Volcanic Eruptions of 1980 

·at Mount St. Helens 

The First 100 Days 

Volcanic Eruptions of 1980 

at Mount St. Helenls 

The First 100 Da)'S 
Photographs of Mount St. Helens after (top) and before (bottom) the May 18, 1980, eruption, taken from exactly the same spot at 

Coldwater II observation station, 5. 7 miles north-northwest of the peak. Haze in the top view is mostly airborne volcanic ash, which is 

present near the volcano during all but the calmest (or rainy) days. These photographs were taken by Harry Glicken on May 17 and 

September 10, 1980. 
Volcanic Eruptions of 1980 

at Mount St. Helens 

The First 100 Days 

By BRUCE L. FOXWORTHY arzd MARY HILL 

GEOLOGICAL SURVEY PROFESSIONAL PAPER 1249 

UNITED STATES GOVERNMENT PRINTING OFFICE, WASHINGTON: 1982 
UNITED STATES DEPARTMENT OF THE .INTERIOR 

JAMES G. WAIT, Secretary 

GEOLOGICAL SURVEY 

Dallas L. Peck, Director 

r Library of Congress Cataloging in Publication Data 

Foxworthy, B. L. (Bruce LaVerne), 1925-

Volcanic eruptions of 1980 at Mount St. Helens. 

(Geological Survey professional paper ; 1249) 

Bibliography: p. 

Supt. of Docs. no.: I 19.16:1249 

1. Saint Helens, Mount (Wash.)-Eruption, 1980. I. Hill, Mary, 1923-

(2ES23.S23F69 1982 551.2'1'0979784 82-600231 

. II. Title. III. Series. 

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

Washington, D.C. 20402 
IN DEDICATION 

DAVID A. JOHNSTON 

DECEMBER 1949-MAY 1980 

Volcanologist David A. Johnston writing 

field notes at Coldwater II observation 

station May 17, 1980, the evening before 

he was killed by the lateral blast of the 

Mount St. Helens eruption. Earlier in the 

day, Johnston had collected volcanic gas 

samples from a fumarole high on the 

unstable northern side of the volcano (see 

fig. 20.). This photograph was taken by 

Harry Glicken, who was relieved of his 

observer duties at Coldwater II by 

Johnston and who brought this film out 

of the area the night before the fatal eruption. 

Among those who lost their lives in the May 18, 1980, eruption of Mount St. Helens 

was an exceptional colleague, volcanologist David Johnston. 

David was special not only because he was the first member of the U.S. Geological 

Survey to die in a volcanic eruption but also because of his capabilities and his dedication to his science. He knew well the personal risks involved in studying active 

volcanoes. Yet, his belief in the need to better understand volcano behavior led him to 

vigorous service in the "front lines" at Mount St. Helens. Through it all, he displayed a 

rare combination of inventiveness and originality in his scientific observations and interpretations. 

On the morning of May 18, David was alone at the Coldwater II observation station, 

5.7 miles from the mountain's summit, measuring the volcano's bulging northern side. 

He was among the first to see the beginning of the eruption and tried to send a warning 

to the control center. "Vancouver, Vancouver, this is it!," he shouted into his radio. 

Then, as the black, billowing front of the lateral blast raced toward him, he tried a second message, which was garbled by atmospheric disturbance from the eruption. 

Then -nothing. 

The lateral blast obliterated Coldwater II observation station. Ironically, the location was (and is again) considered to be much safer than some of the sites on the mountain itself that David and his colleagues visited regularly. 

We dedicate this report to David Johnston, an untimely loss to his science as well as 

to his friends. 

PREF.ACE 

This report is unusual for the U.S. 

Geological Survey's Professional Paper 

series. Not only does it attempt to 

describe volcanic events that are unprecedented in United States history, it 

also tries to describe those events in 

ways that th~~ nontechnical reader will 

understand and in a context of human 

concerns to which he can relate. This 

account will serve as a backdrop for 

more technically written scientific 

reports on the volcanic activity at 

Mount St. Helens and the geologic and 

hydrologic effects of its eruptions. 

Because this report is intended for a 

broad audience consisting mainly of 

nonscientists, we have avoided technical language wherever it was possible. Discussions of the volcanic processes and related hazards, however, 

touch upon many scientific specialties 

and involve some terms and concepts 

for which nontechnical counterparts 

simply do not exist. Some of these 

technical terms are explained when 

they are used in the main body of the 

report, and some are defined in a 

glossary at the back of the report (p. 

121 ). A term that is explained in the 

glossary app~~ars in bold italicized type 

the first time that it is used in the text. 

Similarly, we have used mostly English units of measurement (inches, 

feet, miles, atnd so forth) rather than 

metric units for presenting quantitative 

information. Exceptions include altitudes and contour intervals (given in 

meters) on one of the general maps (fig. 

7) and ash thicknesses (given in millimeters) on the ash-distribution maps 

(figs. 35, 43, and 48). Temperatures are 

given in both Fahrenheit and Celsius 

units. A table for converting other 

units to the metric system is provided 

at the back of the report (p. 125 ). 

Although the words in this report 

are largely ours, most of the information comes from the work of many 

others. These information sources 

range from scientific publications 

prepared years before the 1980 eruptions to oral accounts, news releases, 

and data obtained after the major eruptions. It is impossible to present appropriate and balanced credits for all 

information and materials used; generally we have cited only the more readily indentifiable sources, such as 

photographers (in photographic credits) and published reports (listed in the 

reference section). 

Among the sources that can be identified are the daily, summary, and 

hazard reports prepared by the leaders 

of the U.S. Geological Survey's Mount 

St. Helens task force-Robert L. Christiansen, Dwight R. Crandell, Robert 

W. Decker, Donal R. Mullineaux, and 

Donald W. Petersen -and by the 

leader of the University of Washington 

seismology center, Stephen D. Malone. 

We also have borrowed freely from 

U.S. Geological Survey press releases 

prepared by Donovan Kelly, Edna C. 

King, and Donald R. Finley. With permission, we have quoted the eyewitness account provided by Keith L. 

Stoffel, first published in Information 

Circular 71 of the Washington Department of Natural Resources, Division of 

Geology and Earth Resources (Korosec 

and others, 1980). Many other eyewitness accounts and observations by 

both scientists and nonscientists are 

quoted or paraphrased. 

Christiansen provided us with a 

typescript copy of a paper published in 

Nature (June 19, 1980) (Christiansen, 

1980). We made extensive use of it and 

of monthly reports prepared by many 

scientists on the U.S. Geological 

Survey-University of Washington 

team. We also have quoted from 

Potential Hazards from Future Eruptions of Mount St. Helens Volcano, 

Washington, published as U.S. 

Geological Survey Bulletin 1383-C 

(Crandell and Mullineaux, 1978). The 

"Glossary of Volcanic and Related 

Terms" (p. 121) is derived largely from 

a glossary prepared by Roy A. Bailey. 

Although most of the technical information for this report was provided 

by colleagues in the U.S. Geological 

Survey, other individuals and agencies 

also provided valuable information. 

Malone furnished summary data on 

seismic events recorded by the University of Washington Geophysics Program. We used information selectively 

from bulletins prepared by the Mount 

St. Helens Technical Information Network; other information was taken 

from daily reports and news releases of 

the U.S. Forest Service, the U.S. Army 

Corps of Engineers, and the Federal 

Emergency Management Agency. For 

the human side of the volcanic events, 

we relied on the news media and a few 

personal interviews. 
Photographs used to depict various 

events or features discussed in the text 

were selected, insofar as it was practical, to reflect the first occurrence or 

discussion of the specific event or 

feature. Better illustrations of several 

subjects, however, are provided by 

photographs that were not strictly 

equivalent in time. Other illustrations 

are enhanced by paintings by U.S. 

Geological Survey hydrologist-artist 

Dee Molenaar. 

Technical reviews of part or all of 

this report were provided by Mullineaux, Peterson, Crandell, Molenaar, 

David G. Frank, David P. Dethier, 

Philip J. Carpenter, Edwin H. 

McGavock, John E. Cummans, Mark 

L. Holmes, and Jerry C. Stephens of 

the U.S. Geological Survey; Malone of 

the University of Washington Geophysics Program; James L. Unterwegner of the U.S. Forest Service; and 

geologists Vaughn E. Livingston, Jr., J. 

Eric Schuster, and Michael A. Korosec 

of the Washington Department of Natural Resources, Division of Geology 

and Earth Resources. Individual credits 

for the many other scientists, graphics 

specialists, and reviewers who contributed to this report are impractical, 

but the helpful cooperation of all is 

most gratefully acknowledged. 

Finally, we wish to acknowledge the 

key role played by David A. Rickert, 

assistant to the Chief Hydrologist of 

the U.S. Geological Survey, who developed the concept for this report and 

provided encouragement and many 

helpful suggestions during its preparation. 
CONrTENTS 

1 • Abstract 

2 • Introduction 

3 • Cascade Range volcanoes 

·~ • TABLE 1. Activity of major Cascade Range volcanoes 

9 • Mount St. Helens before 1980 

1.3 • TABLE 2. Summary of volcanic events and deposits formed at 

Mount St. Helens before 1980 

14 • Perception and warning of the hazards 

16 • Chronology of the first 100 days 

16 • lJnusual earthquakes begin 

18 • 1\sh eruptions begin 

20 • ~v1ountaintop cracks and craters grow 

25 • State of emergency 

30 • Eruptive activity decreases 

32 • r~orthern side bulges alarmingly 

37 • Eruptive activity resumes 

44 • <=ataclysmic eruption 

66 • c=ontinuing threats and mounting toll 

. 77 • 1\nother explosive eruption and its aftermath 

92 • ll"hird explosive eruption 

97 • Lava dome grows 

105 • At the end of the first 100 days 

105 • Summary of conditions 

114 • c:ontinuing hazards 

116 • Outlook for the future 

121 • Geologic hazard responsibilities 

121 • Glossary of volcanic and related terms 

123 • More about Mount St. Helens and other volcanoes 

125 • Unit conversion 

Volcanic Eruptions of 1980 at 

Moulnt St. Helens 

The First 100 Days 

By BRUCE L. FOXWORTHY and MARY HILL 

ABSTRACT 

On May 18, 1980, after nearly 2 months 

of local earthquakes and steam eruptions, 

picturesque Mount St. Helens, a Cascade 

Range volcano in southwestern Washington, suddenly began a major explosive 

eruption directed first northward and then 

upward. The lateral blast, which lasted 

only the first few minutes of a 9-hour continuous eruption, devastated more than 150 

square miles of forest and recreation area, 

killed countless animals, and left about 60 

persons dead or missing. The 9-hour eruption, the huge debris avalanche that immediately preceded it, and intermittent 

eruptions during the following 3 days 

removed about 4 billion cubic yards (0.7 

cubic mile) of new magmatic material and 

of the old upper and northern parts of the 

mountain, including about 170 million 

cubic yards (0.03 cubic mile) of glacial snow 

and ice. The eruption caused pyroclastic 

flows and many mudflows, the largest of 

which produced deposits so extensive and 

voluminous that they reached and blocked 

the shipping ch;-annel of the Columbia River 

about 70 river miles from the volcano. The 

May 18 eruption blew volcanic ash, consisting of pulverized old rock from the 

mountain's core as well as solidified new 

lava, more than 15 miles into the air. Winds 

carried the ash generally eastward across 

the United States and, in trace amounts, 

around the world. The ash, which fell in 

troublesome amounts as far east as western 

Montana, severely disrupted travel, caused 

widespread economic loss, and resulted in 

other problems that persisted to the end of 

the first 100 days of the volcano's activity 

(June 27, 1980). During that time, two other 

major eruptions (May 25 and June 12) also 

produced troublesome ashfalls in western 

Oregon and Washington. 

Mount St. Helens had been labeled in a 

1975 U.S. Geological Survey report as the 

Cascade volcano most likely to erupt. 

When frequent earthquakes began beneath 

the mountain on March 20, 1980, the potential for volcanic activity was recognized 

quickly by University of Washington 

seismologists and soon was accepted by 

most other knowledgeable scientists. Officials of emergency-services agencies and 

other appropriate organizations at all 

governmental levels were alerted to the 

possibility of an imminent eruption. Scientists quickly stepped up the collection and 

interpretation of pertinent geologic, 

geophysical, hydrologic, and atmospheric 

data. As events progressed toward the climactic eruption of May 18, scientists, lawenforcement officers, and other responsible 

officials teamed up in round-the-clock efforts to evaluate the increasing hazards and 

to protect tourists and local residents (often 

against their will) while also attempting to 

minimize panic and hardships among the 

citizenry. Officials of the State of Washington and the U.S. Forest Service established 

restricted-entry zones around the volcano. 

Most people respected these restrictions, 

but the spectacular eruptions of steam and 

ash from the mountaintop were an irresistible attraction to some, who entered the 

danger zone by way of logging roads too 

numerous to blockade. An information 

center established at Vancouver, . Wash., 

coordinated the release of warnings and 

other information, including thousands of 

news releases and responses to telephone inquiries, daily briefings by scientists, and explanatory meetings with officials and local 

citizens. 

From mid-April to May 17, eruptions 

and seismic activity diminished to such a 

degree that some residents and loggers were 

clamoring for entry into the restricted area 

near the volcano. (Limited entry was, in 

fact, granted on May 17 and scheduled also 

for the morning of the cataclysmic eruption.) The scientific data, however, showed 

that the mountain was bulging on its upper 

northern side and undergoing other ominous changes and, therefore, that the 

hazards were increasing rather than decreasing. Although opposition to official 

restrictions was widespread before the May 

18 eruption, the human responses to the 

far-reaching effects of that eruption included acts of exceptional heroism, and selfless 

cooperation was commonplace. 

The May 18 eruption differed from what 

was generally expected by the scientific 

team mainly in the character and destructiveness of the lateral blast and the lack of 

prior seismic warning. With these notable 

exceptions, the scientists' evaluation provided an ample hazard warning and unquestionably saved hundreds of lives. That 

evaluation was based not only on the 

many-faceted project for monitoring restless Mount St. Helens but also on information obtained by earlier geologic investigations of this volcano, of other Cascade 

volcanoes, and of other volcanoes 

throughout the world. 

Hazards that continued after the first 100 

days of activity at Mount St. Helens in 1980 

included possible ashfall and ash clouds, 

pyroclastic flows, lateral blasts, lava flows, 

floods, mudflows, and fires. The main 

flood hazard existed along the channels of 

the Toutle and lower Cowlitz Rivers, which 

were so choked with mudflow deposits 

from the May 18 eruption that normal wetseason runoff could have caused severe 

overbank flooding. Dredging undertaken 

on an emergency basis to open the channels 

probably will be continued in subsequent 

years. 

Abstract 1 
The volcanic activity at Mount St. 

Helens during the 100-day period ending 

June 27, 1980, is not exceptional in recorded 

history or in the evolution of the Cascade 

Range. Mount St. Helens was only one of 

perhaps 50 volcanoes worldwide that were 

active during 1980, although its May 18 

eruption was by far the most powerful during the year and, perhaps, during the last 

decade. At the end of the 100-day period, 

the mountain remained dangerous to those 

nearby, but the near-term likelihood of 

another eruption as destructive as that of 

May 18 was considered to be small. So far 

as is known, the 1980 eruptions of Mount 

St. Helens do not increase the probability 

that other Cascade Range volcanoes will 

erupt. The eruptions should, however, 

serve as a reminder that other Cascade 

volcanoes will erupt in the future as surely 

as they have in the past and that they are 

likely to produce effects that no amount of 

farsightedness or good intentions will be 

able to prevent. 

- The outlook for the future of Mount St. 

Helens and the areas that it affected can be 

discerned only partially. Salvage of blowndown timber was begun in June 1980, but 

proposals have been made to incorporate 

part of the devastated forest area into a 

park. Tourists are expected to be attracted 

in great numbers. Future uses of land near 

the volcano probably will resume largely as 

they were-forestry, farming, recreation, 

and hydropower generation-but will depend ultimately on the behavior of the 

volcano. The volcano might go through a 

period of dome building (as it was on June 

INTRODUCTION 

On May 18, 1980, Mount St. Helens 

in southwestern Washington exploded 

in a volcanic eruption more violent 

than any in the conterminous United 

States during the 20th century. An immense avalanche from the volcano's 

northern side was followed immediately by an explosive eruption directed 

first northward and then upward. The 

sustained lateral blast spewed hot gas 

and rock particles from the volcano at 

hurricane speeds, its devastation 

reaching nearly 16 miles outward from 

the volcano's center. Nearer the mountain, massive deposits of rock and ice 

from the avalanche were followed by 

intensely hot pyroclastic flows and by 

countless mudflows. In a wide swath 

northward from the mountain, survivors of the blast-plant, animal, or 

human-were rare. 

Some of the consequent, more distant effects of the May 18 eruption, 

which were themselves considered to 

be major disasters, included smothering layers of volcanic ash that fell on 

much of Washington and parts of other 

States. Others were the · extensive 

floods and mudflows that poured 

down stream courses leading_ from the 

mountain and left huge deposits of 

sediment that choked the channels of 

major rivers in southwestern Washington-even a part of the mighty Columbia River. 

The eruption of May 18, 1980, so far 

has been the main event in a sequence of 

volcanic activity that began on March 

20 of that year and persisted for 100 

days (to June 27) and beyond. The 

eruptive events at Mount St. Helens 

during the spring of 1980 were probably the most intensively observed, 

photographed, documented, and 

reported series of geologic events in 

history. The broad coverage of the 

events, particularly by the news media, 

resulted in many different accounts, 

from many different viewpoints, on 

many different aspects of the volcanic 

activity and its impacts. Unfortunately, these accounts do not all agree or 

reflect the facts as they are now 

known. 

The U.S. Geological Survey (USGS) 

has played a major role in the observation, interpretation, and documentation of this sequence since it began. 

As the Federal agency responsible for 

geologic and hydrologic investigations 

and geologic hazard warnings (see p. 

121), the USGS has an obligation to 

report to the Nation on these events. 

This paper is intended to provide a 

scientifically sound, general description of the events and their effects-to 

2 The First 100 Days of Mount St. Helens 

27, 1980) interspersed with occasional explosive eruptions; it might extrude enough 

lava to overflow the crater that was left 

open to the north; or the volcanic activity 

might simply stop indefinitely at any stage. 

In the meantime, the ash gradually will 

be assimilated into the soil. The streams and 

lakes that persist on the mountain flanks 

and in the devastated area will adjust to the 

new conditions of runoff and sediment 

load. Glaciers and snowfields will adapt to 

the different shape and lower altitude of the 

cone. Animals and vegetation, already returning to the devastated areas at the end of 

June 1980, will become abundant again. 

The restorative phase of the cycle, repeated 

many times before at this volcano and 

others in the Cascades, has begun once 

more. 

supply answers for the general reader, 

from the perspective of earth scientists, 

to the questions, "What happened?" 

and "What does it all mean?" 

Another major purpose of this report is to provide an accurate summary 

of the events before, during, and shortly after the devastating eruption of 

May 18, 1980, and the two lesser eruptions of May 25 and June 12. A 

chronological summary is preceded by 

a brief general discussion of Cascade 

Range volcanoes, the geologic processes involved in a volcanic sequence, 

the conditions at and near Mount St. 

Helens before the volcanic activity 

began, and the perception of and warning about the volcanic hazards. The 

chronology is followed by a short 

discussion of the continuing hazards, 

the outlook for future volcanic activity, and some implications for the 

future use and management of affected 

land and water resources. 
CAS<:ADE RANGE VOLCANOES 

Mount St. Helens is one of a group 

of high volcanic peaks that dominate 

the Cascade Range between northern 

California and southern British Columbia, Canada (fig 1.) The distribution of 

these volcanic peaks in a band that 

roughly parallels the coastline is 

typical of the so-called "Ring of Fire," a 

roughly circular array of volcanoes 

located on islands, peninsulas, and the 

margins of continents that rim the 

Pacific Ocean (Anderson, 1980). 

Even before it began erupting in 

1980, Mount St. Helens and at least six 

other volcanoes in the Cascade Range 

were known to be active-that is, to 

have erupted at least once during historical time. Few major Cascade volcanoes are known to have been inactive long enough to be considered 

extinct or incapable of further eruption. Most display some evidence of 

residual volcanic heat, such as 

fumaroles, hot springs, or hot ground 

where snow melt is unusually rapid. 

Information about the previous eruptions of some major Cascade volcanoes 

is presented in table 1. 

Dramatic eruptive activity in the 

Cascades has been rare so far in the 

20th century. Until the recent eruptions 

at Mount St. Helens, the only Cascade 

volcano that had a major eruption during this century was Lassen Peak in 

California . A series of intermittent 

eruptions of steam and volcanic ash 

beginning in May 1914 and lasting until 1921 climaxed, during the 4 days 

from May 19 to 22, 1915, in a series of 

violent events comprising small lava 

flows, massive lava-triggered mudflows, and explosive eruptions of ash. 

The most destructive of these eruptions 

included a nearly horizontal (lateral) 

blast that reached only about one-fifth 

as far as the recent Mount St. Helens 

lateral blast (Day and Allen, 1925). 

From the time when Lassen Peak 

quieted until March 1980, the only 

other known increase in activity at a 

Cascade volcano occurred at Mount 

Baker (fig. 1), when a sudden increase 

in emanations of heat, steam, and 

other gases from a previously steaming 

old crater began on March 10, 1975. 

Although new fumaroles were formed 

and minor amounts of "volcanic dust" 

and sulfur were emitted, "the greatest 

undesirable natural results" that were 

observed at Mount Baker were "an increase in local atmospheric pollution 

and a decrease in the quality of some 

local water resources" (Bortleson and 

others, 1977, p. B1). Since 1976, 

however, even those effects have subsided to levels only slightly higher than 

those that prevailed before 1975. 

Eruptions of Cascade volcanoes tend 

to be much more explosive than those 

of, for example, the well-known 

Hawaiian volcanoes. This explosive 

tendency is related to the chemical 

composition of the magma that feeds 

.A MOUNT GARIBALDI 

Vancouver 

j CANADA ____ ---

~-------U-NITED -sTATES 1 ~ A MOUNT BAKER 1 

\ ~· .._ I ~\- --- ;tO .A GLACIER PEAK Zl~ 

Spoka ne •~10 

• Seattle ~~ 

• Tacoma Moses Lake • 

• llJ 

Olympia A MOUNT RAINIER 

M~~~ETN t? .A MOU S ~ 

Vanco uver 

• • <:C".A • The Dalles 

Portland MOUNT HOOD 

Salem • 0: 

A MOUNT JEFFERSON 

THREE SISTERS ... Eu gene• • Bend 

• Ritzvi ll e 

' ------\'" 

' J 

I 

I 

I 

I 

J 

"\ I 

t 

\ 

a A NEWBERRY VOLCANO \ 

() 

CRATER LAKE 

_.!MOUNT MAZAMA) 

A MOUNT McLOUGHLIN 

o.-~ Gl\:t 0 0 z, 

(/) • Klamat h Falls __ ---

--------------·----N 

\ () 

Redding • 

50 100 MILES 

I 0 50 100 150 KILOMETERS 

FIGURE 1.-Sketch map of the Pacific Northwest and the western Pacific Ocean showing 

major Cascade Range volcanoes and other regional features. The position and alinement of the Cascade Range volcanoes result from the slow grinding together (convergence) of huge plates of the Earth's crust as new volcanic rock is added at spreading 

zones beneath the ocean (after Atwater, 1970). Arrows indicate relative movement of 

the crustal plates. These processes are further illustrated in figure 2. 

Cascade Range Volcanoes 3 
Volcano 

Mount Garibaldi __ _ 

Mount Baker ____ _ 

Glacier Peak _____ _ 

Mount Rainier ___ _ 

Summit altitude 

(ft above 

sea level) 

8, 787 --------

10,775 ----- - -

10,451 -------

14,410 -------

TABLE 1.-Activ ity of major Cascade Range volcanoes 

[Locations of volcanoes shown in fig . 1] 

Times of 

eruptions 1 

Nature or products 

of eruptions 2 

British Columbia, Canada 

About 10,000(?) ___ Lava flows; ______ _ 

years ago. fragmental 

1820(?); 1843; -----

1846; 1853-

1854; 1858; 

1859-1860; 

1863; 1870. 

About 200-300 ___ _ 

years ago; 

1,000-1,800 

years ago; 

1,800-2,800 

years ago. 

About 1820(?); ___ _ 

1841-1843(?); 

1854(?); 1879; 

1882. 

pyroclastic 

deposits. 

Washington 

Steam, __________ _ 

pyroclastic 

materials, 

mudflows. 

Mudflows; ______ _ 

pyroclastic 

flows; widespread ash 

and pumice. 

Light pumice ____ _ 

fall between 

1820 and 

1854, only 

steam emission 

and mudflows 

thereafter. 

Present thermal 

activity 

None; may be __ _ 

extinct. 

Steaming ______ _ 

fumaroles at 

flank and 

crater 

locations. 

Two hot _______ _ 

springs on 

the volcano's 

lower flanks. 

Occasional _____ _ 

steam explosions on 

upper slopes; 

many steam 

vents and 

hot rocks 

in summit 

craters. 

4 The First 100 Days of Mount St. Helens 

Remarks and references 

Volcano's core is solid 

dacite rocks. Most of 

cone comprises fragmental material that was 

deposited on surrounding ice of a continental 

glacier (Mathews, 1952; 

Harris, 1980). 

Heat emission increased 

markedly in crater area 

in 1975 and produced 

warm, acidic meltwater 

and effusive emissions 

of steam containing 

occasional traces of ash 

and sulfur dust. Activity 

had diminished somewhat by 1978 (Malone 

and Frank, 1975). 

Eruptions have characteristically produced large 

volumes of volcanic ash 

and airborne pumice 

that could endanger 

closest centers of population (Tabor and 

Crowder, 1969; Beget, 

1979). 

Largest of the Cascade volcanoes. A mudflow 

caused by steam explosions about 5,700 years 

ago was one of the 

largest known in the 

world. Expected to erupt 

again within the next 

few hundred years; 

hazards consist mainly 

of mudflows, floods, 

and fallout of tephra 

(Crandell and 

Mullineaux, 

1967). 
TABLE 1. -Activity of major Cascade Range volcanoes- Continued 

Summit altitude 

(ft above Times of Nature or products Present thermal 

Volcano sea level) eruptions 1 of eruptions 2 activity Remarks and references 

Washington - Continued 

Mount St. Helens __ 8,364 -------- Between 1600 _____ Violent __________ Strong ---- ----- Had been identified in 

(9,677 and 1700; explosions, steaming; 1978 as an especially 

before about 1800- pyroclastic occasional dangerous volcano 

May 18, 1802; 1831; flows, lava eruptions of because of its past 

1980). 1835; 1842- extrusions; steam and behavior and relatively 

1844(?); lava dome ash; occa- high frequency of 

about 1847- formation; sional pyro- eruptions (Crandell 

1854; 1857; steam and clastic flows, and Mullineaux, 1978). 

1980-7 ash; mudflows. intermittent 

(see table 2). extrusion of 

dome-forming 

lava (as of 

June 27, 

1980). 

Mount Adams ____ 12,286 - ------ No more than _____ Lava flows _______ Fumaroles Appears to consist of 

1,000 or 2,000 emitting a group of several 

years ago. steam and superimposed volcanic 

hydrogen cones. Summit crater 

sulfide in has extensive sulfur 

the crater deposits that were 

area. formerly mined 

(Hopkins, 1969.; 

Harris, 1980). 

Oregon 

Mount Hood ·-- --- 11,245 ------- 1865; 1859(7) ----- Incandescent(?) Extensive _______ Expected to erupt again, 

gaseous fumaroles possibly within the next 

plumes; small emitting few decades, but time of 

amount of steam and eruption cannot now 

pumice. other gases; be predicted. 

also hot Portland metropolitan 

200-300 years ___ Mudflows; ground on area probably will not 

ago; 1,500- pyroclastic upper south- be significantly affected 

1,800 years flows, dome western side. (Crandell, 1980; 

ago. extrusions. Harris, 1980). 

Mount Jefferson ___ 10,495 ------- Earlier than _______ Lava flows _______ None; may be ___ Future eruptions in the 

about 40,000(7) extinct. vicinity are most 

years ago. likely to be from 

smaller adjacent 

volcanoes, last active 

about 6,400-6,500 

years ago (Harris, 1980). 

Three Sisters _______ 10,085 ------- Possibly within ___ Lava extrusion ---- None known ____ A cluster of closely 

(North the last 1,000 summit area grouped, glacier-dad 

Sister); years. (South Sister). large volcanoes in an 

10,047 area of many smaller 

(Middle Flank eruptions young volcanic cones 

Sister); Less than of lava and (Williams, 1944; 

10,358 2,500(7) pyroclastic Harris, 1980). 

(South years ago. deposits 

Sister). (South Sister). 

Cascade Range Volcanoes 5 
TABLE 1. -Activity of major Cascade Range volcanoes-Continued 

Summit altitude 

(ft above Times of Nature or products Present thermal 

Volcano sea level) eruptions 1 of eruptions 2 activity Remarks and references 

Oregon-Continued 

Newberry 

Volcano 7, 985 -------- About 1,400 ______ Lava flows, _______ Hot springs _____ Actually about 40 miles 

(Paulina years ago. tephra. in eastern east of the Cascade 

Peak). crater lake. Range. A broad shield 

Volcano is volcano with a large 

promising pros- summit crater occupied 

pect for deep- by two lakes. One of the 

seated thermal region's largest volcanoes 

energy. before its explosive 

eruption and collapse 

(Williams, 1935; 

Harris, 1980). 

Crater Lake ______ 8,156 -------- At least 800- ______ Explosive -------- None ___________ From a probable altitude 

(Mount (Hillman 900 years ago. eruptions of roughly 12,000 ft, 

Mazama) Peak). that built the top of former Mount 

Wizard Island Mazama was lost to 

and two other eruption and collapse 

cones (sub- that left the present huge 

merged) on crater and the deepest 

present crater lake (1,932 ft) in North 

floor. America (Williams, 1942; 

Harris, 1980). 

About 6,600 ______ Very explosive 

years ago. eruptions proclueing regionwide ashfall 

and extensive 

pyroclastic 

flows. 

Mount ___________ 9,493 -------- About 1,500- _____ Lava flows _______ None ___________ (Harris, 1980) 

McLoughlin 2,000(7) 

years ago. 

California 

Mount Shasta _____ 14,161 ------- During about _____ Pyroclastic Two small ______ Has erupted an average 

the last 200 flows, hot fumarole of about once every 600 

years. mudflows, areas on the years during the last 

cool mudflows. summit 4,500 years. Future 

dome; one eruptions very likely 

About 700 _______ Pyroclastic has a from vents at or near 

years ago. flow. small acidic the present summit but 

hot spring. could also occur at new 

vents almost anywhere 

in the vicinity of 

Mount Shasta 

(Miller, 1980). 

6 The First 100 Days of Mount St. Helens 
Volcano 

Lassen Peak _____ _ 

TABLE 1.-Activity of major Cascade Range volcanoes-Continued 

Summit altitude 

(ft above 

sea level) 

10,457 -------

Times of 

eruptions 1 

Nature or products 

of eruptions 2 

California-Continued 

1914- 1921________ Violent explosions; 

pyroclastic 

flows; lava 

flow; steam and 

ash; mudflows; 

lava dome 

formation. 

Present thermal 

activity 

Small steaming --

fumaroles in 

summit 

craters; hot 

ground on 

northern 

flank. 

Remarks and references 

One of youngest major 

Cascade volcanoes. 

Most of the mountain is 

a single mass of dacite 

rock, emplaced in a 

relatively short time. 

Only volcano in the 48 

conterminous United 

States, besides Mount 

St. Helens, to have 

erupted during the 20th 

century (Macdonald and 

Katsura, 1965; Harris, 

1980). 

1 Nearly all dates before the mid-1800's are subject to some uncertainty, earlier dates being more uncertain than later ones. Uncertainty is indicated, in accordance with listings in referenced reports, by (7). 2 Products are those associated with the eruptions listed in the preceding column; other volcanic rocks and related deposits were involved in earlier conebuilding phases. 

• Seattle 

.... 

A GLACIER 

PEAK 

e Olympia 

A MOUNT RAINIER 

• Yakima 

+ + + + + + + + + + + + + + + + + + + + + North American plate 

~ + + + + + + + + + + + .+ + + + + + + + + + + 

FIGURE 2.-Thl~ Juan de Fuca crustal plate is slowly thrusting under the North American plate and into the hotter mantle layer, as this greatly 

simplified diagram shows. This process results in the formation of magma and probably also causes the zones of weakness in the North 

American plate through which magma rises to feed Cascade volcanoes. As the Juan de Fuca plate moves northeastward (relative to the 

mainland) at a rate of perhaps 1 inch a year, new rock material is added by volcanic extrusion in the Juan de Fuca Ridge spreading zone. 

(Data from Atwater, 1970; Srivastava and others, 1971; Riddihough, 1978.) 

Cascade Range Volcanoes 7 
A B 

c D 

:\1 GROUNO TEMPERATURE 

VISUAL OBSERVATION 

RADAR OBSERVATION 

FIGURE 3.-Typical warning signs of possible increase in volcanic activity and some ways in which they can be detected and monitored. In 

addition to the phenomena shown, slight variations in local gravity or magnetism often are related to changes in volcanic activity. None 

of these clues tells for sure whether or when a volcano will erupt. A, Earthquakes caused by magma intrusion, measured by 

seismometers; may be felt by people nearby. B, Increased heat and gas emission; may be detected from visible fuming, water-quality 

changes in streams draining from the volcano, or unusual increases in streamflow or avalanches. May be measured with ground-level 

temperature instruments, by sampling at fumaroles, by spectrometer scanning (to determine gas contents), and by infrared (heat) scanning and gas sampling from aircraft. C, Inflation caused by magma intrusion; may be measured by tiltmeters and by sequences of 

photographs, precise optical surveys, and laser-electronic distance measurements that span the period of inflation. D, Steam-driven 

(phreatic) eruptions of old rock and ash; monitored by visual observation, radar observation, photography and video recording, and by 

studies of the ejecta. · 

the volcanoes and to the amount of gas 

contained in the magma. Magma from 

the more explosive volcanoes contains 

relatively large amounts of gas and 

silicon and produces rocks such as 

andesite, dacite, or rhyolite. Magma 

from ·the less explosive volcanoes contains smaller concentrations of gas and 

silicon and produces basalt as well as 

andesite. Some Cascade volcanoes, including Mount St. Helens, have had 

nonexplosive eruptions of andesite and 

basalt, as well as explosive eruptions, 

in the past. 

