Investigations of 

Alaskan Volcanoes

GEOLOGICAL SURVEY BULLETIN 102

This volume was published 

as separate chapters A-U
UNITED STATES DEPARTMENT OF THE INTERIOR

GEOLOGICAL SURVEY 

William T. Pecora, Director
CONTENTS

[Letters designate the separately published chapters]

Page

(A) Geology of Pavlof Volcano and vicinity, Alaska, by George C. Kfennedy

and Howard H. Waldron________________..____________ 1

(B) Geology of Great Sitkin Island, Alaska, by Frank S. Simons and

Donald E. Mathewson__________________________ 21

(C) Geology of northern Adak Island, Alaska, by Robert R. Coats____ 45

(D) Geology of northern Kanaga Island, Alaska, by Robert R. Coats___ 60 

(E) Reconnaissance geology of some western Aleutian Islands, Alaska,

by Robert R. Coats____________________________ 83 

(F) Geology and petrology of the Pribilof Islands, Alaska, by Tom

F. W. Earth__________________________________ 101 

(G) Ocean floor structures, northeastern Rat Islands, Alaska, by

George L. Snyder_____________________________ 161 

(H) Geology of Little Sitkin Island, Alaska, by G. L. Snyder_______ 169 

(I) Geology of the Delarof and westernmost Andreanof Islands, Aleutian

Islands, Alaska, by George D. Fraser and H. Frank Barnett_ 211 

(J) Geologic reconnaissance of Gareloi Island, Aleutian Islands, Alaska,

iby Robert R. Coats____________________________ 249 

(K) Geology of Segula, Davidof, and Khvostof Islands, Alaska, by

W. H. Nelson________________________________ 257 

(L) Geology of Umnak and Bogoslof Islands, Aleutian Islands, Alaska,

by F. M. Byers, Jr______________________________ 267

(M) Geology of southern Adak Island and Kagalaska Island, Alaska,

by George D. Fraser and George L. Snyder________ 371 

(N) Some effects of recent volcanic ash falls' with especial reference to

Alaska, by Ray E. Wilcox_______________________ 409 

(O) Geologic reconnaissance of Semisopochnoi Island, western Aleutian

Islands, Alaska, by Robert R. Coats________________ 477 

(P) Geology and submarine physiography of Amchitka Island, Alaska,

by Howard A. Powers, Robert R. Goats, and Willis H. Nelson_____ 521 

(Q) Geology of Rat Island, Aleutian Islands, Alaska, by Richard Q. Lewis,

Willis H. Nelson, and Howard A. Powers_________ 555 

(R) Geologic reconnaissance of Kiska Island, Aleutian Islands, Alaska,

by Robert R. Coats, Willis H. Nelson, Richard Q. Lewis, and

Howard A. Powers______________________ 563 

(S) Geology of Unalaska Island and adjacent insular shelf, Aleutian

Islands, Alaska, by Harald Drewes, G. D. Fraser, G. L. Snyder,

and H. F. Barnett, Jr__________________________ 583 

(T) Geologic reconnaissance of Frosty Peak volcano and vicinity, Alaska,

by Howard H. Waldron_____________________ 677 

(U) Geology of the Near Islands, Alaska, by Olcott Gates, Howard A.

Powers, and Ray E. Wilcox, with a section on Surficial geology of

the Near Islands, by John P. Schafer.___________ 709

US. GOVERNMENT PRINTING OFFICE :1970 O 407-665
Geology of Pavlof 

Volcano and Vicinity 

Alaska

By GEORGE C. KENNEDY and HOWARD H. WALDRON

INVESTIGATIONS OF ALASKAN VOLCANOES

GEOLOGICAL SURVEY BULLETIN 1028-A

Prepared in cooperation with the 

Office, Chief of Engineers, U. S. Army

^ UNITED STATES GOVERNMENT PRINTING OFFICE, WASHINGTON : 1955

».
UNITED STATES DEPARTMENT OF THE INTERIOR 

Douglas McKay, Secretary

GEOLOGICAL SURVEY 

W. E. Wrather, Director

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

. Washington 25, D. C. - Price 65 cents (paper cover
PREFACE

In October 1945 the War Department (now Department of the 

Army) requested the Geological Survey to undertake a program of 

volcano investigations in the Aleutian Islands-Alaska Peninsula area. 

The first field studies, under general direction of G. D. Robinson, were 

begun as soon as weather permitted in the spring of 1946. The results 

of the first year's field, laboratory, and library work were assembled 

hastily as two administrative reports. Part of the data was published 

in 1950 in Geological Survey Bulletin 974r-B, Volcanic activity in the 

Aleutian arc, by Robert R. Coats. The remainder of the data have 

been revised for publication in Bulletin 1028.

The geologic and geophysical investigations covered by this report 

were reconnaissance. The factual information presented is believed 

to be accurate, but many of the tentative interpretations and conclusions will be modified as the investigations continue and knowledge 

grows.

The investigations of 1946 were supported almost entirely by the 

Military Intelligence Division of the Office, Chief of Engineers, U. S. 

Army. The Geological Survey is indebted to the Office, Chief of 

Engineers for its early recognition of the value of geologic studies 

in the Aleutian region, which made this report possible, and for its 

continuing support.

in

CONTENTS

Page

Abstract__ _____-____--_________--____--_-__-_-----_-___-___-___- 1

Introduction ______________________________________________________ 1

Geography__ ___________________-__-_-_-__--_-__-_-_--___--______ 2

Location, settlement, and accessibility__________________________ 2

Topography __________________________________________________ 4

Drainage and water supply_--_-_-------------_----------__-____ 4

Glaciers ______________________________________________________ 5

Geology.________________________-..__-------_-----_---__--_-___--_ 5

Rocks of Tertiary age__________________________________________ 6

Arkose ___________________________________________________ 6

Belkofski tuff--. __ _- 6

Agglomerate of Cathedral Valley.___________________________ 7

Intrusive rocks.___________________________________________ 7

Rocks of Quaternary age..______________________________________ 8

Older lava flows._____________-_____-_-_-___---____-__-____ 8

Volcanoes and associated lava flows..________________________ 10

Cinder cones and associated lava flows.______________________ 13

Unconsolidated deposits.____--_-_______---__-_-_--______-__ 14

Structure, ___________________-___-____--_--_-__^_-__---_______ 14

Fumaroles and hot springs...___________________________________ 15

Historic activity of Pavlof Volcano._____________________________ 16

Geologic history.______________________________________________ 17

Literature cited____________________________-______________--_^-___ 18

Index._____________....___.___.____________.___ 19

ILLUSTRATIONS

Page 

PLATE 1. Little Pavlof Volcano__________________________________ Facing 6

2. Slightly dissected cone of Pavlof Sister___________________ Facing 7

3. Geologic map of Pavlof Volcano and vicinity _____________ In pocket

4. Small crater on the northeastern side of the summit of Pavlof

Volcano__-__--_-__--____--_-____-_--___-_____-____ Facing 12 

FIGURE 1. Map of the Alaska Peninsula and Aleutian Islands__.________ 3

INVESTIGATIONS OF ALASKAN VOLCANOES

GEOLOGY OF PAVLOF VOLCANO AND VICINITY, ALASKA

By GEORGE C. KENNEDY and HOWARD H. WALDRON

ABSTRACT

An area of about 400 square miles near the end of the Alaska Peninsula and 

extending along the Pacific coast from Pavlof Bay to Cold Bay, was mapped 

geologically during the summer of 1946. The oldest rocks, consisting of arkose, 

are overlain by a thick sequence of fraginental volcanic deposits, principally tuff 

in the southwestern part of the area and agglomerate in the northeastern part. 

