is estimated to be 20,000 cubic feet per second. The 

springs show no seasonal variation. Their temperature is 62° F. 

The water comes from the cellular basal portion of a lava sheet which, 

as previousl}7. explained, was in part shattered and in part u shredded" 

by steam explosions, and descends over a cliff composed principally of 

compact volcanic lapilli. The immense water power that could be 

easily utilized here awaits development. Only a small fraction of the 

water pouring out and descending in picturesque, foaming cascades is 

now utilized for irrigation.

A novel plan for raising a portion of the water to the plain above, 

where there is a great tract of fine land available for irrigation, has 

been attempted hy the Idaho Hydraulic and Pneumatic Irrigation 

Company, of which Mr. A. Ferguson, of Hagerman, Idaho, is chief 

engineer. The leading features of the plant, now nearing completion, 

is a large completely inclosed iron tank, or air separator, resembling 

a steam boiler, situated at the base of the cliff, into which, near its base, 

water is conducted from about 180 feet above by means of a large iron 

pipe or penstock. The water escapes from the tank in part through a 

standpipe connected with it near its bottom and rising to a height of
164 SNAKE EIVEE PLAINS OF IDAHO. . [BULL. 199.

about 40 feet, and in part through a smaller pipe leads from the tank, 

also near its base, to the summit of the canyon wall. The operation of 

the plant is this: The water in rushing down the penstock carries air 

with it, which separates in the tank and rises to the top, where it is 

under the pressure of the water in the large escape pipe, 40 feet high. 

The air pressure th-us obtained forces water up the smaller pipe leading to the top of the canyon wall. This pneumatic engine, if such it 

maybe termed, is claimed to be automatic in its operations, and therefore economical when once installed. It has not as yet been put in 

actual use so far as irrigation is concerned, although it has been made 

to discharge a stream of water on the plain above where it is situated, 

and its efficiency remains to be demonstrated.

Near the western end of The Thousand Springs water emerging at 

an elevation of about 75 feet on the canyon wall has been conducted 

across the river by Mr. I. A. Heron, in a pipe 12 inches in diameter, 

supported on a f-inch wire cable, which rests on crossed timbers 

planted in the river's bottom. The penstock leading to the pipe has 

a fall of 40 feet and delivers about 600 cubic feet of water per second 

on the south bank of the river. About 300 acres of land are under 

irrigation. An instructive experiment in connection with this plant 

was made in attempting to use a pipe placed on the bottom of the 

river. It was found, however, that air carried into the pipe by the 

water rushing down the penstock supplying it collected in the pipe at 

its upward bends on the river's bottom and caused it to rise and break.

Just below The Thousand Springs, Snake River makes an abrupt 

bend to the south, returning again to its A\7 estward course about 7 

miles farther downstream. On its southern side the river is cutting 

into a prominent bluff of nearly white sand clay and on its northern

side it is bordered by a large body of land, which, for the most part, has

a gentle slope. This " Hagerman bend" contains by estimate about 14 

square miles^ nearly all of which can be irrigated from springs. The 

northern wall of the canj^on continues westward from The Thousand 

Springs, and does not follow the bend of the river, for the reason that 

the stream, after having cut through two or more upper lava sheets 

and a thick la}^er of sand and clay below, discovered a southwarddipping sheet of lava which deflected the current toward its left bank. 

At the base of each of the two upper sheets of lava strong springs 

pour out and are extensively utilized for irrigation. They emerge, 

however, at too low a level to be available for use on some.xof the 

higher terraces, and to obviate this difficulty in part two tunnels have 

been excavated in the lava with remarkably successful results.

One of these tunnels, on Dan Jones's ranch, about 2 miles northeast of Hagerman, is 140 feet long, and discharges about 5 cubic feet 

of water per second. A second tunnel, about 100 yards eastward, is 

approximately 200 feet long and delivers about 4 cubic feet per second.
RUSSELL.] CANYON SPRINGS. - 165

Each of these tunnels is in the open-textured basal portion of a lava 

flow, and the water rises through fissures or other opening's in their 

bottoms. This fact shows that water exists under some pressure in 

rocks below the floors of the tunnels. The water has a temperature 

of 62° F. and issues at a horizon approximately 60 feet below the 

level of the surface of the plain to the northward.

Large springs occur at several localities from Hagerman to Bliss. 

In fact, there is what may be truthfulty termed a continuous chain of 

springs along the north side of Snake River Canyon from about 2 

miles above the mouth of Salmon River westward to Bliss. Included 

in this series are the springs of Little and Box canyons, Sand Springs, 

the Snow Bank, The Thousand Springs, the numerous springs and the 

two flowing tunnels near Hagerman, and a large number of strong 

springs between Hagerman and Bliss.

These springs issue from at least four, and perhaps more, strata.

Those in Little and Box can}7 ons and Sand Spring come from a stratum 

consisting largely of fine white sand which is overlain by a thick sheet 

of lava. The large springs supplying the Snow Bank come from above 

this same stratum of lava and from beneath a higher sheet, the margin 

of which has been weathered back from the canyon's border. The 

Thousand Springs issue from the lower portion of the lava sheet, over 

which the water supplying the Snow Bank cascades. This lava sheet, 

when traced westward to the end of The Thousand Springs escarpment, 

declines somewhat rapidly, the true dip being to the southwest, and 

passes beneath the agricultural land at Hagerman Bend. That the 

.stratum is water charged is shown by a large fissure spring at the base 

of a small fault which supplies in part a creek flowing eastward and 

emptying into Snake River about a mile above Salmon Falls. This 

fissure spring, as well as the passage of the water-charged layer which 

supplies The Thousand Springs, beneath Hagerman Bend, is strong 

evidence that artesian wells would be successful if put down near 

Hagerman, and probably at any locality in Hagerman Bend. The 

depth of the water-charged layer is not great, but increases from the 

northeastern portion of the bend toward the southwest. A test well 

put down at Hagerman to a depth of 500 or 600 feet would probably 

yield flowing water.

The lava sheet in the escarpment to the north and northeast of 

Hagerman is higher in the rock series than the one supplying The 

Thousand Springs. It is probably the same one from which the water 

flowing over the cliffs at the Snow Bank emerges, but in the intervening space, about 3 miles in a straight line, has been weathered far 

back from the canyon's brink, and was not followed in the field. 

While the springs downstream from Hagerman all the way to Bliss, 

including the great springs in Malade Canyon, may come from the 

same layer that furnishes the water at the two tunnels described above
166 SNAKE RIVER PLAINS OF IDAHO. [BTJLL.HB.

and the large springs in their vicinity, a detailed study would perhaps 

show that two or more water-charged layers are present. Before the 

relation of all the springs can be accurate^ determined and the best 

wajr to develop them pointed out it will be necessary to have an 

accurate topographic map of the region.

In the bottom of Snake River Canyon near Bliss the water-charged 

stratum which supplies the springs upstream passes below the level of 

the river, on account of a gentle westward dip, and springs are rare 

for a distance of about 40 miles. The reason for the general absence 

of springs in this section of the canyon is not only the greater depth 

of the layers which yielded water near Hagerman, the continuation of 

which to a considerable distance west of Bliss, however, is not 

positively known, but also the deep dissection of the portion of the 

plains lying north of Snake River. So far as- I am aware, springs 

are absent or nearly so in Snake River Ctinyon between the mouth 

of Kmghill Creek to a locality several miles below the mouth of 

Rattlesnake Creek. North of the river in this section creeks, about 

eight in number, have cut deep canyons, which would prevent a 

water-bearing stratum above the level of the main stream from conducting its waters to the Snake River Canyon. It is to be expected, 

judging from the topographic and geologic conditions, that small 

springs occur in the canyon of the lateral streams, such as Alkali, 

Cold Spring, and Bennett creeks, but as to the fulfillment of this 

predication I am not informed.

West of the mouth of Rattlesnake Creek, and near the point where 

Canyon Creek joins Snake River, large springs again occur. In that 

region there is a broad, uneroded plain leading from Snake River 

Canyon to the mountains north of Mountain Home. The canyon of 

Canyon Creek is short, and does not furnish an exception to the Statement just made. For a distance of about 2 miles or more above the 

mouth of Canyon Creek soft sand and beds of gravel occur beneath the 

lava forming the upper portion of the canyon wall, and strong springs 

come out of the talus slopes and landslides encumbering the portion of 

the canyon's border below a prominent rim rock. These springs appear 

at a horizon about 500 feet below the top of the canyon, and have a temperature of 69° F., or about 7° F. higher than the water of The Thousand Springs. The water of some of the springs referred to is used for 

the successful irrigation of orchards. Far more service could be 

obtained from -the springs, however, by tracing up the water that 

emerges through talus to the horizon where it issues from a pervious 

stratum, and excavating horizontal wells. By this means a larger 

volume of water could be had, and at such elevation that it could be 

used over a much larger area than is at present possible.

Canyon springs occur again, below the mouth of Canyon Creek, in 

the southeastern portion of Ada County, at Chapman's Ranch. They
RUSSF.T.T,.] CANYON SPBTNGS. 167

discharge somewhat less than 2 cubic feet per second, and are now used 

for irrigation. Other similar springs are near, but are not utilized. 

These springs come to the surface through talus' and above a stratum 

of yellowish lapilli. Their temperature is 69° F. An excellent 

opportunity is here furnished for excavating horizontal wells, and 

there is an abundance of land near at hand suitable for irrigation. It 

is safe to say that not only the springs at Chapman's ranch but the 

neighboring spring a few hundred yards to the east could be developed 

so as to yield much more water than they now deliver.

The portion of Snake River Canyon from Chapman's ranch westward 

to the Idaho-Oregon boundary has not been visited by me, and what 

the conditions are in respect to the presence or absence of canyon 

springs is unknown.

In Bruneau Valley, near Plot Spring post-office, a number of large 

hot springs come to the surface and are utilized for irrigation. The 

temperature of one of these is 109° F. Still more remarkable springs 

occur from 5 to 6 miles up Hot Spring Creek, where its canyon is 

narrow. One of the springs has an estimated volume of 4 cubic feet 

per second, and a temperature of 109° F. While the high temperature of these remarkable springs suggests that they come from deep 

fissures, no other evidence that such is the case was obtained during 

my hasty visit. The canyon or valley in which they occur is fully 1,000 

feet deep, and there is little doubt but that they are of the canyonspring type, but for the most part they rise in the bottom of a canyon 

instead of issuing from its sides. In places, however, as on Hot Spring 

Creek, they gush out from the canyon wall at an elevation of approximately 100 feet above its bottom. These springs, although developed 

to some extent by vertical borings, as will be described more fully 

later in connection with the records of other artesian wells, can easily 

be made to yield far more water than they do at present.

