57TH CoNGREss, } HOUSE OF REPRESENTATIVES. J DocUl\iENT 

1st Session. t No. 53. 

DEPARTMENT OF THE INTERIOR 

WATER-SUPPLY 

AND 

IRRIGATION PAPERS 

OF THE 

UNITED STATES GEOLOGICAL SURVEY 

No. 53 

GEOLOGY AND WATER RESOURCES OF NEZ PERCE 

COUNTY, IDAHO, PART I.-RussELL 

WASHINGTON 

GOVERNMENT PRINTING OFFICE 

1901 

UNITED STATES GEOLOGICAL SURVEY 

CHARLES D. WALCOTT, DIRECTOR 

GEOLOGY AND WATER RESOURCES OF 

NEZ PERCE COUNTY, IDAHO 

PART I 

BY ISRAEL COOK RUSSELL 

WASHINGTON 

GOVERNMENT PRINTING OFFICE 

1901 

CONTENTS. 

Page. 

Letter of transmittal ••••••...... ___ . ____ .. _________________________ •.. _ _ _ _ 9 

Location and general character of region _ . __________________________ . _ _ _ _ _ _ 11 

Geology •.••••. __ . ________________ ... ______________________ . _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 15 

Pre-Tertiary terranes _____ . ____ . ___ • _______ .. ___ ... _. _ .. _ .. ____ . _ ...• _ 16 

Bitterroot Mountains __ .. __ ~ __ ... _ .. __________ ... ________ . _______ . _ 16 

Island-like areas in a sea of lava (steptoes) ______ • __ .. ________ . ____ . 19 

Formations beneath the Columbia River lava __ ... _ . _. _ _ _ _ _ _ _ _ _ _ _ _ _ 23 

Columbia River lava. __ .. _____________________ ._._. ___ ... ___ .. ____ ... _ 28 

History __ . __ . __ . _ . ___ . __ . ________________________ ·- _____________ • _ 28 

Sheets of volcanic dust. _________ . ___ . _ .. ___ .. _ ... ___ . _. ____ . ____ . _ 32 

Deposits of lapilli __________________ . _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 34 

Sedimentary beds __________ . __ . _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 35 

Summary ___ . _ .. __ .. _ • ___ . _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 40 

Soils. _____ . ___ ... _____ .. __ . _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 42 

Residual soils . _________ . _____________________________ ... _ _ _ _ _ _ _ _ _ 42 

Transported soils ________________ . _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 48 

Summary ___________________________________ .____________________ 51 

Physiography ________ .. ___________________________ . _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 51 

Relation of surface relief to geologic structure and climate __ ... _ _ _ _ _ _ _ _ _ _ · 51 

Original lava plateau. _______________________ ._________________________ 52 

Leading features in the relief due to movements in the earth's crust _ _ _ _ _ 54 

Uniontown Plateau._. _________ .__________________________________ 55 

Clarkston and Lewiston plateaus_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 57 

Blue Hills __________ .. _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 59 

Craig Mountain ________ . _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 59 

Camas and Kamiah prairies _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 60 

Summary ____ . _ . _______ •... _ .. _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 61 

Leading features in the relief due to erosion_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 61 

Canyons of Snake River ______ :.__________________________________ 62 

Canyon of Grande Ronde River ________________ . _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 66 

Canyon of Salmon River .• _ ••.. _. _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 67 

Canyons of Clearwater River_ •• ___ ... _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 69 

Relation of the streams to geologic structure_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 70 

Stream terraces _____ .. ____ . ____ .. ______________________ .- _ _ _ _ _ _ _ _ _ _ _ _ _ 72 

Landslide topography ___ . _ .. _. _______ . _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 75 

Lake W aha __ .. __ . _______________________________________ . ____ · ___ .. _ _ 79 

Topography of the level plateaus _____________________ .. _ ... __ • _ _ _ _ _ _ _ _ 81 

Solution basins._._. _____ . ____ ..• ___________ . _________ . _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 83 

Torrent-built levees. __________________________________________ ._______ 83 

Index, note concerning ..• _____________________ .. _ ..•• _ •.•...• __ •. _ • __ . _ _ _ 85 

5 

ILLUSTRATIONS. 

PLATE I. Map showing position of Nez Perce region _______________________ _ 

II. Map of Nez Perce region, showing Columbia River lava and pre- Tertiary terranes ________________________________________ . ____ _ 

III. A, View illustrating mature topography in the Bitterroot Mountains; 

B, Camas Prairie, with Kamiah Buttes in the distance __________ _ 

IV.- Canyon of Snake River near Waha ________ ' _________ ------ _______ _ 

V. A, Southern slope of Cottonwood Butte; B, Columbia River lava in 

Salmon River Canyon ________________________________________ _ 

VI. A, Sandspit in North Fork of Clearwater River; B, Canyon of Snake 

River from Craig Mountain ___________________________________ _ 

VII. Lewiston Plateau from near W aha ______________________________ _ 

VIII. View showing details in wall of Snake River Canyon " ____ . _______ _ 

IX. A, Valley of South Fork of Clearwater River near Kamiah; B, Salmon 

River Canyon from Cottonwood Butte _________________________ _ 

X. View showing details in wall of Salmon River Canyon. _______ . ___ _ 

Fw. 1. Section through Uniontown Plateau, Clearwater escarpment, and 

Lewiston Plateau _______________________________________________ _ 

2. Section through Lewiston and Clarkston plateaus_. ______ ._. __ . ____ ._ 

3. Section through I .. ewiston Plateau, Craig Mountain, and Camas Prairie_ 

4. Sections of cliffs with landslides._. _____________ • ___ ._ .. _ ... _______ . 

7 

Page. 

12 

16 

18 

30 

32 

40 

58 

62 

68 

70 

56 

58 

60 

78 

LETTER OF TRANSMITTAL. 

DEPARTMENT OF THE INTERIOR, 

UNITED STATES GEOLOGICAL SURVEY, 

DIVISION OF HYDROGRAPHY, 

Washington, IJ. 0., Aprill~, 1901. 

SIR: I have the honor to transmit herewith a manuscript by Prof. 

Israel C. Russell, of Ann Arbor, Michigan, relating to the geology 

and water resources of Nez Perce County, Idaho, for publication in 

the series of Water-Supply and Irrigation Papers. This is the result 

of the examination conducted during the field season of 1900. The 

facts obtained ·have considerable value, not only in the development 

of water, but also in obtaining a knowledge of the other resources of 

this important area. The details and descriptions have increased the 

length of the manuscript to such an extent that, in order to conform 

with the terms of the law restricting the pamphlets to 100 pages, it is 

necessary to divide the material into two portions, the first or preliminary part relating to the geology and physiography of the area, 

and the second part taking up the water supply and other economic 

features. 

Very respectfully, 

Hon. CHARLES D. WALCOTT, 

F. H. NEWELL, 

IIydrographm· ·in Charge. 

Director United States Geological Survey. 

9 

GEOLOGY AND WATER RESOURCES OF NEZ PERCE 

COUNTY, IDAHO. 

PART I. 

By IsRAEL C. RusSELL. 

LOCATION AND GENERAL CHARACTER OF REGION. 

An investigation of the geology of Nez Perce County, Idaho~ was 

made by the writer during the summer of 1900, with special reference 

to the possibilities of obtaining artesian water. Field work was carried on from July 4 to September 11, and examination was made of as 

much of the county and adjacent country as time permitted. In the 

absence of a satisfactory topographic map, however' only what is understood as reconnaissance work could be done, and without such· a map 

it is also difficult to mak~ a detailed and accurate presentation of the 

facts observed. For these reasons this paper should be considered as 

simply a report of progress, and not a complete and detailed geologic 

survey of the region visited and studied. 

Nez Perce County, as i~ shown on Pl. I, is situated in western Idaho. 

It is bordered on the west by portions of Washington and Oregon, and 

the dividing line between these two States if prolonged eastward 

would cross the county about 10 miles from its southern boundary, 

As will be seen on the accompanying geologic sketch map (Pl. II), the 

western border of the county, to within about 4 miles of Lewiston, is 

marked by the middle line of Snake River. The other portions of the 

boundary need not be described, as they ~re indicated on the map 

referred to, but it will be convenient to bear in mind their relations 

to certain conspicuous topographic features. A part of the southern 

boundary is formed by Salmon River, and another part by Lawyers 

Creek, while the eastern boundary is determined by Clearwater River 

and the South Fork of the same stream. Each of the streams just mentioned, and also Snake River throughout the portion of its course 

shown on Pl. II, flows in a canyon 2,000 or more feet deep, so that 

11 
12 GEOLOGY, ETO., OF NEZ PEROE 00., IDAHO.-PART I. [No.53. 

throughout much of its course the boundary of the county coincides 

with strongly pronounced features in the relief of the lana. 

The approximate area of the county is 1,335 square miles-somewhat 

larger than that of the State of Rhode Island. It is, however, one of 

the smaller of the twenty~one counties into which Idaho is divided. 

The main portion of the county lies between latitude 46° and 46° 35' 

N., and between longitude 116° and 117° W. The county seat is Lewis 

ton, which has a population of 2,425 and is situated on its western 

border, at the junction of Clearwater River with Snake River. Lewiston is connected with Clarkston, Washington, on the west side of Snake 

River, by a fine steel cantilever bridge. These two towns, frequently 

designated Lewiston-Clarkstpn, have a joint population of 4,000. 

There are also many villages and hamlets scattered throughout the 

county and over the adjacent country, more especially to the east and 

north, and isolated farmhouses and settlers' cabins are numerous. The 

population of the county is 13,748. Agriculture is the chief industry. 

An examination of any recent map of the New Northwest will show 

that branches of the Northern Pacific Railroad and of the tracks of 

the Oregon Railway and Navigation Company extend into Nez Perce 

County and the country adjacent, and terminate without making 

through connections. These branches of two great trunk railroad systems suggest at once that the newly settled region which they invade 

has something that invites capital, and it will be found that the attraction which has drawn the steel bands through profound canyons, across 

broad plateaus, and over rugged mountains is mainly wheat. No doubt 

it will be a surprise to many of my readers to learn that the eastern 

portions of Washington and Oregon, with an adjacent strip of country 

in Idaho, produce annually from 50,000,000 to 60,000,000 bushels of 

wheat, as well as considerable quantities of other grain. This great 

and rapidly growing industry is based on the remarkable fertility of 

the soil and the favorable climatic conditions. The fine, dark, rich soil, 

as will be shown later, has resulted from the disintegration and decay 

of certain widely spread volcanic rocks, and is of almost unrivaled fertility. The climate, although inmanyrespectsfavorable to agricultural 

pursuits, is not all that might be desired. The seasons are two in number, winter and summer; or, to use more descriptive terms, a humid 

season and a dry season. The winters, more particularly in the -valleys 

and canyons and on the lower plateaus, are wet. Snow seldom lies on 

the ground for more than a few days at a time, but damp, chilly weather 

is prevalent, and practically all the rain of the year falls during that 

time. It is stated that the only ''zero weather" known at Lewiston 

within the last ten years or longer occurred in February, 1899, when 

the temperature during one night :fell to 7t0 below zero; the next cold~ 

est period was in January, 1899, when the thermometer registered 12° 

above zero. On the higher plateaus and mountains, or, in general, at 
U.S.GEOLOGICAL SURVEY. WATER-SUPPLY PAPER N~ 53 PL. I 

~L\P SfiO\'\' lNG POSI'l'ION OF NE7. PERCE RJ~GION 

S cal e 

~~=-""~=26"'=-c.lf.J'==""~~"--"""'""'""'======~0 MILR~ 

.JULJU5 81(N 8 CO. LITH N '( 
RUSSELL.] LOCATION AND GENERAL CHARACTER OF REGION. 13 

an elevation of 2,000 or more feet above Lewiston, equivalent to an 

elevation of 3,000 feet above the sea, the climate throughout the year 

is cooler and more humid than at lower altitudes, and in winter the 

cold is frequently severe and the snow deep. In the Bitterroot Moun-

. tains, to the east of Nez Perce County, the marks made on the trees 

in winter, known as" snow-shoe blazes," are from 15 to 20 feet above 

the ground, and show that the snow accumulates to great depths. 

These mountains are densely forest covered, are uninhabited, and 

judging from the nature of the vegetation the climate is cold and the 

precipitation abundant. Between the two extremes in elevation, 

namely, the canyons and lower plate:;~.us and the truly mountainous 

portions of the country, there are certain broad plateaus, such as the 

on(3 to the north of Clearwater River, termed in this paper the Uniontown Plateau, and the Camas and Kamiah prairies, which have surface 

elevations of about 3,000 feet and are intermediate in climatic conditions between the extremes just referred to. The winters, although 

colder than at lower elevations, are not severe; snow remains on the 

ground several weeks, but seldom affords good sleighing, and the rainfall is frequently heavy. During the long, clear summers the days are 

hot, but the nights are always cool. 

The most populous portions· of the region are thus without the cold, 

clear winter weather, with the land snow covered, which forms so 

characteristic a feature of the States in the same latitude on the eastern 

side of the continent. On the contrary, the open winters of western 

Idaho and of adjacent portions of Washington and Oregon are characterized by frequent changes from frost to thaw. The air is frequently 

damp and chilly, and much of the time the roads are all but impassable, 

on account of the deep mud. The summers are long, and in the can-

)'"Ons and on the lower plateaus the heat at times is intense, the thermometer frequently registering 100° F. or more in the shade. Owing 

to the dryness of the air, however, this extreme heat is less oppressive 

than a much lower temperature would be in more humid lands. During the summer hot winds, the equivalent of the warm chinook winds 

of winter, also occasionally occur, which, particularly on the lower 

plateaus, sometimes wither the green grain in a few hours and cause 

great losses. During the heat of the summer the soil is dry, frequently parched, and the dust on the roads lies several inches deep, 

being often carried in the air in dense clouds. 

The rainfall at Lewiston, situated in the lowest and d:--iest portiOn 

of the Nez Perce region, is usually from 14 to 16 inches a year. Of 

this meager amount the larger portion comes between the first of 

November and the end of March. With increase in elevation there is 

an increase in precipitation, but in the absence of definite observations 

the annual rainfall on the higher plateaus can only be judged from the 

nature of the vegetation and the success with which various crops are 
14 GEOLOGY, ETC., OF NEZ PERCE CO., IDAHO.-PART I. [No.53. 

cultivated. On the Uniontown Plateau, where the elevation is about 

3,000 feet, the annual precipitation is said to be in the neighborhood 

of 25 inches. In its original state this broad plateau wa~ without 

trees, but was covered with a luxuriant growth of grasses and flowering annuals, which made it a beautiful prairie. The broad Camas and 

Kamiah prairies also were treeless, and may be considered to have 

about the same rainfall and other climatic features that characterize 

the Uniontown Plateau. At higher elevations, beginning, in general, 

at about 3,500 feet, forests appear, and give evidence of more abundant 

precipitation. 

In the lower and drier portions of the county, particularly in the 

canyons of Snake and Clearwater rivers and on the adjacent plateaus, irrigation is necessary for all forms of agriculture except 

where the land is so low that it is subirrigated naturally from the 

streams. On the plateaus, 1,500 or more feet above the sea, wheat, 

oats, barley, flax, etc., are grown without water other than that 

absorbed and retained by the fine porous soil, and yield surprisingly 

abundant returns; but orchards, except under unusually favorable 

local conditions, require irrigation. On the higher plateaus and in 

the mountains, although the rainfall is sufficient for growing fruit, the 

temperature conditions are unfavorable except for berries and, possibly, apples. In the valleys and canyons, particularly those of Snake, 

Salmon, and Clearwater rivers, where suitable land can be had and 

where water for irrigation is also available, peaches, pears, plums, 

prunes, cherries, grapes, berries, and garden vegetables, all of excellent 

quality, are produced in great abundance. 

With reference to native vegetation, the Nez Perce region may be 

divided into two portions, namely, prairies and forests. Before being 

plowed, the plateaus at .elevations of 3,500 feet or less were clothed 

with bunch grass and a great variety of flowering annuals. With these 

natural meadows are to be classed al~o the precipitous border of most 

of the canyons, which are, for the most part, still in their natural state, 

except that they have been utilized for stock ranges and are still clothed 

with bunch grass. In early spring their rugged slopes are many tints 

of green, but as the heat of summer increases the grasses wither and 

become yellow. In late summer the entire landscape, from any commanding eminence rising above the plateaus, is various shades of yellow, 

. for then the grain fields have changed to nearly the same color as the 

grass-covered canyon walls, the only exception to the prevailing oldgold color being furnished by the rich brown of the crumbling rocks 

in the canyon walls, the less prevalent black of the but slightly weathered basaltic lava, and rectangular areas of deep black, as it appears by 

contrast, which mark the locations of fallow lands among the grain 

fields. 

While Nez Perce County and much of the adjacent country is highly 
RUSSELL.] GEOLOGY. 15 

favored in many ways by soil and climatic conditions, there is in general a scarcity of water available for town supply, irrigation, and 

even for household purposes. While the streams are numerous, and 

several of them are of large size, they are, for the most part, in deep 

canyons, and are practically unavailable for irrigation or other economic uses. In certain instances, however, the water of streams has 

been diverted and is being used for irrigation, but the areas thus 

brought under cultivation are small in comparison with the total extent 

of rich agricultural land which needs water at certain seasons. The 

further utilization of the stream is limited by the great cost of constructing storage reservoirs, dams, and ditches, and by the conflicting 

interests involved. For these reasons attention has been directed to 

possible subterranean sources of water supply, and a number of wells 

have been drilled, one of which yields a good surface flow. It was 

with the hope that if the geologic conditions were understood the 

present scant water supply might be increased, not only by obtaining 

artesian water but by incre:tsing the flow of springs, that the studies 

described in the following pages were undertaken. 

GEOLOGY. 

The rocks in the Nez Perce region form two sharply defined groups. 

The older .group consists of a large variety of rocks of both igneous 

and sedimentary origin, and includes also great areas of metamorphic 

rock the original nature of which has not in all cases b~en determined. 

The younger group consists principally of basalt, but includes layers 

of clay, sand, gravel, volcanic dust, and lapilli interbedded with it. 

The older group was greatly disturbed by folding and otherwise, and 

formed a land surface that was deeply denuded before the younger 

group, which in general has been but moderately deformed, was spread 

out upon it. Thus, geologically, the two groups are sharply defined. 

Their differences are also conspicuous from the viewpoint of the 

economist. The older group contains a variety of excellent building 

stones, in many places carries gold and ores of various metals, and when 

decomposed fonns usually a I!ght-colored soil, which iFi not fertile; 

while the younger group, furnishing only the black basalt and certain 

soft beds of loosely compacted volcanic dust which can be used for 

building purposes, is without native metals or ores, hut contains lignite which may prove of value, and on decomposing furnishes a deep, 

rich, dark soil of marvelous fertility. 

With reference to the possibilities of obtaining artesian water, only 

the younger group needs to be considered; and as the principal aim of 

the reconnaissance was to ascertain to what extent the geologic conditions favor an increase in the underground water supply, but little 

attention could be given, in the time available, to t4e study of the 

rocks of the older group. 
PRE-TERTIARY TERRANES. ~ 16 GEOLOGY, ETC., OF NEZ PERCE CO., IDAHO.-PART I. fNo. 53. 

The older rock group just referred to is considttred to be of preTertiary age, partly because of its lithologic similarity to known terranes of older date than the Tertiary, but principally because certain 

limestones found in it carry obscure fossils which seem to indicate a 

Mesozoic age, and because the Columbia River lava, which overlies portions of it unconformably, is known, fron1 the fossils contained in the 

sedimentary beds included in it, to have been outpoured during Tertiary time. 

Rocks of older date than the Columbia River lava are now exposed j 

at the surface. In some places these rocks were never covered by the "] 

lava, and in other places the lava beneath which they were formerly ··~ .

buried has been cut through or removed by stream erosion. The 

exposures of the former class, so far as the region shown in Pl. II is 

concerned, are in the foothills of the Bitterroot Mountains, and 

where Cottonwood Butte, Kamiah Buttes, and a few other island-like 

areas rise above the surface of the generally lava-covered country. 

The exposures of the older formations due to erosion occur where 

Snake, Salmon, and Clearwater rivers and some of their tributaries 

have cut through the lava and into the rocks beneath. 

BITTERROOT MOUNTAINS. 

Comparatively little information is available concerning the Bitterroot Mountains; but it is known that along their western border they 

are composed principally of gneiss and mica-schist, frequently rich in 

garnets, diorites, etc., with occasional porphyritic dikes and intrusions 

of rhyolite. The trend of the structural lines in the gneiss and schist 

and of the dikes is nearly north and south. About 20 miles east from 

the generalized western margin, as can be seen along the Lolo trail, a 

change occurs, and the great central portion of the mountains is seemingly composed throughout of a light-colored granite containing black . 

mica and frequently large crystals of both white and pink feldspar. 

This granite is the country rock over a great area, extending far to the 

north of the ]\rJiddle Fork of Clearwater River, and no doubt is a part 

of the extensive area of similar rock in the southern portion of the 

same mountains, mapped by W. Lindgren and shown by him to be 

intrusive and of post-Paleozoic age. 1 Lindgren makes the statement 

that this is the largest granite area in the United States, and gives 

a detailed description of the rock, accompanied by several chemical 

analyses. 

A view of the Bitterroot Mountains from any commanding summit 

near their western bo~der shows a multitude of peaks and sharp, serrate 

1The gold and silver veins of Silver City, De Lamar, and other mining districts in Idaho, by Waldemar L.ndgren: Twentieth Ann. Rept. U.S. Geol. Survey, Pt. III, pp. 79-85. 

·:; 
U.S.GE<. _, WATER -S UPPLY PAPER N9 53 Pl. II 

GEOLOGICAL SKETCH MAP OF NE7. PERCE REGION, ID.c\HO. r ___.______, ' Scale of mlles L___.1 0 r -4 ,. &. 10 lZ Z4 36 

Columbin.l{iver lnva ( 7'ert.iary) L901. 

.JUUUSBIENSC'.O.LFTH N.V 

'l'c1·1·ancs older tl'tan lh(· Coluntbin H.ivcv laYu .. 
RUSSELL.] PRE-TERTIARY TERRANES. 17 

crests rising to a general elevation of about 6,500 feet above the sea. 

(See Pl. III, A.) Between the elevations are deep canyons and valleys 

with flaring sides. The topography is characteristic of an old land surface, deeply denuded and now drained by a mature and well-developed 

system of waterways. Every view of the mountains impresses one 

with the vast amount of erosion that has occurred in the process of 

shaping the present peaks and removing the solid rocks which once 

occupied the valleys, and although this herculean task taxes the imagination to picture and understand, it is evidently small in comparison 

with the totaJ amount of denudation required to lay bare the granite, 

which at the time of its intrusion must have been covered to a depth of 

thousands of feet by rocks which were hardened by its heat. 

To the south of the Middle Fork of Clearwater River and in the 

west-central part of the Bitterroot Forest Reserve, is a range of prominent peaks termed The Crags, which rise from 3,000 to 4,000 feet above 

the general level of the rugged land surrounding them, and have 

patches of snow in their sheltered recesses late in the summer. Judging from their topography as seen at a distance, the depressions among 

the prominent peaks appear to have formerly been occupied by alpine 

glaciers. . At least one of the secondary peaks, Rocky Crest, situated 

about 15 miles west of Bald Mountain and crossed by the Lolo trail, also 

bears evidence of former glaciation. On its eastern and northeastern 

sides there are three well-defined amphitheaters in the walls and over 

the bottoms of which are. smoothed rock surfaces such as glaciers leave. 

These amphitheaters, eroded in the summit of a bold mountain, are 

about 500 feet deep, and on their lower margins open out into impressive stream-cut valleys. The glaciers which occupied them were in each 

instance about a mile in length and were isolated from one another. 

None of the ..adjacent mountains retain evidences of glaciation, although 

about 20 miles to the northeast of Rocky Crest there are prominent 

peaks which are similar in form to that mountain and which very likely 

once gave origin to small ice streams. This is the only evidence 

observed of the former presence of glaciers in the region represented 

on the map forming Pl. II, or over a large area to the east and west of · 

that region. Seven Devils and Powder River mountains·, from 40 to 

50 miles south of the southern boundary of Nez Perce County, were 

in plain view from several points visited during the reconnaissance, and, 

judging from the topography and the fact that late in summer they 

are whitened with lingering snowbanks, it is to be presumed that they 

were formerly occupied by glaciers. This meager evidence, taken in 

connection with observations made by Eldridge 1 and Lindgren 2 in 

south-central Idaho, shows that throughout central and southern Idaho 

1 A geological reconnaissance across Idaho, by Geo. H. Eldridge: Sixteenth Ann. Rept. U. S. Geol, 

Survey, Pt. II, pp. 223-224. 2 Twentieth Ann. Rept. U.s. Geol. Survey, Pt. III, pp.I00-101. 

IRR 53-01--2 
18 GEOLOGY, ETC., OF NEZ PERCE CO., IDAHO.-PART I. [No. 53. 

local glaciers only, of the alpine type, existed during the Glacial epoch, 

and that there was an absence of anything approaching a confluent ice 

sheet. The most instructive records made in this region during the 

time referred to are the stream-deposited gravels, some account of 

which will be given further on. 