Diorite stocks cut the tuff and locally have altered0 it. Copper and gold occur in 

altered tuff beds adjacent to the diorite stocks. Some basalt plugs and andesite 

sills also cut the volcanic roclts. Both the bedded and the intrusive rocks are 

believed to be of Tertiary age. The igneous activity that produced these rocks 

was followed by a long period of erosion. Near the close of Tertiary time, 

volcanism was renewed. A series of basalt flows issued from vents along or near 

a great curving rift of northeast trend, and filled topographic depressions in the 

old erosion surface. Later, six large strato-volcanoes, accompanied by small 

cinder cones and associated lava flows, were built up along the rift. Pavlof, 

largest of these volcanoes, has been active frequently during historic time, its 

activity ranging from violent eruption of ash and lava to the quiet discharge of 

ash-laden steam.

INTRODUCTION

The smoke-plumed peak of Pavlof Volcano, 8,900 feet above sea 

level, forms an imposing landmark near the end of the Alaska Peninsula. The proximity of this active volcano and its satellites to Fort 

Randall, an Army base at Cold Bay, led to a geologic investigation 

of the area during the summer of 1946.

The investigation was undertaken during the period May 31 through 

September 1 by a party that was directed by George C. Kennedy, 

geologist, and included Howard H. Waldron, geologist, Kussell C. 

McGregor, recorder, and Charles O. Haynes and Leroy T. Isaacson, 

camp assistants. The results of the work are presented in preliminary 

form in this report.

The volcanoes of the Pavlof area were probably first seen by white 

men shortly after the Bering Expedition of 1741, but their first mention is by Kotzebue, reporting on his search for a Northwest Passage 

in 1815-18 (Grewingk, 1850). Very little geologic investigation has 

been done in the area in the past, although the prominence and activity

1
2 INVESTIGATIONS OF ALASKAN VOLCANOES

of Pavlof Volcano has been noted by many persons. The earliest 

geologic investigations of record are those by Constantin Grewingk 

(1850) in 1848. T. A. Jaggar x visited the area in 1927 while making 

a reconnaissance investigation of the Alaska Peninsula and the Aleutian Islands. He returned to the area during the summer of 1928 

under the auspices of the National Geographic Society (Jaggar, 

1929). Scientific results of his visits have not been published. C. P. 

McKinley (1929), who accompanied Jaggar in 1928, prepared a topographic map of the area extending from Port Moller on the east to 

Lenard Harbor on the west. S. E. Capps (1934) briefly examined 

some coastal parts of the area in 1932. B. R. Hubbard (1935) visited 

the area in 1934.

Acknowledgment is due Capt. John Weyant, commanding officer of 

Fort Randall, Capt. E. R. Hoover, ordnance officer of Fort Eandall, 

the staff of the Pacific American Fisheries, Inc., at King Cove, Mr. 

Alex Dushkin, and the Eev. D. C. Hotovitsky for their cooperation 

and assistance.

GEOGRAPHY

LOCATION, SETTLEMENT, AND ACCESSIBILITY

The area mapped geologically during 1946, called the Pavldf area 

in this report, includes about 400 square miles near the tip of the 

Alaska Peninsula. It covers a strip as much as 15 miles wide along 

the Pacific Ocean and extends from Pavlof Bay on the east to within 

a few miles of Cold Bay on the west. Pavlof Volcano, which lies 

within the area, is about 35 air-line miles northeast of the Army airbase' at Fort Eandall, about 215 air-line miles northeast of Dutch 

Harbor, and about 390 air-line miles southwest of Kodiak (fig. 1).

Belkof ski, a native village about 22 miles southwest of Pavlof VolCanOj and King Cove, about 30 miles southwest of the volcano, are the

only communities in ike area. SuppllfiS CEIl 1)6 (tolllCd at King 

Cove, the site of a large cannery, a post office, a school, and a general

store. A short-wave radio station is operated by the cannery during 

the summer. Fassengor-ana-f reigkt aimers deliver supplies to King 

cove on their way to and from Bristol Bay and points north.

The Pavlof area is readily accessible only by boat. Good anchorages

are found at Ivan Island near Chinaman Lagoon in Pavlof Bay, at

Volcano Bay (locally known as Bear Bay), at Belkofski Bay, at King 

cove, ana at i^nftr<i nart>or in Cold Bay. Many lagoons ar& aCC6Ssible by small boats at high tide but are dry or nearly dry at low tiae.

There are no roads or man-made trails. Trappers' hlltS Scattered 

throughout the area afford emergency lodging and protection from 

storms.

1 Jaggar, T. A., Scientific exploration of the Aleutian Islands: U. S. Geol. Survey 

unpublished report.
» «.

I 1 [T IT I I ! | I I I r-jri I I 

170° 180° ~ "170° 

FIGURE 1, Map of the Alaska Peninsula and Aleutian 
4 INVESTIGATIONS OF ALASKAN VOLCANOES

TOPOGRAPHY

The Alaska Peninsula comprises three major physiographic divisions : a narrow lowland facing the Pacific Ocean; a broad, swampy 

lowland facing the Bering Sea; and-the rugged Aleutian Range between. The Pavlof area embraces large segments of the Pacific Ocean 

lowland and of the Aleutian Range and a small inland segment of the 

Bering Sea lowland.

Between Cold Bay, at the western end of the area, and Volcano 

Bay the mountains rise abruptly from the ocean. Steep-walled fiordlike bays indent the rugged coastline, and only a few broad flat valleys 

breach the cliffs and steep slopes. At the foot of the cliffs are narrow 

boulder beaches and a few sea stacks. Bay deltas and midbay and 

bayhead bars are common in the narrow bays and coves. Reefs and 

offshore rocks, abundantly fringed with kelp, flank most of the headlands.

Northeastward from Volcano Bay is a narrow constructional plain 

that has been built up by coalescing alluvial fans and sheet floods; 

it broadens both northward and eastward from Volcano Bay and 

merges into the Bering Sea lowland at the head of Pavlof Bay, The 

rather smooth surface of the plain is interrupted by scattered, low, 

rolling hills. The plain is bordered on the southeast by narrow, steep 

beaches of black volcanic sand. Barrier beaches enclose large lagoons 

at the mouths of most of the lowland streams. Much of the seaward 

part of the lowland is a maze of streams, swamps, marshes, and stagnant lakes. Grass, tundra vegetation, and in some places clumps of 

alders and willows cover most of the higher landward part. Extensive areas are nearly barren ash and cinder wasteland.

