Some Effects of Recent 

Volcanic Ash Falls 

With Especial Reference 

to Alaska

By RAY E. WILCOX

INVESTIGATIONS OF ALASKAN VOLCANOES 

GEOLOGICAL SURVEY BULLETIN 1028-N

Prepared in cooperation with the 

Office, Chief of Engineers, 

U.S. Army

UNITED STATES GOVERNMENT PRINTING OFFICE, WASHINGTON : 1959
UNITED STATES DEPARTMENT OF THE INTERIOR 

FRED A. SEATON, Secretary

GEOLOGICAL SURVEY 

Thomas B. Nolan, Director

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

Washington 25, D. C. Price 30 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 and Alaska Peninsula area. The first field studies were made during the years 

1946-48. The results of the first year's field, laboratory, and 

library work were hastily assembled as two administrative reports, and most of these data have been revised for publication 

in Geological Survey Bulletin 1028. Part of the early work was 

published in 1950 in Bulletin 974-B, "Volcanic Activity in the 

Aleutian Arc," and in 1951 in Bulletin 989-A, "Geology of Buldir 

Island, Aleutian Islands, Alaska," both by Robert R. Coats. Additional fieldwork was done during the years 1949-54. Unpublished 

results of the early work and all the later studies are being incorporated as parts of Bulletin 1028. The investigations of 1946 

were supported almost entirely by the Office, Chief of Engineers, 

U.S. Army. From 1947-55 the Departments of the Army, Navy, 

and Air Force joined to furnish financial and logistic assistance. 

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, and to the several military departments for 

their support.

in

CONTENTS

	Page

Preface ................. . . . m

Abstract .___.....__. _ .. . .._... .... _._ _ _ . .__... ... -. 409

Introduction .-... ....._ . . . _..... . .. . . _... ........... _. ... ... ... 410

Geography .......... _.. __ . ...... . . _. .. 413

Character of Alaskan eruptions.......... - 415

Eruption of Mount Katmai in 1912.. . . 415

Eruption of Okmok Volcano in 1945. 418

> Eruption of Trident Volcano in 1952 _______......_ 419

Eruption of Mount Spurr in 1953 420

' Eruptive sequences -.- - ..... - . . -- 423

Distribution of ash fall... _-. -........ . . . 426

Mount Katmai ......... .... ....... . .......... . 427

Hekla .._...._. .__.__._ .. _. _ : _ ._ . _ ._.. 428

Volcdn Quizapu . --.._. .._..________. ___...__ ....._____ ...___._....__ ___ ._ - .- 432

Gunung Kelud ...... . .............. ... 434

Paricutin ...._..__.._____..__._ _____._____.. __.__.___.._.___ __.___.________ _..- 435

Meteorological factors in Alaska . -.. .. . 438

Effects of eruptions ... - - . 441

Public health and safety.__..________._...._........._ __.._....... ....._. _..........- . 442

Buildings _..... ...................................... ....._..... ........................... .... 447

Utilities, transportation, and communication ............. . .. 447

Agriculture and related activities . ...... .. 450

Immediate effects of ash fall-.--- --- .. 451

* Long-range effects of ash fall ....__ ._. 456

Recolonization by natural vegetation. . . . ..._._ . . .. 462

Literature cited .... ...........______..._.. .__.__.___._. ~ 470

Index ..-- . __ .. _. _ _.. 475

ILLUSTRATIONS

[Plates are in pocket]

PLATE 54. Map of Alaska Peninsula and Aleutian Islands.

55. Map montage of average upper-air wind directions 1948-53 

for Anchorage, Alaska.

56. Map montage of average upper-air wind directions 1948-53 

for Kodiak, Alaska.

57. Map montage of average upper-air wind directions 1948-53 

for Dutch Harbor, Alaska.

58. Map montage of average upper-air wind directions 1948-53 

for Adak Island, Alaska.
Page

FIGURE 62. Map of Mount Katmai and the Valley of Ten Thousand 

Smokes, Alaska, showing thickness of ash deposits from 

the eruption in June 1912 . .... 416

63. Map of area affected by ash from the eruption of Mount

Spurr, Alaska, in July 1953 424

64. Map of Hekla volcano, Iceland, showing thickness of ash

deposits from the eruption in March 1947 .......... ... ...... 430

65. Map of route of airborne ash from the eruption of Hekla

volcano, Iceland, in March 1947 431

66. Graph showing size range of ash fall in 1947 at increasing

distances downwind from Hekla volcano in Iceland- 431

67. Map of successive positions of ash front from the eruption

of Volcan Quizapu, Chile, in April 1932- 432

68. Map showing the thickness of ash deposits from the eruption of Volcan Quizapu, Chile, in April 1932. .. 433

69. Map of Java, showing bilateral distribution of ash fall from

the eruption of Gunung Kelud in May 1919 .. 435 /

70. Graph showing variation of silica content of 1919 ash fall

of Gunung Kelud in Java, with distance . . 435 t

71. Map of vicinity of Paricutin in Mexico, showing thickness

of ash deposits in 1946-.--.. .- 437

72. Map of vegetation destruction in the eruption of Mount

Katmai, Alaska, in 1912 ........ ......- . 465

VI
INVESTIGATIONS OF ALASKAN VOLCANOES

SOME EFFECTS OF REGENT VOLCANIC ASH FALLS, 

WITH ESPECIAL REFERENCE TO ALASKA

By RAY E. WILCOX

ABSTRACT

Most historic and late prehistoric volcanic eruptions of Alaska have yielded 

a high proportion of fragmental material in the form of ash, whose effects are 

felt over wider areas than those of lava flows because of the wide distribution 

of ash by winds. Some 6 cubic miles of fragmental material was erupted 

during the first 3 days of the spectacular Mount Katmai eruption of 1912, 

and much of it was spread over large areas of the Alaska Peninsula and 

Kodiak Island, producing extensive, but not permanent, damage. Less intense 

Alaskan eruptions were those of Okmok Volcano in 1945, Trident Volcano in 

1952, and Mount Spurr in 1953.

Because of the scantiness of records of Alaskan eruptions and their effects, 

data from several better documented eruptions in other parts of the world are 

used here to fill in the range of behavior expected of future Alaskan eruptions. 

The importance of wind directions, wind speed, and rainfall in affecting the 

distribution of ash fall is illustrated by the eruptions of Hekla in Iceland, 

Volcan Quizapu in Chile, Gunung Kelud in Java, and Paricutin in Mexico, 

and by that of Mount Katmai in Alaska. Wind rose diagrams compiled from 

upper-wind data at selected Alaskan stations enable crude estimates to be 

made of the probabilities of ash fall from future eruptions in particular 

Alaskan areas.

Much needless fear of volcanic eruptions can be prevented by a foreknowledge of the range of effects that may be expected. The danger from poisonous 

gases, for instance, is seldom present, especially at the distances of most 

Alaskan communities from the potentially active vents. Few historic Alaskan 

lava flows have extended more than a few miles from their sources, and ash 

fall from the moderate activity that characterizes the great majority of 

Alaskan eruptions is commonly less dangerous than it is inconvenient. Nevertheless, volcanic activity in Alaska must command an attitude of respect 

because of its great potential and because of the chance that great damage 

will be done by the occasional extraordinarily strong eruption.

A mantle of ash more than a few inches thick over the countryside can 

radically increase runoff, with accompanying important effects on water 

supply, transportation, and agriculture, not only during, but also for some 

time after, the ash fall. Floods and mudflows may damage travel arteries, 

water reservoirs, and crop land. Ash fall itself may totally destroy growing

409
410 INVESTIGATIONS OF ALASKAN VOLCANOES

crops; but if the deposit is not more than a few inches thick, as at Kodiak 

Island in 1912, the next few seasons' plantings may result in normal or even 

improved harvests because of the beneficial mechanical and chemical effects 

of the ash that is worked into the old soil. Volcanic ashes commonly contain 

important amounts of calcium, potassium, and phosphorus available for plant 

nutrition some are rich enough to encourage their use as fertilizers. The 

nearly complete lack of available nitrogen in most volcanic ash and the special 

chemical and physical properties of raw ash impose handicaps to its direct 

utilization as a soil, however, and these characters must be modified by some 

means for successful cropping.

The recovery of natural vegetation may make great progress in only a 

season or two in areas where the ash fall deposit is less than a foot thick and 

rainfall is adequate, as was shown at Kodiak Island after the eruption of 

Mount Katmai in 1912. With greater thickness of ash or in drier climate, the 

rate of recovery may be proportionately slower; the initial lack of available 

nitrogen in the raw ash appears to be an important obstacle. On bare lava 

flows the rate of recovery is enormously slower than on ash under similar 

climatic conditions; it is delayed both by the lack of nitrogen and by the slow 

rate of breakdown of the lava to a soil. The course of recovery usually does 

not wait on the formation of a residual soil, however, for plants get a foothold 

in crevices partly filled by airborne dust. In the case of lava flows covered by 

ash-fall deposits of the same eruption or by reworked clastic material, the 

progress of colonization by plants becomes much the same as that on ash fall 

alone.

INTRODUCTION

More than 250 separate eruptions have been observed from 39 

Alaskan volcanoes during slightly less than 200 years of recorded 

history of the region, and many more eruptions must have gone 

unobserved in isolated areas. The frequencies of eruption have 

apparently varied considerably from decade to decade, and according to Coats (1950) eruptions have occurred with greater 

frequency about the years 1770, 1790, 1830, 1910, and 1930. There 

have usually been one or two eruptions a year, and no doubt 

similar behavior may be expected in the future. This paper will 

present descriptions of several past volcanic eruptions in Alaska, 

and, with the aid of this and information from certain eruptions in 

other parts of the world, will attempt to explore the problems that 

might have to be solved by communities or by organizations 

operating in the Alaskan region. Although ready solutions are 

not offered, it is hoped that this discussion will result in an 

awareness of the nature and scope of the problems that will help 

in dealing with them when they arise.

The writer is indebted to colleagues in the Geological Survey, 

especially G. A. Macdonald, for helpful criticism and suggestions 

in compiling this paper. An early draft of the manuscript was 

read and criticized by Dr. V. H. Cahalane of the New York State
SOME EFFECTS OF RECENT VOLCANIC ASH FALLS 411

Museum, and by Dr. W. D. Keller and Dr. E. R. Graham of the 

University of Missouri, and their help is gratefully acknowledged. 

Thanks are due Dr. Harry Wexler of the U.S. Weather Bureau 

for helpful discussion and for making available the date on which 

the map montages of figures 12 to 15 are based. The Coast and 

Geodetic Survey kindly furnished copies of the seismic record at 

College, Alaska, of the period before and during the eruption of 

Mount Spurr on July 9,1953.

For the purpose of the present discussion the volcanic phenomena can be divided into two types: (1) lava flows, ash flows, and 

volcanic landslides; and (2) ash falls and gases. Damage to 

human habitation by flows of lava and ash has not figured prominently in Alaska, mostly because they extend only short distances 

from the volcanoes; in inhabited areas, however, the destruction 

could be complete. Damage by ash falls and gases may extend 

many miles downwind and be accompanied or followed by damage 

from floods and mudflows. Most consideration is here given to the 

effects of ash falls, both because of their more common occurrence 

and wider extent and because there seem to be more chances to 

reduce their harmful effects by directed effort.

The present paper does not deal with seismic sea waves 

("tsunamis", often incorrectly called "tidal waves") and seiches 

generated by submarine earthquakes, some of which may be 

associated with volcanic eruptions. For these phenomena the 

reader is referred to Gutenberg and Richter (1954, p. 94) for a 

general discussion and especially to Imamura (1937, p. 126), who 

discusses them with special attention also to volcanic earthquakes 

and volcanic eruptions. Also left out of consideration here are the 

possible indirect effects of volcanic activity on climate. These 

effects, due perhaps mainly to absorption of sunlight by extremely 

fine ash blown to great heights in some major eruptions and 

spread by winds to form a world-wide blanket, have long been the 

subject of controversy and have recently been discussed by Wexler (1951).

The" area seemingly most likely to be affected by volcanic 

activity includes not only the active volcanic zone itself, extending 1,600 miles from Mount Spurr near Anchorage southwestward 

out the Alaska Peninsula and westward nearly to the end of the 

Aleutian Islands chain (pi. 54), but also the adjacent areas that 

might be reached by ash falls, principally Kodiak Island, the 

Kenai Peninsula, and even points farther east. Few historic 

eruptions have been noted in other parts of Alaska, but there 

are several other areas in which the volcanic activity cannot with
412 INVESTIGATIONS OF ALASKAN VOLCANOES

certainty be said to be extinct. In point is the late prehistoric 

eruption that blanketed the White River near the Canadian 

border with a great ash blanket, possibly about 1,400 years ago, 

according to Capps (1915). Here, also, should be noted the 

several mild steam and "smoke" eruptions from Mount Wrangell, 

suspected puffs from nearby Mount Blackburn and Mount Sanford 

in the Wrangell Mountains 200 miles east of Anchorage, and 

finally the very recent volcanic ash deposits around Mount Edgecumbe on Kruzof Island in southeastern Alaska and the Indian 

legends of its activity. Volcanic rocks and deposits of recent 

origin in British Columbia and the Yukon have been listed by Hanson (1934), and they indicate the possibility of eruptions from 

centers in areas adjacent to Alaska.

The geology of the volcanic region is known only in reconnaissance. Spurr's (1900) survey of southwestern Alaska gives most 

of the meager record of the appearance of the Katmai country 

before its physiognomy was drastically changed by the eruption 

of Mount Katmai in 1912. Atwood (1911) outlined the geology 

from rapid reconnaissance through parts of the peninsula and 

adjacent islands. Martin and Katz (1912) described the region 

near Iliamna Volcano, and Smith (1925) and Knappen (1929) 

briefly described Aniakchak volcano. Capps (1929, 1930, and 

1935) described the geology of the southern Alaska Range, including Mount Spurr, the volcano at the extreme northeastern end of 

the volcanic zone, and furnished notes (Capps, 1934) on the 

geology of several islands in the Aleutian chain. Volcanic activity 

in the eastern Aleutians is briefly described by Jaggar (1908) in 

the account of his 1907 expedition. The volcanological and 

petrological results of the National Geographic Society's early 

expeditions to Mount Katmai are admirably reported by Griggs 

(1918, 1919a and 6,1922) and by Fenner (1920, 1923, 1925, 1930, 

and 1950). Finch (1934, 1935) reported on the activity of Shishaldin Volcano and Akutan Peak in the eastern Aleutians.

From 1946-54 the Geological Survey did reconnaissance geologic mapping, together with some geophysical work and observation of volcanic activity at selected localities in the Aleutians. 

The record of volcanic activity is thus somewhat more complete 

for this than for former periods, but many gaps exist in the 

record even after 1946. A list of historic eruptions was compiled 

by Coats (1950) and a more complete summary of Alaskan volcanoes is being prepared by Coats for the "Catalogue of Active 

Volcanoes of the World," to be published by the International 

Volcanological Association. Preliminary reports have been made
SOME EFFECTS OF RECENT VOLCANIC ASH FALLS 413

on various parts of the Aleutians and the peninsula (Simons and 

Mathewson, 1956; Kennedy and Waldron, 1956; Coats, 1956a, b, 

and c) and others are in preparation. In 1953 and 1954 the National Park Service, in cooperation with the National Geographic 

Society and the Department of Defense, sponsored an expedition 

into the Katmai National Monument to study problems of geology, 

botany, and zoology arising from the 1912 eruption; the results 

are being prepared for publication by G. L. Curtis, V. H. Cahalane, 

and others.

GEOGRAPHY

The backbone of the Alaska Peninsula is the Aleutian Range, a 

zone of volcanoes and folded and faulted mountains (pi. 54) extending southwestward from the nonvolcanic Alaska Range. Still 

farther southwestward along the peninsula, the mountains are 

lower and the peninsula narrower and more indented; it is finally 

terminated by a saddle below sea level (Isanotski Strait), and 

the mountain range is continued as the mostly submerged Aleutian 

chain of island volcanoes. This chain extends westward in a long 

arc for a thousand miles with generally decreasing size of islands 

and increasing lengths of open water between. Kiska Volcano, 

200 miles short of the western end of the chain, is the westernmost 

volcano known to have been active in historic time. Buldir volcano, 50 miles farther west, has been active in postglacial time 

and cannot be said to be extinct. Three hundred miles of open 

water separate Attu Island, the westernmost of the American 

Aleutian islands, from the Russian Komandorskiye Ostrova, which 

in turn lie 200 miles from the Kamchatka Peninsula, part of a 

separate volcanic arc.

Northwest of the peninsula, the Bering Sea is quite shallow. 

The 600-foot depth line runs generally northwest from Unimak 

Pass and marks the beginning of a relatively steep slope westward 

down to depths of 12,000 feet. To the north of the middle and 

western parts of the Aleutian chain, the floor of the Bering Sea 

is quite flat, mostly at depths about 12,000 feet, broken only by 

the curving submerged ridge of Bowers Bank, which extends 150 

miles northward from Amchitka Island. The south flank of the 

submerged Aleutian mountain range slopes down to a maximum 

depth of about 24,000 feet in the Aleutian Trench, thence the 

bottom rises to the rolling floor of the Pacific Ocean at depths 

between 15,000 and 20,000 feet. The beautiful geometric plan 

of the arc and of the trough in front of it has counterparts in 

the several other island arcs surrounding the Pacific basin; the
414 INVESTIGATIONS OF ALASKAN VOLCANOES

Kamchatka-Kurile arc, the Japan arc, and the Philippine arc are 

examples, which, with the Aleutian arc, undoubtedly reflect major 

crustal structures. All are volcanically and seismically active, and 

their volcanoes erupt materials chemically and mineralogically 

similar. The common structural interpretation is that the troughs 

mark the traces of major crustal fractures sloping toward the 

concave sides of the arcs (northward in the case of the Aleutians) , and that there has been overthrusting along this fracture. 

The locus of surface volcanic activity lies some miles inside the 

trace of this supposed fault zone, presumably above the intersection of the major fracture with molten or potentially molten 

zones at depth.

