History of Snake River Canyon 

Indicated by Revised Stratigraphy 

of Snake River Group Near 

Hagerman and King Hill, Idaho

GEOLOGICAL SURVEY PROFESSIONAL PAPER 644-F
History of Snake River Canyon 

Indicated by Revised Stratigraphy 

of Snake River Group Near 

Hagerman and King Hill, Idaho

By HAROLD E. MALDE

With a section on PALEOMAGNETISM

By ALLAN COX

SHORTER CONTRIBUTIONS TO GENERAL GEOLOGY

GEOLOGICAL SURVEY PROFESSIONAL PAPER 644-F

Lavaflows and river deposits contemporaneous with 

entrenchment of the Snake River canyon indicate 

drainage changes that provide a basis for improved 

understanding of the late Pleistocene history

UNITED STATES GOVERNMENT PRINTING OFFICE, WASHINGTON : 1971
UNITED STATES DEPARTMENT OF THE INTERIOR 

ROGERS C. B. MORTON, Secretary

GEOLOGICAL SURVEY 

W. A. Radlinski, Acting Director

Library of Congress catalog-card No. 72-171031

For sale by the Superintendent of Documents, U.S. Government Printing Office

Washington, D.C. 20402 - Price 40 cents (paper cover)

Stock Number 2401-1128
CONTENTS

Abstract ___________________________________________

Introduction.______________________________________

Acknowledgments --..______-__-____--__-_---__-_____

Age of the McKinney and Wendell Grade Basalts. _____

Correlation of lava previously called Bancroft Springs

Basalt_________________________________________

Equivalence of pillow lava near Bliss to McKinney 

Basalt.._________________________

Page

Fl

2

2

2

Late Pleistocene history of Snake River_ _ 

Predecessors of Sand Springs Basalt. 

Wendell Grade Basalt-________

McKinney Basalt. ____---__---__

Bonneville Flood.________________

Conclusion___________________________

Paleomagnetism, by Allan Cox_________

References cited._____________________

page 

F9

13

14

16

18

19

19

20

ILLUSTRATIONS

FIGURE 1. Index map of Idaho showing area discussed.______________________________________________________

2. Chart showing stratigraphy of Snake River Group..____________________________._____--___-_-_-_-.

3. Geologic map of area between Hagerman and King Hill.___________________________________________

4-7. Photographs showing:

4. Pressure ridges of McKinney Basalt.______________________________________________________

5. Scabland surface of McKinney Basalt_________________________________________-___---__-_-

6. Boulder of Melon Gravel on McKinney Basalt______________________________________________

7. Gravel under McKinney Basalt.._________________________________________________________

8. Geologic map of area southeast of King Hill._____________________________________________________

9. Photograph of canyon-filling McKinney Basalt at Bancroft Springs._________________________________

10. Geologic sections across former canyon of Snake River____-______-_______-____-_______-_--_-_------

11. Maps of area between Hagerman and King Hill showing late Pleistocene drainage changes. ___________

12. Photograph showing canyon fill of Sand Springs Basalt ___________________________________________

13. Diagram showing directions of remanent magnetization of selected basalts from the Snake River Group.

Page 

F2

2

3

4

5

5

5

6

8

10

12

15

20

TABLES

TABLE 1. Altitudes and gradients of surface of McKinney Basalt southeast of King Hill..._________-__________-

2. Selected pebble counts of gravel pertaining to ancestral river history between Hagerman and King Hill..

3. Log of water well 6S-13E-6dcl at Bliss...____________________________________________________

4. Log of water well 6S-13E-5ddl, three-quarters of a mile east of Bliss. ______________________________

Page 

F9

13

14

16

m

SHORTER CONTRIBUTIONS TO GENERAL GEOLOGY

HISTORY OF SNAKE RIVER CANYON INDICATED BY REVISED 

STRATIGRAPHY OF SNAKE RIVER GROUP NEAR HAGERMAN

AND KING HILL, IDAHO

By HAROLD E. MALDS

ABSTRACT

A discovery that debris left by the Bonneville Flood (Melon 

Gravel) overlies McKinney Basalt about 200 feet above the 

Snake River near King Hill requires that the stratigraphy of 

the Snake River Group be revised. In former usage, the McKinney Basalt and its immediately older companion, the Wendell 

Grade Basalt, were considered on the basis of equivocal field 

relations to be younger than the Melon Gravel and were assigned 

to the Recent. These lava flows are here reclassifled as Pleistocene. The Bancroft Springs Basalt, which consists of both subaerial lava and pillow lava in a former Snake River canyon, 

was previously separated from the McKinney but is now combined with the McKinney. Accordingly, the name Bancroft 

Springs Basalt is here abandoned.

This revised stratigraphy is first described from geomorphic 

relations of the McKinney Basalt near King Hill and is then 

discussed in the light of drainage changes caused by local lava 

flows during entrenchment of the Snake River.

Near King Hill, a former Snake River canyon was completely 

filled by McKinney Basalt at the place called Bancroft Springs, 

but the depth of this lava in the next several miles of the canyon 

downstream (along a route that approximately coincides with 

the present canyon) steadily decreased. This ancestral geomorphology is inferred from the former canyon route and, also, 

from the continuity in gradient of the McKinney lava surface 

downstream from Bancroft Springs.

The drainage history recorded by various lava flows and river 

deposits of the Snake River Group indicates that the McKinney 

and Wendell Grade Basalts erupted after the Snake River 

canyon had reached its present depth of about 500 feet. The 

Snake River of that time, as far downstream as Bliss, flowed 

approximately along its present route. The Wood River of that 

time, however, skirted the north flank of Gooding Butte and 

joined the ancestral Snake at a junction, now concealed by lava, 

north of the present canyon about 3 miles west of Bliss. From 

that place the former Snake River canyon, also now concealed 

by lava, continued west to Bancroft Springs and thence along 

a route close to the present canyon to King Hill.

To become entrenched in a canyon 500 feet deep, the Snake 

River downstream from Hagerman became progressively more 

incised while its upstream route was pushed south in several

earlier canyons by intermittent lava flows. Distinctive gravel 

deposits help to establish the episodes of progressive canyon 

cutting and to determine the routes of ancestral drainage, including the former position of the Wood River. As canyon 

cutting continued, springs began to emerge where lavrs had 

filled the earlier canyons. When the Snake River canyon eventually attained its approximate present depth, the Wendell 

Grade Basalt erupted near Shoshone and, as several tcngues, 

spread west to the canyon rim opposite Hagerman. One tongue 

crossed the future route of the Wood River, and another covered 

an upland area of Sand Springs Basalt that had previously 

reached the canyon floor at Hagerman.

The McKinney Basalt then erupted from McKinney Butte 

northeast of Bliss and spread southward as a subaerial flow, 

covering part of the Wendell Grade Basalt. It filled the ancestral 

Wood River canyon and the Snake River canyon of that time 

west of Bliss as far downstream as King Hill. The resulting 

dam of lava impounded a deep lake, which extended upstream 

in the canyon beyond Hagerman. Copious amounts of the McKinney spilled into this temporary lake and produced pillow 

lava. About 2 miles west of Bliss, pillow lava 500 feet thick 

completely fills the former canyon and is protected by rfmrock 

of the subaerial McKinney Basalt. From Bliss, the pillow facies 

extends upstream as far as the McKinney rimrock about 5 

miles.

Eruption of the McKinney Basalt diverted the Wood River 

to a course along the southeast edge of this lava flov. The 

temporary lake that was dammed by McKinney Basalt vest of 

Bliss spilled along the south edge of the McKinney and began 

to cut the present canyon of the Snake River. By the time of 

the Bonneville Flood of 30,000 years ago, tlie new canyon west 

of Bliss;had reached its approximate present size and depth, for 

it was able to carry the computed flood discharge. PhysiogTaphic 

change along the canyon since this catastrophic event h&s been 

minor.