The mountains of the Pavlof area, although a part of the Aleutian 

Range, constitute an isolated block separated from the main range 

by lowlands near Pavlof Bay and Cold Bay.

The Bering Sea lowland is similar to the constructional plain of 

the Pacific Ocean lowland in most respects, but as so little of it is

included in the area mapped, no discussion of it is made in this report. 

DRAINAGE AND WATER SUPPLY

Several large and numerous small unnamed streams empty into 

the Pacific Ocean within the mapped area. No measurements of 

stream flow have been made, but it is certain that the annual winter

snows and the perennial snowfields insure an abundant water supply

during most of the year. Streamflow decreases greatly during the

winter, and some streams cease to flow for a few weeks or months. 

Melting snow during spring and early summer thaws provides a great 

volume of water; however, many of the swollen streams carry such 

great quantities of suspended matter that the water is not usable
GEOLOGY OF PAVLOF VOLCANO AND VICINITY 5

unless filtered or allowed to settle. During late August and September the water of some streams is undrinkable because of pollution by 

decaying dead salmon. Only on the surface of recent lava flows and 

in parts of the country deeply covered by ash is surface water lacking 

or scarce.

GLACIERS

Glaciers cover much of the upper slopes of the larger volcanoes 

and occupy the heads of many of the upland valleys. Most of Little 

Pavlof Volcano, Double Crater Volcano, and that part of Pavlof 

Volcano above an altitude of about 1,600 feet are covered by a 

glacier that has an area of more than 50 square miles (pi. 1). Tongues 

of this glacier that trend both north and east around Pavlof Sister 

extend to an altitude of 1,000 feet. The flanks of Pavlof Sister, however, are free of ice at altitudes at which nearby Pavlof is covered by 

glacier. Much volcanic ash is mixed with the glacial ice, and summer 

melting, added to recent ash falls, leaves a thin, dark ash cover over 

most of this glacier (pi. 2).

Small glaciers occupy the northeast and southwest slopes of Mount 

Hague and fill the large crater at its summit. The glacier of the 

northeast slope of Mount Hague coalesces with the extension of the 

large glacier of Pavlof, Little Pavlof, and Double Crater Volcanoes. 

A small glacier, a few square miles in area, trends northward 

from the summit of Mount Emmons, and a somewhat larger glacier 

occupies much of the upland south of "Emmons Lake." 2

Glaciers occupy parts of the highland area of the Aghileen Pinnacles, west of the mapped area, and extend from the summit of 

Mount Dutton. The boundaries of these glaciers have not been 

traced. Many small cliff and headwall glaciers occur throughout 

the upland.

For the most part the glaciers appear to be relatively static. The 

presence of widespread undissected morainal deposits in areas now 

free of permanent ice, and the existence of U-shaped valleys and 

other such typical glacial features throughout the area indicate that 

glaciation in the recent past was considerably more widespread.

GEOLOGY

The oldest exposed rocks in the Pavlof area are believed to be of 

Tertiary age. They consist of arkose, and occur in beds overlain by 

a thick sequence of tuffs and agglomerates. Broad, flat folds characterize their structure. The bedded rocks are intruded by quartz 

diorite stocks, basalt plugs and necks, andesite sills, and numerous 

basaltic dikes. The Quaternary rocks of the area comprise basalt

2 Place names In quotation marks are not shown on standard maps but are used for 

convenience In this report. '
6 INVESTIGATIONS OF ALASKAN VOLCANOES

lava flows along a northeastward-trending rift; a chain of large stratovolcanoes, made up of interbedded lava flows and pyroclastic material, 

which have been built up over the rift; numerous satellitic cinder cones 

and associated lava flows; and minor glacial, alluvial, and beach deposits. A discussion of the rocks of the Pavlof area and their 

relationships follows. Insofar as is feasible they are treated in 

chronological order. The geology of Pavlof Volcano and vicinity is 

shown on plate 3.

BOCKS OF TERITAEY AGE 

ARKOSE

The oldest rocks in the Pavlof area are nonfossiliferous beds of 

green arkose, which crop out in cliffs at Indian Head and in the northwest corner of Belkofski Bay. A thickness of 200 feet of these beds 

is exposed in the crest of a broad anticline with maximum dips of 

2°-3°. Lenses of pebble conglomerate 1-2 feet thick are interbedded 

with the arkose. The areal extent of the arkose is too small to give 

any clue as to its source. It is tentatively assigned a Tertiary age because of conformable relations with the overlying locally fossiliferous 

tuff beds.

BEL.KOFSKI TUFF

Conformably overlying the arkose is a thick series of well-bedded 

tuff. These tuff beds crop out principally around Belkofski Bay and 

on Belkofski Point; therefore, they are designated Belkofski tuff in 

this report. They crop out also from Dushkin Lagoon, east of Volcano Bay, to King Cove.

The beds are classed as volcanic sandstones and volcanic conglomerates. They are largely composed of fine- to coarse-grained lithic 

tuff colored in shades of green, purple, and gray. Where the tuff has 

been reworked by water, the original angular fragments are subrounded to rounded. The tuff is made up chiefly of a microcrystalline 

aggregate of feldspar microlites and chlorite, but crystals and angular 

fragments of oligoclase feldspar are included. The beds have been 

intensely silicified and sericitized in the vicinity of the diorite stocks 

that intrude them on Belkofski Point and at the head of Volcano Bay. 

The total thickness of the Belkofski tuff is difficult to ascertain, but it 

exceeds 3,000 feet.

Numerous plant fossils, principally silicified and carbonized trunks 

of trees and impressions of conifer needles, are present in the lower 

parts of the Belkofski tuff. They belong chiefly to an unidentified 

species of fir. Their age is not yet determined, but it is probably Tertiary. No conifers grow on the Alaska Peninsula, and it is not likely 

that any have grown there since the early Pleistocene. Silicified and
GEOLOGICAL SUliVEY 

The slopes are largely ice covered. An artive tongue of HI ! nil: 1' \\ I.OK VOLCANO. be seen between Little Pavlof and Pavlo

Air Force, 1942.
GEOLOGICAL SURVEY 

SLIGHTLY DISSECTED CONE OF PAVLOF SISTER

Crevassed glacier on lower slopes of Pavlof Volcano (left foreground) is covered by ash. Ph
GEOLOGY OF PAVLOF VOLCANO AND VICINITY 7

carbonized plant remains, occurring in beds 1-5 centimeters thick, 

also are present in the formation.

The age of the Belkof ski tuff is believed to be Tertiary, partly on the 

evidence of the fossil fir trees, and partly by analogy with nearby areas. 