The existence, position, and recurrent activity of the Cascade volcanoes 

are generally thought to be related to 

the convergence of shifting crustal 

plates (figs. 1 and 2). The Juan de Fuca 

plate and the Gorda plate are oceanic 

crustal plates that apparently are 

slowly but inexorably thrusting under 

8 The First 100 Days of Mount St. Helens 

the North American plate at a rate of 

perhaps 1 inch a year along a convergent margin that generally parallels 

the northern Padfic coast. Although 

the deep structural relationships are 

complex and not thoroughly understood, the presence of magma bodies 

beneath the Cascade Range, as well as 

the zones of structural weakness along 

which the magma rises to form the 

Cascade volcanoes, probably is related 
to the convergence of these crustal 

plates. The diagrammatic cross section 

(fig. 2) shows the relationship between 

the Juan de Fuca plate and the North 

American plate and the source of 

magma for Cascade volcanoes. 

Lava eruptions occur when magma, 

formed many miles beneath the Earth's 

surface, moves upward through zones 

of weakness in the crustal rock layers 

and is ejected from surface vents. Tilling (1977, p " 37) described the processes leading up to a typical eruption: 

". . . magma is fed from depths into a 

[magma] reservoir [analogous to air 

filling a balloon], the internal pressure 

increases, and the surface [rock] layers 

are pushed upward and outward in 

order to accommodate the swelling, or 

inflation. The net effects of such inflation include: the steepening of slope of 

the volcano's surface; increase in 

horizontal and vertical distances between points on the surface; and, in 

places, the fracturing of the [rock] 

layers stretched beyond the breaking 

point. Such rupturing of materials adjusting to magma-movement pressures 

results in earthquakes." The earthquakes, inflation, and related phenomena can be monitored by several 

methods (fig. 3), and such monitoring 

provides the best available guidance 

about the state of volcanic activity and 

associated hazards. Although this concept of internal volcanic processes was 

developed through years of research on 

volcanoes in other parts of the world, 

the foregoing description is generally 

applicable to the sequence of the 

Mount St. Htelens eruptions. 

FIGURE 4.-A, Aerial view of Mount St. 

Helens from the west in October 1977. 

The symmetry of the cone and its snow 

cover gave the volcano its nickname, the 

"Fuji of America," because of its similarity in appearance to the famous Japanese 

volcano. Mount Adams is in the 

background. (Photograph by Dee 

Molenaar, USGS.) B, View of Mount St. 

Helens from Goat Marsh Lake, 5 miles 

southwest of the peak, in 1978. 

(Photograph by Dwight R. Crandell, 

USGS.) 

MOUNT ST. HELENS 

BEFORE 1980 

Mount St. Helens was known as "the 

Fuji of America" because its symmetrical beauty was similar to that of the 

famous Japanese volcano (fig. 4A). 

The graceful cone top, whose glistening cap of perennial snow and ice 

dazzled the viewer, is now largely 

gone. On May 18, 1980, the missing 

mountaintop was transformed in a few 

hours into the extensive volcanic ash 

that blanketed much of the Northwestern United States and into various 

other deposits closer to the mountain. 

Even before its recent loss of height, 

Mount St. Helens was not one of the 

highest peaks in the Cascade Range. Its 

A 
Base fro m U.S. Geological Survey 

1:62,500 M ount St. Helen s, 1958 

0 2 3 MILES ------~----~--,-------~-L------,-----~ 

0 2 3 4 KILOMETERS 

CONTOUR INTERVAL 80 FEET 

FIGURE 5.-Map of pre-1980 Mount St. Helens showing named features referred to in the text. The shaded area surrounding the peak 

indicates the approximate extent of timber in 1958, much of which had been logged by 1980. The dashed line encloses the part of the 

north-side slope that became the unstable bulge area. By 1980, Timberline Campground had been closed and replaced by a public viewpoint about a quarter of a mile to the east (see figs. 7 and 18). 

10 The First 100 Days of Mount St. Helens 
summit altitude of 9,677 feet made it 

only the fifth highest peak in Washington (table 1). It stood out handsomely, 

however, from surrounding hills because it rose thousands of feet above 

them and had a perennial cover of ice 

and snow (fig. 48). The peak rose more 

than 5,000 fe,et above its base, where 

the lower flanks merge with adjacent 

ridges. The mountain is about 6 miles 

across at the base, which is at an altitude of about 4,400 feet on the northeastern side and about 4,000 feet elsewhere. At the preeruption timberline 

(upper limit of trees), the width of the 

cone was about 4 miles (fig. 5). 

Mount St. Helens is 34 miles almost 

due west of Mount Adams, which is in 

the eastern part of the Cascade Range 

(figs. 1 and 4A). These "sister and 

brother" volcanic mountains are each 

about 50 miles from Mount Rainier, 

the giant of Cascade volcanoes. Mount 

Hood, the nearest major volcanic peak 

in Oregon, is about 60 miles southeast 

of Mount St. Helens. 

Mount St. Helens was named for 

British diplomat Alleyne Fitzherbert 

(1753-1839), whose title was Baron St. 

Helens. The mountain was named by 

Commander George Vancouver and 

the officers of H.M.S. Discovery while 

they were surveying the northern 

Pacific coast from 1792 to 1794. 

Mount St. Helens was recognized as 

a volcano at least as early as 1835; the 

first geologist apparently viewed the 

volcano 6 yE!ars later. James Dwight 

Dana of Yale University, while sailing 

with the Charles Wilkes U.S. Exploring 

Expedition, saw the peak (then quiescent) from off the mouth of the Columbia River in 1841. Another member of 

the expedition later described "cellular 

basaltic lavas" at the mountain's base. 

Although :Mount St. Helens is in 

Skamania County, the best access 

routes to tht~ mountain run through 

Cowlitz County on the west. State 

Route 504 (fig. 6), which formerly 

ended at Timberline Viewpoint (fig. 7) 

. 2.6 miles from the summit, connects 

with the heavily traveled Interstate 

Highway 5 about 34 miles to the west. 

OREGON 

Base from U.S. Geological Survey 

State base map, 1:500,000 unedited 

advance print 1981 

WASHINGTON 

I 

10 

I 

10 MILES 

I 

15 KILOMETERS 

FIGURE 6.-Sketch map showing selected streams, population centers, and other features in 

relation to Mount St. Helens. 

That major north-south highway skirts 

the low-lying cities of Castle Rock, 

Longview, and Kelso along the Cowlitz 

River (fig. 6) and passes through the 

Vancouver, Wash.-Portland, Oreg., 

metropolitan area less than 50 miles to 

the southwest. The community nearest 

the volcano is Cougar, which is in the 

Lewis River valley about 11 miles 

south-southwest of the peak. Gifford 

Pinchot National Forest surrounds 

Mount St. Helens, but some land on 

the mountain and much of the area 

adjacent to the national forest are 

Washington State lands or are privately owned. 

Mount St. Helens Before 1980 11 
Base from U.S. Geological Survey 

1:100,000 Mt. St. Helens, Washington 

April 1980, Special Edition 

0 

0 

2 3 MILES 

1 2 3 4 KILOMETERS 

CONTOUR INTERVAL 50 METERS 

FIGURE 7.-Map showing Mount St. Helens and vicinity before the 1980 eruptions. The heavy line indicates the area shown in figure 5 . 

12 The First 100 Days of Mount St. Helens 
Streams that head on the volcano 

enter three main river systems-the 

Toutle River on the north and northwest, the Kalama River on the west, 

and the Lewis River on the south and 

east (fig. 6). The streams are fed by 

abundant rain and snow that dump an 

average of about 140 inches of water 

on Mount St. Helens a year, according 

to National 'Neather Service data. The 

Lewis River is impounded by three 

dams for hydropower generation. The 

southern and eastern sides of the 

volcano drain into an upstream impoundment, the Swift Reservoir, 

which is directly south of the volcano. 

The streams that drain the mountain 

also are som,ewhat regulated naturally 

by the mountain's perennial snowfields 

and glaciers (blue-contoured white 

areas on fig. 7; see names on fig. 5). 

Water is stored as snow and ice during 

the cool, wet periods and is released as 

melt. water during warmer, drier periods. 

Water-related recreation has been 

one of the major activities in the area. 

All three reservoirs on the Lewis River 

(fig. 6) have been used extensively for 

recreation, as was Spirit Lake (fig. 7) 

before 1980. Before the eruption, Spirit 

Lake was impounded in the North Fork 

Toutle River valley by a natural dam 

formed chiefly of deposits from one or 

more ancient mudflows (table 2). The 

principle resource of the region is 

timber, and many areas near the volcano had been logged recently and 

were still being logged at the beginning 

of the 1980 eruptive activity. 

Mount St. Helens, like most other 

Cascade volcanoes, is a great cone of 

rubble consisting of lava rock interlayered with pyroclastic and other 

deposits. Volcanic cones of this internal structure are called composite 

cones or stratovolcanoes. Mount St. 

Helens includes layers of basalt and 

andesite through which several domes 

of dacite lava have erupted. The largest 

of the dacite domes formed the 

previous summit; another formed Goat 

Rocks on the northern flank. Figure 8 is 

a diagrammatic section through 

preemption Mount St. Helens showing 

the inferred relationship of the former 

summit dome to the lava layers and the 

interbedded rubble. Information about 

previous eruptions is given in table 2. 

TABLE 2.-Summary of volcanic ev ents and deposits formed at Mount St. Helens during the period of about 3,000 years before the 1980 eruptions (after Crandell and Mullineaux, 1978; Hopson and Melson, 1980) 

[IEruption dates in the 1800's generally agree with eyewitness accounts summarized by Harris (1980). All dates A.D. unless indicated otherwise] 

Date 

1857 ---------------- -----------------

About 1847 to 1854 - --- ----------------

1842 to 1844(1') --------------- ---------

1831 and 1835 --------------- --------- -

About 1800 to 1~02 --------------------

Between 1600 and 1700 -----------------

About 1500 to 1600 --------------------

800 ( ± 200 years) ----------------------

300 ( ± 200 years) ----- - ----- - ----------

50 ( ± 100 years) - --------- -------------

Between abou!t 700 and 100(7) B.C. ______ _ 

Between 1200 and 700 B. C. ____________ _ 

Event or type of deposit 

Last-reported eruptions before 1980; no resultant deposit has been recognized 

Steam and ash; no recognizable deposits 

Dacite pumice (extending northeast of volcano); followed by dome of dacite 

(Goat Rocks), glowing avalanches, hot and cool mudflows, and andesite lava 

flows (north-northwestern and south-southwestern flanks). 

Steam and ash; no recognizable deposits 

Dacite pumice 

Voluminous flows of andesite lava from flank vents on all four sides of the 

mountain; pyroclastic flows on northern and southwestern sides; mudflows 

from summit area. 

Thick, extensive dacite pumice; at least three pyroclastic flows down Kalama 

River valley; andesite lava flows; hot and cool mudflows, some reaching Spirit 

Lake; growth of Summit Dome (dacite), followed by glowing avalanches on 

south-eastern, southern, southwestern, and west-northwestern flanks. 

Strong flank explosion, laterally directed on the northeast, followed by the 

growth of a dacite dome (Sugar Bowl). 

Pyroclastic flows; extrusion of dacite dome (East Dome); lava flows 

Voluminous basalt lava flows on southern and southwestern sides 

Pyroclastic flows; lava flows; mudflows extending from southeastern and southern sides of mountain. 

Sequence of extensive pyroclastic flows and mudflows, some reaching Spirit Lake 

and into North Fork Toutle River valley; several mudflows reached the present 

site of Castle Rock; dacite dome formed . 

Mount St. Helens Before 1980 13 
~Lava rock 

EXPLANATION 

~ Pyroclastic and 

L___:_j mudflow deposits 

c::::J Older rock 

FIGURE 8.-Mount St. Helens is a composite volcano, or stratovolcano, built of alternating 

layers of lava rock and pyroclastic debris. This cross section of the pre-1980 volcano 

shows the generalized relationships between the layers of the volcano's cone, the lava 

dome (emplaced about 1600 A.D.) that formed the summit, and the north-flank dome 

called Goat Rocks, which formed during the 1840's (table 2). For simplicity, the magma 

chamber as shown here is much shallower, in relation to the mountain's height, than it 

actually is thought to be. 

PERCEPTION AND WARNING 

OF THE HAZARDS 

The death toll from the May 18 eruption undoubtedly was greatly lessened 

by the timely dissemination of reliable 

scientific information about the volcano and the hazards that it presented 

and by public and private use of that 

information in response to those 

hazards. The volcanic hazard information was derived from geologic studies 

of Mount St. Helens and other Cascade 

volcanoes and from monitoring the 

volcano visually and by various 

geophysical methods. This information 

was widely spread in written reports 

and news releases, briefings of public 

officials and news reporters, replies to 

thousands of individual telephone inquiries, and the formal announcement 

of a "Hazards Watch" and subsequent 

updates by the USGS. Responsible officials reacted to that information by 

taking steps that significantly reduced 

public exposure to the risks. These 

steps included restricting and eventually prohibiting access to lands identified 

as being within zones of relatively high 

risk and lowering the water level in 

Swift Reservoir (fig. 6). 

Although historical accounts of 

eruptions during the 1800's (table 2) 

suggested the possibility of renewed 

volcanic activity at Mount St. Helens, 

the foundation of scientific information that allowed. realistic evaluation of 

the hazards was laid over several decades. Because the volcano has long 

been a favorite of climbers and naturalists, the two areas of fumaroles and 

warm ground known before 1980 had 

been documented as early as 1939 in a 

report on the flora of the mountain 

(Lawrence, 1939). The first systematic 

14 The First 100 Days of Mount St. Helens 

geologic investigation of Mount St. 

Helens, begun in the 1930's, was a 

reconnaissance-type study by Verhoogan (1937). The report was concerned mainly with the character of the 

rocks that make up the volcanic cone 

and underlie adjacent areas. Two of 

Verhoogen's statements were especially 

pertinent to the recent activity of the 

volcano. According to Verhoogen 

(1937, p. 268), "The activity of the 

volcano seems to have continued without interruption until very recent 

times. Many [lava] flows cannot be 

more than a few hundred years old, as 

evidenced by the vegetation." Further 

on, he said, "The writer has been told 

that, until a few years ago, climbers on 

Mount St. Helens could witness solfataric action [emission of sulfurous 

gases] and hot springs. Today [1937] 

the mountain is completely dormant." 

Later geologic studies verified the 

relative youthfulness of volcanic deposits from Mount St. Helens, and 

geologists most familiar with the Cascade volcanoes gradually became 

aware of the unusual potential hazards 

posed by the volcano. The geologic 

record of past eruptions was sufficiently well documented by 1975 to enable 

USGS geologists Dwight Crandell and 

Donal Mullineaux and geochemist 

Meyer Rubin to warn, in an article in 

Science magazine, that ". . . an eruption [of Mount St. Helens] is likely 

within the next hundred years, possibly before the end of this century" 

(Crandell and others, 1975, p. 441). 

That judgment was verified in a 

more comprehensive assessment of the 

volcanic hazards of Mount St. Helens 

produced by the USGS in 1978 as part 

of a broad program for the systematic 

evaluation of volcanic hazards (see section on "Geologic Hazard Responsibilities"). The results of that assessment 

were published as USGS Bulletin 

1383-C, Potential Hazards from Future Eruptions of Mount St. Helens 

Volcano, Washington (Crandell and 

Mullineaux, 1978). The report summarized the mountain's volcanic 

history since the year 2500 B.C. and 
showed the extent of the deposits 

resulting from those events. On the 

basis of that reconstructed history, as 

well as prevailing land uses and 

developments near the volcano, Crandell and Mullineaux described the anticipated effects of future eruptions and 

included maps showing the hazard 

zones for various kinds of future eruption results (ashfalls, lava flows, 

pyroclastic flows, mudflows, and 

floods). The Crandell-Mullineaux report proved to be remarkably prophetic, differing from the actual eruptive effects of May 18, 1980, mainly in not 

anticipating such an extensive and 

devastating lateral blast. Among the 

accurate forecasts made Crandell and 

Mullineaux (1978, p. Cl) was" ... we 

believe [Mount St. Helens] to be an 

especially dangerous volcano because 

of its past behavior and relatively high 

frequency of eruptions during the last 

4,500 years." Another (Crandell and 

Mullineaux, 1978, p. C25) was "If [a 

typical eruptive] sequence is followed 

during future eruptions, the greatest 

potential danger will exist at or soon 

after the onset of volcanic activity. " 

Information about the flow and 

water quality of streams draining the 

volcano and other streams likely to be 

affected by eruptions was available 

from data collected over several decades by the USGS in cooperation with 

other agencies and utilities. The stream 

data were collected primarily for 

water-resource assessment by the 

USGS and for water management by 

other cooperating agencies; the data 

also, however, provided important 

background information about 

preemption stream conditions, including the flood-carrying capacity of 

the stream channels. 

Under the special responsibilities 

given to the USGS in the Disaster 

Relief Act of 197 4 to warn of geologic 

hazards (p. 121 ), the Crandell and 

Mullineaux (1978) report and a letter 

discussing its hazard implications were 

disseminated as a "Notice of Potential 

Hazard" in December 1978. The report 

and letter were sent to appropriate 

Federal and Washington State officials 

and selected county and local agencies 

in southwestern Washington. Also, 

USGS scientists explained the hazard 

implications of the report during a 

meeting with key Federal and State officials in Olympia, Wash., on January 

8, 1979. 

While the assessment of volcanic 

hazards was being prepared, the volcano was already being monitored to 

detect early signs of an impending 

eruption. No one knew what kinds of 

monitoring techniques would provide 

the most reliable warning, however, 

because knowledge about the behavior 

of Cascade volcanoes in general was 

limited and because Mount St. Helens 

had not been active recently. University and USGS studies in the 1970's had 

monitored Mount St. Helens intermittently by means of three instrumental 

methods: (1) seismometers that could 

detect earthquakes caused by the 

movement of molten rock into a volcano, (2) precise ground-surface 

measurements that could detect swelling of the volcano, and (3) aerial infrared surveys and surface-temperature 

measurements of two "hot spots" high 

on the mountain to detect any changes 

in heat emission from the volcano (fig. 

3). The volcano also was one of many 

glacier-dad mountains that were photographed routinely from the air to 

detect changes in snow and ice as part 

of a USGS glaciology research project. 

At the beginning of March 1980, the 

only instrument directly monitoring 

Mount St. Helens was a seismometer 

on the western flank of the volcano, 

from which a record of seismic shaking 

was automatically transmitted by 

radio (telemetered) to seismic recorders 

at the University of Washington in 

Seattle. That seismometer was one of 

about 100 seismic instruments deployed in a network throughout 

western and central Washington by the 

university's Geophysics Program in 

cooperation with the USGS. 

That seismometer was one of the 

first instruments to warn, by registering earthquakes on March 20 and 

thereafter, of impending eruptive activity. When increasing seismic activity 

suggested the possibility of an impending eruption, University of Washington and USGS scientists at Seattle 

notified other USGS volcano experts 

throughout the country and the USGS 

Hazards Information Coordinator in 

Reston, Va. Aerial observations were 

begun as soon as possible. Within a 

few days, additional geophysical instruments were brought into use, including more seismometers, precision 

tiltmeters to measure slight changes in 

the slope of the volcano's flanks, and 

gravity meters and magnetometers to 

detect changes in the character of the 

subsurface rocks. Photographic and 

heat-monitoring (thermal infrared) 

surveys from the air were resumed as 

weather permitted. 

After the first eruption on March 27, 

scientists and technicians intensified 

their monitoring activities and began 

sampling and analyzing volcanic gases, 

volcanic ash, and snow and melt water 

from and near the volcano. In the 

following few weeks, they began using 

laser distance-measuring instruments 

and other precise surveying equipment 

to detect small shifts of the volcano's 

surface. They also expanded an existing network of hydrologic measuring sites to monitor changes in streamflow and water quality on streams 

draining Mount St. Helens and streams 

likely to be affected by volcanic ash. 

These additional stream-monitor sites 

were intended to help detect (1) any 

unusual changes in flow, such as sudden increases in melt water that might 

result from rapid heating of the rocks 

under ice and snow, and (2) changes in 

water quality that might be caused by 

volcanic gases dissolving in the melt 

water or by materials leached from 

volcanic ash. 

As scientists and information 

specialists assembled, first in response 

to the forewarning earthquakes and 

then because of the early eruptive 

events, scientists already on the 

scene at the University of Washington 

and in Vancouver, Wash., provided 

Perception and Warning of the Hazards 15 
most of the information that was 

available to local agency officials, the 

news media, and the general public. In 

Vancouver, initial information releases 

were coordinated by the U.S. Forest 

Service at its administrative headquarters for the Gifford Pinchot National Forest, where an emergency operations center was set up to provide 

incoming scientists with work space, 

communications facilities, and other 

logistical support until such support 

could be arranged otherwise. This action greatly assisted the newly 

launched scientific effort and also was 

instrumental in providing anxious reporters, officials, and the public with 

the necessary hazard warnings and 

authoritative information. The USGS 

also set up its own temporary headquarters in Vancouver under the general guidance of Mullineaux, in close 

coordination with the Forest Service. 

Volcanic hazards analysis and interagency coordination were directed by 

Crandell, and volcanic monitoring and 

observational investigations were 

supervised by Robert L. Christiansen. 

In the meantime, USGS hydrologists, glaciologists, and technicians 

operated their stepped-up program of 

water-related monitoring and data collection from their normal headquarters 

at Tacoma, Wash., and Portland, 

Oreg. Studies of Mount St. Helens 

glaciers were largely directed by Mark 

F. Meier in Tacoma. Stream surveillance and water-quality monitoring 

were supervised by Charles R. Collier 

in Tacoma and by Stanley F. Kapustka 

in Portland. 

After President Carter declared on 

May 21 that the State of Washington 

was a disaster area, the Federal Emergency Management Agency assumed 

responsibility for coordinating the 

release of information and hazard 

warnings at a temporary emergencyoperations center in Vancouver. Intensive coverage of the volcanic events by 

the news media, as well as actions by 

State and local officials based on coordinated information released by 

scientists, provided most of the warnings and guidance for local residents. 

CHRONOLOGY OF THE FIRST 

100 DAYS 

The following chronology begins 

with the first telltale earthquake on 

March 20 and ends during a domebuilding phase on June 27. This interval gave rise to countless fascinating 

stories about the volcanic events and 

the human responses to those events. 

This chronology emphasizes the sequence of geologic occurrences and 

processes as well as the hazardwarning aspects of that historic period, 

but it also describes other incidents 

that relate public and agency responses 

to the volcanic events. 

This chronology has been written as 

if it were an evening journal recounting 

the events of the day-a method traditionally used by field scientists. Indeed, 

the major sources for the account that 

follows were the daily reports of field 

scientists and other observers who 

were on the scene as the Mount St. 

Helens story unfolded. 

By far, the most important event of 

this period was the devastating eruption of May 18, hereafter referred to as 

"E Day." For the convenience of the 

·reader, all dates in the chronology are 

referred to that day. 

Unusual Earthquakes 

Begin 

Thursday, March 20, 1980 

E Day Minus 59 

Seismographs at the University of 

Washington in Seattle registered at 

3:37p.m. today the first sizable earthquake to shake Mount St. Helens since 

recording devices were installed in 

1972. The quake was distinctly felt 

near the volcano. It measured 

magnitude 4.1 on the Richter scale, 

was followed by many aftershocks, 

and originated at shallow depth from a 

point immediately northwest of the 

summit of Mount St. Helens. That 

quake and the others that followed 

were unlike any earthquake sequence 

ever recorded in the Northwest. 

The initial quake differed from other 

such earthquakes in the Cascade Range 

because of its unusually shallow origin 

(how shallow is yet unknown) and its 

many aftershocks. A telephone call 

from the University of Washington 

seismology center notified the USGS 

regional office in Menlo Park, Calif., 

of the earthquake and the unusual persistence of its aftershocks. 

Only one telemetered seismic station 

(linked to university recorders by 

radio) is operating in the area, but the 

decision was made to install additional 

seismometers immediately. Coincidentally, four of the instruments already in 

shipment to Seattle arrived this evening. 

Friday, March 21 

E Day Minus 58 

Evidence of aftershocks persisted 

this morning in the record being transmitted by the Mount St. Helens seismic 

station, and telephone advisories between the Forest Service, USGS, and 

the University of Washington were 

stepped up. Forest Service officials in 

Vancouver telephoned a report of 

yesterday's earthquake to personnel of 

the USGS Volcanic Hazards Project in 

Denver, Colo. Scientists at the University of Washington seismology center 

contacted the Forest Service in Vancouver for assistance in locating additional seismic stations (because of 

snowy conditions) and were told that 

the earthquakes had caused large avalanches yesterday on Mount St. 

Helens. The seismology center staff 

also notified the USGS Menlo Park office that yesterday's main shock had a 

very shallow source, which was indicated by the reported avalanches, the 

character of the recorded shock waves, 

and the fact that the earthquake was so 

strongly felt nearby. 

Working together, USGS and University of Washington scientists in16 The First 100 Days of Mount St. Helens 
stalled four additional seismic stations 

near Mount St. Helens. Three of these 

stations (one each a few miles east, 

north, and south of the volcano) are 

designed to begin recording as soon as 

they detect a shock and to continue operating unattended for 5 days unless 

they are reset. The other station, about 

20 miles to the northeast, will automatically transmit electronic signals of 

earth movements to the seismology 

center in Seattle. 

Seismologists expect that the additional instruments will help to define 

the geologic processes that caused the 

shocks. Those processes, they believe, 

involve fairly ordinary crustal movement along subsurface faults. 

Saturday, March 22 

E Day Minus 57 

A second earthquake greater than 

magnitude 4 occurred today, together 

with many smaller ones similar to 

those occurring on Thursday. Seismologists decided that this event was not a 

single large quake with smaller aftershocks but an earthquake swarm consisting of many separate events. 

Scientists at the University of Washington advised the Forest Service's avalanche warning center in Seattle (as they 

advised the Vancouver office yesterday) that the possibility of continuing 

earthquake-triggered avalanches on 

Mount St. Helens was high. A field trip 

has been arranged for tomorrow to collect records from the 5-day recording 

instruments in the hope of determining 

a more precise location for today' s 

major quake. 

Sunday, March 23 

E Day Minus 56 

Visits to the seismic stations near 

Mount St. Helens today were frustrating. All three recording seismographs 

installed on Friday were not working 

properly, two because of bad batteries. 

Thus, no records are available from 

them to help pinpoint the source of 

yesterday's large shock. 

Meanwhile, seismic data being received at Seattle show a sharp increase 

in earthquake activity. Five quakes 

greater than magnitude 3 were recorded today, including (shortly after 8 

p.m. tonight) the third one greater than 

magnitude 4. Seismologists in Seattle 

have decided that this earthquake sequence may be a forerunner of volcanic activity, and they will alert Denver 

Volcanic Hazards Project personnel 

tomorrow morning. 

Monday, March 24 

E Day Minus 55 

Observers flying over the volcano 

today were unable to detect obvious 

signs of increased volcanic or new thermal activity, but they did note a 

number of snow avalanches triggered 

by the continuing earthquakes. 

Seismic activity continues to increase. Ten earthquakes greater than 

magnitude 3 were recorded from the 

Mount St. Helens area; 4 were greater 

than magnitude 4, and the strongest 

was magnitude 4.7. The University of 

Washington seismology center is now 

being staffed 24 hours a day. 

Seismologists added another seismic 

station to the USGS-University of 

Washington network monitoring the 

volcano, reinstalled one of the failed 

recorders, and made plans for future 

additions. They also advised USGS 

Volcanic Hazards Project personnel in 

Denver, as well as the USGS regional 

headquarters in Menlo Park, Calif., 

and the Forest Service Vancouver office, that a "tremendous increase in 

seismicity" has been observed and that 

the seismic records are indicating a 

volcanic earthquake sequence. The 

University of Washington and the 

Forest Service immediately began asking the public to stay away from 

Mount St. Helens and Spirit Lake. The 

USGS Hazards Information Coordinator in Reston, Va., was advised that 

the earthquakes near Mount St. Helens 

were showing a "classic preemption 

pattern," a behavior seen previously at 

Japanese volcanoes. 

David Johnston, a USGS volcanologist from Menlo Park, Calif., who was 

vacationing in the Seattle area, visited 

the seismology center and stayed on to 

help handle the rapidly accumulating 

seismic data. 

Tuesday, March 25 

E Day Minus 54 

Seismic activity increased greatly 

again today, when as many as 5 earthquakes of magnitude 4 or greater were 

recorded in 1 hour (22 during one 

8-hour period). At this rate, recorder 

traces of earthquakes even as large as 

magnitude 3. 5 are buried in the continuations of traces of previous quakes. 

This sharp increase in the number 

and magnitude of earthquakes has 

prompted USGS geologist Mullineaux 

to leave Denver for Forest Service 

headquarters for the Gifford Pinchot 

National Forest in Vancouver, where 

an interagency meeting about Mount 

St. Helens has been scheduled for 

tomorrow. Mullineaux will stay on to 

direct the USGS study of the volcano. 

The Forest Service announced that 

national forest areas on the mountain 

above the tree line (or timberline; fig 5) 

have been closed, along with the information center at Spirit Lake, and 

warned residents near the mountain of 

the danger of earthquake-induced avalanches. The closed area ranges from 

less than 2 miles to nearly 4 miles from 

the summit. The Skamania County 

Sheriff's office closed the main highway into the north-side area, State 

Route 504 (fig. 7), at a point even farther away-about 5 miles northwest of 

the peak. Many national forest roads 

also were closed. 

News reporters and photographers 

have flocked to the mountain. The 

Federal Aviation Administration has 

imposed special flight restrictions near 

the volcano because of the number of 

aircraft carrying scientists, reporters, 

and other observers for a close look. 

Bud Kimball, a commercial aerial 

photographer, reported to USGS scientists in Tacoma that he had photogaphed a large crack in the snow and 

ice across the top of Mount St. Helens. 

Chronology of the First 100 Days 17 
Wednesday 1 March 26 

E Day Minus 53 

Extensive cloud cover hid the mountain from view all day. 

The University of Washington seismology center this evening registered 

the 100th quake of magnitude 3.5 or 

larger in the Mount St. Helens area 

since March 20. Today, 7 earthquakes 

of magnitude 4.0 or greater occurred-many less than the 25 recorded yesterday. Most of these quakes 

originated at relatively shallow depths 

of about 3 miles or less below the land 

surface. 

Additional recording equipment was 

installed at the seismology center to 

handle the saturation of seismic data 

from the telemetered stations. Data 

processing and attempts to locate 

earthquakes' origins are now roundthe-dock efforts. 

A meeting of Federal, State, and 

county emergency-services officials 

was held today in Vancouver. USGS 

scientists explained their interpretations of the seismic events and potential hazards. An emergency coordination center was set up by the Forest 

Service at its Vancouver headquarters. 

In spite of the earthquakes and news 

reports, some residents do not believe 

that an eruption is possible. Said one, 

according to the Associated Press, "It's 

just . . . cooked up by the Federal 

forestry service for them environmentalists to delay a big development of 

the Spirit Lake recreation area. That's 

my opinion." 

Ash Eruptions Begin 

Thursday 1 March 27 

E Day Minus 52 

USGS officials today issued a formal 

"Hazards Watch" announcement to 

more than 300 State and Federal officials, representatives of other agencies, and the local congressional delegation. 

At 11:20 a.m., an observer in an 

Army National Guard reconnaissance 

airplane reported seeing a hole in the 

icecap on the mountain near the summit and a gray streak (presumably ash) 

extending southeast from the hole. No 

emissions from the hole were reported 

at that time. Then, at about 12:30 

p.m., people near the volcano heard a 

loud boom. This boom probably 

marked the first sighted eruption, 

which took place during cloudy 

weather. Mike Beard, a reporter from a 

Portland radio station, was flying over 

the cloud-shrouded mountain and apparently was the first to report seeing 

the eruption. He is quoted as saying 

that he " ... saw ash and smoke 

spewing out, a little like smoke out of a 

chimney. It was not explosive .... " 

At 2:00 p.m., the University of 

Washington seismology center recorded a magnitude 4.7 earthquake, the 

second strongest to date. The quake 

was one of 57 during the day to register 

magnitude 3.5 or greater. (Earthquakes 

have become so common in the Mount 

St. Helens area that a half dozen 

quakes greater than magnitude 4 are 

considered normal for a day.) After 

this magnitude 4.7 shock, the eruption, 

as described by airborne observers, 

was a thick black plume rising about 

7,000 feet above the volcano. 

Observers flying over the mountain 

shortly afterward saw a crater about 

200 to 250 feet wide near the summit 

(fig. 9). They also noted that the ice, 

snow, and rocks around the crater 

were deformed and that volcanic ash 

had darkened the snow in a band that 

extended across the crater and down 

the cone's southeastern slope. Two 

crack systems trending east-west were 

seen extending across the peak. The 

southernmost crack is about 1 mile 

long; it turns north on both the eastern 

and western sides of the summit and 

reaches short distances down the 

northeastern and northwestern flanks 

of the mountain. 

Within hours of the initial eruption, 

hundreds of people were evacuated 

from logging camps, scattered homes, 

and public facilities in the area. 