Paleomagnetic measurements show that the direct'on of 

remanent magnetism is the same for both the McKinney Basalt 

and the Bancroft Springs Basalt of former usage (each sampled 

in 'Several places at three outcrops). Although it is possib1 ** that 

the earth's magnetic field had this direction at different times, 

this equivalence suggests that these outcrops are part of the 

same lava flow.

Fl
F2 SHORTER CONTRIBUTIONS TO GENERAL GEOLOGY

INTRODUCTION

In current studies by the U.S. Geological Survey 

along the Snake River from Hagerman to King Hill 

(fig. 1), one of the difficult stratigraphic problems in 

dividing the youngest rocks has been to determine the 

position of two local lava flows, the McKinney Basalt 

and its immediate predecessor the Wendell Grade 

Basalt, with respect to the Melon Gravel that was deposited by the catastrophic late Pleistocene Bonneville 

Flood. Until recently, these lava flows were interpreted 

on the basis of equivocal field relations to be younger 

than the Melon Gravel and were assigned to the Recent 

(Malde and Powers, 1962, p. 1217). Now, however, the 

McKinney and Wendell Grade Basalts are known to 

be older than the Melon Gravel and are accordingly 

dated as Pleistocene. Moreover, the McKinney is now 

believed to include lava previously classified separately 

as Bancroft Springs Basalt (Malde and Powers, 1962, 

p. 1216). (The revised age of the McKinney Basalt was 

briefly mentioned by Malde, 1964, footnote, p. 204.) 

This report explains the geologic and paleomagnetic 

evidence by which this revised stratigraphy has been 

learned and then applies this knowledge to a new analysis of late Pleistocene history along this segment of 

the Snake River.

117° 116- 114° 113° 112° 111° 

50 100 MILES

FIGURE 1. Index map of Idaho showing area discussed.

The analysis of the river history deals with the entrenchment of the Snake River canyon ani with the 

inferred routes of ancestral canyons that am recorded 

by various lava flows and river deposits of the Snake 

River Group. Thick deposits of pillow lava a few miles 

downstream from Hagerman are explained as a facies 

of the McKinney Basalt that accumulated in a temporary lake 500 feet deep; the lake was impounded by 

another part of the McKinney Basalt in the Snake 

River canyon of that time. This pillow lava, though 

previously known to be older than the Melon Gravel 

(part of the Bancroft Springs Basalt as used by Malde 

and Powers, 1962, p. 1216), has not been heretofore explained from a knowledge of the canyon history.

The former and present classifications of the Snake 

River Group are compared in figure 2.

ACKNOWLEDGMENTS

My work along the Snake River has beer shared by 

Howard A. Powers, who first opened my eyes to the 

role played by local lava flows in modifying river history. He did much of the geologic mapping on which 

my present understanding of the Snake F;ver Plain 

depends. We have spent so much time togetHr discussing the perplexing matters that led to this report, both 

at the outcrops and in the office, that many of the ideas 

presented here are as much his as mine. E^en so, especially because the features to be described stem mainly 

from geomorphology rather than volcanology, I take 

responsibility for whatever faulty deductions are found 

in these pages.

AGE OF THE McKINNEY AND WENDELL GRADE 

BASALTS

Surveys between the years 1954 and 1961 established 

that the McKinney Basalt erupted from McKinney

Former classification

ti

*

I

1CO '3

CL,

&

McKinney Basalt

Wendell Grade Basalt

Melon Gravel 

* Bancroft Springs Basalt

Sand Springs Basalt

Crowsnest Gravel

Thousand Springs Basalt

Sugar Bowl Gravel

Madson Basalt

Present classification

g

g

§

V

|

.2

V

h

&

Lava flows

Melon Gravel 

McKinney Basalt

Wendell Grade Basalt

Sand Springs Basalt

Crowsnest Gravel

Thousand Springs Basalt

Sugar Bowf Gravel

Madson Basalt

*Name now abandoned

FIGURE 2. Stratigraphy of Snake River Group.
HISTORY OF SNAKE RIVER CANYON NEAR HAGERMAN AND KING HILL, IDAHO F3

Butte 8 miles northwest of Gooding and that the 

Wendell Grade Basalt came from Notch Butte 4 miles 

south of Shoshone (Malde and others, 1963). As these 

events were then understood, the McKinney Basalt 

flowed south toward the Snake River, then west in the 

upland north of the canyon rim, and finally cascaded 

from the upland to present river level near King Hill;

the Wendell Grade Basalt flowed west and reached the 

canyon rim at several places near Hagerman (fig. 3). 

Exposures 5 miles northeast of Hagerman along the 

Malad River (which is the local name for the lower 

reach of the Big Wood River) showed that the McKinney overlies the Wendell Grade. Because both the 

McKinney and the Wendell Grade lavas retain rough

115-00' 114-45'

EXPLANATION

Thousand Springs

McKinney Basalt

Pillow lava in black

Madson Basalt y

Older rocks of Quaternary 

and Tertiary age

Paleomagnetic 

sample

Water well

X 538 

Locality of pebble

count

Number refers to sample 

dismissed in the text

Crowsnest Gravel

^ 43-00'

42°45'

FIOUBE 3. Generalized geologic map of area between Hagerman and King Hill. Geology modified from Malde, Powers, and 

Marshall (1968). Base from U.S. Geological Survey Twin Falls quadrangle. 1955-63, and Hailey Quadrangle. 1955-62.
F4 SHORTER CONTRIBUTIONS TO GENERAL GEOLOGY

surfaces that are only partly mantled by windblown 

surficial material (fig. 4) in contrast to contiguous 

older lavas for which the original surface roughness 

has been almost entirely obliterated and because of 

erroneous interpretations explained below, the McKinney and Wendell Grade were assigned to 

the Recent.

A discovery made in 1.962 by George Stone, who was 

then collecting petrographic samples with Howard 

Powers, showed that the McKinney Basalt, and hence 

the Wendell Grade Basalt, is older than the Melon 

Gravel and is therefore of Pleistocene age, in spite 

of its youthful appearance. The decisive geology was 

found along the Union Pacific Railroad 4 miles southeast of King Hill at a site 200 feet above the Snake 

River. There, the Bonneville Flood scoured McKinney 

Basalt to make the intricate anomalous topography 

known as scabland (fig. 5), and it left well-rounded 

boulders of Melon Gravel on the eroded McKinney,

some of which were more than 5 feet long (fig. 6). 

Prior to this discovery, I had recognized stream erosion 

of nearby McKinney Basalt no higher than 125 feet 

above the river and thought that this erosion could 

have been produced by overflow where the McKinney 

had dammed the Snake. My. other previous interpretations about the relation of the McKinney Basalt to 

Melon Gravel, which I will now summarize, were also 

wrong. I had erred in two places.

First, along the Snake River 3 miles southeast of 

King Hill, the McKinney Basalt overlies basaltic cobbles and boulders formerly interpreted to be Melon 

Gravel (Malde and Powers, 1962, p. 1217) the only 

local gravel deposit then known to consist solely of 

basaltic debris. The length of outcrop of this gravel 

amounts to less than a mile, much of it being obscured 

by talus from the overlying basalt, but sections of the 

gravel several feet thick are locally well exposed 

where protected by an overhang of lava (fig. 7). I now

FIGURE 4. Pressure ridges of McKinney Basalt, which are partly covered with surficial material. View is north toward

McKinney Butte from the railroad 5^ miles east of Bliss.
HISTORY OF SNAKE RIVER CANYON NEAR HAGERMAN AND KING HILL, IDAHO F5

FIGURE 5. Scabland surface of McKinney Basalt about 200 

feet a'boye the Snake Hirer 4 miles southeast of King Hill. 