The "lower" beds of Palache's (1904) Stepovak series, exposed in the 

vicinity of Chichagof Peak, about 85 miles northeast of Belkofski Bay, 

are described as pyroclastic deposits of early Eocene age. They appear 

to occur locally, however, and probably are not comparable to the later 

pyroclastic deposits occurring throughout the Peninsula and assigned 

a post-Eocene age by W. W. Atwood (1911), G. C. Martin and F. J. 

Katz (1912), W. K. Smith and A. A. Baker (1924), and R. S. Knappen 

(1929). Available evidence indicates, therefore, a post-Eocene, prePleistocene age for the Belkofski tuff, and the rocks are tentatively 

assigned a late Tertiary age.

AGGLOMERATE OF CATHEDRAL VALLEY

A thick sequence of agglomerate beds and subordinate tuff beds and 

lava flows crops out north of the chain of volcanoes that occupies the 

central part of the mapped area, and is well exposed in Cathedral 

Valley. The rocks are predominantly basalt and basaltic andesite. 

The beds dip north toward the Bering Sea at angles of a few degrees. 

They are probably comparable in age to the Belkofski tuff, but direct 

evidence is lacking.

INTRUSIVE ROCKS

The beds of Belkofski tuff are cut by stocks of quartz diorite, by 

basaltic plugs and necks, by thick sills of andesite, and by smaller sills 

and dikes of basalt and andesite.

Four stocks, each several square miles in area, occur at the head of 

Volcano Bay, on Belkofski Point, near the head of Belkofski Bay, and 

at the head of King Cove, respectively. The stocks are made up of 

coarsely crystalline quartz diorite that contains about 20 percent 

quartz, 60 percent andesine felspar, and 20 percent amphibole,, biotite, 

and magnetite. In general this rock has been little altered, but the 

adjacent tuff beds have locally been sericitized and silicified for distances as great as 1 mile from the stocks. The tuff was also considerably bleached during the period of alteration, thus its original 

composition is difficult to determine. Bleaching and alteration are 

particularly conspicuous in the tuff on Belkofski Point. Many contacts between tuff and quartz diorite are gradational because of the 

intense alteration. Between Bear Bay and Moss Cape, numerous sills 

extend from the main quartz diorite body into the altered tuff and 

further obscure the marginal relationships.

The mineralization associated with the emplacement of the diorite 

stocks is principally pyritization, but extensive, though weak, copper 

mineralization was noted in the tuffs immediately south of the intrusive
8 INVESTIGATIONS OF ALASKAN VOLCANOES

mass northwest of the head of Belkof ski Bay. Local prospectors have 

reported finding colors of gold in the altered tuffs of Belkofski Point 

and near the head of Volcano 15 ay. Thorough prospecting of these 

localities is believed warranted.

In addition to the four quartz diorite bodies, several small masses of 

coarsely crystalline quartz-rich rocks are present about 3 miles north 

of the head of Volcano Bay. They have been mapped with the quartz 

diorite, although one of the smaller of these bodies may be granitic 

in composition.

Several large plugs of fine-grained dark olivine basalt cut the 

Belkofski tuff north of Belkofski Bay and east of Volcano Bay. At 

the margins of the plugs the tuff beds have been locally tilted and 

deformed, These plugs are believed to be the necks of ancient volcanoes that have been eroded away, and are believed to be somewhat 

younger than the quartz diorite intrusive masses.

One large sill of andesite, probably of the same age as the basaltic 

plugs, occurs several miles north of Volcano Bay. Numerous sills and 

dikes of andesite and basalt, too small to map, cut the tuff beds. Most 

of the dikes are less than 15 feet thick, but a few are as much as 50 feet 

thick; they can be traced for only short distances.

BOCKS OP QUATERNARY AGE 

OLDER LAVA FLOWS

Three extensive lava units fill old canyons and gullies carved in the 

Belkofski tuff and diorite stocks within the Pavlof area. These lava 

units the Arch Point basalt, the Dushkin basalt, and an even older 

group of basalt flows exposed principally near Black Point occur 

on the Pacific side of the Aleutian Range between sea level and an

altitude of 4,000 feet, but have been mapped only in the lowlands,

They are older than the cinder cones and their associated lava flows 

(p. 13) that are scattered throughout the central part of the mapped 

area, and are probably older than Pavlof Volcano and the other large 

strato-volcanoes (pp. 10-13). The oldest of these flows may be of very

late Tertiary age, but most of them are probably Pleistocene, and the

lavas as a whole are therefore tentatively assigned a Quaternary age.

Arch Point 'basalt. Thick lava flows, designated the Arch Point

basalt, are well exposed on Arch Point south of Dushkin Lagoon,

They are also exposed a few miles north of the head of Volcano Bay

and both north and south of "Emmons Lake;" small exposures may 

be found at the head of Belkofski Bay. The Arch Point basalt is

overlain by, and is therefore older than, the nearby flows of Dushkin 

basalt (see pp. 9-10). Columnar jointing in the Arch Point basalt is 

distinctive: hexagonal columns averaging 4-6 inches in diameter are 

arranged in fanlike patterns; some of the columns on the wings of a
GEOLOGY OF PAVLOF VOLCANO AND VICINITY 9

few fans are horizontal and resemble stacked cordwood. The rock is 

dark and contains 1-5 percent conspicuous glistening black hypersthene phenocrysts 2-4 millimeters long; about 15 percent plagioclase 

phenocrysts 1-3 millimeters long, ranging in composition from that 

of labradorite to that of bytownite; and sparse crystals of olivine and 

augite. The sources of the flows are not exposed.

Dushkin basalt. The most widespread of the older lavas is the 

Dushkin basalt, well displayed on the north margin of Dushkin 

Lagoon. The flows occur south of the tip of the long southwestern 

arm of the glacier extending from Little Pavlof and crop out sporadically over a distance of 20 miles southwestward to Mount Dutton. 

Locally, a single flow more than 200 feet thick makes up this unit; 

elsewhere, the unit comprises many superimposed flows, each a few 

tens of feet thick. In places, such as in the cliffs south of "Emmons 

Lake," the aggregated flows are several thousand feet thick.

The individual flows of Dushkin basalt are similar to each other. 

The rock is dark, unaltered, and locally rich in inclusions of dense 

earlier basalt. A streaked appearance, particularly conspicuous on 

somewhat weathered surfaces, and not unlike the banding recorded 

for some Yellowstone Park and Katmai lavas (Fenner, 1923), suggests that in places inclusions of a more siliceous rock have been remelted and dragged out as the lavas were extruded. Coarse columnar 

jointing is conspicuous in some of the thicker flows. As in the Arch 

Point basalt, the jointing is not invariably at right angles to the plane 

of the flow. Some columns are arranged in fanlike patterns, and 

many appear to lie parallel to the plane of the flow.

The Dushkin basalt characteristically contains 25-35 percent of 

strongly zoned labradorite phenocrysts, which range in length from 

0.5-3 millimeters. About 5 percent each of hypersthene and augite 

are present as small phenocrysts, 0.5 millimeter across. Hypersthene 

typically is surrounded by a very narrow zone of fine-grained clinopyroxene. The groundmass is made up of magnetite grains and of 

plagioclase and clinopyroxene microlites set in a matrix of brown 

glass.