The Mascot Hills, indicated in part in the northeastern corner of the 

map forming Pl. II, are a typical portion of the foothills of the Bitterroot Mountains, adjacent to the eastern margin of the Columbia River 

lava, and may be taken as representative of the conditions that exist 

for a long distance to both the north and the south o~ them. These 

hills rise boldly to a height of about 1,100 feet a hove the lava plain 

skirting them on all sides except to the eastward, and form a prominent headland on the margin of the sea of molten rock which, as will 

be described further on, encroached on the western slope of the Bitterroot Mountains. The rocks forming the Mascot Hills consist, in large 

part at least, of gneiss and mica-schist traversed by quartz veins. As 

is an almost invariable rule along the western border of the Bitterroot 

Mountains, the trend of the rock structure is about north and south, 

and what appears to be the bedding of the gneiss and the lamination of 

the schist stands nearly vertical. A marked feature in the topography 

of the hills is their subdued and generally rounded profiles, indicative of 

long exposure to the atmosphere. Sustaining this conclusion is the fact 

that the rocks are deeply disintegrated and decomposed. At the 

extremity of a tunnel at the Mascot mine, 150 feet from its entrance 

and about 125 feet below the surface, the rock is so soft and so completely shattered that it can be removed with a pick, and even the 

quartz can be crumbled between the fingers. Although the rocks are 

evidently weathered to a great depth, nowhere about the hills is there 

evidence of the advanced degree of rock decay which gives origin to 

red soil. The characteristic topography and deep weathering referred 

to are among the numerous evidences that the older group of rocks 

under consideration has formed a land surface for a great length of 

time, and was deeply eroded before the coming to the surface of the 

younger group of rocks of the region, namely, the Columbia River 

lava. 

From the summit of the Mascot Hills the relation of the Bitterroot 

Mountains to the vast lava plateau to the northward and westward is 

plainly revealed in the topography. To the north, and extending well 

to the northeast, there is a broad, level, densely :forest-covered region 

across which the North Fork of Clearwater River has cut a steepsided trench. Each branch of the river flows in a canyon, and what 

in distant views seems to be a level plateau is in reality deeply dissected. The summits of the canyon walls are formed of rim rocks of 

basalt, and the lower and usually bold slopes reveal the characteristic 

buttresses or terrace-like shoulders produced by the weathering of 

the more resistant rocks on which the basalt rests. 
U. S. GEOLOGICAL SURVEY WATER - SUPPLY PAPER NO. 53 PL. Ill 

A. B ITTERROOT MOUNTAINS, SHOWING MATURE TOPOG RAPHY. 

II. C~MAS PRA I RI E ; KAMIAH BUTTES IN THE DISTANC E. 
RUSSELL.] STEPTOES. 19 

The same plateau which has been deeply trenched by the North 

Fork and its numerous tributaries sweeps about the western base of 

the Mascot Hills and extends eastward up Orofino Creek nearly to 

Stuart. South of the canyon of Orofino Creek, with its precipitous 

walls of black basalt, the eye ranges over a long succession of rounded, 

forest-covered hills which project irregularly into a plateau to the 

westward, which is without forests and in summer is yellow, as far as 

the eye can reach, with grain fields. This vast cultivated tract, seemingly as level as a floor, is the Camas and Kamiah prairies. Although 

the plain is trenched by a number of narrow, steep-sided canyons, 

they are concealed from. view, and the plateau appears as it did when 

the last of the lava sheets of which it is composed was poured out as 

molten rock. Rising from the sea-like expanse of the former grasscovered and flower-strewn prairie, and forming conspicuous objects 

in the far-reaching landscapes, are two elevations, known as Cottonwood Butte and Kamiah Buttes, which are easily recognized, even at a 

distance of many miles, as mountain peaks which stood as islands 

· when the lava invasion occurred. A view from the summit of the 

Mascot Hills not only serves to reveal the general relation between 

the two groups of rocks of which the surrounding region is composed, 

but brings out the fact that although large portions of the plateau 

formed by the younger group still retain an essentially horizontal 

position, other portions have been tilted and otherwise deformed as 

well as trenched by stream channels. The evidence of extensive 

movements in the once horizontal lava sheets, however, will be discussed further on. 

ISLAND-LIKE AREAS IN A SEA OF LAVA (STEPTOES). 

The deep erosion of the pre-Tertiary land over which the Columbia 

River lava was poured out has already been referred to, but nowhere 

is it more clearly demonstrated than at Cottonwood Butte, which rises 

through the lava forming the Camas Prairie and in the adjacent portion of the canyon of Salmon River. This butte, which rises 1,100 or 

1,200 feet above the generally level basaltic plateaus surrounding it, 

is eomposed of a variety of rocks belonging to the older group 

referred to. At its summit and on its western side the rocks are 

compact and massive, and consist largely of old lavas or intrusions 

which have been altered and somewhat metamorphosed. In its eastern 

portion reddish slate appears, the cleavage planes of which are nearly 

vertical, also ancient lavas and lapilli-like deposits that have been consolidated and greatly altered, probably by heated waters and pressure. 1 

I Rock samples collected on Cottonwood Butte have been examined by Waldemar Lindgren, who, 

from their macroscopic characteristics, made the following provisional determinations: 

"A sample from west slope of the butte, metaandesite; from the top probably metabasalt or altered 

volcanic feldspar basalt; east slope, tuff or tuff-breccia, of old effusive rock, greenstone tuff, original 

character basaltic or andesitic; east end, clay slate (roofing slate), probably containing considerable 

admixed volcanic tuffaceous material." 
20 GEOLOGY, ETC., OF NEZ PERCE CO., IDAHO.-PART I. [No. 53. 

These old rocks show that they were deeply eroded before the coming 

of the Columbia River lava, but were left, by the removal of the material which formerly surrounded them, as isolated mountain peaks. 

The time required for this topographic transformation was certainly 

long, although it can not be measured by year·s, but some idea concerning it may be had by comparing the tasks accomplished by erosion 

before and after the eruption of the Columbia River lava. The peak 

has stood fully exposed to storms and sunshine since the lava flowed 

about it, but evidently it has suffered only a moderate amount of denudation, although the neighboring canyon of Salmon River has been 

excavated in the lava and the underlying and more resistant rocks to 

a depth of fully 3,500 feet. The work of the river in shaping its 

magnificent canyon is small in cmr..parison with the task which was 

accomplished previous to the coming of the lava in removing the 

material from about the hard rocks now forming the butte and leaving it a prominent mountain. The peak has suffered but little change 

during the time the adjacent canyon was being excavated, for the 

reason that it afforded but a small gathering ground for streams, and · 

also because its slaty layers are on edge and permit the rain water 

falling on them to percolate through, thus robbing it of the power to 

corrade. The rocks of Cottonwood Butte are not only resistant to 

mechanical wear, changes of temperature, etc., but, equally important, 

they do not yield readily to chemical influences such as the solvent 

action of percolating water. Even at the surface they are hard, and 

show visible evidences of weathering to a depth of only a few feet, 

in some cases only a few inches. The soil on the butte is thin, and the 

rock exposures are abundant. The weathering which has produced 

the deep rich soil of the basaltic plateau has made but little progress 

on the more resistant rocks forming the much more ancient butte. 

Even when account is taken of the steep slopes of the butte and the 

fact that rock waste would be removed n1uch more readily there than on 

the nearly :flat prairie surface surrounding it, the evidence still favors 

the view that the butte has been changed but little in height or contour 

since the Columbia River lava was poured out. A view of the southern slope of the butte is shown in Pl. V, A. It is of interest to note 

also that the soil on the butte is different from that on the surrounding 

basaltic plateau, and was derived from the rocks on which it rests. 

Reference will be made further on to this and other kindred facts 

which show that the soil of the basaltic plateau was derived from the 

decay of the basalt itself, and was not brought from a distance through 

the agency of the wind. 

As already stated, the slaty cleavage in the rocks forming Cottonwood Butte is nearly vertical. This has an important influence on the 

drainage, and accounts for the presence of the numerous springs of 

clear, cool water which occur there. One of these springs is in the 
RUSSELL.] STEPTOES. 21 

depression between the two summit peaks, and is supplied by the rain 

falling at higher levels. The northern side of the butte is forest cov-· 

ered, but its southern slope is mostly free from trees, and is clothed 

with bunch grass down to an horizon about 800 feet below the summit, 

where a pine forest begins which extends southward over the basaltic 

plateau. 

No more charming camping place and no more attractive location 

for a summer resort can be found in the Nez Perce region than is 

afforded by this isolated mountain peak, from the summit of which so 

much of the earth's history can be read as fron1 a printed page. From 

the summit of the butte one has not only a magnificent but a most 

instructive panorama spread out before him. In summer the air is 

nearly always cool and invigorating, and so clear that the distant 

mountains as well as the depths of the neighboring canyons seem 

near at hand, instead of many miles away. The clouds, which frequently form in vast, brilliantly illuminated banks about the higher 

peaks of the Bitterroot Mountains and drift over the broad wheat 

fields of the once monotonous prairie, mottling them with slowly moving shadows, serve to enhance the glory of the scene, and perhaps 

bring refreshing showers; violent storms are unknown in this region. 

In winter the ancient mountain peak is white with snow, and the cold 

frequently is intense. Looking southward from the topmost crag of 

the prominent butte on which the reader is invited to stand, in fancy, 

one sees at his feet the forest-covered plateau of Columbia River lava. 

Near at hand, rising from amid the dark pines, is the shining spire of 

a village church. A few miles beyond the dark plateau breaks off, as 

if an earthquake had shattered it, and one looks down into the purple 

depths of the vast chasm which Salmon River has eroded in order to 

carry its burden of sand and gravel to Snake River and then onward 

to the sea. The canyon is not a narrow gash in the rocks, with vertical walls, as the term may perhaps be thought to signify, but is a great 

excavation from 4 or 5 to 10 or more miles wide, with many serrate 

ridges and buttresses diversifying its precipitous sides. The upper 

portions of the canyon walls, sculptured into many forms by rain and 

rills, are of horizontal masses of dark rock (the edges of nearly level 

lava sheets), below which are more massive slopes showing where the 

underlying and more resistant rocks have been exposed. The course 

of. the canyon can be traced for 50 or more miles-from far away to 

the southeast to where it makes a sharp bend, seemingly at one's feet, 

and thence southwestward to its junction with the larger and still more 

magnificent excavation of a similar nature in the depths of which 

Snake River is hidden. To the south of the canyon of Salmon River 

is a broad forest-clothed remnant of the original plateau, formed of 

lava, which is bordered on its farther side by the canyon of Snake 

River, there fully 4,000 feet deep. The upper portion of the vast 

south wall of Snake River Canyon is in view from the butte, and 
2 2 G EO LOGY, ETC. , O"F NEZ PERCE CO. , IDAHO. -PART I. [No. 53. 

when brilliantly illuminated by the sun, one can, at a distance of 25 

iniles, trace the outlines of the castle-like and cathedral-like forms 

which give diversity to its somber scenery. The brink of the distant 

canyon is marked by a dark line of pines and firs, and, like the layer 

of basalt beneath it, is the edge of a widely extended sheet-the great 

coniferous forest of eastern Oregon. Still farther away, but frequently sharply outlined against the southern sky, rise the angular 

peaks of the Seven Devils and Powder River mountains, their summits 

far above timber line and here and there flecked with snow which 

gleams like burnished silver in the intense light of the unclouded summer sun. 

The view to the eastward embraces the broad undulating surface of 

the Camas and Kamiah prairies, which are checkered with rectangles 

of yellow grain fields and black fallow lands. The plain, several hundred square miles in area, is everywhere covered with a deep, rich 

soil, which has resulted from the decay of lava and is of wonderful 

fertility. Some suggestions are furnished of the deeply sunken. 

stream channels which dissect this young land, but for the most part 

they are lost to view, and the great expanse, with its mild undulations, recalls the rolling prairie or the great plateaus to the east of the 

Rocky Mountains. The Camas and Kamiah prairies are bordered on 

the east by an irregular coast line of hills, beyond which rise the 

forest-covered peaks and ridges, with flowing outlines, which compose 

the nearer portion of the Bitterroot Mountains. The view to the 

westward is less extensive than in other directions, but it presents 

other instructive features. The generally level surfaces of the Camas 

and Kamiah prairies rise gently along their western margin and merge 

by insensible gradations into the long eastern slope of Craig Mountain. 

With increase in elevation there comes a change in the vegetation, and 

the open prairie country, with its grain fields, its scattered farmhouses, and its villages, gives place to a dark forest of pines and firs. 

The rocks which underlie the- prairie have been bent upward and form 

a gently tilted plain, which breaks off abruptly on its farther (western) 

side, and there possesses some of the features of a mountain. 

A few miles to the north and west of Cottonwood Butte there are 

low hills, composed of rocks which are older than the Columbia River 

lava, which, like the main butte, are islands in the lava plain. As 

sheet after sheet of molten rock was ·poured out and flowed over the 

land, it rose higher and higher on the sides of the once prominent 

mountains, but the inundation ceased before they were completely 

buried. Neighboring peaks of lesser height were no doubt covered, 

and ages hence will be revealed through the agency of erosion. 

Another group of mountain summits left as islands in the lava sea 

occurs on the west side of the South Fork of Clearwater River, 

between the towns of Stuart and Kamiah, rising to elevations of 500 

or 600 feet above the cooled and hardened surface. The Kamiah 
BUSSELL.] PRE-TERTIARY TERRANES. 23 

Buttes, as they have been named, are between the canyon of the South 

Fork, which there is 1,800 feet deep, and the smaller but nearly as 

deeply cut canyon of Lawyers Creek. The nature of the rock forming the buttes is not definitely known, but what probably are portions 

of the same mass are exposed in the canyon of the South Fork; they 

are granite-like in character-more definitely, diorite. The buttes are 

without timber, and to some extent are now under cultivation. They 

consist of several rounded summits, and are to be classed with the 

foothills of the Bitterroot Mountains, now separated from them by 

about 6 miles of lava. A view of Camas Prairie, showing the Kamiah 

Buttes in the distance, is shown in Pl. III, B. 

Another island-like area in the lava bed, of small size and rising 

only a few hundred feet above its surface, occurs 5 or 6 miles to the 

south of the Kamiah Buttes, on the brink of the canyon of the South 

Fork. Still another area, with a similar history, is situated farther 

north, on the west side of the same canyon, opposite Greer; from 

Kamiah Prairie it appears as a low hill with an undulating surface. 

Another and less conspicuoqs example occurs on the east brink of the 

canyon of Snake River, near Waha, but in this instance there is some 

question whether the elevation of old igneous rock now exposed was 

an island in the lava or was covered by it and has since been exposed 

by erosion. • 

Isolated mountain peaks rising through the Columbia River lava, of 

the general nature of those described, form conspicuous and instructive features in several portions of the vast region occupied by that 

formation, and are of such importance as to demand a family name by 

which to designate them. Steptoe Butte, near Garfield, Washington, 

which has been described in a previous paper, 1 is a typical example of • 

these eminenc~s, and its name may with propriety be adopted as a generic term by which to designate simila:r topographic forms. A steptoe, then, is an island-like area in a lava flow. Cottonwood Butte and 

the Kamiah Buttes are the largest steptoes in the Nez Perce region. 

These are far exceeded, however, by the Eagle Creek Range (known 

also as the Powder River Mountains) in Oregon, which, as stated by 

Lindgren, 2 consist of bare, rugged peaks that rise several thousand feet 

above the basaltic plateau surrounding them on all sides. This, the 

greatest steptoe known, has a diameter of 24 miles. 

FORMATIONS BENEATH THE COLUMBIA RIVER LAVA. 

As is indicated on the map forming Pl. II, the older group of rocks 

in the Nez Perce region is exposed in the deeper portions of several 

of the larger canyons that have been excavated in the Columbia River 

lava. The principal outcrops of this nature are along Clearwater 

1 A reconnaissance in southeastern Washington, by I. C. Russell: Water-Supply and Irrigation 

Paper U.S.Geol.Survey No.4 (1897}, pp. 38-40. 

2Twentieth Ann. Rept. U.S. Geol. Survey, Pt. III, p. 92. 
24 GEOLOGY, ETC., OF NEZ PERCE CO., IDAHO,-PART I. [No. 53. 

River and several o:f its tributaries to the east o:f Peck; along Snake 

River above the mouth o:f Grande Ronde River; in the vicinity o:f Buffalo Rock; and on the sides o:f the canyon o:f Salmon River near its 

junction with Snake River and again at several localities :from 20 to 30 

miles above its mouth. 

Near its mouth the North Fork o:f Clearwater River has cut through 

a thousand or more :feet o:f basalt and deep into the underlying diorite 

and gneiss. The portion o:f the canyon sunk in these older rocks is 

steep-sided and all but impassable. Beginning about 6 miles above its 

mouth, however, the basalt comes down to the stream, and :for 4 or 5 

miles the canyon broadens so as to leave room :for a :few small :farms 

on its western side, where it is about 2,000 :feet deep. About a mile 

below the mouth of Elk Creek the older group o:f rocks appears again 

in the lower portion o:f the canyon wall and eontinues :for at least 25 

miles upstream, probably to the eastern edge o:f the basalt. Throughout this distanee the roeks beneath the lava are mainly gneiss and mieaschist rich in garnets. In plaees the older terranes are traversed by 

light-colored porphyritie dikes, and in a :fe,w instanees by dikes o:f dark 

rock apparently o:f the same nature as the lava whieh :forms the upper 

portion o:f the walls of the canyon. One o:f the dikes is :from 250 to 

300 :feet wide, nearly vertical, and trends N. 10° W. The struetural 

lines in the gne"iss and schist have nearly the same strike, and the apparent bedding and planes o:f schistosity dip eastward at an angle o:f from 

70 to 80 degrees. At many localities along the river the lower portion 

o:f the canyon walls, up to a height o:f, in general, 800 to 1,200 :feet, are 

composed o:f the older group o:f rocks and are bold and precipitous. 

At the summit o:f these steep lower slopes there is usually an irregular 

' terrace, due to the more rapid recession o:f basalt which overlies the 

more ancient mica-bearing rocks, while the upper portion o:f the canyon 

walls, 500 to 1,000 :feet in heig4t, according to the irregularities o:f the 

sub basaltic floor, is diversified by alternate promontories and recessions. The summit of the canyon walls is frequently marked by a 

rim rock formed by the edge of the topmost layer of basalt which 

forms the surface o:f the bordering uplands. The great forest-covered 

plateau in which the North Fork has sunk its channel rises, with a 

gentle gradient, toward the east, and the basalt which underlies it 

grows gradually thinner when traced in that direction, although there 

are many important irregularities in thickness, and the influence of 

the underlying rocks on the topography of the canyon walls becomes 

more and nwre marked. 

When the· region traversed by the North Fork is studied in detail, 

it will probably be found that there is a .progressive change in the 

rocks beneath the basalt, in reference to metamorphism, from west to 

east, until the granite, which begins near Rocky Crest and extends at 

least 20 miles eastward from that peak, is reached. This is seemingly 
RUSSEU.] PRE-TERTIARY TERRANES. 25 

in keeping with the conelusion reached by Lindgren, that the granite 

of the Bitterroot Mountains is intrusive and has altered the rocks 

along its contact; but the greater part of the metamorphism observed 

in the rocks along the North Fork is probably regional and of older 

date than the granite. 

At Orofino, for several miles both up and down each side of Clearwater River, and also along Orofino Creek for a distance of 2 or 3 tniles 

from its mouth, the n1ica-bearing rocks beneath the basalt are well 

exposed. In this region the suhlava formations are mainly gneiss, 

mica-schist, crystalline litnestone, and quartzite. This association is 

_ essentially the same as occurs in Snake River Canyon, where black 

slate also is found, and it is to be expected that slate is also present in 

the neighborhood of Orofino. The limestone is in well-defined beds, 

associated with mica-sc~ist. The beds are nearly vertical and strike 

N. 15° to 20° W., which is also the general trend of all of the conspicuous division planes in the older group of rocks, and shows the 

influence of a force acting in an east-west direction. In common with 

all other portions of the canyon in the Nez Perce region in which the 

older group of rocks is exposed, the topography of the bluffs in the 

vicinity of Orofino reveals the junction of the overlying basalt with 

the rocks on which it rests; but, as is common in other instances also, 

the precise contact is almost always obscured by landslides and talus 

slopes. · 

The rocks exposed beneath the basalt near Orofino can be traced 

continuously along Clearwater River and its south fork to near 

Kamiah, and appear again in the west wall of the canyon about a mile 

above that town. The same group of rocks is also exposed along 

several of the streams which join Clearwater River from the east, as 

well as along the main stream above its junction with the South Fork. 

In the lower portions of the canyon walls in the vieinity of Greer, a 

light-colored diorite resembling granite is the most important member 

of the older terrane. 

In the first 6 miles of its course below the great bend near Keuterville, Salmon River cuts at least three ridges of hard, resistant rocks 

belonging to the series which occurs beneath the lava. At each of 

these lo~alities the strean1 is narrow, and rushes through the flumelike trenches with a swift, foaming current. The topography of the 

walls of the canyon permits one to trace in even distant views the outcrops of the rocks beneath the lava, and to distinguish their junction 

with the black, horizontally bedded basalt resting on them. In this 

canyon, as in many others in the Nez Perce region, the older rocks, 

consisting largely of light-colored, acid, igneous rock, are more resistant to atmospheric influences than is the basalt resting on them, and 

form conspicuous shoulders on the lower portions of the mountain-like 

spurs wh.ich extend into the canyon from either side. Where the 
26. GEOLOGY, ETC., OF NEZ PERCE CO., IDAHO.-PART I. [No. 53. 

basalt descends to the river the trail by which one can traverse the 

oanyon from its mouth to near Keuterville descends also, and follows 

the bank of the river or runs near it; but where the rocks beneath the 

basalt ft.re exposed the immediate banks of the river are precipitous, 

and the trail ascends and crosses the promontory at an elevation of, in 

general, about 1,000 feet above the bottom of the canyon. Below 

Deer Creek, which comes from the north and joins Salmon River about 

15 1niles from its mouth, the river flows over basalt and is bordered by 

magnificent mountain-like escarpments of the same rock, in which the 

bedding iH essentially horizontal. The basalt continues along the 

margin of the river to within 4 or 5 miles of its mouth, where, as 

already stated, it enters a deep, narrow, impassable canyon in quartzite, 

diorite, and other exceedingly resistant terranes. Some of the finest 

canyon scenery in Idaho is along this portion of Salmon River and in 

the still greater excavation made by Snake River near its mouth. 

Snake River Canyon between the mouths of Salmon and Grande 

Ronde riverH presents the most varied and instructive exposures 

of the sublava formations to be found in the Nez Perce region. Some 

account of the rocks there laid bare by the excavation of a mighty 

trench through the lava and deep into the formations on which it rests, 

as "-·ell as of other similar outcrops a few miles below the mouth of 

Grande Ronde River, in the vicinity of Buffalo Rock, has been given 

in a previous publication, 1 and although additional facts are here pregented much more study must be given to this instructive area 

before its complete history and the economic importance of its building stone and ores can be presented. 

Beginning at the first exposure of the sublava rocks, in ascending 

Snake River above Lewiston, we find, just west of V\-T aha, on the right 

or eastern border of the canyon, a bold bluff of ancient porphyry 

which descends to the river. On the opposite bank there is a small 

outcrop of the same rock, showing that the river in deepening its canyon in the lava sheets was lowered onto a spur of a buried mountain 

and cut a channel across it. The precipitous, mountain-like bluff of 

igneous rock (diorite-porphyry) referred to rises 3,300 feet (aneroid 

measurement) above the river. From its rounded summit a most 

instructive view can be had of the deeply dissected Java plateaus about 

its base. This bluff iH at the southwest end of Craig Mountain, 

and probably formed a small steptoe which rose above the level 

of the last ~beet of Columbia River lava. The basement rocks forming the bluff have been laid bare by the erosion of Captain John and 

Buffalo Creek canyons, and are well exposed at Buffalo Rock. The 

walls of Snake River Canyon from above the outcrop of old igneous 

rocks just mentioned to about 1 mile above the mouth of Grande Ronde 

River are composed, from base to summit, of horizontally.be?ded lava, 

1 Water-Supply and Irrigation Paper U.S. Geol. Survey No.4 (1897), pp. 31-36. 
ltUSSELL.] PRE-TERTIARY TERRANES. 27 

showing that a deep valley in the old land surface was there filled by 

the lava flows. Upstream from the mouth of Grande Ronde River, as 

briefly described in the publication just cited, the horizontal lava sheets 

in the canyon wall abut against cliffs of schist which form the precipitous border of a buried mountaii1. The side of the old mountain slopes 

at an angle of about 45 degrees, and is free from debris. Its base is 

evidently far below the level o~ Snake River. Each successive layer 

of basalt extends farther and farther over the metamorphic rock. until, 

at a height of 2,500 feet, the summit of the old mountain is covered 

and the horizontal sheet" of lava above it have an aggregate thickness 

of not less than 1,500 feet. The strata beneath the lava are generally 

inclined northward at an angle of 40 to 45 degrees, but in places are 

nearly vertical. The upper layer of thin-bedded limestone contains 

indefinite fossils. Beneath the limestone are schists, and farther 

upstream an immense mass of compact igneous rock of the nature of 

greenstone (dwrite) is exposed in the cliffs which rise steeply from the 

river to a height of a thousand or more feet. The same rock may also 

be studied to advantage in the small tributary canyons which come 

down, with steep gradients, to the main stream from each side. 

Farther up Snake River there are associated with the greenstone 

extensive outcrops of fine, even-grained diorite (granite) suitable in 

every way for architectural uses. This '' granite" has been opened 

by quarrying on each side of the river near where Corral Creek joins 

it. as well as at another locality a mile or two below. 

The rocks beneath the basalt are exposed in the lower 2,000 feet of 

the canyon of Snake River all the way upstream from Corral Creek to 

above the mouth of Salmon River, but they were examined by the 

writer at only one locality, namely, where Cougar and Cottonwood 

creeks descend the eastern escarpment. The creeks referred to are 

small streams, fed principally by springs which come out at the base 

of the basalt, but they have cut deep canyons in sandstone, shale, 

limestone, and diabase-porphyry. The stratified rock<s are much 

disturbed, but in general the beds strike about northeast and southwest, or directly across the course of Snake River. The dip of the 

beds shows great variation, indicating that the beds were disturbed, 

largely, perhaps, on account of the intrusion of porphyry beneath 

and among them, forming dikes. The sandstone is coarse, feldspathic, and hard, and contains well-rounded pebbles of dense igneous 

rock. Certain layers are exceedingly coarse, being in reality conglomerates, containing water-worn pebbles 6 or more inches in 

diameter. The shale is fine-grained, black, frequently has a glossy. 

surface, and on weathering breaks into sliver-like fragments a few 

inches long and a fraction of an inch in diameter. Its thickness is 

evidently great, probably a thousand or more feet, but owing to the 

disturbances it has suffered it can not easily be measured. It is 
28 GEOLOGY, ETC., OF NEZ PERCE CO., IDAHO.-PART I. [No. 53. 

especially well exposed along Cougar Creek, where it immediately 

underlies the basalt. Limestone occurs on Cottonwood Creek, and 

forms well-defined layers which show a diversity of dips. At one 

locality these strata have a thickness of about 60 feet, but in most 

places they extend to mueh greater depths. The limestone is compact, 

bluish in color~ and without recognizable fossils. The variety of 

rocks at the locality referred to and the abundance of good exposures 

make it a favorable place for a detailed study of the geology and 

topography of the old land over which the Columbia River lava was 

outpoured. 