Part of the basalt was removed by the Bonneville Flood, and 

the remaining lava was extensively corraded, rounded, and 

polished.

discern subtle differences between this deposit and typical Melon Gravel. The basaltic gravel under the McKinney is subangular, rather well sorted, more cobbly 

than bouldery, and lacks interstitial sand. In contrast, 

the nearby Melon Gravel is rounded, poorly sorted, 

more bouldery than cobbly, and contains much basaltic 

sand. Because of the unequivocal evidence found by 

Stone and Powers (that is, boulders of Melon Gravel 

lying on McKinney Basalt), this gravel below the 

McKinney must be older than the Melon Gravel.

FIGURE 6. Basalt boulder of Melon Gravel more than 5 feet 

long on McKinney Basalt 175 feet above the Snake River 4 

miles southeast of King Hill. Another boulder, nearly buried 

by surficial sand, is at the right.

FIGURE 7. Basaltic gravel under McKinney Basalt on right 

bank of the Snake River 3 miles southeast of King Hill. 

Pieces of the gravel are frozen in the base of the lava.

Second, the terminus of the McKinney Basalt near 

King Hill, in the area known as The Pasture (fig. 8), 

was formerly interpreted as several small tongues of 

lava that had descended shallow troughs in the Melon 

Gravel (Malde and Powers, 1962, p. 1217), but the 

physiography is now understood as subdued bars of 

Melon Gravel on the McKinney.

Observations by Powers (in Malde and Powers, 1962, 

p. 1217), about the stratigraphic position of the Wendell Grade Basalt with respect to Melon Gravel, in 

the light of present knowledge, were also deceptive. 

Powers found a place 2 miles east of Hagerman where 

Wendell Grade Basalt had cascaded from the canyon 

rim onto landslide debris. Because this landslide closely 

resembles another landslide 2-3 miles northwest that 

overlaps Melon Gravel (Malde, 1968, fig. 19), Powers 

decided that the Wendell Grade Basalt was also younger 

than Melon Gravel. From present evidence, this conclusion is false. The McKinney Basalt clearly overlies 

Wendell Grade Basalt on the Malad River, as previously mentioned, and both are older than the Melon 

Gravel.

CORRELATION OF LAVA PREVIOUSLY CALLED 

BANCROFT SPRINGS BASALT

Study since 1962 indicates that lava which fills a 

former canyon of the Snake River at Bancroft Springs, 

5 miles south-southeast of King Hill (fig. 8), and which 

also forms the north rim of the present canyon as far 

upstream as the mouth of Malad Canyon, is McKinney 

Basalt as originally defined by Stearns (1936). The 

name, Bancroft Springs Basalt, which was previously 

applied to this lava (Malde and Powers, 1962, p. 1216),
F6

R, !0 E. 

43°00'

SHORTER CONTRIBUTIONS TO GENERAL GEOLOGY

115-10' R. 11 E.

T. 5 S.

42°55'

T, 6 S.

3 MILES

FIGUBE 8. Generalized geologic map of area along Snake River souheast of King Hill showing inferred route of former canyon 

of Snake River, which is filled; with MlcKinney Basalt. Cross sections (A-A' to K-K') are shown in figure 10. See map 

explanation on facing page.
HISTORY OF SNAKE RIVER CANYON NEAR HAGERMAN AND KING HILL, IDAHO F7

EXPLANATION

*

Glenns Ferry Formation

Contact

Inferred route of Snake 

River before eruption 

of McKinney Basalt

FIGURE 8. Continued.

is hereby abandoned for reasons given in this discussion. Also, pillow lava between Bliss and Malad Canyon, which was formerly included in the Bancroft 

Springs Basalt, is here identified as a facies of the 

McKinney. This new assignment of the pillow lava is 

discussed in the next section, and the assignment is then 

incorporated in subsequent remarks on the river history. Paleomagnetic measurements compatible with this 

correlation are discussed in a separate section by Allan 

Cox.

Assignment of the canyon-filling lava at Bancroft 

Springs to the McKinney Basalt stems from my liberation from faulty concepts about the age of the McKinney 

and from a better comprehension of certain features of 

the ancestral physiography.

The cany on-filling lava forms an imposing basalt 

cliff 300 feet high at Bancroft Springs and is obviously 

older than the present canyon (fig. 9). The lava is also 

older than the Melon Gravel, which in places litters the 

lava surface with boulders as large as 15 feet. (See also, 

Malde, 1968, fig. 21.) Until George Stone and Howard 

Powers determined that a downstream lobe of McKinney Basalt that cascaded from the upland is also older 

than the Melon Gravel, I thought that this lobe represented an eruption younger than the lava at Bancroft 

Springs and that it reached the Snake River after the 

present canyon was cut. (The downstream lobe occupies 

the area called The Pasture in fig. 8.) This idea evidently was a misconception. I now infer that the lava at 

Bancroft Springs and the downstream lobe were formed 

concurrently by the eruption of McKinney Basalt and 

that both are older than the present canyon. The correlation of these bodies of lava cannot be proved from 

available outcrops because any possible link between 

them along the canyon is concealed by Melon Gravel. 

Nevertheless, their former connection can be inferred 

from the route of the ancestral canyon and, also, from 

the continuity of the surface gradient of the lava that 

extends downstream from Bancroft Springs. These 

features can be traced in a series of geologic sections 

drawn across the path of the ancestral canyon (fig. 10).

In section A-A', the former canyon is shown to be 

completely filled with McKinney Basalt, which at one 

time undoubtedly extended across the area of the present 

canyon to the small remnant of lava on the southwest 

side. The former canyon, with a floor at an altitude of 

about 2,575 feet, is intersected by the present canyon at 

Bancroft Springs (section D-D') and probably continues northwest into an area covered by Melon Gravel. 

Sections F-F' through /-/' show the possible presence 

of concealed remnants of the canyon-filling lava and 

indicate the inferred gradient of the former canyon 

floor. Beyond section /-/', the former canyon is again
F8 SHORTER CONTRIBUTIONS TO GENERAL GEOLOGY
HISTORY OF SNAKE RIVER CANYON NEAR HAGERMAN AND KING HILL, IDAHO F9

intersected by the present Snake River, and the McKinney Basalt is underlain by basaltic gravel, as previously mentioned. Finally, the former canyon approximately coincides with the present canyon near section 

K-K' where the McKimiey reaches present river level.

The surface gradient of lava between Bancroft 

Springs and The Pasture can be measured from the 

cross sections and from the geologic map. For convenience, the altitudes and the indicated gradients are given 

in table 1. Because the original surface of the lava is 

preserved, except for a few feet of local stripping by 

flood erosion, the present altitudes closely indicate the 

original gradient. North of section />-/>', the lava surface descends rather uniformly at a gradient of about 

2 percent, and the projected surface corresponds with 

the surface of the McKinney Basalt at section G-G'. 

Thereafter, the surface gradient descends more 

gradually.

In summary, the former canyon was deeply filled by 

McKinney Basalt at Bancroft Springs and was filled 

only to shallow depth downstream at The Pasture; the 

lava surface probably was graded continuously between 

these two localities. The differences in thickness of the 

McKinney Basalt between Bancroft Springs and The 

Pasture appear to be a consequence of the steep gradient 

of the lava surface. At The Pasture, McKinney Basalt 

in the canyon was joined by a lava cascade that spilled 

simultaneously from the adjacent upland.

EQUIVALENCE OF PILLOW LAVA NEAR BLISS 

TO McKINNEY BASALT

Another stratigraphic problem that has been clarified 

by studies made since 1962 concerns the age and origin 

of pillow lava that extends discontinuously upstream 

along the Snake River canyon from below Bliss to the 

mouth of Malad Canyon. The outcrops of pillow lava 

reach from present level near Bliss (about 2,650-ft.

TABLE 1. Altitudes and gradients of surface of McKinney Basalt 

southeast of King Hill

Relation to previous section

Section Altitude (feet) Difference in 

altitude (feet)

Intervening 

gradient (percent)

A- A'... 

B-B' ...