The widespread distribution and the range in altitude of the flows 

of Dushkin basalt indicate that they did not all necessarily come from 

the same vent. It seems likely that they issued from a series of vents 

or were extruded as fissure flows from the main northeast-trending 

rift (now marked by the chain of strato-volcanoes and cinder cones) 

that extends from Pavlof Sister to Mount Emmons. Whatever the 

exact source, the lava poured out on the Arch Point basalt and partly 

filled topographic depressions in a pre-Dushkin erosion surface developed on the Belkofski tuff. South of "Emmons Lake" these lavas 

may have accumulated to sufficient depth to spill over the hills of 

Belkofski tuff toward the Pacific Ocean. The greatest volume of
10 INVESTIGATIONS OF ALASKAN VOLCANOES Y

Dushkin basalt appears to have been poured out in the vicinity of v 

Mount Emmons. vj

A'major problem, as yet unsolved, associated with both the Arch 

Point basalt and the Dushkin basalt, is the origin of the crescentic * 

depression, partly filled by "Emmons Lake," bordering the western 

half of Mount Emmons. It is not a normal feature of glacial erosion, 

particularly because of its crescentic shape and asymmetric transverse ' 

section the slopes of the outer confining wall of the trough are steep, ; 

and the slopes from the bottom of the trough toward Mount Emmons . are gentle. The explanation may be that the area surrounding Mount 

Emmons and Mount Hague including the depression is a sunken ,.- 

block or part of a caldera formed when the lavas of the Dushkin basalt 

were being erupted. These flows would then have poured on the newly T.

lowered surface, building up the foundations of Mount EmmOHS and .- 

Mount Hague as nested cones. Much geologic and topographic evidence contradicts this hypothesis, however, and further work must be 

done before the true relations can be determined. The original topographic features involving the Dushkin basalt have been profoundly ( 

modified by erosion. *

Basalt of Black Point. A group of lava flows, thought to be the ^ 

oldest of the Quaternary lavas, form a large dome-like hill near Black 

Point. They also crop out at tidewater in Long John Lagoon, and 

20 miles away along the beach in Chinaman Lagoon. An elliptical ; 

depression, largely filled with alluvium, at the top of the hill near 

Black Point suggests the presence of an ancient crater; it may mark 

the vent from which flows of basalt issued and spread north and south. «, 

The lava flows that make up the hill dip away from the summit at 

angles of about 2°-10°. *

The basalt of Black Point is dark reddish brown, dense, and even- \ 

textured. It is composed of abundant very small phenocrysts 70

percent labradorite feldspar, 8-10 percent olivine, and 2 percent 

hypersthene in a fine-grained groundmass which makes up about * 

20 percent of the rock. The basalt appears to contain more magnesium 

and calcium and less silica than most flows of the area. The flows at ^ 

Black Point contain a much higher percentage of phenocrysts than A

do the other flows studied.

.VOLCANOES AND ASSOCIATED LAVA FLOWS

Six large strato-volcanoes lie along an arc about 12 miles long and 

Constitute the central zone of the mapped area. These volcanoes 

Pavlof Sister, Pavlof, Little Pavlof, Double Crater, Mount Hague, 

and Mount Emmons appear to be built over a major rift of northeast trend. With the possible exception of Little Pavlof, these volcanoes have been active within historic time, as indicated by welldefined summit craters, lava flows and ash falls that show little sign
GEOLOGY OF PAVLOF VOLCANO AND VICINITY 11

of erosion, and undissected satellitic cinder cones. The age of the 

strato-volcanoes'cannot be precisely established. Most of the material making up the volcanoes probably accumulated by sporadic 

eruptions throughout Quaternary time; the uppermost parts are of 

Kecent age. The lowermost parts may be of late Tertiary age.

Wherever possible the lava flows and pyroclastic beds associated 

with the strato-volcanoes have been individually mapped (pi. 3). 

The lava flows and pyroclastic beds of each central vent are lithologically and structurally similar, and therefore the products of each 

volcano are discussed as a unit.

Pavlof Sister. Pavlof Sister is the northeasternmost volcano in 

this area. Its uniform slopes of about 33° rise to an altitude of more 

than 7,000 feet. The slopes of the volcano are covered with cinders 

and ash, much of which was probably showered on the cone from 

eruptions of nearby Pavlof Volcano. At the summit is a small 

crater a few hundred feet in diameter and a few tens of feet deep. 

Two recent lava flows, one on the north side and the other on the 

southeast side of the volcano, are largely buried under accumulations 

of ash and detritus. The upper parts of the flows are buried by ash; 

it could not be determined whether these lavas spilled from the crater 

at the top of the volcano or emerged from vents on the flanks of the 

cone. Gullies, each a few tens of feet deep, are carved on the slopes 

of the mountain, but they are not deep enough to reveal the structure 

of the volcano. A few small outcrops at the top of the mountain, 

in which flows of lava alternate with beds made up of ash, lapilli, 

bombs, and angular fragments of crater-wall rocks, provide a clue 

to the internal structure. The diversity of rocks in the exposures and 

the steepness of the slopes of the cone indicate that this is a stratovolcano made up of intermingled lava flows and pyroclastic deposits.

Pavlof Volcano. Pavlof Volcano rises to an altitude of 8,900 feet 

and is one of the highest peaks of the Aleutian Range. Ice that 

mantles the volcano almost to its summit limits the amount of information that can be obtained regarding the bedrock geology.

A small crater occupies the northeast side of the volcano near its 

summit (pi. 4). During the summer of 1946, puffs mostly of 

steam emerged from the vent at infrequent intervals. For periods 

of several days the crater appeared to be inactive. Occasionally a 

relatively steady emission of steam was observed, and several times 

dark, ash-laden puffs emerged from the vent. Only a small amount 

of the ash was carried beyond the limits of the crater.

Pavlof is made strikingly asymmetrical by a long ridge that extends 

southwestward from the vent. The asymmetric shape of the volcano 

suggests that the vent has been migrating northeastward. Such migration is common in other volcanic regions, but the reason for it is 

as yet undetermined.
12 INVESTIGATIONS OF ALASKAN VOLCANOES

Three narrow lava flows extend seaward from bequeath the ice on 

the eastern and southeastern slopes of the volcano. They are of such 

recent date that their topographic expression and original blocky surfaces are almost unmodified by erosion. Parts of these lava flows are 

heavily blanketed by glacial moraine and recent ash falls. Two of the 

lava streams probably flowed from the cinder cones that project above 

the ice headward from the exposed parts of the flows.

South of the crest of Pavlof Volcano, headward glacial erosion 

has carved vertical cliffs, revealing the internal structure of the cone. 

Layers of ash, lapilli, bombs, and blocks alternate with lava flows 

and dip at angles of about 30° away from the summit.