In Snake River Canyon, near the mouth of Salmon River, quartzite 

and diorite are exposed; and the trenches cut through the basalt and 

a thousand or more feet into the underlying terranes become narrow, with exceedingly rugged and precipitous walls, where the older 

rocks are exposed. 

The geologic age of the sedimentary beds referred to as occurring 

in the canyon of Snake River is unknown, but, judging from the few 

obscure fossils obtained and from the result of Lindgren's studies in 

what is probably a southern extension of the sa..ne terranes in Seven 

Devils Mountains, they probably belong, in part at least, to the Carboniferous. 

COLUMBIA RIVER LAVA. 

HISTORY. 

On the preceding pages many references have been made to the 

formation here specially considered, the reason being that it forms so 

important a feature in both the geology and geography of the Northwest that but little can be written about the natural conditions and 

economic development of that region without frequent reference to it. 

The rocks here termed the Columbia River lava 1 are exposed nearly 

everywhere in the canyon walls of the Nez Perce region to the west 

of the Bitterroot Mountains, and are familiar to all of its inhabitants. 

They were poured out in a molten condition, and hence come under 

the general meaning of the term lava, but more definitely, and from 

the point of view of the petrologist, they should be designated basalt. 

Either of these terms may be used in referring to them. 

The lava in the region under review is a part of a terrane that is 

among the most widely distributed of the geologic formations of the 

continent. Its exact boundaries have not been 'traced, but enough is 

known concerning them to determine approxinl.ately .the area it occu-

. pies. It lies almost entirely within the drainage area of Columbia 

River, for which it is named, forming the surface over nearly the 

IJn previous reports this formation has been termed Columbia lava; but to avoid confusion with the 

ColumbiajormaUon of the Atlantic States, it has been thought best to change the name to ColwnlJia 

River lava. 
RUSSELL.j COLUMBIA RIVER LAVA. 29 

whole of Washington and Oregon to the east of the erest of the 

Cascade Mountains, and extending into Idaho until it meets the older 

formations, prhcipally mica-bearing metamorphic rocks and old eruptives which form the Camr d~Alene and Bitterroot mountains. The 

same great series of lava sheets extends into southern Idaho, where 

they have been deeply trenched by Snake River. The area of the 

formation is estimated to be 200,000, possibly 250,000, square miles, 

and its greatest known thickness more than 4,000 feet. 

The lava was outpoured at successive intervals embracing a long 

period of time, as is shown by the occurrence, at several horizons, of 

layers of sedimentary material, principally clays and sand, between the 

lava sheets. In places, also, the lava sheets are separated by layers of 

volcanic dust containing the silicified trunks of trees which grew on 

a soil formed by the decay of the underlying layer, thus showing that 

the intervals between the flows were in some cases a century or more 

in duration. The lava came through fissures in the earth's crust-in 

what are known as fissure eruptions-and spread widely over the land, 

from which it is evident that each sheet was spread out horizontally. 

The movements that have occurred in the layers since they cooled and 

hardened, and which have caused them to be deformed from their original horizontal position, can be studied in the same way as the structure of sedimentary beds. Although the lava sheets are still essentially 

horizontal over broad areas, they frequently have gentle dips, and in 

certain regions are tilted and even sharply folded and faulted. On the 

eastern slope of the Cascade Mountains the lava sheets occur with a 

dip to the eastward, for long distances, of 3 or 4 degrees, showing that 

a large part of that range has been elevated to a height of at least 

6,000 feet since the lava was poured out. Similar but less extensive 

deformations have also oceurred on the eastern side of the lava-covered 

country, as will be described further on. Between these bordering 

areas is the region of the Great Plains of the Colmnbia, and southward from it, in Oregon, the lava sheets have, in general, been but 

little disturbed from their original horizontal position, althDugh a 

subsidence of three or four thousand feet has probably taken place. 

Extensive movements in the earth's crust occurred also at certain 

periods during the time the lava sheets were being formed, as is shown 

near Clealum, Washington, on the eastern slope of the Cascades, 

where the upturned and eroded lower portion of the formation is overlain unconformably by later sheets. How widely extended this unconformity may be remains to be determined. 

The fact that the Columbia River lava came to the surface through 

fissures, as molten rock, and that it spread widely over the land, is 

shown not only by the generally level condition of much of its surface 

as it exists to-day, and by the absence of volcanic mountains, cinder 

cones, etc., in connection with it, but is demonstrated in a most 
30 GEOLOGY, ETC., OF NEZ PERCE CO., IDAHO.-PART I. [No. 53. 

instructive manner where denudation has exposed the dikes formed by 

the cooling of the liquid magma in the fissures through which it was 

forced to the surface. Over an area of at least 400 square miles on the 

eastern slope of the Cascade Mountains in Washington, to the south of 

Mount Stuart, the lava has been eroded away so as to lay bare the 

rocks on which it formerly rested. In the surface there exposed many 

hundreds, probably thousands, of dikes are to be seen. These dikes, 

composed of dense basaltic rock, range in thickness from a few feet 

to 160 or more feet, but in general they are from 15 to 60 feet across. 

They stand nearly vertical, usually with a slight inclination to the westward, and in general trend about N. 15° E. 1 

The vast lava flows just considered spread over the land surface like 

an inundation, covering the broad plains and extending far into the 

valleys previously eroded in the slopes of the bordering mountains. 

Although the lava is of volcanic origin, its surface presents marked 

contrasts to the topographic changes produced by eruptions through 

definite and circumscribed vents. Volcanoes generally tend to roughen 

the surface where they occur, and to build up mountains, thus increasing the diversity of the i·elief. Fissure eruptions, on the other hand, 

owing to the vast volumes of liquid rock poured· out, tend to spread 

out widely and to obliterate the inequalities of the land over which 

they flow, and produce horizontal surfaces. For this reason it is safe 

to assume that the entire region oecupied by the Columbia River lava 

was a monotonous plain nearly as -level as the ocean's surface at the 

time each successive sheet of mo]ten rock was outpoured. The surface 

was no doubt rough and strewn with broken fragments of the firstformed crust, and, as cooling progressed, it was in places forced up 

into mounds and low ridges, which were probably cracked open at the 

top, as is the case to-day on the very fresh lava sheets forming the Snake 

River plains; but these small features would not detract from the general monotony. Again, some diversity of surface was no doubt produced owing to the uneq~al extent of the various lava flows. Although 

individual sheets are known to have a great area-their edges as 

exposed in canyon walls in many instances being traceable for a score 

or more of miles without noticeable variations in thickness and without any indications of approaching a limit-it is not to be supposed 

that each one had precisely the same extent as its predecessor. and 

differenees in elevation from this eause are to be surmised. 

Where a lava sheet was thickest a greater amount of vertical shrinkage on eooling would oceur than where it was thin, and in such depressions shallow lakes would form. The greatest influence on the streams, 

however, occurred from the fact that the lava invaded the lowlands 

and entered the lower portions of the valleys in the mountains, thus 

IA preliminary paper on the geology of the Cascade Mountains in northern Washington, by I. C. 

Russell: Twentieth Ann. Rept. U.S. Geol. Survey, Pt. II, pp. 121-122. 
U. S. GEOLOGICAL SURVEY WATER·SUPPLY PAPER NO. 53 PL. IV 

CANYON OF SNAKE RIVER NEAR WAHA. 
RUSSELl •. ) COLUMBIA RIVER LAVA. 31 

obstructing the dt·ainage and furnishing conditions for the origin of 

extensive lakes. The truth of this ded uetion i~ verified by the presence of lacustral deposits, some of them of great thickness and wide 

extent, interbedded with the lava sheets. 

The age of the lava, as determined principally from the fossil plants 

contained in the sedimentary layers and beds of volcanic dust interstratified with it, is Tertiary. It seems to have been outpoured 

mainly ~._luring the medial division of the Tertiary, or during the Miocene epoch. 1 The time when the eruptions ceased has not been determined, and if the lava forming the Snake River plains in southeastern 

Idaho i~ included in the same formation as that of the central portions 

of Oregon and Washington, it. will probably be found to extend into 

late Tertiary, or po:ssibly into the Pleistocene division of geologic time. 

In the history of the Columbia River lava Nez Perce County and 

the country adjacent on the east occupy an important place, for 

there the lava met the mountains which form the eastern border of 

the region it inundated. Although the western shore of the sea of 

molten rock in the same latitude is not definitely known, it ~as to the 

west of the present crest line of the Cascade Mountains and at least 

250 miles distant. 

The lava is well exposed in the canyon walls throughout the region 

under consideration, all through the Palouse country and the Great 

Plains of the Columbia in Washington, and throughout central and 

eastern Oregon. In the central portions of each sheet the rock is 

usually compact and massive, nearly black in color' and is typical 

basalt. As determined by J. S. Diller, 2 it is composed of plagioclase, augite, olivine, and magnetite, with considerable globulitic base. · 

An exception to the prevailing characteristics of the lava occurs 

in the rock on the eastern side of Snake River Canyon, at Corral 

Creek, and again near the junction of Snake and Salmon rivers. At 

each of these localities, at a depth of about 2,000 feet below the 

top of the formation, there are exposures .of a sheet of black rock, 

from 90 to 100 feet thick, which contains crystals of labradorite an 

inch or more across. Below and above this sheet are layers of the 

normal and in places markedly characteristic Columbia River lava. 

In the central portions of thick sheets the rock is frequently columnar 

in structure, illustrated by a conspicuous example at what is known 

as the Candle Rock':!, on the left bank of Snake River about 3 miles 

below Lewiston. While the Ce\ltral portions of the sheets are hard, 

compact, without steam holes, and frequently are conspicuously 

jointed, their upper and lower portions are irregularly and confusedly jointed, and usually are scoriaceous. The scoriaceous layers 

are likely to be of a reddish color; occasionally they are bright red, 

1 F. H. Knowlton, Bull. U.S. Geol. Survey No. 108, pp. 103-104. 

2Water-Supply and Irrigation Paper U.S. Geol. Survey No.4, p. 43. 
3 2 G EO LOGY, ETC. , OF NEZ PERCE CO., IDAHO. -pART I. [No. 53. 

due to the oxidation of the iron which they contain. The number; of 

separate sheets in an exposure, as in the wall of a canyon, for example, is usually difficult to determine, on account of the disintegration 

that has occurred and because of the prevalence of talus slopes and 

landslides, but an approximation to the actual number can be made 

by counting the layers where the rock is sufficiently massive to stand 

in vertical walls. On the sides of Snake River Canyon between 

Asotin and the mouth of Grande Ronde River, where the cliffs are 

about 2,000 feet high, from 12 to 15 sheets of lava are exposed. An 

estimate made in the same canyon, near Corral Creek, by counting the 

layers of scoriaceous r·ock, gave a still larger number. The thickness 

of the sheets is in general from 50 to 150 feet. The appearance of 

the edges of the lava sheets exposed in the walls of the numerous 

canyons excavated in it is well shown in Pls. IV and V, B, which also 

indicate the extent to which they are concealed beneath their own 

debris. On the surface of the plateaus between the canyons such 

deep decay has occurred that usually no hard rock is seen. In fact 

one might travel many miles through the cultivated fields above the 

lava without finding a fragment of rock of sufficient size to show its 

common features. 

The feature of the lava which is of greatest interest in connection 

with the possibilities of obtaining artesian water is its texture. Is it 

sufficiently porous to permit water to percolate through it, or should 

it be classed as impervious? The compact portions of the rock should 

no doubt be ·considered impervious; but it is so generally broken into 

blocks or columns, by joints, that the ability of even thick sheets 

to retain water in a lower porous layer under pressure is doubted. 

The scoriaceous surfaces of the sheets where they come in contact are 

sufficiently open to permit the ready passage of water through them, 

and if interbedded with clay or some similar material they would 

furnish one of the requisite conditions for flowing wells. In this con 

nection the sheets of volc~nic dust and the beds of sedimentary material interstrati:fied with the basalt demand careful study. 

SHEETS OF VOLCANIC DUST. 

Between the sheets of Columbia River lava there are, at several 

~ocalities, beds of almost pure white, fine-grained volcanic. dust, which 

was blown out of some distant volcano and widely spread over the 

land through the agency of the wiRd. Exposures of this material, 

known locally as magnesia, occur beneath the Candle Rocks, on the 

left bank of Snake River below Lewiston; near Swallow Rock, between 

Clarkston and Asotin; on Asotin Creek, about 10 miles from its mouth; 

on Captain John Creek; at several localities in the canyon of Grande 

Ronde River; and at a number of place.s on eaeh side of Potlatch Canyon. The exposures referred to, which occur on the west side of 
U. S. GEOLOGICAL SURVEY V,ATER-SUPPLY PA.~ER NO. 53 PL. V 

A. SOUTHERN SLOPE OF COTTONWOOD BUTTE. 

B. COLUMBIA RIVER LAVA IN SALMON RIVER CANYON. 
RUSSELL.] COLUMBIA RIVER LAVA. 33 

Snake River, probably belong to a single sheet, the positio.n of which 

is about 200 feet below the surface of the topmost layer of lava as it 

exists to-day; but most of the exposures are in landslides, and the 

exact position where they occur in place has not been determined. 

The evidence seems to indicate that in the region under review there 

are several layers of volcanic dust, some of them mingled with sedimentary material. These deposits are of special interest in connection 

with the question of obtaining artesian water, as the coarser layers 

more particularly are sufficiently porous to permit water to percolate 

through them. This is shown not only by their texture but by the fact 

that in certain instances, where their edges are exposed, springs come 

to the surface, the water having a peculiar opalescent or slightly 

milky appearance, due to the exceedingly fine particles of dust held in 

suspension. These layers frequently contain fossil leaves, which 

afford excellent illustrations of the nature of the varied and luxuriant 

flora which clothed the lava plain at the time the dust showers occurred, 

and also serve to define the stratification of .the lava sheets with which 

they are associated, and, further, they are of economic importance, as 

will be shown further on. 

Near the heads of many of the small streams, particularly at the 

lower extremities of small gulches, down which there is only an occasional flow of water, there are, throughout a wide extent of territory 

in eastern Washington and adjacent portions of Idaho, small surface 

deposits of fine w bite material, usually designated by herdsmen and others as alkali. If examined under a microscope, however, this material 

will be found to be composed of small angular grains and shreds having a glass-like appearance; to be, in fact, volcanic dust, which chemical analyses prove it is. The deposits referred to are usual]y from a 

few inches to 6 or 10 feet, possibly Iilore, in thickness. Characteristic 

examples occur on Cottonwood and Cougar creeks, which flow into 

Snake River; about the mouth of several of the small gulches opening 

into the canyon occupied by China Creek, and elsewhere, particularly 

in the southern portion of Nez Perce County. In all of these instapces 

the dust has accumulated in alluvial cones or flood plains near the 

mouths of gulches which are usually dry, and bas not been noted where 

the conditions favor rapid transportation. Evidently it was brought 

down by brooks and rills flowing through the small ravines and 

gulches at the mouths of which it is now found, and was deposited at a 

recent date. The probable explanation of these occurrences is that a 

light shower of volcanic dust occurred over the Northwestern States 

not many year1:l ago, and that the material has been washed from the 

steeper slopes and in part accumulated in the flood plains and alluvial 

cones of small, particularly of intermittent, streams. The larger 

streams, which must also have received their share of the material, 

being able to carry it away, evidence of the shower is now to be found 

IRR 53-01--3 
34 GEOLOGY, ETC., OF NEZ PERCE CO., IDAHO.-PART I. [No. 53. 

in only sheltered situations. That these accun1ulations of volcanic 

dust are not due to the washing out and redeposition of the similar 

material from between the sheets of the Columbia River lava is shown 

by the fact that characteristic Pxamples of the deposits occur at the 

mouths of gulches which drain areas of the older group of rocks only, 

as, for example, on some of the tributaries of Cougar Creek, from 

which the lava has heen removed hy erosion and deep trenches excavated in the shale, limestone, etc., beneath. 

An analysis of a characteristic sample of the dust from Cottonwood 

Creek, one of the small tributaries of Snake River, in the southern 

part of Nez Perce County, is given herewith, which shows that it is 

richer in silica, potash, and soda than the basalt which forms the 

Columbia River lava. Evidently the fissure eruptions which furnished 

the basalt ca11 not be responsible for the dust, which must have come 

from some distant volcano in a state of explosive eruption and discharging acid lava. The fineness of the dust, which frequently equals 

that of ordinary wheat flour, also indicates that it was brought from a 

distance by the wind, all coarse particles being dropped on the way. 

A 1wly.si.~ of ·mlcauic dust from Cottonwood Canyon, Idaho. 

[W. F. Hillebrand, analyst.] 

Constituent. 