The marked success that has attended the excavation of the two 

horizontal wells near Hagerman, and also the concentration of the 

outflow of water secured by a similar method at The Thousand Springs, 

is highly encouraging to the hope that a great development of the 

canyon spring described above may be attained.

There need be no hesitation in concluding that results similar to 

those just referred to may be had at a large number of localities. 

Wherever a canyon spring appears, there is an opportunity to increase 

its flow and in many instances to obtain water at a higher level than 

it now comes to the surface, for the reason that the water usually 

issues from talus and the true source is concealed. The main difficulties are the clearing away of the fallen blocks of stone that encumber 

the lower portions of the canyon walls, and the discovery of the edge 

of the water-bearing stratum. In some places the murmur of the 

water in flowing through the talus will assist in doing this. Where
168 SNAKE EIVEE PLAINS OF IDAHO.' [BOLL. 199.

such a guide is absent, pits should be sunk at various horizons, beginning where the water is known to be present and extending up the 

canj^on walls until the outcrop of the supplying layer is discovered. 

In some instances it will be more economical to begin at the top of a 

talus slope, above a spring, and clear away the stones in a descending 

direction, thus avoiding the danger of working at the bottom of a 

loose mass of debris.

When the precise horizon at which tunnels should be excavated is 

learned, it will serve to indicate where other similar excavations in the 

same neighborhood should be made, but such deduction can not be 

carried to a distance, for the reason that the lava sheets exhibit great 

and frequently abrupt changes in thickness. As previously explained, 

while the surface of a lava sheet may be horizontal, or essentially so, 

for many miles, its bottom may be markedly irregular. Another 

suggestion which may be of value is that the water escaping into a 

canyon from its walls Hows over the surface of an impervious stratum. 

If, then, a bed of clay or compact lapilli (which in Snake River Can3^011 is usually dull yellowish, with black glass-like grains) is encountered in excavating, it is evidence that water, if present, will occur at 

the summit of the bed.

It need scarcely be mentioned that where fissure springs occur low 

in a canyon, and even in the central part of a flat-bottomed valley, as 

they do at times, the escape of the water being perhaps through fissures of small depth, vertical instead of horizontal wells must be excavated or drilled in order to increase the flow. Some assistance in 

reference to choosing a location for a horizontal well, method of development, etc., may be had by consulting a previous report n relating to 

the Columbia River lava, and associated formations.

FISSURE SPRINGS.

Fissure springs are not abundant in the portion of southern Idaho 

examined by me, and, so far as can be judged from the report of 

others, are of rare occurrence throughout the entire extent of the 

Snake River Plains. The Boise Hot Springs, situated on a fault 4£ 

miles east of Boise, are of small volume, and have a temperature, as 

stated by Lindgren in the Boise folio, 6 varying from 120° F. to near 

the boiling point. The belt of faulting on which these springs are 

located, extends for several miles in a southeast-northwest direction, 

and near it and about midway between the springs and Boise artesian 

wells, described later, yield a large volume of water with a temperature 

ranging from 75° to 170° F.

About 8 miles northeast of Mountain Home, a mile south of the

a I. C. Russell, Geology and water resources of Nez Perce County, Idaho, Water-Supply and Irrigagatiou Paper No. 54 U. S. Geol. Survey, 1891. 

l> Geologic Atlas U. S., folio 45.
RUSSELL.] FISSURE SPRINGS. 169

line of displacement which defines the junction of the Snake River 

lava with the rhyolite of Mount Bennett, there is a small group of hot 

springs, rising through lava. For the sake of brevity, .I. shall term 

them the Mountain Home hot springs. Their combined discharge is 

about 2 cubic feet per second and their range in temperature is from 

103° to 167° F. The water from this group of springs forms Plot 

Spring Creek, which flows to Bennett Creek.

Small springs, with a temperature of 131° F., occur at the right or 

southern banks of Snake River, about 4 miles above the mouth of 

Salmon River. The water rises through recent alluvium deposited by 

the river, and the true orifice from which it comes is not visible. 

Most probably there is a fissure in the solid rocks beneath the alluvial 

floor of the valley. A small warm spring, known as Poison Spring,, 

occurs in the canyon of Salmon River, about 8 miles above its junction 

with Snake River Canyon.

Near the head of Little Valley, about 9 miles west of Bruneau, there 

is a small hot spring, which rises through soft, white lake beds (probably sediment deposited in Lake Idaho) which has a temperature of 

101° F. Five drill holes, put down to a depth of 40 feet in the immediate vicinity of this spring, resulted in a marked increase in the outflow. The discharge is now about one-half cubic foot per second. 

The wells are not cased, and there is reason to believe that larger holes, 

with proper casing, would lead to a greater discharge.

In reference to the development of fissure springs, the fact should 

be borne in mind that the water in most instances rises through nearly 

vertical cracks, and may not have great freedom of discharge. When 

the water rises through stratified sedimentary beds or lava sheets, the 

chances are that there is great lateral dispersion or leakage, only a 

small part of the discharge that comes from the more deeply seated 

portions of the fissure actually reaching the surface. In general, 

fissure springs are similar to uncased artesian wells, but owing to 

probable irregularities in the fissures and the many chances they are 

exposed to of becoming clogged, it is to be presumed their surface 

outflow, in many instances, can be increased.

In the case of each of the warm or hot springs mentioned above, 

to which may be added a mud spring situated northwest of Mountain Home, and on the Overland road midway between Dry and 

Canyon creeks, there is no doubt that an increase and possibly a 

great discharge can be secured by drilling vertical wells. Such wells 

should be put down within a few feet of the springs, and continued, if 

practicable, to the depth indicated by the temperature of the spring 

water unless success is attained at less depth. In the case of Mud 

and Mountain Home hot springs the pioneer drill holes should be put 

down to the south of the spring in each case, and about 50 feet from 

it. The reason for this is that most probably these springs are sit-
170 SNAKE RIVER PLAINS OF IDAHO. [BULL. 199.

uated on faults, which incline downward to the south at a high angle 

in reference to a horizontal plane. The depth to which it would be 

justifiable to continue drilling in the case of the Mountain Home hot 

springs, as indicated by their temperature, is about 5,000 feet. This 

is on the assumption that the temperature gradient in the Snake River 

lava is one degree for each 45 feet, as indicated by the wells along the 

Oregon Short Line Railroad. This assumed gradient will no doubt 

be found incorrect when more observations are available, but it probably indicates the minimum depth to which drilling would have to be 

carried to reach the stratum from which the water rises in the spring 

referred to. There is, however, a chance that an open fissure that 

w'ill yield an abundant supply of water will be struck at less depth. 

The drill hole put down for the purpose of developing these and other 

similar springs should be at least G inches in diameter, and thoroughly 

cased, to prevent all possibility of an escape of water on the outside 

of the casing. In seeking to develop springs in this manner when 

water, even in small amounts, of the same temperature as that rising 

in the spring is encountered, it will probably be desirable to explode a 

charge of dynamite in the hole with the hope of so shattering the rock 

that a free communication with the cracks through which the spring 

water rises may be obtained.

It is scarcely necessary for me to urge that efforts should be made 

to develop the Mountain Home hot springs, since there is abundant 

land near them which could be irrigated. It may be found, however, 

that they are of more value for bathing purposes, or even for furnishing warm water in Mountain Home, than for irrigation; but even if 

these demands are not assured, there is sufficient justification for their 

development for irrigation purposes. The conditions at Mud Springs 

are less favorable than at the Mountain Home hot springs, but are 

sufficiently promising to warrant a trial.

In brief, I may state that wherever warm or hot springs rise on the 

Snake River Plains an attempt should be made to enlarge them and 

to prevent their waters from escaping by percolation. By this 1 

mean that an open pipe should be provided in which the water may 

rise, in place of the fracture provided by nature, and that the space 

between the outside of the pipe and the inner surface of the bore hole 

at the bottom of the pipe should be packed so as to prevent leakage. 

This suggestion is made with the understanding that the pipe has been 

put in place after all necessary tests have been made for the purpose 

of discovering precisely where the water enters the bore hole. The 

lower end of the pipe should be just above that locality.

A spring developed in the way suggested, when a surface flow of 

water is obtained, becomes an artesian well. Probabty in most cases 

of this nature, however, the water does not come from a well-defined 

artesian basin or artesian slope, but fr.mi irregular and what may be
RUSSELL.] WELLS. 171

termed accidental fissures. A fissure spring may, however, be due to 

the leakage of either an artesian basin or an artesian slope, and is at 

least a sure indication that water in a subterranean reservoir of some 

kind exists under sufficient pressure to force it to the surface. In an 

arid region every such indication should be tested in case the water 

can be utilized.

Three miles north of Mountain Home, and at an elevation of about 

110 feet above the town, there is a spring known as Bennett Spring, 

near which a drill hole 6 inches in diameter has been put clown to a 

depth of 50 feet, all in basalt. The casing of this well is defective and 

 water rises both within and around it, as well as from natural openings 

near at hand. At the time of my visit, August 2, 1901, this imperfectly developed spring was discharging about one-half cubic foot per 

second. The temperature of the water was 55° F. From the assumed

temperature gradient given above the depth from which the water rises 

is judged to be about 225 feet. The water is not only cool, but, so far 

as one can judge by tasting, is of excellent quality. Mr. Bennett, the 

owner of the well, informed me that it flows continuously, but that the 

supply decreases in summer; other persons have stated that it sometimes becomes dry, and expressed the belief that it is fed by seepage 

from the Mountain Home reservoir or its feeding canal. In reference 

to this last statement, 1 would say that the natural conditions indicate 

that an escape of water has occurred for many years, and that most 

probably the spring is due to a weak discharge of water from a shallow fissure.

