ANIAKCHAK CRATER, ALASKA PENINSULA. 

By wALTER R. SMITH. 

The discovery or" a gigantic crater northwest of Aniakchak Bay (see fig. 11) closes 

what had been thought to be a wide gap in the 

extensive series of volcanoes occurring at 

irregular intervals for nearly 600 miles along 

the axial line of the Alaska Peninsula and the 

Aleutian Islands. In this belt there are more 

active and recently active volcanoes than in all 

the rest of North America. Exclusive of those 

on the west side of Cook Inlet, which, however, belong to the same group, this belt contains at least 42 active or well-preserved 

volcanoes and about half as many mountains 

suspected or reported to be volcanoes. The 

locations of some of these mountains and the 

hot springs on the Alaska Peninsula and the 

Aleutian Islands are shown on a map prepared 

by G. A. Waring. 1 Attention has been called 

to these volcanoes for nearly two centuries, 

but a record of their activity since the discovery of Alaska is far from being complete, 

and an adequate description of them as a 

group has never been written. Owing to 

their recent activity or unusual scenic beauty, 

some of the best known of the group are 

Mounts Katmai, Bogoslof, and Shishaldin, 

but there are many other beautiful and interesting cones and craters. 

Aniakchak Crater (Pls. XLI, XLII) was discovered in August, 1922, 2 by a United States 

Geological Survey party, in charge of R. H. Sargent, topographic engineer, in the course of a 

reconnaissance topographic and geologic survey 

of the country west of the Aleutian Mountains 

between Wide and Aniakchak bays. The first 

evidence of an ancient volcanic eruption in the 

district was observed 30 miles northeast of the 

crater, in the form of thin deposits of fine ash 

concentrated in small depressions on the hillsides. As the work progressed southwestward 

1 Waring, G. A., Mineral springs of Alaska: U.S. Geol. Survey WaterSupply Paper 418, pl. 1, 191'?. 2 It has recently been reported that W. W. French, an engineer, 

and party visited the crater in July, 1921, but no report of the discovery was made at that time. 

the deposits of volcanic ash became more numerous and the material coarser. Along Ray Creek, 

18 Y2 miles from the crater, pieces of scoria and 

fine ash had consolidated and subsequently 

been cut by the stream until vertical walls 

stand 6 to 12 feet high on both banks. (See 

Pl. XLIII, A, B.) The floor of the broad 

valley of Cinder River was found to be entirely 

covered by volcanic ejecta, but the source of 

the material was not discovered until the 

summit of Elephant Mountain was occupiljd 

by Mr. Sargent and the writer. Prior to the 

view of the crater, h0wever, locations on the 

topographic map of a group of peaks in the 

distance had assumed the form of a circle, but 

the reason of the . arrangement was not suspected. 

Aniakchak Crater is 24 miles northwest of 

Aniakchak Bay, approximately in the central 

part of the Alaska Peninsula, on the divide 

between the Pacific Ocean and Bering Sea. 

Although there are no trails, the district is 

easily accessible from either side of the penin-:-

sula. Ania.kchak River, the largest stream on 

the peninsula flowing into the Pacific Ocean, 

rises within the crater and breaks through the 

east side of the rim in a narrow and picturesquely castled canyon which has been named 

" The Gates" (Pl. XLIII, 0), from two long, 

nearly symmetrical mountain spurs that diverge from the canyon, one on each side of the 

river, and inclose the upper valley. The 

crater is nearly circular in outline and has a 

maximum diameter of 6%' miles and a minimum 

diameter of a little over 5%' miles. The lowest 

part of the crater floor is 1,100 feet above sea 

level and contains Surprise ·Lake, a body of 

water with an area of 2 square miles. The 

walls are well preserved and rise almost vertically in places to altitudes of 1,200 to 3,000 

feet above the bottom of the crater. A large 

truncated cinder cone, the SU¥J.mit of which is 

2,200 feet above Surprise Lake, occupies the 

south-central part of the area inclosed within 

the crater rim. 

139 
140 SHORTER CONTRIBUTIONS TO GENERAL GEOLOGY, 1923-1924. 