The young volcanic rocks of the Aleutian arc are mainly of 

basaltic and andesitic composition, with minor amounts of 

rhyolitic or dacitic materials. Chemically they belong to the 

"calcic" suite of volcanic rocks, that is, one in which the ratio of 

calcium to alkalies is relatively high for a given silica content. 

On the peninsula the exposures of young volcanic rocks are subordinate in area to older sedimentary, metamorphic, and plutonic 

igneous rocks; on the islands the reverse is generally true, and 

there also much of the sedimentary rock is composed of only 

slightly reworked volcanic materials.

Most of the civil communities in the neighborhood of the main 

Alaskan volcanic zone are small and the intervening areas sparsely 

populated. Chief industries are fishing, cattle and sheep raising, 

and a limited amount of farming. The small population near the 

active volcanoes of Alaska is in sharp contrast to the situation in 

such areas as Java or near Vesuvius and Etna in Italy, where 

intense agricultural development extends to the bases or even 

up the flanks of intermittently active volcanoes. As pointed out 

by Sapper (1926), population density and economic development 

are important considerations in choosing practical protective 

measures against effects of volcanic eruptions.

The mainland end of the Alaska Peninsula is forested, but 

trees are virtually absent southwest of a line through Kodiak Island and the Mount Katmai region. Because the trees along this 

"timberline" are mostly young and not particularly stunted, Griggs 

(1934) concluded that the timberline is moving slowly westward 

under the influence of postglacial reforestation. On the islands 

a few scrub willows are found in protected valleys, but in general 

the trees grow and survive only where specially cared for. Even 

these do not thrive and their seedlings rarely persist (Bruce and 

Court, 1945). The dominant cover on the islands and the western
SOME EFFECTS OF RECENT VOLCANIC ASH FALLS 415

part of the peninsula consists of grasses, sedges, mosses, and 

ferns growing on soils that have been designated as "tundra" type 

by Kellogg and Nygard (1951). Animal life on the islands is 

limited to mice, shrews, ground squirrels, foxes, rabbits, birds, 

and a few imported herds of sheep and caribou. Alaskan brown 

bear are known on Unimak Island, at the end of the peninsula, 

but not farther west.

CHARACTER OF ALASKAN ERUPTIONS

Much of the material erupted from Alaskan volcanoes during 

historic time has been pyroclastic, that is, it has been thrown 

out in a fragmental condition as ash, lapilli, or bombs, to travel 

downwind various distances depending on its f rothiness or fineness 

and on the intensity of the winds. A minor quantity has been 

erupted as lava. The large amount of pyroclastic material in the 

older deposits of the peninsula and the islands attest to much 

explosive activity in the late prehistoric eruptions also.

The effects of predominantly explosive eruptions are different 

than those of predominantly effusive (lava-producing) eruptions. 

The ash of the explosive eruptions may be distributed much 

farther and over greater areas than the lava of effusive eruptions, 

and it may be accompanied by reactive gases and fumes and 

chemicals absorbed on the ash particles. The ash, as deposited, 

is generally more vulnerable than lava to weathering processes 

and is potentially more adequate as a soil, mainly because of the 

greater amount of surface exposure to soil-forming solutions; in 

addition, it is easily reworked and mixed into old soil, either 

naturally or artificially, because of its mechanical condition.

Four historic Alaskan eruptions, namely, the 1912 eruption of 

Mount Katmai, the 1945 eruption of Okmok Volcano, the 1952 

eruption of Trident, and the 1953 eruption of Mount Spurr, provide examples of the range of past explosivity and intensity, no 

doubt comparable to those of the future. The Mount Katmai 

eruption is justifiably famous for its great intensity and extensive 

damage. The others were comparatively moderate and perhaps 

more representative. It is important to note that three of these, 

Mount Katmai, Trident, and Mount Spurr, had no record of 

previous eruptions in historic time and to bear in mind that some 

future eruptions no doubt will come from vents not known to 

have been recently active.

ERUPTION OF MOUNT KATMAI IN 1912

In early June 1912, Mount Katmai, after apparently centuries 

of quiescence, burst out in an eruption that was the greatest
416 INVESTIGATIONS OF ALASKAN VOLCANOES

volcanic catastrophe in the recorded history of Alaska. More 

than 6 cubic miles of ash and pumice were blown into the air 

from Mount Katmai and the adjacent vents in the Valley of 

Ten Thousand Smokes. Measurements of thickness of ash by the 

1953 Katmai Expedition led Curtis (1955) to conclude that, contrary to previous opinions, almost all the material was erupted 

from vents in the Valley of Ten Thousand Smokes and that Mount 

Katmai played only a subordinate role in the eruption. Much of 

the ash was carried by winds into the southeastern and northern 

quadrants (fig. 62). Although a great deal of it fell at sea,

® C-7

Location of sample dredged by Menard

FIGURE 62. Map of Mount Katmai and the Valley of Ten Thousand Smokes, Alaska showing 

thickness of ash deposit from the eruption in June 1912 (after Griggs, 1922, and Menard. 1953).

vegetation was smothered over thousands of square miles on the 

mainland and on Kodiak Island. The maximum depths of ash fall 

material in the vicinity of Mount Katmai were more than 50 

feet, while 100 miles to the southeast at Kodiak village it was only 

about 10 inches enough, however, to cause extreme damage to 

buildings and crops.

The most complete account of the eruption of Mount Katmai 

is given by Griggs (1922), who alludes to the lack of definite
SOME EFFECTS OF RECENT VOLCANIC ASH FALLS 417

information about events leading up to the eruption and what 

was happening during the eruption. As much as 5 days before 

the eruption, earthquakes began at Katmai village on the Pacific 

shore some 20 miles from the volcano. The people of Katmai 

village had become so frightened by earthquakes that, on June 4, 

they moved 10 miles down the coast to camp at Cap Kubugakli, 

and when the eruption broke out on June 5, they proceeded another 

20 miles along the coast to the village of Cold Bay (now known 

as Puale Bay). Villagers at Savonoski, about 20 miles northwest 

of Mount Katmai, likewise were frightened by the preliminary 

earth tremors but did not begin their move until the eruption 

started on June 5. Then, with great difficulty, they made their way 

the 50 miles to the village of Naknek on the north coast of the 

Alaskan Peninsula.

On the evening of June 5, a supposed eruptive cloud was seen 

from Cold Bay (now Puale Bay), 40 miles southwest of Mount 

Katmai, and during the morning of June 6 several large explosions 

were heard in Seldovia, 150 miles northeast. At about 1:00 p.m. 

on June 6 the great explosions of the main phase of the eruption 

began and continued for 2^ days. The major explosions occurred 

at about 3:00 p.m. and 11:00 p.m. on June 6 and at about 11:00 

p.m. on June 7. From what can be made of the fragmentary accounts it seems that fairly strong eruptions continued for several 

weeks, after which there was a general diminution of the amount 

of ash being erupted but a continuation of earth tremors and gasladen explosions for several months.

No seismographs were close enough to record the preliminary 

earthquakes, of which there were probably many too weak to be 

felt, but which would have been recordable instrumentally. The 

quakes accompanying the first few days of the eruption itself, 

however, were so strong that they were picked up by seismographs 

at Victoria, British Columbia, and Seattle, Wash. Air shock waves 

of the explosions were reported to have been seen from Seldovia, 

150 miles away, and the noises to have been heard at Juneau, 750 

miles away. Curiously, the noises were not reported to have been 

heard at Kodiak, only 100 miles away; this was attributed to the 

muffling effect of the ash cloud, presumably already in the air 

between the volcano and Kodiak Island. It has been suggested 

also that such phenomena may be due to refraction of sound waves 

by a layered atmosphere, perhaps in the manner in which Gutenberg and Richter (1931) accounted for the abnormal audibility, 

at several localities far inland, of naval gunfire off the coast of 

California.
418 INVESTIGATIONS OF ALASKAN VOLCANOES

All the observations of explosions were made from a great 

distance, and it was universally assumed that the eruptions took 

place from Mount Katmai. When Griggs and the National Geographic Society party finally reached the scene several years later 

they found that a huge caldera, 2 miles in diameter, had formed 

in the summit area of Mount Katmai. In addition, they found a 

valley extending westward from the western base of the mountain 

filled with a still steaming mixture of ash and lava lumps that 

must have moved as a tremendous ash flow from a source near 

the base of Mount Katmai. They concluded that this material 

had erupted first, and then been covered by several feet of layered 

airborne ash from the eruption of Mount Katmai. Actually their 

observations do not rule out the possibility that almost all the 

eruptive material came from the valley vents, as suggested by 

Curtis (1955). The shape of Mount Katmai before the eruption 

is only imperfectly known and there has been speculation whether 

a small crater might already have been present in its summit. It 

seems fairly well agreed that during, or very soon after, the 

eruption the great caldera formed in its summit, probably by 

collapse.

ERUPTION OP OKMOK VOLCANO IN 1945

Okmok Volcano is a caldera, 6 miles in diameter, in the broad 

mountain dominating the northeastern portion of Umnak Island, 

200 miles west-southwest of the tip of the Alaska Peninsula. 

Eight eruptions had been reported before 1945, probably originating from more than one vent in the broad floor of the caldera; 

the last reported had occurred in 1938.

On June 1, 1945, a sharp earthquake was felt at the Umnak 

Island army base on the east side of the mountain. Nothing otherwise unusual was noted, and the rim of the caldera was hidden 

by persistent low clouds. On June 4, pilots reported a column of 

black ash rising from the southern part of the caldera to a height 

of 9,000 feet, and that evening the clouds lifted above the rim to 

reveal red reflections. Attempts to reach the site of eruption 

were thwarted until June 10 when the weather cleared. On this 

date ash was being erupted copiously from a small cinder cone 

near the southwest edge of the caldera floor and lava was flowing 

from the base of the cone. The lava stream broadened to about 

40 feet and flowed at a rate of about 30 feet per minute at the 

surface. It was flowing in a wide circle to the east and north, 

undermining a local mass of ice in the southern part of the 

caldera. The airborne ash, being carried southeasterly at that 

time, had formed a coarse deposit several feet thick on the ice of
SOME EFFECTS OF RECENT VOLCANIC ASH FALLS 419

the caldera floor and several inches thick on the rim of the caldera. 

Nine miles southeast only a fraction of an inch of ash was deposited. 

The lava flow extended 4 miles in about a month of intermittent, but declining, activity. By late July, lava effusion practically 

ceased and the amount of ash in the eruptive column generally 

decreased until only steam was emitted, and that only in weak 

surges. In December 1945, there was a brief resurgence of activity with a small lava flow and light ash fall, In all, no significant damage was done by the ash fall, and it was apparent at an 

early stage that any large amount of lava would be effectively 

confined within the caldera.

ERUPTION OF TRIDENT VOLCANO IN 1952

Trident Volcano, with no record of previous historic activity, 

broke out in a flank eruption on February 15, 1952. Only about 5 

miles southwest of Mount Katmai and 3 miles southeast of the 

vent area of the Valley of Ten Thousand Smokes, this was the first 

appreciable eruption in the Mount Katmai area since 1912, 

although there have been minor ash eruptions from close by 

Mount Mageik, Mount Martin, and Novarupta, and a few minor 

outbursts from Mount Katmai itself.

Much ash was ejected from Trident in the initial bursts and 

reached altitudes near 30,000 feet (Snyder, 1954), but clouds and 

bad weather prevented immediate identification of the source. 

The cloud cover persisted for 2 days and aerial observations, 

limited largely to the material rising above the clouds, indicated 

that besides Trident, at least one other vent, perhaps Mount Martin or Mount Mageik, must have been contributing to the eruptions 

of the first several days.

On February 18, the weather cleared to show a gray column of 

ash and steam rising from a vent at about 3,600 feet on the 

southwest flank of Trident, but only the usual amount of steam 

from Mount Martin and Mount Mageik. The Trident vent was 

apparently just beginning to produce a viscous blocky lava flow 

about 800 feet in diameter at the vent. Reports of "long streams 

of molten lava" were obviously erroneous and perhaps had their 

basis in the mudflows and floods composed of ash and melt water 

that coursed down the flank of the mountain.

Observation was hampered by the characteristically bad weather 

of the region at that season of the year, but flights on February 

21 and 27 and March 4, 9, and 11 showed much-reduced explosive 

activity and ash production while the viscous lava built up a domeshaped lobe three-quarters of a mile broad and a mile long downslope. Explosions recurred briefly on March 24. During the next
420 INVESTIGATIONS OF ALASKAN VOLCANOES

few months the lava dome grew in height by addition of lava 

but increased little in length. Sometime before June 2, a landslide 

carried material from the toe of the lava dome another mile 

downslope. Brief minor explosions of ash continued through the 

summer, and another lava flow, apparently of more fluid material, 

moved out from the source area in a tongue that eventually 

reached a length of about 2i/£ miles. Only a few minor ash 

eruptions were noted during the fall and winter of 1952.

During the period of intense eruption, few observations of directions of ash transport could be made, and the inaccessibility of 

the area prevented measurements on the ground. On February 

18, a blanket of ash was seen to cover the snow west of the vent, 

but new snow had effectively concealed the pattern of ash distribution of the first 2 days of eruption. All observations until February 27 noted winds carrying ash westward or northwestward, 

and ash covered the ground as far as 50 miles, around Naknek 

Lake. Subsequently the ash of subsiding eruptive surges was 

carried mainly into the southeast and east quadrants.

The volume of the lava erupted before June 1953 was computed 

to be between 300 and 400 million cubic yards (Snyder, 1954), 

and later information indicates that the volume of the dome approached 500 million cubic yards by October 26. The volume of 

ash, most of which was expelled in the early part of the eruption, 

is estimated to have been between 7 and 70 million cubic yards, 

making a possible total of 570 million cubic yards on 0.24 cubic 

mile of material.

ERUPTION OF MOUNT SPUBB IN 1953

At 5:00 a.m. on July 9, 1953, a glacier-filled vent on the south 

flank of Mount Spurr erupted with tremendous violence, shooting 

a mushroom cloud like an atom-bomb cloud to a height of 60,000 

or 70,000 feet in a matter of some 40 minutes. By good chance 

the eruption was witnessed from its onset by plane pilots whose 

photos and descriptions provide a valuable record of this type of 

eruption (Juhle and Coulter, 1955). The bulk of material of the 

eruption was blown out in only a few brief surges on July 9, and 

was carried due eastward across the city of Anchorage, 80 miles 

away. No lava flows occurred, and during the next few weeks 

the eruption subsided to a weak emission of steam.

The outbreak did not occur at the summit of Mount Spurr, but 

at a point about 7,000 feet above sea level on the south shoulder 

of the mountain just above the gorge of the Chakachatna River. 

No historic record of eruptions of this or other vents on Mount 

Spurr prior to 1953 are known, except for minor emissions of
SOME EFFECTS OF RECENT VOLCANIC ASH FALLS 421

steam in 1927. Photos of Mount Spurr taken before July 9 show 

a continuous cover of ice over the area of the July 9 vent, with 

small glaciers extending down the flank. A mantle of pumice 

under the turf of the region, noted by Capps (1935, p. 87), indicates a relatively recent eruption from this or nearby vents.

The only premonitory symptom recognized seems to have been 

an increased fumarolic activity in the peak area noted by pilots 

during the latter part of May (Fairbanks News-Miner, May 21, 

1953, p. 9). The seismic record at College, 300 miles northeast of 

Mount Spurr, showed that for the evening of July 8, and early 

hours of July 9, several brief disturbances occurred that may or 

may not have been connected with the imminent eruption. Because of their relatively short oscillation periods, which is characteristic of volcanic (local) quakes, it seems entirely possible 

that they may have been precursors of the eruption, although no 

epicenter distance determinations have been made on the records 

of these quakes. At a few minutes before 5 a.m. on July 9, the 

seismograph began recording swarms of confused "microseisms" 

(vibrations of small intensity and short period compared to 

those of a normal earthquake), which were quite different in 

character from normal microseisms.

The following pilots' account of the initial phase of the eruption 

is quoted from an Air Force press release of July 10,1953:

At 05h 05m Lieutenant Metzner noticed a column of smoke 60 miles ahead 

that was about 15,000 feet high and one-eighth mile wide. As he approached 

the smoke it was apparent that the eruption causing it was becoming increasingly severe with the smoke growing rapidly in height. At about 25 miles 

distance, the volcano was recognized as the 11,070-foot high Mount Spurr. 

Both planes approached the mountain at about 15,000 feet and circled the 

volcano at about 05h 25m. They noticed the continuing increase in the intensity and size of the column of smoke with lightning flashes through its core 

every 30 seconds. Smoke issued from the volcano in violent billows at the 

7,000-foot level of the mountain caused by huge subterranean explosions. 

Tremors on the mountainsides were visible from the aircraft and were followed by snow slides on the mountain. The smoke had by now reached the 

30,000-foot level, rolling upward and assuming the shape of the atomic bomb 

mushroom. Clouds of smoke were every shade of gray from black at the crater 

to pure white at the top. By this time the width had increased to about a mile 

at the base and 30 miles at its widest part.

About 05h 40m Lieutenant Metzner climbed in order to estimate the height 

of the mushroom. The top of the stalk, or the bottom of the mushroom, was 

30,000 feet and the top of the mushroom had climbed to 70,000 feet. Lightning 

was now flashing from top to bottom of the mushroom at three-second 

intervals.

At about 6h 00m volcanic ash began falling from the mushroom on all sides 

and finally made the entire area hazy. A clear definition of the volcano and 

the mushroom rapidly faded and the patrol returned .to its base.

Thus one gets a picture of a huge mushroom cloud, boiling upward to some 70,000 feet, and the beginning of ash fall as the 

mushroom spread and turbulence diminished. Wind from the
422 INVESTIGATIONS OF ALASKAN VOLCANOES

west carried the great sinking ash umbrella due eastward and 

allowed practically no ash to fall on the west side of the volcano. 

At 9:00 a.m. a pilot reported ash still being erupted in great 

quantities, but another observation at noon showed the activity 

to have greatly decreased. At 3:30 p.m. resumption of strong 

activity was reported, and other eruptions apparently took place 

during the afternoon or evening.