On account of the favorable location of the Bennett Spring, the excellence of its water, etc., it is highly desirable that an effort be made to 

increase the flow. The present drill hole should be tested in order to 

learn how much water it will deliver when all leakage is stopped, and 

then deepened to at least 225 feet. By suitable tests the most favorable water-bearing horizon could then be determined, and, if desirable, the rocks at that horizon should be shattered by an explosion of 

dynamite. With the information thus "gained, if favorable, several 

other holes should be drilled within a radius of 200 feet of the present 

well. It is not improbable that this spring can be made to yield sufficient Avater for the present needs of Mountain Home.

WELLS.

For convenience, we may classify wells as, first, surface or earth 

wells, deriving their water by percolation from the surface sheet of 

rock waste, usually shallow and represented by the ordinary house 

wells of humid regions; second, rock wells, usually deep, penetrating 

the unaltered rocks beneath the surface sheet of rock waste, if any is 

present, and obtaining from pervious strata water which may be under 

some pressure, but which does not rise to the surface; and third, artesian wells, from which there is a surface overflow.
SNARE ftivE& PLAINS OF IDAHO. - [«««.. i«.

SURFACE WELLS.

On the Snake River Plains ordinary surface wells, such as are common in humid regions, are seldom possible. Where streams coming 

from the mountains have spread out flood plains or alluvial fans surface wells, however, are sometimes successful, the water supply being 

furnished by the outward percolation from the streams themselves and 

not by direct precipitation on the adjacent surface. Such wells are 

situated, for the most part, in canyons and stream-cut valleys. Their 

depth is regulated by the height of the surface at the locality chosen 

above the bed of an adjacent stream.

A modification of the process just referred to is to be seen where 

water is spread over the land for purposes of irrigation. In such 

instances a part of the irrigation water sinks below the surface and 

may saturate the subsoil. When the soil and subsoil are porous a 

large amount of subsurface water is stored more or less permanently 

in this manner, and furnishes a supply for surface wells. On isolated 

ranches wells fed by surface water from irrigation are not, perhaps, 

objectionable, but when towns are supplied in this manner a serious 

disarrangement of sanitary conditions results. One instance of a 

town which depends on shallow surface wells for water for household 

uses, and where the adjacent gardens and fields are irrigated, is furnished by Mountain Home. This town has a population numbering 

about 550; many of the houses are surrounded by gardens and orchards; 

the subsoil is gravel; there is no sewerage system; shallow cesspools 

are numerous and mostly in an insanitary condition; numerous stables 

and poultry yards are present, and the surface is flooded from time .to 

time for purposes of irrigation. The water, after standing on the 

surface, in part percolates downward into the gravelly subsoil, which

is underlain by an impervious stratum, and which is penetrated by 

wells ranging -in depth, usualty, from 15 to 20 feet. A more insanitary arrangement could scarcely be devised, yet Mountain Home is a 

typical example of many communities in the arid region. Strange as 

it may seem, practically no attempt is made in the majority of these 

towns to insure sanitary conditions.

As previously pointed out, ordinary surface wells are analogous to 

hillside springs. As the subsoil in arid regions is not saturated by 

direct precipitation, hillside springs are absent, and surface wells are 

not as a rule practicable.

EOCK WELLS.

The conditions which favor the occurrence of canyon springs also 

insure the success of deep wells which reach a water-bearing stratum. 

In the Snake River Plains, where deep borings have been made, water 

has generally been obtained. It is usually under pressure, so that it
RUSSELL.] BOOK WELLS. 173

rises some distance up the drill holes. Reference is not here made to 

flowing wells, which will be considered later.

Examples of wells which penetrate the stratified deposits beneath 

the Snake River Plains are furnished by those drilled by the Oregon 

Short Line Railroad between Pocatello and Caldwell. A list of 

these wells, with their depth, has been kindly furnished by W. H. 

Bancroft, vice-president and general manager of the Oregon Short 

Lino Railroad. The height to which the water rises and the temperatures recorded are from observations made by Mr. Scott Turner.

Wdl records along Oregon Short Line Railroad.

Location of well.

Wapi ......................................

Minidoka. ..................................

Kimarna. ...................................

Owinza. ....................................

Bliss ........................................

Cleft .......................................

Mora. ......................................

Nampa .....................................

Total depth.

Fed. 

250

425

325

401

483

450

390

600

380

114

Depth of 

water.

Feet.

375

265

341

430

530

40

Temperature.

Dctjrm F.

55

56

54 . 70

73

70

61.5

The success of these and other deep wells is good assurance that 

water can be had over large portions of the Snake River Plains if 

pumping can be resorted to. .Near canyons the depth at which 

springs appear in their wells or bottoms indicates the depth at which 

rock wells would 'be successful, but the springs must, in most 

instances, be on the same side of a canyon as the site of the proposed 

well. If no springs occur in the canyon, wells located on the adjacent 

plains must be continued to a horizon below the canyon bottom 

before water can be expected to flow into them. Owing to irregularities in the thickness of the lava sheets, no accurate prediction can 

be made as to the depth to A\7 hich a well should be carried at a distance 

from cai^on springs, but in general can perhaps be assumed to be not 

less than 300 or 400 feet. It would not be surprising if in the broad 

plain tract, in the central part of which Big Butte is situated, rock wells 

would be successful at a depth less than that just stated, or from 150 

to 200 feet, but no tests have been made to show the truth of this 

assumption.

An instructive result, based on the temperature of the water in the 

wells in the above list, is that the increase in temperature with depth 

is greater than the normal. As indicated by the data given (but 

not including the well at Narnpa), the temperature gradient beneath 

the Snake River Plains is approximately 1° F. for each 45 feet below
174 SNAKE EIVER PLAINS OF IDAHO. [BULL. 199.

the stratum of no seasonal variation. This high rate probabty indicates that the lava sheets have not as yet completely cooled, but in 

part the abnormally high temperature may be due to fissure springs 

rising beneath the lava, and contributing to the water supply of canyon 

springs and of rock and artesian wells.

AETESIAN WELLS.

A considerable number of artesian wells in northern Idaho are now 

flowing, but data concerning only a portion of them have as yet been 

procured.

Included with an account of several artesian wells situated in the 

Boise quadrangle, and described by Lindgren in the Boise folio," are 

those which supply Boise. These are located near the immediate 

border of the Snake River lava and are highty suggestive as to the 

possibilities in other similar situations.

There are two groups of wells near Boise one in Hull Gulch, 1£ 

miles north, and the other about 2 miles east of the city. The first 

group consists of eight wells, six of which are reported to be 400 feet 

deep, and one 619 feet, but some changes were made during the 

summer of 1901, the results of which are not at hand; their combined 

flow is about 670 gallons per minute. The water is cold.and of good 

quality. The second group consists of three wells, ranging in depth 

from 394 to 455 feet, which discharge about 550 gallons of water per 

minute, having a temperature of 170° F. This water is conducted to 

Boise in pipes and extensively used for heating purposes, baths, etc. 

Other hot wells are located in the same vicinity; they are described in 

the Boise folio.

The unique water supply of Boise, consisting of both hot and cold 

water, furnished by flowing wells at small expense, makes it highly, 

important to learn whether similar conditions exist near other towns. 

The only other town similarly situated in reference to geological conditions is Mountain Home, some statement concerning the water supply 

of which has already been made, and to which more attention will be 

given later.

BRUNEAU VALLEY.

In the upper portion of Bruneau Valley there are three flowing 

wells, each 2£ inches in diameter, which, together with the numerous 

hot springs of the same region briefly described above, show that an 

abundance of water exists at a moderate depth under sufficient pressure to cause it to rise to the surface if openings are. provided.

On W. N. Roberson's ranch, about 2 miles north of Hot Spring 

post-office, and on the west side of the valley, a drilled well having a

a Geologic Atlas U. S., folio 45.
KUSSBLL.] ARTESIAN WELLS. 175

depth of 240 feet delivers about 7 gallons of water per minute, having 

a temperature of 109° F. This well is within a few feet of a large 

hot spring having the same temperature, the flow of which was not 

diminished when the well was drilled. The elevation of the surface 

at this point, by aneroid, is 2,750 feet. The section passed through, 

as reported from memory by Mr. Roberson, is as follows:

Section % miles north of Hot Spring ^post-office.

Granular black layer, lik<

Total depth, about

(lake beds) ...............................

3 basalt (volcanic lapilli?) ..................

Feet.

236

4

240

Inches.

10

(«)

10

« Several.

The water is used for household purposes and for irrigation.

Nearly opposite the well just described, on the east side of the 

valley and at an elevation approximately 50 feet higher, a well drilled 

to a depth of 230 feet, on land belonging to Mr. A. H. Pence, resulted 

in a small surface flow.

On Mr. B. Whitson's ranch, situated on the eastern side of the valley, about 3 miles north of the two wells just mentioned, where the 

surface elevation is by aneroid 2,750 feet, a well 700 feet deep discharges about one-third cubic foot of water per second. The temperature is reported to be 90° F.

These three wells derive their water from different depths, and seem 

to indicate that water under pressure exists in at least three disconnected pervious layers, or else that a source of supply more deeply 

seated than has been reached by any of the drill holes yet made charges 

porous beds above it through fissures. The abundance of hot springs 

in the same vicinity apparently favors the latter hypothesis.

As will be shown below, the artesian wells in Bruneau Valley are 

within the border of a large structural basin, which it is convenient to 

designate the Lewis artesian basin.

LITTLE VALLEY.

Near the head of Little Valley, 9 miles west of Bruneau, there are five 

flowing wells, which range in depth from 150 to.215 feet, each drilled 

with a 2£ inch bit, and poorly cased. The water is of good quality; 

temperature is about 67° F. The flow varies somewhat with seasonal 

changes, being greatest in winter and spring and least in summer and 

fall. In most instances the pipes have become clogged and the dis-
176 SNAKE RIVER PLAINS OF IDAHO. [nuu,.199.

charge is small. One of the stronger .of these wells delivers in August 

a gallon of water in seven minutes, and is said to discharge about a 

gallon per minute in winter. Neighboring springs have various temperatures, ranging from 56° to 59° F.

These shallow wells, some of which began to flow when a depth of 

60 to 70 feet was reached, are in a broad, deeply alluvial-filled valle}7 

and evidentty depend for their water supply on an alternation of pervious and impervious beds in the alluvial deposits. The source of the 

water of the several cold springs is, no doubt, the creeks which flow 

from the mountains southward, but the wells must be supplied from 

a deeper source.