Silica (Si02 ) .......................... .. 

~~~ri~~~i~~128!~i>~):::::::::::::::::::: Ferrous oxide (FeO) .................. . Magnesium oxide (MgO) .............. . Calcium oxide (CaO) ................. .. Sodium oxide (N~O) ................. .. Potassium oxide (K20) ................ . Water, hygr~scopic (H20-) ........... . Water, combmed (H20+) .............. . 

Percent. 

68.95 

14.33 

1.17 

1. 23 

0.47 

2.13 

5.08 

2.58 

0. 28 3.63 

Constituent. I Per cent. 

Titanium oxide (Ti02) ................. 1 0.42 Zirconium oxide (~r0 ) • • • • • • • • • • • • • • • • 0. 03 Phosphorus pentox1d (P20 5) ••••••••••• ·1 0.10 Chlorine (Cl) ........................... (?l Fluorine (F) .. .. .. .. .. .. . . . . . . . .. .. . . . . (? 

Sulphur (S) ................ .... .. ...... Trace. Manganous oxide (MnO) . . . . . . . . . . . . . . Trace. Barium oxide (BaO).......... ..... . . ... 0.08 Strontium oxide (SrO) . .. . . . . . . . . . . . . . . Trace. Lithium oxide (Li20) . . .. . . . . . . . . . .. .. . Trace. 

Total ............................. _ 100. 48 

The dust referrecl to became mingled with the soil of the plateau 

and served to increase its percentage of, especially, silica, potash, and 

soda. While the dust of the particular shower of which evidence 

remains can not be eonsidered as having made a notable increase in 

the richness of the soil in potash, it is possible that older showers, all 

direct evidence of which has been lost, may have assisted in the same 

direction, which would explain the greater percentage of potash in 

the soils of the lava-covered region than is contained in the rocks from 

which they originated, as will be explained further on. 

DEPOSITS OF LAPILLI. 

When a lava flow encounters a body of water steam is generated, or 

the water is, perhaps, decomposedandoxygenand hydrogen are evolved, 

which, if ignited, cause an explosion. In either case the hot rocks are 

likely to be blown into fragments, which are covered by the lava in 

case it eontinues to advance. The fragments produced in this manner 
RUSSELL.] COLUMBIA RIVER LAVA. 85 

are angular, frequently of the size of gravel, and on account of the 

rapidity with which the hot magma cools they usually have a glassy 

texture, or when broken resemble bits of overburned earthenware. 

Deposits of this material known as lapilli occur in the Columbia River 

lava at several horizons, but usually seem to be local in their distribution. A characteristic deposit, in which the angular, glassy grains 

are incrusted with a yellowish coating, probably of ferric chloride, is 

exposed near Swallow Rock, a few miles below Asotin, along the 

aqueduct which supplies Clarkston with water. Another deposit can 

be seen above the conspicuously columnar basalt forming a colonnade 

along Snake River between Clarkston and Alpowa; and others of a 

similar character but of smaller extent and thickness and usually associated with highly scoriaceous lava, are known at a few other localities in the Nez Perce region. The lapilli is seemingly too local in its 

distribution to have much significance in reference to the occurrence 

of artesian water, but as it is associated with the scoriaceous portions of 

lava flows and occurs between lava sheets, it would favor the passage 

of water through the rocks. Its principal geologic interest lies in the 

fact that it furnishes a part of the evidence by which separate lava 

sheets may be d~stinguished. 

SEDIMENTARY BEDS. 

During each interval between the inundation which spread out the 

sheets of Columbia River lava, the streams from the bordering uplands 

brought down debris and deposited it on the newly formed surface. 

When the intervals between the eruptions were long, the quantity of 

debris swept down from the uplands would increase, and it would be 

deposited as alluvial cones at the mouths of valleys, or perhaps be 

spread out in lakes on the lava plains and form deltas or possibly 

widely extended layers of lacustral sediment. It is therefore to be expected that both fluvial and lacustral deposits will be found at several 

horizons where a number of lava sheets occur one above another. 

This expectation hab been realized in the Nez Perce region, by the discovery of several localities where beds of clay, sand, gravel, etc., 

occur between sheets of Columbia River lava. One of the most 

instructive of these is on the farm of Ira Small, about 6 miles east of 

Lewiston (sec. 1, T. 35, R. 5), where a well, drilled with the hope of 

obtaining artesian water, passed through the following strata: 1 

1 In the first layer of basalt mentioned an inflow of water amounting to about 4 barrels an hour was 

obtained at a depth of 140 feet from the surface. This fact, taken in connection with observations 

made elsewhere, indicates that the basalt above the sedimentary beds reported in the section is in 

reality composed of two separate sheets-the upper one fl,bout 140 to 150 feet thick and the lower one 

from 90 to 100 feet thick. When the drilling had reached a depth of approximately 300 feet, and was 

at about the bottom of the sand, as stated by Mr. Small, ''there was an escape of air which had sufficient force to blow off a 2-inch plank when laid over the top of the well." This so-called air was not 

inflammable, and may have been carbonic acid gas? At the base of the clay an inflow of water was 

obtained sufficient for the purpose of continuing the drilling in the underlying basalt, but no water 

under pressure was encountered. The well is 6 inches in diameter (tool 5t inches), and is cased to 

within about 10 feet of the surface of the lower basalt. 
36 GEOLOGY, ETC., OF NEZ PERCE CO., IDAHO,-PART I. [No. 53. 

Sect-ion about 6 milrs eost of Leuri~~ton, Idaho. 

Feet. 

Soil and subsoil (decomposed lava)__________ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 10 

Basalt, hard, compact, black _________________ . _ _ _ _ _ _ _ _ _ _ _ _ _ _ 210 

Sand (about 60 feet) and clay (from 90 to 100 feet) __________ ._ 160 

Basalt, hard, compaet, black _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 75 

Total _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 455 

The locality where this boring was put down is near the northern 

border of the plateau termed in this report the Lewiston Plateau, which 

at that place slopes gently downward toward the south, in conformity 

with the dip of the strata beneath it. To the north of the site of the 

boring, and from a quarter to a half mile distant, is the brink of the 

south wall of the canyon of Clearwater River, in which are exposed 

the sedimentary beds penetrated in sinking the well. At this locality, 

and at the head of a ~':!mall ravine opening northward into the canyon 

of Clearwater River, a copious spring outflows at the contact of the 

layer of sand with the clay beneath, which has been enlarged, by excavation, so as to supply a neighboring farm with water for household 

use and irrigation. This spring il':! typical of a large number of springs 

in the Nez Perce region, and it will be referred to again in connection 

with certain suggestions for increasing and utilizing the waters of 

some of the porous sedimentary layers which occur between the lava 

sheets by excavating •• horizontal wells." . 

The sedimentary beds penetrated in drilling Small's well, and which 

are exposed in the neighboring gulch, can be traced over a large extent 

of country in the northern and western portions of Nez Perce County 

and adjacent portions of Washington and Oregon. They probably 

extend eastward to the foothills of the Bitterroot Mountains, but as 

there are other similar layers in that region they have not been identified east of Craig :Mountain. All along the sides of the canyon of 

Snake River fron1 near Lewiston-Clarkston to Bufl'alo Creek on the east 

and to the breaks of Grande Ronde Canyon on the west, as well as on 

the sides of the canyons of the various branches of Asotin Creek, and 

of Tammany, Sweetwater, and Lapwai creeks, the sedimentary beds 

referred to are plainly revealed in the topography of the canyon walls. 

The basalt above these beds has been eroded nwre rapidly than the 

layer~':! below, leaving a terrace which, although usually heavily 

encumbered with talus and landslides, can readily be distinguished. 

The terrace extends into each side gulch which opens out into the main 

canyons, and near the heads of these gulches there frequently is a 

spring. The position of the terrace in reference to the surfaces of the 

adjacent plateaus between the drainage lines varies from 200 to 380 

feet. This variation is due in part to inaccuracies in determining precisely where the base of the soft beds occurs, owing to the debris that 

is almost invariably present, and to the differences in weathering which 

the plateaus have experienced. By aneroid measure1nent the terrace 
RUSSET, J,. j COLUMBIA RIVER LAVA. 37 

on the east border of Snake River Canyon near W aha is 200 to 220 

feet below the general level of the adjaeent plateau; on the border of 

the canyon of Asotin Creek it is 370 feet below; and on the Clearwater 

escarpment, which forms the south border of the Uniontown Plateau, it 

is about 250 feet below. The identification of the sedimentary layer 

which determines the presence of the terrace referred to is in places 

rendered somewhat difficult, owing to the presence above it of another 

layer of similar material, whieh is separated from it by a sheet of 

basalt. The nature of these irregularities, which are to be expected 

in so large an area, is shown by the following section, obtained in the 

south wall of Asotin Canyon nearly opposite the mouth of George 

Creek: 

Section in Asot·in (hnyon. 

Feet. 

Soil on the slope descending from the plateau surface, with blocks 

of basalt, exposures poor. ___ . _________________ . ______ . ____ 120 

Basalt, forming a well-defined rim rock._____________________ 35 

Sedimentary beds containing a large variety of well-rounded 

pebbles, some of them 3 to 5 inches in diamder ___________ . 110 

Basalt, forming a bold escarpment, in places broken off and 

fallen in landslides. ____ . _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 150 

Sedimentary bed, tJOft, apparently day_____ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 140 

Basalt, scoriaceous at top and bottom; compact in central part, 

but showing 4 or 5 partings on weathered slopef-1. __________ , 390 

Total _______ . _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 955 

The thicknesses given in the foregoing section are only approximately correct, as the contacts are seldom sharply defined. Judging 

by the plateau surfaces, the upper layer of basalt on Asotin Creek and 

at Small's farm are the same, but the sedimentary beds at the former 

locality are separated by a sheet of bnsn1t about 150 feet thick, and 

their aggregate thickness is 100 feet more than at the second locality 

referred to. A tentative explanation of these differences is that a lava 

flow occurred in the Asotin region which did not reaeh as far to the 

northeast as the loea]ity where the drill hole was put down at Small's 

farm, and that to the east of Lewiston this lava flow practically separates the upper or sandy member of the sedimentary beds from the 

lower or clayey member. The writer confesses, however, th~t the difference may be owing to errors of observation, as the natural exposures 

are obscure and are largely interpreted from topographic forms. 

What is probably a part of the sedimentary beds just considered 

occurs on the south side of the Blue Hi1ls, in the walls of the canyon 

of Grande Ronde River, but there it appears to be thicker than in the 

vieinity of Lewiston, and it rarries one or more beds of lignite. Its 

presence in the locality referred to is sho··wn not only by actual outcrops, usually, however, in landslides, but in a conspicuous manner by 

the topography. On the north side of the river, where the strata dip 
38 GEOLOGY, ETC., OF NEZ PERCE CO., IDAHO.-PART I. [No. 53. 

toward it at a low angle, there have been a great number of large landslides, but on the south side, where the strata dip away from the 

face of the precipices, the cut edges of the beds· stand nearly vertical, 

and the presence of the soft layer near the summit is revealed by a 

well-defined terrace. 

An important feature in reference to these sedimentary beds is that 

when two beds are present, as along Asotin Creek, the upper portion 

of the formation is composed of sand and gravel, and is so open that 

water could flow freely through it. In many instances, as on the escarpment forming the south border of the Uniontown Plateau, the gravel 

contains well-worn pebbles 5 to 6 inches in diameter. The lower portion of the formation, however, is clay -like and is practically impervious. 

Water descending into the sandy and gravelly portion of the formation is arrested by the basalt or the clay beneath it, and there flows 

laterally, thus accounting for the springs which appear where the beds 

are cut by canyons. These springs occur at only certain localities, 

especially near the heads of small gulches, as in most places the outcrops of soft beds are covered with loose material which has fallen 

from above. The large number of canyons, which have been cut to a 

greater depth than the base of the sedimentary beds, in most instances 

precludes the possibility of their receiving water from the mountains, 

and all of the water which issues as springs, or which may be obtained 

by excavating tunnels, must be supplied by the local rainfall. And, 

on account of the deep dissection of the plateaus, it is not to be expected 

that the water in the porous beds referred to could exist under sufficient pressure to supply artesian wells. 

At Denver and Cottonwood, situated on the Camas Prairie within 

the region occupied by the Columbia River lava and at a distance of 

from 8 to 15 1niles from its eastern border, borings (the detailed 

records of which will be presented further on) have been made, which 

show, in connection with natural exposures and the topography of the 

walls of neighboring canyons, that sedimentary beds of considerable 

thickness underlie the surface sheet of basalt. At Cottonwood the 

surface layer of basalt is from 60 to 70 feet thick, as shown by a boring, 

and rests on a sheet of gravel which has been penetrated to a depth of 

56 feet without reaching its base. At Denver, where several borings 

have been made, the surface sheet of basalt appears to be broken. and 

largely disintegrated, as the drill penetrated only loose material to a 

depth of about 200 feet. Terraces on the sides of canyons and occasional outcrops in their walls in the same region indicate that over a 

large portion, perhaps the whole, of the Camas Prairie, layers of open 

and porous sedimentary material are probably present beneath the 

surface sheet of basalt. 

Along the canyon of the South Fork of Clearwater River, from 

Stuart to the vicinity of Peck, there are occasional outcrops of sand-
RUSSELL.] COLUMBIA RIVER LAVA. 39 

stone and allied rock, mostly, however, in landslides, which indicate 

the presence of a .thick sheet of similar material, the surface of which 

is about 800 feet below the general level of the adjacent plateaus. The 

chief evidenee of the presence of this important bed of soft material 

is furnished by the vast nun1ber of landslides that have oeeurred. 

"There the river has not eut below the level of the bed referred to its 

eanyon widens, as at Kamiah, and its sides are formed by hundreds of 

displaeed masses of basalt whieh have fallen from above. A view 

taken near Kamiah (Pl. IX, A) exhibits some of the topographic 

forms referred to. 

Throughout the length of Orofino Creek, fron1 its mouth to near 

Pierce City, there is an almost eontinuous series of heavy landslides 

on each side of the creek, whieh indicates the presence of incoherent 

beds at least 200 or 300 feet in thiekness, beginning at a depth of about 

750 feet below the surface. These strata are probably a continuation 

of those which have so greatly influeneed the topography of the wall 

of Clearwater Canyon near Kamiah and elsewhere. Their character 

is shown by outcrops of sandstone and shale Qarrying lignite which 

are exposed in the bed of the creek at severalloealities. 

Along Little Canyon Creek, whieh drains a portion of the broad 

plateau to the south of Orofino, coarse sandstone associated with carbonaeeous shale occurs just at the base of the preeipitous eanyon 

walls and beneath 800 feet of horizontally bedded basalt. The thickness of this bed is not exposed, but it evidently is eonsiderable, as the 

water pereolating from it is suffieient to maintain Little Canyon Creek 

throughout the dry summer months. 

Again, in the canyon of Potlatch Creek, which joins Clearwater River 

from the north about 18 miles east of Lewiston, there are several outcrops of sedimentary beds inter~tratified with the Columbia River 

lava. In ascending the canyon the first of these exposures is on its 

western side, about 3 miles from its mouth, where some grading has 

been done for a wagon road. There is shown a thickness of about 25 

feet of sedimentary material, consisting largely of voleanie dust, at a 

height of approximately 80 feet above the canyon's bottom. Neither 

the top nor the bottom of the deposit was seen, and it is probably a 

part of a large landslide. This layer is impervious, and a spring finds 

an outlet just above it. A half mile farther upstream, and about 250 

feet above the canyon's bottom, there is a small exposure, 3 to 4 feet 

thick, of yellowish sandstone carrying pebbles. On the wagon-road 

grades which aseend the steep eastern side of the canyon near Juliaetta, there are at least three outcrops of sedimentary beds, one of 

which is evidently in place, or has moved but a short distanee down 

the slope from its true position. It is 250 feet below the general level 

of the neighboring plateau, and consists of coarse granitic sand spangled with mica. A thickness of 8 feet is in sight. Resting on this is a 
40 GEOLOGY, ETO., OF NEZ PEROE 00., IDAHO.-PART I. [No. 53. 

1ayer of sandy, micaceous clay, a thickness of 2 feet of which is 

exposed. Two other outcrops of sedimentary material at lower level~ 

consist mainly of voleanic dust, and are apparently portions of landslides. While owing to the prevalence of landslides and talus but little information was obtained concerning the true position of these 

beds, the differences between the limited outcrops observed show that 

at least two important sheets of sedimentary origin underlie the adjacent plateaus. One of these beds is of open texture, and permits 

the free percolation of water, the other, or lower, is clay-like and 

impervious. The direct connection of these beds with the sheets of 

similar material in the cliffs bordering Clearwater Canyon on the south, 

between Spalding and Lewiston, which are penetrated by the well at 

Small's ranch, has not been traced, but it is probable that they belong 

to the same layers. While the elevations of the outcrops at these two 

loc.alities differ, owing to the movements that have occurred in the 

rocks, the depth of the sedilnentary sheet below the surface of the 

broad plateaus should be in each instance approximately the same. 

In the canyon of Salmon River near the 1nouths of Eagle and Deer 

creeks, for a distance of 3 or 4 miles along its western border, and 

extending a mile or more up the sides of each of the creeks, there are 

five exposures, from 20 to 55 or more feet in thickness, of coarse, yellowish sandstone containing well-rounded pebbles and fragments of 

silicified wood. This bed of sandstone is at a depth of approximately 

3,500 feet in the Columbia Hiver lava, and has beneath it a bed of 

lava with a rough scoriaceous surface. One of the outcrops referred 

to, on the west side of Salmon River just above the mouth of Eagle 

Creek, is interrupted by a promontory of crystalline rock which rises 

into the overlying lava sheets, having formed an island or cape in the 

waters in which the sandstone was deposited. Such an interruption in 

a porous water-bearing sheet illustrntes one class of diffieulties to 

be expeeted in attempting to obtain artesian water from the sedimentary beds interstratified with the Columbia River lava. That is, the 

old land surface over which the lava spread was irregular; the aneient 

peaks and ridges rise into the lava to varying heights, some of them, 

as already noted, remaining as steptoes when the last and highest lava 

sheet flowed about them, while others, and probably by far the larger 

number, were buried to greater or less depths and can only be discovered when denudation has unearthed them or the drill in its descent 

encounters them. As will be shown more fully further on, these buried peaks and ridges of impervious rock may cut off the supply of 

water from an otherwise favorably located porous layer. 

SUMMARY. 

In addition to the observations already noted, others might be cited 

to prove the presence of sedimentary beds between sheets of Columbia River lava, but they are of a qualitative nature and pertain princi-
U •. S. GEOLOGICAL SURVEY WATER-SUPPLY PAPER NO. 53 PL. VI 

A . SANDSPIT IN NORTH FORK OF C LEARWAT ER RIVER. 

R. CANYON OF SNAK E RIVER FROM CRAIG MOUNTA I N. 
RUSSELL.j OOLUMBI.A RIVER LAVA. 41 

pally to the presence of such material in landslides. What is desired 

are definite measurements of the thickness of the sedimentary deposit-:; 

and their depth below the surface; but such quantitative observations 

are difficult to obtain, owing to the peculiar conditions which exist, especially with referenee to the disintegration of the rocks in natural outcrops and the tendency of soft beds beneath lava sheets to give origin 

to landslides. The depth at which a widely ~xten·ded layer of clay, 

sand, gravel, etc., occurs beneath the surface varies from place to 

plaee, owing principally to movements which have affected the rocks 

over broad areas and the amount of surface denudation. From such 

facts as are in hand it is evident that in the Nez Perce region, where 

extensive lava plateaus occur, the presence of porous water-bearing 

beds is to be expected at three principal horizons, namely, at 150 to 

350 feet, at 750 to 1,000 feet, and at 3,500 to 3,600 :feet. Although 

the beds at these appi'oximate depths below the plateau surface in 

which the stratification is essentially horizontal, are widely extended, 

yet at certain localities where the lower beds especially might be 

expected to occur, they have not been found. In Snake River Can-· 

yon above Asotin, where the sedimentary beds would be expected to 

appear at the horizon 750 to 1,000 feet below the sur:faee, no evidence 

of their presence has been obtained. A more eareful search may 

reveal them, but it is evident that if there were present a stratum of 

sandstone of the thiekness and character of the one near Orofino it 

would have a decided influenee on the topography of the canyon walls, 

and such testimony is wanting. The conclusion to be drawn from 

this negative evidence seems to be that the beds under consideration 

did not reach the locality referred to, possibly on account of intervening ridges of the pre-lava formations which cut off the streams from 

the Bitterroot Mountains. 

The general history to be read in these sedimentary beds is that 

the material of which they are composed was brought by streams 

:frmn the mountains bordering the Columbia River lava on the east 

and spread out over the lava from time to time, during the intervals between the eruptions, as alluvial fans and as lacustral deposits. The material thus spread out should become finer and :finer 

when traced away from the mountains that supplied it, and in the case 

of the beds of sand and gravel it should thin out in the same direction. 

·such beds should also be more numerous near the eastern border of 

the lava plateaus than farther west, for after each lava flow some 

material would be washed down upon it from the mountains, but during only the longer intervals would widely extended alluvial :fans be 

formed. For this reason it may be coneluded that the probabilities of 

obtaining artesian water should increase as the eastern margin of the 

last lava flow is approached. 

While the beds of sand and gravel referred to should be considered 

mainly as stream deposits, they may be in part the shore foundations 
42 GEOLOGY, ETC., OF NEZ PERCE CO., IDAHO.-PART I. (No.53. 

of lakes into which the streams flowed. There is no means of determining from occasional exposures under which of these two methods 

sand and gra-vel may have been laid down, and in faet the stream-laid 

beds and the layers of coarse material found in the shallow portions of 

lakes merge into the others hy insensible gradations. The fine clays, 

however, such as those underlying the region about Lewiston at a 

depth of 280 to 300 feet below the surface of -the level plateaus, were 

evidently deposited in ·lakes, and may be widely extended without 

exhibiting marked variations in thickness. During the intervals 

between many of the eruptions lakes probably existed on the surface 

of the la-va, and they would lay down sheets of clay-like material of 

variable thickness, dependent largely on the length of time they 

existed; but the positions of the lakes can not be predicted. It is 

expected, however, that laeustral deposits will be found widely distributed throughout the Columbia River lava, and as they are in general composed of impervious beds, one of the eonditions requisite for 

the storage of water under pressure-artesian-may be present in even 

the eentral portion of the lava-covered eountry. This statement in 

referenee to the probable wide extent of laeustral deposits interbedded 

with the lava is not based entirely on general principles, as thick and 

widely extended foundations of the nature. referred to are known to 

exist in west-central vVashington. On the whole, what is known of 

the sedimentary beds, whether fluviatile or lacustral, interbedded with 

the Columbia River lava is favorable to obtaining artesian water over 

a widely extended region embracing portions of Washington, Oregon, 

and Idaho. 

SOILS. 

As is well known, the material forming soils is con1posed chiefly of 

disintegrated and more or less thoroughly deeomposed rock debris. 

ThiH debris either remains in essentially the position where it originated or is removed from that position and redeposited elsewhere. 

Two leading classes of superficial aeeumulations are thus produced, 

termed sedentary deposits and transported deposHs, in each of which 

important subdivisions have been reeognized. So far as the Nez 

Perce region is concerned, the representatives of the sedentary 

deposits are sneh as have originated from the disintegration and 

deeay of roeks in place, and they may be termed residual soils; while 

the superficial material whieh has been brought frmu a distance and 

redeposited, found principally along the margins of the rivers, forms 

alluvial soils. 

RESIDUAL SOILS. 

The character and mode of origin of the soil in a typical portion of 

the great region occupied by the Columbia River lava has been discussed in a previous report, 1 and but little information in addition to 

lA reconnaissance in southeastern Washington, by I. C. Russell: Water-Supply and Irrigation Paper 

U.S, Geol. Survey No.4 (1897), pp. 57-64. 
RUSSELl •. ) SOILS. 43 

what was then presented can he given at this time. The soils covering 

the broad plateau surfaces in the Nez Perce region and streaming down 

their steep bordering escarpments are similar to, in fact practically 

identical with, the soils about Pullman, Washington, described in the 

report just referred to. Throughout the lava-covered portions of 

Oregon, Washington, and Idaho and the bordering uplands, composed 

of older terranes, thesoils have resulted from the disintegration and 

decay of the underlying rocks, and in genenal have been removed but 

short distances, if at all, from their original positions. This conclusion 

is sustained by the fact that when the sw·face material is traced downward it is found to change, frequently by_ insensible gradations, into 

the underlying and still solid rock~ also by comparing the chemical 

composition of the soil and subsoil with that of the unaltered rocks 

beneath, and by noting the surface changes in passing from one geologic formation to another. In traveling from the lava plateaus to the 

adjacent uplands of older rocks, such aH limestone, granite, diorite, 

schist, etc., in the foothills of the Bitterroot Mountains, an immediate 

change in the character of the soil forces itself on one's attention. 

Above the lava the soil is fine and of a dark color, owing, principally, 

to the presence of organic matter, while the subsoil, equally fine in 

texture, is always <Jf a dull yellow or a brownish yellow color, and is 

characteristically without pebbles or sand grains visible to the unaided 

eye, while the soils on the older rocks are usually light colored and 

contain sand, angular fragments of rocks, and minerals the nature of 

which can readily be determined and which corresponds with that of 

the underlying rocks. The chemical composition of these two divisions 

of residual soils shows marked differences, in harmony with the obvious 

fact that the soils of the lava plateaus are more productive than those 

of the older formations. 

Compared with the older rocks adjacent to it, the greater rapidity 

with which the Columbia River lava breaks down and changes its 

physical characteristics is shown by the increased fineness and far more 

complete decay of the residual material produced. This is the more 

striking when it is remembered that the region composed of the older 

terranes above the level of the last sheet of lava has been much longer 

exposed to the influences which produce weathering than the more 

thoroughly decayed surface of the lava. That this difference is not 

due to differences of slope or of exposure-the surface of the lava 

being frequently nearly :fiat, while the surface slopes of the older 

terranes are more generally inclined, thus favoring the removal of 

small particles and resulting in a concentration of the larger fragments-is evident from the fact that the older land has a great variety 

of surface slopes and that on all of them the debris is much less thoroughly decomposed than on the lava plateaus or even on the steep 

escarpments forming the walls of the canyons excavated in the lava. 

The fact that the soil on the lava plateaus is. not mainly a dust deposit 
44 GEOLOGY, JiJTO., OF NEZ PERCE CO., IDAHO,..:_PART T [No. 53. 

brought frotn a distance by the wind, as.its fineness might indicate and 

as has been suggested by certain careful observers, is clearly shown 

by the abrupt change, just referred to, observable in the surface 

material on passing from the lava to the bordering upland and particularly on visiting the steptoes which rise in isolated positions through the 

lava. On Steptoe and Kamiah buttes in Washington, on Cottonwood 

Butte in Idaho, and on other similar island-like areas, orsteptoes, of preTertiary terranes rising through the Columbia River lava there is an 

abrupt and frequently conspicuom; change between the soil of the 

buttes and that of the surrounding plateau. The soils on the various 

steptoes also differ from one another, but all contain fragments of the 

underlying rocks. These observations are evidently not in harmony 

with the suggestion that the soil of the wheat lands has been brought 

from a distance by the wind. 

The great importance of the wonderfully rich soil on what may be 

termed the wheat lands of the region under consideration is sufficient 

excuse for repeating certain observations concerning it, which were 

published in the report already cited. In the following table there is 

given the results of analyses of a sample o£ basalt, a representative 

of the Columbia River lava, collected at Wallawalla, Washington, and 

o£ the subsoil and soil resting on the same formntion at Dayton, Washington. The subsoil is from a depth of 30 feet, and the soil was collected in a wheat field at a depth of 2 feet below the surface. Each of 

these samples is characteristic o£ the material from which it was taken 

over a wide extent of country. 