The "microseismic" activity recorded at College, Alaska, which 

had begun in earnest just before 5:00 a.m., increased in intensity 

until about 9:00 a.m., then diminished rapidly to the normal 

microseismic level. A similar disturbance began again at about 

3:30 p.m., built up to a climax by 5:00 p.m., and thereafter subsided rapidly. The coincidence of times of seismic disturbance 

and observed periods of strong explosive eruption leave little 

doubt that this peculiar seismic activity originated at Mount 

Spurr.

The ash cloud of the first eruptive surges of July 9 moved 

slowly eastward and by 11:00 a.m. the leading edge of the descending mushroom, by now greatly distorted, had spread out above 

Anchorage. While ash fell copiously on the northwest shore of 

Cook Inlet it was not yet falling in Anchorage, and the base of 

the ash cloud sloped upward to the east in its direction of movement. Fine ash started falling in Anchorage shortly before noon, 

when darkness caused the automatic switching system to turn on 

the street lights, and continued to fall copiously until 3:00 p.m. 

After 3:00 p.m. the rate of ash fall decreased but some continued 

through the night. By early morning only a pall of dust hung 

over the area.

On July 10 at 5:00 a.m. the vent was only steaming. At 3:30 

p.m. an especially strong surge of ash-laden steam rose to 20,000 

feet. From July 11-16, according to Juhle and Coulter (1955), 

the eruption consisted only of white steam clouds rising to maximum altitudes of 20,000 feet and occasional puffs of black dust 

and rock debris, most of which fell back into the throat of the 

volcano.

A mudflow or debris-laden flood must have occurred July 9 or 

10, for Juhle and Coulter on their arrival at the volcano July 11 

found a fresh debris dam across the Chakachatna River just below 

the Mount Spurr vent and a new lake, 5 miles long. The mudflow 

may have been caused by the torrential rains of the initial eruption or by melt water from the ice that apparently had filled the 

vent.

The zone of heavy ash fall covered an area some 25 miles wide
SOME EFFECTS OF RECENT VOLCANIC ASH FALLS 423

extending almost due eastward from Mount Spurr (fig. 63). 

Thickest ash (and lapilli) deposits were not far from the volcano, 

and the appearance from the air of bowed-over foliage in the 

Beluga Lake area indicated a thickness of ash of several inches. 

At Anchorage the deposit was variously one-eighth to one-fourth 

inch in thickness, decreasing still more to the eastward where 

ash fall was reported at Valdez and within 30 miles of Cordova, 

some 200 miles from the origin. Additional reports of ash fall 

came from Kenai, Kalgin Island, and as far south along Cook 

Inlet as Tuxedni Bay, 80 miles south of Mount Spurr, near 

Iliamna. This ash could have been from a branch of the main 

cloud of the morning eruption on July 9, or from the clouds 

of the afternoon eruptions, by which time the winds may have 

shifted.

ERUPTIVE SEQUENCES

Few generalizations on the behavior patterns of volcanoes are 

valid, but in most eruptions the eruptive behavior may conveniently be split into three phases: preliminary symptoms, outbreak 

and climax, and declining phase. From volcano to volcano and 

from region to region, these phases may bear quite different 

relations to each other in duration and intensity.

The preliminary symptoms are of great importance, for they 

often make possible the successful prediction of an impending 

eruption. They may include earthquakes, slow earth movements 

(such as tilt of the ground surface), and disturbances in the local 

magnetic and electrical fields. Until recently, the established volcano observatories, such as that in Hawaii, gave most attention 

to earthquakes and tilting in their efforts to find bases for prediction of eruptions. Within the last decade, however, enough 

data on magnetic and electrical effects have become available to 

suggest that these also may become useful, once the behavior 

pattern for a particular volcano is established.

The tilting of the land surface near a volcano has been interpreted as being due to a general swelling of the volcanic structure 

that is brought about by increase of internal pressure or temperature or both. Tilting generally amounts to only a few seconds 

of arc, and although it may be detected by precise leveling across 

the volcano flanks, it is much more convenient to record its progress by sensitive tiltmeters placed at strategic points on the 

flanks. Local earthquakes occur from time to time in most volcanic 

regions without any apparent direct relation to volcanic eruptions. 

When the frequency and intensity of quakes originating below a
424 INVESTIGATIONS OF ALASKAN VOLCANOES

li

<M.2

o _
SOME EFFECTS OF RECENT VOLCANIC ASH FALLS 425

particular volcano increase, however, it may be suspected that 

increasing volcanic pressure is causing rock failure and readjustments that may be the forerunners of an actual outbreak. Abnormal changes in the earth's local magnetic field and in local 

patterns of earth currents have been recorded in several areas, 

such as in the Japanese volcanic arc, in connection with volcanic 

eruptions, and observatories in several volcanic zones are making 

continuing studies of these phenomena in the hope that they will 

serve as indicators of impending outbreaks.

The actual outbreak of the eruption is usually sudden and may 

be regarded as the continuing crescendo of energy release that 

started with the premonitory earthquakes. After the initial outbreak the earthquakes commonly cease or decrease greatly in 

intensity and frequency. Eruptions commonly build up to a climax 

in a matter of hours or days and thereafter subside irregularly. 

Material may be erupted as flowing lava, pyroclastic blebs or 

fragments, or as both, accompanied of course by various amounts 

of gaseous products. Part, at least,.of the driving force of the 

eruption must be the pressure of the pent-up gases that, once an 

exit to the surface has been made, rush toward it pushing the 

lava along. If the lava is very fluid, the expanding gas can be 

released quietly at the surface to produce lava fountains and 

smooth flow, such as are typical of Hawaiian eruptions. If the 

lava is less fluid, the rapidly expanding gases may disrupt the 

molten material explosively to produce pyroclastic material, such 

as was the case with the eruption of Mount Spurr in 1953. It is 

perhaps more common to find a combination of effusive and explosive activity, as occurred in the eruption of Okmok Volcano in 

1945 and the eruption of Paricutin volcano in Mexico.

The declining phases of eruptions commonly continue for periods many times the length of the period from outbreak to climax. 

They are marked by intermittent resurgences of explosive or 

effusive activity, successive ones being of generally decreasing 

intensity and no doubt representing relief of minor pressures 

built up during readjustment to the new conditions. After the 

eruption is over and the record is complete, the climax of the 

eruption can often be pointed out easily in retrospect. During the 

eruption, however, it is not simple to say when the climax has 

been reached, for it is often approached in a series of explosions 

or surges of generally increasing intensity and sometimes increasing frequency. An observer who has witnessed several eruptions of the particular volcano might be better able to estimate 

when the decline begins, but unfortunately the explosive eruptions
426 INVESTIGATIONS OF ALASKAN VOLCANOES

of a particular volcano are spaced erratically and often at intervals greater than the life span of the observer. Hence, although 

the pattern and phase sequence outlined above may be applicable 

in the general case, the duration of the separate eruptive phases 

is not commonly predictable and the transition from one phase to 

the next not always recognizable at the moment.

To be able to interpret the seismic and other preludes to eruptive 

activity at a particular volcano requires an investment in equipment and research in the area through a period of several eruptions, so that the usual pattern of events preceding an eruption 

is indicated. Even then, in certain areas or at certain volcanoes, 

the seismic or other prelude may be too brief to provide sufficient 

advance warning of the impending eruption. At the present time 

the lack of funds and difficulties of instrumentation hinder the 

establishment of a network of stations for studying the behavior 

of Alaskan volcanoes. The brief record from 1949-53 obtained 

by the Geological Survey observatory at Adak Island concerning 

the seismic phenomena and intermittent eruptive activity of the 

nearby volcanoes of Kanaga and Great Sitkin Islands has been 

of only limited value in indicating eruptive symptoms. It is now 

apparent that the task of mapping the behavior patterns of the 

sporadically active volcanoes of this sparsely populated extensive 

geographic region in a manner that would be of direct application 

to the problems of prediction would require a considerable outlay 

of money as well as a generation or two of human effort.

DISTRIBUTION OF ASH FALL

Because of the high proportion of explosive eruptions from 

Alaskan volcanoes, the manner of transportation and deposition 

of the fragmentary products of such eruptions and meteorologic 

conditions of the area are of interest. As the information on 

Alaska ash falls is meager, records of several ash falls from volcanoes in other parts of the world those from Volcan Quizapu 

in Chile in 1932, Hekla in Iceland in 1947, Gunung Kelud in Java 

in 1919, and Paricutin in Mexico in 1943-52 have possible applicability to the Alaskan situation. The eruptions of the first three 

and the eruption of Mount Katmai in Alaska represent predominantly explosive eruptions in which the main bulk of material 

was ejected in the space of a few days or weeks and the resulting 

patterns of ash fall were relatively simple. The eruption of 

Paricutin represents a long-continued eruption through 9 years 

with complications in the pattern of ash distribution that were 

due to seasonal changes in wind direction.
SOME EFFECTS OF RECENT VOLCANIC ASH FALLS 427 

MOUNT KATMAI

The ash fall of the Mount Katmai eruption in Alaska in 1912 

was mainly in the quadrant east-southeastward across Kodiak 

Island, with a minor lobe to the north (p. 417). The map of ash 

fall thickness (fig. 62) is taken chief fly from Griggs' (1922) 

detailed book on the eruption, with slight modification of the 

isopachs (lines of equal thickness) in the Gulf of Alaska, where a 

dredged sample by Menard (1953) indicated somewhat thicker 

ash on the sea bottom than was inferred by Griggs.

According to Griggs (1922, p. 26) an area of 3,000 square miles 

was covered by ash a foot or more deep, and 30,000 square miles 

by more than an inch of ash. Small ash falls were also recorded 

at Fairbanks (550 miles distant), Juneau (750 miles) and in the 

Puget Sound region (about 1,500 miles). Griggs estimated that 

the total volume of ash fall was about 4% cubic miles, not 

counting the ash flow of the Valley of Ten Thousand Smokes.

Appreciable amounts of extremely fine ash blown into the stratosphere remained in suspension for months and caused spectacular red sunsets in many parts of the globe. The effect of 

the suspended ash on infall of solar energy, and thus on climate, 

has been discussed at length in several papers (Griggs, 1922, 

p. 33-44 ;Wexler, 1951).

At the village of Kodiak, 100 miles east-southeast, the ash 

began falling about 5:00 p.m. on June 6, following the unusual 

occurrence of thunder and lightning. Five inches of coarse ash 

were deposited during the night and some 6 inches of finer ash 

during the following two days. Subsequently very little ash fell 

there.

"Acid rains" were common at many localities, usually along 

with ash fall. This is spoken of in most reports as "sulfuric 

acid" although few actual determinations seem to have been made. 

According to newspaper accounts, on June 11 a "corrosive" rain 

fell at Seward, 250 miles from Mount Katmai, and at Cordova, 

360 miles distant, painfully burning some persons and damaging 

vegetation and exposed metal. Fumes near Cape Spencer, 700 

miles distant, were strong enough to tarnish freshly polished 

ship's brass in 15 or 20 minutes. On July 12, at Vancouver, 

British Columbia, 1,500 miles away, laundered linen goods of 

many housewives were reported to have been decomposed by the 

acid fumes. Curiously, no mention of damage to fabrics at points 

closer to the volcano was made by Griggs (1922), nor does he 

mention acid rains and fume damage at all at Kodiak. Perhaps
428 INVESTIGATIONS OP ALASKAN VOLCANOES

the other effects of the ash fall were so strong as to overshadow 

those of acids and fumes.

HEKLA

Much specific data and pertinent discussion on ash falls and 

their effects are furnished in a series of papers on the 1947 eruption of Hekla volcano in southern Iceland, published by the Museum of Natural History at Reykjavik (Thorarinsson, 1951, 1954; 

Einarsson, 1949a and b, 1950, 1951; and Kjartansson, 1951). 

Hekla had been dormant since 1845 and had come to be regarded 

by some as extinct. Precursory earthquakes to the eruption of 

March 29, 1947, were too faint to be recorded at the nearest 

seismograph, 70 miles away at Reykjavik, but a few nearby residents had noted peculiar rushing noises for several nights prior 

to the eruption, without having been aware of their origin. Several residents were awakened in the early hours of the 29th by 

brief tremors that rattled windows, and the vibrations increased 

notably during the last half hour before the outbreak. All these 

phenomena would probably have produced records on a seismograph in the immediate vicinity.

The visible eruption cloud started from a single crater at 6:40 

a.m. and rose very rapidly. To the accompaniment of earthquakes 

at 6:50 a.m. nearly the whole ridge line of the mountain split 

open, and eruptions spread along 2 miles of the fissure. By 7:00 

a.m. a white umbrella cloud condensing above the eruptive mushroom had reached a height of 85,000 feet and by 7:10 a.m. a height 

of some 88,000 feet with the top of the darker eruptive material 

not much lower. This singular-appearing white umbrella had 

nearly disintegrated by 7:40 a.m. while winds of 40 to 60 miles 

per hour at the intermediate levels rapidly pushed the darker 

eruptive cloud southward. The material being erupted at this 

time was only reaching heights of some 30,000 feet (the base 

of the stratosphere), and in midafternoon it was only reaching 

to about 18,000 feet where it was maintained for 2 days.

Most of the fragmentary material was erupted during the first 

hour: about 60,000 cubic yards of solids at a rate of some 16,000 

cubic yards per second (Einarsson, 1949a). Most of the lava 

probably flowed out in the first 10 hours, and the total of both 

lava and pyroclastic material ejected by the eruption, which 

continued at a much reduced rate for a year, is estimated at some 

520 million cubic yards. The lava flows covered a relatively small 

area, estimated at 18 square kilometers (7 square miles) on the 

slopes and at the base of the volcano.

The chemical composition of the erupted material changed
SOME EFFECTS OF RECENT VOLCANIC ASH FALLS 429

progressively during the eruption. The initial outburst was of 

brownish-gray material containing 62 percent silica and 9 percent 

total iron oxide; the later material was darker and contained 54 

percent silica and 13i/£ percent iron oxide (Einarsson, 1950). 

The Hekla eruptions of 1845, 1766-68, and 1693 behaved similarly. The initial material is apparently dacite and later material andesite near basalt in composition.

Closely associated with the eruption were minor flash floods 

and mudflows, the water of which was thought by Kjartansson 

(1951) to have come from condensed volcanic steam and melted 

snow and ice. The largest floods came from a series of tongues of 

water pouring down the north face of the elongate volcano, probably not more than a few minutes after the eruptive outbreak. 

The total volume of the floodwaters was estimated at 31/& million 

cubic yards of water. After gathering at the headwaters of the 

Ytri-Ranga they rushed down the 40 miles to the sea as one simple 

wave less than 3 feet high, taking only a couple of hours to pass. 

On the volcano flanks steam issued from the multiple flood streams, 

and many persons noted the tepid character of the water along 

the lower reaches of the streams.

The ash cloud at first moved southward and laid down a mantle 

of ash, whose thickness varied as shown in figure 64. Some ash 

fell on ships at sea and as far away as Scotland, and Finland. 

Thorarinsson (1954) carefully reconstructed the probable path 

of the eruptive cloud from reports of the ships and Finnish 

geologists, and from prevailing meteorological conditions; his map 

(fig. 65) shows that the cloud followed a curved path about 2,400 

miles long and travelled at an average speed of about 50 miles 

per hour, based on its arrival time at Finland. Across Finland 

the ash fall was quite thin and was restricted to a zone only about 

40 miles wide surprisingly narrow considering the length of the 

trip from Iceland.

The relative amounts of particles of different sizes in the ash 

deposit control the manner in which the mantle will absorb subsequent rainfall and are important factors in the rapidity of 

soil development and release of inorganic nutrients to plants. 

Studies have therefore been made of the size characteristics of 

the ash from a number of volcanoes, and the report of Thorarinsson (1954) on Hekla is one of the most informative. Thorarinsson 

made many determinations on the range in size of ash particles at 

various distances and directions from Hekla, and his results for 

stations at intervals downwind for 100 km from the volcano are 

summarized in figure 66. The maximum diameter of ash particles
430 INVESTIGATIONS OF ALASKAN VOLCANOES

FIGURE 64. Map of Hekla volcano in Iceland showing thickness of ash deposit from the eruption in March 1947 (after Thorarinsson, 1954).

at the vent is too large to be shown on this graph. It was about 

6 centimeters at a distance of 3 kilometers downwind, 1.5 centimeters at 30 kilometers and 0.2 centimeters at 70 kilometers. The 

median diameter decreases similarly. While the maximum and 

median diameters give an idea of the range in size, more meaningful information may be conveyed by plotting the size range of 

the middle 80 percent of the material. Thus, in figure 66, at 3 

kilometers from the volcano 80 percent of the material is between 

0.15 and 5.0 centimeters diameter, whereas at 30 kilometers, 80 

percent is between 0.05 and 0.50 centimeter diameter. It is shown 

here in this manner to emphasize that not only do the maximum, 

average and median sizes decrease at greater distances but that 

necessarily the size range of material must decrease also. The 

salient effect of the lower absolute size and smaller range of size 

of particles at greater distance is to decrease the permeability 

of the mantle to rainfall and hence to increase the possibility of 

excessive runoff and erosion out to the point where the thickness
SOME EFFECTS OF RECENT VOLCANIC ASH. FALLS 431

FIGURE 65. Map of route of airborne ash from the eruption of Hekla volcano in Iceland, across 

Scotland and Finland, on March 29-31, 1947 (after Thorarinsson, 1954).

I 2

30 40 50 60 70

DISTANCE FROM VOLCANO. IN KILOMETERS

FIGURE 66. Graph showing size range of ash fall in 1947 at increasing distances downwind from 

Hekla volcano in Iceland. At a particular distance 80 percent of the material is of sizes between the upper and lower solid curves (from data of Thorarinsson, 1954).
432 INVESTIGATIONS OF ALASKAN VOLCANOES

of the mantle becomes so small as to furnish little material to 

the runoff water.

VOLCAN QTTIZAPU

A brief, but catastrophic eruption of Volcan Quizapu in the 

Chilean Andes on April 10, 1932, projected a great quantity of 

ash to heights of about 45,000 feet to be carried eastward by 

strong winds and deposited in a belt across the whole width of 

South America. According to Bruggen (1932) and Vogel (1932), 

the strong explosions apparently began about noon on April 10, 

reaching a climax in the late afternoon. The eruption continued 

through the night and the next several days with decreasing intensity. Because of the heavy cover of ash and pumice in the source 

areas, it could not be determined subsequently whether there had 

been minor amounts of lava erupted also.