Emergency-services officials advised 

residents within a 15-mile radius of the 

18 The First 100 Days of Mount St. Helens 

mountain to leave. Forest Service 

employees and their families left the 

ranger station at the head of Swift 

Reservoir. About 300 loggers moved 

out of three Weyerhaeuser Company 

logging camps near the volcano, as did 

20 people from the State fish hatchery 

on the North Fork Toutle River, about 

30 miles downstream from the volcano. Skamania County Sheriff's deputies moved 45 people, mostly newsmen 

and scientists, from the Spirit Lake 

area. Cowlitz County law-enforcement 

officers evacuated people farther 

downstream along the Toutle River. 

Deputies from both counties set up 

roadblocks on several main routes to 

keep out the curious. The Washington 

Department of Emergency Services 

distributed to residents of the town of 

Cougar information sheets suggesting 

that they "pack an overnight bag" and 

be ready to move quickly. 

One longtime resident, Harry Truman, proprietor of the Mount St. 

Helens Lodge at the southwestern end 

of Spirit Lake, refused to leave in spite 

of strong urging to do so. 

The evacuations were spurred by 

two major concerns. One is that the 

cracks across the summit resulted from 

a slumping of the ice field on the upper 

northern flank of the volcano, which 

may increase the danger of major avalanches. The other is that widespread 

flooding and mudflows might result if 

heat from the volcano melts the mountain's mantle of snow and ice. By evening, however, USGS hydrologists 

reported that none of the streams that 

drain the volcano's slopes was rising. 

More scientists have been arriving at 

the Vancouver coordination center to 

study phenomena such as earthquake 

activity, deformation of the volcano 

surface, composition of volcanic gas 

and ash, heat emissions, and changes 

in the quantity and quality of melt 

water (fig. 3). 

Friday 1 March 28 

E Day Minus 51 

Another explosive eruption began 

about 3:00 a.m. today and lasted near-
FIGURE 9.-0n March 27, 1980, observers saw Mount St. Helens erupt for the first time in 123 years. The eruption, which was preceded by a 

loud "boom, " left a single crater, 200 to 250 feet across, in the snow and ice that capped the volcano's cone. The snow around the crater 

was coated with volcanic ash, a material that was to become all too familiar to many residents of the Northwest. The view here is from 

the north. (Photograph by Austin Post, USGS, March 27, 1980.) 

ly 2 hours. Although observations 

were hampered by bad weather and 

darkness, a cloud of ash and steam was 

seen by airborne observers to rise 

"more than a mile" above the volcano, 

and an ash cloud cascaded slowly 

down its eastern flank. 

By dusk, at least a dozen other eruptions lasting from a few minutes to 

nearly an hour had occurred. Columns 

of steam and ash at times reached nearly 10,000 feet above the volcano and 

drifted eastward. An eruption just 

before sunset threw out not only ash 

but also rocks that ranged in size from 

a few inches to about 3 feet across. A 

short time later, volcanic ash was falling in a wide swath east of the volcano. 

It was reported as far away as Trout 

Lake, about 35 miles to the southeast. 

Several mud-darkened avalanches of 

snow and ice moved down the eastern 

flank of the mountain; a few extended 

down to the 6,400-foot level. Because 

of their dark color, some observers 

mistook them for lava flows or mudflows, an error that added to concerns 

about flood hazards in the valleys of 

streams draining the mountain. 

Earthquake activity remains about 

the same. Eight events of magnitude 4 

or greater took place today; the 

strongest earthquake to date, which 

occurred shortly after midnight this 

morning, registered 4.9 in Seattle. 

Geophysicists report that the earthquakes are centered beneath the volcano at a depth of less than 1 mile. 

Scientists from the University of 

Washington Cloud Physics Research 

Group flew over the volcano to collect 

samples of the emanating gases. They 

found that sulfur dioxide, which is 

associated with high temperatures, was 

the main sulfur gas present. This discovery was the first indication that a 

high-temperature source inside the 

mountain is releasing gas during eruptions. The presence of sulfur dioxide in 

the gases is of special interest because 

its content is usually low in geothermal 

steam but relatively high in gases 

emanating from magma. 

Despite the bad weather and frequent eruptions, scientists in a 

helicopter flew to the 4, 000-foot level 

of the volcano to collect ash samples 

for analysis to determine whether the 

volcanic ash was coming from new 

magma or from pulverized old rock. 

Chronology of the First 100 Days 19 
University of Puget Sound scientists 

began making gravity measurements at 

sites near the volcano to detect any 

changes that might be related to intrusion of magma. 

USGS water specialists began collecting water-quality data systematically from sites around Mount 

St. Helens and in the direction of 

prevailing winds from the volcano. 

They also began installing additional 

water-quality monitors near the 

volcano. 

The Pacific Power and Light Company has been releasing water from its 

Swift Reservoir to two reservoirs 

downstream; the water level in the 

Swift consequently was about 20 feet 

below capacity today. The objective 

was to create storage space to accommodate rapid snowmelt runoff or mudflows that might be caused by eruptions. A USGS report (Crandell and 

Mullineaux, 1978) had pointed out that 

Swift Reservoir, the closest one to the 

volcano, was both a danger and a 

margin of safety-a danger if floods 

were to overtop it, a margin of safety if 

it could be used to hold back sudden 

floods or mudflows. 

Sightseers jammed possible evacuation routes with their vehicles and tried 

to evade roadblocks to get closer views 

of the volcano. Officials of the Washington Department of Emergency Services have implored curiosity seekers to 

keep away from potential danger 

areas. 

Yesterday, volcanologist Johnston 

left his volunteer duties at the University of Washington seismology center in 

Seattle for Vancouver to join the field 

studies at the volcano. In an interview 

today with reporters at Timberline 

Viewpoint, he likened the mountain to 

dynamite with a lit fuse; " ... but you 

don't know how long the fuse is," he 

said. 

Mountaintop Cracks 

and Craters Grow 

Saturday, March 29 

E Day Minus 50 

The weather cleared today, and airborne observers noted a second, larger 

crater west of the first (fig. 10). 

Sporadic eruptions of steam and ash 

were now coming mainly from this 

new crater. 

Clouds of erupted ash and steam 

that swept slowly down the mountain 

(fig. 11) sometimes were accompanied 

by lightning flashes, some of them 2 

miles long. Scientists speculated that 

the ground-hugging lightning bolts 

were caused by rock particles in the ash 

cloud rubbing together to produce electrostatic discharges, much as static 

electricity is sometimes generated by 

walking over a rug. 

The first USGS analyses of volcanic 

ash showed that the ash is composed of 

pulverized old rock propelled into the 

air by steam eruptions. There was no 

evidence of "juvenile" rock material 

(from the magma) that would indicate 

the presence of the magma at shallow 

depth in the volcano. 

The explosive eruptions to date are 

phreatic eruptions, attributed mainly 

to subsurface water coming into contact with very hot rocks that are being 

heated by the magma beneath. When 

the water reaches boiling temperature, 

it expands suddenly and violently into 

steam. Rapid expansion of other gases, 

such as carbon dioxide, also may contribute to these eruptions. 

Earthquakes recorded today in the 

Mount St. Helens area included 39 

ranging in magnitude from 3.5 to 4.4, 

part of a total of 86 that exceeded 

magnitude 3. 

20 The First 100 Days of Mount St. Helens 

Field crews installed the first tiltmeter station, which will help to 

measure the surface deformation of 

the volcano. A tiltmeter network is 

planned, in conjunction with the use of 

precise distance-measuring instruments, so that changes in the volcano's 

shape-particularly swelling that 

might indicate upward movement of 

the magma (fig. 3)-can be detected. 

USGS hydrologists continue to 

monitor the streams closely but have 

detected no unusual increases in 

streamflow. Stream-water quality also 

has remained stable, except at sampling sites on two streams southeast of 

Mount St. Helens, both about 40 miles 

from the mountain and in the path of 

ash from yesterday's eruptions. Water 

acidity, hydrologists have found, increased slightly at those sites; the pH, 

an index of acidity or alkalinity, went 

from about 7 (neutral) to. 6 (slightly 

acid). (The pH returned to normal 

within 2 days.) 

FIGURE 10.-The sight of two craters instead of one greeted airborne observers 

as clouds lifted over Mount St. Helens on 

March 29, 1980, after more than a day of 

bad weather and frequent eruptions. At 

night, blue flames, probably from burning hydrogen sulfide gas, were flickering 

within the old crater (left) or jumping 

from crater to crater. The view here is 

from the north. (Photograph by David 

Frank, USGS, March 30, 1980.) 

FIGURE 11.-Erupted plumes of ash and 

steam (and minor amounts of other 

gases) were carried from the crater by 

winds and sometimes streamed down the 

flanks of Mount St. Helens for considerable distances. Spectacular displays 

of lightning occasionally were generated 

in these ground-hugging plumes by 

charges of static electricity built up when 

ash particles rubbed against one another 

in the turbulent cloud. This photograph 

was taken from the northwest by David 

P. Dethier (USGS) on AprilS, 1980. 

Some tourists admitted to reporters 

that, despite roadblocks, they had 

evaded the barriers and gone closer to 

the mountain but could not see the 

volcano because of the cloud cover. 

Sunday, March 30 

E Dav Minus 49 

The first major eruption of the day 

was reported at 4:10 a.m. By 7:40 

a.m., a huge anvil-shaped cloud of 

steam and ash had formed; drifting to 

the southeast, it produced light ashfalls 

miles away. Fine gray volcanic ash was 

reported at Stevenson, Wash., about 

25 miles south of the volcano, and officials were concerned about the effects 

of the ash on the quality of the Bull 

Run River, the main water source for 

Portland. Five later eruptions sent ash 

more than 1 mile above the twin 

craters. Altogether, observers counted 

93 eruptions of steam and ash from the 

volcano today. 

Last night, airborne observers could 

see a flickering blue flame burning 

within the old crater or jumping from 

crater to crater. Volcanologist Johnston reasoned that the blue flame meant 

that a flammable gas was being emitted. Possible gases were hydrogen, 

hydrogen sulfide, methane, or carbon 

monoxide, the most likely being 

hydrogen sulfide. (The flame disappeared on April 2 before scientists 

could determine the exact composition 

of the gas.) Burning gas has been 

observed previously above lava flows 

and lava lakes in other volcanic regions 

but not in craters before the appearance of lava. 

Seismographs at the University of 

Washington recorded 58 earthquakes 

of magnitudes greater than 3.0, including 6 above 4.0. 

A group from Dartmouth College in 

Hanover, N.H., began remote monitoring of sulfur dioxide (S02). Early 

results showing that the volcano is 

emitting S02 at the rate of 0.3 tons a 

day verify the March 28 identification 

of the gas, which is typically found in 

emanations from magma. This measurement also shows that Mount St. 

Helens at present is not a major source 

of sulfurous air pollution. (For comparison, some large coal-burning 

powerplants may emit more than 100 

tons of S02 a day.) 

In the afternoon, as many as 70 aircraft reportedly were flying around the 

volcano at the same time, and strict 

air-traffic control was necessary to prevent aerial collisions. 

Monday, March 31 

E Day Minus 48 

Shifting winds sent ash from the 

volcano's frequent eruptions toward 

different, more densely populated 

areas today. By noon, the KelsoLongview area, about 40 miles west of 

Mount St. Helens, was lightly dusted 

by ash. No juvenile rock material has 

been seen in the ash at month's end. 

Airborne observers reported that the 

twin craters are both growing and have 

nearly merged. 

The frequency of earthquakes near 

the volcano slackened, although an increase in the number having magnitudes greater than 4.3 suggests that the 

total energy release remains about the 

same. 

Tourists, who earlier had been disappointed by bad weather and roadblocks around the mountain, have 

been penetrating the closure boundary 

during the good weather at the end of 

March ". . . until it appeared," wrote 

Bill Stewart in the Vancouver Columbian, "that there was a competition to 

see who could get closest. Some people 

[in helicopters] actually landed on the 

crater rim and climbed inside." One 

group wearing camouflage clothing 

climbed to the top and filmed scenes intended for a documentary movie-and 

for beer commercials. 

Tuesday, April1 

E Day Minus 47 

Clouds shrouded the lower part of 

the mountain, as they do much of the 

time, but the top was clear enough for 

22 The First 100 Days of Mount St. Helens 

aerial observations. Several eruptions 

of ash and steam made clouds that 

reached as high as about 20,000 

feet-10,000 feet above the peak. Light 

ashfall was reported on the outskirts of 

Vancouver, and the village of Cougar, 

11 miles southwest of the volcano, 

received somewhat larger amounts. 

Some observers believe that these eruptions are the strongest since the volcano reawoke last month. 

USGS scientists reported that a huge 

wedge (graben) of ice-capped rocks, 

including the crater area, has settled at 

least 200 feet downward between the 

systems of major cracks crossing the 

mountaintop (see fig. 14). This settling 

has caused a noticeable outward displacement, or bulging, of the rocks and 

glacier ice north of the crater. Airborne 

observers noted that the two summit 

craters are now essentially a single 

crater more than 600 feet across. At 

least two new steam vents also were 

spotted in the crater area. 

Last night and early this morning, 

seismographs recorded three of the 

strongest quakes to date-two with 

magnitudes of 4.6 and one of 4.7. This 

afternoon, another of magnitude 4.6 

occurred. 

Between 7:25 and 7:30p.m., the first 

weak harmonic tremor was noted on 

the seismograms at the University of 

Washington seismology center. It was 

an undulating ground movement of the 

kind typically associated with the 

underground movement of magma 

(fig. 12). (Although harmonic tremor 

has preceded and accompanied volcanic eruptions in Hawaii, it may occur 

without being followed by an 

eruption.) 

Volcano experts are saying that the 

possibility of eruptions involving 

magma seems to be increasing. Their 

evidence includes the stronger earthquakes accompanied by harmonic 

tremor; the new steam vents and the 

more vigorous eruptions, which may 

reflect a general heating up of the 

volcano; and the presence in the gas 

· samples taken last Friday of sulfur 
FIGURE 12.-Seismograph traces comparing harmonic tremor (top) to normal earthquake 

pattern (bottom). (Data from the University of Washington Geophysics Program.) 

dioxide, which shows that a hightemperature source for the gas exists 

within the mountain. A magmatic 

eruption may not occur soon, however, and its onset cannot yet be 

predicted. 

Scientists are eager to get new aerial 

photographs looking straight down on 

the mountain to compare with similar 

vertical photographs taken in 1979. 

Comparison of the two sets of photographs will help to determine the 

physical changes that the mountain has 

undergone during the last few months. 

A U-2 reconnaissance plane took highaltitude pictures of the volcano today, 

but the images were unsatisfactory 

because clouds obscured too much of 

the area. 

Representatives of the University of 

Washington Geophysics Program and 

the USGS field headquarters have decided to install a computer link between the seismology center in Seattle 

and the Vancouver facility to improve 

the exchange of scientific data and to 

speed warnings of earthquake-related 

hazards. 

April 1, which usually marks the 

start of the mountain-climbing season, 

finds Mount St. Helens closed to climbing. Spirit Lake, which (by Forest Service records) averages 658,000 "visits" a 

year, is also closed. Farther from the 

mountain, however, about 300 loggers 

have returned to their jobs on and near 

the lower flanks of Mount St. Helens 

and at Camp Baker, some 15 miles 

northwest of the peak (fig. 13). 

Officials of Cowlitz and Skamania 

Counties have decided, because of 

limited county budgets and small lawenforcement staffs, that they must ask 

the Washington National Guard to 

help maintain the roadblocks around 

the volcano. Sheriffs' deputies from 

both counties have been manning 

roadblocks across several main access 

roads west and south of the mountain 

around the clock since last Thursday, 

the day of the first eruption. 

The restricted zone (fig. 13) is not 

difficult to enter because the mountain 

is crisscrossed by dirt logging roads. 

One official estimated that, instead of 

the 6 roadblocks being maintained by 

Cowlitz County, as many as 29 barriers requiring about 180 officers 

would be needed to completely block 

the mountain roads. 

Nolan Lewis, Cowlitz County Emergency Services Director, was quoted 

today in the Tacoma News Tribune: "I 

just can't fathom it," he said. "People 

are swarming in from all over, putting 

their lives in danger. . . Sunday, when 

the weather was clear, the road up to 

the mountain looked like downtown 

Seattle at rush hour." 

Wednesday, April 2 

E Day Minus 46 

A stronger burst of harmonic tremor 

was recorded by many seismographs in 

the Mount St. Helens area between 

about 7:35 and 7:50 a.m. This burst 

confirmed the recognition of the harmonic tremor of yesterday and is the 

best indication to date that magma is 

moving beneath the mountain. (Seismologists later determined that short 

episodes of harmonic tremor also occurred on March 31 and earlier this 

morning.) 

The number of earthquakes greater 

than magnitude 3.0 increased to 63 today, reversing the decreasing trend of 

the past 3 days. Five of the quakes were 

stronger than magnitude 4.0; one was 

4.8, among the strongest of the volcanic sequence to date. (Today was to 

be the most active day, for earthquakes 

stronger than magnitude 3.0, during 

the month of April.) 

At least a dozen major eruption 

plumes shot above the mountain, one 

reaching an altitude of more than 

20,000 feet. Large boulders and "blocks 

of undetermined matter" (rock or ice) 

were thrown out of the crater during 

one 30-minute eruption in midafternoon. A light ashfall left small 

amounts of ash on automobiles in Vancouver and Portland. 

The Forest Service's Pine Creek 

Ranger Station, south of the volcano, 

was closed permanently today. It had 

been evacuated on March 27. 

Asked about the likelihood of an explosive eruption-one that would hurl 

rock and lava from the mountain 

-Mullineaux replied that it was the 

Chronology of the First 100 Days 23 
7 

13.- Map of 

and vicinity showing generalized locations of the various boundaries of the restricted-entry zones established by the 

State of Washington and the Forest Servic~ at the indicated times during the 

period from March 25 to June 27, 1980. 

Entry to hazardous zones was further 

restricted by State and county 

roadblocks placed at key locations on 

roads leading to the volcano. (Data from 

Washington Department of Emergency 

Services and U.S. Forest Service.) 

EXPLANATION 

Date Established '_+-..._ ___ .._,..,_.._~--.....,.. 

March 25 

June 2 (WOES) 

June 4,11 (USFS) 

10 20 

T1et 

Draper Spr ·--".c.~.tt---1---- ----

Gtlmero,~ 

~ 

\,; 

«-' 

' / 

30 KILOME 

Base from U.S. Geological Survey 
least likely of the volcano's possible actions. "A series of small eruptions 

would be more likely than a large, 

cataclysmic event," he said. 

State of Emergency 

Thursday, April 3 

E Day Minus 45 

Washington Governor Dixy Lee Ray 

today declared a state of emergency 

and set up a "Mount St. Helens Watch 

Group." Local officials in both 

Washington and Oregon issued leaflets 

prepared by the Federal Emergency 

Management Agency entitled "What 

To Do During a Volcano Ashfall. " The 

leaflet gives advice on the dangers of 

ashfalls, mudflows, and floods. 

Seismographs recorded six earthquakes of magnitude 4.0 and greater, 

the strongest of which was 4.6. Two 

more bursts of harmonic tremor occurring this evening indicate continued 

movement of magma beneath the 

mountain. The total duration of harmonic tremor-33 minutes-is more 

than double last evening's IS-minute 

episode. 

Airborne observers reported that the 

crater has enlarged to a diameter of 

about 1,500 feet and a depth of about 

300 feet. Plumes of steam and ash 

billow from the crater almost hourly. 

Traces of volcanic ash fell in and near 

Tacoma, about 70 miles north of the 

mountain. 

Friday, April 4 

E Day Minus 44 

Two episodes of harmonic tremor 27 

and 32 minutes in duration were recorded by seismographs today, as were 

five earthquakes stronger than 

magnitude 4.0 and many weaker 

quakes. 

Governor Ray called out the National Guard to share duties at 

roadblocks around Mount St. Helens. 

Only property owners and scientists 

are to be allowed inside the blockaded 

zone. 

In an effort to protect sightseers and 

to keep them out of the way, Washington State officials moved one roadblock on State Route 504 about 20 

miles farther from the mountain and 

established a major public viewing area 

near Ridgefield, Wash., about 40 miles 

from the volcano. 

Loggers and truckers are urging 

county officials to let them resume 

work in the restricted zone, and they 

have offered to sign waivers releasing 

public officials from liability for any 

volcano-related casualties. An attorney for several logging companies 

argued that loggers should be able to 

make their own choice about entering 

and working in the restricted zone, 

"since they make their living in the 

woods and are familiar with the dangers," according to a story in the Seattle Post-lntelligencer. 

No measurable radioactivity was 

found in the volcanic ash during 

radiological testing reported today by 

the Washington Department of Social 

and Health Services. According to 

State health officials, there is no reason 

to believe that the small amounts of 

ash that sometimes drift beyond the 

immediate vicinity of the volcano are 

dangerous to people in good health. 

Most scientists believe that the 

greatest hazard currently posed by the 

reawakened volcano is the possibility 

of flash floods or mudflows, especially 

those that might enter Swift Reservoir 

and cause a massive overflow and 

flood surge into the downstream channel and reservoirs. 

USGS hydrologist David Frank set 

up a time-lapse movie camera to take 

color pictures of the periodically erupting volcano. The camera, designed to 

expose one frame of film after each 

preset time interval, was installed on a 

logged-off ridge accessible only by logging roads, 8.4 miles northwest of the 

volcano's summit. The site overlooks 

the North Fork Toutle River near the 

mouth of Coldwater Creek and affords 

an unobstructed view of Mount St. 

Helens. It also is high enough to be safe 

from even the largest mudflow that 

might result if the ice and snow were 

melted by the volcano's heat. The site 

was selected a few days ago as a scientific observation post, and a tent was 

set up to shelter observers. Additional 

instruments, including another timelapse camera, will be installed within 

the next few days. Scientists refer to 

the observation site as "Coldwater" 

(later called "Coldwater I"; see fig. 7). 

Saturday, April 5 

E Day Minus 43 

At least three eruptions today sent 

ash to altitudes of about 15,000 feet, 

and scientists using airborne measuring 

devices detected low concentrations of 

sulfur dioxide in the plume. Only four 

earthquakes today reached magnitude 

4.0 or greater. Harmonic tremor occurred for 16 minutes shortly before 

noon. 

Sixty Washington National Guardsmen took up duties this morning at 

four roadblocks on major routes to 

Mount St. Helens. They immediately 

moved two of the roadblocks farther 

away from the mountain to allow them 

better control of side roads leading to 

the volcano and to place some of the 

most congested (and therefore potentially most dangerous) viewing spots 

off limits. 

Scientists and technicians have been 

working long hours in the field under 

difficult and often risky conditions. 

When the weather permits, some are 

flown by helicopter from Vancouver to 

various places on the mountain or to 

nearby sites such as Timberline Viewpoint or Spirit Lake (fig. 7), depending 

on their scientific specialty or work 

assignment. If expensive helicopter 

support is not available, investigators 

must drive to the area, usually by way 

of State Route 504 through the valley 

of North Fork Toutle River, from 

headquarters in Seattle and Tacoma as 

well as in Vancouver. Ground travel 

away from the vehicles usually involves 

Chronology of the First 100 Days 25 
trudging through deep snow. Heavy 

rain or snowfall, often accompanied by 

bitter wind, is common in the area. 

When bad storms hit, fieldworkers use 

tents and umbrellas to shelter sensitive 

instruments during the measurements. 

Fieldwork includes visiting instrument 

sites to change batteries and calibrate 

instruments already in place or to install additional instruments; photographing the widening crevasses in the 

upper glaciers; making measurements 

of gravity and magnetic field with 

portable instruments; and sampling 

and measuring fumarole gases, 

volcanic ash, and the flow of streams 

draining from the mountain. Some of 

the work must be done on avalancheprone slopes while the upper parts of 

the mountain are hidden in clouds. At 

such times, the sudden, strong earthquakes can be startling. During good 

weather, helicopters ferry scientists 

from one site to another during the day 

and return them to Vancouver in the 

evening. The helicopter flights are 

made during the daylight hours, but 

the long drives to and from the area 

often begin and end in darkness. 

Workers from Vancouver then conduct 

evening conferences to review the day's 

activities. Fourteen-hour working days 

are common; clockwatching is mainly 

for timing scientific observations and 

resetting instruments. 

Most scientists, however, prefer the 

hardships and long hours in the field to 

remaining at the Vancouver center and 

being besieged by news reporters, who 

persist in asking questions that the 

scientists cannot answer about what 

the volcano will do next. 

Sunday, April 6 

E Day Minus 42 

Although clouds, rain, snow, and occasional "mud rains" containing ash 

hampered visibility today, they did 

keep away much of the expected crowd 

of sightseers. The Spirit Lake area 

received 6 inches of new snow. Scientists termed the few eruptions of ash 

and steam as "insignificant." 

Earthquake activity around Mount 

St. Helens was about the same as it has 

been in the last few days-hundreds of 

quakes of magnitude 3 or less, 54 

greater than magnitude 3, and 6 of 

magnitude 4.0 or greater. No harmonic 

tremor was recorded today, however. 

Scientists found the ash to be 3 inches thick on the eastern flank of the 

mountain at the 5,000-foot level. 

In an interview with Seattle Times 

reporter Hill Williams, USGS geologist 

Crandell explained that scientists really 

do not know what to expect from the 

volcano because information about actual eruptions of Cascade Range volcanoes is limited and because the eruptive history of Mount St. Helens is 

different from that of other Cascade 

volcanoes. "Mount St. Helens has done 

so many different things in the past 

that hardly anything would be a surprise," Crandell said. 'The only thing 

it hasn't done is blow itself apart." 

Monday, April 7 

E Day Minus 41 

For the fix:st time, observers today 

got a clear view of a vent in the floor of 

the enlarged crater and saw a single circular "throat" at least 20 feet in 

diameter in the deepest part of the floor 

(fig. 14E). The crater, which has been 

enlarging progressively since March 

27, is now about 1,700 feet long (east 

to west), 1,200 feet wide, and 500 feet 

deep. Airborl:le observers reported 

ponds of muddy water, large enough 

to float chunks of ice, in depressions in 

the crater floor. The ponds are fed by 

melt water from the crater walls and a 

capping of ice 30 feet thick on the 

crater's rim. The water reportedly 

disappears with each eruption, but 

more water accumulates again soon 

after an eruption subsides. Two of the 

ponds have short streams draining 

from them into the crater bottom. This · 

is the first report of substantial pending in the crater. 

Overall seismic activity at Mount St. 

Helens continues at about the same 

26 The First 100 Days of Mount St. Helens 

level. Although the number of earthquakes greater than magnitude 3 declined slightly today, the activity included one event of magnitude 4.7 and 

one of 4.6. A 15-minute episode of harmonic tremor occurred, the first in 2 

days. Most quakes were clustered beneath the volcano at depths ranging 

from 0.5 to 3 miles. A plot of earthquake epicenters since March 20, completed today by scientists from the 

University of Washington Geophysics 

Program, showed a heavy concentration of quake locations under the 

northern slopes of Mount St. Helens. 

Scientists installed a new tiltmeter in 

the parking lot at Timberline Viewpoint, 2.6 miles northeast of the crater 

(fig. 7). The snow there, 3 feet deep in 

places, hampers the work of scientists 

who are using various kinds of geophysical instruments to detect changes 

in the shape and subsurface makeup of 

the mountain. The snow surface is 

coated with volcanic ash, and pits dug 

in the snow show alternating layers of 

ash and snow that have fallen during 

the last 12 days. 

Tuesday, April 8 

E Day Minus 40 

One long, single eruption, visible for 

more than 5 hours, was first seen at 

8:22 a.m. and continued until at least 

2:00p.m. today. 

During the eruption, a hole opened 

in the ice at the head of Wishbone 

Glacier (fig. 5), near the northwestern 

rim of the crater, and melt water from 

the surrounding ice poured into the 

hole for several minutes to form a 

pond. Then the rim cracked, the water 

disappeared, and a slice of the upper 

Wishbone Glacier caved into the 

crater, enlarging the crater's northwestern side by more than 300 feet. For 

several minutes after the cave-in, airborne observers noted an especially 

heavy concentration of dark ash in the 

eruption cloud. 

On calm days, the white clouds of 

steam from the volcano sometimes rise 

nearly 10,000 feet above the crater rim, 
and they often resemble thunderheads. 

On windy days, the steam is carried 

out laterally from the crater. At times, 

winds direct the clouds downslope on 

the leeside of the cone as a groundhugging plume that deposits ash as it 

moves (fig. 11). A pattern of black 

scallops on the s1ope of the volcano 

often marks the lower limit of these 

downslope plumes. 

There is still much uncertainty and 

speculation about what the volcano 

will do next. Some news reporters 

complain that they get a different idea 

or view from each scientist interviewed, depending on his background 

and specialty. Most scientists prefer to 

withhold judgment until they have 

more data to help them decipher the 

volcanic events. 

Wednesday, April 9 

E Day Minus 39 

Cloud cover prevented scientists 

from observing the mountain today, 

either from the air or the ground, but 

light ashfalls near Timberline Viewpoint and Spirit Lake and the odor of 

sulfur marked at least three eruptions. 

An apparent decrease in seismic activity, begun yesterday, continued today. Yesterday, only 38 earthquakes 

greater than magnitude 3 were recorded, 4 of which reached or exceeded 

magnitude 4. Today's totals were 37 

and 6, respectively. No harmonic 

tremor was recorded either day. (This 

general level of seismic activity was to 

continue throughout April. Most days 

this month saw less than 40 events 

stronger than magnitude 3 and less 

than 10 events of magnitude 4 or 

greater.) 

The new tiltmeter installed near 

Timberline Viewpoint started sending 

to Vancouver continuous records that 

are expected to show any deformation 

of the mountain's northern flank. 

The Forest Service officially designated Mount St. Helens as a "Geological Area," an area that is protected 

from land-use changes because of its 

geologic importance. 

Thursday, AprillO 

E Day Minus 38 

Clouds covered the mountain most 

of the morning, but they cleared 

enough for aerial observation by early 

afternoon. Several major and minor 

eruptions of steam and ash occurred at 

irregular intervals, most of them 

lasting no more than a few minutes. 

A fresh snowfall last night, as yet 

unsullied by ash on the southern side of 

the peak, gave residents and tourists to 

the south much the same view of the 

mountain that has existed for more 

than a century. Fracturing and slumping on the upper northern side, however, are causing cracks in the ice cap 

that are much too large to be hidden by 

the fresh snow. 

The progressively enlarging crater 

now measures about 2,000 by 1,200 

feet. Coatings of gray volcanic ash give 

the northern side of the crater's interior 

a velvety look, except for some jagged 

rock outcroppings and scattered huge 

blocks of fallen rock on the crater floor 

(fig. 14E). The eruptions are confined 

to a single circular vent, perhaps 30 

feet across, in the position of the second (western) crater but now at least 

500 feet lower than the opening originally blasted through the volcano's icecap on March 27. The position of the 

first, more easterly crater has been 

largely obscured by crater growth. To 

the west of the active vent, however, 

the presence of a cone-shaped depression in the crater floor, separated from 

the active vent by a small, sharp ridge, 

suggests that a third orifice for the 

eruptions of steam and ash may have 

been active until recently. 

Some of the intermittent eruptions 

since March 27 have consisted of a 

single explosion; others have surged 

upward in pulses. The cloud sometimes 

consists of three parts: (1) a lower, 

very dark, tephra-rich finger, (2) an intermediate gray cloud of ash and 

steam, and (3) an upper cloud of white 

steam (figs. 148, C). The intermediate 

part develops from the dark finger and 

soon roils out in all directions to 

obscure the finger that feeds it. Blocks 

of rock and ice occasionally blast 

through the cloud. As the gray clouds 

drift downward, thin veils of ash fall 

from them. 

Lobate fingers of several "generations" of ash-darkened snow and ice 

avalanches reach down to the lower 

slopes of the mountain. The youngest 

are darkest and contrast sharply with 

the stark white of the newly fallen 

snow. 

Harmonic tremor, the first in 3 days, 

occurred twice today. One episode 

lasted for 22 minutes, the other for 16. 

Gravity has been measured repeatedly at most of the established gravity 

stations, but, so far, measurements 

near the mountain have shown little 

change. Precise instrumental 

measurements on the mountain often 

are hampered by rapid, short-term 

tilting of the ground. Two scientists 

measuring the gravity at East Dome 

(fig. 5) felt an earthquake and then 

watched with fascination as the level 

bubbles on their gravity instruments 

moved far offcenter in response to a 

strong upward tilt of the mountainside 

above them. This tilt was followed a 

few minutes later by a puff of steam 

from the crater, whereupon the bubbles registered a similar tilt in the opposite direction. 

Friday, Aprilll 

E Day Minus 37 

Good weather returned to the mountain, which continued to erupt intermittently. Airborne observers could 

see into the crater during a moderate 

eruption that took place from 6:12 to 

6:58 a.m. They saw large blocks of ice 

being hurled into the air along with ash 

and steam and also noticed two new 

steam vents on the northwestern flank 

of the volcano, just below the crater 

rim, as well as ponded water on the 

floor of the crater. 

For only the second time since activity began 23 days ago, a magnitude-4.9 

earthquake occurred today at 3:51 

p.m. This quake and the similar one on 

Chronology of the First 100 Days 27 
FIGURE 14.-Aerial views of the Mount St. 

Helens crater and eruptions on April10, 

1980, from the north and northwest. A , 

The oblong crater, enlarged since the 

merging of two smaller pits, continued to 

grow with the repeated eruptions and 

avalanches from the crater walls. The 

summit graben had slumped noticeably 

since March 30, as the prominent offset 

(scarp) along the major crack (fault) on 

the southern side (back) of the crater 

shows. (Compare with fig. 10.) 

(Photograph by John Whetten, USGS.) 