Little Valley-is situated within the Lewis artesian basin, and at a 

lower level than the surface at the flowing wells near Hot Spring 

post-office, in Bruneau Valley, but the-wells referred to above do not 

furnish a test of what may be termed the true artesian condition.

The partially develdped hot spring in the upper portion of Little 

Valley, described above, is about a mile east of the shallow artesian 

well just referred to, and presumbly derives its water from a deep 

source.

HOCK CREEK HILLS.

In the valley of Rock Creek, about 3 miles south of Rock Creek 

post-office, Cassia County, on Mr. E. M. Crockett's ranch, a 6-inch 

well put down in 1899 has a depth of 275 feet. The water rose at 

first to a height of about 20 feet above the surface, but owing to leakage due to imperfect casing has since ceased to flow. The water stands 

about 3 feet below the top of the well.

Half a mile south of the Crockett well, on Jones Brothers' ranch, 

two wells drilled in 1899, each 6 inches in diameter, imperfectly cased,

now discharge about 2 cubic feet of water per second. The temperature is about 75° F., but was not measured. One of them is 90 feet 

deep, and the other, 30 j^ards distant, 115 feet deep.

The three wells on Rock Creek are. situated in a deep canyon-like 

valley among hills of stratified rhyolite, where the rocks have been 

considerably disturbed. No structural artesian basin is definitely 

known to be present, but further study may show that this region is 

an extension eastward of the Lewis artesian basin. Springs are 

numerous in the same region and supply Rock Creek, which flows 

throughout the year to below Rock Creek post-office,.where its water 

is all used for irrigation.

The geologic conditions in the Rock Creek Hills are closety similar 

to those in the rhyolitic mountains to the north of Mountain Home, 

where springs are also abundant, and the success of the wells drilled 

at the former locality suggests that equally favorable results should be 

expected on Long Tom and Syrup creeks and about Mount Bennett.

In the neighborhood of the Rock Creek Hills several borings have
RUSSELL.] AETESIAJS" WELLS. 177

oeen put down, with various results. More or less definite reports concerning them are here presented:

At Rock Creek post-office a 6-inch drill hole 300 feet deep failed to 

reach water under sufficient pressure to cause it to rise to the surface. 

Water stands about 40 feet below the top of the well and is pumped. 

The well is imperfectly cased, and no adequate tests of the pressure of 

the water have been made. It seems probable that if this well should 

be properly cased a surface flow would result.

Near Dry Creek, about 10 miles east of Rock Creek post-office, and 

about one-half mile from the foothills to the south, a cb'ill hole, situated near a warm spring, is reported to have a depth of between 200 

and 300 feet, and to discharge a small amount of warm water. Judging from reports, this well is on the Snake River Plains, where the 

surface rock is basalt.

About 4 miles west of Rock Creek post-office, on the McMullen 

ranch, near the border of the Snake River Plains and adjacent to the 

Rock Creek Hills, a 6-inch well, 50 feet deep, is reported to discharge 

a small stream of warm water. About 10 miles farther west what 

is known as Wild Horse well is said to be 75 feet deep and to furnish 

a small supply of warm water.

Of the several flowing wells in and about the Rock Creek Hills, I 

was enabled to visit only the three on Rock Creek, but the success of 

these and the surface discharge from the others referred to is evidence 

that water exists under pressure beneath a region many square miles 

in area. Whether or not there is a continuous water-charged stratum 

in this region at a moderate depth beneath the surface is not demonstrated, but the facts in hand are such as to justify a thorough test. 

It is highly desirable that the well at Rock Creek post-office and also 

the wells east and west of that locality should be continued downward 

several hundred or possibly 1,000 feet, in order to determine positively 

the actual conditions.

There is a vast amount of fine land about the Rock Creek Hills, and 

the indications are that artesian water can be had for the irrigation of 

a considerable portion of it.

UNSUCCESSFUL WELLS.

In addition to those places at which the flowing wells briefly described 

on the preceding pages were obtained, attempts have been made to 

obtain flowing wells at various other localities, principally, so far as I 

am aware, on the northern border of the Snake River Plains. Thus 

far these attempts have all been unsuccessful.

At Shoshone, a well was drilled in 1890, with the hope of obtaining 

flowing water for town purposes, to a depth of 280 feet, all in lava, 

but no water was reached. 

Bull. 199 02 12
178 SNAKE RIVER PLAINS OF IDAHO. [BULL. 199.

At Gooding, 16 miles west of Shoshone, a drill hole is reported to 

have been put down in 1890 to a depth of 155 feet, which, after passing 

through lava, entered clay; water rose to Avithin 110 feet of the surface. Again, one-fourth mile south of Gooding, a drill hole 185 feet 

deep passed through lava and entered clay; whether water was reached 

or not, was not learned.

At Lee's ranch on Slater Creek, approximately 25 miles northwest 

of Mountain Home, and near the northern border of the Snake River 

lava, a well put down in the bottom of the small valle}7 cut by the 

creek, has a depth of about 85 feet, but failed to reach water.

At Howe, on Little Lost River, a well drilled through lava to a 

depth of 200 feet reached water under sufficient pressure to cause it 

to rise 25 feet or to within 175 feet of the surface. The casing of the 

well is defective, and to what height the water would rise if proper 

care were taken in making a test is not known.

IMPERFECT CASINGS.

The inferences to be drawn from the several artesian wells and 

unsuccessful borings referred to in the past few pages are by no 

means so instructive as they would be if the pressure of the water 

met with in most instances were known. So far as I am aware, none 

of the artesian wells now flowing and none of the wells in which 

water rose some distance but failed to reach the surface are properly 

cased. Lack of care in this respect has caused failure, or but. trifling 

returns, Avhere a strong flow of Avater can be easily and cheaply 

obtained. The methods employed to prevent leakage in artesian wells 

are briefly described in my report on Nez Perces County, already 

referred to, and in several of the books and papers cited in it, but can 

not be repeated at this time.

LEWIS ARTESIAN BASIN.

From near the mouth of Clover Creek Avestward, at least as far as 

the eastern boundary of Ada Count}^, the Snake River lava and associated sedimentary beds have been bent into a broad, gentle downward fold or syncline, the longer axis of Avhich has a nearly east-west 

trend, and pitches A^ery gently westward. The strata forming this 

basin underlie the plains both north and south of Snake River, and 

judging from what is knoAvn concerning the way in Avhich the formations Avere deposited, or poured out as molten lava, the pervious 

beds, if any are present, are in a position to be charged with water 

from the mountains bordering the portion of the Snake River Plains 

referred to on the north and'south. These conditions are such as 

produce artesian basins, and, so far as can be judged from the observed 

facts, this basin should yield flowing Avells, providing the requisite succession of pervious and impervious beds is present The only direct
KUSSELL.] AETESIAW WELLS. 179

evidence we now have on this point is the meager records of the drilled 

well in Bruneau Valley. The wells referred to show not only that 

pervious beds occur beneath impervious beds, but that water under 

sufficient pressure to force it to the surface is present. Several hot 

springs also suggest the same conclusion.

My judgment, based on all the facts accessible, is that the Lewis 

artesian basin is of large size and well worth careful testing by means 

of the drill. The extent of the basin west of Elmore County is 

unknown, and the assumption that it is a closed basin and reaches the 

Idaho-Oregon boundaiy is based on a general knowledge of the geology 

of southwestern Idaho and the fact that Snake River below Weiser 

is flowing over impervious rocks older than the Payette formation.

As to the height, to which the water will rise in the artesian head, 

the only basis for judgment at present is the surface elevation at the 

flowing wells in Bruneau Valley. None of these wells, so far as I have 

been able to learn, are tightly cased, and they probably do not show 

the full height to which water would rise under more favorable conditions. B}r aneroid measures, the artesian head shown by the wells in 

Bruneau Valley is, as previously stated, at an elevation of about 2,750 

feet above the sea. The method of measuring by means of aneroid 

barometers, the only one I was enabled to employ is, as is well known, 

defective, and the elevation just given maybe a hundred feet in.error. 

With the assumed height to which water will rise, artesian wells may 

be expected to be successful at any locality west of the mouth of Clover 

Creek at least as far as 7 the eastern boundary of Ada County and the 

southward prolongation of that line across Owyhee County, where the 

surface elevation is less than 2,750 feet. The land which is below 

this level is situated in the canyon of Snake River in Bruneau and 

Little Valley. So far as can now be judged, there is no hope that 

water under sufficient pressure to rise to the surface of the plains 

bordering the canyon and valleys just named, is present, but this is a 

matter that should be determined by experiment.

In order to test the predictions based on geological structure, etc., 

a pioneer well should be put down, with all the well driller's skill that 

can be commanded, at the most favorable locality, and a careful record 

kept of the strata passed through. It is unnecessary to add that the 

pressure of each water supply reached should be accurately measured. 

Favorable places for such a test well occur at severariocalities in the 

vicinity of Snake River, between the mouth of Clover Creek and the 

east boundary of Ada County and in the lower portion of Bruneau 

Valley. -1 would name, especially, Glenns Ferry and Bruneau. In 

the absence of accurate topographic maps, it is impossible to state at 

what depth water should be reached, but what is scarcely more than a 

guess places it at between 500 and 700 feet. The demand for water 

is so great, however, and the conditions, so far as can be judged from
180 SNAKE BIVEK PLAINS OF IDAHO. [BULL. 199.

a hasty reconnaissance, are seemingly so favorable, that the people who 

are interested in the development of this region can well afford to 

continue drilling to a depth of 1,000 or 2,000 feet, unless water is sooner 

reached. To make a complete test, drilling should be continued until 

the Snake River lava and its associated lacustral beds are passed 

through. Beneath these formations it is probable that the drill will 

strike either granite, rh}^olite like that which forms Mount Bennett and 

the Rock Creek Hills and which appears also at Shoshone Falls, or 

quartzite. When the drill reaches rock like any of them, or some 

other rock clearly distinct from the Payette formation or the Snake 

River lava, the possibilities for obtaining artesian water will have 

been exhausted. Deep drilling is also justified for the reason that 

the sheets of lava which supply the great springs, in the vicinity of 

Hagerrnan dip gently westward, as maV be seen between the mouth 

of Clover Creek and Bliss, and pass beneath the region included in 

the Lewis artesian basin. As the continuation of a lava sheet after 

it disappears from sight is uncertain, it can not be said from definite 

evidence that the open, water-charged lava sheets referred to have a 

wide extent west of where they dip beneath the level of Snake River, 

but there is a possibility that they extend far and are abundantly water 

charged. The manner in which the sheets of basalt in the western 

portion of the Snake River Plains vary in thickness is an important 

matter in reference to the search for artesian water, but one concerning which no predictions seem possible. This and other qualifying 

conditions can be discovered only by the use of the drill.