The large area of ash fall on land provided an exceptional opportunity for investigation of the pattern of ash distribution, 

and Larsson (1937) made a careful and detailed study of ash 

samples that had been collected along the path of the ash cloud 

and augmented it with the many published descriptions of the 

ash fall at various points. Larsson's map of the times of beginning 

of ash fall, reproduced in figure 67, indicates that the ash cloud

Site of reported start of ashfall

Location of analyzed samples 

Limit of observed ashfall 

0 500 1000 Km

 40°

FIGURE 67. Map of successive positions of ash front from the eruption of Volcan Quizapu in 

Chile, in April 1932 (after Larsson, 1937).
SOME EFFECTS OF RECENT VOLCANIC ASH FALLS 433

moved eastward at high speed but along a remarkably narrow 

front. Its arrival at Buenos Aires, Argentina, 700 miles to the 

east at 6:00 a.m. on April 11 implies an average speed of about 

40 miles per hour in this direction. From Buenos Aires the ash 

fall front swung around and moved more slowly northeastward 

along the Atlantic coast, reaching Rio de Janeiro, Brazil, a distance of 1,850 miles from the volcano, shortly after noon on 

April 15.

Because of the uniformity of wind directions in the levels 

through which the ash settled, the zone of appreciable ash fall is 

quite narrow, as shown by figure 68, Larsson's (1937) map of 

lines of equal thickness of ash deposit. The general decrease in 

thickness with increasing distance downwind from the volcano is 

interrupted by a subordinate maximum greater than 10 centimeters 

(4 inches) some 350 miles downwind. The zone within the line 

of 5 centimeters (2 inch) thickness, is only some 60 miles wide 

but stretches for 600 miles downwind, almost to Buenos Aires. 

North and south of this narrow zone the thickness of ash fall 

decreases rapidly so that the zone of ash fall that is thicker than 

0.1 centimeter (% 5 inch) is only about 400 miles wide, and of

70° 60' 50°

Limit of observed ashfall 

0 500 1000 Km

-40°

FIOURB 68. Map showing the thickness of ash deposits from the eruption of Volcan Quizapu 

Chile, in April 1932 (after Larsson. 1937).
434 INVESTIGATIONS OF ALASKAN VOLCANOES

fairly uniform width from the vicinity of the volcano to the 

far side of Buenos Aires.

The material erupted was andesitic or dacitic with about 64 

percent silica, 16 percent alumina, and 4 percent total iron oxides. 

The detailed data of Larsson's study made it possible for him to 

demonstrate that progressively greater differences existed between the bulk composition of the material as initially erupted 

and the material falling at greater distances from the volcano. 

Thus ash at 100 miles distance had 67^ percent silica, that at 

500 miles had 70*4 percent silica, and that at 700 miles had 

69% percent silica, a general increase of some 6 percent silica 

with concomitant changes in other oxides, compared with the 

erupted material near the vents. This change Larsson accounts 

for simply as a result of the early settling out of the heavy lowsilica mineral constituents, such as pyroxenes and calcic plagioclase, leaving the remaining ash enriched in silica, a characteristic 

of ash falls noted by several previous workers, among them 

Murray and Renard (1884). He further reasons that the material 

falling quite near the volcano should be enriched in these heavier 

mineral constituents giving a bulk composition lower in total 

silica than that of the material as initially erupted. Larsson 

lacked samples to confirm this relationship but it seems to be 

borne out in the 1919 eruption of Gunung Kelud in Indonesia.

GUNTTNG KELUD

Gunung Kelud, a volcano 5,678 feet above sea level in central 

Java, is an example of an explosive volcano, where the hazard of 

its eruption is increased greatly by the presence of a crater lake 

in its summit, for such a volcano may furnish not only quantities 

of airborne ash, but also destructive mudflows and floods. Ten 

thousand persons are said to have been killed in its eruption in 

1587 A.D., and 5,110 persons in its eruption of 1919.

The eruption in 1919 took place on the night of the 19th and 

20th of May. The crater lake, containing about 40 million cubic 

yards of water, was ejected along with somewhat more than this 

volume of volcanic debris and ash. In less than an hour 104 villages and many plantations were partly or completely destroyed 

(Mohr and Van Baren, 1954, p. 224).

The eruption of Gunung Kelud illustrates still another pattern 

of ash distribution brought about by a specific meteorological 

situation. The eruption took place during the season when winds 

below 20,000 feet were from the west while those above were from 

the east. The ash blown to high levels was carried westward at 

fairly high speed, and as it settled into the lower zone it was
SOME EFFECTS OF RECENT VOLCANIC ASH FALLS 435

J A V

0 C B A _

0 100 200 300 400 500 KilometerT

0 100 200 300 Miles

FIGURE 69. Map of Java, showing bilateral distribution of ash fall from the 1919 eruption of 

Gunung Kelud volcano. Dashed lines enclose areas of ashfall. (Mohr and Van Baren, 1954, 

fig. 38a, after Kemmerling, 1921).

carried eastward, but at slower speeds so that the bulk of it fell 

to the ground west of the volcano (fig. 69). That portion of the 

ash thrown to heights less than 20,000 feet was carried only 

eastward to form another lobe of the ash deposit that extended 

as far as Bali. The composition of ash fall material at various 

distances east and west from the volcano follows closely the pattern of ash fall eruption of Volcan Quizapu in Chile in 1932, 

(Larsson, 1937). Figure 70 has been constructed with data selected 

by Mohr and Van Baren (1954, p. 233) from Baak (1949, p. 38) 

and shows that the material that fell very near Gunung Kelud 

is somewhat less silicic than the bulk composition as erupted, 

though that which fell at great distances is more silicic.

PABfCUTIN

Prolonged eruptions are not common, and indeed it is uncommon for significant ash eruption to last more than a few weeks or 

months. Paricutin, the volcano that started at a point where no 

vent had been known previously, was an exception, and its 9 years

2 

i 55

DISTANCE. IN KILOMETERS

150

EAST

FIGURE 70. Graph showing variation in silica content of ash fall of Gunung Kelud in Java, in 

1919, with distance east and west of the volcano (from data listed by Mohr and Van Baren, 

1954, p. 283).
436 INVESTIGATIONS OF ALASKAN VOLCANOES

of continuous eruptive activity permitted investigation more extensive than usual. During these years there were 18 changes of 

seasonal wind directions in the waxing and waning ash column, 

so that the resultant distribution of ash became much more 

complicated than that of the more common brief eruptions. A 

detailed account of the first 3 years of activity, during which the 

major part of material was erupted, is given by Foshag and 

Gonzales (1956).

The preliminary seismic disturbances began several weeks before 

the outbreak and built to such a crescendo of intensity and frequency that the villages in the area were thoroughly aroused to 

impending disaster. The outbreak, when it came on the afternoon 

of February 20,1943, was not from any of the many cinder cones 

that dotted the countryside, but from a flat, cultivated area. At 

first only ash, bombs, and gases were thrown out of the newly 

opened fissure. Then, during the second night, a lava flow started, 

and from that time onward for 9 years there were few, if any, 

periods when lava was not being erupted, although there were 

periods, some of them weeks in length, during which eruption of 

ash remained small.

The first several weeks were marked by particularly strong ash 

eruptions. According to Fries (1953) some 83 million cubic meters 

(110 million cubic yards) of bombs, lapilli, and ash were erupted 

from February 20 to March 6, a rate of some 5,930,000 cubic 

meters per day. Thereafter the daily rate dropped consistently to 

the end of 1947 and remained well below 100,000 cubic meters 

per day until the latter part of 1951 when volume increased 

again, much like a dying gasp, before finally ceasing entirely on 

March 4,1952.

The measurements of ash thickness given by Segerstrom (1950) 

for the deposits in 1946 are approximately those at the end of the 

eruption, for the bulk of ash had been erupted before 1946 (fig. 

71). The ash mantle extends radially from the volcano with decreasing thickness, and because of the many changes of wind 

direction as well as vacillations in strength of the eruption, the 

deposit is made up of many discontinuous layers of ash and lapilli 

varying in grain size.

The winds of the dry season (winter and spring) in this region 

of Mexico are prevailingly from the west, and those of the wet 

season (summer and fall) from the east* accounting in large part 

for the east-west elongation of the distribution pattern. According to Segerstrom (1950) the area of ash deposit thicker than 

25 centimeters (10 inches) was 233 square kilometers (about 9,500
A X

FIGURE 71. Map of the vicinity of Paricutin in Mexico (from Segerstrom, 195

ash deposit in 1946 from the eruption of the volcano, the area covered by l

that was crop land before the beginning of the eruption in 1943.
438 INVESTIGATIONS OF ALASKAN VOLCANOES

acres), and this land was covered too deeply by ash to enable 

early reclamation, especially in the face of continued threat of 

more ash fall. Consequently this zone of bare ash-covered fields 

and dead forests remained desolate through the 9 years of the 

eruption.

METEOROLOGICAL FACTORS IN ALASKA

Important factors that affect the pattern of distribution of ash 

fall from a given explosive eruption include height of eruption, 

particle size and density, behavior of wind, and occurrence or 

nonoccurrence of rainfall. Knowing these factors and making 

several compromises in the interest of simplifying the problem, 

the area where ash fall will occur may be determined and even 

the relative amounts falling at different areas may be indicated 

roughly. Similar calculations have been made with varying degrees of precision to determine fall-out patterns in atomic bomb 

tests (Air Weather Service, 1952). But for most volcanic eruptions 

the calculations become impractical because the necessary data 

are not available at the moment of eruption, much less in advance, 

and because the height to which material is thrown varies widely 

during the course of the eruption. Little can be said of the characteristics of the particles except that a great range of size may 

be expected and a range of density, from very compact material 

to very frothy material. Wind directions and speeds are not only 

likely to be quite different at different levels through which the 

particles settle, but also may change as the eruption continues. 

About the only aspect of the problem that encourages exploration 

is that of the probability of ash fall in given areas on the basis of 

general behavior of winds.

The map montages of plates 55 to 58 have been compiled to 

show the wind directions and average speeds at different elevations and seasons from series of observations at four Alaskan 

stations. The location of each map area is given in plate 54. 

These montages permit a very rough estimate of the probabilities 

of ash being carried across a given area from the eruption of a 

given volcano. They imply nothing, of course, as to the probability 

of an eruption occurring.

The data on which plates 55 to 58 are based were obtained 

from daily soundings during the period May 1948 to April 1953, 

the total number of successful observations for most levels and 

seasons varying from 350 to 450. The observation was attempted 

at 0300 G.c.t. each day, and, if unsuccessful, a usable value was 

sometimes furnished by measuring wind direction and speed from 

the upper air chart for that particular observation time. The
SOME EFFECTS OF RECENT VOLCANIC ASH FALLS 439

data were averaged and tabulated by the U.S. Weather Bureau 

for the Aerological Branch of the U.S. Navy for the seasons of the 

year and for five isobaric levels corresponding approximately to 

elevations of 5, 10, 20, 30, and 40 thousand feet above sea level. 

The map montages were compiled by the writer from these tabulations, centering the wind roses for upper levels at representative 

volcanoes rather than at the station where the observations were 

made. Such shifting of wind roses by a hundred miles or so seems 

permissible, at least for the upper levels, because of the similarity 

of the wind rose patterns from station to station along the 1,200- 

mile arc from Anchorage to Adak Island. The 850 millibars 

(5,000 feet elevation) wind roses are not confidently applied except 

in the immediate vicinity of their station because of orographic 

effects.

In addition some information on wind behavior at levels above 

40,000 feet may be obtained from the mean monthly maps (for 

instance, Air Weather Service 1953). An "average" wind direction and speed can be scaled off the map of a particular month 

and level above the geographic point in question, and such determinations for four representative months are shown in the following table. A disadvantage of such a representation for the present 

purpose is that no idea can be obtained of the variability of the 

winds nor the percentage of time the wind direction is in each 

quadrant.

To illustrate the use and limitations of such a map montage an 

estimate of the probability of ash fall at Whittier, 140 miles to

Four-year-average directional tendency of upper-air wind

[Inferred from "Mean monthly maps of 300-, 200-, 100-, 50-. and 25-milIibar surfaces over North 

America." Air Weather Service, tech. rept. 105-107 April 1953, Washington, D. C.]

Place

Level (millibars)

25 

50 

100 

200 

300

25 

50 

100 

200 

300

25 

50 

100 

200 

300

Approximate 

elevation 

(feet)

70,000 

60,000 

50,000 

40,000 

30,000

70,000 

60,000 

50,000 

40,000 

30,000

70,000 

60,000 

50,000 

40,000 

30,000

Directional tendencies, in degrees clockwise 

from north, for indicated midseason months

January

65 

65 175 

160 

50

65 

65 165 

155 

50

95 

85 165 

160 

60

April

350 

10 120 

45 

45

115 

20 145 

55 

60

1105 

65 170 

85 

75

July

315 

320 

340 

325 135

320 

310 10 

0 150

(?) 

300 190 

80 170

October

55 

60 

55 

30 155

80 

80 

90 

55 160

85 

90 

95 

75 170

i Weak tendency.
440 INVESTIGATIONS OF ALASKAN VOLCANOES

the east, can be made from a hypothetical example of a winter 

eruption at Redoubt Volcano in which a brief explosion throws 

material to a maximum height of 45,000 feet. As a first approximation, the percentage of time that the wind at each level is 

directed from Redoubt Volcano toward Whittier may be listed, as 

in the following table, and the average made of the whole. This 

is 11.5 percent, a very crude indication that winds would be 

favorable about that percentage of the time to carry ash from 

Redoubt Volcano to, and beyond, Whittier. Although the winds 

in the upper levels have the greater velocities and, for precision, 

should probably be given more weight in the calculation, it alters 

the result in the normal case only slightly, certainly not enough 

to cause concern in view of the many other imponderable and 

uncertain factors.

Percent of time wind blew from Redoubt Volcano toward Whittier and Homer,

Alaska,

Level

(feet)

35,000 to 45,000. ......:...................

25,000 to 35,000. . .........................

15,000 to 25,000. ..........................

5,000 to 15,000. ..........................

Whittier

Winter

18 

12.5 

8.5 

7

11.5

Summer

12 

1.1 

8 

5

9

Homer

Winter

8 

10 

8

7

8.3

Summer

7 

5 

4 

3

3.8

It is well to remember, however, that the "average" situation 

dealt with here does not necessarily represent an actual situation 

at a particular time. The assumption in the foregoing discussion 

that the 18 times out of a hundred when winds at 40,000 feet are 

directed from Redoubt Volcano toward Whittier also includes the 

12, 8, and 7 times that the winds, at 30-, 20-, and 10-thousand 

feet respectively were in that direction, but winds seldom are 

in exactly the same direction at all levels. To fall at Whittier, 

ash starting its journey at 45,000 feet might start in a southeastern 

or northeastern direction and be carried by a somewhat circuitous route to Whittier by an appropriate combination of winds 

at lower levels.

Similar qualitative estimates of the situations for other volcanoes and localities in the area could be made from plate 55, or 

of still other situations illustrated in the map montages of the 

Kodiak Island, Dutch Harbor, and Adak Island areas (pis. 56-58).
SOME EFFECTS OF RECENT VOLCANIC ASH FALLS 441

In a general way, ash may be carried great distances by the 

stronger winds at higher levels, and the wind directions at these 

higher levels are more consistent than those at low levels. Thus 

for the Anchorage and Kodiak areas in the winter, spring, and 

summer, winds above 20,000 feet blow toward the eastern quadrant most of the time, but in the fall they blow into the northern 

and northeastern quadrants, and for the Dutch Harbor and Adak 

Island areas, the upper winds blow into the eastern quadrant most 

of the time in all seasons. Probably the distribution of ash from 

major explosive eruptions (hence in general the more damaging 

eruptions) can be predicted more confidently than that of the 

weak eruptions, because the ash of the major explosions will be 

projected to upper levels where wind directions are more consistent. 

Rainfall may have a great influence, not only in limiting the 

area of ash fall, but also in determining the action of the ash and 

its associated water-soluble chemicals on the vegetation and in 

the buildup of floods and mudflows (p. 449). The simple smooth 

distribution of ash fall downwind by gravitational settling can 

be greatly modified by a heavy rainstorm, bringing down in a 

small area most of the ash remaining in the erupitve plume and 

forming an abnormally thick accumulation there and an abnormally thin one farther downwind. Very favorable conditions for 

production of torrential rains are found in the immediate vicinity 

of the eruptive column (Finch, 1930) and under the "elbow" 

where the eruptive plume extends downwind from the vertical 

eruptive column. Moisture-laden low-level air has been dragged 

upward and mixed into the rapidly cooling gases of the eruptive 

column, which contains a certain amount of steam as well as 

abundant solid particles to act as condensation nuclei. Conditions likewise favorable for producing rain exist to a diminishing 

degree downwind in the extremely turbulent eruptive cloud.

EFFECTS OF ERUPTIONS

It would be quite impossible to anticipate all the effects, direct 

and indirect, that might result from volcanic eruptions in Alaska 

or to set them down in their proper relationship. But here to be 

considered are the range of effects on public health and safety, 

utilities, transportation, communication, and agriculture, based 

on the limited recorded experience in Alaskan eruptions and on 

several somewhat better documented eruptions in other parts of 

the world. Several points are worth noting at the outset: first, 

the major damage and human suffering from a volcanic eruption 

often may be due less to physical than to psychological factors,
442 INVESTIGATIONS OF ALASKAN VOLCANOES

such as panic and fear of the unknown, and usually such suffering 

is entirely unnecessary; second, eruptions are short-lived, and, 

although they produce physically uncomfortable or inconvenient 

situations, actual danger is usually quite absent at a reasonable 

distance from the vents; and third, explosive eruptions usually 

bring long-range benefits, such as improvement of soil and crop 

production as an after effect of ash fall.

PUBLIC HEALTH AND SAFETY

Of immediate concern to the individual are his own personal 

health, safety, and continued efficiency. Many people at once 

associate the ash from volcanic eruptions with noxious gases and 

poisonous chemicals, and the terms "sulfurous fumes" and "toxic 

gases" are used more often than warranted in descriptions of 

eruptions. It is true that the odors of certain acid gases are 

frequently detectable in areas of falling ash, but at a distance 

from the vent the concentrations are usually only temporary and 

no more than met with in an adequately ventilated chemical laboratory, in which atmosphere the chemist works year after year 

with no ill effects.