Little Pavlof. Little Pavlof Volcano appears to have been long 

inactive; most of it has been carried away by glaciers. In vertical 

exposures southwest of the cone along "Glacier Ridge," interbedded 

agglomerates and lavas dip away from the core of the volcano at 

angles of 15°-35°. It appears likely that the period of principal 

growth of Little Pavlof overlapped that of Pavlof, and the older 

products of the two volcanoes are interbedded between the two cones.

Double Grater. Double Crater Volcano is a low hill that projects 

only a few hundred feet above a surrounding icefield. Two large, 

partly coalescing craters, each almost 1,000.feet across, occupy the 

upper part of the volcano. The more southerly of these craters contains a small, permanent icefield and is rimmed by brick-red interbedded agglomerates and lavas. The other crater contains a small 

lake and is largely filled with alluvium. The flows that extend from 

this volcano are buried under the surrounding icefield.

Mount Hague. Mount Hague is perhaps the most spectacular of 

the volcanoes in the Pavlof area. It is a twin-peaked volcano, the 

eastern peak rising to an altitude of 4,600 feet above the surrounding 

icefields and topped by a large, elliptical, glacier-filled crater almost

800 feet deep and two-thirds of a mile in longest dimension. The 

slopes of Mount Hague are blanketed partly by ice and partly by 

very recent cinder beds and lava flows. The volcano is a stratified 

cone made up of alternating lava flows and beds of agglomerate, which

apparently have been built upon a foundation of Dushkin basalt.

Many recent flows appear to have poured from vents on the flanks

of the volcano, particularly on the northwest flank. The large basalt

flow (pi. 3, flow 5), which covers much of the lowlands north of Dushkin and Long John Lagoons, may have had its source on Mount

Hague's southeast flank, novr buried by ice. Because of its fresh,

blocky surface and lack of dissection, this flow is believed to be at 

most only a few hundred years old. The flow is believed to have 

moved southwestward until it reached the heads of two narrow southeast-trending valleys carved in the older Dushkin and Arch Point 

basalts. The lava followed these valleys until it flowed out on the
GEOLOGICAL SURVEY 

.'V,- ;> £ ./t:' / *' '

SMALL CRATER OK THE NORTHEASTERN SIDE (II THE SI MM IT 

Pholograph by U. S. Army Air Force, 1912.
GEOLOGY OF PAVLOF VOLCANO AND VICINITY 13

low plain'at the valley mouths. Here the two streams spread radially 

and coalesced. Much of this lava has been capped by a younger and 

more extensive flow from cone G (p. 14).

That volcanic activity has not altogether ceased at Mount Hague 

is evidenced by the large and spectacular fumaroles on its western 

flank, described on page 15. . Mount Emmons. Mount Emmons is the southwesternmost of the 

large volcanoes in the area. Its cone, like those of the other volcanoes, 

is made up of interbedded lava flows and layers of agglomerate. It is 

apparently superimposed upon a platform of Dushkin basalt. The 

origin of the lower slopes of Mount Emmons has already been discussed in connection with the origin of the flows forming the Dushkin 

basalt (pp. 9-10). Icefields cover much of the north slopes of Mount 

Emmons, and satellitic cinder cones and their associated flows are 

scattered on the flanks of the volcano.

CINDER CONES AND ASSOCIATED LAVA FLOWS

Eleven cinder cones of Recent age occur in the Pavlof area. They 

are given alphabetic designations in this report. Compared with the 

large strato-volcanoes, the cinder cones are small, have a maximum 

height of only a few hundred feet, and are for the most part made up 

of ash, lapilli, bombs, and blocks, but include subordinate interbedded 

lavas." Each cinder cone is believed to be the product of a relatively 

brief cycle of eruption, for nearly all are built around vents from which 

only one or two lava flows have poured.

Most of the cinder cones are along the main rift on which the large 

strato-volcanoes are built, and on the flanks of the volcanoes. Some of 

the cones, however, are distant from the main rift.

Cone A\ located on. the major rift, is a symmetrical cone west of the 

summit of Mount Emmons. Below it is a small flow that poured from 

its crater down the side of Mount Emmons into the crescentic "Emmons 

Lake."

Four cinder cones, each with one or two flows, appear along the 

main rift between Mount Emmons and Mount Hague. Three of these 

cones B, C-, and E are somewhat dissected and are accompanied by 

flows of small extent. The fourth, cone G, which is very fresh-looking, 

is accompanied by a flow that covers an area of about 10 square miles 

and extends to the lowlands north of Volcano Bay. The flow forked: 

one tongue of lava moved southwestward along a canyon carved in the 

Dushkin basalt and poured into "Emmons Lake," and the other, a 

larger tongue, moved southward toward Dushkin Lagoon, blocking the 

stream draining "Emmons Lake" and creating a second, smaller lake. 

This flow is probably the youngest in the area. It is a typical aa, or 

blocky flow, having a very irregularly furrowed and blocky surface. 

Very little ash has been 'deposited on its lower parts, and vegetation
14 INVESTIGATIONS OF ALASKAN VOLCANOES

is just beginning to grow. The black top of the flow contrasts 

markedly with the green of the adjacent plains.

Two cinder cones, D and F, lie about 1 mile north of the main rift. 

D is a fresh-looking, breached cone from which a moderately extensive 

flow spilled north, damming a stream and creating a small lake along 

its western border. F is a highly dissected cone of which only two 

remnants remain. Much of its associated lava flow is deeply buried 

in ash and glacial outwash from Mount Hague.

Two coalescing symmetrical cones with deep summit craters, cones 

H and 7, lie about 2 miles south of Mount Hague. The southwest 

tongue of the glacier from Little Pavlof abuts against them on the 

east and has piled considerable morainal debris on their flanks. The 

recent flow from cone G partly encircles them on the west. Consequently, any flows associated with these cones are covered.

Cones / and K project above the ice on the west slopes of Pavlof 

Volcano. The lava flows that emerge from beneath the ice front down 

slope from the cones probably belong to them.

The lava flows associated with the strato-volcanoes and the cinder 

cones consist of somewhat vesicular, gray-to-black basalt containing 

20-30 percent phenocrysts. Most of the phenocrysts occur as laths of 

labradorite feldspar that are from 1-3 millimeters long; 1-5 percent 

of the phenocrysts are of olivine; 2-10 percent, of hypersthene; and 

about 5 percent, of augite. Narrow reaction rims of augite surround 

the hypersthene. Microlites of feldspar and clinopyroxene, and a 

little brown glass, make up the groundmass.

TTNCONSOMDATED DEPOSITS

Much of the surface of the Pavlof area is thinly covered by Recent

asK and by unconsolidated glacial, alluvial, and beach deposits. Only

where these imconsolidated deposits are of significant thickness and

extent are tkey sliown on the gQologic map (pi. 3) .

Deposits of volcanic silt, sand, and gravel are widely distributed

on the floors of stream valleys, on beaches, and on small marine and 

stream terraces.