The crater was first mentioned without a 

name by R. F. Griggs 3 in a book that was 

printed shortly after the return of Mr. Sargent's party. Under the name "Old Crater" 

N 

report 4 on the geology of the district. In a 

chronologie account of observed volcanic activity in Alaska, Grewingk 5 gives the geographic position of V eniaminof volcano as 

f ~ 

0 

c 

1"' 

c1-

oO 

Oi\=c::>===isi===:::::EIO:==:==:==:ii'IS====::::i20 Miles 

o Kak I. 

FIGURE 11.-Sketch map showing location of Aniakchak Crater, Alaska Peninsula. 

its position· is indicated on the map of Alaska 

published by the Survey in 1923. A very brief 

description of the crater was included 1n a 

3 The Valley of Ten Thousand Smokes, p. 65, footnote, 1922. 

• Smith, W. R., and Baker, A. A., The Cold Bay-Chignik district: 

U.S. Geol. Survey Bull. 755, p. 157, 1924. 

6 Grewingk, Constantin, Beitrage zur Kentniss der orographischen 

und geognostischen Beschaffenheit der Nord-west Kuste Amerikas, 

mit den anliegenden Inseln (with geologic and other maps), St. Petersburg, 1850. 
U. S. GEOLOGICAL SURVEY PROFESSIONAL PAPER 132 PLATE XLI 

ANIAKCHAK CRATER, ALASKA PENINSULA 
U, S. GEOLOGICAL SURVEY PROFESSIONAL PAPER 132 PLATE XLII 

RELIEF MAP OF ANIAKCHAK CRATER AND VICINITY, ALASKA PENINSULA 
U. S. GEOLOGICAL SURVEY PROFESSIONAL PAPER 132 PLATE XLIII 

A 

B 

A, B. EXPOSURES OF VOLCANIC ASH ON RAY CREEK, ALASKA PENINSULA 

C. "THE GATES" OF ANIAKCHAK CRATER, ALASKA PENINSULA 
U. S. GEOLOGICAL SURVEY PROFESSIONAL PAPER 132 PLATE XLIV 

A. BLACK NOSE, ALASKA PENINSULA 

B. MOUNT CHIGINAGAK, ALASKA PENINSULA 
ANIAKCHAK CRATER, ALASKA PENINSULA. 141 

latitude 56° and longitude 158° to 159°. 

This position is rather close to that of Aniakchak Crater, which is latitude 56° 45' and longitude 158° 9', but from the short account given 

it is quite evident that Grewingk meant the 

volcano known at present as Veniaminof, latitude 56° 17' and longitude 159° 15', and not 

Aniakchak Crater. Although the Russian 

scientists and travelers recorded many interesting and valuable observations regarding the 

volcanoes of Alaska Peninsula, they made no 

mention, so far as known to the writer, of the 

immense crater discovered in 1922. It is quite 

probable that some of the Russian fur hunters, 

or perhaps a prospector or trapper of more 

recent days, came across the crater but either 

failed to recognize it as such or failed to report 

it. Inquiries were made of the inhabitants of 

Chignik, the nearest settlement, and of local 

trappers, all of whom knew nothing about the 

crater. The present paper is based on observations Inade by the writer during a few hours. 

Time was not available to determine the age of 

the crater or the exact manner in which it was 

formed. 

The observer at a distance would not suspect 

the existence of a huge crater within the cluster 

of rather gentle peaks which are separated from 

the other mountains of the district by broad 

level areas. The valleys of Meshik and Aniakchak rivers west of the crater are in general 

less than 200 feet above sea level. The boldest 

portion of the outer rim of the crater is along 

the east side of the mountains, where cliffs rise 

abruptly from the tributary valleys of Aniakchak and Meshik rivers. Over these precipitous cliffs many streams cascade from the 

glaciers near the summit of the rim. One of 

these streams has a vertical fall of at least 1,000 

feet. The west and north sides of the rim 

slope more gently away from the crater and 

are covered to a great depth by ash and cinders. 

Gullies 30 feet deep on these slopes do not 

expose the solid rock beneath but show rudely 

stratified layers of ash and large lava and scoria 

boulders 4 feet and less in diameter. 