Analyses of basalt, snbsoil, and sml from TVallawalla and Dayton, TVashington 

[George P. Merrill, analyst.] 

Constituent. i Basalt. Subsoil. I Soil. 

-------- ------~-,-

Pe1' cent. Pe1· cent. Per cent. Silica (Si02) •••••••••• ___ • __ .•• _. ______ •••••••••••••••••••••••••••••••••• 47.35 65.89 63.58 

~~r~;r~~~:~:~ : ~ ~: ~-:~:~~~~:~~:~::~~~ ~~:~:~:~~~~~~P ::; ::~ ~:; Soda (N~O).. ...... .. .. . . .. . . . . . . . . . .. .... . ... ..... ... ... ...... .. ... . ... 2.55 2.08 2. 02 

Potash ( K20)... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . . . . . . . . . 1. 33 2. 36 2. 27 Loss on ignition (principally organic matter)' . . . . . . . . . . . . . . . . . . . . . . . . . . . 95 2. 60 4. 37 

99.33J~ ------------------------------------------~~----~ 

Total .................................... _ ......... _ ............. .. 99.26 

In reference to these analyses, Merrill says: 

All of the material analyzed was first dried at 100° C. The analyses are not as 

detailed as I would like to make, but are all that the limited time permits. Perhaps 

the most striking fact in the analyses is the similarity in composition between the 

surface soil and that from a depth of 30 feet; almost the only essential difference 

being, apparently, the larger percentage of volatile matter of the surface soil. Not 

having as yet separated the iron and alumina, I am unable to account for the apparent loss of these constituents shown. From previous analyses I am led to suspect 

that the iron oxides have been very largely removed. I am unable as yet to account 

for the apparent increase in potash in the decomposed material. It is possible, 

though hardly probable, that this is due to errors in analysis. 
RUSSELl,.) SOILS. 45 

The close similarity between the composition of the soil and subsoil and of the rock which occurs beneath them is instructive and 

sustains the conclusion that the surface material has resulted from the 

breaking down of basalt. In the formation of residual soils the more 

soluble constituents are removed in solution by percolating water, and 

the less soluble substances are left as a residuum. The soil and subsoil 

should therefore contain an increased percentage of the less soluble 

substances in the original rock~ such as silica and alumina, and a 

smaller percentage of the more readily soluble substances, such as soda, 

potash, lime, etc. The foregoing analyses are essentially in harmony 

with this general principle~ with the exception of the potash and soda. 

In the case of the potash there is an increase in the decomposed material above the amount present in the parent rock~ while the percentage 

of soda is nearly the same. This result is so surprising that I fear more 

analyses should be made before accepting it as final, 1 but it is perhaps 

not out of place to suggest a way in which potash and soda may have 

been added to the soil. 

Over· a large portion of the United States to the west of the Mississippi there have been showers of volcanic dust in recent times. An 

analysis of some of this material which fell in Nez Perce County has 

already been given (p. 34), which shows that it carries 2.58 per cent of 

potash (K20) and 5.08 per cent of soda (Na20). This material falling 

- on the surface of the plateaus would in most situations not be washed 

away, but would form an addition to the soil. How many showers of 

volcanic dust have occurred since the last sheet of Columbia River lava 

was poured out is unknown; but as such showers occurred during the 

eruption of the lava, and also at a recent period, it is reasonable to 

suppose that they took place in the interval referred to. The material 

thus added to the residual soils would be on its upper surface, although, 

judging by present conditions, when in general the plateaus are without surface drainage, there would be a transfer of soluble material by 

percolation from the surface downward. If there has been a notable 

1 In Bulletin No.9 of the agricultural experiment station at Moscow, Idaho, by Prof. Charles W. 

McCurdy, and in Bulletin No. 13 of the agricultural experiment station at Pullman, Washington, by 

Prof. Elton Fulmer and Prof. C. C. Fletcher, a large number of soil analyses are given, and of those the 

samples for which came from the region occupied by the Columbia River lava, only one contains 

potash in excess of 1 per cent, while the average is about one-half of 1 per eent. The exception 

referred to is in the case of the subsoil from near the experiment station at Moscow, analyzed by 

McCurdy, which is reported to contain 1.83 per cent of potash. The soil at the same locality contained but 0.59 per cent of potash. This analysis is vitiated, however, for our present purpose, as 

"sand and silicates" are reported present to the extent of 73.77 per cent; what is included under the 

term silicates is questionable. In a large number of analyses of the soil~ of Washington by Fulmer 

and Fletcher, in which there seems to be no ambiguity of the nature just referred to, the potash 

reported is always considerably less than 1 per cent. The geologic relations of the soils analyzed 

is not always stated, but a number of these are certainly from localities which are underlain by the 

-columbia River lava. In a summary, in reference to the presence of lime, phosphoric acid, and 

potash in the soils of Washington, embracing the results of 45 analyses, the maximum, minimum, 

and mean percentage for potash are 0.6428, 0.0354, and 0.3049, respectively. There is thus a serious 

discrepancy between the analyses just cited and those by Merrill given on page 44, in reference to the 

percentage of potash in the soils of the Columbia River lava region, which will have to be diminished 

before the discussion of the origin of the soils from a chemical standpoint can satisfactorily be continued. 
46 G EO LOGY, ETC. , OF NEZ PERCE CO. , IDAHO. -pART I. [No. 53. 

addition of volcanic dust to the surface of the residual soils on the 

lava, analysis may reasonably be expected to show a greater percentage of potash in the soil than in the subsoil, but this fmpposition is not 

sustained by the chemical evidence available. Again, the beds of volcanic dust interstratified with the Columbia River lava may have contributed material to the soils formed by their decay and enriched in 

potash. The volcanic dust referred to is of the same physical character as that of which an analysis has been given, and with little doubt is 

of about the same chemical composition. 

A typical illustration of the nature of the soil and subsoil produced 

by the disintegration and decay of basalt is afforded at an excavation 

made for clay at a brickyard in Uniontown. The material there used 

for brick making is the normal subsoil of the wheat lands. It is about 

35 feet thick, but the passage to the solid rock beneath was not 

exposed at the time it was visited. The material is fine in texture, in 

fact is almost without appreciable grains, and is of a uniform brownish yellow eolor, exeept that the upper 4 or 5 feet, as seen in vertical 

walls, is darkened by organic matter. There not only is no evidence 

of stratification, but the material is uniform in eolor, texture, etc., 

from the base of the discolored upper portion to the bottom of the 

exposure, a depth of about 25 feet. The most interesting feature is 

the presence of nearly vertieal but somewhat tortuous tubes, having 

an approximately uniform.diameter of one-fourth inch, which occur at 

intervals of, in general, frmn 4 to (j inches. These tubes ean easily be 

traced in the walls of the excavation for distances of 5 or 6 feet, and 

seem to be continuous from the base of the layer of soil to the bottom 

of the exposure. They are so nearly vertical that the gentle bends or 

irregularities in direetion seldom eause them to depart more than 4 or 

5 inches from a mean position. They do not bifurcate or send off 

branehes, and have no definite walls. They are simply holes in the 

soft, clay-like material traversed by them. On their interiors there 

are slight irregularith~s, such as might be produced by the downward 

flow of drops or small clots of the material whieh they traverse, which 

have hardened so as to form slight elevations with well-defined and 

rounded lower margins. 

A tubular structure like that just deseribed is· somewhat exeeptional 

in the residual soils on th~ Columbia River lava, but it has been 

observed in a few other instances. More eommonly mueh smaller 

tubes are present, similar in every way, exeept, perhaps, in the eharacter of their bounding surfaees, with diameters rather uniformly 

about one-tenth of an ineh. These small tubes were not observed in 

the subsoil at Uniontown, but in many other instanees, in material of 

the same charaeter, they were so numerous that a eubie inch of the 

subsoil could not be examined without finding several of them. 

The origin of either class of these tubes is unknown, but it is obvious 

that .they serve an important funetion in permitting the ready absorp-
RUSSELL.] SOILS. 47 

tion of rain water falling on the wheat lands, and show, in fact, 

why there seldom is any evidence of surface ·rills. Slopes of fully 25 

to 30 degrees, composed of soft soil in either its natural condition or 

plowed, harrowed, and left unsown for a year, a common cu~tom, 

show no rill marks such as are usual in many regions, especially where 

the soil is an impervious clay .. The open tubes in the subsoil insure a 

prompt and most effective underdrainage and aeration, and the soil in 

which it is presumed the tubes have been obliterated, through movements in the material, due to the beating of rain, the growth of plants, 

frost, etc., is so exceedingly :fine-less than 2 per cent of the grains 

exceeding one-tenth of a millimeter in diameter 1-that all of the water 

falling on it is at once absorbed. While the rate of evaporation is 

high, the soil does not become charged with alkaline salts, as is so 

commonly the case in regions of small rainfall-the water from below 

being raised to the surface by capillary attraction, and the salts it 

contains being precipitated as evaporation progresses-but on account 

of the prompt subdrainage by percolation, where rain occurs, the 

material brought to the surface during dry seas0ns is redistributed. 

The only localities on the plateaus underlain by Columbia River lava 

where alkaline salts are concentrated at the surface are in low basins 

where an excess of organic matter has rendered the soil impervious; 

but these places are of rare occurrence and of small area. 

On the precipitous walls of the numerous canyons cut into the 

Columbia River lava and the older formation beneath, there is usually 

a mantle of soil not only on the ledges and terraces but on the steep 

talus slopes and irregular surfaces of landslides. These soils, althoug];t 

usually composed largely of disintegrated and decayed basalt, have in 

many instances received important additions of material derived from 

the layers of volcanic dust, sand, gravel, etc., interbedded with the 

lava, and at horizons below the base of the lava sheets they contain 

also the debris of the pre-Tertiary terranes. The sides of the canyons 

are nearly everywhere clothed with bunch grass, and in spite of their 

steepness they afford excellent pasturage~ The corpmingling of debris 

on the steep plateau margins has led to the making of a soil which in 

some instances seems to be even better adapted to agriculture and horticulture than the more uniform soils of the plateau surfaces. This 

may be due in part, however, to more favorable exposure to the sun, 

but it certainly is influenced by the escape of water from the cut edges 

of porous layers in the lava formation. 

In the case of the terranes of older date than the Columbia River 

lava, surface disintegration seems to be in excess of rock decay, as the 

soils are usually charged with rock fragments, while on the lava 

plateaus the reverse is true, and fragments of rock large enough 

t See mechanical analysis of a sample of wheat-land soil from Pullman, Washington, by Milton 

Whitney: Water-Supply and Irrigation Paper U. S. Geol. Survey No.4 (1897), p. 59. 
48 GEOLOGY, ETC., OF NEZ PERCE CO., IDAHO.-PART I. [No. 53. 

to be distinguished by the unaided eye are of rare occurrence, even 

at depths of from 20 to perhaps 75 or more feet below the surface. 

The lava is plainly more prone to decay and to crumble under the 

influence of percolating water than is the granite, diorite, gneiss, 

schist, limestones, etc., of the older formations. The marked tendency 

of the lava to decompose in this manner and to yield a rich soil of 

such a physical character that it absorbs and retains all of the rain 

which falls on it and is easily plowed, insures a long period of prosperity for this '"Inland Empire," as the grain-growing region of 

eastern Oregon and Washington and neighboring portions of Idaho is 

sometimes termed. 

The peculiar and interesting surface relief of the lava plateaus will 

be discussed further on, in connection with other features of the physiography of the region under consideration. 

TRANSPORTED SOILS. 

In addition to the residual soils in the Nez Perce region, which 

occupy probably ninety-nine one-hundredths of the surface, there are 

small detached areas, principally along the margins of the larger 

streams, where the soil is composed of silt, sand, and gravel deposited 

by the streams during high-water stages. These transported soils, in 

which the debris from an extensive series of cliffs is commingled, contain a great variety of rock fragments, usually well rounded and 

assorted and deposited in an orderly sequence with reference to size 

and specific gravity. At present this material forms flood plains 

which are inundated. during high-water stages, or represents ancient 

flood plains which have been abandoned owing to the deepening of 

strea1n channels. In excavations in these depoBits the changes to be 

observed as the depth below the surface increases, are such as are 

normal to similar accumulations the world over, and result from the 

manner in which the mnterial was laid down. As a rule, the surface 

of a flood plain is composed of fine silt or fine sand; beneath this, 

at a depth usually varying .from 3 to 4 feet, there is a change to 

gravel, and at lower levels pebb]es, and even cobblestones and rounded 

water-worn bowlders, ma5r be found. The reason for this arrangement is that the material in the flood plains of streams is continually 

being worked over by the streams themselves and becomes assorted. 

Where streams are depositing their loads they flow in curves. cut 

away their banks on the outer side, and make deposits on the inner 

side of each bend. The material cut away at one curve is carried 

downstream and much of it is redeposited on the inner side of the 

next curve below. This process is clearly illustrated along the lower 

course of Clearwater River, and can be observed in almost any brook 

or rill. The succession of finer and finer material from the bottom 

of a flood-plain deposit to the surface is due to the fact that the lower 
RUSSELL.] SOILS. 49 

portion is laid down in the central part of a stream, where the current 

is swift, and as the stream migrates finer and finer material is deposited 

upon it. The last layer is spread out during inundation. It also 

receives dust deposited from the air, is usually of fine quality, and 

forms a remarkably rich soil. 1 

Flood plains of the nature of those just described occur along Clearwater River, and are also well illustrated near Kamiah, Lewiston, 

Spalding, and Lapwai. They are built on deposits of the same nature, 

and in a few other instances, along the larger streams, there are small, 

nearly flat areas of a similar character; but in general the canyons are 

too narrow to permit the deposition of much of the material that is 

being transported through them. The streams in general are engaged 

in deepening their channels; they have not reached the stage of broad--

ening their valleys and spreading out extensive flood plains. It is only 

where special conditions exist-for instance, the presence of soft beds 

at· the level of the streams, as at Kamiah, or where a depression of the 

rocks has caused a widening of the valleys, as along Clearwater River 

near Lewiston-that flood plains of sufficient width to be of economic 

importance are to be found. The fact that the flat lands referred to 

are due to stream deposition is cle3,rly shown in numerous instances 

by the presence of abandoned stream channels, some of which are in 

the condition of lakelets or sloughs. 

Flood-plain deposits form the lands now under cultivation in Asotin 

Canyon, and there, as elsewhere, they are in danger of being removed 

by the same agency that built them. This obvious truth should be 

borne in mind by all who seek to cultivate the narrow flood plain in 

that canyon, particularly where the small, flat areas of rich land favorably situated for irrigation have tempted people to build their homes 

within reach of the creek when swollen by heavy rains._ The canyon 

bears evidence of having recently been swept by floods caused by torrential rains, commonly termed cloudbursts. Similar high-water stages 

are sure to recur, and proper precautions should be taken to insure 

the safety of life, even if the risks to grain fields and orchards are 

accepted. 

As will be shown further on, the rivers of the Nez Perce region first 

cut their canyons to about their present depths, then filled them with 

gravel to a depth of 350 feet, and have since removed the greater part 

of the material formerly deposited. In this process of reexcavation, 

in a few instances portions of old flood plains have been left, and they 

furnish examples of transported soils at a considerable elevation above 

the present streams. Clarkston is built on an alluvial deposit of this 

nature which has a sloping surface, owing to the fact that it is on the 

I This and other important changes now being made by streams in the surface features of the earth 

are discussed somewhat fully in Rivers of North America, by Israel C. Russell, published by Putnam's 

Sons, New York, 1898. 

IRR 53-01--4 
50 GEOLOGY, ETC., OF NEZ PERCE CO., ID.A.HO.-P.A.RT I. [No. 53. 

concave side of a curve in Snake River, and the stream, in deepening 

its channel, migrated slowly eastward. In this instance there is a surface layer of fine silt-like materiaL about 5 or 6 feet thick, resting on 

coarse gravel and cobblestones. The surface layer furnishes a rich 

soil, and the open texture of the gravel beneath insures underdrainage, which prevents the concentration of alkali at the surface. This 

fortunate arrangement is favorable to the sanitary conditions, particularly as the water supply is brought from a distance. 

Other.areas of transported soil similar to that at Clarkston occur 

on the opposite side of Snake River and form the surface of the plateau 

on which the newer or upper portion of Lewiston is situated. Fine 

sections of flood-plain deposits are exposed in the margins of this 

plateau, especially where grades have been made along the streets 

connecting the upper with the lower portions of the city. Similar 

deposits occur near Alpowa, also in the canyon of Salmon River, near 

its mouth, and, of limited extent, along the borders of many small 

streams or where such streams enter the large canyons. 

In connection with the examples of soils just cited, in whieh material has been brought from a distance, reference will be made to at 

least one somewhat conspicuous 'instance of wind transportation. 

Snake River just above Lewiston deposits on its right bank a considerable quantity of fine, white, micaceous sand or silt. 1 During lowwater stages this material is exposed to the air, becomes dry, and is 

blown eastward by the prevailing winds. It is carried up the canyon 

wall, which there is low, over the sloping margin of the Lewiston 

Plateau for a distance of 2 or 3 miles, and is deposited largely in 

dunes, although much of it is widely distributed. 

Some movement of the surface of the soil on even the generally level 

plateaus must result from the action of the wind, but in a state of 

nature, when the present extensive grain fields were prairies, the soil 

was held by plant roots and was sheltered by the vegetation growing 

1 Many of the sand bars along the borders of the larger streams in the Nez Perce region are of an 

exceptional character. The banks of the rivers are, as a rule, precipitous, so that gravel and sand 

can not be rolled along them under the influence of the current, but exceedingly find sand, particularly flakes of mica, are carried in suspension by the swift water, and are deposited in eddies where 

the force of the current is slackened. Conspicuous bars or spits of white sand or silt are in certain 

instances formed in this manner, and are attached to the shore at their downstream extremities, 

while their upper and usually rounded distal ends are free and are surrounded by water several 

feet deep. The explanation of the origin of these peculiar bars is that the fine material of which 

they are composed was brought down the streams in suspension by the strong central current, and 

when a portion of the water was deflected by changes in the direction of the shore line, an eddy was 

produced in which the water flowed upstream along the side of the channel. When the current 

slackened, on being deflected in this manner, the material in suspension waR deposited and shaped 

into a bar or spit, with curved margins, the free end pointing upstream. A photograph of one of 

these spits of fine, white, micaceous silt is reproduced as Pl. VI, A. 

The fineness and lightness of the silt form,ing these bars and the fact that it can be transported in 

suspension may be demonstrated by pushing a mass of it into the water and observing that a considerable portion of it will float, often being carried a long distance by even a gentle current before it 

finally sinks. Under natural conditions the bars are sometimes cut away during low-water stages, 

and floating silt can be seen extending from them in all directions on its way down the stream. 

The material will float, however, only when its upper surface is dry, and in that condition it is perhaps buoyed up by air vesicles; but when wet it settles slowly, and in a rapid stream it will be <"arried long distances before finding a place sheltered from the current in which it can rest. 
RUSSELl,.] PHYSIOGRAPHY. 51 

on them, so that the transfer, through this agency, of material from 

one locality to another must have been small in amount. At present, 

when so much of the fine soil is plowed and left for a season without 

being sown, and roads have been established, great quantities of dust 

are carried in the air during the summer season. 

SUMMARY. 

The deep soils and subsoils on the lava plateaus and also on the terraces formed by the projection of resistant layers in canyon walls 

where they are bordered by the Columbia River lava, have resulted 

from the disintegration and decay of the lava rock, and remain in their 

original positions or have been removed but "short distances through 

the influence of beating rain, changes of temperature, the pull of 

gravity, etc. This widely extended surface sheet of decomposed rock 

furnishes a typical illustration of residual soil. While it has been 

formed principally from the lava rock, it contains some volcanic dust 

which was deposited on it and has been incorporated in it. This dust 

is richer in potash and soda than is the lava rock, and serves as a fertilizer. On the walls of canyons where terraces occur, and, what is 

equally common, where landslides have found terrace-like shelves, 

frequently with undrained basins on their surfaces, there is in many 

cases an admixture of volcanic dust, lapilli, gravel, sand, clay, etc., 

derived from layers of these substances which are interbedded with 

the lava sheets through which the canyons have been excavated. In a 

more critical classification than is here attempted these soils might be 

considered by themselves as representing colluvial deposits. 

The soils on the foothills of the Bitterroot ·Mountains, and generally 

throughout the .mountains as well as on the steptoes rising through 

the Columbia River lava, are also of sedentary origin, and have resulted 

from the disintegration and decay of the rocks on which they rest. 

The rocks forming these uplands yield to the influences of the atmosphere less readily than does the basalt of the adjacent plateaus, and furnish a soil that is less homogeneous and less thoroughly disintegrated. 

No soils of glacial origin occur in the region represented on the map 

forming Pl. II. Transported soils occur in areas of limited extent 

along the rivers, and are principally the deposits of the rivers in recent 

times, although a few remnants of ancient flood plains still remain. 

PHYSIOGRAPHY. 

RELATION OF SURFACE RELIEF TO GEOLOGIC STRUCTURE AND 

CLIMATE. 

As is well understood, the present diversity in the relief of all land 

areas is in the main the net result of two series of changes, or of the 

action of two agencies which are in opposition to each other. • One of 

these embraces the movements in the earth's crust by which rocks are 
52 G EO LOGY, ETO. , OF NEZ PEROE 00. , IDAHO. -PART I. [No. 53. 

raised above sea level, or, if originally. above that horizon, are folded, 

tilted, etc. ; while the other includes the denuding action of the atmosphere and of water, and has for its object, so to speak, the carving 

away of all land areas to sea level. In countries where the rainfall is 

small the changes in relief produced by upheaval, or, more definitely, 

the surface irregularities resulting from the folding and ·breaking 

(faulting) of the rocks and the tilting of areas of greater or less size 

bounded by folds or faults, remain prominent for a long period of time, 

and frequently furnish the most conspicuous features in the topography; 

while in humid lands, particularly where the climate is warm as well 

as humid and vegetation is luxuriant, rock decay is rapid, and the 

most conspicuous featrlres in the relief of the land are likely to be 

such as result from denudation. Between these two extremes there 

are all degrees of gradation. 

In the Nez Perce region th_e rainfall, as already stated, is small, but 

streams rising in the ·mountains to the eastward, where precipitation 

is heavy, flow across it, and conspicuous features in the relief are due 

both to movements in the underlying rocks and to stream erosion. 

For these reasons a knowledge of the structure of the rocks and of 

the manner in which streams have excavated channels in them is essential in order to understand the significance of the larger topographic 

features of the surface as it exists to-day. In fact, nearly the entir~ 

history of a region needs to be considered in order to be able fully to 

interpret its present relief. · 

ORIGINAL LAVA PLATEAU. 

So far as the Nez Perce region is concerned, there seems to have 

been no conspicuous movements in the earth's crust during the time 

the Columbia River lava was being poured out. In other words, so 

far as known there are no unconformities in the lava sheets due to 

movements in one portion before the next succeeding sheet was spread' 

out above it, although time intervals between successive sheets are in 

some instances recorded by sedimentary and other deposits. The 

edges of the lava sheets exposed in canyon walls are always essentially 

parallel with one another. 1 

A starting point in the study of the present relief is thus furnished 

by the condition of the surface at the time the last sheet of lava was 

spread over it. At the tin1e referred to Nez Perce County and the country adjacent to the foothills of the Bitterroot l\!Iountains was a featureless plain, diversified only by a few island-like peaks that rose through 

the lava. This plain, we are justifi~d in assuming, was similar to the 

surfaces of many lava sheets of recent date which have been studied, 

and presented a rough and moderately uneven expanse of black, scotAn exception to this statement will perhaps be found in the northwestern portion of the Clarkston 

Plateau and in the region drained by Alpowa Creek. 
RUSSELL.) PHYSIOGRAPHY .. 53 

riaceous, slag-like rock. That it was absolutely level is not to be supposed, since lava sheets may continue to :flow after their surfaces have 

cooled and hardened, and the surface crust is frequently broken and 

perhaps forced up into ridges and hillocks. In a thick lava sheet shrinkage occurs after its surface has hardened, and the surface is deformed 

and frequently forced up into ridges or dome-like forms which crack 

open along their tops. For these and other reasons it is to be presumed 

that while the surface of the last sheet of Columbia River lava formed 

a plain without conspicuous inequalities, it was far from being smooth 

and even. 

If we knew the elevation of the surface of the last sheet of lava as 

it existed before being deformed by movements in the earth's crust, 

much assistance would be gained in tracing th~ history of the present 

highly diversified 'topography. While a definite answer to this question can not at present be given, certain facts enable one to reach an 

approximate determination as to the original level of the lava plateau. 

As already explained, the Columbia River lava was poured out in a 

molten condition, in a series of vast inundations, over a deeply eroded 

land surface. The contact of the lava with the formations on which it 

rests is always unconformable, and between the two there are no massive sediments. As the pile of lava sheets is in places more than 4,000 

feet thick, it follows that the last sheet spread out must have had at 

least that elevation above the sea, unless the old land surface, like the 

region about the Dead Sea and the bottom of Death Valley at the present day, was below sea level, which is improbable. The only other 

escape from the conclusion just stated seems to be that movements producing a depression occurred during the time the lava sheets were being 

formed. If such a downward movement did occur, it was evidently 

not sufficient to carry the surface below sea level, for no marine sediments have been discovered between the lava sheets. Unconformities 

due to a folding or tilting of the earlier formed lava sheets before the 

succeeding sheets were spread out have not bP.en discovered in the 

eastern portion of the formation under consideration, although such 

unconformities are known in the Cascade region. Whether the movements which caused the unconformity referred to influenced the eastern portion of the lava sheets can not at present be definitely stated. 

From these considerations it might reasonably be expected that since 

the lava sheets in eastern vV as.hington and Oregon and the adjacent' 

. portion of Idaho are still horizontal, the surface of the plateaus thus 

formed should have an elevation of at least 4,000 feet above the sea. 

Instead, however, we find in numerous instances that the general 

elevation of the plateaus underlain by essentially horizontal lava sheets 

is between 3,000 and 3,300 feet. This difference, approximately 1,000 

feet, between the present elevation of ~he locally undisturbed plateaus 

and what is assumed to have been their original position can be 
54 GEOLOGY, ETC., OF NEZ PERCE CO., IDABO,-PART I. [No. 53. 

ascribed in part, perhaps, to erosion, but the amount of erosion is 

certainly small, and in places, as will be shown further on, it is nil, for 

the reason that portions of the scoriaceous surface of the last lava 

sheet have been proteeted by sedimentary beds laid down upon it, and 

these portiuns of the lava sheet have essentially the same elevation as 

the deeply weathered portions of the same sheet. A warrantable inference seems to be that there has been a general subsidence of the easttern portion of the Columbia River lava region referred to of at least 

1,000 feet, whieh did not disturb the horizontaHty of the strata. This 

subsidence may have gone on during the time the lava was being 

·extruded, or may have occurred in part or wholly since the last sheet 

of lava was spread out. 1 

LEADING FEATURES IN THE RELIEF DUE TO MOVEMENTS IN 