Some of the materials erupted as vapors, such as water, quickly 

condense in large part to liquids, while others such as carbon 

dioxide and sulfur dioxide may remain as gas for some time and 

gradually become diluted by mixing with the atmosphere. The 

odor characteristic of volcanic eruptions, frequently ascribed simply to "sulfur," may often be due to burned sulfur, that is, sulfur 

dioxide, less often sulfur trioxide, or to hydrogen sulfide, but it is 

rarely justifiable to presume that other gases are not present. In 

many cases where "sulfurous" fumes have been noted by sense of 

smell, it has been found by analyses that several other gases are 

in equal or greater quantities. These other frequently-present 

gases include hydrochloric acid, hydrofluoric acid, carbonic acid 

(carbon dioxide), and ammonia.

All these gases may be harmful if inhaled in sufficient concentration for a sufficient length of time. The accompanying list 

gives the maximum concentration of industrial gases considered 

permissible for workers in steady contact (Sax, 1951), but somewhat greater concentrations of some of the gases can be tolerated 

for short periods of time. Thus, while 10 parts per million of 

sulfur dioxide is regarded as the maximum allowable concentration for continuous exposure, as much as 50 to 100 parts per 

million can be tolerated for exposures of half an hour to one hour 

duration. Ammonia, although perhaps common at the vents of 

some volcanoes, may be expected to quickly form less harmful
SOME EFFECTS OF RECENT VOLCANIC ASH FALLS 443

compounds by reaction with one or more acid gases usually present in excess. Carbon dioxide is harmful only in very high concentrations, when it acts as a diluent of oxygen. Its density causes 

it sometimes to collect in low places where it may be a hazard, 

especially because of its lack of warning odor.

Most of the other common volcanic gases are acidic, and have 

similar injurious effects, that is, irritational injuries to the eyes 

(conjunctivitis) and to the respiratory system (lung or bronchial 

edema). It is not possible to prescribe complete protective measures for all volcanic situations, and a properly fitted industrial 

gas-mask with acid-type filter is best. In the common case where 

such special equipment is lacking, it has been found a practical 

expedient to breathe through a dampened folded cloth, and if the 

eyes smart, to wear airtight-type goggles. As the action of the 

damp cloth is to trap the acidic gas in the moisture of the cloth, 

it is advisable to renew the effectiveness of the cloth at intervals 

by rinsing.

Effects of industrial gases on humans

[Generalized from Sax, 1951]

Gas

Ammonia ................

Carbon dioxide ............ 

Carbon monoxide. .........

Chlorine .................. 

Fluorine. .................

Hydrofluoric acid ..........

Sulfur dioxide. ............

Initially 

detectable 

odor 

(ppm)

53.........

Odorless. . . .

3.5........

1. ........ .

1. .........

Maximum 

allowable 

continuous 

exposure 

(ppm)

100. .......

5,000. ..... 

100. .......

0.35.......

5..........

3..........

20.........

10.........

2..........

1. .........

Effects of overdose

edema. 

Coma, asphyxiation.

Conjunctivitis, lung edema.

tion, lung inflammation.

larynx.

edema.

and respiratory tract.

of lungs.

in individual susceptibility to respiratory effects) .

The sulfur-derivative gases deserve special attention because of 

the complexity of their relationships and the variety of effects 

under different conditions. In a strongly reducing environment
444 INVESTIGATIONS OF ALASKAN VOLCANOES

the sulfur derivative may come forth as hydrogen sulfide, recognized by its well-known odor of rotten eggs. In a strongly oxidizing environment, the sulfur derivative may be sulfur dioxide, 

recognizable as the odor of a flaring match. It happens not infrequently that the conditions are neither strongly oxidizing nor 

reducing, and the product then may be a mixture of both gases. 

In the air their conversion to the stable sulfur trioxide or sulf uric 

acid goes on only slowly, in spite of the readily available oxygen, 

and in the absence of a catalyst the two original gases may persist 

for many miles downwind, with the concentration of the muchblamed "sulfuric acid" actually remaining quite low. This is not 

to say that sulfuric acid is rare or unimportant in volcanic products, for it no doubt comes out ready-formed in many eruptions. 

Its potency as a respiratory irritant is certainly decreased in this 

situation, however, by its existence not as a gas but as aerosol 

droplets which tend to take on moisture from the air to further 

dilute themselves and grow to sizes more likely to be filtered out 

of the inhaled air.

The solid products of an explosive eruption, that is, the ash 

particles themselves, are largely composed of rock-forming silicate 

minerals and silicate glass. Small quantities of such material 

inhaled usually have no harmful effect. The filtering mechanism 

in the human nose and upper air passages is remarkably efficient, 

and only a very small proportion of particles of ash-laden atmosphere entering these passages actually reaches the lungs. The 

length of exposure to such ash-laden air is relatively short usually 

not more than a few hours or days and quite ineffective in 

comparison to the months and years of daily exposure required in 

certain dusty occupations to develop the condition known as 

silicosis or pneumonoconiosis. Nevertheless during an ash fall 

from a volcanic eruption, it is usually easy and convenient to hold 

a damp folded handkerchief over the face, or, if both hands must 

be free, wear a dust mask, either ready-made or improvised. 

These can give nearly complete prefiltering action against dust 

and also give the wearer added comfort by relieving the nasal 

passages of a large part of the filtering work.

The health hazard of breathing ash, while never great if simple 

precautions are observed, should be guarded against, particularly 

among those whose occupations may expose them to airborne ash 

for protracted periods. Long intermittent exposure to low-level 

concentrations of finely divided ash could possibly have more 

harmful and insidious effect on the individual than the brief 

exposure to very high concentrations that may have occurred
SOME EFFECTS OF RECENT VOLCANIC ASH FALLS 445

during the ash fall proper. For weeks or months after an eruption there may be brief flurries of ash caught up by winds, and 

these are of no harm nor great inconvenience to persons in most 

occupations. However, those persons continually exposed, such 

as in the clearing of the ash from traffic arteries, should wear dust 

masks.

Many of the public and private water supplies of Alaska are 

from streams and reservoirs exposed to ash fall in the event of a 

nearby volcanic eruption. While an ash fall will not necessarily 

spoil a stream or reservoir supply, such supplies need close attention during and after the eruption to confirm potability of their 

water. In extreme cases, also, the actual storage capacity of a 

reservoir may be greatly reduced by ash brought in with runoff 

water.

During an eruption the ash particles commonly act as nuclei 

for the condensation of water, which dissolves a certain amount 

of acidic and other gaseous coproducts of the eruption. The water 

may persist as raindrops or as thin films until it reaches the 

ground, or it may evaporate, leaving an acid residue on the particle. The acid constituents in solution in the drop or film react 

slowly with the ash particle, and in time the solution will return 

to a nearly neutral condition. Should a large amount of such ash 

fall into a stream, lake or reservoir before reaction is complete, 

the initial effects will be increased turbidity and acidity of the 

water. Within a few hours after cessation of the ash fall, however, the water may again become neutral or slightly alkaline, 

owing to reaction of the acid with the ash or other suspended 

material. The final condition will be a somewhat greater content 

of dissolved solids.

An instructive example of effect on water supply is furnished 

by the ash fall in Anchorage from the eruption of Mount Spurr 

on July 9,1953. Between one-fourth and one-eighth inch of fine ash 

was deposited in the environs of Anchorage in a period of about 

6 hours. Early tests of water samples from a reservoir showed 

pH values near 4.5 (moderately acidic); yet a few hours later 

when the ash fall had abated, the pH was again back to its normal 

value of slightly over 7. In the laboratory, measured amounts of 

dry ash placed in distilled water likewise produced only temporary 

increase in acidity. Thus, an acidic water that may have entered 

the public distribution system must have been neutralized long 

before reaching the consumer.

Turbidity of the intake water at the Fort Richardson treatment 

plant is normally less than 5 parts per million. On July 9, the day
446 INVESTIGATIONS OF ALASKAN VOLCANOES

of the ash fall, it rose sharply to 290 parts per million and then 

decreased to below 5 again by July 15 (Whetstone, 1955). At the 

times of the rains mentioned below the turbidity again rose to low 

maxima of 10, 12, 36, and 70 parts per million. It was necessary 

to add much more of the chlorinating agent than normal at the 

Anchorage treatment plant to maintain the required level of 

chlorination during the initial period of high turbidity and presumably the extra chlorinating agent was consumed by reaction with 

the suspended ash.

An investigation of the effects of the ash fall on the chemical 

character of water from Ship Creek and other water sources in 

the Anchorage area was made by Whetstone (1955). During a 

normal period, such as July 1949, the average sulfate concentration 

stayed close to 16 parts per million, decreasing, as did the content 

of total dissolved solids, during periods of high discharge of the 

streams. Immediately after the ash fall of July 9,1953, the sulfate 

content was 28 parts per million, considerably higher than would 

be expected at this time of year. For a few days thereafter the 

sulfate content ranged between 27 and 29 parts per million, then 

increased to 36 parts per million on July 17-19, coincident with 

the first rainfall since the eruption and accompanying increase in 

stream discharge. The sulfate concentration then decreased gradually to 23 parts per million by the end of July. Subsequently 

maxima of 28, 35, and 38 parts per million occurred immediately 

after rains of August 1-2, 5-10, and 21-28 respectively. Less 

complete sampling of other creeks in the area indicated similar 

concentrations.

It is quite apparent from these results that soluble sulfate 

brought down with the ash particles caused the abnormally high 

concentrations in the surface runoff. This occurred not only at 

the time of the ash fall but also at times of subsequent rainfall 

and high stream discharge. Although the amounts of sulfate 

involved in this case are far below that considered harmful to 

drinking water, harmful or disagreeable amounts of soluble constituents, such as sulfates, chlorides, fluorides, borates, or combination of these, might be furnished by other eruptions. It would 

seem advisable therefore to determine the potability of a threatened 

water supply by repeated tests during and for a reasonable period 

following an ash fall.

Attention is directed also to similar effects on smaller water 

supplies, such as reservoirs, tanks, open wells, and springs serving 

only small groups of people or those on farms. With small or 

moderate amounts of ash falling into a well, the undesirable
SOME EFFECTS OF RECENT VOLCANIC ASH FALLS 447

effects of turbidity and dissolved solids may be cleared up simply 

by prolonged pumping to bring in normal water from the aquifer. 

In other cases, such as during the eruption of Paricutin volcano 

in Mexico, springs and small gathering areas may silt up so badly 

that removal of ash becomes necessary. According to Segerstrom 

(1950, p. 25), the ash fall from Paricutin affected such local 

water supplies in a variety of direct and indirect ways.

BUILDINGS

In some volcanic areas, during eruptions there is an immediate 

danger of roof collapse due to heavy loads of ash. This danger is 

especially frequent in tropical countries where the construction 

of roofs for dwellings and other buildings is typically somewhat 

flimsy, providing only for protection from sun and rain. Least 

trouble of this kind is experienced with steep-pitched roofs, which 

permit the load of ash to slide off before an excessive amount 

collects. For instance, ash fall material did not accumulate on the 

steep shingled roofs of the Tarascan Indian homes in the neighborhood of Paricutin volcano, Mexico, in 1943 and 1944, whereas 

much not only collected on the low tile roofs of the Spanish style 

buildings but was difficult to remove because of their fragile 

construction. It is interesting to note that the distinctive steeproofed Tarascan architectural style is found in a region that 

probably was subjected to relatively frequent ash falls during the 

last few thousand years and that the steepness of roofs may thus 

be more than a coincidence.

Roofs of Alaskan houses and many public buildings possess high 

bearing strength and are purposely steep as a measure of protection against overload by snow. Although almost a foot of ash 

fell at the village of Kodiak during the 1912 eruption of Mount 

Katmai, Griggs' account makes little mention of roof collapse due 

to overloading except for one photo of a low-angle shed roof on a 

barn on Long Island, just off the village of Kodiak (Griggs, 1922, 

p. 16). While the possibility of roof collapse due to excessive 

loads of volcanic ash thus may not be acute during an Alaskan 

eruption, nevertheless it should not be disregarded, and attention 

should be given especially to those roofs of weak construction or 

low pitch. The point of failure of a roof will be approached with 

a much thinner deposit of ash than of snow because of the greater 

density of volcanic ash, and the point of failure will be even more 

quickly approached with wet ash.

UTILITIES, TRANSPORTATION, AND COMMUNICATION

The community electric power is affected by both the potential
448 INVESTIGATIONS OF ALASKAN VOLCANOES

of the generating plant and by the changing load or demand. 

Both factors operated to disadvantage during the ash fall at 

Anchorage on July 9, 1953, from the eruption of Mount Spurr. 

At the time one generator was already shut down for normal 

summer overhaul, when the peak power demand usually is lowest, 

and thus the available standby power was below normal. The 

darkness preceding and accompanying the ash fall caused the 

city street-lighting system to come on automatically at 11 o'clock 

in the morning, and with the lights of residences and office buildings being turned on also, an unanticipated peak load resulted. 

The crisis was passed without serious breakdown by means of 

prompt radio appeals to consumers to economize on the use of 

power.

At the same time, Anchorage telephone facilities were greatly 

strained because of the rush of phone calls between neighbors, 

friends, and relatives wishing to compare notes on the extent and 

meaning of the unprecedented fall of ash. Again radio appeals 

to the subscribers were successful in reducing the load and prevention of choking of the system. It is fairly obvious that for a 

community of this size one of the most effective means of communicating with the populace during an emergency is by way of 

the operating radio stations.

Transportation at first may be made difficult, chiefly owing to 

decreased visibility, but seldom because of deterioration of engines during the short period of ash fall. The ash, if dry, may 

form a haze, nearly opaque for all practical purposes to headlights of surface traffic. To this are added difficulties due to ash 

coatings on windshields and headlights and scratching of windshields, if windshield wipers are used incautiously. Even if the 

rate of ash fall is not great, much fine ash may be churned into 

the air by traffic and by winds, giving greatly decreased visibility. 

The damp ash or mud rain, which commonly falls, adheres even 

more persistently than dry ash to windshields and headlights, 

and the driver may or may not find improvement by leaning 

outside, where he must face the same barrage as the windshield. 

Traction becomes a problem with greater depths of ash on streets 

and highways, and it may become necessary to begin large-scale 

ash-removal operations at once.

Air traffic may become completely impracticable during the 

ash fall because of the decreased visibility. In a heavy ash fall 

the ceiling is zero for all practical purposes, and the attrition 

effects of the ash particles may cause damage to the plane and 

engine if exposure is more than momentary. Operation of plane
SOME EFFECTS OF RECENT VOLCANIC ASH FALLS 449

traffic during light ash fall does not seem to have serious 

consequences.

For some time after eruption and fall of ash has declined, the 

danger of floods, mudflows, and even landslides may continue; 

they constitute the main threats to continuous operation of public 

utilities, transportation, and communication. Additional hazards 

may exist to a minor degree owing to wind-raised dust clouds 

in and around the desolated region.

Although it might appear at first that ground covered with the 

porous and fluffy ash mantle should readily absorb large quantities of rainfall and thus hold back runoff, generally it can hold 

back only a fraction of what would have been retained were the 

ground still covered with normal vegetation (Lowdermilk, 1947). 

The rainwater quickly saturates the interstitial space of the ash, 

then begins to run off its surface and erode the already saturated 

ash and the soil beneath. The very fineness of particle size of the 

ash at the surface the portion that settled out most slowly decreases the permeability and is a major factor in increasing runoff and erosion. Only slight oversaturation of slope ash is needed 

to increase the bulk volume and lubricate the mass movement of 

water-saturated ash, so that the situation is ideal for triggering 

floods and mudflows, which in so many cases have followed volcanic eruptions and caused more loss of life and property than the 

eruptions themselves.

The probability of floods and mudflows, besides being dependent 

on the quantity of loose ash deposited, is dependent on the weather, 

and heavy rains during or following heavy ash fall will practically guarantee the occurrence of destructive floods and mudflows. This probability must be assessed by the civil authorities 

with the aid of meteorologists, and provision should be made for 

evacuation of citizens from vulnerable areas. Too often there is 

no period of grace, for, once started, the flood and mudflow fronts 

move with astonishing rapidity, and to be safe, personnel must be 

out before the flow starts. Ash avalanches and landslides, while 

an extension of the features of mudflows, are likely to be of importance only in areas very deeply covered by new ash, that is, in 

zones quite near the volcano.

The effect of floods and mudflows on transportation can be sudden and calamitous. Floods of volcanic derivation often carry 

much greater suspended loads than ordinary floods, and because 

of this, carry the threat not only of destruction of bridges and 

washouts of subgrades in some areas but likewise of "fill-ins" along 

other portions of the flood course. The latter can be in the form
450 INVESTIGATIONS OF ALASKAN VOLCANOES

of burial of stretches of highway or railroad tracks or choking of 

established water courses. Following the intense early ash eruptions of Paricutin in Mexico, for instance, the first heavy rains of 

the wet season sent great debris-laden floods down valley to choke 

the intricate system of irrigation ditches with ash (Lowdermilk, 

1947).

Machinery in power-generating plants, often located not far 

above normal stream level, can be especially vulnerable to volcanic flood waters. Besides the hazard of submersion, there is 

the added danger of abrasion of moving parts of turbines by the 

ash-laden water. Power lines as well as communication lines are 

vulnerable to breakage by floods, mudflows, and avalanches.

To forestall as much as possible the damage of floods and allied 

catastrophies, the work of clearing the ash from main arteries of 

travel should be started as soon as possible after the climax of 

eruption. In the city, attention should also be given to prevention 

of clogging of storm sewers and other vulnerable installations. 

Several types of ash-removal machinery may be pressed into 

service, and the most effective type will depend on the depth of 

ash to be removed and the degree of completeness of removal. 

The 1953 ash fall in the Anchorage area, for instance, was effectively removed by two makeshift devices: at the airports, jet engines were used to blow ash from runways, and in the city streets, 

graders with thick rubber lips attached to their blades were able 

to scrape all but a small residue of ash from the streets.