_ D-D' 

E-E' 

F-F'.

i-r . J-J'.

K-K'

2, 915 . 

2,885 

2,845 

2,800 

2,750 

(2, 700) 

2,650 

2,625 

2,600 

2,575 

2,540

30

40

45

50

50

50

25

25

25

35

1. 2

1.7

1.8 

1. 9 

2.0 

2.0 

1.0 

1. 0 

1.0 

. 6

Interpolated.

alt.) to places 500 feet higher and can be accounted for 

only by lava that entered a deep lake. Such a lake could 

have formed only behind a lava dam.

Russell (1902, p. 113-116) recognized pillow lava 

in the canyon at Bliss and compared these outcrops 

with subaqueous lavas in the Hawaiian Islands. Stearns 

(1936, p. 439-441), using the now-abandoned name of 

Bliss Basalt, considered the pillow lava as possiHy a 

subaqueous phase of the McKinney Basalt. (See also, 

Stearns and others, 1938, p. 76-78). His stratigraphic 

placement of the McKinney, however, was incorrect. 

Malde and Powers (1962, p. 1216) assigned the pillow 

lava to a supposed early lava from McKinney Butte, 

the Bancroft Springs Basalt, but did not explair the 

canyon history that accounts for the deep lake in which 

the pillow lava was deposited.

As determined from petrography and geographic 

proximity, two possible sources of the pillow lava exist: 

McKinney Butte and Gooding Butte (fig. 3). The pillow lava, together with lava from both these vents, is 

fine-grained porphyritic plagioclase-olivine basalt, having plagioclase laths as much as 7 millimeters long that 

are clustered with olivine crystals 1-2 millimeters across. 

The petrography of these lavas differs from that of all 

others nearby. Gooding Butte, however, can be rejected 

as a potential source, because its time of eruption must 

have been earlier than the entrenchment of the ancestral 

Snake River to the depth represented by the pillow lava; 

the much younger McKimiey Butte is therefore the only 

feasible source. This conclusion is derived from rather 

detailed knowledge of the canyon history, as described 

in the next section. Briefly, from an analysis of drainage 

history based on the effect of local lavas during canyon 

entrenchment, I infer that a dam of McKinney Basalt 

filled a former canyon of the Snake River and that the 

pillow lava accumulated simultaneously by the spilling 

of McKinney Basalt into the resulting lake. This interpretation can be easily tested by drilling about 3 miles 

west of Bliss, where the lava dam of McKinney Basalt 

is inferred to be concealed.

LATE PLEISTOCENE HISTORY OF SNAKE RF'ER

The latest episodes of geologic history along the Snake 

River between Hagerman and King Hill, which ar?, recorded by the various lava flows and river deposits of 

the Snake River Group, are portrayed on a series of 

paleogeologic sketch maps (fig. 11). The existing and inferred geologic features by which each of these maps 

has been constructed will be discussed in turn. The maps 

should be compared with the present geology shown in 

figure 3.
SOUTHWEST 

K

3000' -i

H

3000' -i

2800' 

2600' -

Qal

nm|f

NORTHEAST 

K'

i- 3000

- 2600

H'

Qm

- 2800

- 2600

2600' -
2600' -

1

3000' -

2600' -

? 1 

~--\ Qbs Qsb Qmk Qsb Qmk Qfb Qal

~"~ ^\ Qmk Q3^= * ' ^~ 

 ^QTg Qm snake / -7""^ 

^ ~--^ ^ River 1 / ,/

\ /^QTg?(Talus cover)

)'

- 3000

^oUU

- 2600

3000

2 MILES

FIGURE 10. Geologic sections across former canyon of the Snake River southeast of King Hill. For location of sec
F12 SHORTER CONTRIBUTIONS TO GENERAL GEOLOGY

A. Sand Springs Basalt from 

vent 50 miles east fills ancestral canyon of Snake River 

and terminates at Hagerman 

(H) on floor as deep as present (2,800-ft alt). Ancestral 

Wood River along north edge 

of Gooding Butte (G) joins 

Snake River west of Bliss (B)

B. Wendfll Grade Basalt from 

vent 20 miles east terminates 

as several tongues that reach 

canyon edge 400 feet above 

Snake River near Hagerman 

(H). Snake River diverted 

by Sand Springs Basalt occupies new canyon along south 

edge of lava plain

C. MeKinney Basalt from McKinney Butte (M) fills ancestral Wood River canyon, dams 

Snake River at confluence, and 

flows west to King Hill (KH). 

Basalt that spills south into 

temporary lake forms pillow 

lava (indicated by X marks) 

to local thickness of 500 feet

D. Bonneville Flood occupies 

new canyon along south edge 

of Me Kinney Basalt west of 

Bliss, reaches depth of 300 feet 

at King Hill (KH), and overflows McKinney rimrock at 

confluence with former canyon. Wood River follows 

southeast edge of McKinney 

Basalt

10 MILES

FIGURE 11. : of area between Hagerman and King Hill showing late Pleistocene drainage changes caused by local lava

flows.
HISTORY OF SNAKE RIVER CANYON NEAR HAGERMAN AND KING HILL, IDAHO F13

EXPLANATION

Area of Bonneville Flood

McKinney Basalt

A', pillow lava concealed

by temporary lake

Older rocks of Quaternary 

and Tertiary age

Contact

Edge of canyon or upland

Dashed where covered by 

Bonneville Flood

Rivers

Ancestral rivers dotted 

where concealed

Lava butte 

FIGUBE 11. Continued.

PREDECESSORS OF SAND SPRINGS BASALT

The eruption of Sand Springs Basalt occurred after 

the Snake River had become entrenched to its present 

depth (fig. 11 A). Before then, the entrenchment had 

been interrupted at various times by lava flowr that 

had caused minor diversions of the river. The first of 

these older lavas, Madson Basalt, came from an er.stern 

source and reached nearly as far west as King Hill. It 

occupied a shallow ancestral valley of the Snake River 

at about 3,000 feet in altitude at the approximate 

latitude of Gooding Butte. This valley, which if now 

mainly concealed north of the present mouth cf the 

Big Wood River (Malad Canyon), passed just south 

of Bliss (where it is intercepted by the present canyon) and then turned west. Gravel under the Madson 

Basalt is exposed in Malad Canyon (fig. 3) anc1 is a 

type that differs from the porphyry-rich gravel that is 

now carried to the Snake River Plain by the Big TVood 

River from central Idaho (Howard Powers, written 

commun., May 19, 1967). The lack of porphyry in this 

gravel suggests that the Wood River at that time was 

probably along the north edge of the Madson Basalt. 

The Sugar Bowl Gravel that overlaps the terminus of 

the Madson Basalt (locality 510 in fig. 3) resembles the 

modern gravel of the Big Wood River (locality 538) 

by being rich in porphyry and other rocks from central 

Idaho (table 2).

The Madson Basalt pushed the ancestral Snake River 

south to the latitude of Hagerman. Lava from Gooding 

Butte, one of the sources of the Thousand Springs Basalt, then covered the eastern part of the Madson, restricted the Wood River to a course north of Gooding 

Butte, occupied the site of the Snake River that was 

then east of Hagerman, and diverted the Snake into

TABLE 2. Selected pebble counts, in percent, of gravel pertaining 

to ancestral river history between Hagerman and King Hill

Locality No... _ ....... ........

Source chiefly in central Idaho:

Source nearby:

Latite... -------------

Rhyolite _ ... ... 

Source indeterminate:

Chert-... . .. 

1

2

O

o 

«

a

E?

02

.. 610

.. 22

.. 13

1

.- 41

7

2

2

.. 279

 O

FJ +*

O <§ f] 58

CM®°c

202*

o

531

M

14iS

73

3

M

glX

311

1

1

12

o

632

2

IIM

65

6

14

313

1

1

£

g

O

1513

24H

3

41

10*$

2

71^

281

1

6

a

"3

a

498

31

46

6

9

1

272

O ^

g«

dl

S bo |a

538

iKU.

j

43

2

1

7

372

i This locality is 7 miles southwest of King Hill and 1 mile south of Glennf Ferry. 