Extensive moraines, only slighted dissected, fringe the lower slopes 

of the volcanoes. In the vicinity of Black and Bluff Points, thick 

deposits of recent glacial material occur at altitudes as low as 200 

feet. Some of the boulders in the moraines are as much as 20 feet 

across. Striated and faceted boulders are common. In addition to 

volcanic rock detritus, the moraines contain a few fragments of 

coarsely crystalline igneous rock whose source is unknown.

STRUCTURE

The general structure of the Aleutian Range in the Pavlof area 

appears to be that of a broad, flat anticline, trending northeast.
GEOLOGY OF PAVLOF VOLCANO AND VICINITY . 15

Gently folded beds having average dips of 5°-10° prevail throughout 

most of the area. Steeper dips were observed only in the vicinity of 

intruded plugs and high on the flanks and near the summits of the 

strato-volcanoes, each of which has superimposed its individual 

structure on the underlying major anticline.

The large volcanoes seem to be along a major curving rift, but the 

rift itself is buried and its characteristics are unknown.

Steeply dipping faults of small displacement are common in the 

Belkofski tuff, but are too small to be shown on the geologic map. 

Two larger faults have been mapped south of "Emmons Lake", but 

their relationships are not clear.

FUMAEOLES AND HOT SPRINGS

One area of f umaroles and one hot spring were discovered in the 

Pavlof area. Local residents report the existence of other hot springs 

beyond the mapped area on the side of the Aleutian Range facing 

the Bering Sea.

Six large fumaroles and many small ones occupy a steep gully on 

the southwest side of Mount Hague. They occur at altitudes ranging 

from 3,200 feet to 3,800 feet. In the summer of 1946, sulfur dioxide 

and steam were rising in clouds from the major vents, accompanied 

by a noise like that of a locomotive escape valve, which could be heard 

a quarter of a mile away. The presence of the fumaroles could be 

detected by their pungent odor at a distance of several miles 

downwind.

Extensive deposits of native sulfur occur within the gully, and 

cones of pure sulfur, 3 to 4 feet high, have been built around each 

of the vents. Because of the great volume of sulfur fumes, it is 

impossible, without special equipment, to approach closer than a 

few hundred feet to the cones. Large blocks of sulfur have tumbled 

down the gully onto the glacier below. A distinct reddish cast appears 

on the inside of the sulfur cones and deceptively suggests that they 

are heated to incandescence by the escaping fumes. This cannot 

be true, however, owing to the low melting point of sulfur; the red 

color probably results from the deposition of a sulfur mineral, such 

as realgar. No blocks of sulfur containing this reddish material were 

collected.

A hot spring near the northwest corner of "Emmons Lake" comprises two streams that emerge within a few feet of each other and 

flow into the lake. The temperature of the water was estimated to be 

140°F. An 8-inch pipe would probably be required to carry the 

combined flow of the streams. No incrustations were seen on pebbles 

within or near the spring, and the water was sweet and odorless. 

Vegetation for several hundred feet away from the streams was 

much more luxuriant than elsewhere around the lake.
16 INVESTIGATIONS OF ALASKAN VOLCANOES 

HISTORIC ACTIVITY OF PAVLOF VOLCANO

The activity of Pavlof Volcano has been often noted in the past, 

but few specific facts and details have been recorded. Some of the 

observations that follow are extremely indefinite and may apply to 

Pavlof Sister.

Grewingk (1850) reports that the volcano was active from 1762-86 

and in 1790, and that it was smoking in 1838.

Doroshin (1870) reports the eruption of flames, ash, and rocks 

in August 1844. In August 1846 he reports another eruption in 

which lava flowed out on the east slope, fire appeared from the top 

of the peak, and ash was carried as far as Unga Island, about 55 

miles east of Pavlof. The north side of the peak was smoking in 

August 1852.

An ash eruption is recorded for March 1866 (Coats, 1950).

Becker (1898) states from information compiled by W. H. Ball 

that in 1880 the volcano showed a "red glare" and that in 1892 it was 

smoking.

Jaggar (1929) reports that an island trapper said Pavlof was smoking vigorously from 1906-11 and that in 1911 "fire" poured down the 

mountain and alarming rumbles continued for several months; 

boulders were thrown into the air and the mountain was said to have 

cracked open toward the north. The United States Commissioner 

at Unga gave Jaggar black sand that fell at Unga from Pavlof during 

an eruption that occurred July 6,1914.

Other eruptions of Pavlof that were followed by dust falls, and a 

severe earthquake at King Cove, occurred in October 1917.

"Flames" that reached a height of 2,000 feet above the volcano 

lighted the village of Belkof ski the evening of December 24,1922, and

"flames" were again reported in tne -winter of 1923.

A strong explosion followed by steam and ash eruptions occurred 

on January 17, 1924. Crew members of the steamer Starr reported 

that Pavlof was unusually active in December 1929,

Rev. D. Hotovitsky (Hawaiian Volcano Observatory, 1931) reported that Pavlof was smoking all of the summer of 1931. The

volcano was in active eruption about May 20, 1931, and at times a glow

was seen at the crater; the ash fall was noticeable.

Major explosive eruptions occurred in 1936 and early in 1942; during the intervening period the emission of ash-laden steam was almost

continuous. Reports by Army and Navy fliers indicate almost continuous discharge of smoke from the crater since 1942. Activity was 

probably less during the summer of 1946 than at any time during the

preceding 4 years.
GEOLOGY OF PAVLOF VOLCANO AND VICINITY 17 

GEOLOGIC HISTORY

The geologic history of the Pavlof area is one of recurrent and 

long-continued volcanism characterized by periods of particularly 

violent activity followed by periods of relative quiescence during 

which erosion by streams and glaciers greatly modified the topography.

The first recorded event is the accumulation of a series of arkose 

beds in the southern part of the area, presumably in early Tertiary 

time. Sedimentary processes were interrupted by extensive and violent volcanism, during which the "beds of Belkof ski tuff accumulated 

to depths of several thousand feet. Locally the tuffs were reworked 

by streams, and volcanic sands and gravels were deposited in lowland 

areas. During about the same time interval, violent explosive eruptions produced the agglomerates of Cathedral Valley. Fir forests 

in the area were blanketed by the hot ash and were destroyed. Bodies 

of molten rock, possibly the same ones that caused the explosive volcanic activity, were intruded into the thick accumulations of fragmental material where they solidified as diorite stocks. Later, basalt 

was intruded into f ragmental rocks, probably reaching the surface to 

form volcanoes; andesite sills also were intruded. The volcanic 

activity was accompanied by gentle warping and, locally, by more 

intense deformation of the arkose beds and f ragmental deposits.

A long interval of erosion followed, during which deep canyons 

were carved in the tuff and agglomerate beds and in the intrusive rocks.