AGRICULTURE AND RELATED ACTIVITIES

Perhaps the most lasting effects of volcanic eruptions from the 

viewpoint of humans are found in agriculture. Lava flows destroy 

land for agricultural purposes, usually for many generations, unless covered in turn by volcanic ash or water-deposited sediments. 

Ash falls may destroy the crop at hand and impose severe handicaps to livestock grazing and to obtaining normal crops for several 

seasons. As the ash becomes mixed into the old soil, however, it 

may contribute benefits that are felt for many seasons or generations. The details of the after effects of eruptions on soils and 

crops are not yet well understood, and there is need for investigation of ways to ameliorate the harmful effects and ways to make 

the beneficial effects of the ash available soon after an eruption. 

The agricultural effects of volcanic eruptions may be classed as 

the immediate effects and the long-range effects. The immediate 

effects are in the main spectacular and destructive, while those 

felt over a longer period (several years or generations) include 

many that are beneficial. The lack of fundamental information on
SOME EFFECTS OF RECENT VOLCANIC ASH FALLS 451

which more definite conclusions could be based is due in large part 

to the fact that the opportunities for clear-cut investigation presented by actual eruptions are scattered, both geographically and 

in time, and that only in a very few instances have studies, started 

with the eruption, been carried through systematically to an 

ultimate fruition.

IMMEDIATE EFFECTS OF ASH FALL

Plants are relatively vulnerable to damage by volcanic eruptions, and there is a wide range of susceptibility among plants of 

different types. The mechanical overloading of ash on broadleaf 

trees and plants is common, leading to breaking of limbs and 

stems and to many casualties. Needle-leaf trees such as pines, 

while less vulnerable to overloading, appear to be quite susceptible 

to damage by such common volcanic gases as sulfur dioxide damage that may not show up for several days or weeks after exposure. 

Fruit blooms exposed to volcanic gases and ash may be killed 

outright or may survive to produce malformed or blighted fruit.

A sufficient depth of ash smothers pasture grass and low foliage. 

If only an inch or thereabouts of ash is deposited, subsequent 

rainfall probably will wash out enough for the grass and other 

plants to continue growth the same season, provided chemical 

damage to the leaves has not been too great. If the deposit is 

much deeper, new growth may break through the ash mantle or 

reappear when the ash mantle is removed by erosion. A depth of 

ash-fall deposit of several inches is sufficient to smother many 

types of grasses, and if somewhat thicker it is enough to weigh 

down and smother low bushy growth. For higher bushes and 

trees the main damage may be from breakage of branches. 

With orchard trees and other trees of special value, damage from 

this source may be prevented in large part by frequent shaking of 

foliage during the ash fall.

During the eruption there are marked meteorological effects 

near the vent. Low-level air laden with moisture is dragged upward to mingle with moisture- and dust-laden air of the eruptive 

cloud (Finch, 1930), with the result that strong downpours, 

variously loaded with ash and dissolved chemicals, are common 

in the vicinity of the vent and immediately downwind. The 

eruptive plume that is, the horizontal train of eruptive gas and 

ash moving downwind is extremely turbulent and has the required conditions not only for rainstorms but also for destructive 

hailstorms, which have been noted on occasion in zones under the 

eruptive plume. The heavy rainstorms on ash-covered terrain 

may result in excessive runoff and disastrous floods (p. 449).
452 INVESTIGATIONS OF ALASKAN VOLCANOES

While very little quantitative information is available on damage of vegetation by volcanic gases, a relatively large amount is 

available about damage by various industrial gases, some that 

find their counterparts in the fumes emitted from volcanoes. The 

data in this field have been summarized by Thomas (1951) and 

are listed in a somewhat generalized form in the following table 

for those gases common to both industrial and volcanic activity. 

It may be noted that the "threshold concentration" given here is 

roughly similar but not exactly analogous to the "maximum allowable concentration" listed for human experience on page 443. It is 

necessary also to emphasize that the threshold value may vary 

greatly, not only from one type of plant to another, but also 

that the susceptibility of a given plant may increase drastically, 

for instance, during periods of higher humidity and more active 

growth. An additional factor of possible importance in the problem of volcanic damage is the effect of combinations of one or 

more of the harmful gases, a situation that apparently also exists 

in the smog of modern cities and is claiming the attention of many 

investigators.

Effects of gases on plants

[Generalized from Thomas 1951]

Gas

Ammonia. ...........

Carbon dioxide. ..............

Carbon monoxide. ............

Fluorine.... .................

Hydrochloric acid ............

Hydrofluoric acid. ............

Threshold 

concentration 

(ppm)

10...........

500.......... 

1............

0.1.. ........

10...........

50...........

1. ...........

Effect of overdose

drying.

Epinasty, chlorosis, shedding of leaves.

Acute: Collapse of marginal and intercoastal 

areas, drying to ivory or brownish red.

size of aerosol droplets.

t-; 

V

The complexity of the problem of natural volcanic gases increases by the common involvement of aerosol mists and larger 

droplets composed of water solutions of one or more of the harmful compounds. Thus, while an aerosol of pure sulfuric acid 

liquid may not be particularly harmful, one of a water solution
SOME EFFECTS OF RECENT VOLCANIC ASH FALLS 453

of sulf uric acid of medium strength may have a strong scorching 

effect. Many of the "charred forests" and "burnt" vegetation of 

past volcanic eruptions, attributed to red hot ash falls or to hightemperature blasts, must rather be suspected of having been 

produced at low temperatures simply by the oxidizing action of 

sulfuric acid associated with the ash fall, or by the action of 

strong doses of sulfur dioxide gas, the effect of which may not be 

distinguishable from that of sulfuric acid by untrained observers. 

The action of soluble acid gases, such as hydrochloric and hydrofluoric acids may likewise be expected to vary greatly in water 

solution aerosols, and not necessarily to show a maximum effect 

in concentrated solution nor a constant decrease of effect upon 

dilution.

The wide range of possible concentrations leading to differing 

chemical and pathological activity of these substances can be 

appreciated by considering the variety of meteorological situations 

in which they might be involved. Aerosol droplets of sulfuric 

acid, for instance, passing through an atmosphere of high relative 

humidity would be quickly diluted owing to the strong affinity of 

sulfuric acid for water. Other acids in gaseous form might form 

aerosols under similar circumstances, and rain drops falling 

through or forming in an eruptive fume cloud dissolve some of 

the available nonatmospheric gases or aerosols. Duration of exposure is an important factor, and if the toxic droplets are removed quickly from the plants (rinsed off for instance by a 

nontoxic rain), there may be no harmful effect.

The gaseous and liquid constituents also exist as absorbed films 

on ash particles in the eruptive cloud and are brought down with 

the ash fall or mud rains. The harm they do to vegetation is 

probably largely conditioned by different meteorological situations, as discussed above. Finely divided ash, especially the glassy 

portion, may slowly react with the acid solution of the adsorbed 

film and, if contact is of sufficient duration, the acid may be 

neutralized before it begins reacting with the vegetation, or shortly 

thereafter, thus reducing the direct toxic effect.

Near Mount Katmai, the destruction of plants by the 1912 

eruption was extreme. Griggs (1915) went ashore in 1913 at 

Russian Anchorage, about 25 miles east-southeast of Mount 

Katmai volcano, and found extensive devastation by the 3-foot 

mantle of ash, but also many indications that the process of 

recovery had already begun. Whereas the vegetation of the preceding season had been reported as completely wiped out, Griggs 

found that the alders on slopes facing away from the volcano
454 INVESTIGATIONS OF ALASKAN VOLCANOES

were green and luxuriant. Those on the slopes facing toward the 

volcano had shriveled buds and were without leaves, although 

their woody parts were still pliable and new shoots were being 

sent up from the roots. From the description it appears that 

gases or fumes, rather than the high-temperature blasts suggested 

elsewhere, could have defoliated the alders. Smaller plants on 

the fairly level areas had been buried completely, yet where ash 

had been removed, vegetation seemed to be starting again 

vigorously.

At Kodiak, 100 miles east-southeast of Katmai volcano, the 

10-inch ash fall destroyed all low-growing vegetation. The damage to such plants, according to Griggs (1915), was not by any 

poisoning effect but simply by the smothering action of the ash 

blanket. Trees were weighted down by the ash, but on the 

conifers the effect was possibly little worse than from the periodic 

loads of winter snow. Griggs found no evidence of chemical 

blight on the coniferous trees. Materials of landslides and mudflows, together with material washed off slopes by running water, 

were deposited at the base of slopes to fill in ponds and swamps 

and bury their vegetation.

In the 1943-52 eruption of Paricutin in Mexico, agriculture in 

the immediate neighborhood came to a virtual halt, and effects of 

the eruption were felt many miles down the main valley where 

ash-laden floods covered fields, clogged the irrigation ditches of 

the rich sugarcane lands of the Los Reyes flood plain, and washed 

out the several power dams of the valley. Close to the volcano, 

foliage and blooms of fruit trees were destroyed, and at distances 

of several tens of miles sporadic ash falls caused damage to fruit 

blooms. Widespread loss of cane harvests at Los Reyes during 

1944 and early 1945 was the result of a plague of cane borers, 

who thrived apparently because of the extermination of a natural 

insect enemy of the borer during the ash fall. Yet in the same 

area the productivity of mangos and guavas increased after the 

onset of the eruption, reportedly because of the eradication of 

a destructive fruit fly by the ash fall (Segerstrom, 1950, p. 22). 

Also the ash fall may have killed certain insects that otherwise 

would have fertilized blooms and thus may have interrupted the 

reproductive cycle of some plants.

As long as the eruption continued there seemed little to be 

done to ameliorate the situation in regard to cultivated crops near 

Paricutin. If such plantings as were attempted in the ash were 

able to survive subsequent ash falls, washouts, or burials by runoff 

sediment, they withered and died before maturing. Consequently
SOME EFFECTS OF RECENT VOLCANIC ASH FALLS 455

there was much discouragement, and the few who obtained harvests were able to do so only by great effort, such as planting corn 

in individual holes in the ash where the roots could reach the 

old soil. It should be emphasized here, however, that Paricutin's 

continuation of activity through several growing seasons is exceptional behavior for volcanoes and that agricultural destruction 

by most volcanic eruptions takes place mainly in a brief period, 

after which rehabilitation and return to normal can proceed with 

only moderate chance of interruption by further eruptive activity.

The logging industry may suffer owing to widespread killing 

of forests by ash fall, to distorted growth of trees following nonfatal damage, or to insect infestations brought about with the 

ecological imbalance. At Paricutin prior to the 1943 eruption, 

pine forests had been the source of lumber, fuel, and turpentine 

(Segerstrom, 1950, p. 23). Most trees within the 1-meter line of 

ash thickness were killed, while most outside the half-meter thickness survived. Many men of the nearby villages, no longer able 

to plant crops, turned to wood cutting for a living, with the 

result that not only were damaged trees logged off, but also many 

more of the undamaged trees than was good for the region as a 

whole. The turpentine industry had to be given up for the duration of the eruption because of the intermittant contamination 

of the pine sap by ash falling into the collecting cups.

The effect of ash fall on livestock is frequently quite serious, 

and the present writer has found no complete explanation of the 

mechanism of the effect, except where starvation has been caused 

by burial of pastures. In situations where the cattle are able to 

graze on ash-laden pasturage, they have frequently been seen to 

sicken and die in a very bloated condition, and this has been 

presumed, without much trained investigation, to be due mainly 

to indiscriminate consumption of ash along with the grass, perhaps resulting in ultimate overloading of the digestive system 

with mechanically irritating rock material or with poisons such as 

fluorides or ammonium chloride. At Kodiak in 1912 so much 

concern was felt for the herd of Galloway cattle at the Agricultural Experiment Station that it was shipped to the States and 

only returned two years after the eruption when pastures had 

revived. Other cattle were supported by imported ensilage 

(Griggs, 1922, p. 44). At Paricutin about 4,500 cattle, 550 horses, 

and dozens of sheep and goats died from the effects of the ash falls 

during the early weeks of the eruption in 1943 (Segerstrom, 1950, 

p. 23), and many more were saved only by removing them in 

time to unaffected areas. A study of the effects of ash fall on
456 INVESTIGATIONS OF ALASKAN VOLCANOES

livestock is anticipated as a part of the series on the 1947-48 

eruption of Hekla in Iceland (Thorarinsson, 1954) and promises 

to be of value.

Damage to fishing grounds and to marine life in general appear 

to be very temporary, judging from the scanty information found 

in the literature. Little directed study seems to have been made 

of the problems, probably because of the erratic occurrence of 

eruptions and the difficulties introduced by lack of controlled 

conditions. However, it is not possible to say that important and 

long lasting effects do not result from some eruptions.

The effect of the eruption of Mount Katmai on marine vegetation was discussed briefly by Rigg (1914), who had examined the 

near-shore vegetation along the south coast during the summer of 

1913. He found that larger plants, such as kelp, that had been 

reported as dead soon after the eruption, were once again growing 

in the littoral zone, and he concluded that damage had been 

apparently from four causes:

(1) the grinding effect of floating pumice;

(2) actual burial of plants by the deposit of ash;

(3) burial by ash of rocks which had furnished anchorage for marine algae;

(4) the effect of poisonous gases on plants growing in the littoral zone or 

whose distal portions are kept at the surface of the water by floats.

Rigg further concluded that the damage was temporary and that 

the kelp beds, which serve so well as a warning of shallow rocky 

bottoms to navigators, as well as a source of potash fertilizer for 

the vegetable gardens of the natives, should regain most of their 

original distribution shortly. He did not discuss the effects of 

the ash fall on the food supplies of the near-shore or off-shore 

fauna or possible direct effects on the fauna.

In discussing the 1947 eruption of Hekla in Iceland, Thorarinsson (1954, p. 62) remarked on the reports of complete disappearance of cod from the fishing area between the islands of 

Vestmannaeyjar and the south coast of Iceland (map, fig. 4) for 

two days following the outbreak and ash fall. Fishing boats operating still farther south and outside the zone of ash fall reported an apparent increase of cod in the deeper water, as if they 

had temporarily fled the area of ash fall. No further information 

was furnished.

LONG-RANGE EFFECTS OF ASH FALL.

Moderate ash falls usually are ultimately beneficial to agriculture, especially if the area affected escapes excessive erosion, for 

most soils are improved, both chemically and physically, by admixture of fresh rock material. This is strikingly shown in many 

tropical and subtropical areas of concentrated agricultural de-
SOME EFFECTS OF RECENT VOLCANIC ASH FALLS 457

velopment, as remarked upon by van Bemmelen (1949, p. 224) 

for Indonesia, by Rigotard (1934) for areas of recent volcanic 

activity in Italy, and by others. Application of volcanic ash to 

soils as a slow-acting fertilizer has been cogently suggested by 

Keller (1948). In regions of low temperatures and low rainfall 

the beneficial effects of volcanic ash falls are not felt as soon 

perhaps, but nevertheless have been amply demonstrated, as 

noted, for instance, by Griggs (1922) in describing the remarkable recovery of vegetation at Kodiak Island following the eruption 

of Mount Katmai. Leon and Polle (1956) found that only potash 

was available in adequate amounts in the 1955 ash fall of Volcan 

Nilahue in southern Chile. Whereas the phosphorous-fixing capacity of this ash was low, that of somewhat older ash soil was 

already appreciably developed.

The physical characteristics of fresh volcanic ash differ markedly in some respects from those of the usual soil, particularly 

in its granularity, sharp angularity of particles, general paucity 

of ultrafine particles, and extreme lack of cohesion under some 

conditions, yet too great cohesion under other conditions. If the 

fresh ash deposit is greater than plow depth, these physical 

characteristics lead to distinct behaviors when its use as a soil 

is attempted, for they affect not only workability, permeability, 

and erodability, but also ability to function as a nutrient medium 

for the soil flora and fauna.

The bulk chemical composition of raw volcanic ash may be 

similar to that of a normal soil, except for abnormally low content 

of chemically combined water and organic material. Silica content of most volcanic ash lies between 45 percent and 75 percent. 

The following table shows, for example, that the ash of the Mount 

Spurr eruption of 1953 had a fairly low silica content, about 55 

percent, whereas that of the Mount Katmai eruption of 1912 

ranged from 57 to 76 percent, an extraordinarily wide range for 

ash of a single eruption. An ash mantle several inches thick 

would contain large absolute amounts per acre of such mineral 

nutrients as potash, lime, and phosphorus, even though the percentages of these constituents in the ash is low. However, the 

total bulk analysis does not give the very important information 

on how much of the mineral nutrients are available to the plants.

Whether the ash will be suitable as a supporting "soil" is determined by its response to the demands of the plants. A variety 

of chemical tests have been devised to measure the approximate 

amounts of plant nutrients that may be expected to become available from a normal soil during the growing season. These tests
458 INVESTIGATIONS OF ALASKAN VOLCANOES

Bulk chemical compositions, in percent, of some Alaskan volcanic products

SiOa. ....................

AlaOa....................

FezOa....................

FeO.....................

MgO....................

CaO.....................

Na2O....................

KaO.....................

HaO + ...................

HaO-.... ...............

TiOa.....................

COz............... .......

PaOs.......... ...........

MnO ....................

S................ ........

Cl....... ................

80s.....................

BaO. ....................

Total ..............

1

t;^ 9

17 9

3.1

4.2

3.7

7.4

3.4

1.0

.24

.93

.74

.30

.16

.60

1.5

100

2

"17 QQ

17.39

2.76

4.75

3.42

7.49

4.03

1.06

.36

.07

.81

.22

.15

.07

.07

.05

100.69

3

68.00

14.58

1.66

2.75

1.65

4.07

3.92

1.98

.13

.42

.53

.14

.07

.02

.13

.05

100.10

4

76.53

12.31

.46

.96

.00

1.01

4.15

3.05

.25

.87

.17

.05

.04

.01

.23

.07

100.16

1. Ash, Mount Spurr, eruption of July 9, 1953, collected at Anchorage, Alaska. Analysts: 

F. S. Borris, Katrine White, and H. F. Phillips, U.S. Geol. Survey.

2. Ash, Mount Katmai, eruption of 1912, layer in a series. Analyst: C. N. Fenner (1950, p. 

616).