THE EARTH'S CRUST. 

Whatever may have been the amount of the broad regional movements in the Nez Perce region, the faet that large areas have not been 

deformed but still remain essentially level and are underlain by horizontally bedded lava sheets, permits of reaching interesting conclusions 

1 The region occupied by the Columbia River lava is of special interest in reference to the study of 

the manner in which the earth's crust has been deformed, as it is unique and exceptional in the geologic history of North America. At the close of the eruptions which furnished the lava there 

existed in that region an essentially horizontal plateau 200,000 square miles or more in area, which 

in itself is exceptional in the history of topographic forms; but more than this, the plateau was 

produced by the outpouring of lava, and was built up, layer by layer, on a land surface. The plateau 

has since been variously deformed, but mostly in a broad way, and the nature of the movements can 

readily be determined. Moreover, the region is usually bare of trees, and the changes that have 

been made by erosion are sharply defined and easy to separate from those resulting from movements 

in the rocks. In the studies of isostasy and diastrophism that may be carried on there, the influence 

of the vast weight of the lava poured out at the surface, and also the withdrawal of a corresponding 

volume of liquid rock from beneath the surface, demand attention. The importance of the field as 

furnishing a test of isostasy is shown by the fact that the volume of the Columbia River lava is in 

the neighborhood of 50,000 to 60,000 cubic miles; its weight is about 160 pounds to the cubic foot; 

where the lava is 4,000 feet thick the pressure on the underlying rocks is in the neighborhood of 320 

tons to the square foot. It is reasonable to suppose that the effect of the extrusion of so vast a volume of lava would be to cause a regional depression of the earth's crust. That this result was produced is shown by the fact that over the central part of the lava-covered country in Oregon and 

Washington the surface is now but a few hundred feet above sea level. At Pasco, Washington, the 

elevation is 386 feet, and over a large area of the surrounding lava plain the elevation is certainly 

less than 500 feet. The subsidence that has occurred in this region is not less than 3,500 feet, and 

probably exceeds that measure by at least 1,000 feet. This downward movement began, perhaps, at 

an early stage in the extrusion of the lava, and continued during the time the successive sheets were 

being spread out; but a part of the deformation which the lava has experienced, and possibly a part 

of the general subsidence of the central portion, has occurred since the extrusion of the last lava 

sheet. Other portions of the lava formation, of even greater extent than the central depressed 

region, have been upraised. In the Cascade Mountains the lava sheets, with a gentle eastward dip 

toward the depressed region, which includes the Great Plains of the Columbia, have an elevation of 

from 7,000 to 7,500 feet. The lava plateaus in eastern Oregon have ari elevation of from 5,000 to 7,000 

feet (Lindgren), and the general inclination of the beds, as in eastern Washington, is westward. 

Thus portions of both the eastern and western border of the lava-covered country have been raised 

from 3,000 to 3,500 feet, and the central part has been depressed by about the same amount from what 

would have been the surface level of the lava-covered country in case there was no subsidence during 

the extrusion of the lava. These movements have been in large part of the nature of a tilting of 

broad blocks of the lava, bounded by monoclinal folds and faults. 

While the foregoing statements serve to indicate the general nature of the problems presented by 

the Columbia River lava, a detailed study will probably show that there have been extensive movements in the rocks during the time the lava was being poured out. For example, as has been shown 

by George Otis Smith, on the east side of the Cascade Mountains near Clealum, there is a strongly 

pronounced unconformity between a lower and an upper member of the lava formation, which 

proves that the lower portion of the pile of lava sheets was sharply folded and deeply eroded before 

the nearly horizontal and later sheets were poured out. 
RUSSELL.) PHYSIOGRAPHY. 55 

in reference to the movements that have affected adjacent areas where 

the strata are no longer horizontal. About the foothills of the Bitterroot Mountains there are many small valleys which still retain the 

level floors given them by the last inundation of Columbia River lava. 

These floors are horizontal, and beneath their coverings of alluvium 

their scoriaceous surfaces are to be seen. In several such instances 

the elevation of the lava surface is, by aneroid measurement, about 

3,000 feet above the sea. This is also the general elevation of the 

Uniontown Plateau, to the north of Lewiston, beneath which the lava 

sheets are horizontal. The Uniontown Plateau, although its boundaries, except on the south, have not been defined, is certainly several 

hundred square miles in area, and extends, without any perceptible 

structural change in the rocks, eastward to the foothills of the Bitterroot Mountains, and on the northwest is believed to merge, without 

any conspicuous change, into the still more extensive region of similar 

character known as the Palouse country, where the lava sheets are also 

horizontal, or possibly have a slight dip to the westward, and where 

the general surface elevation is also about 3,000 feet. This extensive 

region of essentially horizontal lava sheets has evidently not undergone local deformation; and where adjaeent areas beneath which the 

strata are inclined are belmv its level, it seems safe to conclude that 

they have been depressed; a,nd where similar areas stand above the 

assumed datum plane, the conelusion is that they have been locally 

upraised. More definite reasons for assuming that the Uniontown 

Plateau may be taken as a datum plane for determining the amount of 

differential movements that has taken place in the adjacent plateaus, 

will, the writer thinks, be recognized in the somewhat detailed record 

of facts which follows. 

The lava-covered portion of the region represented on the map 

forming· Pl. II is divided naturally into six more or less well-defined 

areas of primary rank, which, when inciined, illustrate the nature of 

the movements which have affected the rocks beneath them. These 

areas are the Uniontown Plateau and the Camas and Kamiah prairies, 

beneath which the lava beds are horizontal, and the Blue Hills, the 

Lewiston and Clarkston plateaus, and Craig Mountain, beneath which 

the lava beds areinclined. 

Uniontown Plateatt.-Rising from the north or right bank of Clearwater River, throughout the lower 25 or 30 miles of its course and 

continuing westward beyond Lewiston, is a bold escarpment which in 

its central part has a height of about 2,000 feet. This is one of the 

most pronounced topographic features in Nez Perce County, and 

although in some respects it resembles the walls of the deeper portions 

of several of the great canyons in the same region, it is plainly of a 

different nature and origin. For example, there is but one escarpment, 

not two facing each other, as in the case of a canyon, except in a 
56 GEOLOGY, ETC., OF NEZ PERCE CO., IDAHO,-PART I. [No. 53. 

minor way, as will be exp~ained later. Then, too, the strata in the 

Clearwater escarpment, as.it is convenient to term it, are for the most 

part not the edges of horizontal strata, as is commonly the case in 

the neighboring canyon walls, but are-formed of inclined bedA which 

dip southward. In the eentral and highest portion of the escarpment 

this southward dip is at a high angle, frequently 40 or 50 degrees, but 

near its extremities the inclination is more gentle. On climbing the 

escarpment it will be found to be the border of the nearly level Uniontown Plateau. 

At the base of the Clearwater. escarpment, and in general about 1,500 

feet lower, are the Clarkston and Lewiston plateaus, described further 

on. The lava sheets, and certain sedimentary beds interstratified with 

them, which underlie the Uniontown Plateau, are horizontal, or essentially so; but in the Clearwater escarpment they bend abruptly downward, and at its base they flatten out beneath the Clarkston and Lewiston 

plateaus-that is, the escarpment is a monoclinal fold, which begins at 

the east, in the neighborhood of Agatha, as a gentle flexure, and 

increases both in height and in the inclination of the layers as one follows it westward, until near Lewiston its height is about 2,000 feet 

and the dip of the beds from 40 to 50 degrees. Still farther west, along 

N. 

Uniontown Plateau 

o~~==·~oo~o~~szooornn VERTICAL SCALE OC=;""H~OR:C::IZ===ON~~A~L~5CAL~t~ MILE5 

FIG. 1.-North-south section through the Uniontown Plateau, Clearwater escarpment, and Lewiston 

Plateau. 

the north side of Snake River for 3 or 4 miles below Lewiston, the fold 

becomes a break or fault. How this fault terminates at the west is 

not known, but such facts as are in hand suggest that near Alpowa it 

passes again into a fold, which continues westward along the creek of 

the same name. The entire length of the fold, including the 2 or 3 

miles where it is broken, is about 50 miles. 

A peculiar and interesting fact in conneetion with the monoclinal 

fold just described is that Clearwater River flows directly along it for 

a distanee of about 35 miles, and has excavated a canyon in it. The 

relation of the river to the fold is illustrated in fig. 1, which may be 

considered a generalized north-south section about 6 miles east of 

Lewiston. 

At the locality referred to, and for a distance of about 10 miles 

upstream, the southward dip of the rocks forming the south side of 

Clearwatm: Valley is well shown. Again, to the west of Lewiston 
RUSSELl,.) PHYSIOGRAPHY. 57 

Snake River enters this same monoclinal fold where it changes to a 

fault, and, bending westward at almost a right angle, continues in 

nearly the same course that the Clearwater has in the portion referred 

to above. From the abrupt bend made by Snake River just below 

Lewiston to the equally sharp curve made at Alpowa, the river flows 

along the monoelinal fold, in part a fault, which unites the Uniontown 

Plateau with the Clarkston Plateau. On the south side of Snake 

River between Lewiston and Alpowa, the southward dipping rocks 

form a conspicuous precipice facing north, in which a layer of columnar basalt it:l well exposed. The south ward dip referred to may readily 

be seen from any commanding point near Lewiston. A north-south 

section midway between Lewiston and Alpowa would be similar to the 

one shown in fig. 1, but the southward dip on the south side of the 

river would be more pronounced. 

The Uniontown Plateau is underlain all along its southern border, 

and apparently throughout practically its entire area, by horizontal 

sheets of basalt, which include at least one important bed of clay, sand, 

and gravel, at a depth of about 160 feet below the surface. The 

plateau is undulating, owing to strea1n erosion, as will be discussed 

further on, and at severallocalitjes on its southern border deep notches 

have been cut by streams flowing into Clearwater River. 

Clarkston and Lewiston platea'lts.-The country to the south of the 

Clearwater escarpment in the vicinity of Lewiston and Clarkston has 

been depressed about 2,000 feet below the level of the Uniontown 

Plateau, and the strata beneath it are inclined downward toward the 

north. This inclination is slight, however, but it affects the rocks for a 

distance of about 20 1niles, so that its influence becomes conspicuous in 

the larger features of the surface relief. As the displacement producing 

the escarpment referred to dies out to both the east and the west, there 

is also an inclination of the beds beneath the sunken area and adjacent 

to the base of the Clearwater escarpment toward the center, where the 

movement was greatest. This center is at Lewiston-Clarkston, but the 

dip of the beds is too slight to be observed in rock outcrops, being 

only about 1,500 feet in a distance of 20 miles, although it is apparent 

in the surface slopes of the country. 

Thus, the reg~on to the south of the Clearwater escarpment· has the 

form of a trough, with the axis running about north and south. This 

axis determined the general course taken by Snake River from the 

mouth of Grande Ronde River to Lewiston-Clarkston. Other move, 

ment::; also have affected the region. The rocks to the west of Snake 

River have a gentle inclination toward Lewiston-Clarkston over the 

broad area which is cut by the canyons of the various branches of 

Asotin Creek. This nearly level but deeply dissected country has 

been termed the Clarkston Plateau. The town for which it is named, 

however, is in the canyon of Snake River, about 500 feet below the 

general surface of the plateau. 
58 GEOLOGY, ETC., OF NEZ PERCE CO., IDAHO.-PART I. [No. 53. 

On crossing the Clarkston Plateau from its eastern border along 

Snake River toward the southwest, the surface continues to rise until 

the plateau merges into the large dome-shaped uplift known as the 

Blue Hills. In this uplift the lava beds are carried about 2,000 feet 

higher than the surface of the Uniontown Plateau, showing that there 

has been a local uplifting of the lava sheets above their original position. 

The eountry to the east of Snake River, for a distance of about 15 

miles above Lewiston, has a gentle inclination toward that city, but 

it is roughened by stream erosion. This plateau, which has been 

termed the Lewiston Plateau, when crossed in a direction southeast 

from the town for which it is named, rises gently until the base of 

Craig Mountn.in is reached, where there is a steep ascent. The strata 

beneath the plateau correspond in dip with the surface slope of the 

broad areas between the stream-cut canyons, and at the border of Craig 

Mountain they are bent sharply upward. 'rhe latter mountain is 

formed by a monoclinal fold similar to the larger fold which determines the south border of the Uniontown Plateau, as will be described 

more fully further on. 

We,;t East 

LeWJ"ston Platesu 

0 

VERTICAL. SCALE 

FIG. 2.-Section through the Lewiston and Clarkston plateaus. 

The Clarkston and Lewiston plateaus are in reality a single topographic feature, but it is convenient to give them separate ~onsideration, on account of the depth of Snake River Canyon, which has 

been excavated along the axis of the gentle north and south trough 

into whieh the rocks have been bent. Snake River, however, does not 

follow the axis of this trough precisely, but the northeastward slope 

of the rocks away from the Blue Hills extends east of the canyon, as 

can be seen in looking over the region from comma a ding points on 

the hill8 near Waha (Pl. VII), or from the summit of the Clearwater 

escarpment near Lewiston, and as indieated in the section shown in 

fig. 2. In the country on the east side of Snake River Canyon opposite Asotin, the axis of the synclinal trough formed by the junction 

of the strata which rise from it to the east and the west lies about 

2 miles east of the course followed by the river. 

It is important, in reference to the question of obtaining artesian 

water, to note that the surface slope of the broad remnants between 

the streams which have dissected the Lewiston and Clarkston plateaus, 

and also the inclination of the strata beneath the surface, is downward 

toward the towns for whieh the plateaus have been named. 
U. S. GEOLOGICAL SURVEY WA T ER-SUPPLY PAPER NO. !53 PL. VII 

LEWISTON PLATEAU FROM NEAR WA H A. 
RUSSELL.) PHYSIOGRAPHY. 59 

Blue IIills.-Included in part in the area represented on the map 

forming Pl. II are the Blue Hills, or mountains, as they are frequently 

termed, of southeastern Washington. This uplift was visited during 

the reconn.aissance which forms the basis of this report, but the 

observations made give little information in addition to that contained 

in a previous. publication. 1 

The Blue Hills have been elevated since the Columbia River lava of. 

which they are composed was spread out in horizontal sheets. The 

uplift is of the nature of a broad, low dome, which attains an elevation 

of about 5,000 feet above the sea, or 2,000 feet above the level of the 

Uniontown Plateau. The strata which underlie the Clarkston Plateau, 

as has already been stated, rise gently toward the southwest, and pass, 

by insensible gradations, into the more steeply inclined portions of 

the same beds which have been elevated to form the Blue Hills. The 

differential movement which the once horizontal beds have experienced 

between Clarkston and the summit of the Blue Hills is about 4,000 

feet. This change occurs in a distance, in a direct line, of 25 miles, 

but the upward movement at the southwest was sharper than the 

downward movement at the northeast. The strata involved in the 

Blue Hills uplift are inclined away from its summit portion in all 

directions, in essentially the same way that they are inclined to the 

northeast, where they pass into the Clarkston Plateau, but they dip 

somewhat more steeply on the south side than in other directions. 

The pas.sage from the surrounding plateaus into the dome is so gentle 

that the eye can not distinguish where the change begins, but, in general terms, the uplift may be said to be from 50 to 60 miles in diameter 

from east to west, and to measure from 30 to 40 miles along its northsouth axis. On the summit of the uplift the strata are so nearly horizontal that it is impracticable to measure their inclination, and on its 

sides the dip is seldom more than 2 or 3 degrees. If the- uplift had 

not been eroded it would appear as a smooth dome, low in compariRon 

with its width, but streams have sculptured it in a conspicuous manner, 

and its slopes are now trenched by deep canyons. The greatest change 

produced by erosion is on the south side, where Grande Ronde River 

has excavated a canyon comparable in grandeur with the finest portions 

of the neighboring Snake River Canyon. 

Ora1:g 11Imtntain.-This name, although used somewhat indefinitely 

by the inhabitants of the Nez Perce region, will be considered as 

designating an elevation which extends in a northeast-southwest 

direction across the west-central portion of Nez Perce County, from 

the border of Snake River Canyon near W aha to the vicinity of 

Willola on Clearwater River. Viewed from the vicinity of Lewiston, 

the uplift appears to be a long, even-topped ridge, which begins at the 

northeast as a gentle swell and becomes higher and more precipitous 

as the eye follows it toward the southwest. On visiting the mountain, 

1 Water-Supply and Irrigation Paper U.S. Geol. Survey No.4. 
60 GEOLOGY, ETC., OF NEZ PERCE CO., IDAHO.-PART I. [No.53. 

one finds it to be the upraised border of a broad plateau which is 

inclined to the southeast, but which soon flattens and forms the Camas 

and Kamiah prairies. 

The north west border of Craig Mountain is an escarpment of the 

same general character as the one forming the south border of the 

Uniontown Plateau, but it is less pronounced. It is a m~moclinal fold 

which unites the Lewiston Plateau on the northeast with the Camas 

and Kamiah prairies on the southeast. It differs from the Clearwater 

escarpment, principally in the fact that the two plateaus which it unites 

slope away from its longer axis in each direction. A section through 

the Lewiston Plateau, Craig Mountain, and Camas Prairie would show 

the relations expressed in fig. 3. 

Such a fold may, perhaps, be termed a gentle anticline, but as it 

unites two broad plateaus in which the strata are but gently inclined, 

it seems more accurate to designate it a monocline. 

West East 

t.ewlsron Plat"ee~u C8ma6 Prai'rle 

i:::=:::;H::::;::OR;::::::IZ::=:ON~TA¥.L S§CA~Lit~;3'0 MILLS 

FIG. 3.-Section through Lewiston Plateau, Craig Mountain, and Camas Prairie. 

At its n0rtheastern extremity the Craig Mountain fold commences 

as a broad, gentle swell, and from this indefinite beginning it increases 

in height and steepness to the southwest until in the vicinity of W aha 

it is about 1,000 feet high ·and probably passes into a fault. In its 

higher portion, overlooking Snake River Canyon, Craig Mountain has 

an elevation of nearly 5,000 feet above the sea, and is densely forest 

covered. It is not a smooth plateau, but has been trenched by stream 

erosion. The most conspicuous change thus produced is in the case of 

Mission Creek, which has its source well to the southeast of the crest 

of the uplift, flows across it in a deep canyon, and continues, to its 

junction with Lapwai Creek, in a canyon cut in the Lewiston Plateau. 

Oa,mas a·nd Karn,iah prairies.-To the southeast of Craig Mountain 

lie the broad Camas and Kamiah prairies, beneath which the layers of 

Columbia River lava over an extensive area are nearly horizontal. This 

plateau measures about 40 miles in length from northeast to southwest, 

and is about 25 miles wide. The lava sheets beneath it, although horizontal throughout nearly its entire extent, are bent upward, as already 

stated, along its northwestern margin, to form the Craig Mountain 

monocline. The border of the sheets adjacent to the uplands of older 

rock on the south and east are also gently inclined upward from the 

great central area. Whether the rocks in this region form a complete 

basis remains to be determined by a study of the structure in the 

vicinity of Agatha. There the beds are nearly or quite horizontal, 
RUSSELL.] PHYSIOGRAPHY. 61 

and the Camas-Kamiah Plateau merges into the Uniontown Plateau, 

with little if any line of demarcation between, except such as has 

resulted from erosion. The general elevation of the broad central portion of this plateau is about 3,000 feet, and its surface is deeply 

trenched by various branches of Clearwater River. 

Surnmary. -The deformation of the Nez Perce region since the 

outpouring of the Columbia River lava has been mainly in the direction 

of a tilting of the once horizontal lava sheets over broad areas. The 

movements have been grea~est along certain lines where sharp folds 

have been produced which at times pass into faults, as the Clearwater 

and Craig escarpments. The most pronounced change has taken place 

in the Blue Hills, where a dome-shaped uplift has been raised. This socalled dome, however, is steepest on its southern side, and from another 

point of view may with propriety be considered of the same type as 

the Craig Mountain fold, but of larger size, and without a break in its 

steeper side. · 

The class of folds represented by the Blue Hills dome, Craig Mountain, and the Clearwater escarpment may be likened to waves and 

swells on the ocean; some are upswellings with nearly circular bases, 

others are elongated and have steep slopes on one side of the crest and 

a gentle descent on the opposite side, while in other instances the waves 

break, as when a monoclinal fold passes into a fault. There are also 

basins between the elevations, and extending through the waves and 

troughs alike are the deformed layers of once horizontal lava sheets. 

The elevations and depressions are so broad and the inclinations of the 

strata in general are so gentle, that the geologic terms in current use, 

derived principally from the study of sharply folded regions, can not 

be applied t<? them without conveying false impressions. The generalized type of the struetural features may be considered as a monoclinal fold connecting two broad plateaus in which the strata are either 

horizontal or gently inclined. The greatest departure from this type 

occurs where the fold approaches a dome in shape, or where the 

steeper limb of a monocline is broken and becomes a fault. 

LEADING FEATURES IN THE RELIEF DUE TO EROSION. 

The Nez Perce region is characteristically a land of deep, steep-sided 

canyons with broad, generally level, remnants of the dissected plateaus 

between them. The canyons are naturally divided into two claeses in 

reference to the origin of the streams that excavated them: (1) Those 

through which flow rivers the courses of which were determined before 

the deformation of the original lava plate.au occurred, and are therefore 

to be classed as antecedent st1·earns; and (2) the canyons cut by branches 

of the master streams, which in most instances had their courses determined by the slopes of the secondary plateaus and the monoclinal folds 
62 GEOLOGY, ETC., OF NEZ PERCE CO., IDAHO.-PART I. [No. 53. 

which were produced by movements in the earth's crust, and which 

maMy the:fieforte be term

1 

ed cfonseq,nent streadrns. d b t d t t _-j·.·

agm cen examp es o canyons pro uce y an ece en s reams 

are furnished by Snake, Salmon, Clearwater, and Grande Ronde rivers. 

Each of these rivers flows through a profound canyon of its own making, but the height of the bordering walls varies from place to place 

in accordance with the movements in the direction of elevation or 

depression which have affected the country it crosses. Where plateaus or monoclinal folds have been boldly upraised athwart the course 

of a stream, its bordering walls are high and rugged; and where the 

rocks have been depressed the work of the stream has been less to 

establish a graded course to the sea, and its canyon becomes correspondingly shallow. In other words, the streams antedate the time 

when the plateaus were tilted or the monoclinal folds and faults came 

into existence, and have maintained their right of way as the country 

was deformed. The consequent streams represented by Asotin, Lapwai, Tammany, Lawyers, and many other creeks have had their courses 

determined by the slopes given to the various secondary plateaus into 

which the originally level lava sheets have been broken, and the depths 

of the canyons they have excavated have been determined by the depths 

of the great canyons cut by the master streams to which they are 

tributary. 

Canyons of Snake Rhwr.-The head branches of Snake River are in 

southeastern Idaho and in neighboring portions 'of Wyoming, ineluding 

the western part of the Yellowstone National Park. The river at first 

flows westward across southern Idaho for a distance of about 400 miles. 

It then bends sharply northward, and for a distance of 220 to 250 miles 

it follows the boundary between Idaho and the States of Oregon and 

Washington to Lewiston, where it again turns to the westward, and 

at Alpowa makes still another sharp bend, where it enters a steep-sided 

canyon cut in the Uniontown Plateau, and continues in a canyon to 

near its junction with the Columbia. The length of the river is in the 

neighborhood of 750 miles, and the part of its course to which attention is here invited is the northern portion of the central or northwardflowing section. Snake River is characteristically a canyon stream 

throughout nearly its entire leng-th. The head of its canyon is now at 

Idaho Falls, in the southeastern part of Idaho, where its waters make 

a plunge of about 30 feet into a narrow trench in the basaltic rock. 

For a hundred miles above this cascade the main river and several of its 

branches flow over the surface of a vast lava flow, and instead of corrading their channels they a.re upgrading them by the deposition of 

aHuvium brought from the 1nountains. Below Idaho Falls-practically 

all of the way to where it joins the Columbia-the river flows between 

precipitous walls from a few hundred to 4,000, and even 6,000, feet 

deep. From 30 to 60 miles south of Nez Perce County the river flow~ 
U. S. GEOLOGICAL S'JRVEY WATER-SUPPLY PAPER NO. 53 PL. Vtl l 

SNAKE RIVER CANYON, SHOWING DETAILS IN WALL. 
RUSSELL.) PHYSIOGRAPHY. 63 

through an unusually rugged region known as the Sevml. Devils and 

Powder River (Eagle Creek) mountains, which are about 9,000 feet 

high and are mottled with snow throughout the summer. The combined canyon and mountain scenery.is there perhaps the wilde~t and 

grandest in the Northwest, and rivals that of the finest portions of the 

justly celebrated Grand Canyon of the Colorado, except in brilliancy 

of color. 

As is indicated on the accompanying map (Pl. li), Snake River follows the western boundary of Nez Perce County for from 40 to 50 

miles. In this portion of its course it has excavated a canyon which 

may be divided into two well-defined sections of about equal length. 

Throughout the southern half of its course the river is in the bottom 

of a magnificent canyon with deeply sculptured walls 4,000 feet high 

and about 15 miles wide at the top. The rim rock at the crest of 

the walls on each side is formed by the edges of a lava sheet which 

immediately underlies the surface of Craig Mountain and of another 

similar plateau in Oregon. The northern half of the portion of the 

canyon referred to is narrow, being perhaps 2 miles wide at the top, 

and is cut in nearly horizontally bedded lava sheets; the walls, which 

are so steep that they appear vertical, are about 2, 000 feet in height. 

This portion of the canyon has been excavated approximately along the 

axis of the trough between the Clarkston and Lewiston plateaus, which 

pitches to the northward, and the canyon walls decrease gradually in 

height as the lowest portion of these depressed plateaus is approached 

at Lewii;ton-Clarkston. The well-marked differences exhibited bv 

these two sections of the canyon are due to the fact that in the southern section the rocks have been upraised and so profoundly dissected 

that .. the granite, limestone, ·etc., beneath the basalt is exposed and 

deeply trenched, while in the northern section the walls are entirely 

of basalt and the plateau through which the river flows has been 

depressed and the task of cutting a trench to a uniform gradient much 

lessened. These differences in the two sections of the canyon may be 

recognized by comparing Pls. IV and VI, B. The former is a view of 

the narrow, steep-sided canyon above Asotin, taken from a locality on 

its eastern border near W aha, and the latter is a view taken on the 

brink of the canyon in its deeper portion, on Craig Mountain opposite 

Mount Wilson, but the distances are so great that it fails to convey 

even a faint impression of the magnificence of the scene. Details of 

the walls of the canyon are shown in Pl. VIII. 

Snake River Canyon in its deepest and wildest portion adjacent to 

Nez Perce County is joined by Salmon River Canyon, which comes in 

from the east and is of the same depth and character as the mighty 

trench excavated by the master stream. About 20 miles below the 

the mouth of Salmon River, Grande Ronde River joins Snake River 

from the west, and also flows through a magnificent canyon, scarcely 
64 GEOLOGY, ETC., OF NEZ PERCE CO., IDAHO.-PART I. lNo. 53. 

second in its scenic features to that of the larger river, and, like it, 

about 4,000 feet deep. Near its mouth Grande Ronde River is joined by 

Joseph Creek, which ha~ also excavated a canyon as deep as the one it 

JOins. These several strong streams, acting like endless saws, have cut 

into the great plateau which was elevated athwart their courses. Each 

of their branches has also striven to deepen its canyon at the same 

rate as the master stream, and the result is that a once even-surfaced 

and monotonous plateau has been given an exceedingly rugged topography. 

The impression gained by one who follows the immediate borders of 

Snake River and its various branches would probably be that he is 

traversing a mountainous region; and this conclusion is true enough, 

for the land forms to be seen are far more rugged and lofty than the 

ridges and peaks of many greatly admired mountain ranges. It is 

only when a commanding summit is gained, like the top of Mount 

Wilson or the southern border of the Blue Hills, that the relations of 

the topographic features of an extensive portion of the rugged country 

are recognized, and it is seen to be a deeply dissected plateau. In farreaching views large areas of the unmodified plateau surface are in 

sight, and the change from what is termed young topography to 

middle-aged and mature topography can be traced in different portions 