B, The beginning of one of several eruptions observed on April10. The eruptive 

cloud often included a lower, very dark, 

ash-rich finger; an intermediate gray 

cloud of mixed ash and steam; and an 

upper, white cloud of steam. (Photograph by Fred Pessl, Jr., USGS.) C, These 

phreatic eruptions seemed to grow in 

slow motion because of the immensity of 

the scene. Some were powerful enough to 

throw out automobile-sized blocks of 

rock and ice. (Photograph by John 

Whetten, USGS.) D, A moderate-sized 

eruption cloud obscured the crater as 

steam and ash drifted eastward. 

(Photograph by John Whetten, USGS.) 

E, By April 10, eruptions were coming 

from a single circular vent (shown by an 

arrow) in the lowest part of the crater 

and almost directly below the position of 

the crater first seen on March 29 (fig. 10). 

Traces of what probably was another, 

but now-dormant, vent can be seen to 

the right of the active vent, here steaming 

weakly. The active vent was about 30 

feet across. (Photograph by John Whetten, USGS.) 

March 28 have been the strongest of 

the volcanic earthquakes to date. 

The results of tiltmeter measurements on the volcano's northern and 

eastern flanks are, so far, inconclusive. 

Although the ground both swells and 

subsides over periods of minutes or 

hours, the net change seems to be insignificant. 

Signs now have been posted along 

Interstate Highway 5 notifying motorists of four safe points from which to 

view Mount St. Helens. 
Saturday, April12 

E Day Minus 36 

Continued clear weather allowed 

viewers as far away as Portland to see 

some of today's many eruptions. Most 

were small, as activity was less than it 

has been in the past 2 weeks, but a few 

larger ash-rich clouds lifted above the 

crater rim. As the summit crater gradually deepens, eruptive plumes must rise 

to greater heights in order to be visible 

above the mountain. 

Instruments have detected a slight 

swelling on the northern flank of the 

mountain near Goat Rocks (fig. 5), and 

scientists working on the volcano's 

flank report fresh, new ground cracks 

in the swelling area. The clearer 

weather today made it possible to take 

aerial photographs so that the shape of 

the mountain could be compared systematically with its shape as shown on 

photographs taken last year. Progressive shifting and cracking of the ice 

on the northern side below the crater 

are increasing concern that a large 

mass of ice and rock could break loose 

and form an avalanche reaching to the 

valley of the North Fork Toutle River. 

A period of harmonic tremor beginning at 2:12p.m. and lasting until 2:29 

p.m. ended with an earthquake of 

magnitude 4.5. (This harmonic tremor 

was to be the last recorded for nearly a 

month.) 

USGS Director H. William Menard 

arrived in Vancouver to observe the 

volcano and to inspect the scientific instrument installations and data-collection activities. 

Officials of Skamania County, in 

which Mount St. Helens is located, are 

speculating about how long they can 

(and can afford to) control access to 

the mountain. Some question whether 

it is even appropriate for the county to 

keep people out against their will. 

Sunday, April13 

E Day Minus 35 

Between sunrise and sunset today, 

USGS scientists counted 18 eruptions 

of steam and ash ranging in duration 

from a few minutes to 45 minutes. 

The recording tiltmeter installed in 

the parking lot at Timberline Viewpoint showed small but consistent 

changes, the overall results indicating a 

slight subsidence of the central part of 

the volcano relative to the Timberline 

instrument station. In order to monitor 

surface tilt more closely, the USGS installed an additional tiltmeter on East 

Dome at the foot of Ape Glacier. 

The number of earthquakes of magnitude 4 or greater increased slightly 

today; there were nine, the largest 

number since March 29. 

Clear weather brought record-breaking numbers of sightseers to the area 

from all over the United States and 

from other countries. This weekend, 

two television camera crews were 

airlifted onto the mountain in defiance 

of closure orders, and unauthorized 

climbers were also sighted. Forest Service officials warned again that the 

mountain is not safe and that it is off 

limits to the press and public above the 

4,400-foot level. 

Chronology of the First 100 Days 29 
Eruptive Activity 

Decreases 

Monday, April 14 

E Day Minus 34 

Cloudy weather prevented scientists 

from seeing the volcano, and no new 

ash fell today. Instruments, however, 

continue the volcano watch. Seismometers show a continuation of 

sizable earthquakes but no ~ruptions. 

The recording tiltmeter at Timberline 

Viewpoint showed a shift that may 

represent additional slight subsidence 

in the central part of the volcano. The 

evidence from this one instrument, 

however, is not conclusive. 

Tuesday, April 15 

E Day Minus 33 

Mount St. Helens became visible by 

midday for the first time since Sunday, 

and observers were able to verify that 

the volcano has slowed its eruptive activity. Only one eruption, near dawn, 

was seen today. The apparent slight 

subsidence of the cone has stopped; no 

change in the ground tilt was recorded 

by the tiltmeters. Teams are in the field 

during this lull to collect samples and 

to try to evaluate the volcano's status. 

The Washington Department of 

Game announced that three popular 

fishing lakes near Mount St. Helens 

will remain closed when the regular 

fishing season opens next Sunday. Officials felt that Merrill Lake, Spirit 

Lake, and Swift Reservoir, if they were 

not closed, would add to the temptation to slip around the roadblocks and 

enter hazardous areas. 

Wednesday, April 16 

E Day Minus 32 

Activity was low again today, 

although at least nine small steam 

eruptions and some ashfalls occurred 

during daylight hours. Seismic activity 

is lower than it has been at any other 

time during the month; only 30 earthquakes greater than magnitude 3 occurred today. Three quakes greater 

than magnitude 4 were recorded during 

the early morning hours, and two more 

were recorded this evening. The tiltmeters continued to show no changein 

ground tilt. 

Some erupting volcanoes have 

shown a marked decrease in activity 

followed by a dramatic increase in 

seismic activity just before a major 

eruption. Scientists have no way of 

knowing, however, whether Mount St. 

Helens is experiencing a "lull before the 

storm" of a magmatic eruption or possibly is in the final part of the eruptive 

sequence. 

A sampling project begun on April 

14 ended today as scientists completed 

taking ash fr..om 30 stations. The samples were taken from accumulated 

snow so that the ash would not be contaminated by soil. 

Thursday, April17 

E Day Minus 31 

The summit crater of Mount St. 

Helens erupted frequently but mildly 

today; 12 plumes were seen between 

7:00a.m. and 1:30 p.m. Two of them 

formed vertical columns that extended 

about 500 feet above the crater rim, 

but strong winds then carried the 

plumes away from the summit. In the 

afternoon, weather conditions prevented observers from seeing clearly 

into the crater. 

Seismic activity remained comparatively low, although two earthquakes 

of magnitude 4.6 occurred. Scientists 

took advantage of the relative lull in 

activity to make a gravity survey 

around the mountain, to place surveying targets near the summit, and to collect information on the total amount of 

ash accumulated. 

Some fisheries specialists are concerned that accumulating ash washed 

into the streams by water from the 

melting snow may harm the valuable 

fish population in streams near Mount 

St. Helens. When Mou~t Baker (fig. 1) 

suddenly increased its steaming activity in 1975, some of its emanations of 

gases and "fumarole dust" were acidic. 

A stream draining the fumarole area of 

30 The First 100 Days of Mount St. Helens 

Mount Baker apparently once carried 

enough acid water into nearby Baker 

Lake to cause some of the fish there to 

die. So far, however, none of the 

Mount St. Helens ash has been found 

to be strongly acidic. 

The greatest hazard other than ash, 

USGS scientists reported today, is the 

increasing instability of the northern 

flank of the volcano. Contributing to 

this instability are ground shaking, 

avalanching caused by continuing local 

earthquakes, subsiding of the summit 

graben, fracturing of ice and rocks, 

and accelerated melting of snow and 

ice caused by the heat of the volcano 

and possibly by solar heating of the 

fallen ash. This announcement marks a 

shift in the emphasis on hazards. The 

possibility of volcano-related flooding 

in the Lewis River drainage system is 

now thought to be less of a threat than 

the possibility of large avalanches from 

the volcano's northern slope. 

Friday, April 18 

E Day Minus 30 

Eruptions of steam and ash were rising only about 500 feet above the 

crater today, and seismic activity 

stayed at a moderate level. "Because all 

pertinent factors· seem to remain about 

the same each day," USGS scientists at 

Vancouver have decided to reduce 

their information releases from daily to 

twice weekly. 

Scientists are encouraged in their 

grueling work by the excitement derived from Mount St. Helens' spectacular, historic reawakening and by 

the opportunity for major scientific 

achievement. Few of the scientists, if 

any, had seriously expected to see a 

Cascade volcano in eruption, much 

less to be part of an intensive study of 

the volcanic activity. They are fascinated by what has occurred already, 

and each hopes for a spectacular event 

that will advance his or her scientific 

specialty. They also feel frustrated, 

however, by the frequent bad weather 

that obscures the mountain from view 

and hampers ground travel and 

fieldwork. 
Scientists who lack aircraft support 

are especially frustrated. Many aspects 

of the volcano can be seen only from 

the air, and scientific work on the 

mountain itself is not practical without 

helicopter support. For reasons of 

public safety, teams whose work deals 

with assessment or warning of the 

hazards have first call upon aircraft 

owned or chartered by Federal agencies. Scientists whose work does not 

relate closely to the hazardous potential of the volcanic activity may have 

long waits before they can be fitted into the busy flight schedule. Some 

distinguished scientists and government officials have arrived at Vancouver expecting to be given tours of 

the volcano, only to find that senior 

USGS scientists have Federal aircraft 

completely booked for urgent hazard 

assessments. 

Saturday, April19 

E Day Minus 29 

Seismographs today recorded about 

the same amount of earthquake activity as they have in recent days-37 

earthquakes greater than magnitude 3, 

including 8 greater than magnitude 4. 

One this afternoon, however, reached 

magnitude 4. 9, equaling the strongest 

to date. No harmonic tremor has appeared in the past week. 

Local scientists who are most familiar with the shape of Mount St. Helens 

are saying that the upper northern side 

of the mountain obviously has moved 

outward (northward), but they are not 

unanimous about cause and effect. 

Some believe that the outward 

displacement is caused by the downward-settling mass of the summit 

graben. Others believe that intruding 

magma is inflating the mountain and 

causing a spreading of the summit that 

allows the graben to subside (see fig. 

3). 

Snow surveyors from the U.S. Soil 

Conservation Service, who periodically measure snow depth and water content in order to predict snow-water 

resources, have been observing the 

melting rate of the ash-rich snow near 

Mount St. Helens. They reported recently that the snow is melting faster 

where it is covered by the dark ash 

because it absorbs more heat from the 

sun than the clean snow does. Whether 

spring runoff this year will be faster 

and the danger of flooding greater are 

still uncertain, because much of the 

water melted at the snow surface can 

be held in lower parts of the snowpack. 

USGS hydrologists report no evidence 

of unusual runoff at their streamgaging stations so far. 

Sunday, April 20 

E Day Minus 28 

No eruptions were seen today, but 

seismic activity increased somewhat. 

The number of earthquakes stronger 

than magnitude 3 was 47; 7 were 

stronger than magnitude 4. This count 

was the highest in 2 weeks. 

Although clouds have covered the 

peak most of the weekend, tourists 

continue to be a problem. These first 

weeks of volcanic activity have been 

treated as a gigantic carnival by some 

people in the Northwest, who have 

come to see Mount St. Helens "performing" on center stage. T -shirts imprinted with various slogans, coffee 

cups bearing photographs, plastic bags 

filled with ash, and other souvenirs are 

being offered for sale. Sightseers line 

the roads leading to the mountain in 

spite of the several "Mount St. Helens 

viewpoints" that the State of Washington has designated near Interstate 

Highway 5 so that the local roads 

leading to the mountain would be less 

congested. The opening of the sportfishing season this weekend doubtlessly contributed to the crowds in this 

popular fishing area. Understandably, 

a great many people want to see the 

first erupting volcano in the conterminous United States in more than half 

a century. 

Monday, April 21 

E Day Minus 27 

The lull in eruptive activity continues. Poor visibility kept scientists 

from observing the volcano closely today, but the instruments continue to 

watch. The seismographs indicate that 

earthquake activity today was less 

than it was yesterday and more like the 

previous week. 

On many of these typical cloudy 

spring days, airborne observers can fly 

above the clouds and see the mountain 

peak even though the lower slopes remain hidden. Mount St. Helens a~d its 

neighboring volcanoes then seem to be 

riding on a billowing sea of clouds. 

Nearest to Mount St. Helens are 

Mount Adams, Mount Hood, and 

Mount Rainier (fig. 1), all easily visible 

and identifiable. Mount Rainier is the 

giant of the group. Rising 14,410 feet 

above sea level, it dominates this part 

of the Cascade Range. Of these three 

neighboring volcanoes, only Mount 

Adams, closest to and due east of 

Mount St. Helens, has not erupted in 

historical times (table 1.) Even Mount 

Adams, however, may not be extinct. 

Tuesday, April 22 

E Day Minus 26 

Improved weather today brought 

better aerial views of Mount St. 

Helens, although low clouds still 

prevented observers on the ground 

from seeing the volcano clearly. Dawn 

disclosed a new mantle of snow on the 

mountain, covered in only one spot 

with a light dusting of ash. The only 

eruptions reported during the day were 

small bursts of steam during the noon 

hour that barely cleared the crater rim. 

Steam vents, not directly associated 

with the eruptions, can be seen on the 

eastern part of the summit area. The 

tiltmeters continued to record small 

changes that have not, as yet, shown a 

consistent pattern. 

In discussing the leveling off of eruptive and seismic activity, USGS 

volcanologist Johnston reminded reporters that, "Lassen in California 

went through a year of this kind of activity before it turned into a magmatic 

eruption in 1915." 

Chronology of the First 100 Days 31 
Northern Side Bulges 

Alarmingly 

Wednesday, April 23 

E Day Minus 25 

Good weather allowed scientists to 

observe the volcano more closely and 

to note that there were no eruptions 

large enough to add to the light mantle 

of ash seen on yesterday's new snow. 

The volcano's quiet period also permitted researchers to collect gas samples 

from the steaming areas near the summit itself. (Analyzed later, these 

samples were found to contain a high 

concentration of sulfur.) Two new 

steam vents were seen in the crater today. 

Although the slumping of the summit graben and the breaking up of 

glacier ice on the volcano's northern 

side have been evident for about 3 

weeks, the first real indication of the 

amount of deformation came today 

when optical comparisons of aerial 

photographs taken on August 15, 

1979, and on April 12, 1980 (11 days 

ago), were completed. These comparisons show that some places on the 

northern flank are about 250 feet 

higher than they were last year (fig. 

15). The full extent of the bulged area is 

not known. Scientists and technicians 

flying in by helicopter placed surveying targets on the northern flank of the 

volcano today to help monitor its 

changes in slope. 

Tiltmeters at Timberline Viewpoint 

and Spirit Lake indicated a slight tilting 

of the ground surface downward to the 

northwest; on the southern side of the 

mountain, tilting was downward to the 

southwest. This surface tilting suggests 

that the volcano may be inflating 

because of increasing magma pressure 

beneath it (fig. 3). 

The sustained period of relative 

quiet prompted Forest Service officials 

to schedule discussions within the next 

few days on opening some areas 

around the volcano to restricted use. 

USGS geologist Crandell, Mount St. 

Helens Hazard Coordinator, warned, 

however, that avalanches could begin 

on the unstable, bulging area of the 

northern slope and surge into areas 

downslope. Such avalanches, he said, 

could also cause floods by suddenly 

raising the level of Spirit Lake. An 

avalanche also could dam the North 

Fork Toutle River temporarily, and the 

dam could fail later in a washout that 

would release a torrent to downstream 

areas. 

USGS scientists in Vancouver, in response to demands for more frequent 

information about the volcano, agreed 

to resume daily information releases. 

Thursday, April 24 

E Day Minus 24 

Although fumaroles continued to 

emit steam near the summit crater, no 

ash eruptions were large enough to 

throw material outside the crater walls. 

The number of earthquakes was about 

the same as it has been in recent days, 

but the quakes were stronger; eight 

were of magnitude 4 or greater, and 

one reached magnitude 4.7. 

The USGS Volcanic Hazards Project 

made public a map showing the possible dangers presented by the bulge area 

and emphasized the potential for avalanches. 

Friday, April 25 

E Day Minus 23 

Fumaroles continued to steam today, and seismic activity continued at 

about the level that it has maintained 

for several days. About 1,560 earthquakes stronger than magnitude 3 have 

been recorded since activity at the 

volcano began March 20. More than 

200 have been stronger than magnitude 

4. 

Tiltmeters continue to show slight 

tilt that, once again, does not have a 

consistent pattern. In an effort to better 

define changes in the shape of the 

volcano, scientists are using electronic 

distance-measuring devices. They were 

32 The First 100 Days of Mount St. Helens 

able today to measure the precise 

distances to five targets on the upper 

slopes of the volcano, as well as two 

additional reference points nearby. 

These measurements, together with 

others to be made by using markers installed on the mountain today, will 

help to define the size, shape, and 

-growth of the bulge on the northern 

flank in days to come (fig. 16). 

Saturday, April 26 

E Day Minus 22 

The mountain is relatively quiet today. Clear weather allowed observers 

a good view of the crater, but they saw 

only fumaroles emitting steam and 

eruptive bursts too weak to lift ash outside the crater. The seismographs indicate that earthquake activity was 

about as low as it has been since March 

24. 

Tiltmeters on the mountain's eastern 

and southern flanks showed small, unsystematic changes, but the tiltmeter at 

Timberline Viewpoint recorded downward tilt to the north. 

Sunday, April 27 

E Day Minus 21 

The mountain remains quiet, 

although fumaroles continue to send 

up steam. One fumarole on the southeastern crater wall is especially active. 

Clear weather gave observers a good 

view today, but they saw no ash eruptions. 

On the ground, changes are being 

detected by the instruments. Ground 

tilt measured by the tiltmeter at 

Timberline Viewpoint now shows an 

increase in tilt, downward toward the 

northeast. This tilt is interpreted to 

mean that the volcano is swelling. In 

addition, surveys of the Goat Rocks 

FIGURE 15.-A comparison of the shape of 

Mount St. Helens (A) at the time of the 

March 27 eruption and (B) just before the 

May 18 eruption shows the large outward displacement of the bulge area. The 

view here is from the northeast. (Paintings by Dee Molenaar, USGS.) 
Summit crater 
FIGURE 16.-At Coldwater II observation station, a scientist (back to camera near rear of 

vehicle) uses a laser ranging instrument to measure distances to reflector targets on the 

northern side of Mount St. Helens, including the unstable bulge area (left and center 

parts of the mountain as viewed here). Dogs Head is on the skyline to the right of the 

tree, and Goat Rocks, the lava dome that formed during an eruptive period in the 

1840's, is directly above the rear of the vehicle. (Photograph by Harry Glicken, May 4, 

1980.) 

area using instruments on the flank of 

the volcano indicate that the area has 

moved outward, away from the main 

mass of the mountain, at least 15 to 20 

feet in the past 4 days. Geologists 

report seeing new fractures in the 

bulge; some ground locations on the 

bulge are now about 300 feet higher 

than they were in 1979. 

Monday, April 28 

E Day Minus 20 

Although poor visibility hampered 

aerial observations, there was no indication today that any eruptions of 

ash were large enough to extend beyond the crater. When the crater was 

visible, it was emitting clouds of steam 

punctuated by occasional short bursts 

of ash. 

The northern flank continues to 

deform, as the tiltmeter at Timberline 

indicates. Most scientists are unwilling 

to specify the exact cause of the tilting, 

but they generally agree that it probably is related to the subterranean 

movement of magma. 

Tuesday, April 29 

E Day Minus 19 

Continuing studies of aerial 

photographs show that the bulging 

area on the northern side of the mountain is now about 1 mile long and 0.5 

mile wide and has a northeast-trending 

axis that extends from the northern 

side of the summit crater toward Sugar 

Bowl, on the northeastern flank of the 

volcano. The outward displacement of 

the slope has caused ground positions 

on part of the bulge to be as much as 

320 feet higher than they were last 

year. From this maximum, the bulge 

decreases toward the east, north, and 

west. Ground surveys confirm that the 

deformation is continuing. Between 

April 27, when the last survey was 

made, and today, Goat Rocks has 

shifted about 9 feet toward the northnorthwest, and little or no vertical 

uplift has occurred. 

The tiltmeter at Timberline Viewpoint, on the northeastern side of the 

volcano, indicates tilting downward to 

34 The First 100 Days of Mount St. Helens 

the north and confirms that the bulge 

extends to that site as well. 

The mountain itself remains relatively quiet; it has produced only 27 earthquakes stronger than magnitude 3.0 

and no sizable eruptions. 

The bulge continues to cause scientists concern. They now believe that it 

represents the most serious potential 

hazard from the present volcanic activity. They are especially worried 

about the likelihood of avalanches 

headed toward the North Fork Toutle 

River and Spirit Lake. (Spirit Lake 

itself was formed over a period of time 

by volcanic mudflows damming the 

river.) USGS geologist Crandell said, 

in a prepared statement to be released 

tomorrow morning, that Forsyth 

Glacier (fig. 5), upslope from Spirit 

Lake, "looks so unstable that a sharp 

earthquake or volcanic explosion could 

trigger a large avalanche of snow, ice, 

and possibly rock, without warning. In 

addition, measurements indicate that 

the upper part of the volcano from 

Forsyth Glacier west to Goat Rocks 

is shifting and may be unstable. An 

avalanche from this high part of the 

volcano could result in [millions of] 

tons of debris dropping a vertical 

distance of more than 4,000 feet, from 

an altitude of about 7,600 feet down to 

about 3,200 feet, the altitude of Spirit 

Lake. Such an avalanche could move 

downslope at a high velocity-more 

than 100 miles per hour-and could 

move long distances, certainly as far as 

[State Route] 504, about two and a 

quarter miles away." 

Scientists believe that such an 

avalanche could extend beyond Timberline Viewpoint as far as Spirit Lake 

and could cause a large surge wave in 

the lake. The momentum of such an 

avalanche might carry parts of it across 

the valley of the North Fork Toutle 

River west of Spirit Lake and upslope 

along the northern wall of that valley, 

as well as down the valley to the west. 

Emergency-services officials are being frustrated in their attempts to make 

the public aware of potential dangers. 

One official, quoted in the Seattle Post-
Intelligencer, said, "The hardest thing 

is to warn people of the danger. The 

mountain looks so serene, so people 

can't fathom 4,000 vertical feet of 

earth, rock, and ice plunging into 

[Spirit Lake] in less than two minutes." 

Wednesday, April 30 

E Day Minus 18 

The crater was not active today, except for steam venting from many 

fumaroles. Earthquakes continued, although larger ones-those stronger 

than magnitude 4-numbered only 6, 

and only 15 stronger than magnitude 3 

were recorded. Since March 20, about 

240 earthquakes of magnitude 4 or 

greater have been recorded. 

The northern flank of the volcano 

continues to swell and move outward. 

In order to compare the large movement at Goat Rocks with possible 

movement elsewhere on the mountain, 

scientists commenced ground measurements near Sugar Bowl and Dogs 

Head, ancient lava domes that are 

prominences on the northeastern side 

of the cone near the base and the upper 

flank of the bulge, respectively (figs.5 

and 16). 

During the lull in eruptive activity, 

volcanologist Johnston flew by helicopter to the crater rim and climbed 

down into the crater to collect samples 

of water from a small lake that had 

formed in the crater bottom. Formed 

by melting ice, the lake had a temperature of 17°C (62°F), and gas bubbled 

through it. Analyzed later, the sample 

of lake water was found to have a pH 

of 5.1 (slightly acid), 120 milligrams of 

chlorine per liter, and 32 milligrams of 

sulfur in the form of sulfate per liter. 

These analyses indicate that the water 

has a low to moderate concentration of 

dissolved minerals. The radioactive gas 

radon was present in the minor amount 

of 100 picocuries per liter, well within 

the range found in geothermal waters 

in other regions. 

USGS scientists, concerned over the 

increasing instability of the bulge area 

and the possibility that large avalanches of snow, ice, and rock could 

disrupt State Route 504 south and west 

of Spirit Lake, today issued an updated 

Hazards Warning to State and local officials and to the Forest Service. 

Governor Ray and the Forest Service's Forest Supervisor Robert Tokarczyk, acting on this and earlier hazard 

assessments, closed additional areas 

near the volcano to entry. A "Red 

Zone" (fig. 13) was established around 

the peak to distances ranging from 

about 3 to 8 miles and included the 

Spirit Lake area. Only scientists, lawenforcement officers and other officials, and search-and-rescue personnel are permitted in this zone. In a 

"Blue Zone," which extends beyond 

the Red Zone, logging operations are 

allowed to continue, and property 

owners holding special permits may 

enter, but no overnight stays are allowed. As an added precaution, 

Governor Ray also declared the entire 

State an emergency area because, 

under certain conditions, winds could 

scatter tephra from volcanic activity 

over hundreds of miles. 

Toutle Lake School, located about 

25 miles from the mountaintop, held a 

"volcano drill," the first of its kind in 

the United States. 

Despite the ominous bulging on its 

northern side, the mountain remains 

quiet as the month closes. The eruptions of March and April spread ash 

for at least 30 miles in every direction 

and as far as 60 miles to the southsoutheast and 70 miles to the north. So 

far, the ash has been derived from 

pulverized old rocks. Although 35 days 

have passed since the first eruption, no 

new lava has been seen or found in the 

ejected ash. 

The installation and use of instruments to measure and monitor the 

volcano have continued throughout 

the month. As April closes, the instruments being used to measure at 

various sites include: 

• Six 5-day seismic recorders 

operating within 10 miles of the summit of Mount St. Helens and 10 

telemetered seismometers within 35 

miles of the summit. Receiving and 

recording equipment at the University of Washington seismology center 

in Seattle has been expanded to handle the blizzard of data, and a computer link has been established with 

the USGS group in Vancouver to 

speed data transfer and communications between the two centers. 

• A network of five tiltmeter stations 

and their automatic telemetering instruments at distances ranging from 

less than 2 to about 9 miles from the 

summit. 

• Fourteen reflector-type surveying 

targets on the mountain, many of 

them precariously accessible only by 

helicopter, used in making precision 

measurements that detect changes 

such as slumping or swelling of parts 

of the volcano. Distances between 

base stations and the targets on the 

mountain are measured with a 

geodimeter (electronic laser instrument). Horizontal and vertical 

angles are measured with a 

theodolite (manual optical instrument). 

• A network of six gravity stations 

spread over the northwestern, northern, northeastern, and eastern sides 

of the volcano at distances ranging 

from less than 2 to about 5 miles 

from the summit. Each station is 

visited twice in a typical day, and 

the gravity is measured with one of 

three electronic-readout precision 

gravimeters. These measurements 

are repeatedly checked against measurements of presumed stable gravity 

made at a base station about 12 miles 

west of the summit. 

• Three recording magnetometers 

located northeast, east, and west of 

the volcano at an average distance of 

about 2.5 miles from the crater. 

Magnetic field intensity is automatically recorded on tape every 10 

minutes. 

• A preexisting network of hydrologic 

measuring sites expanded by the addition of 33 stream sites for collecting water-quality data (chemical, 

Chronology of the First 100 Days 35 
biological, and sediment characteristics) and monitoring changes in 

streamflow. Nineteen of these additional sites are on streams that drain 

Mount St. Helens; 14 are on other 

streams likely to be affected by ash 

from the volcano. Two of the additional sites have monitoring instruments that automatically send 

telemetered data by way of an orbiting Earth satellite to the USGS office in Tacoma. 

• Two time-lapse cameras that are 

making a photographic record 

(when visibility permits) of the eruptions and profiles of the volcano. 

Thursday, May 1 

E Day Minus 17 

As the month opens, the mountain is 

steaming continuously but otherwise is 

not erupting. USGS observers report 

that a small lake has formed again in 

the volcano's crater and has covered 

one of the steam vents and that gas 

bubbles up through the water. The 

most active steam vents, however, are 

above the lake surface on the southern 

side of the era ter. 

The swelling on the northern flank 

continues. One point on the bulge, according to measurements, moved 

about 2 feet outward in less than 12 

hours. 

Earthquakes, too, continue; 26 

stronger than magnitude 3 and 5 of 

magnitude 4 or greater were recorded 

today. 

A seismic station was installed today 

at Dogs Head to help detect earthquakes that might trigger a major 

avalanche and to improve the accuracy 

of earthquake location. Near the 

7,500-foot level, it is the highest instrument station on the mountain. 

Also today, a new observation station was established on a ridgetop east 

of the Coldwater I site and 2.7 miles 

closer to Mount St. Helens. The new 

site is between the valleys of the North 

Fork Toutle River and South Coldwater Creek, 5.7 miles north-northwest of the summit. It is at an altitude 

of about 4,100 feet-about 1,400 feet 

above the floor of the adjacent river 

valley. Automatic cameras, other 

monitoring equipment, and radios for 

communication have been moved there 

from Coldwater I. Also, a travel trailer 

has been brought in to shelter volcano 

watchers, who now are at the site 24 

hours a day. The new station is called 

Coldwater II (fig. 16). 

Friday, May 2 

E Day Minus 16 

The mountain is not erupting, 

although it continues to steam. Thirty 

earthquakes stronger than magnitude 3 

were recorded today, 8 of which were 

of magnitude 4.0 or greater. The bulge 

is growing outward at a rapid rate, as 

much as 5 feet a day near Goat Rocks. 

Scientists studying a thermal infrared survey made by personnel of the 

U.S. Naval Air Station at Whidbey 

Island, Wash., detected a previously 

unknown area of warm rock in the 

middle of the bulge on the northern 

slope of the volcano. Ice continues to 

break up in this area, which is about 

100 feet long and 50 feet wide. No one 

knows whether it is a new hot spot or 

one that existed before and has been 

hidden by a covering of ice. 

Skamania County Sheriff Bill Closner accused television newsmen of 

practicing "one-upsmanship" by flying 

helicopters into the volcano's dangerous Red Zone, according to an article in the Seattle Post-Intelligencer. 

He is quoted as saying, "The mountain 

is getting more dangerous all the time. 

It's getting to the point where somebody's going to get hurt, and we're going to arrest them .... " Most news 

reporters and photographers, however, seem to be responsible and law 

abiding in their efforts to present the 

Mount St. Helens story to the public. 

Some news teams have provided aircraft rides for scientists who otherwise 

would have had no access to the 

volcano area. 

Owners of some of the many summer cabins in the Spirit Lake area 

reportedly have refused to make their 

36 The First 100 Days of Mount St. Helens 

semiannual property-tax payments because they have not been allowed to 

use or even enter their property since 

the area was evacuated after the eruptions of March 27. 

Saturday, May 3 

E Day Minus 15 

The bulge continues to grow as Goat 

Rocks moves northward at an alarming rate. Although steam continued to 

issue from summit fumaroles today, 

there were no eruptions, and seismic 

activity was down-only 26 earthquakes of magnitude 3 or greater, including 5 exceeding 3.9. 

USGS scientists in Vancouver took 

time out from their measurements to 

discuss funding for the increasingly expensive volcano watch and whether 

some of them should return to their 

regular duties. Volcanologist Johnston, 

who normally is assigned to the Menlo 

Park office but who has been involved 

since the first earthquake on March 20, 

told newsmen, "We all want to stay. 

We don't want to be in California, 

Denver, or Virginia if something happens. I even offered to move here." 

Sunday, May 4 

E Day Minus 14 

The mountain remains quiet, and 

scientists were able to remeasure the 

bulge. They confirm that outward 

movement continues at a rate of about 

5 feet a day. USGS geologists are now 

convinced that some bulging of the 

northern flank resulted from a magmatic intrusion within the volcano during late March. They do not know yet 

whether the intrusion is still active or 

how much of the continuing change in 

the mountain's shape may be merely a 

gravitational spreading of the mountain accompanying the settling of the 

summit graben (fig. 14A). 

Volcanologist Johnston has been 

using a spectrometer, which measures 

the wavelengths of light components, 

to examine the makeup of the gases 

emanating from the crater. He uses the 

instrument at Timberline Viewpoint at 
midday when the sunlight shining 

through the gas is brightest. So far, he 

has not detected significant amounts of 

sulfur dioxide, which would indicate 

that the volcanic gases are from a hightemperature source. 

Monday, May 5 

E Day Minus 13 

Mount St. Helens continued to 

steam but did not erupt today. Smoke 

from the burning of timber slash 

(debris) led to rumors of lava flows, 

but there were none. Although strong 

eruptions of ash have not been common during the past 3 weeks, scientists 

do not think that the volcanic activity 

is subsiding yet. 

Jack Hyde, a Tacoma Community 

College geologist who has done extensive research on Mount St. Helens and 

has worked with USGS geologists on 

studies of other Cascade Range volcanoes, was interviewed today by 

reporter Jim Erickson of the Tacoma 

News Tribune. "I have a gut feeling . . . that as the bulge continues to 

grow, something dramatic is going to 

happen soon," Hyde said. He speculated that the instability of the northside bulge might result in massive landslides, which could be followed by a 

"spectacular" explosion of lava, 

possibly without warning, as lava 

vents on the northern slope are opened 

up. When he was told that scientists 

are watching the northern face of the 

volcano from nearby ridges, Hyde 

replied, "I hope they're not in a direct 

line. That's like looking down the barrel of a loaded gun." 

The frequency with which the 

famous Hawaiian volcanoes erupt and 

the type of lava flows that they produce have contributed to the popular 

belief that all volcanoes have fluid, 

channeled lava flows. Because of this 

notion and because Hawaiian volcanoes, being less explosive, are much 

safer than volcanoes like Mount St. 

Helens, some people who have visited 

Hawaii do not understand why scientists and officials are being so cautious. 

"We're logging 10 miles away from the 

peak," one logger was quoted as saying. "I don't see any hazard. I just came 

back from Hawaii, where they run 

tourist buses right up to the edge of a 

venting volcano." 

Tuesday, May 6. 

E Day Minus 12 

Athough clouds obscured the mountain most of the day, there was no 

reason to suspect that it had erupted. 

The northern flank continues to bulge 

at the rate of 4 to 5 feet a day; earthquakes continue at about the same rate 

as they have in recent weeks. 