The panorama of the crater (Pl. XLI) conveys a rather poor conception of its magnitude, 

owing to the large size of the area inclosed 

within the proportionally low rim and to the 

absence of an object of known dimensions. 

However, the greatest length of Surprise Lake 

visible in the photograph is 2 ~ miles, and the 

33372°-25--10 

small cones near the upper end of the lake rise 

about 200 feet above the floor of the crater. 

The summit of the large cinder cone is 4~ 

miles from the point at which the picture was 

taken; the mountains beyond the cone are 6 

miles from the observer. The inner wall is 

abrupt-at places nearly vertical-and so far 

as known it can not be easily descended except 

just north of The Gates. A view of Black 

Nose (Pl. XLIV, A), the peak immediately 

south of The Gates, taken from a cinder ridge 

within the crater, gives an idea of the steepness 

of parts of the inner wall. The south side of 

the crater rim affords a gathering ground for 

the snow, and here vigorous alpine glaciers 

have been formed on the steep slopes. Evidence of slumping along the inner wall was not 

noted except for several talus slopes in the 

canyon 'bf Aniakchak River and near the base 

of Black Nose. The circumference of the crater 

is nearly 19 miles. The rim is broken in two 

places-the sharp notch through which Aniakchak River flows and a depression on the west 

side which · was not seen in 1922 but has been 

reported by M. W. Taylor, of Seattle, who 

visited the crater in 1923. On the south side 

the highest point on the rim is 4,200 feet above 

sea level and 3,000 feet above Surprise Lake. 

This peak and several others close by were 

obscured by clouds at the time the photograph 

reproduced in Plate XLIV was taken. The 

greater part of the crest of the rim is not jagged, 

although Black Nose and several other sharp 

peaks rise above the average altitude, which is 

approximately 3,000 feet. 

Along the north and northeast sides the inner 

wall is partly covered by detritus, but in the 

few exposures seen the rocks appeared to be 

layers of pink and black lava, probably obsidian, 

several hundred feet thick, overlying a lightcolored quartz diorite. Most of these exposures are inaccessible and were not closely 

examined, but a specimen of the quartz diorite 

was tak-en on the outer wall northeast of the 

crater. Exposures in the cliffs along the canyon 

and near the bottom of Black Nose consist of 

nearly horizontal sedimentary rocks, chiefly 

very massive gray sandstone. In the lower 500 

feet the rocks exposed in the canyon are 

abundantly fossiliferous; the greater part of the 

fossils belong to several species of Aucella that 

are characteristic · of the Naknek formation, 

of Upper Jurassic age. From. a distance the 

summit of Black Nose apparently consists of 
142 SHORTER CONTRJBUTIONS TO GENERAL GEOLOGY, 1923-1924. 

lava, but the upper portion may be in part 

sedimentary rock, presumably of Tertiary age. 

The unconformity and the contrast in lithology 

between the rocks of the two kinds can be 

seen in Plate XLIV, A. Although the high 

mountains forming the south side of the rim 

were not closely examined, they probably consist entirely of sedimentary rocks, the greater 

part of which are Upper Jurassic. A rugged 

spur north of the north wing of The Gates is 

composed of very coarse agglomerate or tuff 

similar to that overlying large areas in the 

vicinity of Aniakchak and Kejulik bays. Most 

of the large and small boulders that make up the 

agglomerate are angular, but some are rounded. 

Individual blocks attain 16 feet in diameter and 

display the darker shades of red, green, and 

gray. Many of the boulders are black, and all 

of them show a scoriaceous texture. 

The area of · the bottom of the crater is 

approximately 30 square miles. The entire 

floor is covered to an unknown depth by black 

and gray scoria ranging in coarseness from very 

fine material to pieces several feet in diameter. 

About one-third of the floor is level; around the 

base of the large cone ridges of cinders, 200 to 

800 feet high, radiate toward the crater wall. 

The formation of the cones and the position 

of the material within the rim are undoubtedly 

the results of activity subsequent to the major 

eruptions that produced the great crater. 

The later activity probably decreased the 

original depth of the crater by partly filling it 

with cinders, The upper 800 feet of the large 

cone is remarkably circular and well preserved. 