' Includes as much as 3 percent fine-grained dark rock, counted as argillite

424-038 O - 71 - 2
F14 SHORTER CONTRIBUTIONS TO GENERAL GEOLOGY

a course still farther south at the approximate latitude 

of 42°45'. Gravel southeast of Hagerman on this Thousand Springs Basalt (locally 531) reflects material that 

was transported by the ancestral Snake River and is 

more than 400 feet above the present Snake River. The 

gravel evidently closely marks the depth of canyon 

cutting at that time.

As entrenchment by the Snake River progressed, the 

base of the Thousand Springs Basalt from Gooding 

Butte in the former canyon east of Hagerman was exposed and began to discharge spring water. This discharge initiated the small spring-fed tributary (Billingsley Creek) that parallels the east wall of the canyon. The springs at the base of the basalt range in altitude from 3,100 to 3,150 feet.

A younger part of the Thousand Springs Basalt from 

vents about 20 miles east of Hagerman was then deposited on the floor of a shallow canyon 100 feet below 

the south edge of the basalt from Gooding Butte. This 

canyon was at the latitude of 42°45', as previously mentioned. Ground water carried by basalt in this former 

canyon is thought to account for the large discharge 

at Thousand Springs, 5 miles southeast of Hagerman 

(Nace and others, 1958, p. 45-48). Because of this 

younger Thousand Springs Basalt, the ancestral Snake 

River was pushed a little farther south to the position 

of the concealed canyon sketched as a dotted line in 

figure 1L4.

The canyon was next partly filled with about 50 feet 

of Crowsnest Gravel, which overlaps the younger part 

of the Thousand Springs Basalt near Hagerman. Along 

Billingsley Creek, the base of this gravel is from 3,050 

to 3,080 feet in altitude, which is 30-80 feet below the 

springs at the base of the basalt from Gooding Butte. 

If the Crowsnest Gravel extended eastward under the 

basalt, the springs would issue from a level equal to 

the base of the gravel. Their absence at this level confirms that the basalt from Gooding Butte is older than 

the Crowsnest Gravel, as the physiographic relations 

already described indicate.

The Crowsnest Gravel southeast of Hagerman (locality 532) closely resembles in composition the gravel 

on the basalt from Gooding Butte (locality 531), and 

this composition reflects nearby sources. The outcrops of 

Crowsnest Gravel downstream near King Hill, however, include a large component transported by the 

ancestral Wood River from central Idaho (locality 513). 

The Crowsnest Gravel near King Hill lies about 200 

feet below the Sugar Bowl Gravel and thus indicates 

the depth of canyon entrenchment by this time.

Canyon cutting then resumed, eventually reaching a 

depth of more than 400 feet at Hagerman (250 ft. below 

Crowsnest Gravel) and probably a comparable depth

near King Hill. In the lava plain southeast of Hagerman, the Snake River canyon was approximately in the 

position it had occupied since eruption of the last Thousand Springs Basalt (dotted line in fig. 11A). From 

Hagerman to Bliss, as indicated by confining outcrops 

of Madson Basalt and older rocks still preserved along 

the canyon rim, the ancestral canyon was approximately 

in its present position. At Bliss it was separated from 

the Wood River canyon on the north by a divide of old 

Quaternary and Tertiary deposits, as recorded in the 

log of well 6S-13E-6dcl (table 3). West of Bliss the 

canyon must have been approximately in the position 

it occupied during the subsequent eruption of McKinney Basalt, as will be explained later.

When the Snake River canyon reached its present 

depth at Hagerman (2,800-ft alt), it was filled as far 

downstream as Hagerman by the Sand Springs Basalt, 

which erupted from a vent 50 miles east. Tl°, narrow 

ancestral canyon is now exposed in profile along the 

present canyon 7 miles southeast of Hagerman (fig. 12). 

In the wide part of the canyon at Hagerman an area 

bounded on the west by weakly consolidated basin 

deposits (older Quaternary and Tertiary) the Sand 

Springs Basalt spread as a thin terminal tongue. (For 

a map of outcrops of Sand Springs Basalt farther 

east, see Malde and others, 1963.)

With emplacement of the Sand Springs Fasalt, the 

geology resembled that shown in figure 11-4.

WENDELL GRADE BASALT

The Wendell Grade Basalt (fig. 11B) ws.s the immediate predecessor of the McKinney Baralt. Both 

display a rough surface of pressure ridges th'vt project 

above a thin cover of surficial material. Glassy skins 

on ropy surfaces of these lavas are locally preserved, 

and the lavas are fresh. (The McKinney Basalt, however, at a single locality 7 miles east of F"ing Hill, 

displays patterned ground, a curious landform characteristic of older weathered basalt and gravel in this 

region; see Malde, 1964, p. 204.)

TABLE 3. Log of water well 6S-lSE-6dcl at Bliss

[From files of U.S. Geological Survey, Water Resources Division Boise, Idaho. 

Alt. 3,620 ft. Assignment of Hthologic units based on map by Malie, Powers, and 

Marshall (1963)]

Material Thickness Depth

(feet) (feet)

Glenns Ferry Formation (Pleistocene and 

Pliocene):

Clay, yellow. ___-. __________ 84 84 

Lava, gray, hard; water at 188 feet 34 118 

Clay, yellow-__----------_------- 92 210

Clay, blue-.-----.-------.------- 52 262

Clay, yellow-----.-----------.--- 147 409

Clay, blue_-------_-------------- 21 430

Clay and black sand_._._____ 22 452

Banbury Basalt (Pliocene):

Lava, black.--.-.---..----------- 40 492

Sand, black___----__--_---------- 3 495

Clay, blue___-_--_--------------- 17 512
HISTORY OF SNAKE RIVER CANYON NEAR HAGERMAN AND KING HILL, IDAHO F15

I

HI

02 

I

at 

|

i 

 §

0=1
F16 SHORTER CONTRIBUTIONS TO GENERAL GEOLOGY

Before the eruption of Wendell Grade Basalt, a thin 

mantle of windblown sand and silt had accumulated 

on the Sand Springs Basalt to form a smoothly rolling 

lava plain. The Snake River had been diverted at a 

place 30 miles upstream from Hagerman by the Sand 

Springs Basalt and had carved a new canyon southeast of Hagerman where the Thousand Springs Basalt 

had previously abutted an upland of basin deposits. 

This part of the Snake River canyon of that time was 

virtually in the position of the present canyon. (Small 

outcrops of Thousand Springs Basalt at the south rim 

of the present canyon are mapped 1-3 miles east of the 

area of fig. 11; see Malde and others, 1963.) Where the 

new canyon intercepted the former canyon 5-7 miles 

southeast of Hagerman, the Sand Springs Basalt had 

been removed. Near Hagerman the Snake River probably followed the west edge of the terminal tongue of 

Sand Springs Basalt, as it does now. Billingsley Creek 

probably was a little deeper than it had been during the 

eruption of Sand Springs Basalt and was flanked on 

the east by landslide and talus debris derived from the 

basalt rimrock. Downstream from Hagerman, the 

canyon probably had become deeper, as indicated by 

outcrops of pillow lava assigned to the McKinney 

Basalt that occur 100 feet lower than the terminus of 

the Sand Springs Basalt.

The Wendell Grade Basalt flowed west as several thin 

tongues on the old lava plain. One tongue crossed the 

future path of the Wood River southwest of Gooding 

Butte, and others opposite Hagerman reached the canyon edge. At least one of these ended as a lava cascade on 

landslide debris along the east wall of Billingsley 

Creek. The preservation of this cascade indicates that 

subsequent erosion from spring discharge along Billingsley Creek has been minor.