The relatively gentle behavior of 

Mount St. Helens so far in this eruptive 

sequence makes it difficult for those 

who are unfamiliar with explosive 

volcanoes to realize the potential 

danger. For the last 2 weeks especially, 

the mountain has done nothing to convince a nonscientist that a volcanic 

hazard exists. If the scientific instruments were not measuring the ominous displacement of the bulge and if 

the news media were not reporting the 

scientists' concerns extensively, the 

public clamor to do away with the 

roadblocks and entry restrictions undoubtedly would be greater. 

Eruptive Activity 

Resumes 

Wednesday, May 7 

E Day Minus 11 

The volcano resumed activity after a 

lull of about 2 weeks, sending up eruptions of steam and ash late today as high 

as 13,000 feet. The northern flank of 

the mountain maintains its outward 

creep, but earthquakes are mostly of 

low magnitude. 

Some who are trying to carry on 

their daily lives in the shadow of the 

volcano find that their patience is 

wearing thin . Bombarded by rumors as 

well as official warnings, some 

residents say that they glance at "The 

Mountain" whenever they hear a 

noise. Several, according to reporters, 

wish that the volcano would "blow and 

get it all over with." One was quoted as 

saying, "Inflation and that damn 

volcano-it's a wonder we don't have 

ulcers." 

Thursday, May 8 

E Day Minus 10 

Muddy rain fell on the Timberline 

monitoring station today, and ash 

blew to the north and east as the mountain continued its sporadic eruptions. 

The crater steamed, as did areas near 

the head of Shoestring Glacier and the 

Boot, high on the eastern and northern 

sides of the cone, respectively. 

Many geologists agree that it is only 

a matter of time before the bulge area 

fails, probably in a gigantic landslide. 

They are unable to judge, however, 

when the failure is likely to occur. The 

strength of the rocks under the bulge 

and the depth to which they are affected by the deformation are not 

known. In the meantime, the northern 

flank continues its outward creep. 

Earthquake frequency is about the 

same as it has been in previous weeks 

(25 stronger than magnitude 3), but 11 

quakes stronger than magnitude 4 were 

recorded-the largest number of higher 

magnitude quakes since April 24. The 

strongest of these registered 5.0, the 

most powerful single quake to date. 

Harmonic tremor returned to the 

records for the first time since April12. 

Tremor was recorded in three bursts, 

from 4:43 to 5:03 a.m., 10:04 to 10:13 

a .m., and 10:03 to 10:12 p.m. 

Friday, May 9 

E Day Minus 9 

The mountain continues to behave 

as it did yesterday, sending up intermittent plumes of steam and ash, 

steaming continuously in the main 

crater, on the upper northern flank, 

and at the head of Shoestring Glacier, 

and bulging farther outward on the 

northern side. 

Seismicity, too, is about the same. 

Twenty-one earthquakes stronger than 

Chronology of the First 100 Days 37 
magnitude 3 were recorded, including 

nine that ranged from 4.0 to 4. 9, but 

no harmonic tremor was noted today. 

USGS scientists curtailed observations at Timberline Viewpoint because 

of the increasing danger that a sudden 

avalanche might reach that site. Many 

volcano observations now are being 

made at Coldwater I and Coldwater II, 

about 6 and 3 miles farther from the 

crater, respectively (fig. 7.) 

Saturday, May 10 

E Day Minus 8 

The volcano was under cloud cover 

most of the day, but erupting steam 

and ash could be seen when the clouds 

lifted. USGS scientists remeasured the 

bulge on the northern side when 

weather permitted and found that the 

rate of movement apparently has 

slowed to less than 3 feet a day-about 

half its average rate for the previous 2 

weeks. (The apparent low rate was 

later thought to be due to an erroneous 

measurement.) Seismicity continues at 

about the same level; of 20 events exceeding magnitude 3.0, 10 were magnitude 4.0 or greater. 

University of Puget Sound geologist 

AI Eggers told reporters that tideproducing gravitational forces will be 

exceptionally strong on May 21, and 

he warned that the extreme force might 

trigger a major eruption if the volcano 

were already set to erupt. Although 

most USGS geologists do not totally 

discount this idea, they believe that 

other factors, such as magmatic pressure inside the mountain, are likely to 

be much more important. 

Sunday, May 11 

E Day Minus 7 

Although the crater emitted only 

small bursts of steam and ash, 10 earthquakes of magnitude 4.0 or greater occurred again today. Increased steaming 

observed at the hot area on upper 

Shoestring Glacier may indicate 

changes in the distribution of heat inside the volcano, according to USGS 

volcanologist Johnston. 

Volcanic-hazard scientists and public safety officials are feeling the 

pressures of responsibility these days. 

They believe that the volcano is capable of producing dangerous avalanches, mudflows, and explosive 

eruptions, and they are striving to give 

realistic warnings and to provide adequate protection for the public. At the 

same time, they recognize that personal hardships and economic loss to 

local individuals and businesses could 

result from an overreaction to the 

hazards. 

Scientists hope to provide advance 

warning of any impending · disaster. 

They are watching the mountain closely from the observation post at Coldwater II, which is being manned 24 

hours a day. Also, a Forest Service 

observation airplane is in the air 

around the mountain almost continuously when weather permits. In addition, instruments such as the telemetering seismometers remain "on duty" and are closely monitored around 

the clock. Most USGS and University 

of Washington scientists who are studying the volcano believe that any major eruption would be preceded by a 

change in the seismic activity or in the 

rate of bulging; therefore, they believe 

that they can give adequate warning if 

a dangerous eruption occurs. If, 

however, earthquake patterns do not 

change before the onset of a major 

event-such as the expected massive 

avalanche-or if the event occurs when 

visibility is hampered by darkness or 

clouds, even scientifically trained 

volcano watchers may not be able to 

give warning. 

Monday, May 12 

E Day Minus 6 

The mountain continues to erupt ash 

and steam, and observers today could 

see a new cluster of fumaroles on the 

western rim of the crater. The bulge 

continues to move out in the same 

direction (fig. 17) at a rate of about 5 

feet a day. Scientists agree that the 

bulge poses a danger, but they still can38 The First 100 Days of Mount St. Helens 

not determine how extreme that danger 

is. 

Earthquakes stronger than magnitude 3.0 have increased over the past 

few days; of the 28 recorded today, 8 

exceeded 4.0. One earthquake of magnitude 5.0 triggered an 800-foot-wide 

debris avalanche that plunged more 

than half a mile down the northern 

flank of the mountain. The avalanche 

did not take the bulge with it, nor was 

it the huge avalanche that scientists anticipated. They believe that today's 

avalanche demonstrates the increasing 

instability of the northern flank and 

that it was just a sample of larger 

events to come. 

A University of Washington seismology group moved a portable 

seismic recorder from a station at Spirit 

Lake to a ridgetop location northeast 

of Mount St. Helens. A major avalanche probably would reach the Spirit 

Lake station and would destroy the instrument if it were to remain there. 

Tuesday, May 13 

E Day Minus 5 

Steam and ash continue to erupt, but 

the rate slackened in the afternoon. 

The eruption cloud rose only about 

3,000 feet above the crater, and most 

of its ash fell nearby. However, a false 

report (of unknown origin) that a 

"mammoth" eruption had sent ash as 

high as 18,000 feet above sea level 

caused the Federal Aviation Administration to issue a pilots' warning 

that an ash-plume area extended 20 

miles north-northeast of the volcano 

and was "of extreme hazard to 

aircraft." 

The pit at the head of Shoestring 

Glacier has enlarged, and steam emission from that site has increased. USGS 

observers reported also that new 

steaming areas have opened up on the 

western side of the mountaintop, just 

outside the crater rim. Geologists 

noted yellow-green encrustations on 

the old ash on the upper southern 

slopes of the volcano, probably from 

sulfur that was either deposited by the 

fumes or leached from the ash. Similar 
METERS 

3,000 

2,500 

2,000 

1,500 

SOUTH 

0 

I 

0 

I 

.5 

.5 

I 

Graben 

I 

1 MILE 

I 

EXPLANATION 

• .. August 16, 1979 

April 7, 1980 

May 12, 1980 

NORTH 

FEET 

10,000 

Postulated boundary of 8'

000 

dome-forming mass 

6,000 

1.5 KILO~ETERS 

~------------------------------------------------------~----------------~------~4,000 

FIGURE 17.- Profile drawing of Mount St. Helens showing the shape of the north-side bulge on May 12, 1980 (solid line), August 16, 1979 

(dotted line), and April 7, 1980 (dashed line). Diagram is modified from Moore and Albee (1981). 

encrustations have been seen for weeks 

within the crater and around the rim. 

Earthquake activity continued at a 

lesser rate; 21 events stronger than 

magnitude 3.0, including 6 of 

magnitude 4 or greater, were recorded. 

Scientists at Vancouver spent much 

of today quashing rumors about the 

exaggerated size of the ash plume and 

also about a nonexistent lava flow, 

which was reported to have been moving down the side of the volcano. 

Wednesday, May 14 

E Day Minus 4 

Although bad weather obscured the 

volcano more than half of today, 

observers did see some eruptions of 

steam and ash. They noted one new 

steaming vent between the two small 

peaks on and just north of the northern 

crater rim along part of the fault 

system on the northern side of the summit graben. Instruments show that the 

northern flank continues to swell at a 

rate of about 5 feet a day and that 

seismicity is about the same or slightly 

less than it has been in recent days. 

Scientists from Dartmouth College, 

who are cooperating with the USGS in 

studying gas from the volcano, report 

that sulfur dioxide (S02) is being 

emitted at rates of 10 to 20 metric tons 

a day during the eruptive pulses and 

about 1 ton a day between eruptions. 

These S02 rates are much higher than 

those estimated from samples collected 

on March 30 (0.3 ton a day). Because 

volcanic SQ2 requires a very hightemperature source, the increased 

emission of this gas might indicate that 

the magma is moving closer to the surface. 

Thursday, May 15 

E Day Minus 3 

The volcano was visible part of the 

day; USGS observers saw no eruptions, but they could see new ash on 

the southwestern flank. Some of the 

summit vents appear to be filled with 

fallen blocks of ice. 

The north-side bulge continues to 

shift outward at a rate of about 5 feet a 

day. Seismic activity included one 

earthquake of magnitude 4.8 early this 

morning. 

Mount St. Helens continues to attract the curious from around the 

world. Hard-pressed law-enforcement 

officers, unable to man roadblocks on 

the maze of logging roads around the 

mountain, can only check periodically 

for people trying to get around the barricades and locked gates for a closer 

look at the volcano. Many roadblocks 

have become places where visitors 

congregate-picnicking, socializing, 

photographing, or just waiting for the 

clouds to lift and for the volcano to "do 

something." Their vehicles often clog 

the very routes that they would need to 

escape an explosive eruption. 

Fifty days have now passed since the 

March 27 eruption, but no lava has 

been seen, and no evidence of fresh 

magma has been found in the ash. Even 

with the renewal of ash eruptions on 

May 7, the amount of tephra ejected 

since March 27 has not been great in 

comparison with that ejected during 

eruptions of other volcanoes in the 

Cascade Range or during previous 

eruptions of Mount St. Helens itself. 

Friday, May 16 

E Day Minus 2 

The lull in eruptions continues, and 

seismicity has remained at about the 

same level for the past few days. Today, there were 28 earthquakes 

stronger than magnitude 3.0; 10 

reached 4.0 or greater. No harmonic 

tremor has been recorded since May 8. 

Airborne observers could see clearly 

into the growing summit crater and 

Chronology of the First 100 Days 39 
A 

FIGURE 18.-A, This aerial photograph of the northeastern side of Mount St. Helens shows 

conditions on May 17, the day before the devastating eruption. This quiet scene belies 

the forthcoming lateral blast. Dark streaks on either side of Sugar Bowl are deposits 

from avalanches of ice and rock caused by earthquakes and the increased breakup of 

the northern slope. (Photograph by Robert M. Kimmel, USGS.) B, Named features on 

the mountain and the extent of the north-side bulge are shown on the accompanying 

sketch. 

40 The First 100 Days of Mount St. Helens 
noted that steam continues to ~manate 

from the summit area, particularly 

from a large fumarole on the southern 

wall and from a gradually enlarging pit 

at the head of Shoestring Glacier. The 

bulging northern side also was steaming today, especially on its higher 

parts. 

The volcano has changed shape considerably during the last week and a 

half. The northern and northwestern 

rims of the crater show abundant 

cracks, which have been partly filled 

by snow and ash; this area appears to 

be moving downward as a mass 

toward the crater. The bulge area, too, 

continues to be highly broken and 

distorted. 

Before dawn today, an aerial thermal survey of the volcano was made 

by the U.S. Department of Energy. 

Because the results of the survey were 

recorded as digi'tal data on tape, they 

are not immediately available for interpretation. 

Glaciologists set up a time-lapse 

camera on Dogs Head, 1 mile northeast of the mountain's crest, and aimed 

it at the growing bulge. The camera 

takes a picture every half hour and can 

operate for more than 5 days without 

being reloaded. 

Cabins and camps at Spirit Lake, at 

the foot of the volcano, have been 

deserted for the most part, as they are 

in the Red Zone. Yesterday and today, 

however, workers were allowed to 

remove equipment from the Boy Scout 

and YMCA camps along the lake. 

Owners of private property in the noentry zones are demanding similar access to the homes and cabins that they 

were forced to leave weeks ago. Some 

threatened to converge in numbers on 

the roadblocks and go through "come 

hell or high water." The penalty for being found in the zone without permission has been set at $500 or a 6-month 

jail sentence. 

The National Weather Service 

predicts good weather for volcano 

watching this weekend. 

Saturday, May 17 

E Day Minus 1 

No ash erupted from the mountain 

today, but the bulge on the northern 

side continues to expand (fig. 18). 

Seismic activity decreased to its lowest 

level this month, which is only slightly 

lower than the May 7 level. Eighteen 

earthquakes stronger than magnitude 

3.0 were recorded today, six of which 

were of magnitude 4.0 or greater. 

Responding to pressure from property owners and with Governor Ray's 

consent, law-enforcement officers today escorted about 50 carloads of 

property owners to their property in 

the Red Zone to retrieve some of their 

possessions. Those who entered the 

zone were required to sign liability 

releases at the road barricades and to 

be back out by nightfall. Authorities 

have agreed to allow a second caravan 

of property owners to go in at 10 a.m. 

tomorrow, if the mountain remains 

quiet. 

At least two people have remained in 

residence in the restricted zones. Harry 

Truman, proprietor of the Mount St. 

Chronology of the First 100 Days 41 
FIGURE 19.-This aerial view of Spirit Lake, seen from the southeast on the morning of May · 

18, is probably the last photograph taken of this popular recreation area before the 

devastating eruption. At the left end of the lake is Mount St. Helens Lodge, where proprietor Harry Truman presumably was buried a few minutes later beneath hundreds of 

feet of avalanche debris. (Photograph copyright 1980 by Keith and Dorothy Stoffel.) 

Helens Lodge (fig. 19), has stayed in his 

home at Spirit Lake (in the Red Zone) 

in defiance of government authorities 

and the threatening volcano and has 

become something of a folk hero in the 

process. Ray Jennings also has not left 

his cabin in the Blue Zone near Swift 

Reservoir (fig. 13). Because the road 

barricades are not difficult to evade, 

the number of others in the restricted 

zones is not accurately known. 

"No one would listen," Skamanian 

County Sheriff Closner was later 

quoted in the Vancouver Columbian as 

saying. "It didn't matter what we did. 

People were going around, through, 

and over the barricades. Some were 

climbing right up to the rim of the 

crater. Maps were even being sold 

showing back-country roads around 

the barricades." 

One man will be in the Red Zone 

legally tonight. He is volcanologist 

Johnston, who today took up duties at 

the USGS Coldwater II observation 

post 5.7 miles north-northwest of the 

summit of Mount St. Helens. Johnston 

is taking instrument readings of the 

distances to targets on the swelling 

bulge and radioing them to the 

volcano-watch headquarters in Vancouver. He also has been gathering information about the volcano's condition by studying the volcanic 

gases-his scientific specialty (fig. 20). 

He will be alone at the ridgetop site 

overnight but expects to be joined in 

the morning by other USGS staff 

members. Johnston is taking over for 

geology student Harry Glicken, an intermittent USGS employee who has 

been at Coldwater II most of the time 

since May 1 but who left at 9 p.m. 

tonight to participate in a required college field trip. Geologists Daniel Miller 

and Donald Swanson plan to visit 

42 The First 100 Days of Mount St. Helens 

Coldwater II tomorrow to change film 

in the time-lapse cameras and to pick 

up a geodimeter. They expect to leave 

Vancouver about 8 a.m. Normally, the 

trip could be made in a few minutes in 

a charter helicopter. Tomorrow, 

however, the helicopter will not be 

available, so they face a 2-hour trip by 

automobile. 

On the next ridgetop beyond 

Johnston's is the post of Gerald Martin, 

a retired Navy radioman from 

southern California, who is one of a 

team of amateur radio operators serving as volunteer volcano watchers for 

the Washington Department of 

Emergency Services. Martin will spend 

the night in his radio-equipped camper 

at a site just outside the northern boundiary of the Red Zone, less than 2 miles 

north of the Coldwater II observation 

station and about 7 miles north of the 

volcano's top. 

Also staying near the volcano, but 

not inside the restricted zone is Reid 

Blackburn, a staff photographer for the 

Vancouver Columbian. Blackburn is at 

the Coldwater I observation post, 

which is 8.4 miles northwest of the 

mountain's summit and 2.4 miles west 

of the present Red Zone boundary. 

Blackburn will stay overnight to record 

images of the mountain at intervals 

during the night and also to 

photograph it in the clear light of early 

dawn. Two of his colleagues, Fred 

Stocker and Jim McWirter, who also 

have been camping at Coldwater I, 

went into Vancouver and "on a whim" 

have decided to remain in the city 

overnight. 

FIGURE 20.-A, On May 17, volcanologist 

David Johnston collected gas samples 

from a fumarole .recently found high on 

the unstable north-side bulge (shown by 

the arrow). (Photograph by David 

Frank.) B, Johnston and assistant Harry 

Glicken were lifted by helicopter to a 

precarious landing site nearby. C, 

Johnston scrambled over the chaotic rock 

mass to crouch at the edge of the 

fumarole and collect the samples. 

(Photographs by Harry Glicken.) 
Chronology of the First 100 Days 43 
In eastern Washington, everyday activities are going on with little or no 

concern for the increasing instability of 

Mount St. Helens. In Spokane, 

Washington's third largest city, the annual Lilac Festival has brought an influx of visitors to the city. Fair weather 

is expected for tomorrow's festivities, 

after which many people will be traveling homeward. 

In the farming area around Ritzville, 

the winter wheat is about 20 inches 

Cataclysmic Eruption 

Sunday, May 18 

E Day 

Today began free of clouds and so 

quietly that some scientists delayed 

planned reconnaissance flights over the 

mountain. Seismicity during the early 

morning was moderate, about the 

same as it has been in recent weeks. 

The Oregon Army National Guard 

flew over the volcano before dawn to 

make a thermal survey. The infrared 

scanner in the aircraft recorded the 

relative temperatures of the volcano's 

surface on photographic film, which 

was processed in a matter of hours 

after the plane landed. 

In Yakima, the sky was almost 

cloudless. Keith and Dorothy Stoffel, 

geologists working in the Spokane 

area, were visiting Yakima to attend a 

meeting. They decided to charter an 

airplane and fly to Mount St. Helens to 

photograph and observe the volcano. 

At about 7:15a.m., they took off from 

Yakima airport with pilot Bruce 

Judson. 

At 8:30a.m., some campers north of 

the mountain were up and enjoying a 

clear blue sky and warm gentle breezes 

from the west; others were still in their 

tents and sleeping bags. Fishermen, a 

few loggers, and other early risers had 

long been on the move. Several 

volunteer volcano watchers and 

amateur radio operators were at their 

posts. Some photographers, cameras 

cocked, were already awaiting the 

high. Although spring has been cooler 

than normal this year, good crop yields 

are expected because precipitation has 

been abundant, and the soil is moist. 

At Yakima, the late spring has delayed crops, but the blossoms are gone 

from the extensive orchards now, and 

the tiny fruit is beginning to form. The 

alfalfa crop is good; the first cutting of 

hay is about 5 percent complete, and 

the rest of the fields are about ready to 

cut. 

mountain's next move. The Stoffels 

and pilot Judson were in the air over 

the volcano. In Yakima, Robert L. 

Washburn, geologist for the Washington Department of Transportation, 

and his friend Chris Linschooten 

started on a morning run along a road 

west of the city. 

At Coldwater II, Johnston had 

already made two sets of laser 

measurements to the growing bulge 

and had transmitted the last data to 

Vancouver at about 7:00a.m. 

The quiet was ended abruptly at 8:32 

a.m. by an earthquake of about 

magnitude 5.1, the first in a day-long 

series of sharp quakes and seismic 

noise "like we'd never had before." 

That earthquake started a chain of 

events that was to leave the mountain 

and its surroundings drastically 

changed and was to claim the lives of 

about 60 people. 

The earthquake shook the walls of 

Mount St. Helens' summit crater and 

started many small avalanches. Then, 

a huge slab of the northern slope of the 

volcano in the area of the bulge began 

to separate from the main cone along a 

crack across the upper part of the 

bulge. As this immense mass of rock 

and ice plunged northward, small, 

dark clouds emerged from the base of 

the slide, followed closely by vertical 

plumes of steam and ash from the 

era ter area. 

As the huge avalanche raced down 

the volcano's lower flank, black clouds 

grew from the scar of the mountain44 The First 100 Days of Mount St. Helens 

The Army National Guard's 116th 

Air Cavalry Squadron is also in the 

Yakima area with its helicopters for 

summer field training. 

Nearer to Mount St. Helens, about 

30 ships are expected to depart at the 

busy ports of Vancouver and Portland 

in the next day or two and head down 

the Columbia River for the Pacific 

Ocean. About 20 incoming ships are 

expected to steam upriver to these 

same port facilities. 

side. Within seconds, as more of the 

northern flank slumped downward, 

these clouds developed into a large 

blast, directed outward, that became a 

devastating hurricane of ash and 

coarser fragments. The avalanche, 

now outdistanced by the lateral blast, 

slammed into a ridge about 5 miles 

north of the old summit, forming a 

hummocky debris flow that overtopped the ridge at one place but mostly turned to flow westward down the 

valley of the North Fork Toutle River 

as far as 14 miles. Farther east, part of 

the avalanche debris dived into Spirit 

Lake, where it displaced the water as a 

huge swash onto adjacent slopes, 

buried countless trees already blown 

into the lake, and raised the lakebed by 

more than 200 feet. 

The major lateral blast probably 

began about 20 to 30 seconds after the 

triggering earthquake and spread 

northward at remarkable speed. 

Seventy-seven seconds after the earthquake began, a seismic station about 

3.5 miles from the blast origin stopped 

sending signals to the University of 

Washington seismology center, presumably when the instrument was hit 

by the blast. That timing suggests an 

outward speed of 220 to 250 miles an 

hour for the debris-laden blast cloud. 

Johnston was among the first to see 

the avalanche and the beginning of the 

eruption. He probably was outside his 

trailer making measurements to the 

mountain and recording data. He 

grabbed his radio. "Vancouver, Van-
couver, this is it," he shouted-then, as 

the black, hot cloud of the lateral blast 

raced toward him, a final transmission, 

too garbled to be understood. 

The center in Vancouver did not 

receive his warning; atmospheric 

disturbance caused by the eruption 

probably blocked the radio signals. 

Johnston's message was received instead on the radio of a private citizen 

and recorded on an attached tape 

recorder. 

A more detailed warning came from 

volcano watcher Martin on the 

ridgetop north of Coldwater II. When 

the action started, he coolly radioed a 

description of the avalanche, the beginning of the eruption, and the progress 

of the blast cloud. 'The camper and the 

car just over to the south of me [Coldwater II] are covered," he reported. "It 

[the blast cloud] is going to get me, 

too." He was right. There was no 

escape from his position. 

No one could see what was happening within the spreading dark hurricane, but later observations showed 

that the blast had spanned an area 

north of the crater in an arc of nearly 

180°, which measured 23 miles across 

from east to west and extended from 

the mountain crest northwestward for 

about 18 miles. Within that area was 

an inner zone nearly 6 miles wide in 

which almost all life was destroyed. 

Trees were stripped of their branches 

and snapped off near the ground or 

uprooted, and vehicles were overturned. In an area rimming that zone 

and extending to near the edge of the 

blast area, trees were mostly denuded 

and toppled; on the outer limit, trees 

were left standing but seared. 

How hot the blast was can only be 

estimated by its effects; melted plastic 

and charred wood found in its path 

suggest temperatures as high as 680°F 

(360°C). Later, scientists made a preliminary estimate that the energy of the 

blast was equivalent to at least a few 

megatons of TNT and greater than the 

first atom bomb, although the sustained volcanic explosion was entirely 

different in character 

VIEW FROM ABOVE 

The Stoffels watched and photographed the beginning of the eruption 

from the air, narrowly escaping the initial blast and the rapidly spreading ash 

cloud. Here is their story (Korosec and 

others, 1980): 

"At about 7:50 a.m., we entered 

(with permission) the restricted air 

space around Mount St. Helens from 

the northeast and began our first pass 

in the clockwise direction. We were immediately impressed and surprised by 

the wet appearance of the north face. 

We circled above the base of the 

volcanic cone, at an altitude of about 

11,000 feet, taking photographs. The 

mountain looked serene, with only 

very minor wisps of steam blowing 

toward the north and west. Striking 

features on the north side of the mountain included large wet areas glistening around Goat Rocks and Sugar 

Bowl, where small avalanches had 

kicked up rocks and snow. The 

reddish-brown debris flows surrounding the two domes contrasted sharply 

with the lighter color of surrounding 

slopes. We wondered if these flows 

were very recent features and if they 

were hours or days old. 

"After we had completed the first 

pass, we began the second from the 

north-northeast, with a tight bank and 

a pass directly over the south side of 

the summit crater, at an altitude of 

about 11,000 feet. Again we were impressed by the serenity of the scene 

below. Activity included very minor 

steaming from a vent at the bottom of 

the main crater and from a small hole 

on the southeast side of the top surface 

of the raised southern lip of the crater 

[fig. 21B]. We saw numerous wet seeps 

on the north-facing wall of the main 

era ter, and a small lake had formed on 

the crater floor just below this area. As 

we continued westward across the 

crater's edge, we noted the immense 

fractures on the top of the south lip. 

"After we circled around to the 

north, we began a third pass along the 

same path followed in the previous 

pass, crossing directly over the summit. We didn't notice anything different, but the pilot thought he noticed 

more extensive cracking. 

"The fourth pass began with a wide 

sweep to the northwest to get a better 

overview of the entire mountain. We 

circled clockwise at a distance of about 

5 or 6 miles from the summit, passing 

over the northern end of Spirit Lake, 

and viewing each of the flanks as we 

continued the circular path. We turned 

sharply on the west side of the crater, 

intending to pass over the summit and 

continue east back to Yakima. 

"As we approached the summit, flying at an altitude of about 11,000 feet, 

everything was as calm as before. Just 

as we passed above the western side of 

the summit crater, we noticed landsliding of rock and ice debris inward 

into the crater [fig. 21C]. The pilot 

tipped the wing towards the crater, 

giving us a better view of the landsliding. The north-facing wall of the 

south side of the main crater was 

especially active. 

"Within a matter of secondsperhaps 15 seconds-the whole north 

side of the summit crater began to 

move instantaneously. As we were 

looking directly down on the summit 

crater, everything north of a line 

drawn east-west across the northern 

side of the summit crater began to 

move as one gigantic mass. The nature 

of movement was eerie, like nothing 

we had ever seen before. The entire 

mass began to ripple and churn up, 

without moving laterally. Then the entire north side of the summit began 

sliding north along a deep-seated slide 

plane [figs. 21D, E, F]. We were 

amazed and excited with the realization that we were watching this landslide of unbelievable proportions slide 

down the north side of the mountain 

toward Spirit Lake. We took photographs of this slide sequence occurring, 

but before we could snap off more than 

a few pictures, a huge explosion 

blasted out of the landslide-detachment 

plane [fig. 21G]. We neither felt nor 

heard a thing, even though we were 

Chronology of the First 100 Days 45 
46 The First 100 Days of Mount St. Helens 
FIGURE 21. - Aerial closeups of the earthquake-triggered landslide 

and the beginning of the devastating May 18 eruption of 

Mount St. Helens. (Photographs copyright 1980 by Keith and 

Dorothy Stoffel.) A, The airplane carrying geologists Keith 

and Dorothy Stoffel skirted the northern side of the crater during the earthquake that triggered the huge north-side avalanche and the start of the May 18 eruptions. Symbols show 

the approximate flightpath and positions of the airplane when 

the accompanying photographs were taken. B, View from a 

position about 1,000 feet higher than the northwestern lip of 

the summit crater, less than 1 minute before the major eruption. The crater was serene, and there was little steaming. A 

fumarole in the Notch (fault trench) north of the crater was 

fuming only enough to show a slight haze. C, As the airplane 

passed just north of the crater, a strong earthquake started 

avalanches of ice and rock debris on the southern wall of the 

crater, seen here from the northeast, and also triggered a huge 

avalanche on the northern side. When this photograph was 

taken, the area shown in the lower right was "rippling and 

churning in place" but had not yet slumped downward. A puff 

of steam that had appeared from the Notch fumarole (shown 

by an arrow) also shows clearly in D, E, and F. D, This view 

westward across the upper northern side of the crater stops the 

action as a large slab of the mountainside was dropping to the 

north and forming an avalanche tongue. The slide mass has 

detached from a steep slide face , seen here from the edge, to 

the right (north) of the steaming Notch area (shown by an 

arrow). Fuming from the slide face also had begun. The northwestern rim of the crater is seen in the upper left of this 

photograph, and the eastern part of the South Fork Toutle 

River valley is in the upper center. E, Moments later, the slide 

mass had moved farther down and toward the north (right), 

and a second slab had begun to slide down after the first. Fume 

emission increased from the slide face and Notch areas. The 

first dark ash plumes were seen starting from the lower edges 

of the slide face - one above and to the left of center in this 

view and the other at the bottom edge to the right of center. F, 

The initial slide mass had moved even farther down, and the 

entire remaining mass of rock and ice north of the crater rim 

(upper left) had begun to slump as this picture was taken. 

Fume and ash eruptions were beginning from the slide face, the 

Notch area, and the bottom of the crater itself (just out of view 

at the upper left). G, The eruption cloud grew from emanations from the north-side slide face , the former Notch area, 

and the bottom of the crater. These sources determined the 

initial shape of the eruption cloud, here partly hidden from 

view (see figs. 23 and 24). H, Although the vertical crater 

plume appeared almost stationary, the lateral cloud grew 

quickly and violently. Note the projectiles (rock and ice) being 

thrown to the north (right of this view). I, This view, 

photographed shortly after H , shows slight further growth of 

the vertical plume. At this point, the darker cloud (right) was 

becoming the upper part of the rapidly expanding lateral blast 

(see figs. 23, 24, 25, and 26). The Stoffels had used all their 

film, and the pilot opened the throttle and dove the airplane to 

escape the expanding blast cloud. 