The period of erosion probably lasted until about the close of Tertiary time, when volcanic activity recurred, principally along a northeast-trending rift. Lava from the rift filled topographic depressions 

in the underlying rocks and flowed down valleys. Rather persistent 

central vents developed along the rift, over which strato-volcanoes 

were built by the quiet outflow of lava alternating with the explosive 

eruption of ash and coarse fragmental material. Cinder cones and 

their associated flows were built up around short-lived vents.

Ash from the volcanoes, reworked by sheet floods and streams, has 

accumulated in lowland areas, and glaciers moving down the sides 

of the higher volcanoes have built large moraines of volcanic debris 

along their margins.

Major explosive eruptions are to be expected from Pavlof Volcano 

and. possibly from some of the other volcanoes at intervals in the 

future; ash may be expected to be carried by the wind for many miles. 

Eruptions of lava from the flanks of the volcanoes and at new localities 

along the main locus of volcanic activity will probably occur also.
18 INVESTIGATIONS OF ALASKAN VOLCANOES

LITERATURE CITED

Atwoorl, W. W., 1911, Geology and mineral resources of parts of Alaska Peninsula : U. S. Geol. Survey Bull. 467, p. 48-73.' 

Becker, G. F., 1898, Reconnaissance of the gold fields of southern Alaska, with

some notes on the general geology: U. S. Geol. Survey, 18th Ann. Kept.,

pt. 3, p. 13-14 

Capps, S. R., 1934, Notes on the geology of the Alaska Peninsula and Aleutian

Islands: U. S. Geol. Survey Bull. 857-D, p. 152-153. 

Coats, R. E., 1950, Volcanic activity in the Aleutian Arc: U. S. Geol. Survey Bull.

974-B, p. 35-49. 

Doroshin, P. P., 1870, Oniektorykh vulkaiiakh: Russ. K. min. Gesell. Verh.,

ser. 2., v. 25, p. 44, St. Petersburg. 

Fenner, C. N., 19023, The origin and mode of emplacement of the great tuff

deposit of the Valley of Ten Thousand Smokes: Nat. Geog. Soc., Contr.

Tech. Papers, Katmai ser., no. 1, p. 53-61. 

Grewingk, Constantin, 1850, Beitrag zur Kentniss der orographischen und gecgnostischen Beschaffenheit der Nordwest Kiiste Amerikas, mit den anliegenden Inseln: Russ. K. min. Gesell Verh., J. 1848-49, p. 50-53, 204, St.

Petersburg.

Hawaiian Volcano Observatory, 1931, Volcano Letter, no. 357, p. 3. 

Hubbard, B. R., 1935, Cradle of the storms, p. 122-166, New York, Dodd, Mead

and Co. 

Jaggar, T. A., 1929, Mapping the home of the great brown bear: Natl. Geog. Mag.,

v. 55, p. 109-134. 

Knappen, R. S., 1929, Geology and mineral resources of the Aniakchak district:

U. S. Geol. Survey Bull. 797, p. 195-201. 

Martin, G. C., and Katz, F. J., 1912, A geologic reconnaissance of the Iliamna

region, Alaska: U. S. Geol. Survey Bull. 485, p. 78-82. 

McKinley, C. P., 1929, Pavlof district, Alaska Peninsula: U. S. Geol. Survey

Alaska Map 12, scale 1: 250,000. 

Palache, Charles, 1904, Geology about Chichagof Cove: Alaska, v. 4, Harriman

Alaska Expedition, p. 74-77.

Smith, W. R., and Baker, A. A., 1924, The Cold Bay-Chignik district: U. S. Geol. 

Survey Bull. 755, p. 187.
INDEX

Page

Acknowledgment . .-.__.._.._._ 2 

Agglomerate.._.... -.-._-.--...-----.- 5,7,17

Alaska Peninsula, physiographic divisions.... 44

Aleutian Islands. ____.....--.-_ 3

Aleutian Eange..... .-......-_.---...... 4,11

Alluvium__ 4,14

Andeslte... - - 7,8,17

Arch Point basalt....-.-.----..-.--.-.--.-.. 8-9,12

Arkose.. 5,6,17

Ash...............---.....-.-........ ... 5,17

Basalt.... 7,9-10,17

Bays.___...__ - . .______ 4

Beaches...._ _ - - 4

Bear Bay...____________ ___._ 2,7

Belkofski....-.. ....................... 2

Bay-..-.-.-.-----..---...--- 2

Point... . 6

tuff, features of....__...___._-.... 6-7

accumulation.

faults.........

gold.... ...

Bering Expedition....

Black Point..........

basalt............

Caldera.................................. . 10

Cathedral Valley----------------------- 7

Chinaman Lagoon -....................... 2

Clndercones.. ... 13-14,17

Cold Bay.. 1,2

Copper.___._...__ - .___ 7

Craters ......... .............. 11,12,14

Description of area. .- .............. 2,4

Dikes-... - 5,7,8

Double Crater Volcano..........__._.... 12

Dushkin basalt.... --. 8-9,12,13

Dushkin Lagoon... .............._..-... 6

Emmons Lake..._--_..............._.. 10,13

Faults. -..--. 15

Flows, lava-.. 8-10,13-14,17

Folds 5,15,17

Forests, ancient.----------------_-...-...-. 17

Fort Eandall-... ............................. 1,2

Fossils, plant - 6-7

Fumaroles __.___......._....__.... 13,15

Glacier Eidge....------------------------ 12

Glaciers.. .. 5,14,17

Gold....-:.. .-.. 8

Page 

History-. . 1-2

Hot Springs..__ __. - _. ._ 15

Icenelds ... ., 12,13

Indian Head....._......................... 6

Ivan Island.._ _ _ _ - - - 2

Jointing, columnar.....-- -----.---.-------- 8-9

King Cove.-------.----------------------- 2

Lagoons._._.__..... ... .......... 4

Lenard Harbor..._..._._. ._.... .- 2

Little Pavlof Volcano 12

Long John Lagoon..--.-.--....--.-----.-.-.. 10

Lowland.. _.................__._ 4

Moraines 5,12,14,17

Moss Cape_. 

Mt. Dutton... 

Mt. Emmons. 

Mt. Hague....

Necks. 5,7,8

Pavlof Bay..--..-.....---.---.-.-.--.. 2

Pavlof Sister.......-...---.--.-.---- ----- 11

Pavlof Volcano-...----.--------------------. 1,2,11

Plugs ._ . 5,7,8

Port Moller... 2

Beefs. 

Eift..

SeaCllffs . - 

Sea stacks..___.......-..-.. .._..

Sills 

Stepovak series._ ......__.__..

Stocks. 5,6,7,8,17

Strato-volcanoes._ ..-.-....___._ 10-13,17

Streamflow...__............................ 4

Sulfur....-... -. 15

Tuff..._t ... 6-7,17

Vegetation....._.......................... 4,15

Volcanic activity, future - . _ ----. 17

historic._.-...-- -..- -.---- ----- 1C

Volcano Bay.. ...._...................... 2

o

Water supply....__.____.... . ._.. ..- 4-5

19