3. Same at 2.

4. Same as 2.

commonly involve a rapid leaching of a measured soil sample with 

a given amount of weak acid solution, such as hydrochloric or 

citric acid and comparing the results with those obtained from 

leaching a similar soil, whose nutrient content was shown to be 

adequate by actual plant growth tests. Unfortunately few controlled 

plant growth experiments have been made on fresh volcanic ash, 

and, because ash is so different in many respects from normal soil, 

certain reservations must be held on the use of arbitrary chemical tests that have been calibrated only against plant-growth experiments on normal soil.

Such chemical tests are to some extent indicative nevertheless, 

and the results of tests on the 1953 Mount Spurr ash are given below. Although calcium is "high" in these tests, nitrogen (both as 

nitrate and as ammonia) and phosphorus are unavailable, 

and potash is "low." This ash in itself would therefore seem

Results of soil tests on ash sample from the Mount Spurr eruption in 1953, 

collected at Anchorage, Alaska.

[Tests made July 10, 1953, by Paul Martin, Alaska Agr. Expt Sta., Palmer, Alaska, using Morgan soil-testing system, (Lunt, Swanson and Jacobson, 1950). pH = 6.8 (paste of 1 part 

ash to 1 part distilled water) ]

N08 None 

P205 .None 

K20 . Low 

CaO. ._____ _ _ High

MgO--.-....-.- Trace

Fe Medium

Al. Medium

Mn._...... Trace

NH4 ..... -None

Cu .................. Low

SO* . Medium 

Cl . .Trace 

Si High 

C08 None

B - - Trace

Mo... None

Zn ... _ Trace 

Hg .... .Trace

Pb ...... ...None

As None
SOME EFFECTS OF RECENT VOLCANIC ASH FALLS 459

to be a poor medium for plant growth. As its thickness in the 

Anchorage area was only about a quarter of an inch or less, 

however, its available nutrients should not greatly influence 

the total available through the plow depth, in this case. The 

available phosphorus test showing of "none" is somewhat surprising in view of the quite normal amount of total P205 in the 

Mount Spurr ash (p. 458, analysis 1). This total phosphorus can 

probably be assumed to be in the glassy portion or in the mineral 

apatite, or in both, as found in similar ash from other volcanoes, 

which do show a certain amount of phosphorus in the available 

form.

The first examination of the Mount Katmai ash of 1912 was 

apparently made by Fry (1912) of the U.S. Department of Agriculture. Three samples of ash, representing the successive ash 

falls of June 6-8 at the village of Kodiak were found to consist 

predominantly of glass shards with varying amounts of crystalline minerals. Considering them from the agricultural standpoint, 

he stated:

There is every reason to anticipate that these glasses, as well as the definite 

minerals, would dissolve, hydrolize, and behave as would ordinary soil minerals . . . , and on the whole these falls will probably serve ultimately as an 

enrichment of the preexisting soil, although it by no means follows that the 

immediate effects will be satisfactory.

A very few data on the availability of nitrogen in the ash of 

eruption of Mount Katmai are furnished by Shipley (1919a), and 

are summarized in the following table. From them it may be 

concluded, first, that the raw ash has a very low content of nitrogen, or none at all in the case of the ash flow from Katmai volcano, and second, that there was a measurable amount of nigrogen 

in ash around springs in which algae were growing, and a much 

higher content of nitrogen in reworked river-bottom ash in which 

seedlings were thriving. None of these media contained anything 

near the amount of nitrogen found in the normal tundra soil. 

Shipley gives no data on available potash and phosphorus although 

he recounts a few tests for apparent soluble salt content, made 

by an electrical resistance method, which showed great differences 

from the tests on normal soils.

Some of the volcanic ash of the Mount Katmai area not only 

did not support vegetation but appeared to have toxic effect on 

germinating seedlings. Shipley (1919b) concluded that the effect 

was probably due to the high content of ferrous sulfate (0.081 

and 0.300 percent sulfate ion in two samples), which would handicap the functioning of the nitrifying bacteria.
460 INVESTIGATIONS OF ALASKAN VOLCANOES

Results of tests jor, -nitrogen in ash of 1912 eruption of Mount Katmai

[Shipley, 1919a]

Location and description of sample

Mount Katmai volcano:

Section 8 miles south of Mount Katmai crater:

Observation Mountain:

Katmai River:

Kashvik Bay:

Tundra, 12 in. thick ...............................

Nitrogen in parts per million

as NUa

Trace 

None

None 

None 

0.01 

.01 

.01 

.02

.02 

.04 

.04

.4 

Trace

2.4

as NOa

0.0004 

None

None 

None 

None 

None 

None 

None

.0004 

None 

.004

.004 

Trace

.012

Total N

0.8

None

.05

32.0 

32.0

4320

According to Griggs (1922, p. 46), ash at Kodiak village showed 

"available potash (K20) 0.05 percent" and a "small amount" of 

phosphoric acid. He concluded from pot tests on ash alone and 

with varying added chemical fertilizers that, although wheat 

would germinate and start to grow in the raw ash, some addition 

of nitrogen, phosphorus, and potash was necessary to prevent 

their early death. It was found at Kodiak that addition of nitrate 

alone to the ash covered fields produced fair harvests of ensilage 

during the 1913 season.

The low ion-exchange capacity of fresh volcanic ash can no 

doubt be attributed to the absence of clay minerals, organic matter, 

and other ultrafine material. Baak (1949, p. 55) emphasized that 

in typical Indonesian eruptions, the amount of material smaller 

than a half micron is always less than 1 percent by weight, and 

this generalization is no doubt valid for most freshly erupted 

volcanic ash of other parts of the world. The initial pH of suspensions of volcanic ash may be quite acidic, owing mainly to 

absorbed soluble acid constituents, as discussed in the section 

above on public health. These suspensions commonly revert to a 

neutral or slightly alkaline condition as the ash itself gradually 

makes contributions to the solution, and a similar situation may 

arise in the ash layer in place on the ground as well as a flushing 

out of the soluble acidic constituents by percolating water.
SOME EFFECTS OF RECENT VOLCANIC ASH FALLS 461

Weathering and soil-forming processes begin immediately after 

the deposition of the ash in those portions exposed to the air and 

ground water. The ultimate product is a material stable in this 

environment, normally a soil rich in clay minerals. Volcanic ash, 

especially the glassy portion, is unstable, and it weathers to clay 

at a much more rapid rate than dense crystalline rocks, both 

because of the relative vulnerability of the glass to chemical attack and because its granular character permits easy access of 

altering solutions. Yet in terms of the human life span, it requires 

much time. Fifty years after the 1883 eruption of Krakatau 

volcano, for instance, the surface ash seemed to show no discernible development of clay minerals (Mohr and van Baren, 1954, 

p. 214), in spite of an abundant growth of new vegetation. No 

doubt the rate of weathering in the Alaskan and Aleutian climates 

can be presumed to be even slower than in the tropical climate of 

Pulau Krakatau. Dickson and Crocker (1954), studying the 

soil on a 1,200-year old volcanic mudflow from Mount Shasta, Calif., 

found only a thin opaque coating on the glass fragments as indication of weathering. Crystalline fragments such as plagioclase, 

pyroxene and amphibole showed no apparent effects after 1,200 

years of exposure to weathering agencies.

The mechanisms of weathering of natural minerals and glasses 

are only poorly understood, and much more observational data 

under controlled natural conditions are needed. Fieldes and Swindale (1954), investigating soils of Pacific islands and New Zealand list five groups of materials in order of increasing resistance 

to weathering: (1) olivine, pyroxene, and hornblende; (2) basic 

volcanic glass and zeolites; (3) mica; (4) acid volcanic glass and 

feldspars; and (5) quartz. They conclude that basic volcanic 

glass (glass high in iron, magnesium, and calcium) weathers 

first to amorphous hydrous oxides of iron, aluminum, and silicon, 

then to allophane or gibbsite and finally to kaolin or montmorillonite, depending on whether hydrogen ions or calcium ions predominate, respectively. The acid volcanic glasses with which they 

dealt weather first to amorphous hydrous oxides of aluminum 

and silicon and then to allophane or kaolin.

The gradual breakdown of volcanic glass and crystalline material during weathering is accompanied by release of elements to 

ground solutions, and among these elements are calcium, potassium, phosphorus, and certain trace elements important in plant 

nutrition. Thus plant food is made available at a slow rate, which 

perhaps becomes even slower as residual decomposition products 

form mantles on the original particles. The very slowness of
462 INVESTIGATIONS OF ALASKAN VOLCANOES

release of these food elements may be an advantage in some circumstances, however, as pointed out by Keller (1948), who advo^ 

cates the application of certain natural rock materials, among them 

volcanic ash, to the land as fertilizers to provide a steady supply 

of plant food over many growing seasons. For similar reasons 

Mclntyre (1954) and Nestle (1955) have proposed artificially 

compounded silica-glasses as advantageous vehicles for furnishing 

minute but steady supplies of certain "trace element" nutrients, 

such as boron, copper, zinc, manganese, and molybdenum, to the 

plants over a period of years.

RECOLONIZATION BY NATURAL. VEGETATION

The problem of natural recovery of plants in an area devastated 

by volcanic activity is very complex, and discussion is handicapped 

by lack of information. The problem has interested botanists and 

ecologists for many generations, yet the few results, often quoted, 

are based on studies that were discouragingly incomplete. Most 

frequently mentioned perhaps are the discussions of the recolonization of the islands devastated by the catastrophic eruption of 

Krakatau in 1883, and this recolonization has indeed become a 

classic example, owing to the work of Verbeek, Treub, Ernst, and 

Doctors van Leeuwen. Some disagreement has been expressed 

with the assumption by other investigators that the eruption 

resulted in total destruction of plant life and that all new-appearing plants must have come from outside by seed or spores. The 

problem is summarized briefly in a recent paper by Went (1949).

The recovery of vegetation after the 1912 eruption of Mount 

Katmai was the subject of a series of papers by Griggs and his 

coworkers, and the papers offer, perhaps, more useful data than the 

series on Krakatau, especially as applied to the Alaskan situation. 

Mount Katmai's eruption was nearly as intense as that of Krakatau, although it apparently caused no loss of human life. (In 

contrast, 28,000 persons were killed by Krakatau's outburst and 

its accompanying seismic sea waves.) The ash deposits from 

the Mount Katmai eruption were of two types: those of material 

transported through the air and those of material that moved 

along the ground surface as ash flows. The ash-fall deposits were 

several tens of feet thick in the vicinity of the volcano, thinning 

to less than a foot at Kodiak, a hundred miles south. The ash flow 

deposits extended only a few miles but ranged in thickness from 

several feet to several hundred feet.

The recovery of vegetation on Kodiak Island, according to 

Griggs (1918a, 1922), was faster than had been expected in view
SOME EFFECTS OF RECENT VOLCANIC ASH FALLS 463

of the initial desolation in June 1912, and more than bore out 

the prediction of Fry (1912) quoted above. The 10-inch deposit 

of ash had smothered all low vegetation and weighted down 

branches of pine and deciduous trees. By September 1912 the ash 

had compacted somewhat, and shrinkage cracks as much as 2 

inches wide had formed in it; some vegetation had already started 

and shoots were developing along these cracks. In 1913 it was 

found that most trees around Kodiak village had survived, having 

lost much of their burden of ash by this time and replaced the 

foliage that had been destroyed. There was still little or no undergrowth and other low vegetation, however, and only a few lupine, 

fireweeds, and other perennials had come up through the ash 

blanket. A strong detriment to survival of young plants, and one 

that has been noted in many other areas devastated by ash fall, 

was the cutting effect of wind-blown ash.

In 1915, when Griggs next visited Kodiak Island, the whole 

area was once again green with a vegetative cover. Tree seedlings 

had begun to appear and persisted through the following winter 

season. The grasses not only had recovered, but they and other 

small plants were thriving as never before. The ash mantle had decreased somewhat in thickness, owing mainly to compaction and 

local erosion, and most of the new growth had come, not from new 

seeds sprouting in the ash layer, but from old roots in the original 

soil. A species of field horsetail (Equisetum arvense) was able to 

send up shoots from old roots through two or more feet of ash 

cover, and this plant spread rapidly in the absence of competition 

from other plants, acting as an effective deterrent to wind and 

water erosion. Grass seed planted in the ash layer was able in 

places to subsist but did not flourish. The detrimental effect of 

sand blast by blowing ash appeared to be decreasing from season 

to season as more and more of the area was protected by the 

encroaching vegetation.

The beneficial effects of the ash to plant growth on Kodiak 

Island after the initial setback was amply demonstrated. According to the inhabitants the pasture grass and garden vegetables 

were growing more vigorously a few seasons after the ash fall than 

they had previously. A spectacular, though not entirely typical, 

example is a tree cut several seasons after the ash fall (Griggs, 

1922, p. 48) showing yearly growth rings after 1913 five times 

thicker than those formed before the eruption. Griggs (1922, p. 

47) concluded that the increased growth rate of most plants was 

due, not to the effect of added plant nutrients, but to the mulching 

effect of the ash when mixed in old soil and to the destruction of
464 INVESTIGATIONS OF ALASKAN VOLCANOES

competing plants. This conclusion was based, however, on limited 

tests of the plant nutrients that might be available in the ash, 

and it is felt that the conclusion perhaps should be held in 

abeyance.

On the mainland in the vicinity of Mount Katmai and the 

Valley of Ten Thousand Smokes, where the thickness of the ash 

was on the order of feet rather than inches, the recovery of 

vegetation was markedly slower than at Kodiak Island, and even 

today, almost a half century after the eruption, there are large 

areas on the great ash flow of the valley that, to all appearances, 

remain without vegetation. Griggs first examined the damage on 

the peninsula briefly in the summer of 1913 while engaged in kelp 

studies for the Bureau of Soils of the U.S. Department of Agriculture (Griggs, 1915), and returned for more extensive studies 

in 1915, 1916, and 1917 at the head of the National Geographic 

Society expeditions (Griggs, 1918b, 1919a and &). He landed in 

1913 at Russian Anchorage, 25 miles east-southeast of Mount 

Katmai, where he found that alders and most birch trees on slopes 

exposed toward the volcano had no leaves, although many of their 

twigs were flexible and the interior wood was green. In sites 

sheltered from the volcano the alders were in full foliage. Elderberry and devilsclub foliage showed some blight, as if from fumes 

during the 1913 growing season. A vigorous growth of horsetails, 

as at Kodiak Island, was found locally, in gullies partly cut through 

the 3-foot deposit of ash.

Following the more extensive studies in subsequent years in 

the vicinity of Mount Katmai, Griggs (1919a) divided the whole 

of the affected region into six areas on the basis of the type of 

plant damage: (1) the outermost zone where plants were locally 

affected by acid rains but otherwise undamaged; (2) Kodiak and 

Afognak Islands where ash fall had greatly damaged small plants 

but had very little effect on trees and bushes; (3) areas of slight 

injury on the mainland; (4) zone where trees had been killed but 

grasses had recovered; (5) zone of heavy ash fall where trees 

were killed and herbage buried; and (6) Valley of Ten Thousand 

Smokes and Katmai Pass where all vegetation had been incinerated 

by the incandescent ash flow. The last four of these zones are 

indicated on the map of figure 72, taken from Griggs (1919a 

and b).

A zone in which many trees were killed but herbage had recovered extended as a curving band 5 to 10 miles wide from Katmai 

village on the south coast around west of Novarupta, generally 

between the 1-foot and 3-foot lines of ash depth and interrupted
SOME EFFECTS OF RECENT VOLCANIC ASH FALLS 465

58°30'

Irees killed, herbage buried 

Trees killed, herbage recoverec

J 580 3Cy

FIGURE 72. Map of Mount Katmai, Alaska, showing destruction of vegetation in 1912 by the 

eruption and thickness of ash deposit (after Griggs, 1919b).

by the ash flow of the Valley of Ten Thousand Smokes. In this 

zone rank growths of low plants, mostly grasses such as horsetail 

and blue joint, had been able to come up through the ash layer 

from old roots.

To the east and south of the divide marked by Trident Volcano
466 INVESTIGATIONS OF ALASKAN VOLCANOES

and extended to Amalik Bay lay a zone in which most trees were 

killed and herbage was buried too deeply by the ash fall to recover (map, fig. 72). The northern limit of this zone is indefinite 

because of lack of information. It lay within the zone of heavy 

ash fall, with thickness generally greater than 2 feet. Curiously, 

here some smaller balsam poplars survived, though adjacent larger 

ones were dead. Alders and most birches in valley of Katmai 

River had been killed, but willows seemed to have recovered better 

than the other trees. Low herbage had not reappeared except 

where ash had been partly removed and growth started again from 

old roots, as had been seen the first season after the eruption in the 

area around Russian Anchorage.

Griggs (1919&) concluded that all flowering plants had been 

damaged severely in these zones and that some species recovered 

more rapidly than others mainly because of special abilities that 

.enabled them to cope better with the situation. He nrgued against 

toxic fumes at ordinary temperatures as the cause of widespread 

damage and proposed that a radially directed hot blast was responsible. These arguments are not altogether convincing, and 

it is felt that questions still remain. Although Griggs regarded the 

zones of damage as not concentric about the volcano, it seems 

fairly obvious from examination of his map, figure 72, that the 

different zones of damage can be correlated with the configurations of the two types of ash deposits: the ash fall strewn out 

downwind with its fumes, and the incandescent ash flow of the 

Valley of Ten Thousand Smokes.

The zone of plant incineration includes the Valley of Ten Thousand Smokes and the Katmai Pass areas, in which all plant life 

was buried by the sudden outflow of ash, initially called a "hot 

mud flow" by Griggs (1918&) but later shown by Fenner 1923) 

to have been an incandescent ash flow. The thickness of this ash 

flow deposit is still not known but must be several hundred feet 

in the medial part of the valley, thinning to as little as 10 

feet on the lateral edges and lower extremity. Former tundra vegetation, within but near the edges of the flow, was found to have 

been reduced to a thin layer of charcoal, and all parts of trees 

immersed in the ash flow were thoroughly charred. In areas of 

undisturbed bare ash on the surface of the ash flow, no vegetation had appeared by the end of 7 years, and when Griggs returned 

in 1930 at the end of 18 years only one type of plant, the leafy 

liverworts, had obtained a significant foothold (Griggs, 1933). 