of the same upraised block of the earth's crust. 

One not familiar with canyon scenery may perhaps fancy that the 

excavations made by streams in an elevated plateau are narrow trenches 

with vertical walls-in fact simply ravines of larger growth. While 

this ts to some extent true of young canyons in homogeneous and resistant rocks, yet when the trenches become deep, especially if the rocks 

cut through are of varied character, th~ original narrow excavations 

are widened, especially at the top, and their walls are sculptured by 

lateral streams and are trenched by rills and brooks originating on 

them so as frequently to impart to them great diversity. 

In the case of the canyon of Snake River from the mouth of Salmon 

River to near the locality where Grande Ronde River joins it, and 

again a few miles farther downstream, in the vicinity of Buffalo Rock, 

as has already been described, the Columbia River lava forms the upper 

portion of the canyon walls, whil~ the lower slopes are cut in older 

and for the most part more resistant fol·mations. The upper portions 

of the bordering walls, composed of basalt, have receded, and the canyon has been widened there more rapidly than in the lower portions, 

owing to the greater rapidity with which basalt weathers, in comparison with the formations on which it rests, and also on account of its 

longer exposure to the atmosphere; so that a broad canyon, with sculptured walls in which the exposed edges of the lava sheets are horizontal, has in its bottom a narrower canyon with precipitous and rugged 

sides. This canyon within a canyon is due entirely to differences in 
RUSSELL.] PHYSIOGRAPHY. 65 

the resistance of the rocks to weathering, and does not indicate movements in the earth's crust, as does a somewhat similar occurrence in 

the Grand Canyon of the Colorado. 

Throughout the portion of the canyon where the rocks beneath the 

lava are exposed there is no flood plain and no land that is under cultivation. In the next section downstream, where only basalt occurs, 

although a true flood plain is lacking, there are small, moderately flat 

areas, composed in part of talus, which are irrigated by water derived 

from brooks which flow down steep side gulches, and orchards of 

peaches, apricots, peai·s, etc., are cultivated, producing. a rich return 

of excellent fruit. The combined area of these detached fragments of 

flood plains that are under cultivation between the mouth of Asotin 

Creek and Grande Ronde River is only about 100 acres. 

Downstream from where the last exposure of the terranes beneath 

the basalt is to be seen, the walls of the canyon are precipitous from 

base to summit, and although encumbered with debris are mostly g;rass 

covered. The character of the precipices is well shown in Pl. IV, in 

which the edges of the nearly horizontal lava sheets can readily be 

recognized. This portion of the canyon, as previously stated, is cut 

in general along the junction of the Lewiston and Clark8ton plateaus, 

and the rocks are inclined downward toward the mouth. The walls of 

the canyon decrease in height as one approaches Lewiston-Clarkston, 

and at the same time its bottom becomes somewhat broader. 

Just below Lewiston-Clarkston Snake River makes an abrvpt bend 

to the westward. This sharp turn is due to the Clearwater escarpment, which runs at right angles to the previous course of the river 

and is about 2,000 feet high, with southward-dipping beds on its face 

which are inclined at angles of from 4:0 to 50 degrees or more. Evidently the escarpment was raised across the course of the river, or, 

more accurately, the plateau to the southward was depressed and the 

stream was turned aside. The river on turning to the westward follows the base of the great escarpment, but soon cuts into the fold which 

forms the escarpment, and flows along it for a distance of 5 or 6 miles, 

to Alpowa. There it makes another abrupt bend, and enters a narrow, 

steep-walled canyon cut in the Uniontown Plateau, similar to that 

shown in Pl. IV. The relation of Snake River to the monoclinal fold 

forming the Clearwater escarpment, in the portion of its course 

between ~ewiston and Alpqwa, is the same as exists in the case of 

Clearwater River. In fact, the portion of Snake River referred to is 

almost a direct continuation of Clearwater River, and flows along the 

same monoclinal fold, which there passes into a fault, leaving a large 

portion of the southward-dipping rocks on its southern or left border. 

The beds on the south side of the river dip southward at an angle of 6 

to 7 degrees, but soon flatten and pass under the Clarkston Plateau, 

where they are nearly horizontal. 

IRR 53-01--5 
66 G EO LOGY, ETC. , OF NEZ PERCE CO. , IDAHO. -PART I. [No. 53. 

The variations in the depth of Snake River Canyon below the general level of the adjacent plateaus illustrate the relation of the river's 

work to the deformation which the rocks have undergone, and show 

that where the rocks have been lifted highest the trench cut by the 

river is deepest, and where the rocks have been depressed the walls of 

its canyon become low-at Lewiston-Clarkston they nearly disappear. 

Snake River Canyon is typical of the clags of larger canyons in the 

Nez Peree region, and to save spaee and avoid repetition the others 

need not be described at length. 

Oanyon o.f G-rande Ronde Rtver.-The eouqtry to the south of the 

Blue Hills is a high, deeply dissected plateau of the same general character as the neighboring region in which Snake River has excavated 

its magnificent canyon, except that the Columbia River lava there 

seems to be thicker, as the rocks beneath it are not exposed. 

Grande Ronde River, Joseph Creek, and their various tributaries 

have excavated deep eanyons, and the remnants of the original plateau 

have been reduced in width until in many instances they are sharp, 

serrate ridges. Everywhere throoghout the rugged lands thus produced the edges of horizontal lava sheets are to 1Je seen. In few 

places in the United States can better illustrations be found of the 

transformation, by stream erosion, of a level plateau underlain by a 

great thickness of horizontally bedded rocks into a region of excessively rugged topography. Near the junction of Joseph Creek with 

Grande Ronde River, and between the same creek and the canyon of 

Snake River, the topography is as rugged as it ean be made with the 

present amount of uplift. Many of the ridges are sharp and along 

their crests are broken into pinnacles through the action of lateral 

rills and m·eeks, rain, frost, and wind. The eontinuation of the denudation, which has been long in progress, will tend to decrease the 

height of the multitude of ri_dges and peaks and to lessen the ruggedness of the relief. In short, the topography is mature and will slowly 

lose its salient features and flatten out so as to resemble its original 

monotonous eharaeter, unless renewed uplift occurs so as to allow tlie 

streams to eut more rapidly. Aseending the ridges between the 

various streams and traversing them toward the sourees of the bordering eanyons, they beeome broader and are easily recognized as portions of a vast, nearly level plateau. These broad surfaces are eovered 

with a deep residual soil, as is common in all sueh instanees in the Nez 

Perce region, and thm~e probably has been some lowering' of the general level, owing to roek deeay and solution, but the :tmount is not 

known. . In this conneetion, however, it should be remembered that 

the lava in changing to soil not only loses bulk, on aceount of the 

removal of the more soluble material, but may .also gain in volume by 

reason of the ehange that takes p]ace from a dense to a somewhat open 

texture, and also from the swelling of eertain minerals because of a 

change to a hydrous condition. 
RUSSELL.] PHYSIOGRAPHY. 67 

One of the most instructive features in connection with the canyon 

of Grande Ronde River is the fact that the river cuts across the southern slope of the Blue Hills uplift, and there the lava sheets in each of 

its canyon walls dip southward. The explanation of this is that the 

river had its right of way established before the dome from which the 

present rugged relief of the Blue Hills has been produced by erosion was 

upraised. That is, as previously stated, the river is to be classed as an 

antecedent stream. The southward dip of the lava sheets in which the 

river in the portion of ita course indicated on Pl. II· has sunken its 

channel in an east-west direction has had a marked influence on the 

details of its bordering walls. On the north side of the canyon, where 

the lava sheets are inclined downward toward the river, there have been 

innumerable landslides; while on the south side, where the dip, although 

small, is away from the river, the bluffs in many places approach the 

vertical, and landslides are rare, except near the top, where occurs a 

bed of soft sedimentary material, which has caused a terrace to appear. 1 

Canyon of Salmon River.-At its mouth Salmon River is on a level 

with Snake River, into which it flows, but it is a rapid stream, throughout at least the lower 30 miles of its course, and has many swift, foaming rapids, but no actual cataracts. Where the two rivers unite there 

was, previous to the excavation of the profound canyons through which 

they now flow, about 2,000 feet in thickness of horizontal lava sheets 

resting on quartzite and dense igneous rocks. After cutting through 

the lava the streams found much more resistant rock below, and their 

canyons became narrow. The canyon of Salmon River for 5 or 6 miles 

upstream from its mouth is only wide enough for the roaring stream 

that rushes through it, and is quite impassable to man. Above this 

narrow portion, in excessively hard rock, the canyon widens, in basalt, 

and for about 20 miles, or to the mouth of Deer Creek, which comes 

in from the west, there is a narrow strip of flood plain on its western 

side and a series of terrace-like benches on the salients. between the 

lateral streams; but the east wall is usually precipitous and possesses 

remarkably fine scenery. Beginning about 5 miles from its mouth and 

extending upstream 4 or 5 miles, Salmon River makes two sharp bends 

and passes about the base of a massive pile of basaltic rocks 2,500 feet 

high, which have been sculptured into castellated forms of remarkable 

grandeur. Here the basalt forms the bed of the stream, and on its 

immediate banks are exposed the summits of columns which show that 

the larger part of a thick sheet of lava still remains uncut. From t4is 

locality up to the summit of the remnants of the original plateau, which 

occur on all sides at a distance of from 5 to 15 or 20 miles, one finds 

only the edges of horizontal lava sheets. The portions of the original 

plateau remaining have surface elevations of more than 5,000 feet. 

The elevation at the mouth of Salmon River, according to surveys 

1 Other facts concerning Grande Ronde River and its branches will be found in a preceding report 

by the author-Water-Supply and Irrigation Paper U.S. Geol. Survey No.4 (1897), pp. 17, 25, 26. 
68 GEOLOGY, ETC., OF NEZ PERCE CO., IDAHO.-PART I. [No. 53. 

made by the Oregon Railway and Navigation Company, is 965 feet, 

and the thickness of the lava is not less than ±,000 feet and may be 

considerably greater. 

Upstream fron1 the mouth of Deer Creek, Salmon River passes 

through two narrow gorges of dense igneous rocks, which project 

upward into the lava sheets; but between these obstructions the canyon 

widens, and has been excavated wholly in basalt. At the great bend 

of the river near Keuterville, the rocks beneath the lava again become 

prominent in the canyon walls, forming ahout half of their height, and 

the great gulf, about 3,500 feet deep, is nearly as impressive as the 

wildest portion of the canyon of Snake River. The same magnificent 

scenery continues far up the river above the big bend, but only distant 

views of it have been had by the writer. 1 Each of the creeks tributary to Salmon River below the big bend also flows in a deep canyon 

of its own making, so that the once widely extended plateau is nearly 

as deeply dissected and rugged as the similar region drained by Grande 

Ronde River. 

The remnants of the elevated plateau adjacent to tpe lower course 

of Salmon River are elothed with coniferous forests, and trees grow 

here and there on the sides of its canyons; in a few instances yellow 

pines occur at the river's margin. The canyon walls, even where precipitous, are covered with bunch grass and afford fine pasturage. 

Perhaps the most instructive physiographic feature of the river is the 

fact that for a distance of froin 10 to 15 miles above the big bend it has 

cut its great canyon diagonally across a sloping plateau, and flows in a 

westerly direction, while the plateau dissected by it slopes northward, 

in conformity with the gentle inclination of the lava sheets beneath it. 

When followed northward the lava sheets flatten out and pass 

beneath the level surface of the Camas Prairie. A view of the lava 

sheets in the canyon is shown in Pl. V, B. The river crosses the sloping plateau in the great sweeping curve, but is sunk in a canyon about 

3,500 feet deep. The relation of the course of the river to the slope of 

the plateau it crosses is shown in Pl. IX, B, and details of the canyon 

walls in Pl. X. Rock Creek, which rises on ::Mount Idaho and crosses a 

portion of the Camas Prairie, joins Salmon River after flowing through 

a deep, rugged gorge cut in the upraised border of the basin of the 

Camas Prairie; that is, it flows against the slope of the country and 

against the dip of the rock beneath it. The meaning of these facts is the 

same as in the case of Clearwater and Snake rivers, which have excavated 

canyons in the monoclinal fold joining the Uniontown Plateau with 

the Lewiston-Clarkston plateaus, and, again, in the case of Grande 

Ronde River, which cuts into the Blue Hills dome. In other words, 

1 An account of the upper portion of Salmon River Canyon, together with much information concerning the geology of the region traversed by it, will be found in the report by Waldemar Lindgren 

before cited, viz, The gold and silver veins of Silver City, De Lamar, and other mining districts in 

Idaho, published in the Twentieth Annual Report of the U.S. Geological Survey, Part III, pp. 65-256. 
U. 8. GEOLOGICAL SURVEY WA TER -SUPPLY PAPER NO. 53 PL. IX 

A. VALL EY OF SOUTH FORK OF CLEARWAT ER RIVER NEAR KAMIAH. 

R. SALMON RIVER CANYON FROM COTTONWOOD BUTTE. 
RUSf:?ELL.) PHYSIOGRAPHY. 69 

the rights of way of Salmon River and Rock Creek were established 

before the plateau formed by the last sheet of Columbia River lava. 

was disturbed from its originally horizontal position. 

Oany()11)3 of Clearwater River.-Clearwater River is formed by the 

union of many streams, the larger of which have their sources in the 

Bitterroot Mountains and flow westward. All of these branches, as 

well as the main river, flow in canyons, and in all cases where a 

stream passes from the region of diorite, schist, etc., into the Columbia River lava, a change in the character of the excavation it has made 

is at once manifest. In the older rocks the canyons are wide at the 

top and have less precipitous walls than where they have been cut in 

lava. The topography in thr> mountains consists of a labyrinth of sharpcrested ridges, with flaring valleys between, and the streal)ls in the 

valley are swift and without flood plains. The character of the country is indicated to some extent by the fact that the trails follow the 

crests of the ridges persistently, there being no room for them adjacent 

to the streams. On entering the lava-covered region the streams are 

bounded by more precipitous walls, and where they have not cut 

through the lava their sides frequently approach the vertical, from 

base to summit. Some of the creeks from the mountains flow for a mile 

or more over the basalt, as surface streams, before plunging into a narrow canyon at its head. Between the canyons cut in the lava there 

are broad, nearly flat remnants of the once widely extended and undissected plateau. These differences may be briefly summarized by. stating that in the rocks older than the Columbia River lava the topography 

is mature, but in the region floored by the lava it is young. 

The particular feature in the physiography of the region drained by 

Clearwater River which is of greatest interest is the relation of the 

lower portion of the trunk strean1 to the monoclinal fold which unites 

the Uniontown Plateau with the Lewiston-Clarkston plateaus. In the 

portion of its course referred to Clearwater River flows directly along 

a monoclinal fold, in what may be termed, under a classification of 

valleys once proposed by J. W. Powell, 1 a monoclinal valley; that is, 

the rocks in each wall of the valley, as well as beneath its floor, dip in 

one direction, namely, southward. 

On the south side of the valley the rocks are inclined upward, from 

the position they occupy beneath the Lewiston Plateau, at an angle of 

perhaps 1 or 2 degrees in the vicinity of Myrtle, which increases westward to the great escarpment overlooking Lewiston, where it is 40 to 

50 degrees. Throughout this distance the crest line of the north wall 

of the valley is nearly level, although rendered irregular by the pres 

enee of gulches with salients between; but the south wall, which at 

the east is about on a level with its companion to the north, gradually 

declines, and at Lewiston it nearly disappears. The south wall is com1 Exploration of the Colorado Riwr of the West. Washington, 1875, p. 160. 
70 GEOLOGY, ETC., OF NEZ PERCE CO., IDAHO.-PART I. [No.53. 

posed of lava sheets which dip southward but soon flatten and pass 

under the more nearly level Lewiston Plateau, thus forming an elevated rim along the side of Clearwater River Valley. This peculiar 

feature of a large river apparently excavating a canyon along a steeply 

sloping mountain side, instead of descending to the adjacent valley, 

can be explained only on the hypothesis that the course of the river 

was established before movements in the earth's crust formed the 

monoclinal fold which it follows. The river has deepened its channel 

as the rocks beneath it were bent. 

The relation of Clearwater River to the fold it follows suggests that 

before the lava sheets were flexed the river had cut in them a trench 

sufficiently deep to determine a line of weakness along which a sharp 

fold was produced when subsequent movement occurred. The greater 

part of tho canyon cutting, however, was after the monoclinal fold was 

initiated. 1 

RELATION OF THE STREAMS TO GEOLOGIC STRUCTURE. 

In the brief account of the canyons of the Nez Perce region which 

has just been given, references have been made to the manner in which 

the larger streams cross sloping surfaces diagonally, as in the case of 

Grande Ronde River, which cuts into the southern portion of the Blue 

Hills d.ome, and Salmon River, which sweeps in a,great curve into the 

upraised border of the Camas Prairie but leaves that topographic 

basin without reaching its lower portion; and, also to the fact that 

Snake River has cut through the Craig Mountain uplift, and again, at 

the depressed northern border of the Lewiston-Clarkston plateaus, on 

which its valley broadens and is only about 200 feet deep, it enters a 

canyon 2,000 feet deep in the Uniontown Plateau. In this same category is to be placed the fact that Clearwater River in its lower course, 

and Snake River between Lewiston and Alpowa, flow directly along a 

monoclinal fold in monoclinal valleys. 

The important group of observations just summarized shows that 

the courses of the streams referred to are to a great extent independent 

of the structure of the rocks in which they have excavated their canyons, 

aRd are also equally independent of the larger features in the surface 

relief, since the inclination of the various plateaus, which are the major 

physiographic elements, corresponds with the dip of the underlying 

lava sheets. In order to make this conclusion clearer and more graphic, 

let us trace in outline the chapter in the history of the Nez Perce region 

to be read in surface geology and drainage system. 

1 In this connection the idea presents itself that if a broad plateau underlain by horizontally bedded rocks of the nature of, especially, lava sheets, which may be considered as being resistant to 

deformation by bending, should have a canyon cut in its surface, such a canyon, especially if long 

and straight, would mark out a line of weakness which would determine where maximum deformation would occur in case the beds should be warped or displaced by a tangential thrust acting at 

right angles to the course of 'the canyon; that is, in some instances streams are not only antecedent to 

structure, but they exert an influence on the structure itself. While the facts in hand do not warrant 

the unqualified ac;ceptance of this view, they at least awaken a desire to test it by more extended 

oi?servatiom. 
t.J. S. GEOLOGICAL SURVEY WATER-SUPPLY PAPFR NO. SJ PL. X 

SALMON RI VER CANYON, SHOWING DETAILS IN WALL. 
RUSSELL.] PHYSIOGRAPHY. 71 

When the last sheet of Columbia. River lava was poured out it ·formed 

the surface of a nearly level plateau to the westward of the Bitterroot 

Mountains, across which the streams from the eastward, such as Snake, 

Salmon, and Clearwater rivers, had to flow in order to deliver their 

waters to the ocean. It is probable that lakes were formed· on the lava 

plateau, but this and other phases of the hist~n·y need ·not concern us 

at present. The rivers in time excavated canyons which were deepest 

near their mouths and were slowly extended upstream. After this 

work was well under way in the immediate region here considered, 

movements in the rocks began, which continued for a long time, and 

perhaps have.not yet ceased. These movements produced a deformation of the originally level surface, of the nature of a tilting of broad 

blocks of the original plateau. These blocks experienced differential 

movement in reference to one another, and along their borders were in 

, . certain instances bent into monoclinal folds, and where the flexures 

were sharpest breaks occurred. The differential movements of the 

various blocks went on so slowly in most instances that where the 

rivers -crossed the belts of flexure they were able to deepen or upgrac:e 

their channels ·as rapidly as the surface was deformed. Where the 

border of a tilted block rose athwart the course of a river a canyon was 

cut across it, as in the case of St~ake River where it crosses the Craig 

Mountain uplift. In some cases, however, the deformation went on 

more rapidly than the river could deepen or upgrade its channel, and 

the stream was turned aside. An illustration of this is furnished by 

Grande Ronde River, which was turned from the course it has in its 

upstream portion by the elevation of the Blue Hills dome. The best 

example of the raising of a wall directly athwart the course of a 

river, and that, too, the largest river of the region, is furnished by the 

Clearwater escarpment, which turned Snake River aside at the site 

.of Lewiston. This escarpment, which it will be remembered is the 

southern border of the ne~rly level Uniontown Plateau, was formed 

directly across the course of Snake River, and the maximum displacement occurred at the. locality where the river crossed its site. For 

a portion of the way between Lewiston and Alpowa the Clearwater 

escarpment, which elsewhere is a monoclinal fold, became a fault. The 

break here occurred 2 or 3 miles west of Lewiston; but directly in the 

course of Snake River to the north of Lewiston the rocks in the face of 

the escarpment as it exists to-day clip southward at angles of from 30 

to 60 degrees. The differential movement between the borders of the 

b niontown Plateau and the Lewiston-Clarkston plateaus occurred with 

. sufficient rapidity to deflect the river and cause it to flow westward 

along the break produced· by faulting until it could pass about the end 

of the portion of the belt of disturbance where the movement was 

greatest. An irregular course was thus established, which the stream 

was able to maintain as the tilting and depression of the LewistonClarkston plateaus went on. It is possible that Snake River was checked 
72 GEOLOGY, ETC., OF NEZ PERCE CO. • IDAHO.-PAR'l' I. [No. 53. 

by an uprising of the Clearwater escarpment, and a l'Obe was formed. 

That such was the case, however, has not been clearly proved, although 

certain silt-like deposits on the Clarkston Plateau may have been laid 

down in such a water body. The deposits referred to have not been 

carefully examined. 

As the deformation of the original lava plateau progressed and the 

larger streams deepened their channels, their tributaries, situated ·on 

rocks that were but slightly disturbed, or strong enough to maintain 

their rights of way where the n1ovements were greatest, also deepened 

their channels, owing to the greater velocity given them by the lowering of the master streams into which the:r discharged and likewise 

excavated canyons. Most of the smaller streams, however, came into 

existence after the deformation of the surface was initiated, and were 

guided by the slopes produced. For example, all of the streams which 

flow from the Blue Hills to Snake River have courses such as would 

be determined by the present slope of the sur face. These streams, 

and probably all others flowing away from the Blue Hills, came into 

existence after that region was upraised into a dome. In a sin1ilar 

way, all of the streams in the central portion of Nez.Perce County, 

which enter either the Snake, the Salmon, or Clearwater River, flow 

through channels such as would be determined by the inclinations of 

the present surface and the depth of the master streams to which they 

are tributary. 

The streams of the Nez Perce region may therefore be classed in 

two groups, in reference to the relation they bear to the structure of 

the rocks over which they flow: (1) Streams the courses of which 

were established before the underlying rocks were disturbed from their 

original horizontal positions, and which may be classed with what 

geographers term antecedent streams, of which Snake, Grande Ronde~ 

Salmon, and Clearwater rivers are the leading if not the only examples~ and (2) streams which came. into existence on the slope's pro- . 

duced by deformation, and which are consequent to them and therefore are tetmed consequent streams, many examples of which might be 

named, as, for instance, Asotin Creek and its several branches, Lapwai Creek and its principal tributaries, Cottonwood, Lawy~rs, Little 

Canyon, and other creeks which drain.broad portions of the deformed 

lava-covered country and are consequent on slopes produced by deformation. There is still another and subordinate class of streams, such 

as flow down ~he steep ca~yon walls, which are. consequent on slopes 

due to erosion. 

· STREAM TERRACES. 

In a previous report 1 the writer has directed attention to the wid"ely 

distributed and frequently thick gravel desposits in the canyons of 

both the Cascade and the Rocky Mountain ranges in Washington and 

1 A preliminary paper on the geology of the Cascade Mountains in northern Washington, by I. C. 

Rm;sell: Twentieth Ann. Rept. U.S. Geol. Survey, Pt. II, pp. 173-184. · 
RUSSELL.j PHYSIOGRAPHY. 73 

Idaho, which were formed after the rivers had excavated their channels to their present depth, but have since been reexcavated, so that 

in many instances only small remnants of them now renmin. Several 

examples of these gravel deposits belonging to the Pleistocene division 

of geologic history occur in the Nez Perce region. 

Remnants of former flood plains of Snake and Clearwater rivers 

. occur in Lewiston and Clarkston, and may there be studied to advantage. In Lewiston sections of heavy stream-laid gravel are admirably exposed in the bluff which separates the lower portion of the city, 

which js built principally- on the present flood plain of Clearwater 

River, from an old flood plain, at an elevation of 150 feet above the 

low-water stage of Snake River, on which the newer portion of the 

city is situated. The plateau referred to is an abandoned flood plain, 

and shows that the rivers now flowing past its base at some for1ner 

period filled their channels from side to side, so as to elevate their 

beds at least 150 feet above their present summer levels. The plateau 

on whieh the newer portion of the city is located is triangular in shape, 

a mile or more broad, and on its margins facing Snake and Clearwater rivers instructive sections can be seen of the well-worn 

. bowlders, cobblestones, gravel, and sand of which it is composed. As 

in the case of many flood plains, the last material deposited is a fine 

sand or silt. On the southern side of the plateau, where it joins the 

uplands at what was formerly the junction of Snake and Clearwater 

rivers, there are still higher gravel deposits of the same character, 

showing that the most conspicuous terrace now remaining was excavated in a higher flood plain, the upper limit of which is indefinite. 

At the mouth of Tammany Hollow, nearly opposite Asotin, there is 

a well-defined gravel bar, built by Snake River, which crosses the 

mouth of the lateral canyon and at one time formed a dam which 

caused the waters of Tammany Creek to expand and form a small 

lake. This bar is, by aneroid measurement, 235 feet above the summer stage. of Snake River. Since Snake River cleared out the greater 

part of its former gravel deposits, Tammany Creek has cut a narrow 

channel through the obstruction at the mouth of its canyon. The bar 

referred to, and others similar to it along the course of Snake River, 

shows that the main stream was at one time overloaded with debris, 

a large part of which was deposited in its channel, while its small 

tributaries were not thus loaded and could not fill in their valleys so 

as to elevate their bottoms at the same rate as did the master stream 

to which they flowed. The result was that the weak lateral streams 

were ponded and expanded into lakes. In a similar way lateral canyons which were perhaps· without perennial streams were flooded, 

owing to the expansion of the main stream and the gravel carried into 

them. 

The broad, sloping gravel plain on which Clarkston stands is similar 

to the .gravel plateau in Lewiston. but oceupies a less sheltered posi-
74 GEOLOGY, ETC., OF NEZ PERCE CO., IDAHO.--:-PART I. [No.5a. 

tion in reference to Snake Hiver, and was cut away to a considerable 

extent as the river deepened its channel after the period of overloading had passed. The gravel be~eath Clarkston is situated on the imier 

or convex side of a river curve, and was left with a sloping surface as 

the stream migrated eastward. A similar sloping surface covered 

with fine sHt can be seen on the inner curves of many small streams 

which now meander through nearly level-floored valleys. 

Another remnant of the once extensive alluvial deposits along Snake 

River occurs just above Alpowa, forming a flat-topped terrace 150 

feet above its present summer stage. Again, in the canyon of Salmon 

River, about 5 miles above its mouth, there are, on each side of the 

canyon, terraces composed of a large variety of well-worn pebbles, 

which have a surface elevation of 230 feet above the present level of 

the rivers. 

The extreme upper limit of the gravel deposited in the canyon of 

Snake River, as determined by aneroid measurements, was stated in 

a previous report 1 to be 360 feet above the low-water stage of the 

river as it flows at present. This measure is perhaps too liberal, and 

may have to be reduced. The principal difficulty in determining the 

exact upper limit of the gravel lies in the fact that it is usually indefi- . 

nite~ and in some places is difficult to discriminate from the gravel 

derived fron1 sedimentary beds interstratified with the Columbia River 

lava. 

The remnants of the old gravel flood plains just described, taken in 

connection with similar facts observed over a wide extent of country 