McKINNEY BASALT

When the McKinney Basalt erupted from McKinney 

Butte (fig. 11(7), the Snake River canyon from Hagerman to Bliss was as deep as it is now (about 500 ft) and 

occupied its approximate present position. At a place 

about 2 miles west of Bliss, where the only important 

gap in the continuity of the Madson Basalt occurs, I 

infer that the former canyon continued northwest a 

short distance to its confluence with the ancestral Wood 

River and then turned west. The canyon route to the 

west can be approximately located by the presence of 

confining upland areas of older rocks and by the lavafilled canyon intersected at Bancroft Springs (fig. 8). 

Similarly, the route of the ancestral canyon of the 

Wood River north of Bliss can be determined by its 

adjoining uplands (including the divide of older rocks 

under the site of Bliss); its path from the east must 

have been along the north flank of Gooding Butte.

The buried Wood River canyon is evidently encountered in a water well three-quarters of a mile east of 

Bliss, which penetrates a lava fill described in log 6S13E-5ddl (table 4). The bottom of this well is at an 

altitude of about 2,750 feet and probably marks the 

approximate floor of the filled canyon. Howard Powers 

(written commun., May 19, 1967) infers that the confluence of this filled canyon with the ancestral Snake 

River was west of Bliss because no permeable connection exists between the well and pillow lava 100 feet 

lower at Bliss; this is discussed more fully on page F17.

It is unlikely that any lava in the filled canyon of the 

ancestral Wood River came from Gooding Butte. The 

Thousand Springs Basalt from this vent dates from a 

time before the ancestral drainage was deeply entrenched, as previously explained, and the filling of the 

canyon during more than a single eruptive episode 

would have caused diversions of drainage that are not 

recorded by known geologic features. I conclude that 

the ancestral Wood River canyon was filled solely by 

basalt from McKinney Butte, which simultaneously 

descended the Snake River canyon of that time nearly 

as far as King Hill. Most of the McKinney Basalt in 

the ancestral Wood River canyon, and farther west in 

the ancient Snake River canyon, probably is subaerial 

basalt; the flow of river water, which would have favored the formation of pillow lava, probably was 

interrupted early during the eruption of the basalt. 

A few feet of pillow lava locally occurs below subaerial basalt at The Pasture, near the terminus of 

the flow, and some "clay" and "sand" reported in the 

water well east of Bliss may represent basalt that fragmented in water; however, the massive lava fill of McKinney Basalt at Bancroft Springs displays only columnar layers that evidently cooled in air (fig. 9). This 

evidence indicates that Bancroft Springs lies downstream from the site where the McKinney first entered 

and dammed the ancestral Snake River.

TABLE 4. Log of water well 6S-18E-5ddl, three-quarters of a 

mile east of Bliss

[From flies of U.S. Geological Survey, Water Resources Division, Boise, Idaho. 

Alt. 3,270 ft. All beds penetrated are here assigned to McKinney Basalt]

Material Thickness Depth

(feet) (feet)

Clay_ ________ _ ___________-----_- 4 4

Basalt_.____________----_------ - 32 36

Clay_____________ 9 45

Basalt-__-___-_---__----_----------- 11 56

Clay (sloughs)____-_--_________--_--_- 229 285

Clay, blue____________ 10 295

Sand 30 325

Clay _ ------ 83 408

Basalt, hard, black-____________----- 32 440

Clay.. 16 456

Sand rock, water-bearing. ______ _______ 6 462

Clay..... 4 466

Sand, water-bearing_________________ 4 470

Clay, blue____ 35 505

Basalt, sand__________ 12 517
HISTORY OF SNAKE RIVER CANYON NEAR HAGERMAN AND KING HILL, IDAHO F17

As the McKinney Basalt filled the Snake River canyon west of Bliss, a lake formed in the canyon upstream. 

Eventually, the lava dam reached an altitude of 3,150 

feet, thus impounding a lake 500 feet deep that extended 

upstream along the Snake River beyond Hagerman. 

Basalt that reached the lake formed pillow lava, the 

first of it being deposited on old talus that had been 

derived from Madson Basalt (Malde and Powers, 1962, 

p. 1216). Angular pieces of Madson Basalt (not necessarily talus) are also found under the McKinney Basalt 

at The Pasture near King Hill. Much of the basalt that 

became pillow lava probably arrived at Bliss by overflowing the ancestral Wood River canyon when the 

Snake River canyon downstream was already deeply 

blocked by lava. The copious amounts of McKinney 

Basalt that spilled into the temporary lake produced 

the massive subaqueous volcanic features described by 

Stearns (in Stearns and others, 1938, p. 78-80) as the 

"Bliss cone," "brecciated lava," and "dikes."

In the old lava plain southeast of Bliss, subaerial 

McKinney Basalt spread south and covered the Madson 

Basalt as well as some of the Thousand Springs Basalt 

from Gooding Butte and a small part of the Wendell 

Grade Basalt. Some McKinney Basalt on the lava plain 

undoubtedly spilled west into the lake held by the ancestral Snake River canyon, because outcrops of pillow 

lava in the canyon extend upstream along the east side 

as far as the McKinney rimrock (Stearns and others, 

1938, p. 79). Discernible bedding in the .pillow lava 

dips west.

The McKinney Basalt near the canyon rim southeast 

of Bliss has a relatively smooth surface and was formerly mapped separately from lava on the plain 1-3 

miles east, which has a rough surface. (See Malde and 

others, 1963.) Detailed work might show that the smooth 

McKinney is a local physiographic effect produced by 

a mantle of loess, but the two contrasting areas may 

also represent different flows from McKinney Butte 

that were perhaps separated by a considerable span of 

time. Whatever the cause of the local differences, such 

a contrast cannot be recognized west of Bliss, where the 

McKinney surface is uniformly rough. All basalt from 

McKinney Butte is therefore classed as a unit even 

though its eruption may have been prolonged.

The McKinney Basalt west of Bliss, after filling the 

ancestral Snake River canyon, spread south as a subaerial flow over Madson Basalt to the edge of an upland 

formed by older basin deposits. In the gap between 

outcrops of the Madson about 2 miles west of Bliss, 

which marks the former canyon, the subaerial McKinney evidently rests on the pillow lava facies, which 

completely fills the former canyon to a depth of 500 

feet. Although continuous exposures of pillow lava in

the former canyon have been found no more than 250 

feet above the canyon floor, the subaerial McKinney 

rimrock at the east edge of this ancestral canyon is 

separated from the Madson Basalt below by 25 fee* of 

pillow lava, which reaches 500 feet above the canyon 

floor that is, to an altitude of 3,150 feet. Identical 

pillow lava at a comparable height underlies McKiimey 

rimrock 2 miles southeast of Bliss. The height of these 

outcrops implies that the dam of McKinney Basalt is 

concealed about 3 miles west of Bliss, near the buried 

confluence of the ancestral Wood and Snake Rivers, as 

shown in figure 11(7. If the present canyon had then 

existed downstream from Bliss, it necessarily would 

have been filled with McKinney Basalt, thus providing a 

means for the spread of the McKinney to its two outcrops now preserved on the south rim (fig. 11Z>). No 

sign of such a lava fill in the present canyon car be 

found; as explained in the discussion which follows, the 

present canyon west of Bliss surely formed after 

McKinney time.

Aspects of ground water support the inference that 

the ancestral Wood and Snake Rivers joined a short 

distance west of Bliss and indicate that the area betw^n 

the Snake and the buried Wood River canyon is a drainage divide consisting of rather impermeable basin 

deposits (older Quaternary and Tertiary). These conclusions are deduced from a lack of springs in the McKinney pillow lava, whereas most other basalts of the 

Snake River Group in this area are notable aquifers. 