Chronology of the First 100 Days 47 
Coldwater I 

Blackbu rn X 

X 

Rogers 

and t he 

Kea rneys 

MwHI •k~ 

Lan dsburg 

River X 

~~~ 

ZI::J ::Jo 

Ou 

1--Z ~ ::::i( <t 

~,2 o<t 

u~ (f) 

I 

I 

0 1 2 3 4 

X Mart in 

o Ryan Lake 

X Rosenqu ist 

and 

Ronnholm 

Spirit Lake 

10 MILES 

10 15 KILOMETERS 

FIGURE 22.-Sketch map of the Mount St. Helens area showing where some of the victims of 

the May 18 lateral blast and some of the photographers contributing to this report were 

located. (Modified from Cummans, 1981.) 

just east of the summit at this time. 

Dorothy saw the southern portion of 

the summit crater begin to crumble and 

slide to the n9rth just after the initial 

explosion [fig. 211]. 

"From our viewpoint, the initial 

cloud appeared to mushroom laterally 

to the north and plunge down. Within 

seconds, the cloud had mushroomed 

enough to obscure our view. At about 

this time, the realization of the enormous size of the eruption hit us, and 

we focused our attention on getting out 

of there. The pilot opened full throttle 

and dove quickly to gain speed. He 

estimated that we were going 200 

knots. The cloud behind us mushroomed to unbelievable dimensions 

and appeared to be catching up with 

us. Since the clouds were billowing 

primarily in a northerly direction, we 

turned south, heading straight toward 

Mount Hood. 

"After a couple of minutes, we felt 

sure we had outrun the clouds. Behind 

us, we could see the clouds continue to 

mushroom to the north and northwest. 

An ash cloud rolled across the summit 

and down the south face, completely 

enveloping the cone and eventually 

obscuring all but the lower slopes. The 

pilot suggested turning west and flying 

around the west side of the cloud, but 

after we thought about it briefly, we 

48 The First 100 Days of Mount St. Helens 

realized that the billowing clouds were 

moving west faster than we could fly. 

To the east of the volcano, the ash 

cloud separated into billowing, 

mushroom-shaped clouds and a higher 

overhang of cirrus-type clouds. Ashfall 

from the mushroom-shaped clouds was 

heavy. Lightning bolts shooting 

through the clouds were tens of 

thousands of feet high. Soon, the ash 

extended to altitudes higher then 

50,000 feet. 

"We thought about flying back to 

Yakima and even turned to the east 

briefly, but again we decided against it, 

realizing we could never beat the ash 

cloud. Sometime between 9:00 and 

9:15 [a.m.] we landed at a Portland airport." 

VIEW FROM THE WEST 

Ty and Marianna Kearney were at a 

ridgetop site 7.6 miles west of the summit outside the restricted zone (fig. 22). 

Like Martin, they were amateur radio 

operators serving as volunteer volcano 

watchers, and they had been living in 

their camper van at that site for nearly 

a week. Also at the viewpoint that 

morning was sightseer Robert Rogers. 

The triggering earthquake drew their 

attention to the peak; they then 

watched the avalanche and the growing eruption plumes in profile. 

Rogers ran for his camera, which 

was about 60 feet away, and began 

taking pictures (fig. 23). He was able to 

expose only a few frames during a span 

of perhaps 15 seconds before his 

camera jammed. 

Kearney radioed a warning about 

the eruption and then began using his 

camera, taking his first picture (fig. 

24A) several seconds after Rogers' 

camera failed. The observers heard a 

roaring sound as the laterally directed 

cloud began to roll down the mountain, and they could see fires starting as 

lightning in the cloud ignited trees. 

They drove southward to safety by 

roundabout logging roads as winds 

generated by the eruption rocked their 

vehicles. 
E 

FIGURE 23.-These photographs of the 

early part of the May 18 eruption were 

taken from a ridgetop 7.6 miles west of 

Mount St. Helens. The photographer felt 

the triggering earthquake, saw the beginning of the erup,tion, and operated his 

camera as fast as possible (manually) until it jammed after he took the last picture 

shown here. He estimated that this sequence required about 15 seconds. Even 

at this early stage of events, the front of 

the avalanche was already out of sight 

below the horizon to the left of the large, 

streaked hump (which probably was a 

dust cloud). Marianna Kearney, a 

volunteer observer and radio operator 

stationed at the site, is in the right 

foreground near her camper van. (The 

earlier development of this avalanche is 

shown in fig. 21.) These pictures also 

show the growth of both a lower and an 

upper laterally directed eruption cloud. 

Similarities in the sizes and shapes of the 

eruption clouds show that the second picture in this sequence must have been 

taken at about the same time as figure 

21G. (Photographs copyright 1980 by 

Robert Rogers.) 
B . 
FIGURE 24.-This sequence of photographs, which, like that in figure 23, was 

taken at a site 7.6 miles west of the summit of Mount St. Helens, picks up shortly 

after the sequence shown in figure 23 

leaves off and covers a time interval of 

about 15 seconds. It shows the further 

development of the north-directed blast. 

The panoramic photograph (C) spans an 

arc of about 90 °. Mount Rainier is at the 

lower left edge; the site of Coldwater II is 

in the lower center of the left half, 

obscured (and probably already demolished) by the rapidly expanding lateral 

blast cloud. The photographs were taken 

by Ty Kearney, an amateur radio 

operator and volunteer volcano observer 

for the Washington State Deparment of 

Emergency Services. Observers at the site 

distinctly felt the earthquake that triggered the huge debris avalanche 

preceding the eruption. (Photographs 

copyright 1980 by Ty and Alan 

Kearney.) 
A 

D 

52 The First 100 Days of Mount St. Helens 
VIEW FROM THE 

NORTHEAST 

At Bear Meadow, about 11 miles 

northeast of the summit of Mount St. 

Helens (fig. 22), Gary Rosenquist, an 

amateur photographer, and Keith 

Ronnholm, a graduate student in the 

University of Washington Geophysics 

Program, were camped within a few 

hundred yards of each other, along 

with several other parties of campers. 

Earlier in the morning, Rosenquist had 

mounted his camera on a tripod and 

aimed it at the volcano . Thus 

prepared, he was able to begin taking 

pictures as soon as he realized that a 

huge avalanche was occurring. After 

takiing the remarkable sequence of 

eruption photographs shown in figure 

25, he snapped a few more pictures, 

warned other campers who had not yet 

stined, and drove his vehicle to safety 

northward of the blast zone. 

Ronnholm was in his camper when 

the avalanche began, and he estimates 

thalt he did not start taking pictures 

(fig. 26A) until about 10 seconds after 

the eruption began (compare figs. 26A 

and. 25G). He waited, taking more pictun~s from the same site and expecting 

the blast cloud to be stopped or 

divt~rted upward by r1dges closer to the 

volcano. When the turbulent gray 

FIGURE 25.-This remarkable sequence of 

photographs was taken by Gary Rosenquist, who was camped at Bear Meadow 

about 11 miles northeast of the 

summit of Mount St. Helens. On the 

morning of May 18, he had mounted his 

camera on a tripod and was thus well 

prepared to record the fast-moving 

events that began at 8:32 a.m. These 

photographs (copyright 1980 by Gary 

Rosenquist) are estimated to span about 

20 seconds. A, This photograph was 

made at about the same time that Keith 

Stoffel, flying above the volcano, was 

taking the picture in. figure 21E, looking 

down the avalanching northern face of• 

the mountain. At this early stage, the 

summit eruption cloud was just beginning to emerge. The first huge avalanche 

mass was roaring northward; its front 

was already below the crest of the 

timbered ridge (lower right), and a second slab of the mountain's northern side 

was beginning to slump. The beginning 

of the lateral blast is shown here by small 

black eruption clouds on the left- and 

right-hand sides of the scarp left by the 

avalanches. B, and C, In these views, the 

second large slab from the upper northern side was falling and also was beginning to be blown apart by the lateral 

eruption, and the eruption plume from 

the summit area was rising rapidly. The 

left-hand (eastern) side of the avalanche 

mass consisted largely of ice from the 

Forsyth Glacier (white area in left center 

of both views), which was flowing 

around a dark rock obstruction. (Compare with ice extent in A.) D, E, and F, 

Both the vertical and the lateral eruption 

clouds enlarged rapidly as the avalanche 

mass moved downward and to the north 

(right). D stops the action during the collapse of the entire remaining upper northern side of the mountain. At about the 

same instant, Robert Rogers was taking 

his first picture (fig. 23A) from the west. 

G, The forceful blast cloud overtook the 

trailing edge of the avalanche mass and 

may have boosted its upper part (lower 

right) in its northward rush. H , By the 

time that this picture was taken, the 

upper (darker) and lower parts of the 

lateral blast had merged, and the blast 

was in full force. Most of the upper 

northern side of Mount St. Helens was 

involved. Large blocks of rock and ice 

(right center) were thrown through the 

air to the north. 

Chronology of the First 100 Days 53 
FIGURE 26.-Ground views of the rapidly 

expanding lateral blast cloud of the May 

18 eruption. (Photographs copyright 

1980 by Keith Ronnholm, University of 

Washington Geophysics Program.) A, 

View from about 11 miles northeast of 

the summit (from Bear Meadow), where 

geophysicist Keith Ronnholm began 

taking pictures about 10 seconds after the 

eruption began. The front of the avalanche was already out of view behind 

the ridge at the lower right; the upper and 

lower lateral eruption clouds (figs. 23 and 

24A) were merging as they grew. B, 

Telephoto view from the same spot about 

4 seconds later (about 14 seconds after 

the eruption began), taken at nearly the 

same instant that figure 25H was taken. 

Note the streaming projectiles (blocks of 

ice and rock) being thrown beyond the 

eruption cloud to the right. 

B. 

A 

54 The First 100 Days of Mount St. Helens 
cloud continued rushing toward the 

camp about 90 seconds after the eruption began, he took one more picture 

(fig. 26C) and began driving northward to outrun the cloud. Keeping 

barely ahead of the menacing hot 

cloud, he stopped about 3 miles farther 

from the mountain to take a picture of 

the towering front of the cloud (fig. 

26D). About 8 minutes after the eruption began, airborne ash from the 

volcano was streaming eastward with 

the wind (fig. 26E). By that time, 

lightning was flashing, and thunder 

was a constant rumble. Shortly 

thereafter, rocks the size of golf balls 

began to fall on him. Ronnholm's vehicle was soon engulfed in an ashfall so 

thick and so dark that he could continue driving only by following .a logging truck that was being guided by 

men walking ahead to feel out the 

road. 

FIGURE 26. - Continued. C, The blast 

cloud quickly obscured the mountain and 

expanded northward. Ronnholm waited 

at the same site, expecting the cloud to be 

stopped or diverted upward by ridges 

between him and the volcano (A) . When 

the cloud continued to expand beyond 

the first ridge and then the second and 

was still rushing toward him, he took this 

photograph (about 90 seconds after the 

eruption began) and then began driving 

his vehicle northward to outrun the 

cloud. D, Keeping barely ahead of the 

towering hot cloud, Ronnholm stopped 

about 3 miles farther from the mountain 

(about 6.5 minutes after the eruption 

began) and took this photograph by aiming his camera upward between trees. E, 

This photograph, taken toward the south 

from the same site about 1.5 minutes 

later, shows clear sky below the ash 

cloud, which by then was streaming 

eastward with the wind. (The volcano is 

to the right "about two photo widths.") 

By this time, lightning was flashing, and 

thunder was a constant rumble. Amid a 

shower of golf-ball-sized rocks and ash so 

thick and dark that he could barely see, 

Ronnholm escaped to the north. 

Chronology of the First 100 Days 55 
VIEW FROM THE 

NORTHWEST 

Marshall Huntting was up early at 

his home about 30 miles northwest of 

the mountain near the town of Silver 

Creek, Wash. (fig. 13). A former State 

Geologist, he was very interested in the 

volcano and had been observing it intently through binoculars during the 

past weeks as weather permitted. 

When he learned of the eruption, he 

made a hasty start in his car toward a 

nearby hill where he and his neighbors 

had watched previous eruptions of 

steam and ash. After a spinout at a 

road intersection, he got his car back 

on the road and arrived at the hilltop in 

time to see a widespread vertical eruption cloud rising to an amazing height 

and a ground cloud (from the lateral 

blast) spreading westward, apparently 

following the valleys of the North Fork 

Toutle River or the Green River or 

both. At about 8:42a.m., the westward 

front of the ground-hugging cloud appeared to stop at a position about 2 

miles upstream (southeast) from Camp 

Baker (fig. 22). Thereafter, the ground 

cloud seemed to be "sucked up into the 

vertical ash plume" rising toward the 

stratosphere. 

About 20 minutes after the eruption 

began, observers at Silver Creek saw a 

second ash cloud rise from the direction of Mount St. Helens and begin 

moving westward near the ground, as 

the first cloud had. They could not see 

whether the second cloud originated at 

the volcano or was some kind of aftereffect of the original lateral blast. 

About 10 minutes after the second 

cloud appeared, the observers saw a 

·. · white halo forming and rising around 

the vertical eruption plume from the 

volcano (fig. 27A). They noted that the 

second ground-hugging cloud extended 

even farther west than the first; according to Huntting, it stopped slightly 

west of the direction of Camp Baker, at 

about 9:30 a.m. (fig. 27B). Thereafter, 

the lower cloud seemed to settle rather 

than to rise. Part of it moved northwestward out of the Green River 

valley, crossed the Cowlitz River, and, 

at about 10:15 a.m., stopped at Silver 

Creek, the northwesternmost extent of 

ashfall from this eruption. The higher 

ash cloud gradually drifted eastward as 

the volcano continued its upward eruption, and the western side of the 

volcano was clearly visible (fig. 28). 

OTHER OBSERVATIONS 

After watching the "slow-motion" 

beginning of the eruption, other 

observers sought escape as the lateral 

blast cloud sped outward to the north 

and overtook dozens of people in a 

wide area. Some survivors told of racing their automobiles at breakneck 

speeds along mountain roads to escape 

the turbulent dark cloud. 

At least one couple, however, drove 

to the mountain after they heard about 

the eruption. They avoided roadblocks 

and drove as far as they could up a logging road. Three miles from the mountain, their car was disabled by volcanic 

ash. Luckily, a passing helicopter crew 

spotted them and flew them to safety. 

A party of 12 climbers had z:isen 

early to ascend Mount Adams, 34 

miles east of Mount St. Helens. They 

had reached the false summit, at an 

elevation of 11,800 feet, when the 

eruption started. Within 10 minutes, 

they · felt a "heat wave" -a rise in 

temperature of 30 ° to 40 op 

(17° 22 °C)-that lasted several 

minutes. Afterward, a gray cloud cut 

off tP.e sun, and the atmosphere 

becanl.e charged with electricity. 

The climbers heard no sound from 

the ~ruption, nor did observers at 

Silver Lake, 30 miles west of Mount St. 

Hele~s, but others 18 miles northeast 

of the mountain heard a rumbling that 

sounded like a large avalanche 1 or 2 

minutes after the first dark eruption 

cloudi rose. The sound of the initial explosion was heard distinctly in northwestern Washington and southern 

British Columbia in Canada. Instruments at the National Oceanic and 

Atmospheric Administration laboratory in Silver Spring, Md., detected an 

56 The First 100 Days of Mount St. Helens 

atmospheric wave 3 hours and 20-

minutes later; in another 10 minutes, 

instruments at Columbia University's 

Lamon_t-Doherty Geophysical 

Observatory in New York registered it. 

The average speed of the wave traveling across country was nearly 700 

miles an hour. 

Seismograph records show that the 

triggering earthquake came from a 

depth of roughly 1,000 feet below sea 

level and from a point about 1 mile due 

north of the summit. The initial quake 

was followed about 2 minutes later by 

a second earthquake of roughly the 

same magnitude (about 5). Strong 

seismic signals were recorded for 

another 10 minutes (until 8:44 a.m.); 

then, seismic activity was relatively 

low for the following 3 hours. At 11:40 

a.m., instruments at the University of 

Washington seismology center began 

to show a gradual increase in seismic 

activity. By 1:30 p.m., it was impossible to discriminate individual earthquake traces on the recorder charts 

FIGURE 27.-Photographs taken about 1 

hour after the start of the May 18 eruption from a spot about 31 miles northwest of Mount St. Helens. (Photographs 

by Mrs. Jim Lenz.) A, This photograph, 

taken about 9:20 a.m., shows, beyond 

the distant ridges, the westwardspreading plume of a ground-hugging ash 

cloud (the second that was seen) when it 

had reached a position about 14 miles 

west of the volcano, probably following 

the valley of the North Fork Toutle 

River. Also shown is the "halo" that first 

began to appear around the ash column 

rising from Mount St. Helens (hidden at 

left edge of this view) about half an hour 

after the eruption began. B, This view, 

taken from the same site about 9:30a.m., 

shows the second ground plume near its 

westernmost extent, about 15 miles west 

of the volcano. The umbrellalike higher 

cloud from the vertical eruption column 

first spread outward in all directions but 

later was swept eastward, and the western side of the mountain was left clearly 

visible (see fig. 28). The ground plume 

continued to spread northward, its 

·northwestern edge stopping at about 

10:15 a.m. near where these pictures 

were taken. 
A 

B 
FIGURE 28.-The dense column of ash from the May 18, eruption billowed out of the volcano almost steadily for more than 9 hours after the 

lateral blast had removed the upper northern side of the mountain (hidden in this view from the south-southwest). The ash reached an 

altitude of more than 15 miles, well into the stratosphere, but most of it was carried eastward at lesser altitudes by the prevailing winds 

and often formed distinct horizontal layers in the sky, as seen here. The large white cloud extending above the low layer of ash to the left 

of the eruption column was rising from large steam explosions in hot avalanche deposits near the southwestern end of Spirit Lake (see 

fig. 30). Less violent steam vents (left of mountain) were scattered across avalanche deposits that extended into the upper valley of the 

North Fork Toutle River. This photograph was taken about 11:00 a.m., May 18, 1980, by David Frank (USGS). 

58 The First 100 Days of Mount St. Helens 
because of the large number of seismic 

events and the strong harmonic 

tremor. The seismic activity peaked 

about 3:40p.m., declined, and reached 

"moderate" levels by 5:30 p.m. Harmonic tremor continued at fluctuating 

levels. 

ASH SPREADS 

EASTWARD 

Although vertical plumes of steam 

and ash accompanied the beginning of 

the lateral blast (figs. 21G, H, I), the 

lateral blast was well underway before 

the strong vertical eruption from what 

had been the volcano's summit crater 

began. Ash from the vertical eruption 

column, which within 10 minutes had 

risen to a height of more than 15 miles, 

was rapidly blown to the eastnortheast. The ash cloud produced 

countless lightning flashes that started 

hundreds of fires in trees and forest 

debris near the volcano. 

Dense clouds of ash from the continuing eruption turned daytime to 

darkness as far as 120 miles away, and 

a lighter covering of ash dusted areas 

many hundreds of miles away. Ash fell 

heavily in Montana and visibly as far 

east as the Great Plains of the Central 

United States (fig. 29). 

By 9:30 a.m., Washburn and Linschooten had run from Yakima toward 

the community of Cowiche. As they 

continued running in the warm, clear 

morning, they began to see what they 

thought was a very dense rain cloud 

rising over the foothills of the Cascade 

Range from the west, the normal direction for storms moving into the area. 

FIGURE 29. - Satellite pictures and map show the eastward spread of the ash plume from the 

May 18 eruption, which began at 8:32a.m., Pacific Daylight Time. (Photographs from 

the National Oceanic and Atmospheric Administration.) A, By 8:45 .a.m. (eruption 

plus 13 minutes), the eruption cloud (shown by an arrow) was already large enough to 

be seen clearly in the image from a satellite more than 22,000 miles above the Earth. B, 

By 9:15 a.m. (E plus 43 minutes), the eruption cloud was spreading rapidly, still expanding in all directions from the volcano. C, By 10:15 a.m. (E plus 1 hour, 43 

minutes), the ash had expanded eastward across the Cascade Range into eastern Washington, reaching beyond Yakima (see accompanying map). D, By 12:15 p.m. (E plus 3 

hours, 43 minutes), the ash was falling on Spokane and had extended into Idaho. A 

dense ash cloud from the continuing eruption persisted near the volcano. E, Sketch 

map showing times of arrival of the airborne ash as it spread across the Northwest. The 

time lines represent the margins of the ash plume as seen in satellite images at half-hour 

intervals (from Sarna-Wojcicki and others, 1981). 

122° 120° 118° 116' 114" 112° 110° 

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WASHINGTON ...,- "l --....... ...,..._ 

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, 

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r' ~ >L '::)).. ~ · --- OREGON , IDAHO """ \ 1 \ I ' I _,.,. --:_; 11\ WYO. 

100MilES '! ~'' \ ) t-r-'-r-r'-.--1-...L_....t._-,------.._j o Bo ise ""ti· 

300 KILOMETERS 'fJ.,,, \ E 

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100 

100 200 
The cloud appeared very dark 

blue-the "darkest thunderhead" either 

had ever seen-and had a very abrupt 

edge on its northwestern side. 

Although the cloud looked ominous, 

they still hoped to outrun the "storm." 

When they were about 2 miles east of 

Cowiche (8 miles from home), they 

were suddenly heavily pelted with 

sand-sized particles; they then realized 

that Mount St. Helens had begun a major eruption, and they turned back 

toward Yakima. The sky very quickly 

turned black, and the pelting ash particles were accompanied by "bad 

lightning." They sought shelter under 

the stairs of an old fruit warehouse 

near the road. After about 15 minutes, 

a young man in a flatbed truck came 

by; the runners flagged him down and 

were driven back to their homes. By 

this time (10:30 a.m.), it was black as a 

dark night, and ash continued to fall. 

The ashfall diminished, and the sky 

started to lighten about 3:30p.m., but 

soon the darkness and the ashfall 

resumed. 

Just before the ash arrived at 

Yakima, aircrews of the National 

Guard 116th Armored Cavalry Squadron quickly detached armaments from 

their helicopters and scrambled to get 

the aircraft into the air. Twelve of their 

32 helicopters did not get off the 

ground in time. The other 20 headed 

north where they "could still see light 

in the sky." They flew a long route 

FIGURE 30. - Stearn erupting from still-hot 

parts of the avalanche deposits 18 days 

after the major eruption. Hundreds of 

steam vents and craters formed near the 

site of Spirit Lake and the head . of the 

North Fork Toutle River wherever the 

very hot volcanic deposits were contacted by water, which then turned to 

steam and blew out through the overlying deposits. The view here is toward the 

southeast. The steaming crater in the 

right foreground is about 250 feet across. 

The southwestern end of Spirit Lake, 

largely covered with floating forest 

debris, is in the lower left. (Photograph 

by Philip Carpenter, USGS, June 5, 

1980.) 

60 First 100 Days of Mount St. Helens 

north and then west around the ash 

cloud and were directed to the Kelso 

airport and to the Toutle River valley 

to help with search-and-rescue efforts. 

Ground-based radar observations at 

the National Weather Service's station 

in Auburn, Wash., showed increases in 

vertical ash emission at four distinct 

times-at about 8:40a.m., 10:15 a.m., 

12:45 p.m., and 2:00 to 4:00 p.m. 

Other observers said that the strength 

of the eruption at about 4:30p.m. was 

second only to the 8:40 a.m. pulse. 

The ash column (fig. 28) persisted 

for more than 9 hours, producing 

numerous pyroclastic flows. The early 

ones were mostly ash flows, which 

were produced as the dense part of the 

eruption column fell back onto the 

volcano's flanks and poured downslope at least short distances on all 

sides. Later pyroclastic flows, from 

about noon on, consisted of pumice, 

which was produced by the fountaining of lava froth from the eruptive 

center and poured out through the 

giant breach in the northern side of the 

crater. The pumice and ash flows 

fanned out over the huge mass left by 

the debris avalanche and extended part 

way down the North Fork Toutle River 

valley. Now and then, explosions 

caused by water flashing into steam 

within the hot pyroclastic ·and debrisavalanche deposits along the former 

river course blew material as high as 1 

mile into the air and left craters as 

much as 2,000 feet across (fig. 30). 
MUDFLOWS AND 

FLOODS 

Water from melting snow and ice on 

the slopes of Mount St. Helens and in 

the avalanche debris and from the 

now-buried and disrupted stream 

channels produced dozens of mudflows, large and small (fig. 31). On or 

near the blasted mountain, mudflows 

developed within minutes, some pouring over and eroding deposits of the 

debris avalanche itself. Many mudflows stopped on the lower flanks of 

the volcano, and others were dammed 

temporarily behind debris deposits; 

many, however, coalesced and began 

to move through the major drainageways, generating floods all the way 

down the Toutle River and the Cowlitz 

River below it (fig. 32) and on into the 

Columbia River. The mudflows swept 

FIGURE 31.-Effects of the May 18 mudflows in the vicinity of Mount St. Helens. 

(Photographs by Philip Carpenter, 

USGS, May 20, 1980.) A, The mudflow 

in the South Fork Toutle River reached 

the Camp 12 logging camp (27 miles 

downstream from headwaters on Mount 

St. Helens) about 1 hour and 40 minutes 

after the start of the May 18 eruption and 

left a tangled mass of logs and heavy 

equipment. B, The mudflow in the Muddy River left streambanks strewn with 

logs between ash-coated trees at a reach 

16 miles downstream from headwaters 

on Mount St. Helens. C, Mudflows 

destroyed nearly all the bridges that 

crossed streams draining from the northern, northeastern, and northwestern 

parts of Mount St. Helens. This lack of 

stream crossings greatly hampered 

ground rescue and recovery efforts. The 

steel highway bridge shown in D was 

formerly at this site, on the North Fork 

Toutle River 23 miles downstream from 

headwaters on Mount St. Helens. D, The 

mudflow in the North Fork Toutle River 

was dense enough to support heavy 

machinery and this section of a steel twolane highway bridge as it carried them 

downstream. The mudflows moved some 

of this heavy debris for miles before 

depositing it at places where the mud lost 

velocity. 
62 The First 100 Days of Mount St. Helens 

FIGURE 32.-Effects of floods and mudflows in the Toutle and Cowlitz River 

valleys. 

A , The maximum stage of the 

May 18 mudflows on the Toutle River 

reached the second story of this house, as 

mud coatings on trees and structures 

show. When the high water (mud) receded, sediment deposits completely 

covered this homesite to a level about 3 

feet above the first floor of the large 

house. The structure on the right was a 

large wing of the house that the surging 

mud ripped off and moved to the position shown here. Many lower or less protected homes were completely swept 

away by the mudflows or more severely 

smashed than this house by debris that 

the mud carried. The shallow, debrischoked channel in the background is the 

South Fork Toutle River near its confluence with the North Fork. (Photograph by Dwight R. Crandell, USGS, 

May 24, 1980.) B, Debris-laden floodwater from the Toutle River inundated 

the flood plain of the Cowlitz River, 

shown here, to a width of about 1 mile at 

Castle Rock. The volume of flood deposits left on the flood plain and in the 

channel of the Cowlitz is estimated to be 

as much as 40 million cubic yards, not 

counting a huge, unmeasured amount 

that was carried downstream into the 

Columbia River. (Photograph copyright 

1980 by Bud Kimball, June 20, 1980.) 
up thousands of logs (and heavy logging equipment) from timbering operations, destroyed homes, vehicles, 

roads, and bridges, and inundated 

broad areas of the Cowlitz River flood 

plain. 

One small mudflow developed in the 

valley of South Coldwater Creek (fig. 

7) from the tongue of avalanche debris 

that crossed into that valley over the 

ridge west of Spirit Lake. The mudflow 

probably buried everything that the 

lateral blast had carried into that valley 

from the site of Coldwater II. 

Mudflows also moved rapidly down 

Smith Creek and Muddy River, which 

drain the eastern side of the mountain, 

and Pine Creek on the southeastern 

side. The mudflows, which were laden 

with logs and forest debris, took out a 

bridge near the mouth of Pine Creek as 

well as Eagle Cliff Bridge across the 

head of Swift Reservoir (fig. 22). A 

tree-planting crew that had been working near the upper Swift Reservoir opposite the volcano reported that Eagle 

Cliff Bridge was taken out by a towering flood surge "perhaps 30 feet high" 

that struck without warning about 9:00 

a.m. Observers reported that the flood 

surge entering the upper (eastern) end 

of the reservoir caused an initial 6-foot 

rise in the water level at that end of the 

reservoir in about 15 minutes; the 

USGS reservoir gage at the dam 9 miles 

downstream recorded a rise of 2.6 feet 

by noon. The reservoir, whose level 

had been lowered previously, held the 

added volume and did not overtop the 

dam; thus, the flooding anticipated 

along downstream parts of the Lewis 

River was avoided. The mudflow left 

the eastern end of Swift Reservoir filled 

with mud and forest rubble, its brown 

color contrasting sharply with the clear 

blue of reservoir water farther west 

(fig. 33). 

FIGURE 33.-Timber and mudflow debris, 

carried by flooding tributary streams that 

drain the eastern and southeastern slopes 

of Mount St. Helens, began entering the 

eastern end of Swift Reservoir about half 

an hour after the May 18 eruption began. 

The flood surge reportedly caused an initial rise of about 6 feet at this end of the 

reservoir in 15 minutes, but the level of 

the reservoir had been drawn down 

about 30 feet in anticipation of floods 

from the mountain. The mudflows 

poured about 11,000 acre-feet (about 18 

million cubic yards) of mud and debris 

into Swift Reservoir and caused a waterlevel rise of 2.6 feet throughout the reservoir. (Photograph by Philip Carpenter, 

USGS, May 20, 1980.) 
It took time for the major floods to 

build up in the Toutle River drainage 

system-time that allowed many in 

low-lying areas to escape with what 

they could carry. Within minutes of 

the lateral blast, law-enforcement officers were dispatched to warn people 

about the danger of flash floods and to 

police evacuation routes. Cowlitz and 

Skamania County personnel were 

ordered to prearranged flash-flood 

observation positions along the Lewis, 

Kalama, Toutle, and Cowlitz Rivers. 

People along these streams were 

alerted by radio, telephone calls, 

sirens, and loudspeaker warnings to be 

prepared for hasty evacuation. 

The USGS stream-measuring stations were destroyed or disabled by the 

muddy floods or the bank-to-bank 

flood debris. By midafternoon, however, USGS hydrologists were in the 

area observing the floodflows. Their 

accounts, other eyewitness reports, 

partial records from the gages, and 

communication logs allowed USGS 

hydrologist John Cummans to reconstruct the downstream progress of the 

flood crests (Cummans, 1981). 

The first of the Toutle River floods 

began as a major mudflow traveling 

down the river's South Fork. The mudflow originated in water-saturated 

eruption deposits on the western flank 

of the volcano and began developing 

during early phases of the eruption. By 

about 10:10 a.m., the mudflow was 27 

miles downstream from the volcano at 

Camp 12 logging camp, where it demolished equipment and left a tangled 

mass of logs and debris (fig. 31A). The 

flow was swift, perhaps as fast as 20 

miles an hour, in headwater reaches, 

but its speed decreased as the crest 

swept downstream. As the mudflow 

progressed downvalley, it battered 

down streamside trees and carried them 

along, swept up buildings and automobiles, washed away miles of roads 

along the channel, and destroyed at 

least one bridge. No one is known to 

have drowned in the South Fork flood, 

however, despite a few close calls. 

By 10:14 a.m., the flood crest was 

nearing the confluence of the South 

and North Forks of the Toutle River 

and was described by a deputy sheriff 

as a 12-foot wall of water containing 

logs, debris, and buildings. The mass 

of debris came close to the underside of 

a bridge across State Route 504, about 

half a mile downstream from the confluence of the two forks, but floated 

safely underneath. 

Downstream from the confluence, 

floodwater from the South Fork stayed 

within the channels, and its velocity 

decreased. The water level also 

dropped quickly after the flood crest 

passed. At a USGS stream gage on the 

Toutle River about three-quarters of a 

mile below the confluence of the two 

forks, the peak flow probably was 

reached before 11:00 a.m., but mud 

disabled the recording equipment, and 

so the exact time is not known. Hydrologists did determine, however, 

that the flood crest there was about 21 

feet high, 1 foot higher than the highest 

flood recorded at that site since the 

gaging station was established in 1909. 

The floodwater apparently had 

dropped most of its sediment before it 

reached the Toutle River, where it was 

described as being very muddy water 

rather than the mud of farther upstream. 

After the crest of the South Fork 

flood reached the Cowlitz River, its effects diminished greatly. At a USGS 

gage on the Cowlitz River at Castle 

Rock 2.7 miles downstream from the 

mouth of the Toutle River (fig. 6), the 

flood peak, which occurred there at 

1:30 p.m., caused a water-level rise of 

only 3.2 feet. The arrival of the floodwater at Longview, Wash. (fig. 6),_was 

marked not by a rise of water level but 

by the arrival of "logs, trees, limbs, 

and bark," which continued to float 

down the river past Longview for more 

than 3 hours. 

The South Fork mudflow apparently 

was not greatly heated by the eruption 

deposits from which it originated. A 

survivor described the mud in the up64 The First 100 Days of Mount St. Helens 

per part of the valley of the South Fork 

as being like "warm, fluid brown concrete," but no other comment about 

the warmth of the mudflow was heard. 

A second surge of mudflow was 

observed in the upper valley of the 

South Fork Toutle River about 2:00 

p.m. This mudflow did not reach more 

than a few miles downvalley, however, 

and did no further damage. 

Before the South Fork flood had 

reached Castle Rock, airborne observers had already reported that mudflows were developing in the upper 

valley of the North Fork Toutle River. 

Search-and-rescue flights into the area 

by military helicopters were getting 

underway at the time. No one knew 

how many residents had chosen to remain in the valley of the North Fork in 

spite of evacuation warnings or how 

many survivors of the eruption might 

be trying to make their way out of the 

area by the main highway (State Route 

504) that follows the valley. More large 

mudflows, however, obviously would 

be a major danger. 

The mudflow that came down the 

valley of the North Fork Toutle River 

originated in water-saturated parts of 

the debris-avalanche deposit in the upper valley. It was made up of many 

smaller mudflows and took hours to 

develop because individual small flows 

crossing the hummocky surface of the 

avalanche deposit became ponded in 

closed depressions and could break out 

and merge with adjoining mudflows 

only after filling the depressions. In the 

process, the mud picked up heat from 

the volcanic materials in the avalanche 

· deposit and became steaming hot. The 

crest of the mudflow did not pass the 

downstream end of the avalanche 

deposit until after 1:30 p.m. By that 

time, the crest of the South Fork flood 

had passed Castle Rock, and the mudflows entering Swift Reservoir had subsided greatly. 

The North Fork mudflow moved 

more slowly than the South Fork mudflow but was much larger and more 

destructive. The down valley progress 
of the mudflow was complicated by 

several massive logjams that, when 

they broke loose, caused flood surges 

that were especially destructive and 

that added to the uncertainty of floodresponse efforts. The maximum flow at 

Camp Baker (fig. 22), about 5 miles 

downstream from the end of the 

avalanche deposit, came about 3:00 

p.m. The mud destroyed most of the 

camp and carried away hundreds of 

stored logs as it moved downstream. 

Unlike the South Flow mudflow, 

which became more fluid as it flowed 

downvalley, the North Fork mudflow 

remained thick and dense with sediment and thus was able to carry almost 

anything that it swept up or broke 

loose. A tongue of the mud flowed 

upstream into the Green River (fig. 6) 

and filled the rearing ponds of a fish 