Locally they formed a felted carpet half an inch thick that extended 

its cover as far as the stability of the ash soil permitted, that is,
SOME EFFECTS OF RECENT VOLCANIC ASH FALLS 467

up to the edge of areas of erosion and deposition. The gradual reduction of the extent of bare ash surfaces, with the encroachment 

of liverworts over undisturbed ash and other plant types on reworked ash, was leading to a decreasing rate of wind erosion and 

sand blasting and, with this, to an increased momentum in the 

progress toward stabilization.

The presence of the liverworts as thriving pioneers on the raw 

ash surface and their absence or very subordinate role on reworked ash and old soil surfaces at Mount Katmai in 1930 led 

Griggs to investigate these plants in some detail, especially as 

regards their requirements for nitrogen, which he had found to 

be notably lacking in the raw ash. Griggs concluded (1933, 1936) 

that these particular liverworts, especially CephalozieUa byssacea, 

could thrive on lower concentrations of nitrogen compounds in 

the soil than other competing types, such as mosses, algae, and 

seed plants. Smith and Griggs (1932) ran laboratory tests on 

bacteria (chiefly B. radiobacters) associated with the liverworts 

and found none of them able to fix atmospheric nitrogen. Additional laboratory investigations by Griggs and Ready (1934) confirmed that the liverworts could subsist and reproduce, apparently 

on amounts of nitrogen too low to be detected by the available 

chemical tests, and that when the nitrogen content of the media 

was high, the competing plants, such as mosses and algae, 

smothered the very slow growing liverworts. They suggest that 

the amount of ammonia in the rainfall at Mount Katmai, even 

though very low as compared with industrialized areas, might 

have been sufficient to support the liverwort growth.

Additional studies of revegetation near Mount Katmai were 

started in the 1953 and 1954 seasons by V. H. Cahalane as part of 

a cooperative project of the National Park Service and other 

governmental agencies and organizations. Although Cahalane was 

unable to adequately resurvey the same ground in Valley of Katmai 

River in which so much of Griggs' work had been concentrated, 

he made collections at three stations there for comparison with 

Griggs' collections of 1915-17. In the Valley of Ten Thousand 

Smokes, much of which was still barren, six plots of about oneeighth acre size of differing degrees of vegetative cover were 

laid out in differing ecological situations as a start toward a longterm systematic investigation of the vegetation recovery. Results 

of this initial survey are to be published at an early date by the 

National Park Service (Cahalane, written communication). The 

extensive mats of liverworts described by Griggs on the ash-flow 

surface no longer existed in 1953-54. Algae and mosses, too, had
468 INVESTIGATIONS OF ALASKAN VOLCANOES

practically vanished except for a few survivors in the throats of 

the declining1 fumaroles. The disappearance of the liverworts, 

algae, and mosses from the ash flow surface is related by Cahalane 

to the cessation of permeation of the ash by steam. On the hill 

slopes away from the ash flow in 1953 and 1954, there was a 

considerable representation of horsetail, fireweed, small willows, 

grasses, and sedges, and in the bottoms of shallow depressions 

there was abundant alpine wood rush. Wind erosion, sand blasting, 

and rapid desiccation of the ash "soil" continued to be important 

deterrants to vegetative recovery on the hill slopes as well as on 

the valley ash flow.

At Paricutin volcano in Mexico the prolongation of ash eruptions for several years after the initial strong activity of 1943 

acted as a handicap to the recovery of natural vegetation. The 

problem was studied by Eggler (1948) 2i/£ years after the start 

of the eruption. He found that oaks had apparently survived in 

ash depths up to 70 inches, alder, in depths up to 59 inches; some 

pines (5 to 12 inches in diameter), in depths up to 49 inches; 

Cmtaegus, in depths to 40 inches; and trailing-arbutus, up to 35 

inches. The most hardy shrubs were Oestrum and Smilax, which 

survived in ash depths as great as 50 inches, while the common 

Baccharis survived after burial to as much as 22 inches and 

showed ability to put out adventitious roots from the buried 

parts of the stems. Among the herbaceous plants, the prickly 

poppy and mimosa survived in ash depths up to 29 inches. A most 

important survivor in ash depths of less than 10 inches was Bermuda grass, which was spreading vegetatively in some areas and, 

with somewhat less persistent crabgrass, was acting to check erosion. Reproduction from seeds in the undisturbed ash had not 

yet become significant for any of the plants by 1946.

Bare lava flows appear to require enormously greater time for 

plant colonization than ash deposits in a similar environment; 

in some cases at least, the recovery lags until windblown or 

waterborne clastic material filters into cracks or is added to the 

surface. The smooth lava surface alone in a dry or cold climate 

would not ordinarily support vegetation, until its mechanical and 

chemical breakdown is well underway. In some tropical regions 

of very high year-round rainfall, however, such as in parts of Hawaii and the Belgian Congo, the vegetation does not observe this 

restriction, and certain types of trees and other plants spring up 

within a matter of months after the lava surface (but not necessarily the interior of the flow) has cooled. It may be simply that 

a hydroponic situation is involved that makes unnecessary a
SOME EFFECTS OF RECENT VOLCANIC ASH FALLS 469

granular substrate to protect seeds and rootlets from intermittent 

desiccation.

Lichens are commonly the pioneers on bare lava surfaces 

(Forbes, 1912; Robyns and Lamb, 1939; Eggler, 1941), and they, 

perhaps with other elementary forms of plant life able to endure 

long periods of desiccation, may appear on the rock surfaces soon 

after the flow has been emplaced. Although they provide significant aid to the inorganic chemical and mechanical agents of 

rock weathering in the long process of reducing the surface to a 

condition suitable for growth of higher orders of plants, doubt has 

been expressed that they are commonly able themselves to provide 

an adequate mat on which larger plants may subsist. It is obvious 

that without the intervention of other factors it would take many 

hundreds or thousands of years to produce a true soil in this 

manner.

Usually there is at least a small amount of airborne dust deposited on the lava surface, and this eventually comes to rest in 

the cracks and small depressions that abound on the lava. Cracks 

appear to be significant sites for the beginning of revegetation, 

and, according to Eggler (1941), the most favorable situations 

in the lavas of the Snake River Plains of Idaho are crevices 

just deep and narrow enough to provide a soil in their bottoms and 

protection from the wind and sun for the aerial parts of the plants 

that get a start. Thin pockets of soil (in part wind transported) 

on the young Carrizozo basalt flow of south-central New Mexico 

are found by Shields, Mitchell and Drouet (1957) to support 

algal and lichen growths, which in turn may be important nitrogen sources for higher order seed plants. It has been found, both 

in Idaho and Hawaii, that plant colonization on smooth (pahoehoe) surfaces proceeds to completion somewhat faster than that 

on craggy or rubbly (aa) surfaces, and this has been attributed 

to the availability on the smooth lava of more suitable sites for 

plant growth in the abundant cracks that catch the small amount 

of airborne dust. A similar amount of airborne dust deposited 

on the craggy or rubbly surface filters down to depths too great 

to permit germination of the seed or growth of the plants.

Plant foliage protruding out of the cracks induces additional 

deposition of windblown soil, as well as providing bulk to the 

deposit in the form of fallen leaves and other plant debris from 

season to season. As the cracks fill up the deposit begins to extend 

laterally over the lava surface and provides a larger area for 

plant growth but a new environmental situation. The plant types 

adaptable to this situation may be different from those that grew
470 INVESTIGATIONS OF ALASKAN VOLCANOES

in the crevices, and in the Snake River Plain, the new assemblage, 

which also becomes the climax type, is dominated by grasses and 

sagebrush (Eggler, 1941).

Eruption of abundant pyroclastic material simultaneously with 

the lavas from some volcanoes leads to mantling of earlier lava 

flows by airborne volcanic ash and immediately gives a great 

advantage in revegetation to these flows over flows that lack the 

mantle. In this manner a granular "protosoil" is provided readymade, and on a thick cover of this kind colonization may proceed 

much in the manner discussed above for revegetation of ash deposits on old soil. Many lava flows in areas of topographic relief 

are favorably situated also to receive ash brought in from surrounding ash-mantled slopes by gravity, water or wind. Where 

there has been appreciable admixture of old soil and organic 

debris, these secondary deposits may even furnish a medium for 

agricultural rehabilitation.

Long-range beneficial effects of submarine volcanic activity on 

marine life, analogous in some ways to the beneficial effects of 

subaerial volcanism on subaerial plant life discussed above, are 

suggested by Buljan (1955), based chiefly on his studies of the 

Adriatic Sea and adjacent waters. He outlines evidence indicating 

that significant amounts of nutrient materials, notably compounds 

of phosphorus, nitrogen, silicon, iron, and others, are introduced 

into waters in areas of recurrent submarine volcanic activity, 

chiefly in the form of vapor exhalations. These may play an 

important part in increasing the productivity of these areas, and 

in this respect Buljan cites the abundance of marine organisms in 

such volcanically active areas as the Japanese, Indonesian, and 

Aleutian arcs.

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SOME EFFECTS OF RECENT VOLCANIC ASH FALLS 473

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INDEX

Page

Abstract .._..___..__..__..__.._._ 409-410 

Acid rains ._._._...__._.__._.._.__ 427 

Acknowledgments ________............ 410-411

Aerosol mist, effect on plants...._~_.... 452-463

Agriculture, effects of volcanic eruptions

on ....___...._..... ._ .-_.... 450-452

Air traffic, hazards to, from ash fall...... 448-449

Alaskan Peninsula, rocks_...........___...... 414

Aleutian arc, rocks of.... _....._._. _.. 414

Aleutian Islands, animals and

vegetation _._....._........._ 414-415

volcanic arc ....____.._........ ....... 413-414

Aleutian Range, character of....__..._.... 413

Aleutian Trench, depth.-.......-........ .,. 413-414

Analyses of ash deposits-_...._..._......_ 458, 4GO

Anchorage, Alaska, ash fall, thickness. 422-423 

ash deposits at, results of soil tests.... 459

water supply, effects of ash fall on 445-446 

Area of the report-_.................... ....... 411-412

Ash, suspended, effect of on infaJl of

solar energy . ..._..... .._... .... 427

Ash clouds, Hekla volcano._......... ..._.... 429

eruption of Mount Spurr................ 422

movement of ....__........... 429, 431, 432-433

Volcan Quizapu _.._____............... 432-433

Ash deposits, chemical composition of-_ 458 

development of soil on.............. 429-430, 432

permeability of .___.____..._.._.._ 449 

physical characteristics of,

importance of _...._.............. 457

removal ...........__..._.._.._._._._......_... 450

thickness, Mount Katmai- 415-416, 427, 460 

Paricutin ....___......_____. 436

Volcan Quizapu .__...__.._........ 433-434

weathering of .._._.___..................... 461-462

Ash fall, beneficial effects of.... 456-457, 463-464

change in composition.... ...._.__.. 435

changes in mineral constituents..... .. 434

health hazard from.._._......_..__ 444-445

immediate effects of...___._._ 450-456 

long-range effects of .... ..___... 456-462

Mount Katmai eruption_.____.... 427

distribution pattern ____......__..._ 426

Ash distribution, from eruption of

Mount Spurr .............. 422-423, 424

hypothetical estimates of-_..__._ 439-440

pattern of ~.__..._____...___. 434-435

Ash particles, size distribution.__ 429-430, 431

Bering Sea, depth._.___............___ 413-414

Borris, F. S., White, Katrine, and

Phillips, H. F., analyses by.. 458

Page

Buildings, danger of damage to......._. ...... 447

Chemical composition of ejected

material, change in............ 428-429

Clouds, eruptive, Hekla volcano_........_ 428

See also Ash clouds. 

Cordova, Alaska, acid rains at .... .. 427

Dome, lava _._....._...._._.._.._._... 419-420

Earthquakes preceding eruption,

of Mount Katmai........... 416-417

Effusive eruptions, contrast to

explosive eruptions .._._..._... 425 

Electric power, hazards to,

from ash fall..............__.. 447-448

Eruptions, Alaskan volcanoes,

character of ...... .......... 415-423

effects ......____._:'_._ ..... 441-462

frequency of .... _... ...... .. .. 410

Eruptive sequences, declining phases. 425-426 

outbreak of eruption ..._...... ._ ... 425

preliminary symptoms ........_.. . 423

Fenner, C. N., analyses by.... .. 458

Fertilizer, use of volcanic ash for. 457, 462

Fishing industry, effect of ash fall on 456

Floods, danger from. . .__.. 449-450, 451

Hekla volcano ........_.._..__....__ 429

Forests, on the Alaskan Peninsula 414-415 

Fry, W. H. quoted ..__...___..___- 459

Gases from volcanoes. See Volcanic gases. 

Geography . ...____. .... __._ 413-415

Hailstorms, accompanying volcanic

eruptions _________~ 451

Hekla volcano, description of eruption.. 428-432

effect of eruption on fishing industry 456

Industrial gases, compared with

volcanic gases ......_.... 442-444, 452

Introduction ...... ... ..... . 410

Katmai, Mount, area covered by ash from 427 

ash from, chemical composition..... 457-460

results of tests for nitrogen in.... 460

caldera of ______________-__ 418 

destruction of vegetation by ash fall 453 

erupted material, volume of_......_ 415-416

eruption of, description...._~__ . 417-418

events preceding eruption...._...._. 416-417

Katmai village, evacuation of .. 416-417

475
476 INDEX

Page 

Kelud, Gunung, eruption of ..... _.. 434-435

Kodiak, Alaska, ash deposits in...._...... 427, 460

Kodiak Island, ash deposits on,

beneficial effects ........... 463

ash deposits on, thickness.... .. .... 415-416

destruction of vegetation by ash fall 454 

recovery of vegetation on....__.... 462-464

Lava flows, Hekla volcano..........._.....__ 428

Okmok Volcano .......... ......_ .._..._ 419

Parfcutin .__._____.............. ._. 436

plant colonization on.... . _._ .. 468-470

Lichens .__.. _.... .._...._ ... .__...__.... 469

Livestock raising, effect of ash fall on.. 455-456 

Liverwort, studies of growth habits.._ 466-467 

Logging industry, effects of ash fall on 455

Marine life, beneficial effects of

submarine volcanic activity.. 470 

Martin, Paul, soil tests by. .. ....._.. 458

Mudflows, danger from........ ...._... .. 449-450

Hekla volcano . ... ..........._.... 429

Mount Spurr ....... __._. .._ ___... 422

Trident Volcano .__..... .._._.... 419

Nitrogen, in ash deposits, reults of teats.. 460

requirements of liverwort...._...._..._ 467

unavailable in Mount Spurr ash. ...... 459

Noises of eruption, Hekla volcano...__..... 428

Mount Katmai ..__._.............__..__ 417

Okmok Volcano, caldera of... ... . 418 

lava from ... _._.._...._..........__.. 419

observation of eruption of.. . 418-419 

Orchards, effects of ash fall. ___ 454 

Parfcutin, ash fall from, effect on

local water supplies .. 446-447 

destruction of vegetation by

ash fall .................................. 454-455

eruption of .._._.........__.,__... 435-438

floods following eruption.... _..- 450

recovery of natural vegetation.____ 468 

Phillips, H. F., with Borris, F. S., and

White, Katrine, analyses by 468 

Plants, Aleutian Islands.._......_... .. . 414-415

effect of ash fall from Mount

Katmai on ............... ...... 415-416,

453,454, 464-468 

effects of volcanic gases on............... 452

immediate effects of ash fall on....... 451

marine, effects of eruption on. . .... 456

recolonization on ash_......___....... 462-468

regrowth of, in Mount Katmai area 464-468 

zones of damage...._ ..__...... _ 464-468

Pneumonoconiosis .__..._ -_ -__ - 444 

Prediction of eruptions, problems... 426 

Preliminary symptoms of eruption,

Hekla eruption ._______- 428 

Mount Katmai .__..........__ ... 416-417

Mount Spurr eruption. .. 421

Page 

Previous observations ... .... . _._.._ 412-413

Public health and safety, effect of

volcanic eruptions on.. ... 441-447 

Purpose of the report.. ..........._....._..... 410

Pyroclastic material, Hekla volcano. 428

Quizapu, Volcan, composition of 

ash deposits from......

description of eruption. ..

.......... 434

...... 432-434

Rains, accompanying volcanic eruptions.. 451 

effect of, in volcanic eruptions. 441 

Redoubt Volcano, hypothetical

distribution of ash from.... 439-440

Savonoski, Alaska, evacuation of_ . 416-417 

Scope of the report...._.._. . ... .... 411 

Seismic records, of eruption of

Mount Spurr .........___.......... 422

Settlements near active volcanoes,

types of ... _... 414 

Seward, Alaska, acid rains at..__._...... 427

Ship Creek, water of, effect of ash fall on 446 

Silicosis ..........___. .... . ____ 444

Soil, development of, on ash

deposits ......._............ 429-430, 432

tundra ___...... ....__...._...___. 414-415

Soil nutrients, test for-___-__.... 457-458

Soil tests in ash from Mount Spurr,

results of ._...... ____ 458

Spencer, Cape, acid fumes at, effects of . 427 

Spurr, Mount, observations of eruption 420-422

Telephone facilities, disruption of. 448

Tilting of the land surface. .._.___ 423-424

Transportation, hindrances to,

by ash fall ..__..____ 448

Trident Volcano, ash ejected from..__ 419-420 

mudflows from ...._ .. . __ .. 419

observations of eruption...._......_ 419-420

volume of material erupted _._._.._ 420

Umnak Island .....__................ ..__. 418-419

Valley of Ten Thousand Smokes,

material from vents.... 415-416, 418

recovery of vegetation...... _....... 464-467

Vegetation. See Plants.

Volcanic arcs, of the Pacific Ocean...... 413-414

Volcanic eruptions, effects of, on public

health and safety....,.. 441-447 

Volcanic gases, effects of___ 442-444, 452-453

Water supplies, effects of ash fall on. 445 

Weathering, of ash deposits_..___ 461-462 

White, Katrine, with Borris, F. S., and

Phillips, H. F., analyses by.. 458 

Winds, effects on ash distribution___- 436, 438

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