It is thought to be formed entirely of cinders, 

as no lava was observed on the ridges around 

the base. The summit is truncated and may 

be slightly depressed. An attempt was made 

to reach the top, but traveling over the loose 

material is wearisome, and the attempt was 

given up late in the evening with the realization that a trip of 10 miles to camp was yet to 

be made. The small cones near the head of the 

lake were not examined. Toward the west 

side of the crater, 5 miles from the writer's 

nearest point of observation, another small 

cone, which was not caught by the camera, 

could be seen by aid of a field glass. Near this 

cone a curious bowl-shaped deposit of white 

material, probably formed by hot mineral 

waters, stands out in contrast to the surrounding black scoria; which appeared to be very 

coarse at that locality. Only a rough estimate 

of the dimensions of the bowl can be given, 

but it is at least 200 feet in diameter. 

Surprise Lake, in the northeastern part of 

the crater, is irregular in outline and has a 

maximum length of 2 ~ miles and average 

width of three-fourths of a mile. It covers an 

area of nearly 2 square miles, but the bluishgreen color of the water indicates that the 

depth is not great. The lake may have formerly 

c9vered a much larger area, before ·the river 

had deepened its channel through the canyon, 

but terraces or high-water marks could not 

be detected on the wall at the few places examined. An ill-defined bench occurs well up 

on the sides of the cinder cone, however, but 

the bench is not continuous nor sufficiently 

well preserved to consider it an ancient lake 

shore. A small circular lake or pool several 

hundred feet higher than Surprise Lake is 

situated at the base of Black Nose. Although 

a stream of considerable size flows from the 

lake and unites with Aniakchak River just 

inside The Gates, the lake has no affiuents and 

must derive its supply of water from the snow 

fields and glaciers by seepage through the 

cinders.· 

The narrow notch in the crater's rim 

through which Aniakchak River flows has undoubtedly been deepened by the erosive power 

of the stream, which is very turbulent as it 

emerges through The Gates. The break in 

the wall, however, is thought to be caused by 

a rift, which may extend across the crater and 

acco~nt for the depression · on the west side. 

No evidence of relative vertical displacement 

of the opposite sides of the canyon was noted. 

The photograph of The Gates (Pl. XLIII, 0), 

taken through the haze from a point 5 ~ miles 

down the valley, does not do justice to their 

profoundly impressive beauty. Several terraces formed by the river in the ash and pumice 

can be seen in the foreground. The crater can 

. be entered through The Gates without difficulty 

on the south side of the river. The stream 

was too swift to be waded within the canyon 

when it was visited in August, and an attempt 

to pass through on the north side of the river 

terminated by climbing a precipitous cliff 

1,600 feet ·high. 

Only the east side of the crater was visited, 

but the country to the north could be seen 

from Jaw Mountain and the southeaBt outer 
ANIAKCHAK CRATER, ALASKA PENINSULA. 143 

wall from Pinnacle Mountain. All the valleys 

of the surrounding country for many miles are 

covered by thick deposits of ejecta from the 

crater: The material consists of fine ash, 

fragments of black and pink lava, and gray, 

black, and red pumice. The greatest ·observed 

thickness is exposed in the steep banks of Lava 

Creek. The stream has developed many 

beautiful terraces and its present bed, west of 

Jaw Mountain, is cut, perhaps 50 feet, into a 

deposit of black volcanic glass, as reported by 

Mr. Sargent. The glass or obsidian is 10 miles 

from the nearest point on the crater's rim, and 

whatever its source it was extruded before the 

great eruptions of the volcano, as it is overlain 

by at least 150 feet of loose material, the 

greater part of which is black pumice. This is 

the only lava seen in place except on the inner 

wall of the crater, but many fragments of 

black obsidian, containing a few glassy lathshaped crystals of feldspar, were found on the. 