Small springs that appear to issue from pillow lava 

along the canyon wall southeast of Bliss, at altitrdes 

between 2,825 and 2,875 feet, are possibly supplied by 

water that migrates along a concealed surface of Fanbury Basalt. (See log of well 6S-13E-6dcl and map by 

Malde and others, 1963.) Stearns also thought that this 

meager flow of spring water could not represent discharge from the pillow lava (Stearns and others, 1938, 

p. 164), but he attributed the discharge to water carried by the Madson Basalt. Because the former valley 

filled with Madson Basalt is intercepted upstream by 

the present Wood River in Malad Canyon, wher1* it 

yields a phenomenal discharge of about 1,000 cubic feet 

per second at Malad Springs (Nace and others, 1958, 

p. 55-58), the amount of water carried by the Madson 

Basalt in the downstream area of pillow lava must 

be negligible. In summary, a lack of springs in the 

pillow lava indicates that this lava is isolated fr'om 

ground water in the buried ancestral Wood River canyon by an impermeable barrier. Thus, the talus-covered 

canyon wall southeast of Bliss, which was previously 

mapped mostly as pillow lava (Malde and others, 1963), 

surely consists of t>lder Quaternary and Tertiary basin 

deposits (fig. 3). The necessary corollary is that the dry
F18 SHORTER CONTRIBUTIONS TO GENERAL GEOLOGY

pillow lava in the ancestral Snake River canyon connects with lava in the filled canyon of the Wood Elver at 

a somewhat lower altitude at a concealed junction west 

of Bliss.

A small amount of ground water, however, issues 

from the canyon-filling McKinney Basalt at Bancroft 

Springs, which is near the terminus of the flow. Although Bancroft Springs connects with the present 

Wood River via the filled ancestral Wood River canyon 

and also with the Snake River near Bliss via the canyon 

fill of McKinney pillow lava, its discharge is curiously 

small. Howard Powers (written commun., Sept. 25, 

1967) suggested the following explanation. For the McKinney Basalt at Bancroft Springs to have solidified 

as columnar subaerial layers, its dam upstream must 

have been virtually watertight, a circumstance that may 

persist today. That is, under present conditions, the 

water carried by the Snake River flows readily down the 

existing channel, and the water pressure on the concealed lava dam is not great enough to cause substantial 

leaks. Also, contributions to Bancroft Springs from the 

Big Wood River must be small because this stream maintains its flow across the lava plain and seemingly loses 

little water by seepage.

BONNEVILLE FLOOD

After the eruption of McKinney Basalt, lake water 

impounded by the lava dam west of Bliss spilled along 

the south edge of the McKinney lava, where it abutted 

the upland of basin deposits, and thus established the 

Snake River in its present course (fig. 11Z>). As noted by 

Stearns (in Stearns and others, 1938, p. 77), this overflow descended 700 feet in 7 miles (actually more nearly 

13 miles) and must have cut rapidly into the soft basin 

deposits. In the reach from 3 to 10 miles west of Bliss, 

a canyon about 1 mile wide exposed Madson Basalt 

(locally overlain by Sugar Bowl Gravel) below McKinney rimrock. When downcutting reached a depth 300 

feet below the north rim, the river was confined to a narrow inner gorge in Tertiary basalt and eventually 

reached an additional depth of 200 feet (Malde and 

others, 1963). By the time of the Bonneville Flood of 

30,000 years ago (Malde, 1968), the canyon had virtually attained its modern dimensions.

Two remnants of McKinney Basalt are preserved on 

the south rim of the new canyon. One of these, 11 miles 

west of Bliss, is subaerial basalt at the altitude of 

McKinney rimrock on the north side (fig. 10, section 

A-A'). The other remnant, 6 miles west of Bliss, consists only of basalt boulders 2-3 feet in diameter, which 

are slightly below the altitude of McKinney rimrock 

on the north, 1 mile distant. These boulders obviously 

match the distinctive McKinney lithology and must

have been deposited near the edge of the McKinney 

Basalt during initial overflow of the temporary lake. 

Their size demonstrates the transport power of the 

turbulent water discharged from the lake.

The Wood River that had been blocked by the McKinney Basalt was diverted into its present route (the 

Malad River) along the southeast edge of the McKinney 

lava. Downcutting by the ancestral Wood Piver along 

this marginal path required removal of thick layers 

of basalt and need not have been especially rapid until 

erosion reached the base of the Madson Basalt, 200 feet 

below the lava plain. The rate of cutting must have then 

increased, primarily because the soft basin deposits below the Madson were easily erodible, but partly because streamflow was thereby augmented by discharge 

from Malad Springs (p. F17). It is remarkable that the 

present Malad Canyon upstream from the base of the 

Madson Basalt (the site of Malad Springs) abruptly 

narrows and becomes shallow, whereas the canyon in 

basin deposits downstream to its mouth, 2 ir iles distant, 

rapidly widens and deepens. Even so, Malad Canyon 

is short and narrow when compared with the Snake 

River canyon of equivalent age west of Bliss. This difference is probably a function of contrasts in river gradients, discharge, and the resistance of rocks to erosion. 

As explained below, the comparatively Irrge canyon 

west of Bliss was not a circumstance of the Bonneville 

Flood.

The Bonneville Flood deposited large amounts of 

basaltic debris, particularly in wide parts of the canyon (Melon Gravel of fig. 3). For a short distance downstream from the mouth of the Malad River, however, 

the flood debris contains gravel derived frcm the headwaters of the Big Wood River in central Idf.ho (locality 

498). This fact alone, even if other geologic relations 

were lacking, would suggest that the Bonneville Flood 

occurred after diversion of the Wood River and was, 

therefore, younger than the McKinney Basalt. (This 

gravel was previously discounted as pertaining to the 

age of the McKinney because I assumed it was younger 

than the Bonneville Flood.) The basaltic flood debris 

elsewhere along the canyon, although mostly produced 

by spectacular erosion near Twin Falls T5 miles upstream from Hagerman, partly represents local smoothing of canyon walls by flood erosion. Such smoothing by 

the flood, however, had little effect on the previous size 

of the canyon, for calculations of flood discharge and 

canyon capacity indicate that the canyon had already 

attained its approximate present dimensions by the 

time of the flood. The movement of boulders 10 feet in 

diameter 9 miles west of Bliss, for instance, demonstrate 

a velocity of floodwater that required a crnyon of the
HISTORY OF SNAKE RIVER CANYON NEAR HAGERMAN AND KING HILL, IDAHO F19

present dimensions to accommodate the Bonneville 

Flood at its known height and discharge (Malde, 1968, 

p. 34,46).

Part of the erosional effect of the Bonneville Flood 

presumably was the removal of some McKinney pillow 

lava that had survived during the cutting of the canyon 

west of Bliss and also the removal of any lacustrine deposits that may have formed at the head of the temporary lake that was dammed by the McKinney Basalt. 

Such lake deposits, if they had been present, would have 

been mainly in a narrow part of the canyon upstream 

from Hagerman and therefore would have been in the 

direct path of the flood water.

In descending the Snake River canyon, the Bonneville 

Flood overtopped rimrock of Sand Springs Basalt 250 

feet above the canyon floor south of Hagerman (Malde, 

1968, p. 32). Floodwater again overtopped the canyon 

rim at Bancroft Springs and partly covered the toe of 

the McKinney Basalt with Melon Gravel.

Since the Bonneville Flood, the Snake River canyon 

has changed little and still plainly bears marks of this 

catastrophic event.

CONCLUSION

The foregoing account of the volcanic eruptions and 

associated drainage changes that produced the present 

Snake River canyon between Hagerman and King Hill 

leaves some matters still incompletely explained.

Not all the ground water, for example, that emerges 

as springs from lava flows along this part of the canyon 

exactly fits the changing pattern of drainage outlined 

here, even though the positions of most springs are 

understandable in these terms. The cause of the small 

discharge from McKinney1 Basalt at Bancroft Springs, 

in particular, will remain a mystery until drilling penetrates the concealed lava dam west of Bliss and reveals 

its character.