SHOSHONE ARTESIAN SLOPE.

Judging from surface elevation and the nature of the rocks exposed 

in the north wall of Snake River Canyon between Shoshone Falls and 

Bliss, the strata of lava, associated lacustral deposits, etc., beneath the 

plain to the south and southwest of Shoshone slope from the mountains toward Snake River. Coupled with this fact is the marvelous outpouring of water from the north wall of Snake River Canyon between 

Shoshone Falls and Bliss. This water, although no doubt supplied 

in part by precipitation on the surface of the Snake River lava, comes 

mainly from the mountains to the north. The great springs referred 

to are fed by lost rivers and by the water which disappears by percolation on the northern border of the Snake River lava sheets. There is 

thus evidence of a strong underflow beneath the lava plain to the south 

and southwest of Shoshone. For these reasons I venture to term the 

region referred to the Shoshone artesian slope, although the name 

will be justified only when the drill demonstrates that the water is 

under sufficient pressure to cause it to rise to the surface.

The nature of an artesian slope has already been explained, and 

persons familiar with the conditions existing in the triangular area,
RUSSELI,.] ARTESIAN WELLS. 181

containing- some 400 square miles, having Shoshone, Bliss, and Shoshonc Falls at its corners, will, I think, agree with me in the conclusion that the}^ are sufficiently favorable to the hope of obtaining flowing water to be deserving of a thorough test. The rise of the water 

in a hole drilled in the covering layer of an artesian slope depends on 

the friction of flow in the water-bearing la}rer below the site chosen. 

The less pervious the layer, down to a certain indefinite limit, the 

higher the water will rise with a given slope. In the case, of the pervious beds beneath the "Shoshone triangle" there is a remarkably 

free passage for the water. On the other hand, the volume of water is 

great, and this perhaps more than counterbalances the adverse condition resulting from freedom of natural escape, and favors the hope 

that water would rise to the surface if drill holes properly cased were 

put down. There is the same necessity for an impervious cover to 

the water-bearing stratum in an artesian slope that there is for an 

impervious layer above the pervious bed in an artesian basin. In the 

"Shoshone triangle" the covering bed, as indicated in Snake River 

Canyon, is basalt, but above the lowest known water-bearing bed 

there are at least three strata of lava, and sedimentary beds may occur 

between these. The presence of such beds has not been proved from 

observation, but the fact that the water forming the springs along 

Snake River comes from three separate pervious beds is sufficient 

evidence that practically impervious rocks occur between them.

I have dwelt on these probabilities at some length in order to place 

the reader who is familiar with the "Shoshone triangle" in a position 

to judge for himself whether the chances of obtaining flowing water 

are sufficiently good to warrant making a test. In my judgment it 

would be worth while to put down a pioneer well to a depth of 700 or 

1,000 feet, at a distance over 6 miles from the brink of Snake River 

Canyon, anywhere in the triangular area referred to where broad tracts 

of fine land occur. The locality chosen should be at as great a distance 

as possible from elevations like Flat Top and Notched buttes, which 

indicate the position of old volcanic vents.

POSSIBILITY OF OBTAINING PLOWING WELLS IN ALLUVIAL DEPOSITS.

As has already been stated, the border of the Snake River Plains 

is covered in part by alluvium brought down by streams from the 

adjacent mountains. There is reason for believing also that similar 

deposits were formed from time to time between the successive eruptions that furnished the Snake River lava. In such alluvial deposits 

generalty an alternation of pervious and impervious beds occurs. 

The pervious beds have in a general way the shape and associations 

described on a previous page under the term "artesian Avedges."

The conditions here referred to may be expected to occur at any of 

the localities where streams flowing from valleys in the mountains
182 SNAKE KIVEB PLAINS OF IDAHO. [BULL. 199.

emerge onto the border of the Snake River Plains. In order to form 

" artesian wedges" of sufficient size to be of value as a source of water 

supply,'the alluvial deposits need to be of considerable extent and 

thickness and to occur at the mouths of valleys down which there is a 

considerable flow of water. These conditions are best fulfilled, so far 

as I have been able to learn, where the valleys of the "Lost River 

country " open out on the Snake River Plains. In the lower portions 

of the valleys through which Big Lost River and the similar streams 

as far to the northeastward as Beaver Creek emerge onto the plains, 

the conditions are such as to Avarrant the drilling of wells to a depth 

of at least 500 feet in the hope of obtaining flowing water.

In the valleys just referred to there are deep accumulations of alluvium and fine examples of alluvial fans. At the mouth of each lateral 

gorge along the sides of these valleys there are local alluvial fans, which 

unite with a similar deposit in the main valley. The bottoms of the 

valleys of Big Lost and Little Lost rivers, Birch Creek, etc., are 

occupied by immense compound alluvial fans which extend far out 

onto the Snake River lava and there expand widely. Similar alluvial 

deposits were no doubt formed during the intervals between the eruptions that spread out the Snake River lava, and such deposits beneath 

the surface lava sheets and interbedded with the subsurface sheets 

are in a position to become water charged. For these reasons it seems 

worth while to search for water under pressure on the border of the 

Snake River plains, adjacent to or in front of- the entrances of the 

lateral valleys referred to. One such attempt has already been made 

at Reno, as has been stated, and water under pressure was discovered, 

which did not rise to the surface. This test, however, was imperfect, 

as the drill hole was not properly cased, and, although counted a failure, 

is really encouraging. It is not to be expected that water will rise 

through a hole 200 feet or more deep drilled in the Snake River lava, 

unless it is properly cased, for the reason that the lava is largely 

cellular, broken by joints, etc., and would allow water to escape 

laterally.

Another similar locality, but less favorable than those just referred 

to, where the conditions hold out some hope that flowing water may be 

obtained, is at Mountain Home. At that place there is a broad 

alluvial fan laid down by Canyon and Rattlesnake creeks, which may 

contain an alternation of pervious and impervious beds. The conditions are not especially favorab'le for charging the pervious beds if 

such are present, with water, but the urgency for a water supply at 

Mountain Home is such that tests of the artesian conditions beneath 

and in the vicinity of the town should be undertaken. I venture to 

recommend that a row of borings be made at intervals of 1,000 feet 

along an east-and-west line passing through the northern portion of 

Mountain Home. Each of these boring's should be continued until
HUSSELL.] . ABTESIAN WELLS. 183

solid black lava (basalt) is reached. This will probably be at a depth 

of 150 or 200 feet. If such borings are unsuccessful, one of them, near 

the town, should be continued until the sedimentary beds, such as sand, 

gravel, clay, etc., presumably occurring beneath the highest sheet.of 

lava, are passed through and the drill enters the next lower lava sheet. 

No one can predict with certainty what results will follow such a 

series of tests as is here recommended, but there is a chance of success. 

Other suggestions in reference to a water supply for Mountain Home 

may be found on pages 171 and 172.

PROBABILITY OF THE PRESENCE OF WATER BENEATH THE EASTERN PORTION OF THE SNAKE

RIVER PLAINS. '

The largest track of waterless country in Idaho is comprised in the 

portion of the Snake River Plains lying to the north and west of Snake 

River, above Shoshone Falls. This region, measured roughly, is from 

150 to 170 miles long, and from 30 to 50 miles wide, and within it there is 

but one perennial spring the one at Big Butte, which discharges about 

one gallon cf water per minute. A portion of the northeastern margin of this immense tract, it is hoped, can be-watered from storage 

reservoirs on Henry Fork, but by far the greater part is beyond the 

possibility of irrigation from surface streams. In reference to subsurface water but little that is encouraging can be said.

The portion of the Snake River Plains here referred to is floored 

with lava, which was poured out from many vents, and is still in essentially horizontal sheets. The rocks are not cut hy streams so as to 

form canyons, nor are there other exposures by means of which the 

character of the strata beneath the surface can be judged. One can 

only surmise what the subsurface conditions are from analogy with 

the somewhat deeply dissected Avestern extension of the same formations. This analogy and the general principles pertaining to the manner in which broad basins ma}r become filled or partially filled with 

alluvial deposits, lacustral sediments, and lava flows favor the assumption that beneath the broader portion of the Snake River Plain (as, for 

example, between Kimama and Big. Butte), there is a succession of lava 

sheets and sedimentary beds. The lava, although in part in broad 

sheets, consists mainly of local flows which overlap and are probably 

relatively thin. Thicknesses of from 50 to 150 feet are to be expected. 

The sedimentary beds, if laid down as alluvial deposits, will be thickest about the border of the basin and will thin out and become finer in 

texture "toward their center, and, if deposited in lakes, will be thicker 

in their central part and become thinner and coarser in texture toward 

their margins, there merging with alluvial deposits. From these considerations it is to be expected that an alternation of pervious and 

impervious beds is present. The rocks, however, have not, so far as 

the surface sheets are concerned, been bent into, a basin shape, and
184 SNAKE EIVER PLAINS OF IDAHO. [BULL. 199.

there is no evidence of the presence of an artesian basin. While the 

surface is essentially level, the few measurements of elevation available indicate that there is a descent of approximately 25 feet to a mile 

from the region of Big Butte south westward. Under favorable subsurface conditions this would produce an artesian slope which might 

yield flowing water on drilling.

The presence of such an artesian slope has been tested in part by 

wells along the line of the Oregon Short Line Railroad at Wapi (250 

feet), Minidoka (425 feet), and Kimama (325 feet), which fail to furnish 

flowing water, but yield a supply that is raised by pumping.