mountains many miles from the crater. Indications of extinct fumaroles were sought in the 

ash-covered area east of the. crater, but much 

of the volcanic material has been worked over 

by streams, · and no evidence of fumarolic 

activity was found. The upper valley of 

Meshik River and also the valley of Aniakchak 

River in the vicinity of Albert Johnson Creek 

have been filled with volcanic debris to such 

an extent that the prBsent valley floors are very 

broad and nearly level. A few low isolated 

hills near the margins of the level area appear 

to have been partly buried, with only their 

summits left exposed, but this is probably an 

illusion. Several high mountains southeast of 

the crater are sharp-peaked, especially Pinnacle Mountain, and are composed of hornblende andesite. A stream of considerable 

size, Hidden Creek, a tributary of Aniakchak 

River, flows through a subterranean channel 

beneath the ash and cinders for a distance of 

5 or 6 miles and emerges on the west bank of 

the river. The Aniakchak is about 100 feet 

wide and 4 feet deep below the North Fork. 

The current is swift enough to transport small 

pieces of pumice along the bottom. At 4 miles 

from its mouth the river has eroded a picturesque gorge through a thick deposit of volcanic 

agglomerate. The southwest side of the gorge 

is formed by a rugged spur that projects across 

the valley from the hills to the southwest and 

is locally known as Cape Horn. (See fig. 11.) 

The river is navigable by small boats as far as 

the meanders below the mouth of Mystery 

Creek. 

A broad marshy lowland lies between the 

shore line of Aniakchak Bay and the hills 

toward the northwest. In this area a remarkable series of nine crescent-shaped ancient 

beaches can be seen from the mountains north 

of the river in the form of low ridges conforming in direction to the present shore line. A 

large part of the material in these ridges conists of volcanic ash and pumice washed ashore 

by the waves after having been trsnsported 

,into the bay by the river. The bay is uncharted and is not a protected harbor, although 

deep water is reported by masters of fishing 

schooners who have entered the bay. Hook 

Bay, 25 miles directly south of the crater, 

affords an excellent harbor for boats of moderate size. An old trail leads from this bay 

over the mountains toward Meshik River 

valley and is probably the best route from the 

Pacific coast to the crater, although in fair 

weather a landing can be made at the mouth of 

the river at Aniachak Bay. From this point 

the distance to the crater is not so great as 

from Hook Bay, and the route is over level 

country. Chignik is the nearest settlement 

and is 40 miles southwest in a direct line from 

the . crater but at least 60 miles by trail. A 

trapper's cabin has been built near the lagoon 

at Aniakchak Bay and one on the south side 

of the valley below Albert Johnson Creek. The 

trappers occupying the cabins during the winter 

had traveled over the cinders as far west as 

Meshik Lake for many years, but they did not 

know of the existence of Aniakchak Crater. 

Vegetation has gained a footing in places 

throughout the area covered by ash, and even 

within the crater several tufts of grass and 

low flowering plants were seen. Large areas, 

however, within a radius of 20 miles of the 

crater, are entirely barren of plant life and have 

the appearance of arid plains. Alder bushes 

have grown to a height of 6 feet in the valleys 

of High and Lava creeks and furnish sufficient fuel for camp purposes, but they are not 

straight enough to be used for tent poles. 

Foxes and Kodiak bears inhabit the region, 

Small herds of caribou were seen near the valley 

of Pumice Creek. 

The wide general use of the term "crater" 

includes several varieties or types, which have 
144 SHORTER .CONTRIBUTIONS TO GENERAL GEOLOGY, 1923-1924. 

been differentiated as impact craters, subsidence craters, upbuilt craters, and explosion 

craters. An impact crater may be formed by 

the fall of a body, such as a large meteorite or a 

projectile from a cannon. Such a bowl-shaped 

hollow or pit may have nothing in common with 

volcanic activity. A subsidence crater is a depression below the general level of the country 

or a concave area on a mountain, made b3r the 

collapse of the roof of a cavity. In limestone 

countries such depressions are common, ·but the 

use of the term is restricted by many geographers to pits occurring in volcanic regions. 