hatchery with debris that included steel 

bridge girders. A few miles farther 

downstream on the North Fork Toutle 

River, observers said that the mud had 

the consistency of fresh mortar and 

that it carried ice chunks, buildings, 

and a variety of equipment, "riding 

high." They reported seeing a fully 

loaded logging truck being carried upright in the mud and submerged only 

to the lowermost tier of logs. Motion 

pictures of this steaming mudflow carrying everything from houses to a steel 

bridge framework, as well as an unimaginable number of trees and logs, 

were shown in color on local television 

stqtions within hours of the eruption. 

These films were the first visual indication for most people in the Pacific 

Northwest that such colossal devastation had begun. 

When the North Fork mudflow 

reached the T ou tie River valley, it was 

so great in height and volume that it 

dwarfed the record flood just established on the South Fork and extended 

flood damage to higher levels and 

broader areas. About 6:00 p.m., the 

mudflow destroyed the bridge at State 

Route 504, half a mile below the confluence of the North and South Forks 

of the Toutle River, just as it had carried away several other bridges upstream. Shortly thereafter, it also destroyed the gaging station a quarter of 

a mile downstream. 

By 8:30 p.m., the mudflow reached 

the mouth of the Toutle River and 

began to raise the level of the Cowlitz 

River as well. At 8:41 p.m., a report 

said that a bridge 6.5 miles upstream 

from the mouth of the Toutle River 

had just been destroyed and that the 

flood level was still rising. This report 

raised serious concerns about a bridge 

on Interstate Highway 5 that crosses 

the Toutle River about a quarter of a 

mile above the river's mouth. Interstate 

5 is the main north-south highway; if 

this bridge were to be destroyed or 

seriously damaged, transportation in 

this region would be severely curtailed. 

Moreover, if the mudflow were to 

wash out this bridge, it probably also 

would destroy a smaller highway 

bridge less than 1 mile upstream and a 

bridge for the main railroad just 

downstream from Interstate 5. 

Washington State Patrol officers 

halted traffic on Interstate 5, as they 

had done for hours during the South 

Fork flood. Officials, local residents, 

and stalled motorists watched in 

anxious fascination as the mud lapped 

higher and higher on the concrete 

bridge abutments. Soon, large pieces of 

floating debris were scraping and banging on the underside of the bridge. The 

largest masses, such as cabins and 

vehicles, began to strike the upstream 

side of the trestle. They would hang 

there briefly and then submerge further 

and roll noisily under the bridge, causing it to shudder ominously. As darkness fell, the flood level was still rising. 

Then flood waves themselves began 

lapping the underside of the trestle. 

Logs could no longer float freely 

underneath; bark and limbs were sliced 

from their topsides as they scraped 

under the bridge. The number of logs 

banging the trestle forcefully before 

being carried underneath by the 

powerful mudflow was increasing. 

No one knows how long the bridge 

and its approaches can withstand this 

battering from the debris and the 

erosive power of the mudflow. There 

are encouraging reports from observers, however, that flood levels 

upstream are receding. 

Meanwhile, the nearby channel of 

the Cowlitz River can no longer carry 

the flow; its banks, too, have been 

overtopped by the muddy floodwater, 

which is spreading outward and inundating homesites and farms on the 

flood plain near Castle Rock. 

CLOSE OF E DAY 

Although the full story of today's 

events will not be known for months to 

come, their significance cannot be 

doubted. Within a few minutes, what 

was once Washington's fifth-highest 

peak lost about 1,300 feet of its height. 

What rer.lains of its top, formerly a 

glistening white cone, has changed to 

ashy gray. The scenic view on the 

northern side has changed to one of 

stark desolation. Vast green forests 

have been transformed into jumbles of 

giant matchsticks. Spirit Lake, once 

clear and blue, is now a steaming expanse of black water and floating shattered trees. Broad ribbons of mud extend up the valleys of former trout 

streams and disappear into clouds of 

ash around the volcano. Gone are most 

of the glaciers that yesterday mantled 

the mountain's northern slope. Gone is 

Goat Rocks, relic of a past eruption 

episode. 

Gone too, are the observation posts 

called Coldwater I and Coldwater II. 

The toll continues to rise as losses 

and damage are reported. Dozens of 

homes and camps along the Toutle 

River and its forks have been destroyed, along with cabins and campsites at lakes north of the mountain. 

Volcanic ash inches thick is being reported from eastern Washington, although conflicting reports suggest that 

some of these thicknesses may be exaggerated. The North Fork Toutle River 

mudflow continues at very high levels, 

but, so far, it has spared the critically 

important highway and railroad 

Chronology of the First 100 Days 65 
bridges that cross the lower Toutle 

River. The Cowlitz River is flooding 

extensive low-lying areas near Castle 

Rock, but it is still staying within its 

banks in downstream areas. 

How many people died or are missing is not known, but some officials 

say that the total may reach into the 

hundreds. By dusk tonight, military 

and other helicopter crews had rescued 

or evacuated more than 130 survivors. 

They had also seen grisly evidence in 

the blast zone that others did not survive. 

No one knows whether the worst is 

over or what the volcano will do next. 

Continuing Threats 

and Mounting Toil 

Monday, May 19 

E Day Plus 1 

The pace of the eruption has slowed. 

The ash column seldom rises more than 

a few hundred to a few thousand feet 

above the volcano; during the night, it 

appeared to consist mostly of steam. 

The volcano seems to be quieting. No 

one knows how long it will remain so. 

Earthquakes, too, have diminished. 

What earthquakes there were today 

came from depths of 10 to 20 miles 

rather than from 3 miles or less, as they 

had before yesterday's eruption. Only 

three were stronger than magnitude 3. 

Daylight revealed that the Interstate 

Highway 5 bridge was still standing, 

although it bore a load of mud and 

debris from last night's battering mudflow. The nearby highway and railroad bridges also survived. The Toutle 

River was still high, but the flood was 

diminishing, and the debris that it carried was no longer striking the undersides of the bridges. Mud lay thick on 

the riverbanks and on the wreckage 

that they held; it also coated the trunks 

of surviving trees up to the maximum 

flood level. Steam from the still-warm 

mudflow created a mist that added an 

eerie aspect to the morning's scene of 

mud and destruction. A bulldozer 

cleared the mud and debris from the Interstate Highway 5 bridge, which was 

reopened to traffic about 8 a.m. 

Search-and-rescue operations were 

resumed at dawn but are hampered by 

ash and unstable deposits. No one 

knows how much time may be left before the mountain lets loose another 

killing blast. 

Rescue efforts and attempts to assess 

damage north of the mountain are being made by aircraft only. Access 

roads in valleys affected by mudflows 

are largely buried or eroded away, and 

blown-down trees (fig. 34) block all 

roads throughout a wide area of the 

uplands. Ground vehicles also are 

hampered in other areas by loose, 

blinding ash, which slickens the roads 

and chokes engines. Many bridges that 

provided access across streams east 

and west of the mountain have been 

washed out by giant mudflows (fig. 

31). 

Even aircraft cannot always get 

close. Visibility is hampered by airborne ash and, in the upper valley of 

the North Fork Toutle River and near 

Spirit Lake, by steam from hundreds of 

new fumaroles rising from the hot 

volcanic debris. More important to 

fliers, however, is the danger to aircraft engines. No one knows for sure 

how much ash an aircraft engine can 

take in before it stalls. Still, the helicopter sweeps, flown mainly by Army 

and Army National Guard, Air Force, 

and Coast Guard aircraft, continue as 

frequently and as far afield as possible 

to locate and assist whatever survivors 

remain. National Guard helicopters 

alone reportedly helped rescue another 

15 people today. (Eight National 

Guardsmen later would be awarded 

medals for heroism during the rescues.) 

Visibility is hampered, too, by for~.st 

and ground fires started yesterday by 

the lateral blast and by lightning bolts 

from the ash clouds. Although the ash 

blanket is acting as a fire retardant, 

hundreds of fires inside the blast area 

are burning in wood debris buried beneath the surface. People in the area 

are too busy rescuing others-or trying 

to survive-to worry about the fires. 

66 The First 100 Days of Mount St. Helens 

The magnitude of the disaster is just 

beginning to be realized. At least 5 people are known dead, and 21 are missing. These figures will no doubt swell 

in coming days as bodies are discovered and as relatives and friends are 

missed. 

Among those known dead are Fred 

and Margery Rollins of Hawthorne, 

Calif., who stopped 15 miles from the 

volcano to watch the eruption. Included among the missing are USGS volcanologist Johnston, who had been at 

Coldwater II observation station; photographer Blackburn, stationed at 

Coldwater I; Mount St. Helens Lodge 

proprietor Truman, who had simply 

refused to leave; and volunteer radio 

operator Martin, whose radioed warning about the eruption provided 

precious lead time for organizing the 

rescue efforts. 

Survivors tell harrowing stories of 

pumice raining on them, of outracing 

ash clouds and floods, of seeing others 

die, and even of seeing crows fall 

lifeless from the sky. Stranded survivors are being sheltered in churches, 

schools, and other public buildings in 

nearby communities. 

In the Cowlitz River valley downstream from the mouth of the Toutle 

River, an area about 1 mile wide near 

Castle Rock lies under mud and water 

(fig. 32B). The flood crest from the 

North Fork Toutle River mudflow 

reached Castle Rock about midnight, 

causing a maximum water-level rise of 

20 feet in the Cowlitz River at that 

point. That crest was more than 6 feet 

above the lowest nearby banks of the 

river. Much of the Cowlitz River flood 

FIGURE 34.- Within a few minutes, hurricane-force winds from the May 18 lateral 

blast transformed vast stands of evergreen forest into drab tangles of giant 

matchsticks. The trees were stripped of 

their branches, toppled, and "combed" 

into patterns. The logging roads shown 

here are about 12 feet across. (Photograph by Austin Post, USGS, June 30, 

1980.) 

plain farther downstream was inundated to at least shallow depths all the 

way to a point about 4 miles upstream 

from Longview at the community of 

Lexington, where several low-lying 

homes were flooded. The cities of 

Kelso and Longview, however, were 

spared. The flood crest reached Longview about 4:00 a.m. today. 

The North Fork mudflow has 

dumped huge volumes of sediment and 

debris into the Cowlitz River, which, 

in turn, is carrying it on to the Columbia River. Tugboat crews worked 

through the night on the Cowlitz River 

to keep floating trees and logs from 

forming logjams that would force 

water levels still higher. The Coast 

Guard reported that the Columbia 

River channel near the mouth of the 

Cowlitz also is littered with floating 

debris; another mass of logs and trees 

about 600 feet wide and extending for 

about 20 miles reportedly is floating 

down the Columbia River toward the 

Pacific Ocean. 

This morning, the ocean-going 

freighter Hoegh Mascot went aground 

4JC' ~ 

(j ~ 

a 

200 

in the Columbia River near Longview, 

the first indication that the navigation 

channel of that river is blocked by 

deposits of mud and debris carried into 

it by the floodwaters from the Cowlitz. 

A Coast Guard spokesman said that 

the channel depth had decreased from 

40 to 15 feet for a distance of 2 miles, 

"which severely limits the ships that 

can come to Portland." The Coast 

Guard closed the CoJumbia River to 

major shipping tonight; the closure 

strands 24 ships at the mouth of the 

Columbia waiting to come upriver and 

another 23 ships in the PortlandVancouver area that cannot move 

downstream over the shallows in the 

navigational channel. The U.S. Army 

Corps of Engineers dredge Biddle is 

slowly pushing its way through the 

floating debris in the Columbia toward 

the shallow area to begin reopening a 

navigation channel for oceangoing 

ships. 

The North Fork mudflow remained 

warm throughout its course to the Columbia River. Its temperature as it 

passed a bridge on the lower Toutle 

WASHINGTON 

' 46° ~ ~- \ 

MOUNT ~T. HELENS 60 X 

0 -- Pasco ' 

~ _,.----------\ (j 

~ l .... -- ~--~ Portland.----.../ '-

River was 91 °F at 9:45a.m. this morning. At Castle Rock, the mixture of 

mudflow and Cowlitz River water 

measured 85°F at 1:15 a.m. and again 

at 6:30 a.m. At Longview, the water 

temperature at 8:00 a.m., about 4 

hours after the flood crest had passed, 

reportedly was 90 °F. Fish could not 

FIGURE 35.-Approximate distribution and 

thickness of measurable ashfall from the 

May 18 eruption of Mount St. Helens. 

Lines represent equal ash thickness, in 

millimeters (1 inch=25.4 mm), and are 

dashed where observations were lacking. 

Circles represent measurement sites; plus 

signs, sites where trace or light dusting 

was observed; crosses, sites where no ash 

was observed. The measurements were 

made over several days by several investigators. At many of the measuring 

sites, enough time had elapsed before the 

measurements were taken for the ash to 

settle and drift; at some sites, rain had 

fallen. Therefore, individual reports of 

ash-thickness measurements, especially 

those made before the ash had been 

disturbed by wind or rain, may be at 

variance with this map. (Map from 

Sarna-Wojcicki and others, 1981.) 

' 

45° 0 100 200 MILES 

0 100 200 

OREGON 

68 The First 100 Days of Mount St. Helens 

' 

300 KILOMETERS (__ 

( 

' ' \r 
FIGURE 36.-Volcanic ash from the May 18 eruption blanketed much of eastern Washington 

and caused great disruption, hardship, and economic loss. A, Street scene in Yakima 

the afternoon of May 18. The dense ashfall made the day "black as the darkest night." 

(Staff photograph from Yakima Herald-Republic .) B, Many motor-vehicle accidents 

(most of them minor) were attributed to the ashfall. Most occurred when drivers, 

blinded by the ash, smashed into stalled vehicles ahead of them or, like the car shown 

in this photograph, lost traction in the ash and slid off the roadway. (Photograph 

courtesy of U.S. Soil Conservation Service.) C, Dozens of emergency vehicles in the 

"ash belt" were disabled, mostly by ash that clogged engine cooling systems or air 

filters. Several ingenious modifications were tried to keep vehicles operating, including 

large diesel truck air cleaners, like the one seen on this Washington State Patrol car. 

Because the fine ash rose in clouds at the slightest disturbance, the dust mask worn here 

by Trooper Leonard Whitney was an essential part of his outdoor uniform. 

(Photograph by Carolyn Whitney, May 19, 1980.) D, By May 19, the farming community of Ritzville was beginning to dig out from an ashfall of more than 3 inches, at 

the same time that it was providing emergency accommodations for more than 2,000 

stranded travelers. The ash "drifted like snow but did not melt." (Photograph by 

Ronald Hartman, U.S. Soil Conservation Service.) 

survive in water this warm, and hundreds were found floating dead on the 

floodwater. 

Meteorologists tracking the eastward-moving airborne ash estimate 

that it will take 3 days to cross the 

country. No one knows how dangerous to health the ash may be, but other 

problems that it is causing are almost 

overwhelming. 

The ash has halted transportation 

almost completely throughout most of 

central, eastern, and southeastern 

Washington, as well as in parts of 

Idaho and western Montana (fig. 35). 

State and local police have banned 

driving on the most dangerous roads 

and highways, and the Federal Aviation Administration yesterday closed 

all airports in affected areas. Westbound trains stopped today as far 

away as Billings, Mont., and Minot, 

N.D., to avoid entering the equipmentdamaging ash. 

In ash-blanketed areas of eastern 

Washington (fig. 36), thousands of 

motorists have been stranded by continuing poor visibility or by disabled 

cars. They spent last night wherever 

they could find shelter from the choking ash. One traveler in eastern Washington describ~d the ashfall as "like being in a desert sandstorm without the 

wind." Minor highway accidents were 

reported in which cars ran off roads 

after losing traction in the ash or 

smashed into stalled vehicles that 

drivers could not see (fig. 36B), but no 

deaths have been reported. 

Chronology of the First 100 Days 69 
Law-enforcement and other 

emergency-services crews struggled to 

keep patrol and service vehicles running, but about 200 patrol cars were 

disabled by ash yesterday and today. 

The damage to vehicles included seized 

engines that overheated after their 

cooling systems were clogged with ash, 

ruined vital parts that were just "worn 

out" by the abrasive ash, and clogged 

carburetors and air filters (fig. 36C). 

The fine ash, blown into clouds by 

each passing vehicle or gust of wind, 

enters every crack and crevice of a 

vehicle and seems impossible to control. Where the ash is deep, highway 

snowplows are at work in sometimes 

futile attempts to clear the ash off the 

roadways. Washington Department of 

Transportation officials said that highway-clearing work is being slowed up 

because the plows have to stop every 

100 miles or so to have the ash blown 

from engine air filters. The ash drifts 

like snow but does not melt. It often 

blows back into cleared areas as fast as 

the crews can scoop it off. 

The heavy ash, frequently described 

as being like Portland cement, has flattened many field and row crops in cenFIGURE 37.-The avalanche deposit, largely 

the remains of the bulge mass from 

Mount St. Helens, included hot parts of 

the volcano as well as blocks of ice from 

destroyed glaciers. A, USGS hydrologist 

J. R. Williams examines a fumarole area 

within the cooler avalanche deposit at the 

northern base of Mount St. Helens. The 

heat was derived from hot rock material 

buried within the deposit. (Photograph 

by Philip Carpenter, USGS, June 5, 

1980.) B, The huge debris avalanche that 

"uncorked" the lateral blast included ice 

from five glaciers on Mount St. Helens. 

Barry Voight of Pennsylvania State 

University examines this ice block, which 

was rafted along on the avalanche debris 

in the North Fork Toutle River valley . A 

small pond of water was forming as the 

ice melted in the warm springtime. 

Another ice block, found closer to the 

mountain and not shown here, had a 

diameter of about 300 feet, the length of a 

football field. (Photograph by Robert L. 

Smith, USGS, June 2, 1980.) 

70 First 100 Days of Mount St. Helens 

tral and eastern Washington. State officials and various agricultural experts 

expressed deep concern today that 

agricultural production, one of the 

mainstays of Washington's economy, 

could be greatly curtailed by the volcanic ash. They are concerned that a 

dense covering of volcanic ash could 

damage orchards, hayfields, grazing 

lands, and extensive grain acreages. It 

all depends, said one, on the buildup of 

ash and on the amount of water (rain 

and artificial sprinkling) available to 

wash the plants. 

The results of both the May 16 and 

the May 18 thermal surveys of the 

mountain are now available. They 

show that, in addition to the warm 

areas found during the May 2 survey, a 

new hot spot had appeared at the top 

of Shoestring Glacier and that the upper area of the bulge had been "perforated" with new warm areas. Thermal features detected in both the 

surveys were very similar. Geothermal 

specialists interpret the images as proof 

that the magma had moved up to a 

very shallow position-perhaps within 

a few hundred yards of the surfacebefore yesterday's eruption. 

At 5:09p.m. this evening, an eruption produced what appeared to be a 
small pyroclastic flow, which prompted officials to call back rescue units 

from the Toutle River valley. However, the volcano soon returned to a 

quiet state, and no evidence of the 

pyroclastic flow was found. 

At dusk, the level of the Cowlitz 

River at Castle Rock was still about 10 

feet higher than it had been before the 

eruption, and the channel downstream 

from the mouth of the Toutle River remained choked with mud, logs, and 

wreckage, most of it from the valleys 

of the Toutle River and its two forks. 

Much of the lower Cowlitz River flood 

plain remains inundated. USGS hydrologists warn of even more serious 

flooding if water trapped in the debrisdammed Toutle River system, including the area of Spirit Lake, were to 

be suddenly released. 

Tuesday, May 20 

E Day Plus 2 

Sporadic eruptive activity is producing mostly steam. Seismicity, too, has 

declined to a level lower than any since 

March 22; no earthquakes registered 

more than magnitude 3 today. 

Scientists in the field are finding that 

the debris flow that rushed down the 

upper valley of the North Fork Toutle 

River immediately after the initial Sunday morning blast includes hot areas as 

well as cold ones. Scattered warm 

masses in the avalanche debris, which 

is largely the remains of the "bulge" 

mass from the mountain, probably 

came from hot parts of the volcano, 

and colder parts are blocks of ice from 

the destroyed glaciers that were caught 

in the flow (fig. 37). The debrisavalanche deposit is riddled with 

fumaroles, and, now and then, scientists hear explosions, which, no doubt, 

occur when the buried heat in the 

deposit causes subsurface water to 

flash into steam. 

Field crews also have measured the 

temperature of some of the pyroclastic 

flows that followed the initial blast 

(fig. 38). At a depth of about 2 feet, 

they obtained readings of nearly 150 oc 

(300 °F). 

FIGURE 38.-Mount St. Helens pyroclastic deposits. A, Geologists R. P. Hoblitt of the USGS 

(left) and Edward Graeber, Jr., of Sandia Laboratories (right) use a thermocouple probe 

to measure the temperature in a pumice slope north of Mount St. Helens. Although the 

pumice at the surface was cool enough to walk on, at a depth of a few inches it was hot 

enough to boil water. (Photograph by Terry Leighley, Sandia Laboratories, May 30, 

1980.) B, Hobblitt digs into a deposit of pyroclastic material near the head of Smith 

Creek, about 2 miles east of Spirit Lake, for samples of charred wood (see piece below 

his foot in left foreground). The dark-gray deposit is overlain by several inches of lightcolored airfall pumice, which, in turn, is overlain by a thin layer of gray ash that 

developed mud cracks when it dried. (Photograph by Robert L. Smith, USGS, June 6, 

1980.) 

Chronology of the First 100 Days 71 
No one yet knows how much of a 

flood threat the "new," higher Spirit 

Lake may be. One crucial unknown 

factor is the stability of the debrisavalanche deposit that buried the lake's 

former outlet (to North Fork Toutle 

River) ·and impounded the lake at its 

new, higher level. Another uncertainty 

is whether the lake, now that its former 

outlet is blocked, will rise until it overtops the debris dam. Although most of 

the water displaced from the lake by 

last Sunday's giant avalanche already 

has drained back, the lake continues to 

receive inflow from its various tributary streams. If the dam is overtopped, 

Crandell said, "It will be like water going over a spillway; but, in this case, 

the spillway is not made of concrete, 

but of very unstable material." The 

spilling water could quickly erode a 

channel through the debris dam that 

would release more floodwaters, perhaps at catastrophic rates, to downstream areas. 

Scientists who are watching the lake 

(as best they can) report that the water 

level thusfar has remained below the 

top of the debris dam, and no flooding 

from this source is imminent. They 

cannot measure the lake's level directly, and aerial observation of the 

deposits southwest of the lake, in the 

area that might be overtopped, is 

greatly hampered by steam pouring 

from dozens of fumaroles. However, 

aerial radar imagery has shown no 

signs that the area of the lake is enlarging, and some observers have seen 

water seeping through (or beneath) the 

debris dam and flowing westward. If 

this seepage keeps pace with inflow to 

the lake, the chances that the lake level 

will stabilize below the dam crest and 

that the dam itself will hold are greatly 

increased. 

If the dam does fail, it might go 

quickly and (if visibility were poor 

when it failed) with little warning. A 

flash-flood watch remains in effect 

along the Toutle River, and Washington State Patrol officers are stationed 

at the Interstate Highway 5 bridge 

across the Toutle River to close the 

highway again, if it becomes necessary. Hydrologists working with 

limited data are trying to estimate the 

likely height and speed of the flood 

crest that would occur if the dam is 

breached. On the basis of the available 

information, they cannot guarantee 

even a 1-hour warning for downstream 

areas. 

Mapping specialists from the Forest 

Service, USGS, and the Washington 

Department of Natural Resources met 

today to coordinate production of 

aerial photographs and maps of areas 

affected by the eruptions and flooding. 

New aerial photographs of the modified areas will be obtained as soon as 

weather permits. In the meantime, a 

new color topographic map of Mount 

St. Helens and vicinity, showing 

features as they were just before the 

March 27 eruption, will be prepared 

from existing data as soon as possible. 

These maps are urgently needed for 

evaluating changes in landscape, lakes, 

and streams and for guiding rehabilitation efforts and further scientific 

studies. 

Existing maps of the Cowlitz River 

channel and flood plains are as obsolete as preeruption maps of the Spirit 

Lake area. Today, hydrologists began 

remapping the debris-choked channel 

in order to evaluate the continuing 

flood hazard. They are finding that the 

river bottom is as much as 15 feet 

shallower than it was before the mudflows and that the water-carrying 

capacity of the channel is greatly 

reduced. 

Since the May 18 eruption, nearly 

continuous bad weather has prevented 

flying over the mountain to obtain accurate data on changes in heat emission. An aerial infrared survey flown 

by a U.S. Navy airplane at midday, 

however, and a daytime helicopter 

survey over the accessible western and 

southern flanks of Mount St. Helens 

revealed no new sources of volcanic 

heat emission outside the crater. 

The City of Yakima has declared 

itself a disaster area, and Washington 

72 The First 100 Days of Mount St. Helens 

Governor Ray telegraphed President 

Carter to ask that the entire State be 

declared so. Many schools and roads 

are still closed, and the Columbia River 

remains closed to most shipping, but 

people are digging out of the ash. 

Residents of Ritzville, which received more than 3 inches of ash, have 

an especially difficult cleanup problem. 

After spending most of Sunday and 

Monday helping each other (and about 

2,000 stranded travelers) survive, they 

are now seeking places to dump the ash 

where it will not just blow back into 

town. 

Although people in areas where volcanic ash is present are still being cautioned to avoid breathing it, agronomists are now predicting less long-term 

harm to animals and crops than they 

had expected. Some say that the effects 

in most of the "ash belt" will not be 

much worse, if any, than those of a 

bad dust storm. Much of the first hay 

crop, however, apparently has been 

lost. 

The airborne ash cloud from last 

Sunday's eruption is still moving eastward and has now reached beyond the 

Mississippi Valley. USGS Chief Hydrologist Philip Cohen assigned the 

task of mapping the areas of noticeable 

ashfall beyond the Pacific Northwest 

to USGS hydrologists in the other 

States along the path of the ash cloud 

(fig. 39). Some meteorologists had expected the ash to fall in trace amounts, 

at least, on every State east of the 

Rocky Mountains except Texas, 

Louisiana, and Florida. 

Ben Bena, Cowlitz County Deputy 

Sheriff, has compiled a "scorecard" of 

the number of people rescued from lifethreatening situations by aircraft 

crews: Air Force, 61; Washington Army National Guard, 28; Coast Guard, 

6; Army, 4; and Civil Air Patrol, 1. 

These same crews have plucked dozens 

of other people from less desperate 

situations. Several rescues also have 

been made by scientists and news reporters in other helicopters. Ninetyeight people are now on the official 

"missing" list. 
Wednesday, May 21 

E Day Plus 3 

Eruptive and seismic activity continues at a low level. The mountain 

vented only plumes of steam today, 

and only two earthquakes greater than 

magnitude 3 were recorded. 

Scientists flew to Spirit Lake and 

found the level to be about 150 feet 

below the top of the debris flow; 

although the danger of an outburst 

flood is thus lessened somewhat, they 

nevertheless placed markers along the 

lake to help maintain a watch on its 

level. 

The Federal Aviation Administration today warned flyers that volcanic 

ash can pock aircraft windshields and 

clog engines. The ash cloud in the 

stratosphere reached the Atlantic 

coast. 

Reporters in Yakima, after establishing a grid within the city and sampling 

and weighing ash from grid locations, 

FIGURE 39.-Approximate distribution in the United States of noticeable ashfall from the 

May 18 eruption of Mount St. Helens, as of May 23, 1980. Most of these ashfall areas, 

which were identified during a rapid reconnaissance by USGS hydrologists and others, 

received only trace amounts. Other areas to the east probably received minute amounts 

of ashfall. Minor concentrations of ash from the same eruption were suspended in the 

stratosphere (above 36,000 feet) and carried slowly in convoluted paths around the 

world. 

determined that about 600,000 tons of 

ash from Sunday's eruption have fallen 

on the 12. 9-square-mile city. 

Spokane and several smaller communities have been forced to ration 

city water because residents' attempts 

to wash ash from cars, streets, and 

buildings have depleted reservoirs. The 

City of Longview has instituted emergency water-use measures for another 

reason. Intake pipes from the Cowlitz 

River, which normally supply the city's 

reservoirs, have been clogged by mud 

and debris from the flooding that 

began on May 18. The mass of muddy 

debris so far has resisted all efforts to 

remove it from the intakes. 

Electrical utility crews in the "ash 

belt" are busy removing accumulations 

of ash from high-voltage powerline insulators by using high-pressure air and 

water jets. Although the ash is an insulator when it is dry, it conducts electricity when it is wet and causes highvoltage arcing and power surges that 

damage electrical equipment. Electrical 

service has been interrupted because 

power must be switched off during the 

cleaning operations. 

Airports and roads in eastern Washington have begun to reopen. Washington Department of Transportation 

officials report that about half of the 

1,100 miles of State roads that were 

Chronology of the First 100 Days 73 
closed because of ash have been reopened. 

President Carter today declared 

Washington State a disaster area, and 

major Federal aid to victims of the volcano's devastation can begin. 

The Coast Guard reported that 31 

oceanbound ships now are tied up at 

Portland and Vancouver awaiting the 

reopening of the Columbia River shipping channel. Another 10 ships are 

waiting at Astoria, Oreg., to come to 

those upriver ports. Several incoming 

ships originally scheduled to call at 

Columbia River ports now have been 

diverted elsewhere. 

Thirty military helicopters scheduled 

to search today for survivors and victims of the catastrophe were grounded 

because of cloudy weather. The official 

count is now 14 dead and 90 missing. 

The body of photographer Blackburn 

was recovered today from Coldwater I 

observation station. He had l;>een 

seated in his car, which was mired in 

ash to the windows (fig. 40A). 

Thursday, May 22 

E Day Plus 4 

Eruptive activity has slowed to a 

steady pattern. Eruptions of steam are 

frequent or nearly continuous, and the 

plumes sometimes rise 18,000 feet 

above sea level when the wind is light. 

Little or no ash darkens the plumes, 

although the familiar "rotten egg" 

smell attests to the presence of hydrogen sulfide. 

Earthquake activity has diminished. 

Small quakes recorded today were 

from deeper sources; some originated 

northeast of the volcano. 

Crandell reports that the water level 

in Spirit Lake behind the debris dam is 

declining; the water seems to be flowing out through the debris-avalanche 

deposit and gravel in the old channel 

that was buried by the avalanche 

deposit. Geologists have determined 

that the avalanche deposit is hundreds 

of feet thick near the southwestern end 

of Spirit Lake. Scientists now think 

that the avalanche deposit can retain 

FIGURE 40.-Desolate vehicles in the blast zone created by the May 18 eruption. A , The body 

of photographer Reid Blackburn was recovered from this car on May 21, 1980, at Coldwater I observation station. None of the photographic film in the car produced a discernible image. The small red flags indicated to other searchers that the vehicle had been 

checked. (Photograph by Terry Leighley, Sandia Laboratories, May 28, 1980.) B, An 

ash-covered truck and horse trailer near Ryan Lake, more than 12 miles northeast of 

Mount St. Helens. The vehicles were parked at the edge of the area in which trees were 

blown down by the lateral blast. Two men, one the owner of these vehicles, were 

camped at the lake nearby and were asphyxiated by the hot volcanic ash, which 

covered this spot to an average depth of about 6 inches. The blast temperatures were 

hot enough to melt the plastic of the truck grill, trailer window, signal indicators, and a 

lunch box. The tires and glass truck windows, however, were intact. (Photograph by 

Daniel Dzurisin, USGS, May 27, 1980.) 

74 The First 100 Days of Mount St. Helens 
the lake indefinitely unless its water 

level rises greatly. 

USGS geologist David Dethier was 

among the first to get a broad view of 

the huge new crater. He was riding in a 

Forest Service airplane that was flying 

an observation and radio-relay mission 

at an altitude of 18,100 feet above the 

general cloud cover that has persisted 

since the night of May 18 and 19. (Although helicopters have been able to 

edge up to the crater, clouds and steam 

have obscured the interior.) About 

6:00 p.m., the clouds began to open, 

and the pilot spiraled down steeply to a 

lower altitude over the devastated area 

north of the volcano, from where the 

observers got the first spectacular view 

of the mountain's interior and from 

where Dethier took the photograph in 

figure 41. They saw a greatly shortened 

peak, now crested by a jagged rim enclosing a huge, steaming-crater shaped 

like a giant amphitheater open to the 

north. 

James Moore and Peter Lipman, also 

of the USGS, were the first scientists to 

get a close look at features inside the 

volcano's crater today. Lipman said 

that there is now a second crater inside 

the larger one. A ridge rising above the 

middle of the large crater's floor forms 

the rim of the smaller crater, which lies 

in the southern half of the large amphitheater. Small pools of muddy water 

are collecting in depressions in the amphitheater floor, which is about a third 

of a mile wide. Much of the steam 

creating the plume above the volcano 

is jetting upward from several large 

vents within the central crater, which 

form a ring around the deepest part of 

the crater and probably mark the volcano's central "throat." 

Short-term plans for scientific 

studies give first priority to mapping 

the devastated areas and evaluating the 

flood hazard that may still remain. 

Lost or damaged scientific instruments 

will be reinstalled as soon as conditions 

are considered safe. 

Spokane International Airport reopened today "under limited conditions" after an all-night cleanup effort, 

A 

B 

FIGURE 41.-The "new," shorter Mount St. Helens. A, The first opportunity for a broad 

view of Mount St. Helens after the May 18 eruption came on May 22, when clouds 

that had obscured the area since the eruption parted to reveal the stubbed-off, 

hollowed-out volcano, newly coated with 4 to 6 inches of snow. This photograph looking into the open mouth of the amphitheaterlike crater was taken from an airplane 

about 3 miles north-northwest of the crater's center at an altitude of 6,000 to 7,000 feet. 

The new 8,364-foot "summit" of the mountain (the highest part of the crater rim on the 

southwestern side) was obscured by vapor clouds. (Photograph by David P. Dethier, 

USGS.) B, The cratered stump of Mount St. Helens as viewed from the northeast. The 

dashed lines show the height lost (about 1,300 feet) in the May 18 eruption. This painting by Dee Molenaar (USGS) also shows remnants of Shoestring Glacier, descending 

from the notch in the left side of the crater rim, and of Forsyth Glacier (right center). 

Chronology of the First 100 Days 75 
but most airports in the "ash belt" remain closed. Trains in the region are 

running on near-normal schedules, and 

interstate bus service is resuming. 

Idaho police lifted a travel ban on their 

State's ash-covered highways, but they 

cautioned motorists to drive with care. 

State of Washington health officials 

said that crystalline silica, which can 

cause chronic lung disease, has been 