As may be judged by the statements of probabilities made above, it 

is almost impossible to obtain data by means of which a judgment can 

be formed in reference to the chances of obtaining water in the region 

referred to. The evidence is negative and so far as it permits one to 

form an opinion does not favor the hope that flowing wells can be 

obtained. While there is but little if any hope of obtaining artesian 

water, it is probable that "rock wells," that is, wells in the solid rock 

but not flowing wells, drilled to a depth of from 300 to 500 feet, would 

reach water. As there is an immense tract of excellent grazing country in this portion.of the Snake River Plains, it is probable that it will 

be found practicable to establish cattle ranches there, the necessary 

water supply being obtained by pumping from rock wells. There is 

a report current among stockmen and sheep herders who visit the 

region lying southwest of Big Butte in winter to the effect that 

flowing water comes to the surface at one locality. This report is 

well worth investigating, for the reason that a single watering place 

in such an immense pasture would be of great value.

CONCLUSION.

My reconnaissance led to the following general conclusions in reference to the future development of southern Idaho:

1. The surface water supply at present available is largely wasted, 

and can by proper economy be made to yield two or three times the 

service now obtained from it.

2. Every effort should be made to divert and utilize surface streams. 

In this connection, it is evident from the work of the State engineer 

and from personal inspection that it is practicable to use for irrigation 

the entire summer flow of all the streams reaching the Snake River 

Plains.

3. The next largest source of water supply after the flow of the 

streams in summer has been fully employed is by means of storage 

reservoirs. The sites of such reservoirs have in part been indicated by 

the State engineer and the hydrographic division of the United States 

Geological Survey.

4. Drill holes should be put down at the localities suggested on a
RUSSELL.] ARTESIAN WELLS. 185

previous page for testing the artesian conditions in what has been 

termed the Lewis artesian basin, and also in the probable artesian 

slope lying southwest of Shoshone as well as in the "Hagerman bend."

5. At Mountain Home the Bennett well should be developed and drillings made in the alluvium on which the town is situated. The Mountain Home hot springs can also be developed and their water piped to 

the town if desired.. Drill holes put down along Syrup, Long Tom, 

and Rattlesnake creeks in the mountain portions of their courses 

would serve to increase the flow of these streams. Storage reservoirs 

are possible on these same creeks. Where Canyon and Rattlesnake 

and other similar creeks leave the mountains, the escape of their 

water by percolation can be checked in some instances by putting in 

dams reaching to the solid rock beneath the alluvium.

6. Every fissure spring in southern Idaho is a warrant that water 

under pressure exists beneath the surface, and in manj^ instances these 

openings can be made to deliver a greater flow than at present;

7. On the broader portion of the Snake River Plains, west of Blackfoot and elsewhere, rock wells are possible, but flowing water is probably not obtainable.

8. It is self-evident that there is but little if any use in attempting 

to put down the test wells suggested, unless the work is done by a 

skilled and conscientious driller, under the direction of a competent 

engineer. Each water-bearing stratum should be tested in order to 

determine the pressure under which the water exists, and the quantity 

available. Each well should l)e properly cased.

Flowing wells supplied by artesian basins or "artesian wedges" 

should be closed when the water is not being used. The reason for 

this is that the supply is being drawn from a reservoir that is not 

inexhaustible. Flowing wells, however, supplied by artesian slopes, 

and those which are essentially developed fissure springs, should be 

open continuously in order to keep the artificial opening clear and also 

because the water will otherwise escape by natural openings and no 

economy would result from closing the drill holes.

9. Lastly, it is painfully apparent that the control of the water supply, both for irrigation and other uses, and the sanitary inspection of 

towns and of isolated houses, should be placed in the hands of a competent engineer. While this suggestion is perhaps in a measure impracticable, as the private ownership of water is not likely to be relinquished and people will claim the privilege of living as they choose 

even though the death rate is higher than it should be, yet the present 

waste of water is so great and the prevalent ignorance or disregard of 

the laws of health so general that centralization of control or general 

education of the people is imperative.

INDEX.

A.

Pago.

Aa, Dana's description of------------------ 01

Aa near Cinder Buttes, occurrence and

characteristics of.............. 97-98

Agriculture in the region................. 28-31

Alcoves on sides of canyons, occurrence

and features of.............. 127-130

production of, conditions necessary

for........................... 129-130

Alkaline salts, depth of bed of........... 70

Alkaline soil, indications of--------------- 141.

Alluvial deposits, flowing wells in, possibility of obtaining-..,.....-. 181-183

Alluvial soils, deposition of..-.--------- 135-136

American Falls, height of ................. 28

Analyses of soils......................... 136,137

Arco, lava cone near, plate showing...... 112

Area of the region ........................ 14

Arid regions, springs in, occurrence of... 155 

Artesian basin, conditions favoring production of----.............---.. 157

section of ............................... 157

structure of, illustration of........ 156-157

Artesian slope, section of................. 158

Artesian wedge, section of................ 157

Artesian wells, flow of, methods of .... 157-158

imperfect casing of, results of........ 178

location and features of............. 174-177

probable successf ul location of....... 170

temperature of........................ 154

unsuccessful location of............. 177-178

Ascension Island, vesicular bomb from,

reference to drawing of....... 77

B. 

Bancroft, W. H., information furnished

by.............................. 173

Basalt near Cleft, fault scarp of, plate

sho wing --..-..-...............- ] 26

Basin, artesian, section of ................ 157

Beaver River, features of................. 130

Bennett Spring, features of............... 171

Big Butte, composition of.---.-...-----.-. 35,45

elevation of.--.-----------_-....-..___. 34

location and features of ........... 16,34-38

plate showing ......................... 34

slopes of, character of................. 34-35

Snake River lava near, plate showing

pressure ridges in............. 94

spring at base of ...................... 34

vegetation on.......................... 35-36

view from, features of ..-----...-..... 36

Big Lost River, features of ................ 130

Big Wood River, deflection of ........... 133

erosion by ._-.--.----.---.-_---..-.-..._ 68

volcano on.................'............ 67

Birch Creek, features of .................. 130

Bisuka, well at, depth of..........-.----... 173

Page. 

Black Butte, lava from, occurrence of

caverns in ...................... 08

lava sheets from, occurrence of depressions in surfaces of....... 101. 

location and features of .............. 66-68

Black Crater, cleft in summit of ......... 110

Blackfoot, populati on of.................. 32

Blackfoot River, upgrading of ........... 133

Blanche Crater, features of .............. 70-71

warm springs near.................... 71.

Bliss, lava stream, that entered water

near, section of................ 110

springs near ^........................ 162-163

well at, depth and temperature of ... 173 

Blue Lake alcove, view from, into Snake

River Canyon, plate showing. 128 

Blue Lakes, alcove in canyon wall at, features of ........................ .127

springs at, use of....................... 162

Boise, artesian wells in and near, features of ........................ 174

hillside springs at, temperature of ... 152 

population and features of............ 32

water supply of, character of......... 174

Boise granite, character of................ 40

Bois§ Hot Springs, features of............ 168

Boise River, irrigation from............. 31,160

Bombs from Cinder Buttes, characteristics of......-....'............... 75-79

Box Canyon, origin and features of.... 127-128

springs in, source of .................. 165

springs near mouth of ................. 163

Bradley, F. H., cited on Market Lake

craters......................... 108

cited on wind-blown sand ............ 140

quoted on lava of Snake River Plains 65,96 

report by, reference to ............... 46

Breccia in walls of Snake River Canyon,

characteristics of.............. 115

Brey, B. C., information furnished by... 70 

Bruneau, test well suggested at.......... 179

Brunean River, irrigation from.......... 30-31

Bruneau Valley, artesian wells in, location and features of......... 174-175

hot springs in, irrigation from ....... 167

wells in, elevation of artesian head

shown by....................... 179

C.

Canias River, features of................. 130

Campbell, E. D., aid by ................... 88

CanyonCreek,lavarestingon undisturbed

lake beds near, plate showing. 118 

Canyon Creek Canyon, springs in, occurrence and features of ....... 166-167

wall of, plate showing ................ 64

Canyon springs, section showing conditions favoring occurrence of. _ 150 

.187
188 INDEX.

Page.

Caiiyons, spring-formed alcoves on sides 

of, occurrence and features 

of ............................ 127-130

Canyons in the region, occiirrence and

featuresof................... 123-126

Carboniferous rocks east of Snake River,

occurrence of.................. 46

Caverns formed by lava, occurrence and

featuresof..-----...------..... 94

Chamberlin, T. C., reference to paper by. 156 

Chapman's Ranch, springs at, occurrence

and features of .............. 166-167

Cinder Buttes, aa near, occurrence and

characteristics of.............. 97-98

bombs from, characteristics of.....'.. 75-79

clots from, characteristics of --------- 75

dust and lapilli from, characteristics

of ..............................'74-75

elevation and features of highest of.. 73-74 

elevations comprising, composition of 72-73 

granite near, outcrop of .............. 41

lava from, analysis of................. 87

corrugations and arches in ....... 92-97

lava cakes from, characteristics of... 79-80 

lava flows from, plate showing pressure folds in surface of-------- 92

relative age of --....-.....--.-.-. 105-107

lava sheets from, depressions in surfaces of ...................... 101-102

lava sheets near ,flssuresand faults in 118-119 

lava streams from, features of ....... 82-87

lava surface (blistered) and corrugations on lava stream, plate 

showing........................ 90

location and features of ............. 72-112

pahoehoe near, occurrence and characteristics of........-....---.-. 91-92

parasitic cones from, features of..... 80-82

plate showing.......................... 72

relation to older volcanic eruptions

of ............................ 107-112

scoria from, characteristics of........ 75

surface features around .........---.- 89-98

vegetation on.......................... 73

volcanic bombs from, plates showing. 7G, 78 

volcanic rock from, characteristics

of......................._....... 74-80

Cleft, basalt near, plate showing fault

scarp of........................ 126

crater rings near, features of ...... 110-112

map showing...................... 1.1.0

lava at, fissure in .................... 119-120

well at, depth and temperature of.... 173

Climate, effect upon rocks of........... 144-145

relation of springs to.....----------. 154-156

Climate of the region. .................... 17-22

local variations in..................... 19

Clots from Cinder Buttes, characteristics

of............................... 75

Clover Creek Valley, hot springs in,

source of heat of .............. 153

Columbia River lava and Snake River

lava, relation of............... 60-01

Cope,E.D.,uamegiventoPlioceiieLakeby 51 

Crater rings near Cleft, map showing.... 110

plate showing .--.--....--.......--..-- 110

featuresof.......-..........---.--... 110-112

Crater walls, stratification of ............ 74

Crockett, E. M., artesian well on ranch

of, features ef ................. 176

D.