These pits are usually caused by the collapse of 

cavities · formed in volcanoes by the eruption 

of lava and other material. Craters formed in 

this manner are also known as caldrons. The 

largest and some of the best-known craters on 

the earth are of this variety, to which belong 

Kilauea, in the Hawaiian Islands (2.93 miles in 

diameter); the pit of Crater Lake, Oregon (5Y2 

miles in diameter); Ngorongoro, East Africa 

(12 miles in diameter); and Aso-san, in Japan 

(dimensions, 9 by 14 miles). An upbuilt crater 

has the form of a more or less circular mound 

surrounding an aperture, relatively small in 

diameter but usually deep, which serves as a 

vent for the lava, ash, and fumes thrown out 

by a volcano. This is the normal and most 

common type of craters and occurs on 'the 

summits of Lassen, Etna, Cotopaxi, Fuji, and 

scores of other volcanoes. Stromboli, in the 

Mediterranean Sea, is taken as the type of the 

explosion craters. Better examples, however, 

are known, such as the crater formed by the 

ancient explosion of Vesuvius, A. D. 79, of 

which Mount Somma is a remnant, and the 

ruins of Krakatoa in 1883 and of Katmai in 

1912. Excavations made by erosive agents 

have been referred to and classified as craters, 

but they have nothing to do with volcanic 

action. 

· All the evidence now available points to the 

origin of Aniakchak Crater by explosive activity and not by subsidence. Besides the vast 

quantities of rather fine material thrown from 

the crater and concentrated in the valleys of 

the surrounding country, huge projectiles were 

hurled many miles. On the north slope of 

Elephant Mountain, 1,000 feet above the valley 

of Meloy Creek and 23 Y2 miles from the center 

of the crater, a block of black obsidian was 

found which measured at least 2 cubic feet in 

volume. About 14 miles southeast of the 

crater an angular ma~s of sandstone, 5 feet in 

diameter and containing fossils similar to those 

found near Black Nose, occurs near the summit 

of a small hill composed of agglomerate. The 

large boulder is not waterworn, and there is 

slight probability that it was carried to its 

present position by a glacier. The ash contains smaller fragments of sandstone that have 

the same lithologic character as that exposed in 

the southeast wall of the crater and were not 

derived from rock in the immediate vicinity in 

which they were found. · That tremendous explosive forces were active at the time the present crater was formed is quite evident. All the 

known craters of the world as large as Aniakchak Crater or larger are thought to have been 

formed by subsidence. Katmai Crater, 3 

miles in diameter, 151 miles to the northeast, 

was formerly considered the largest crater of 

the explosive type known, but it is greatly 

surpassed by Aniakchak Crater, 6ji miles in 

diameter. In diameter and general outline the 

caldron of Crater Lake, Oreg., and Aniakchak 

Crater are remarkably similar, although the 

two are of entirely different types. 

The form of the mountain mass that occupied 

the present site of the era ter prior to the 

eruptions that resulted in the formation of 

the depression can of course only be conjectured. Before the existence of the volcano 

the area now within the crater was probably 

occupied by one or more mountains of moderate altitude-that is, by analogy with other 

mountains in the district, between 3,000 . and 

4,000 feet-which were composed of very 

slightly folded sedimentary rocks, intruded 

on the north by a large mass of quartz diorite. 

Why volcanic vents should be formed near the 

summits of high mountains composed of nearly 

horizontal strata is difficult to explain, but on 

the Alaska Peninsula many of the active and 

extinct volcanoes origin a ted in mountains of 

this type. This is especially true of the volcanoes toward the northwest, of which Mounts 

Katmai, Magiek, Peulik, and Chiginagak are 

examples. These volcanoes and many others 

on the Alaska Peninsula have formed cones 

and increased their altitudes to heights ranging from 5,000 to nearly 10,000 feet by successive lava flows over the sedimentary rocks. 

Mount Chiginagak (Pl. XLIV, B), an active 

volcano 43 miles northwest of Aniakchak 

Crater, is an impressive and typical example 

of an upbuilt cone. That a similar cone 

once towered above the site of Aniakchak 

Crater is suggested by beheaded lava flows, 
ANIAKCHAK CRATER, ALASKA PENINSULA. 145 

remnants of which are exposed on the east 

wall of the crater, on the summit of ·Black 

Nose, and possibly in the bed of Lava Creek. 