in Idaho and Washington, furnish clear evidence that the' larger canyons of the Nez Perce region, after being excavated to their present 

depth, were deeply filled with gravel and subsequently were reexcavated. During the last down-cutting remnants of the former flood 

plains were left in sheltered places, as on the inner sides of sharp 

bends and at the mouths of s1nall lateral canyons. The changes in 

conditions which permitted the strong rivers to excavate .canyons in 

the Columbia River lava to a depth of from 2,000 to 4,000 feet, then 

deposit in them gravel to a depth of at least 230 feet, probably 360 

feet, and subsequently reexcavate them and renew the task of deepening the channels in the solid lava, seems to have been principally the 

overloading of the streams at a certain period in their history. For 

a long time the swift rivers rising in the mountains were able to carry 

their loads to the sea or to the larger rivers to which they were tributary, and the friction of the debris thus transported deepened their 

channels. Next came a period when the rivers had more debris 

delivered to them in their high-grade, and consequently swift, upper 

courses than they could transport through their long canyons, and 

some of it was dropped, thus raising the stream bed and permitting 

I Water-Supply and Irrigation Paper U.S. Geol. Survey No.4, pp. 56-57. 
RUSSELL.) PHYSIOGRAPHY. 75 

the water to flow more rapidly. After a time the overloading ceased, 

and the streams, with added energy, owing to the higher gradients 

produced by the partial filling of their channels, were enabled to 

remove the debris previously deposited. This work has gone on unttl 

nearly all of the gravel, sand, etc., formerly laid aside has been carried 

away, and the rivers in places are down to their beds of solid rock; 

but in general, as can be seen in Clearwater and Snake rivers for a 

distance of several miles from their junction, they are still floored with 

coarse gravel. During high-water stages immense quantities of this 

bottom load are moved downstream, to such an extent in the case of 

Clearwater River as to show the futility of attempting to deepen that 

river in order to make it navigable. 

The causes which led to the overloading of the rivers flowing from 

the mountains of Washington, Idaho, etc., during a certain period in 

their history, have been discussed in the previous report referred to, 

and can not be considered at length here. It will suffice to say that 

the main reason seems to have been the climatic change which brought 

on the Glaeial epoch. Precipitation is thought to have increased at 

that time beyond what it was before or has been since; the mean 

annual temperature was lowered, and glaciers existed in the mountains. These agencies would tend to increase the loads brought by 

swift tributaries to the trunk streams, but would also increase the volumes of the rivers and consequently their velocities and power to 

transport. If the increase in load, however, was in a greater ratio 

than the increase in transporting power, the stream beds would be 

upgraded; and, according to the best interpretation of the facts that 

can now be made, this seems to have been the case. 

LANDSLIDE TOPOGRAPHY. 

Rock masses which have descended as landslides form so important 

a feature of the canyon walls in the Nez Perce region and have so· 

intimate a connection with the search for lignite deposits and the 

·.question of water supply, that their nature needs to be well understood. 

The distinctions between landslides, displaced rock masses, rock 

avalanches, mud flows, snow avalanches, etc., have been pointed out in 

previous reports/ and seemingly but little needs to be said at present 

in this connection, except what applies directly to the region uncle1· 

consideration. 

A landslide is understood to be the breaking away of one or more 

large blocks of rock, or of a quantity of loose material, from a slope, 

lA geological reconnaissance in central Washington, by I. C. Russell: Bull. U. 8. Geol. Survey No. 

108, pp. 47--49, Pls. III, IV, and V. 

Topographic features due to landslides, by I. C. Russell: Pop. Sci. Monthly, Vol. LUI, Aug., 1898, 

pp. 480-189. 

A preliminary paper on the geology of the Cascade ~fountains in northern Washington, by I. C. 

Russell: Twentieth Ann. Rept. U.S. Geol. Survey, Pt. II, pp. 193-200. 
76 GEOLOGY, ETC., OF NEZ PERCE CO., IDAHO.-PART I. [No. 53. 

and its quick descent into an adjacent depression. The landslides in the 

Nez Perce region, so far as noted, are confined to the walls of canyons 

in the Columbia River lava. The most favorable conditions for their 

occurrence are where canyons have been cut in thick sheets of lava, 

especially where the lava is traversed· by vertical joints so as to be 

columnar, and rests on beds of clay, sand, gravel, volcanic dust, 

lapilli, etc. These conditions are rendered still more favorable when 

a series of lava sheets with included layers of soft material are inclined 

toward the stream which has excavated a canyon in them. Under 

such circumstances, blocks of lava are likely to break away from the 

cliffs and to descend the slope below, perhaps even reach the stream at 

its base. Where a landslide comes to rest, it is usually found that the 

surface of the fallen block or of the mass of loose material which has 

descended has a slope toward the cliff from which it felL This backward slope is frequently so pronounced that basins are formed, which 

under favorable climatic conditions become swamps or lakes, but in 

dry regions are more frequently grassy hollows, or perhaps are overgrown with bushes and trees while the drier slopes adjacent are bare. 

From recent landslides which retain their characteristic for1ns unimpaired there are in many regions, as has been described .in the reports 

just cited, illustrations of a complete t:;eries of gradations to areas which 

are nearly level although having a somewhat undulating topography 

produced by the weathering of ancient landslides. Thus there is a 

series of changes in relief, due to landslides, which may be included 

under the term landslide to_pograpl~y. Prefixes denoting age might be 

used in connection with this term, to indicate the extent to which the 

fallen masses have yielded to weathering and erosion. 

In the Nez Perce region landslides have occurred on the sides of all 

of the larger and many of the smaller canyons e4cavated in the 

Columbia River lava, in places frequently a score or more of miles 

in length, and on each side of a stream they can be counted by the 

hundreds in a single mile. Only a few of these many localities, 

however, can be referred to in this paper. 

On the north side of Grande Ronde River where it cuts into the . 

Blue Hills uplift, the conditions are unusually favorable for landshdes, 

as the lava sheets are inclined downward toward the river and have 

beds of sand, clay, lignite, and volcanic dw;;t interbedded with them. 

Over extensive areas, · measuring in fact many square miles, the 

canyon wall is encumbered by heaps and ridges of material which has 

descended from above. From the river's bank to the rim rock which 

defines the border of the canyon at the top of the Blue Hills, a distance of 7 or 8 miles, there is, except on the salients, a succession of 

fallen blocks, some of them at least a half mile in length, which frequently have undrained basins on their gently sloping northern sides. 

The characteristics of young landslide topography are there well displayed, although most of the fallen 1nasses have been in their present 
RUSSELL.] PHYSIOG R.APHY. 77 

position long enough to be covered with a deep soil, excert on the 

precipitous southern slopes, and are overgrown with magnificent 

forest trees. On the south side of the canyon the precipices are steep, 

in places nearly vertical for 2,000 feet above the river, and landslides 

are rare. The reason for this is that the lava sheets dip to the southward, or away from the river, and the tendency for blocks to fall is 

far less than on the opposite wall of the canyon. Near the summit of 

the southern wall there is a bed of soft material, reported to contain 

lignite, underlying the summit sheet of lava. This· sheet of soft 

material has caused the border of the lava layer above it to recede 

more rapidly than the margins of the layer beneath, and a terrace has 

resulted, which in many places has on its surface landslides and conspieuous talus slopes. 

In the walls of the canyon of Snake River the lava sheets are nearly 

horizontal, so far, at least, as a slope toward or from the riyer is concm·ned, and landslides are rare. So far as known. there is but one bed 

of sedimentary material between the lava sheets that have been cut' by 

Snake River. If two such soft beds are present, as is the case on 

Asotin Creek, they influence the topography in essentially the same 

way that a single sheet would, and for that reason the conditions are 

unfavorable for the development of characteristic landslide topography 

on a large scale. As previously stated, the sheet of soft material is 

at a depth of 200 to 220 feet, and, as on the south side of Grande 

Ronde River, has given origin to a terrace, which may be traced for 

a score or more of. miles along the walls of the canyon below th~ 

mouth of Grande Ronde River and into many of the smaller tributary 

canyons and gulches. This terrace is almost everywhere deeply covered with fallen debris, and frequently exhibits the characteristic 

featuret-5 of landslide topography. A typical example of the conditions 

just referred to can be seen on the east side of Snake River between 

Lewiston and the mouth of Tanunany Hollow, where the dip of the lava 

sheets beneath the Lewiston and Clarkston plateaus brings the soft 

layer which gives rise to the landslides down to within a few hundred 

feet of the level of the river. On the opposite side of the river is 

Swallow Rock, a displaced block of lava of unusually !arge size and 

massiveness, the surface of which slopes steeply downward toward the 

cliff from which it broke away. 

Landslides are abundrtnt throughout the course of Clearwater River 

and its prineipal tributaries where they have cut canyons in the lava, 

and are especially numerous in the vicinity of Kamiah, where they 

impress their peculiar feature:::; on the scenery of the bluffs, which for 

several miles face the river on each side. The lava sheets are there 

, nearly horizontal, but at a depth of about 800 feet, and contain an 

unusually thick layer of friable sandstone which has caused almost. 

innumerable landslides. The exceptional breadth of this portion of 

the canyon, which is a beautiful vale 2 or 3 miles wide, with pleasingly 
7 8 G EO LOGY, ETC, , OF NEZ PERCE CO. , IDAHO. -PART I. [No. 53. 

diversified, tree-clothed bordering bluffR 1,800 feet high, is due to 

the widening of the once narrow gorge by the falling of its walls. The 

irregularities which landslides give to the escarpments, and the subdued 

effeet of their slopes from the same cause, are illustrated in Pl. IX, A, 

a view of the eastern side of Kamiah Vale near the village from which 

it derives its name. 

In the description on page 39, of the occurrence of lignite and its 

associated sedimentary beds near Orofino and along the creek of the 

same name, mention was made of the numerous displaced rock masses 

in that region. The borders of the canyon of Orofino Creek not 

only owe the minor features of their topography to landslides, but 

the character of the entire canyon has been modified by them. There 

is an outer canyon, borderad by cliffs and steep talus slopes, from 700 

to 800 feet high. At the base of these rugged walls, in which the 

edges of horizontal sheets of lava appear, there is, on each side of the 

creek, an ·irregular terrace-like belt a mile or more wide, the surface 

of which shows the ridges, hills, and basins characteristic of landslide 

topography. This broken country is from 400 to 500 feet abo,,e the 

.stream which flows through it in a steep-sided inner canyon. At a few 

localities the landslides have obstructed the river and caused it to flow 

swiftly through narrow defiles. In one of these rapids, about 6 miles 

from the mouth of the creek, the water descends 92 feet in a distance 

of about 500 feet. 

FIG. 4.-Sections of cliffs with landslidt'~. 

On the North Fork of Clearwater River, opposite the mouth of Elk 

Creek, the canyon wall exhibits the characteristic feature that landslides give to precipit9us escarpments, and the cause of the numerous 

slides is revealed by the presence of sand and lignite in the fallen 

1nasses. It is stated that at this locality some movement in the displaced block& near the river has been recognized in recent years. 

It is perhaps unnecessary to attempt to give additional examples of 

the changes produced in canyons by the falling of their walls, for they 

~are so numerous that once the meaning of the ridges and basins so 

common on steep slopes is suggested a person can readily interpret 

them for himself. The manner in which the faces of cliffs break away 

and the dJsplaced masses descend the slopes below is illustrated in a 

general way in fig. 4. At a the nature of the canyon walls where not 

modified by landslides is indicated, the stratification being horizontal 

and the lava sheets separated in a single instance by a sedimentary bed; 

at b a single block has fallen; at c two slides have descended; and at d 
RUSSELL.) PHYSIOGRAPHY. 79 

an attempt has. been made to indicate roughly the nature of the canyon 

walls where many slides have occurred and where much loose material 

encumbers the slope. The last figure (d) illustrates in a rude way the 

condition of the precipitous slope throughout the greater part of the 

. lava-c<;>Vered portion of the Nez Perce region. The most noticeable 

feature in a landslide that has come to rest is the slope of the surface. 

of the fallen mass toward the cliff from which it. broke away. This 

characteristic backward slope is pronounced not only in solid blocks 

which still retain their stratification, but in masses of dislodged fragnlents, and it gives origin to basins which, as already noted, are 

frequently transformed int? lakes and swamps. 

The back slope in the landslides in the Columbia River lava is frequently from 3 to 5 degrees~ but may reach 20 or more degrees. This 

peculiar feature seems to be due to the fact that the friction of the 

sliding mass causes its forward portion at the base to be retarded so 

that it is overridden by the material in its rear. Where the base of 

the displaced portion is of soft material it is pressed outward to the 

front of the descending mass and is sheared and overthrust so as to 

become thickened. For this reason the thickness of the soft layers in 

the fallen masses is deceptive and might lead to erroneous conclusions 

regarding, for instance, the importance of a lignite bed. 

The general reason that landslides are more frequent and usually 

of larger size on Clearwater River and its main tributaries than along 

Snake River is that the soft beds to which the landslides are largely 

due are thicker and more numerous the nearer one approaches the 

mountains from which the streams brought debris and deposited it on 

the Columbia River lava. The beds of water-1aid debris are of the 

nature of wedges, which are not only most numerous but thickest and 

coarsest at the margin of the lava-covered country adjacent to uplands, 

and thin out and become finer as its central region is approached. 

These stream-laid deposits may merge with lacustral sediments, in 

which event other conditions favoring landslides would result. In 

addition to the presence of beds of soft material between the lava 

sheets, conditions favoring the occurrence of landslides are produced, 

as already explained, where the sheets have been tilted. 

So constant is the relation between landslides and the presence of 

sedimentary beds or sheets of volcanic dust and lapilli in the Columbia River lava, particularl}T where the sheets are horizontal, that the 

landslides furnish an indication of the extent and thickness of the soft 

layers. 

LAKE WAHA. 

The only water body in the Nez Perce region worthy to be termed a 

lake is 18 miles, in a direct line, southeast of Lewiston and at the base 

of the northeastward-facing escarpment of Craig Mountain. ·The lake 

is not only an exceptional feature in the deepl)r sculptured land where 
80 GEOLOGY, ETC., OF NEZ PERCE CO. 1 IDAHO.-PART I. [No. 53. 

it occurs, but it is i-iurrounded by attractive scenery and is charming in 

many ways. It occupies a steep-sided valley eroded by W aha Creek, 

which has been obstructed by landslides and has an area, as determined 

by surveys made by Mr. E. H. Libby, president and general manager of 

· the Lewiston Water and Power Company, of approximately 100 acres,. 

and a maximum depth of 90 feet; the average depth is about 60 feet·. 

It has no surface outlet, but its waters escape through the great mass 

of broken stones which retain it and comes to the surface in springs 

of large volume. The nmin landslide which obstructs the valley came 

from the precipitous slope, now covered with forest, to the southwest 

of the northern border of the lake, and still presents the characteristies of what may be termed a landslide scar. At the base of this steep 

slope there is a narrow, curving, trench-like depression, convex to the 

north, on which side it is bordered by the back slope of the mass that 

fell. This treneh has an irregular bottom; and although it is probably 

at no point more than 20 feet above the lake's surface, and is open at 

both ends, it never was occupied as a channel of discharge for the lake 

waters. The surface of the fallen n1ass, which occupies perhaps·30 to 

±0 acres, is irregular and hilly, with elevations that rise from 100 to 

150 feet above the lake's surface. It contains several basins, two of 

which are occupied by ponds fed by springs and by percolation. Middle Lake, about 1 acre in area, is, by aneroid measurement, 20 feet 

lower than Lake vV aha; the lowest point on its rim, where a wagon 

road now tJ·averses it, is 60 feet above its surface and 200 feet above 

the surface of :Niucl Lake, which occupies an adjoining basin. The lastnamed lake has an estimated area of 2 acres, and, like its companion, is 

without surface outlet. 

The lava sheets which form the steep slope of Craig ~Iountain in the 

vicinity of Waha clip northward at a steep angle, and have at least one 

bed of gravel interstratified with them. The presence of a bed of vol-· 

canic dust or of clay charged with that material, although nowhere 

exposed, is indicated by the color of the water in the largest lake. A 

peculiarity of springs that come from beds of volcanic dust is that 

their waters are milky or opalescent in appearance, due to the excessively small particles of volcanic glass helq in suspension. The waters 

of Lake "'Taha have this appearance, and probably are supplied in part 

by springs issuing from deposits of volcani.c dust. The dip of the lava 

sheets in the escarpment rising to the south and southwest of the lake 

is toward the valley it occupies, which, with the presence of sedimentary beds, and probably also of sheets of volcanic dust, is favorable to 

the occurrence of landslides. The only exceptional feature eonnected 

with the landslides at this locality iH that they descended into a narrow valley, so as to completely dam it. The waters rose above the 

dam, but as it is composed mainly if not entirely of rock fragments, 

an eseape by percolation was established before a .. :mrface outlet was 
RUSSELL.) PHYSIOGRAPHY. 81 

reached. On account of the failure of the water to overflow, it could 

not cut down a channel so as to drain the lake, as has occurred in other 

similar instances. The lake has thus been preserved, and is a typical 

illustration of a class of water bodies held by landslides. The larger 

lake differs from the smaller ones near it in that it is retained by a 

landslide which descended into a previously eroded valley, while the 

smaller lakes are of the same type as hundreds of lakelets, swamps, 

and waterless depressions on the surface of fallen rock masses, which 

may be termed true landslide basins. 

The largest spring fed by Lake W aha discharges about 15 cubic feet 

of water per second, which is now conducted into a ditch and used for 

irrigation. A fall of several hundred feet could be made available for 

this water, and it might then be used for power; in fact, a small mill 

was forme1:ly turned by it. This and other plans for utilizing the 

water-among them, the. supplying of Lewiston-have been considered by engineers. The main difficulties developed by the investigations are the loose condition of the natural dam and the precipitous 

character of the borders of the lake, which render it impracticable to 

greatly increase its size. 

TOPOGRAPHY OF THE LEVEL l?LATEAUS. 

There are certain features in the relief of the level plateaus underlain by the Columbia River lava, such, for example, as the Uniontown 

Plateau and the country in the vicinity of Pullman, Garfield, and elsewhere in Washington, which merie attention. The plateaus referred 

to, it will be remembered, are covered with a sheet of residual soil, 

usually from 50 to 100 or more feet thick, and are not smooth plains, 

but nearly everywhere exhibit well-marked variations in relief. tn 

traveling over them one crosses a seemingly endless succession of hills 

and valleys which have differential elevations of, in general, from 50 to 

150 or 200 feet. The topography is undulating, the hills forming convex elevations with steep sides, and the valleys forming concave basins. 

A marked feature is the absence or extreme rarity of basins without 

outlets, such as sinkholes. It is evident from the gradients of the 

valleys, notwithstanding they are gentle, that if ra:ln water could be 

held at the surface of the soil a complete system of streams would be 

formed and lakes would be rare or entirely absent. The valleys, however, in cross section have rounded bottoms, and in most instances are 

without stream channels. The convex slopes of the hills merge by 

insensible gradations into the concave curves of the troughs between 

them. The hills and vales alike are composed of fine, rich soil, and 

no rock fragments attract attention, except in rare instances, where 

the hills are unusually precipitous. 

The character of the relief, however, may perhaps be indicated more 

cle'lrly by saying that it is such as stream erosion gives to regions comIRR 5:3-01--6 
82 GEOLOGY, ETO., OF NEZ PERCE CO., IDAHO.-PART I. [No. 53. 

posed of soft rocks where weathering is rapid, but it has lost all of 

the small features due to the work of creeks, brooks, and rills .. The 

stream courses have long been abandoned, and the movement of the 

soil on the bordering slopes, the beating of rain, the influences of frost, 

vegetation, etc., have subdued and to a great extent obliterated the 

1ninor inequalities due to stream erosion. It is evident from the nature 

of the larger elements in the topography, especially from the gradients 

of the shallow valleys, which are such as would furnish complete drainage in case water could be held at the surface, that streams at one time 

meandered over these nearly level plateaus. The valleys, however, 

have long been abandoned as avenues of drainage, and may be said to 

be slowly crumbling to ruin. One reason for this change, but perhaps 

not the most important, seems to be that rock disintegration and decay 

have been in excess of transportation, and such a depth ofporous soil 

and subsoil has been produced that the rain water is entirely absorbed 

by percolation and evaporation, thus robbing it of the power to corrade. With the increase in depth of residual material there very likely 

was a decrease in rainfall which hastened the disappearance of surface 

streams. 

As already stated, the sedimentary layers and beds of volcanic dust 

between the sheets of Columbia River lava in numerous instances con- · 

tain abundant impressions of the leaves of Tertiary plants, and it 

seems safe to assume that the last and highest lava sheet was poured 

out before the close of that period. This being so, the lava plateaus 

have been exposed to the atmosphere throughout Pleistocene and 

Recent times, and have experienced the climatic changes which gave 

character to the Glacial epoch. In harmony with this conclusion is 

the fact that the surfaces of the plateaus have been exposed to the air 

throughout the immense length of time that witnessed the excavation 

of the neighboring canyons. There is 9,bundant evidence to show that 

glaciers did not reach the Nez Perce region· or the Palouse country, 

although they did exist during the Glacial epoch on the Cascade 

Mountains to the west and on the Rocky Mountain ranges to the east. 

It may reasonably be assumed that the atmospheric changes which 

gave origin to extensive glaciers on the mountains gave to the intervening lowlands a cold and humid climate. Since the glaciers disappeared or have been greatly reduced in size, the clhnate of the lava 

plateaus has become warmer and less humid. In a general way, then, 

it seems safe to refer the erosion of the level lava plateaus which gave 

them their moderately rough surfaces to the Glacial epoch, when precipitation was greater than now. The decrease in the size of the 

streams and the disappearance of all but the larger ones may be correlated with the climatic cha:nges which followed the Glacial epoch and 

which still continue; With the decrease in the volume of the streams 

rock deca:y continued, and the depth of fine soil has become so great 
RUSSELL.] PHYSIOGRAPHY. 83 

that all of the rainfall, although now amounting- to probably 30 or 35 

inches a year on the higher plateaus, is absorbed, and mechanical erosion is nil. 

SOLUTION BASINS. 

Among the minor physiographic features of the Nez Perce region 

should be noted certain shallow depressions, without outlets, in the 

surfaces of the plateau remnants between the ~treams which have dissected the Columbia River lava. In some instances these depressions 

hold water during the rainy season and become transformed into 

small lakes; but in summer their beds are dry, and pm~haps are 

coated with an incrustation of alkaline salts or are traversed by a network of shrinkage cracks. Shallpw basins of this character occur on 

the level plateau about 4 miles west of "T aha, and can be seen to 

advantage from the neighboring hills. In similar situations on the 

Clarkston Plateau, near where it merges with the northeast slope of the 

Blue Hills, are other shallow basins a few rods across, the bottoms of 

which are grass covered and do not retain water so as to form lakelets. 

In one of these basin& a few trees are growing, but the surrounding 

plateau is a prairie. On the Camas Prairie also, to the southwest of 

Denver, several small sheets of water can be seen from Cottonwood 

Butte and other neighboring elevations. While several of these are 

artificial ponds, there is at least one natural lake in a depression in the 

generally level surface. Other shallow basins of a similar nature, 

which are wet and swampy during the winter or are grass covered and 

possibly have trees growing in them, will be recalled by those who are 

fan1ilar with the region referred to. 

These basins are of the nature of the sinkholes or shallow depressions 

common in limestone regions, and owe their existence mainly to the 

dissolution of the rocks through the agency of rain water, which escapes 

through :fissures or other openings in their floors. After a depression 

has been produced by the enlarging of a fissure, the subterranean 

channels may become closed, by the washing into them of the surface 

soil, so as to prevent the downward escape of water, in which ease 

the sinkhole will be changed to a lake. In humid regions such lakes 

are frequently perennial, but where the rainfall is small, or where 

there is an alternation of wet and dry seasons, they are likely to be 

ephemeral. 

It should be remembered that the solution basins referred to occur 

on flat areas, and they should not be confounded with the somewhat 

similar and much more comn1on basins produced by landslides. 

TORRENT-BUILT LEVEES. 

In the Nez Perce region, as in many countries having a small 

mean annual · rainfall, there are occasional torrential rains, locally 

termed cloudbursts. These occur at long intervals, and are local in 
84 GEOLOGY, ETC., OF NEZ PERCE CO., ID.A.HO.-PART I. [~o. 53. 

their extent. Frequently they leave records of their occurrence which 

endure for many years. Among the most conspicuous changes produced by the rush of water down steep declivities which had previously become covered with a sheet of residual soil and angular rock 

fragn1ents, are alluvial cones and parallel ridges formed of angular 

stones left on the sides of the ephemeral torrents. The alluvial cones 

frequently have channels on their surfaces, showing that the water 

flowed over them in streams which at times bifurcated, or abandoned 

well-formed channels with raised borders and built new ones. The 

most striking results, however, are where streams originated on 

declivities of 10 to 15 and in places 20 to 30 degrees angle, and built 

parallel embankn1ents of angular stones from a few inches to 2 or 3 

feet in height. In these instances the swift streams were overloaded 

with coarse material, which was deposited partly on their bottoms but 

principally on their borders, forming levees which tended to confine 

the water to narrow channels. A typical example of these torrentbuilt levees was observed on the sides of the canyon of Captain John 

Creek, where in 1897 there occurred a local storm which gave birth to 

streams that continued less than an hour, on slopes of 20 to 35 degrees 

angle. The channels of these streams are still clearly defined, in fact 

are almost as fresh as when the waters left them. Their width varies, 

but in general they are from 1 to 3 feet across, and the sharp-crested 

ridges of stones piled up on their sides are from 24 to 30 inches high, 

with a width at the base but little greater than their height. The 

stones in the ridges are angular, and are of all sizes up to 5 inches (in 

some instances 8 inches) in diameter. In some cases a torrent broke 

through one of its embankments and sent off a distributary, which also 

built a well-defined pair of levees of angular stones. These parallel 

ridges are of the same general character 'as the levees of alluYialdepositing rivers, as, for example, the Mississippi in its lower course, 

but are sharp crested and are formed of angular stones with large 

spaces between them. The temporary torrents were evidently overloaded with debris, except in their swift central portions. As soon as 

the water which had gathered into a stream began to spread, it lost 

velocity as well as depth; the stones previously swept along were 

dropped, and an embank1nent was formed which tended to confine the 

current within narrow lilnits and thus enable it to build up its embankments. The small ]evees referred to occur on slopes where previously 

there were no stream channels. In the natural waterways the floods 

were high during the storm referred to.. Captain John Creek, which 

in summer is a brook across which one can step, increased in a few 

minutes to a roaring flood charged with the branches and trunks 

of trees and thick with mud from 8 to 10 feet deep, _sweeping along 

large bowlders in its path. The previously formed flood plain, which 

was under cultivation in at least one locality, was largely washed away · 
Rt:SSELL.] PHYSIOGRAPHY. 85 

and new deposits of coarse gravel were laid down. Similar floods 

have occurred in neighboring canyons, as has been noted in the case 

of Asotin Creek, and torrent-built levees like those described can be 

seen on some of the steep slopes along the course of Grande Ronde 

River. 

In Part II of this paper, published as Water-Supply and Irrigation 

Papm~ No. 54, w~ll be found discussions of the water supply and the 

economic geology of the Nez Perce region, also tables of elevations 

in the county (Appendix A), and notes concerning Portland cement 

(Appendix B). 

[For index, see end of Part II, Water-Supply Paper No. 54.] 

0