Dall, W. H., determination of fossils by . " 56 

Dana, J. D., cited on aa ................... 98

cited on lava balls.--.-................ 114

openings in lava mentioned by, explanation relative to caJhse of. 94-95 

quoted as to generic characteristics

of lava surfaces ............... 91-92

reference to............................ 88

Darwin, Charles, reference to drawing of

bomb by....................... 77

Desert varnish, formation of........... 143,144

Dikes of acid and basic rock, occurrence

of.---.----._..___.....__.......- 41

Diller, J. S., examples of desert varnish

described by.................... 106

Drillholes, suggestions relative to.-... 184-185 

Dry Creek, artesian well near, features of 177 

Dunes, sand, occiirrence and features of. 140-141 

Dust from. Cinder Buttes, characteristics

of................................ 74-75.

Dust storms, occurrence of............... 21

E.

East Butte, character of ------------------ 16

composition of........-...-..-.-..----. 45

elevation of............................ 34

location and features of--------------- 34-38

plate showing ___.___..__._ _...____..._ 34

shape of.....-..-....-.--......----.---- 38

slopes of, character of.....---..-....- 36

vegetation on.......................... 38

Eudlich, F. M.,reference to report by.... 46

F.

Faults in the region, occurrence of ----- ^ 47-48,

1.19-121 

Fauna of the region....................... 24

Perguson A., estimate of volume of The

Thousand Springs by .... 27

reference to............................ 163

Fissure eruptions, hypothesis of---------- 61-63

Folds in rocks of southern Idaho, occurrence of......-_..__--....------ 48

Forests in the region, occurrence of------ 22-23

Fortieth Parallel Survey,, reference to

reports of...................... 44

' Fossils of the region, species of........... 56-57

Tertiary (Miocene) age recorded by.. 15

G. 

Geikie, A., quoted as to origin of Snake

River lava. .................... 62

Geologic structure, relation of springs to 154-156 

Geological history of the region.......... .1.5-16

Geology of the region.................... 38-134

Giibert, G. K., examples of desert varnish

described by. ------------------ 106

reference to monograph by ----------- 79

Glenns Ferry, fresh-water shells collected

near....'........ ................ 56^

rim rock in bluffs at. origin of -------- 70

sand drifts near .............-...----.. 140

test well suggested at.............:... 179
INDEX. 189

Page. 

Gold in the region, occurrence of ........ 32

Gooding, well drilled at, unsuccessful.... 178

Granite, occurrence, character, and outcrops of..................... 15,39-42

Great Basin, canyon springs in, reason for

absence of...................... 155

fissure springs in, occurrence of.... 153,155

H.

Hagerinan, basalt in Snake River Canyon 

near, plate showing waterworn mass of................... 146

Snake River Canyon near, plate showing ............................. 24

water tunnels near.................. 164-165

Hagerman Bend, land at, cultivation of.. 30 

land at, irrigation of.................. 164

Hayden survey, reference to work of.... 46

Healthfulness of the region............... 19

Heron, I. A., water piped by.............. 164

Highways of the region................... 33-34

Hillebraiid, W. P., analysis of lava by.... 87

analysis of soil by ..................... 137

Hot Spring, artesian wells near, features

of--.....-.-.---.-------------. 174-175

hot springs near, irrigation from .--. 167 

Hot Spring Creek, springs in canyon of,

occurrence and features of... .167 

Ho we, well drilled at, unsuccessful -___.. 178 

Howell, recent stream erosion near, plate

showing. ---.-.--............... 146

Humid regions, springs in, occurrence of. 155 

Hydrography of the region............... 25-28

I.

Ice wells, occurrence of................... 81

Idaho, population of...................... 33

population of towns in................. 32

southern, map showing approximate

extent of Snake River lava in. 13 

State engineer of, reference to report

by......-.....-.-.-..----- . - 159

Idaho Falls, height of..................... 28

Idaho Falls, population of................. 32

Idaho formation. occurrenc9 and character of ........................ 51-50

Idaho Hydraulic and Pneumatic Irrigation Company, plan for raising water to the plain proposed 

by-....--.........-.....- 163-164

Irrigation from surface streams, consideration of--...--..-----.... 159-162

Irrigation and agriculture in the region. .......................... 28-31

J.

Jones, Dan, tunnel on ranch of, features

of ............................ 164-165

Jones Brothers, artesian wells on ranch

of, features of ................. 176

Judd, J. W., reference to work by....... 110

K. 

Kiniama, well at, depth and temperature

of .............................. 173

King, F. H., reference to paper by....... 148

Kinghill Creek, Snake River lava in,

plate showing remnant of .... 60

Page. 

Kinghill lava stream, features of ........ 70

Kuna Butte, features of ................ 109-110

plate showing ......................... 110

L. 

Lacustral conditions, siinimary of ....... 57-58

Landslides, occurrence of................ _ 126

Lapilli, characteristics of................. 74-75

stratified, plate.showing ._......._ _.__ 1(38

Lava, balls of, occurrence of.............. 114

cakes of, from Cinder Buttes, characteristics of..................... 79-80

caverns in, occurrence and features

of.............................. 98-101

Cinder Butto, analysis of.............. 87

chemical composition of .......... 87-89

cone of, near Arco, plate showing.... ] 12

cones of, occurrence and features of.. 112 

expansion of, by steam on entering

water, plate showing.......... 92

flows of, relative age of............. 105-107

surface drainage influenced by. 104-105 

terminating on a plain, character

of margins of.................. .102

resting on undisturbed lake beds,

plate showing. ................ 118

sheets of, changes produced in, after

cooling....................... 118-130

depressions in surfaces of, occiirreuce of.......... ......... 101-102

disintegration and decay of .._. 122-123 

margins of, character of........ 102-105

open fissures and faults in ...... 118-122

stream cutting of-...... ...... 123-126

thicknesses of, irregularities in. 117-118 

underlying the region, number

and thickness of............. 112-113

streams of, from Cinder Buttes, features of ........................ 82-87

streams of, that entered water, occurrence and features of .... 15,113-117

pillow-like folds in, plate showing. 114 

section of.......................... 116

spindle-like roll of lava from, section of ......................... 114

terminating at the mountains, character of margins of.......... 102-105

Lava Creek, lava flows in region drained

by..--.......--..--.---.... 68-69

Lee's ranch, well drilled at, unsuccessful. 178 

Lewis artesian basin, features of.--...- 178-180 

Lime deposits, manner of formation of.. 142 

occurrence and character of. 141-145 

Limestone, occurrence of................. 15,46

Lindgren, Waldemar, cited-... ...... 42,50,61

quoted on lacustral deposits in Snake

River Canyon.................. 51

quoted on lava flows .................. 71

quoted on sources of Snake River

lava..-......-.....-.-..-- 66

study of the region by, reference to.. 14 

survey of the region by ............... '38-39

terrane named "Boise granite" by,

extent and features of........ 39

Little Canyon, origin and features of 127-128 

plate showing......................... 126

Snake River Canyon near mouth of,

plate showing north wall of.. 64
190 INDEX.

Page. 

Little Canyon, spring near moiith of. featuresof ........-.----.--------. 163

springs in, source of -....---..-.-..-.- 165

Little Canyon Creek, featuressof......... 69,70

Little Canyon lava stream, features of .. 69-70 

Little Lost River, features of ............ 130

well drilled on, unsuccessful.......... 178

Little Valley, artesian wells in, features

of....---...... --- ----.-.------ 175-176

fossils obtained in..................... 56

hot spring near head of, features of.. 169 

Little Wood River, deflection of.......... 133

Long Tom Creek, quartzite in hills at

head of......................... 45

Lost River country, mountain ranges in,

character of._-...-...._..-__--. 47

resemblance of southeastern Idaho to. 46 

Lost rivers, occurrence and features of. 130-133 

Lucas, F. A., determination of fossils by. 56

M.

McMullen ranch, artesian well on, features of ..... '. .................. 177

Malade River, features of ...... 127-128,132-133

Mammoth Cave, reference to..-__..-.--__ 152 

Market Lake Craters, features of... 37,108-109 

lapilli in, stratified, plate showing ... 108 

lava near, plate showing pressure

ridge in........................ 94

plate showing ......................... 108

Martin lava stream, features of .......... 68-69

Medicine Lodge Creek, features of....... 130

Mesozoic rocks in southeastern Idaho, occurrence of.................... 49

Mining in the region...................... 32

Middle Butte, location and features of... 34-38 

elevation of............................ 34

slopes of,character o"................. 36

vegetation on........................... 35-36

Minidoka, well at, depth and temperature

of.-.....---...---..-.--..--.-... 173

Mora, well at, depth of.................... 173

Mountain Home, Canyon Creek Canyon

near, plate showing wall of... 64 

faults north of......................... 120

features of -----.-....-----.----..--.... 172

flowing water at, possibility of obtaining ........................... 182-183

hot springs at, suggestions relative to

development of................ 170

population of ......................... 32,172

springs near, features of........ 168-169,171

wells of, character of ................. 172

Mountains in southeastern Idaho, general trend of.--.--....._.-_.... 46-47

Mountains surrounding the region, rocks

of............................... 39

Mountains visible from the region, character of ........................ 17

Mount Bennett rhyolite, character of.... 42-43

Mud Lake, features of --..--.-.-....--..._ 130

N.

Nampa, well at, depth and temperature of 173 

Newell, F.H.,field workunder direction of 13 

North Fork of Snake River, features of. 134 

Notched Butte, cavern on side of, features

of .----...-...-................. 99

 0.

Pago.

Oregon Short Line Railroad, wells along,

features of..................... 173

wells along, temperature of ........ 153-154

O winza, well at, depth and temperature of 17 

Owyhee,wellat, depthaud temperature of 173 

Owyhee Mountains, granite in, occurrence of........................ 42

lava in, occurrence of.................. 71

P.