A progressive increase in the roughness of lava flows 

that erupted at various time during entrenchment of the 

Snake River corresponds with their decreasing age (the 

older flows being smooth and the younger ones being 

rough), but the McKinney Basalt is locally an exception. Smooth McKinney rimrock southeast of Bliss, 

which must be related to pillow lava in the canyon 

below, contrasts with rough McKinney elsewhere.

In a larger sense, the slightly weathered appearance 

of the McKinney Basalt (and the Wendell Grade 

Basalt) must be reconciled not only with the 30,000 

years that has elapsed since the Bonneville Flood but 

also with whatever additional time was required to cut 

the Snake River canyon west of Bliss. Even though 

the McKinney locally displays patterned ground, a

mark of the Pleistocene, its physiography is that of a 

lava flow which has erupted recently. Thus, together 

with the Wendell Grade Basalt of similar appearance, 

the McKinney provides an example of how little geomorphic change might be shown by other upper Pleistocene lavas in this region.

Preservation of the cascade of Wendell Grade Basalt 

along the canyon wall east of Hagerman is quite unexpected, especially because of the erosion that would 

be anticipated at neighboring sites of springs. Perhaps, 

however, this lava cascade is not at all anomalous; 

perhaps it demonstrates clearly enough that erosion 

along canyon walls rimmed with basalt even a canyon 

supplied with local springs is slow.

PALEOMAGNETISM

By ALLAN Cox

Paleomagnetic measurements can help to determine 

whether isolated outcrops of lava may represert the 

same eruption because they accurately indicate the direction of the earth's magnetic field when the lava 

cooled. For example, studies of historic lava flows on 

Hawaii have established that the mean direction of 

remanent magnetization of an individual flow is nearly 

parallel to the earth's magnetic field of its tine, as 

recorded at magnetic observatories close to tho- site 

where the lava solidified. These results show that the 

angular difference between the measured direction of 

magnetization of a flow and the observed direction of 

the earth's field, which may be regarded as the- irreducible error of the paleomagnetic method, is not more 

than 4° if at least eight oriented samples are collected 

from each flow. Multiple sampling is necessary because 

directions of magnetization of individual samples1 commonly vary from 5° to 15°.

Remanent magnetization is useful for stratigraphic 

purposes, because the geomagnetic field that controls 

the magnetization changes direction with time. If 

plotted on a sphere, or on a spherical projection, the 

changing pole of the earth's magnetic field determined 

at a given locality appears as a point that traces out 

an irregular path around some mean direction. Observatory records show that the velocity of motion and the 

amplitude of the swing of the magnetic pole vary 

widely from place to place. A shift in pole position as 

great as 40° has occurred during a mere 200 yei-.rs at 

some observatories, whereas the change has been less 

than 2° at others. On the basis of such data, it is obvious 

that the path traced out by the shifting magnetic pole 

may cross and recross itself many times during an interval as long as 100,000 years. This conclusion is of con-
F20 SHORTER CONTRIBUTIONS TO GENERAL GEOLOGY

siderable importance in applying paleomagnetism to 

stratigraphy.

Two outcrops of volcanic rock that differ in direction 

of magnetization by several tens of degrees, for instance, 

must have cooled several hundred years apart, if we 

assume that the ancient geomagnetic field changed at 

the maximum rate observed today. A time interval of 

10,000 years or 100,000 years would also be consistent 

with such measurements.

On the other hand, because the geomagnetic field can 

coincide with a former position, two outcrops of volcanic rock that have the same direction of magnetization may have cooled at different times, but such a 

coincidence is very unlikely. It is more probable that the 

outcrops solidified simultaneously.

The directions of magnetization of several basalt 

flows in the Snake River Group are plotted in figure 13. 

Each point is the direction of magnetization of an oriented sample after partial demagnetization in an alternating magnetic field to remove the effects of possible 

lightning strikes (Cox, 1960; Graham, 1961). The samples for a particular flow represent several outcrops 

and show that the direction of magnetization is the same 

throughout an individual basalt unit. For example, the 

samples from the Sand Springs Basalt are from three 

outcrops that span a distance of 22 miles. At the 95- 

percent confidence level, the mean directions of magFIGTTRB 13. Directions of remanent magnetization of selected 

basalts from the Snake River Group: Thousand Springs 

Basalt (open'circles) ; Sand Springs Basalt (horizontal bars) ; 

Bancroft Springs Baslalt of former usage (vertical bars; , 

and McKinney Basalt (solid circles). All directions are 

plotted on the lower hemisphere of an equal-area projection.

netization of these three outcrops are the same. On the 

other hand, samples from different basalts (compare 

Sand Springs and Thousand Springs) are magnetically 

distinct.

For the Bancroft Springs Basalt of former usage 

and the McKinney Basalt, however, both of which were 

sampled at three outcrops (fig. 3), the directions of 

magnetization overlap; at the 95-percent confidence 

level, their mean directions are not significantly different. From the foregoing remarks about the meaning 

of magnetic data, this result suggests that the Bancroft 

Springs and McKinney are almost surely the game flow. 

However, coincidence in direction of magnetization, as 

already explained, does not rule out the remote possibility that the Bancroft Springs and McKinney are 

different. Moreover, the measured direction of magnetization is close to the direction of an axial dipole 

field (Cox and Doell, 1960) that occurs more commonly 

than any other direction in young rocks, as determined 

in many regions. Even in the Snake River Plain, two 

other basalts (not shown in fig. 13 because they are 

remote from the area described here) have nearly the 

same direction of magnetization as the Bancroft 

Springs and McKinney. Coincidence in the direction of 

magnetization is clearly a necessary conditior, but not 

a sufficient condition, for establishing equivalent age. 

Nonetheless, when these paleomagnetic results are combined with the knowledge of geology given earlier in 

this report, the conclusion is virtually inescapable that 

the Bancroft Springs Basalt and the McKinney Basalt are identical.

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Cox, A. V., 1960, Anomalous remanent magnetization of basalt: 

U.S. Geol. Survey Bull. 1083-E, p. 131-160 [196:].

Cox, A. V., and Doell, R. R., 1960, Review of paleomagnetism: 

Geol. Soc. America Bull., v. 71, no. 6, p. 645-768.

Graham, K. "W. T., 1961, The re-magnetization of a surface outcrop by lightning currents: Royal Astron. Soc. Geophys. 

Jour., v. 6, no. 1, p. 85-102.

Malde, H. E., 1964, Patterned ground in the western Snake 

River Plain, Idaho, and its possible cold-climrte origin: 

Geol. Soc. America Bull., v. 75, no. 3, p. 191-207.

 1968, The catastrophic late Pleistocene Bonne^ille Flood 

in the Snake River Plain, Idaho: U.S. GeoL Survey Prof. 

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Malde, EL E., and Powers, H. A., 1962, Upper Cenozoic stratigraphy of western Snake River Plain, Idaho: Geol. Soc. 

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Malde, H. E., Powers, H. A., and Marshall, C. H., 1963, Reconnaissance geologic map of west-central Snake River Plain, 

Idaho: U.S. GeoL Survey Misc. Geol. Inv. Map 1-373.

Nace, R. L., McQueen, L S., and Van't HuL, Arthur, 1958, Records of springs in the Snake River valley, Jerome and 

Gooding Counties, Idaho, 1899-1947: U.S. Geol. Survey 

Water-Supply Paper 1463, 62 p.
HISTORY OF SNAKE RIVER CANYON NEAR HAGERMAN AND KING HILL, IDAHO F21

Russell, I. C., 1902, Geology and water resources of the Snake 

River plains of Idaho: U.S. Geol. Survey Bull. 199, 192 p.

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alcoves along the Snake River in southern Idaho: Jour. 

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Stearns, H. T., Crandall, Lynn, and Steward, W. G., 19"8, Geology and ground-water resources of the Snake River Plain 

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