An imaginary cone reconstructed a mile in 

height above the present floor of the crater 

would be slightly over 6,000 feet above sea 

level, an altitude which is very low in proportion to the diameter of the base and also 

relatively low if compared with the altitude 

of other volcanic cones. But even if a low 

cone is postulated the amount of material to 

be accounted for is enormous and the force 

necessary to remove it in one or several explosions is beyond imagination. The capacity 

of the crater alone, if 1,600 feet is taken as the 

average height of the rim, is about 9 cubic 

miles. Subtracting 1 cubic mile for the large 

cinder cone still leaves space for 8 cubic 

miles within the crater. To this must be 

added at least 7 cubic miles if the low cone, 

suggested above, ever existed. Between 300 

and 40.0 square miles of adjacent country 

on the east and south is known to be covered 

to various depths by volcanic ash and cinders, 

and if an equally large area north and west of 

the crater is also overlain by ejecta, certainly 

an appreciable part of the supposed total of 

15 cubic miles is still to be seen. 

Ordinarily the Bering Sea coastal plain on 

the northwest side of the peninsula is· dotted 

with thousands of small lakes, but in the area 

north of the crater no lakes could be seen from 

Jaw Mountain. That all depressions in this 

part of the plain were filled by material from 

the crater is a fair deduction. The volume of 

material ejected from Katmai is estimated at 

4.75 cubic miles, but Katmai Crater has a 

capacity of only 2 cubic miles. The ejection 

of vast quantities of material from a single 

source and perhaps during a single period of 

eruption is not unheard of in volcanism. 

Capps 6 has estimated a volume of 10 cubic 

miles of volcanic ash thrown from a vent in 

the upper White River basin, and other large 

estimates have been made. Most of these 

computations, however, were made from measurements of the material ejected and not from 

the capacity of the crater. 

Few data are now available for estimating the 

age of Aniakchak Crater. However, it is 

believed to be one of the oldest of the series 

of volcanoes along the Aleutian Range. That 

6 Capps, S. R., An ancient volcanic eruption in the upper Yukon basin: 

U.S. Geol. Survey Prof. Paper 95, p. 62, 1915. 

the eruption antedat~s historic record is suggested by the amount of stream erosion, 

especially in Lava Creek, and the vegetation 

of the area, including alders. If the absence 

of evidence of glaciation since the eruption is 

taken as a criterion it would appear that the 

eruption is of post-Pleistocene age. Although 

the ash is more or less concentrated in the 

valleys it is not in the form of glacial moraines, 

and unless an ice sheet in which there was little 

or no movement covered the entire area, 

moraines of the loose pyroclastic material 

would be expected had this material been deposited before glaciation. A few of the valleys, 

such as that of Ray Creek, in which thick 

deposits of ash occur, are rather narrow and 

probably have been formed almost entirely by 

stream erosion. Most of the valleys are broad 

and suggest extensive glaciation before they 

were partly filled by ash. A detailed study is 

necessary for a more definite age determination. 

An examination of the relief map (Pl. XLII) 

will perhaps convey a better idea of the giant 

crater than a description. Nearly all distances 

were scaled from Mr. Sargent's skillfully 

drawn topographic map, on which the relief 

map by Mr. Renshawe is based. The topographic map is published separately as the 

Cold Bay-Chignik map. 

The writer wishes to acknowledge his indebtedness to Mr. Sargent for cooperation 

during the field work and for valuable assistance and criticism in the preparation of this 

paper. Thanks are also expressed to Mi. Sidney Old, who accompanied the writer into the 

crater and led the way across Aniakchak River. 

The scenery of the Aniakchak district, with 

its broad prairie-like valleys, n1argined by majestic, sharp-peaked mountains, is impressive 

and in many respects unique. The once active 

scene of terrific earth convulsions is now almost 

oppressively silent. The coloration of the 

country is somber and together with the fretfully driven clouds tends to create a rather 

pleasing weirdness. Aniakchak Crater is one 

of the great natural curiosities of North America and is certainly worthy of further investigation. Although small in comparison, it is 

probably the nearest counterpart on earth to 

the craters of the moon in regard to the manner of its formation . . Were it not so remote 

from the usual paths of travel the setting apart 

of this crater as a national monument would 

be justified.