Pahoehoe, Dana's description of.'......... . 90

Pahoehoe near Cinder Buttes, occurrence

and characteristics of......... 91-92

Paleozoic rocks in central and southeastern Idaho, occurrence of...... 49

Payette formation, occurrence and character of ........................ 50-51

Payette Lake, formation and filling of... 15 

Payette River, irrigation from........... 160

Peale, A. C., reference to report by ..... 46

Pence, A. H., artesian well on property

of, features of . --....-......--. 175

Physiography and geology of the region. 13-146 

Pocatello, population of................... i>2

Poison Spring, location of .------.......-. 169

Population of Idaho....................... 33

Populations of towns in Idaho............ 32

Portneuf River, upgrading of ............ 133

Precipitation, mean annual............... 18

run-off influenced by rate of.......... 147

Pre-Tertiary rocks, occurrence and character of......................... 33-49

Quartzite,occurrence and formation of:. 15,45 

R.

Railroads in the region.................... 33

Rainfall. See Precipitation. 

Rattlesnake Creek, Snake River Canyon

belowmouthof,plateshowing. 24

springs near mouth of, occurrence of. 1(50 

Residual soils, occurrence of -.-.-......-.. 141

Rhyolite, occurrenceand character of. 15,42-45 

Roads of the region........................ 3.3-34

Roberson, W. N., artesian well on ranch

of, features of................ 174-175

Rock Creek, rocks in hills drained by,

character of................... 44

well at, features of__._._.............. 177

wells and springs on................... 44

Rock Creek hills, artesian wells in, features of---------------------- 17(i-.l77

Rocks, porosity of,run-off influenced by. 147 

Rocks of the region, character of......... 15-17

disintegration and decay of......... 122-123

Ross, D. W., reference to report by...... 159

Run-off and underflow, conditions influencing relations of ......... 147-148

Russell, I.C., reference to papers by. 156,158,168

S.

Sagebrush (Artemisia tridentata), occurrence of ---...-------..-.-----.- 22

St. Anthony, population of ............... 32

St. John, Orestes, reference to report by. 46
INDEX. 191

Page. 

Salmon Falls, height of ......_............ ' 28

Salmon .River, fissure springs near month

of, occurrence and features of. 169 

warm fissure spring in canyon of, occurrence of _.....--.._.--...... 169

springs near mouth of .............. .102-103

Sand dunes, occurrence and features

of............................. 140-141

Sandhill Mountains, partial bxirial of, by

drifting sand .................. 140

Sand Spring, features of.................. 163

soitrce of............................... 165

Scenery in southern Idaho, attractiveness of ......................... 19-21

Scoria from Cinder Buttes, characteristics of .......................... 75

Scrope, G. P., reference to publication by. 84 

Sedimentary beds, economic importance

of.....:........,............-... 58

(Tertiary), possible eastward extension of ......................... 59

Sheep raising, destruction attributable to 140 

Shell Mountain, basalt exposed at, charactor of..........-.--...-.-.... 55

fresh-water shells collected at........ 5(i

Shoshone, well drilled at, unsuccessful. - 177 

Shoshone artesian slope,features of.... 180-181

Shoshone Falls, domes and ridges near.. 96 

features of............................. 1.25

height of............................... 28

plate showing.......................... 28

rocks at, character of................. 43-44

Silurian rocks east of Snake River, occurrence of --....---------....--... 46

Slater Creek, well drilled on, imsuccessf ul 189 

Slope, artesian, section of... I............. 158

run-off influenced by.................. 147

Snake River, area on each side of, character of ........................ 16

canyon of, character of ............... 54

course, character, and discharge.of. _. 25-26 

gold along, occurrence of............. 32

gravel flood plain of, character of.... 30

lowering of bed of, results of....... 123-124

North Fork of, features of............ 134

rocks forming prominent mountains

east of, character of........... 46

Shoshone Falls, plate showing........ 28

South Fork of, upgrading of........ 133-134

Twin Falls of, plate showing.......... 124

water power available along.......... 28

waters of, above American Falls, use

of............................. 159-160

Snake River and tributaries, water supply from._-_._.-.._..--._...--. 159 

Snake River Basin, early geological history of .......................... 48-49

Snake River Canyon, Blue Lake alcove, 

looking south into, plate showing ............................. 128

breccia in walls of, cnaracteristics of. 115 

domes and ridges on border of, occurrence of --.-.-.-...----------..- 96

features of ........................ 124,125,126

lava exposed in, thickness of.......... 60

lava (columnar) in, plate showing

block of........................ till

Page. 

Snake River Canyon, lava balls in walls

of, occurrence of ............. . 114

lava sheets in, irregularities in thickness of......................... .1.17

Little Canyon, looking south into,

plate showing.................. 126

north wall of, height of............... 52

plate showing...................... 52

plate showing north Vail of, near

mouth of Little Canyon....... 64

plate showing view of, bslow mouth

of Rattlesnake Creek.......... 24

plate showing view of, near Hagerman............................ 24

plate showing water-worn mass of

basalt in, near Hagerman..... 146

rocks in, character of................. 43

sand driftsinand near................ 140

section of, below Glenns Ferry....... 55

sections of, near mouth of Bruncau

River .......................... 53,54

section of wall of, below mouth of Canyon Creek ..................... 52,53

south wall of, plate showing.......... 54

springs in, section showing mode of

origin of ....................... 150

springs of, extent of................. 162-163

springs from northern wall of, features of....................... 26,165

The Thousand Springs of, plate showing ...................... 1 ...... 26

walls of, features of................... 126

source of water pouring from.... 28

Snake River lava, area covered by....... 60

features of............................ 95-96

lava caves in, occurrence of.......... 99

map showing approximate extent of,

in southern Idaho ............. 13

occurrence, extent and character of.. 59-66 

relation of, to Columbia River lava... 50-61 

remnant of, on Kinghill Creek, plate

showing........................ 60

plate showing pressure ridges in, near

Big Butte...................... 94

plate showing pressure ridge in, near

Market Lake Craters ......... 94

source of............................... 63-66

Snake River Valley, character of ........ 55-56

Snowfall in the region .................... 18

Soda Springs, source of heat of........... 153

Soils, analyses of ........................ 136,137

aeolian, analyses and character of.. 136-139 

alkaline, indications of.... ............ 141

alluvial, deposition of ............... 135-136

erosion of, prevention of.............. 146

recent occurrence of ............ 145-146

residual, occurrence of................ 141

water-laid, occurrence of ............. 140

Soils of the region, character of.......... 24-25

kinds and features of ............... 135-141

summary of............................ 141

South Fork of Snake River, upgrading

of............................. 133,134

Springs, character and occurrence of, in

Snake River Valley ... 26-28,162-171 

development of........................ 156

formation of canyons by............ 127-130
192 INDEX.

Page 

Springs, kinds and characters of ....... 148-152

land watered from .................... 30

relation to climate, topography, and

geology of.................... 154-156

similarity between wells and......... 154

sources of supply of................... 132

temperature of, conditions regulating ........................... 158-153

Springs,canyon, fldw of, suggestions relative to increasing .......... 167-1(58

occurrence and features of ..... 150-151,

162-168

section showing conditions favoring occurrence of.............. 15(3

temperature of.................. 153,154

Springs, cavern, occurrence and features

of....--...--.-.--.....-----..-. 152

temperature of.................:.. 153

Springs, fissure, development of, suggestions relative to.............. 169-171

flow of, suggestions relative to

increasing ..................... 168

occurrence and features of..... 151-152,

168-17.1. 

temperature of.................... 153

Springs, hillside, occurrence and features

of.-......-.....-....-..------. 149-150

section showing relation to watertable of......................... 149

temperature of.................. 152-153

Springs, hot, source of heat of ............ 153

Steptoes (Big and East buttes), examples

of....-------.-...........-...... 34

Stock raising in the region........ 1....... 31-32

Streams, occurrence and features of..... 25-26

upgrading of.......................... 133-184

Subaerial deposits, chemically formed.

occurrence and character of. 141-145 

Subterranean waters, distribution of .... 148

T.

Temperature of the region, range in..... 17-18

Temperature of springs, conditions regulating ........................ 152-154

Tertiary beds in mountains near Boise,

occurrence of .................. 49

Tertiary and Recent lacustral formations,

occurrence and character of. - 50-59 

Tertiary sedimentary beds, possible eastward extension of............. 59

Thousand Springs (The), featuresof. 26-27,163 

plate showing.......................... 26

source of-....-----..--------...-------- 165

temperature of...-.....-..-.....--.--.- 163

use of................................... 162

volume of, estimate of................. 27

To'pographic features of southern Idaho,

summary of............---...-- 17

Page. 

Topography, relation of springs to..... 154-156

Topography of the region, features of ... 14-17 

Towns of the region, population and featuresof......................... 32-33

Tree-covered lava streams, occurrence of. 1.07 

Turner, Scott, observations made by -... 1.73 

Twin Falls, heightof...................... 28

plate showing..-....................... 124

U.

Uhrlaub, N., information furnished by... 127

Underflow and run-off, conditions influencing relations of .......... 147-148

V.

Vegetation of the region.......--..,._.... 22-23

Vesicles in bombs, gradation in size of,

theories relative to cause of... 77-78 

Volcanic cones in the region, occurrence

of............................... 37-38

Volcanic eruptions, theories of cause of.. 89-90 

Volcanoes among the mountains, consideration of ...................... 66-71

Volcanoes in the region, location and featuresof........................ 71-134

W.

Wapi, well at, depth of.................... 173

Water, artesian, possibility of obtaining. 58-59 

Water beneath eastern portion of the

region, probability of presence

of..--.-...--.-..-.-...--...-.. 183-184 

Water power in the region -....-..-..-... 28 

Water resources of the region.-....-.-. 147-184 

Water supply of the region, conclusions

relative to ..-.......-.....--. 184-185

Water table, section showing relation of

hillside springs to............. 149

Waterfalls in the region, occurrence and

featuresof............-..,-- 123-126

Wedge, artesian, section of............... 157

Wells, artesian. (.See Artesian wells.)

classification of........................ 17.1

deep, homology to canyon and cave

springs of...................... 154

ordinary supply of.................... 154

rock, occurrence and features of... 172-174 

similarity of springs to ............... 154

surface, occurrence and features of.. 172

temperature gradient indicated by. 173-174

Whirlwinds, occurrence of ............... 19

Whitson, B., artesian wells on ranch of,

featuresof----.-----------.-- 175

Wild Horse well, location and features

of.. .......................... 177

Winds, character of....................... 18-19

o