found in the ash. Available information, however, is not adequate for 

judging the actual risk to the general 

population. Also, postal officials 

warned the public not to mail "souvenir" as}) in paper envelopes that can 

leak and damage postal machinery. 

President Carter toured the stricken 

area today in company with Governors Ray of Washington and John 

Evans of Idaho. The eruption was, 

President Carter said, "a natural disaster of unprecedented proportions. " 

The Corps of Engineers began dredging mud and debris from the Columbia 

River shipping channel near the mouth 

of the Cowlitz River. Thirty-one 

vessels remain stranded above the 

shoal waiting to move downriver and 

out to the Pacific Ocean. 

The Forest Service began ground 

searches today for more victims of the 

eruptions. 

Friday, May 23 

E Day Plus 5 

Although the weather was very 

cloudy until late afternoon, the clouds 

finally broke up, and today was one of 

the best days for viewing the mountain 

since May 18. Today's eruption pattern 

in the crater was similar to yesterday's; 

plumes of steam and other volcanic 

gases were rising above the crater rim. 

Observers saw one small ash cloud but 

concluded that the ash had avalanched 

down from the walls of the crater and 

was not new material. 

There is a lull in seismic activity; no 

earthquakes registered above magnitude 3 today. Although there were 

several smaller quakes, they were 

spread over a larger area than the 

quakes before May 18 had been. At a 

seismic station at Elk Rock about 10 

miles northwest of the crater, one of 

several instrument stations that had 

been destroyed by the lateral blast, instruments were reinstalled today to 

help supply data for continuing studies 

of earthquake activity. 

A large area north of Mount St. 

Helens is dotted by steam vents and 

craters from steam explosions. The 

steam is from underground water that 

is heated by hot avalanche and blast 

deposits. One vent near the southwestern end of Spirit Lake (fig. 30) erupted 

steam 5,000 to 6,000 feet into the air 

early this evening, startling the pilot 

and passengers of a Forest Service 

airplane that happened to be flying 

over the area. 

A chemical analysis shows that the 

glassy ash blown out of the volcano on 

May 18 and since has the composition 

of dacite; this rock is formed from a 

type of magma that has a moderately 

high silica content and is generally 

quite viscous. 

The first Disaster Assistance Center, 

mandated by President Carter and 

Governor Ray, opened today in Kelso, 

Wash. The center is operated by the 

Federal Coordinating Office of the 

Federal Emergency Management Agency in cooperation with the Washington 

Department of Emergency Services. In 

addition to the Kelso center and the 

temporary Federal Emergency Management Agency headquarters in Vancouver, other centers will be opened as 

needed in eastern Washington and in 

Idaho communities. 

Governor Ray called out the National Guard to help clean up volcanic 

ash in eastern Washington this 

weekend. A major manufacturer of 

dust masks donated 21,000 of them for 

use in ash-covered areas. Hay is being 

sought for animal herds in areas of 

thick ashfall in eastern Washington 

and for surviving animals near Mount 

St. Helens. 

By the end of the day, USGS 

hydrologists had installed new streamflow-measuring stations equipped for 

76 The First 100 Days of Mount St. Helens 

radio telemetry on the Cowlitz River at 

Castle Rock, on the Toutle River about 

6 miles upstream from its mouth, and 

on the North Fork Toutle River farther 

upstream. 

State of Washington officials this 

evening released an estimate of more 

than $1 billion for most of the losses 

suffered in the State as a result of the 

May 18 eruption. 

Today is the beginning of the 

Memorial Day weekend, a time when 

eastern Washington normally would 

receive hordes of vacationers from 

western parts of the State and from the 

Portland area. The Washington 

Department of Transportation, however, warned of windblown ash, continuing restrictions on road use, and 

limited public transportation in ashfall 

areas. These warnings, as well as the 

continuing closure of traditional 

recreation areas around Mount St. 

Helens, are expected to cause unusually heavy use of recreation areas in 

western Washington, especially the 

Pacific Ocean beaches. 

The number of bodies recovered 

from the Mount St. Helens area rose to 

17, but 71 people are still missing. The 

body of one man was found on the seat 

of his car; his camera was still held 

toward the volcano. 

Saturday, May 24 

E Day Plus 6 

The volcano ejected plumes of ash 

and steam about 15,000 feet above the 

crater twice today, at about 2:30 p.m. 

and 11:05 p.m. Ash sprinkled towns as 

far south as Salem, Oreg. Harmonic 

tremor, which has continued at varying weak levels throughout the past 

week, was somewhat stronger most of 

today. 

USGS scientists installed new targets 

on the mountain for laser distancemeasuring instruments today. They 

also measured temperatures of about 

540°F (280°C) in pyroclastic flow 

deposits on the volcano's northern 

flank. Geologists mapping in the 

devastated area found that the lateral 
blast had carried stones as large as 

grapefruit that undoubtedly caused 

much of the stripping and battering 

done to the exposed surfaces of trees 

(fig. 42). 

About 45 National Guardsmen arrived today in Ritzville, which has 

received the heaviest ashfall of any 

community away from the volcano. 

They began shoveling ash from some 

of the town's flat roofs to reduce the 

danger of collapse. 

Scientific instruments and related 

equipment lost as a result of the May 

18 eruption include: 

• One electronic laser distancemeasuring instrument, 1 theodolite, 

and 18 surveying reflector targets-destroyed. Three other reflectors-damaged. 

• Three telemetered seismic stations 

and two 5-day recorders-destroyed. 

• Two automatic platform tiltmeters-destroyed. 

• Two recording magnetometersburied (one may be shallow enough 

to recover). 

• Three time-lapse cameras, two video 

cameras, and several hand-held cameras-destroyed. 

• Several communication radios and 

two satellite-relay data transmitters-destroyed. 

• One portable spectrometer-destroyed. 

• One stream-gaging station and its instruments and two water-quality 

monitoring stations and their instruments-destroyed by mudflows. 

Another Explosive 

Eruption and Its 

Aftermath 

Sunday, May 25 

E Day Plus 7 

Shortly after 2:30a.m., the volcano 

began ejecting a huge vertical column 

of ash, the most vigorous eruption 

since last Sunday. Airborne observers 

could see that the column reached a 

height of 24,000 feet in about 7 minutes 

and began to mushroom at the top. 

The National Weather Service radar 

operator in Portland watched it reach 

an altitude of 45,000 feet by 2:45 a.m. 

Because winds were moving in different directions at different altitudes 

today, the ash was scattered over wide 

areas of western Washington and 

Oregon. 

The eruption was heralded at 2:32 

a.m. by an increase in the amplitude of 

harmonic tremor, which had been 

present at a very low level since about 

midnight. A swarm of small earthquakes began at 2:40 a.m. and continued at a rate of one or two an hour, 

all originating about 5 miles beneath 

the mountain. By 8:00a.m., the intensity of tremor had diminished, and the 

earthquake swarm began to subside, 

although the volcano continued to 

erupt. 

Aerial surveillance was continued 

from a Forest Service airplane through 

the early morning, but only once could 

observers see the volcano itself. That 

brief glimpse revealed that the ash was 

rising from two vents-one in the 

northeastern part of the crater and 

another in the southwestern part. A 

new, small mudflow had descended 

south of Shoestring Glacier on the 

southeastern side of the mountain but 

did not extend beyond the base of the 

cone. Even aerial observation, 

however, was halted when Portland 

International Airport closed because of 

the ash, which had begun to fall heavily in Portland and Vancouver as early 

as 6:00a.m. 

Most people still living near the 

volcano on the southern side-about 

200 in all-were evacuated this morning. Flood warnings were issued for 

FIGURE 42.-This shattered tree stump on an exposed ridge about 5 miles north of the crater 

is striking evidence of the tremendous force of the May 18 lateral blast. The handle of 

the folding shovel is 1.7 feet long. (Photograph by David Frank, USGS, August 19, 

1980.) 

Chronology of the First 100 Days 77 
most rivers draining from Mount St. 

Helens, in case renewed eruptions 

should trigger new mudflows or floods 

that might spill out of river channels 

still choked with debris from the May 

18 eruption. 

The top of the ash column remained 

between 13,000 and 20,000 feet above 

sea level most of the day. By early 

evening, the erupted column, as seen 

on the weather radar, was only a few 

thousand feet above the crater rim; as 

of midnight tonight, activity had 

returned to its former subdued level. 

Measurements of the sulfur dioxide 

(S02) content of an ash-laden eruption 

plume this afternoon showed the 

highest concentrations found to date 

According to Richard Stoiber, a Dartmouth College air-quality specialist, 

the amounts measured were equivalent 

to an emission rate of 2,400 metric tons 

of S02 a day. 

The ash content appeared to lessen 

as soon as the column began to 

mushroom, and the height of the column decreased within the first hour; 

still, the quantity of ash was so great 

that it hampered visibility throughout 

the day at places in nearly every direction from the volcano except northeast. Most airports in southwestern 

Washington and northwestern Oregon 

were closed at various times during the 

day because of poor visibility and the 

fear that the ash would harm vital aircraft parts. Airports in the Seattle area 

also were closed briefly. 

The latest ashfall at it heaviest is 

much less than the thickest deposits 

laid down last week in eastern 

Washington; it has been troublesome 

nonetheless and has affected several urban areas that had received only light 

dustings before. Traces of today's ash 

reached as far north as Seattle in 

western Washington and south of 

Portland in western Oregon. The bulk 

of the ash, however, blew to the northwest (fig. 43). Chehalis, SO miles northwest of the volcano, received about 

half an inch of ash. Light ashfall 

reached the ocean beaches of southwestern Washington and northeastern 

+ 

+ 

+ + 

+ -±p Port 

Angeles 

0 Seattle 

X 

+ 

X 

1, Shelton0 

0 Tacoma 

0 

(") 

rn 

)> 

'2 

OREGON 

0 10 20 30 40 MILES 

I I 'I I I 11 I 11 I I 

0 10 20 30 40 50 60 KILOMETERS 

o Oiympia 

WASHINGTON 

0Vancouver 

Portland 0 

FIGURE 43. -Generalized distribution of ash from the May 25 eruption of Mount St. Helens, 

as compiled by Sarna-Wojcicki and others (1981). Lines represent equal ash thickness, 

in millimeters (1 inch=25.4 mm), and are dashed where observations were lacking. 

Circles represent measurement sites; plus signs, sites where trace or light dusting was 

observed; crosses, sites at which no ash was observed. Other observers reported that 

ashfall in the areas of Olympia, the Washington coast, and the Portland-Vancouver 

metropolitan area was greater than the map indicates. 

Oregon. In areas of densest ashfall, the 

sky stayed dark until midmorning. 

While the ash was still falling in 

many areas, the rain started. As one 

observer said, "It was raining mud." 

Many traffic accidents were attributed 

to a combination of roads made slick 

by wet ash and visibility obstructed by 

the muddy rain. Drivers reported that 

they could drive only so long as their 

windshield washers operatedand then only if they could keep their 

vehicles on the slippery roads. These 

conditions resulted in a IS-vehicle 

pileup, with injuries, on Interstate 

HighwayS near Chehalis. For much of 

its route between Olympia and Vancouver, Interstate Highway S was in 

the path of the densest ashfall. Officers 

of the Washington State Patrol and 

78 The First 100 Days of Mount St. Helens 
sheriffs' departments closed that 

highway and others while driving conditions were most dangerous. Portland 

Mayor Connie McCready limited traffic in that city to 15 miles an hour to 

help avoid stirring up the fallen ash. 

The ashfall disrupted business as 

well as travel. In Kelso, even the 

Disaster Assistance Center was closed. 

Road and airport closures temporarily 

stranded thousands of travelers this 

Memorial Day holiday weekend. 

Ironically, many travelers were in 

ashfall areas because they had been 

warned away from traditional recreation areas in eastern Washington. 

Major traffic jams were caused when 

motorists returning early from the 

coastal areas· converged on population 

centers in the Puget Sound and 

Portland-Vancouver areas. 

Travel in eastern Washington was 

restricted, too. Interstate Highway 90 

was closed through most of the eastern 

part of the State as winds stirred up 

blinding clouds of the fine ash that fell 

last Sunday. Busloads of National 

Guard troops from Seattle, on their 

way to help clean up at Moses Lake, 

were stranded overnight at Ellensburg, 

Wash. (about 30 miles north of 

Yakima). Nine pieces of cleanup equipment already had been trucked to 

Moses Lake, but no one arrived to 

operate them. 

Emergency crews in areas blanketed 

by wet ash worked rapidly to clean 

transformers and insulators, so that 

electrical systems shorted out by the 

sticky ash could be restored. 

Participants in the Mount St. Helens 

Technical Information Network, a 

group newly organized by USGS scientist Robert L. Wesson under a directive 

issued by President Carter and Governor Ray, met in Spokane today. Their 

purpose is to find answers to health, 

agricultural, and transportation problems caused by volcanic ash. Because 

solutions to many of these problems do 

not now exist, the group, which consists of specialists in various fields, will 

summarize what is known about 

volcanic ash hazards and focus 

research on what is not. 

The Corps of Engineers reported that 

the removal of approximately 300,000 

cubic yards of material from the Columbia River channel has deepened it 

to a minimum water depth of 20 feetabout half the 40-foot depth of the normal shipping channel. The dredged 

material is being dumped on islands in 

the Columbia River and along parts of 

the riverbank. The Cowlitz River, 

engineers estimated, also will have to 

be dredged upstream at least to Lexington (9 river miles upstream from the 

Columbia) and probably beyond Castle Rock (to river mile 21) for flood 

control. 

The levee along the Cowlitz River 

near Castle Rock is being built up 5 feet 

along a front 2,000 feet long. At Lexington, 300 feet of the levee was raised 

3 feet, and, at Kelso, the levee was 

raised 2 feet. Cowlitz County has been 

given 40,000 sandbags to help in flood 

control. 

USGS geologist Crandell today 

presented a new map showing the 

volcanic hazards of the Mount St. 

Helens area to Governor Ray. He 

pointed out that the main dangers from 

the volcano still consist of ash, 

mudflows and floods, pyroclastic 

flows, and lateral blasts. The history of 

this volcano, however, and that of 

others like it suggest that lava flows are 

an unlikely event. 

Governor Ray, by executive order, 

extended the Red Zone around Mount 

St. Helens out to 20 miles in all directions from the volcano (fig. 13). Only 

people on official business (including 

approved scientific work) or holding 

special permits are to be allowed in the 

zone. The penalty for unauthorized 

presence in the Red Zone was set at a 

fine of $1,000 or a year in jail or both. 

Monday, May 26 

E Day Plus 8 

Although both the volcanic eruptions and their seismic accompaniment 

have settled down, ash continues to fall 

during the day and to be picked up 

again by the wind. Observers in the 

round-the-clock surveillance plane can 

see the volcano now and then; when it 

is visible, it seems to be emitting steam 

almost entirely, although occasional 

traces of gray ash are sighted. No 

earthquakes above magnitude 3 were 

recorded. 

By 10:00 a.m., only four State 

highways in Washington were still 

closed, three of them being in the 

southwestern part of the State near 

Mount St. Helens. Interstate Highway 

5, which received a troublesome 

amount of ash between Portland and 

Olympia, is no longer closed, but 

blowing ash along that reach of 

highway remains a hazard to the stillheavy Memorial Day traffic. 

The Federal Aviation Administration lifted the restrictions imposed 

yesterday on air travel in the ashfall 

area. Air traffic in the vicinity of the 

volcano, however, is still restricted. 

A National Guard helicopter crew 

rescued five hikers who were in the Red 

Zone illegally. All five were nearly 

blinded by ash; one was hospitalized. 

Communities near the volcano have 

suffered from either too much or too 

little water during the previous week 

and a half. A flash-flood watch continues on the Toutle River and parts of 

the Kalama, Lewis, and Cowlitz Rivers. At Longview, water intakes from 

the Cowlitz River remain clogged and 

have caused the water system to go dry 

in part of the city. In eastern 

Washington, ash clogging the sewagetreatment plants in Spokane and 

Yakima has forced officials to dump 

raw sewage into the Spokane and 

Yakima Rivers. 

The Port of Portland reports that 

closing of the Columbia River to shipping has meant a revenue loss of $4 

million a day . The Port of Vancouver, 

across the Columbia from Portland, 

estimates loss,es of $1 million a day. 

The first autopsies conducted on victims of the May 18 eruption indicate 

that they were suffocated by hot ash or 

gas, not killed by burns or other injuries. 

Chronology of the First 100 Days 79 
A group calling itself 'The Friends of 

Washington" announced its intention 

to sell ash at $1 a packet to benefit 

search-and-rescue groups. It was, 

however, only one of many ash sellers 

in the stricken area. "Volcanic Ash-U 

Haul," one wag advertised. (By midsummer, many advertisements running 

in magazines and newspapers throughout the country were offering samples 

of Mount St. Helens ash at various 

prices.) 

Many large blocks of ice on and in 

the rubble north of the volcano might 

seem to have been thrown out by the 

May 18 lateral blast. Most, however, 

are actually chunks of glaciers that 

were part of the huge initial avalanche 

and were carried along with the avalanche debris to their present locations 

(fig. 37). Scientists paced off the 

diameter of one ice block that is mostly 

buried in debris overlooking the North 

Fork Toutle River and reported that it 

is about 300 feet across-the length of 

a football field. 

Farther west along the North Fork 

(beyond the avalanche debris) and in 

valleys where other major mudflows 

occurred, much of the bottomland is 

"flat as poured concrete" and just as 

gray (fig. 44). Mud from the mudflows 

of May 18 now fills most depressions 

and is still too soft to walk on in many 

places. 

USGS hydrologists today completed 

their first appraisal of the debrischoked Cowlitz River channel downstream from the mouth of the Toutle 

River. They found that mud and debris 

from the Toutle had reduced the depth 

of the Cowlitz channel by as much as 

12 to 15 feet and probably had accounted for about 40 million cubic 

yards of new flood-plain deposits and 

channel fill between the Columbia 

River and the mouth of the Toutle 

River. 

80 The First 100 Days of Mount St. Helens 

FIGURE 44.-The May 18 mudflows from 

Mount St. Helens reached levels much 

higher than those of any earlier recorded 

floods in the major valleys that carried 

them. (See the highest mud marks on the 

tree in the foreground and on trees in the 

right background.) When the mudflows 

receded, they left tangled masses of 

assorted debris such as this jumble of 

boulders, branches, and machinery 

pieces. The rock particles in the mud 

stripped and abraded the trees left standing and sharpened trailing tree limbs to 

tapered points. As the mud settled out of 

the receding floodwater, it filled and 

buried former depressions and left much 

of the valley floor "flat as poured concrete." In this view, looking downstream 

along the Muddy River 9 miles southeast 

of Mount St. Helens, a hydrologist 

(yellow figure on boulder in center of 

background) is surveying the mud marks 

to determine the downvalley slope of the 

mudflow at its highest position. (Photograph by Philip Carpenter, USGS, June 

4 1980.) 
Yakima reopened its downtown district today. Officials said that the 

citizens have done a remarkable job of 

"pitching in" and cleaning up. In the 

city, a block-by-block cleanup was 

organized and supervised by "block 

captains." Outside of town, property 

owners volunteered parts of their land 

as dumps for ash cleared from the city. 

Tuesday, May 27 

E Day Plus 9 

Seismicity was very low during the 

day, and eruptions of mixed ash and 

steam were mild. 

USGS scientists examined ash from 

Sunday's eruptions and found it to be a 

mixture of pumice, glass shards, 

crystal fragments, and fragments of 

older rock- similar to the composition of the May 18 ash. Field crews saw 

younger pyroclastic flows on top of 

the May 18 deposits. The pumice in the 

newer deposits is of two types-one a 

light-colored, frothy rock and the 

other darker and more dense. 

As the ash from last Sunday's eruption dries out, motorists along Interstate Highway 5 find that problems 

with visibility and clogged air cleaners 

are increasing. The Washington State 

Patrol imposed an emergency speed 

limit of 25 miles an hour, but, according to reporter Kerry Webster of the 

Tacoma News Tribune, it was being ignored by so many impatient drivers 

that "dust clouds were spread for miles 

obscuring both sides of the highway." 

State Patrolmen were greatly 

hampered in enforcing the new regulation because speeders were creating 

dense "smokescreens" of ash dust. 

Finally, according to Webster, after a 

multicar accident had delayed northbound traffic for more than 1 hour, 

truckdrivers took matters, into their 

own hands. Communicating by 

citizen's band radios, they maneuvered 

their rigs into three-abreast form~tions 

and formed moving roadblocks traveling at the emergency speed limit. The 

trios of trucks spaced themselves about 

7 miles apart, just about far enough for 

the dust from one convoy to settle 

before the next arrived. A State Patrol 

sergeant who was interviewed by 

Webster reported that the accident rate 

dropped immediately and that the dust 

began to clear. He added that, although the State Patrol did not condone the truckers' action, it certainly 

kept the highway open and probably 

saved some lives. 

Gifford Pinchot National Forest 

Supervisor Robert D. Tokarczyk today 

announced preliminary estimates, 

prepared by his staff, of damage 

caused by the Mount St. Helens eruption (fig. 45). The total loss of $114 

million worth of timber and resources 

within the national forest, not including damage to private timberlands, 

is as follows: 

• One billion board feet of timber, 

valued at $100 million, has been 

damaged or destroyed. This amount 

is nearly a thousand times as much 

timber as the Lassen volcanic eruption of 1915 destroyed. 

• Two lakes, Crane and Hoo Hoo, 

covering a total surface area of 6 

acres, perhaps have been destroyed. 

Spirit Lake and 26 other lakes have 

been severely damaged. No 

estimates were given of how long it 

might take for aquatic life to return 

to the lakes. 

• Valley floors of the North and South 

Forks of the Toutle River, Pine 

Creek, and the Muddy River have 

been buried by mudflows, and Coldwater Creek has been severely 

disrupted, as have the lower reaches 

of Spirit Lake tributaries-a total of 

152 miles of streambed. Forest Service biologists surmised that only 

pockets of aquatic life survive in the 

297 miles of heavily damaged 

streams. In addition, more than 

2,000 miles of stream channels were 

moderately or lightly damaged. The 

damage to stream channels will be 

especially disastrous to fish, including the anadromous species that 

spawned in these waters. 

• About 59,200 acres of deer and elk 

habitat reportedly have been completely or almost completely 

defoliated. An additional 62,080 

acres have been moderately damaged. An estimated 2,000 blacktailed deer have been killed, as were 

300 elk, 30 bear, and 12 mountain 

goats. Mount St. Helens' ptarmigan 

population, the southernmost 

known in the Cascade Range, prob-· 

ably has been destroyed. (This 

estimate does not take into account 

the smaller mammals, birds, reptiles, 

and amphibians that have been 

killed. Wildlife loss is not included 

in the $114 million damage figure.) 

• Twenty-seven Forest Service recreation sites in the devastated area have 

been destroyed; the largest of these 

was Spirit Lake Campground. AU 

Forest Service administrative build-· 

ings in the blast area, including the 

Visitor Center and the Spirit Lake 

Work Center, have been destroyed 

totally. The St. Helens Ranger Sta-· 

tion has been abandoned. Four private areas under Forest Service use 

permit, primarily used as summer 

camps for organizations, also have 

been destroyed. 

• Sixty-three miles of road within the 

blast and mudflow areas have been 

totally obliterated, and 154 miles of 

paved road and 1,560 miles of gravel 

road have been covered with 1 to 8 

inches of ash. Seven permanent road 

bridges, five logging-road bridges, 

and five trail bridges are known to 

have been destroyed. Also 97 miles 

of national forest trails have been 

obliterated, and 30 miles are covered 

with ash. 

Governor Ray estimates that total 

eruption damage, of which national 

forest losses are but a small part, is 

"$1.1 billion and might go higher." 

Flash-flood warnings for the Cowlitz 

River were cancelled today by the Na-· 

tional Weather Service. The flood 

watch for the Toutle is still in effect. 

The death toll now stands at 21. 

Sixty-eight are still missing. 

Chronology of the First 100 Days 81 
82 The First 100 Days of Mount St. Helens 
B 

EXPLANATION 

Unaffected area, 

forested and logged 

Pyroclastic or debris flow 

with dammed marginal lakes 

Damaged standing timber 

and downed or 

blast- removed timber 

Valley mudflow 

FIGURE 45. - A shaded relief map of the Mount St. Helens vicinity after the devastating 

May 18 eruption and before (inset).(Painting by Dee Molenaar, USGS.) B, Map labeling features shown in A. 

Chronology of the First 100 Days 83 
Wednesday, May 28 

E Day Plus 10 

The amount of ash in the eruptive 

plumes has been generally decreasing 

since the last big ash eruption of May 

25, and little was emitted today. 

Although the weather has been poor 

for viewing the volcano, radar images 

by the Oregon Army National Guard 

showed an area that could be either a 

dome or a ridge of ash and pumice 

within the large amphitheater and 

south of its open end. During the night, 

observers using light-enhancing 

binoculars reported seeing bright spots 

in the crater, which led to speculation 

that molten lava may be nearing the 

surface of the crater floor. 

Seismicity was low, and quakes were 

centered near Mount Margaret (fig. 7) 

to the north. Although two earthquakes were of magnitudes 4.0 and 

3.8, seismologists found no indication 

that these were directly connected with 

the eruption of Mount St. Helens. 

An evaluation committee, headed 

jointly by John Eliott Allen, professor 

emeritus at Portland State University, 

and retired Oregon State Geologist 

Ralph S. Mason, was formed to process applications for permission to conduct scientific research in the closed 

areas around Mount St. Helens. The 

committee was charged with making 

certain that the applications were for 

legitimate scientific research by competent scientists. 

The Mount St. Helens Technical Information Network issued its first 

bulletin-"The Nature of Mount St. 

Helens Ash." The ash from the May 18 

eruption, it says, consists of three 

layers. The bottom layer, which 

erupted first from the volcano, is a 

dark-gray ash composed of tiny fragments of older rocks and mineral 

crystals. The middle layer is a mixture 

of pumice and crystal fragments. The 

top layer, which forms the bulk of the 

ash that overlies much of eastern 

Washington and Idaho, is a light-gray 

ash composed mainly of fine particles 

of volcanic glass and mineral crystals. 

Geologist Washburn of the Washington Department of Transportation, 

stationed at Yakima, described the 

thickness of the three layers that fell on 

that city as about one-sixteenth inch for 

the dark basal layer, about one-half 

inch for the middle layer of "beachsand-size" particles, and only a "final 

dusting" of the upper fine, light-gray 

ash. 

Although too few analyses of the ash 

have been made to predict long-term 

effects, two fears were allayed. First, 

the ash is not sufficiently acidic to form 

"acid rain" or to increase the acidity of 

streams and lakes markedly. Second, 

the fluorine content is low; thus, the 

amount of fluorine leached from the 

ash will not be significantly greater 

than the amount of fluorine found in 

fluoridated city water systems. The 

amount of free silica in the ash, which 

might constitute a long-term health 

problem, and the quantity of trace 

elements are still being studied and 

debated. 

In its second bulletin, the Technical 

Information Network gave "Precautions for Handling Volcanic Ash." 

These precautions include moving the 

ash only in well-ventilated areas or 

outdoors, keeping it wetted if possible, 

and using dust masks to protect respiratory systems. 

All of Washington and eight Idaho 

counties are now considered disaster 

areas by the Federal Emergency 

Management Agency. About 300 

houses in western Washington have 

been destroyed or badly damaged, 

mostly by floods and mudflows, 

according to estimates prepared by the 

American Red Cross and the Skamania 

County Assessor. The Washington 

Department of Emergency Services 

estimated private timber loss at about 

$143 million. 

The death toll reached 22 when one 

man, hospitalized earlier for burns, 

died today. 

84 The First 100 Days of Mount St. Helens 

Thursday, May 29 

E Day Plus 11 

An Air Force SR-71 reconnaissance 

aircraft today flew a mission to take 

photographs showing topographic features of the altered mountain. Radar 

imagery obtained by the Oregon Army 

National Guard and reportedly showing a recently formed hump on the 

floor of the Mount St. Helens crater led 

to speculation that the volcano may be 

producing a lava dome. The presence 

of a lava dome, however, could not be 

checked by direct observation because 

steam and clouds permitted only occasional glimpses into the crater. 

Emergency-services officials announced a critical need for hay and 

grain to feed animal survivors, both 

domestic and wild. 

Because of the danger of flooding on 

the Cowlitz River, the USGS issued an 

updated Hazards Watch to local officials. They pointed out that the 

capacity of the Cowlitz River channel 

has been reduced about 85 percent, 

from about 76,000 cubic feet per second down to about 10,000 cubic feet 

per second, a flow rate that usually is 

exceeded at least once every year. 

Airborne search-and-rescue operations were ended at 5:00 p.m. today. 

Altogether, nearly 18,000 manhours 

have been spent in the extensive and 

dangerous search for victims and survivors. More than 100 people have 

been rescued since the May 18 eruption. The toll stands at 22 dead and 71 

missing. Ground searches, however, 

continue. 

Friday, May 30 

E Day Plus 12 

The crater w~s cloud free for probably the first time since May 18, and 

the crater floor was visible through the 

steam plumes that rose from dozens of 

vigorously fuming vents 'within. Observers could see that the hump 
detected by radar is not a dome but is, 

instead, a ridge, or "rampart," of ash 

and pumice that has built up between 

the most active steam vents and the 

open end of the amphitheater on the 

north. South of the rampart, an irregular crater (fig. 46) occupies only a 

fraction of the broad floor of the huge 

May 18 crater. In addition to the steam 

spewing from the vents, a burst of ash 

rises now and then, and, even less 

often, a block of pumice is thrown upward and tumbles back into the crater. 

According to the tiltmeters that have 

survived the two major eruptions, the 

ground near the volcano has deformed 

only slightly. One tiltmeter about 4 

miles south-southwest of the volcano's 

center has shown an almost continuous 

slight inflation of the volcano since 

before May 18; instruments farther 

away show little or no change. 

Seismographs today recorded a few 

periods of weak harmonic tremor, 

which died out within a few hours. 

Costs for flood-control, navigation, 

and water-supply rehabilitation projects necessitated by the eruption of 

Mount St. Helens could reach $219 

million, according to preliminary 

estimates made by the Corps of Engineers. Of this amount, $44 million will 

be needed to restore the Columbia 

River channel, where 22 million cubic 

yards of material will have to be 

removed. The shoal near the mouth of 

the Cowlitz River extends farther 

upstream in the Columbia than 

engineers first believed. The channelfilling debris from the Cowlitz River 

may have caused the Columbia River 

itself to deposit much of its sediment 

load where it encountered the shoal. 

The Corps of Engineers estimated 

that the cost of clearing intakes and 

rebuilding or restoring water-supply 

systems in Toutle, Castle Rock, Longview, and Kelso will be about $14 

million. An additional $28 million will 

be needed to restore the Cowlitz River 

channel, including dredging an estimated 25 million cubic yards of 

FIGURE 46.-View of the "crater within a 

crater" between the May 25 eruption and 

the June 12 eruption, looking into the 

north-facing mouth of the main crater 

from the northeast. The smooth slope in 

the right foreground is a rampart of 

pyroclastic debris and ash that built up in 

front of the main eruption center, which 

is at the base of the large steam plume. 

The rock ridge on the left side is old 

volcanic rock, formerly buried, that was 

exposed for the first time in centuries by 

the May 18 eruption. (Photograph by 

Terry Leighley, Sandia Laboratories, 

June 4, 1980.) 
volcanic and flood debris. All Corps of 

Engineers dredges on the west coast 

have been assigned to work on rivers 

affected by the eruption. 

USGS hydrologists have now made 

preliminary calculations of the size of 

the May 18 mudflows down the major 

valleys radiating from Mount St. 

Helens. The volume of water in these 

mudflows is estimated to have been 

more than 100 million cubic yards, or 

more than 20 billion gallons-enough 

to supply household water for every 

person in the United States for 1 day. 

The mudflow from the South Fork 

Toutle River, which crested at the 

steam-gaging station on the main Toutle River about 11:00 a.m. on May 18, 

2.5 hours after the main eruption 

began, reached a peak stage (highwater level) that would be equivalent 

to a water-flow rate of 46,000 cubic 

feet per second, or 1, 700 cubic yards 

per second; the actual flow rate was 

less (by an unknown amount), however, because the mud slurry could not 

flow as fast as water. 

The mudflow from the North Fork 

Toutle River, which destroyed the 

Toutle River gage about 6:00 p.m. on 

May 18, left high-water marks that indicated a peak flow roughly two to 

three times that of the previous 

mudflow from the South Fork. The 

peak stage near the mouth of the Toutle River was equivalent to a water 

discharge of about 100,000 cubic feet 

per second, but, again, the actual rate 

of flow into the Cowlitz was less 

because of the lower velocity of the 

mud slurry. 

Hydrologists also completed and 

released to emergency-services agencies the first computations of probable 

flood levels in the mud-choked Toutle 

and Cowlitz River valleys if various 

amounts of storm runoff were to occur. They found that a wedge-shaped 

mass of mud even extended upstream 

in the channel of the Cowlitz for 2.5 

miles above the mouth of the Toutle 

River; the volume of this upstream 

deposit, however, was only a small 

fraction of the amount deposited 

downstream. The volume of sediment 

left in the channel and on the flood 

plain of the Cowlitz River between 

Castle Rock and the Columbia River 

(not including the vast, but unknown, 

amount that flowed through to the 

Columbia) is estimated to be as much 

as 40 million cubic yards. This volume, 

if it were the concrete that the wet mud 

resembles, would be enough to pave 

an eight-lane highway between Mount 

St. Helens and New York City. 

Daily checks of 40 hospitals in 

Washington, Oregon, Idaho, and 

Montana have failed to reveal any 

severe respiratory ailments caused by 

ash from the May 18 eruption, according to information released by the National Center for Disease Control. 

Ray Jennings, the south-side resident 

who had resisted earlier evacuation attempts, and his four dogs were airlifted 

out of the Red Zone today by a National Guard helicopter. He had been 

in his cabin on the volcano's flank since 

before the May 18 eruption, but, 

because his whereabouts were known, 

he was never on the list of missing persons. 

Saturday, May 31 

E Day Plus 13 

Travel in the Northwest is nearly 

normal again. Only four sections of 

State highways are still closed, and two 

of those allow local traffic. No airports 

are closed on account of ash. On the 

Columbia River, nearly 550,000 cubic 

yards of material have been dredged to 

form a shallow navigation channel, 

which has allowed 18 vessels to move 

upriver and 10 to move downriver. 

The volcano steamed more strongly 

today than it has in the immediate 

past; clouds reached an altitude of 

15,000 feet. Seismic activity was low, 

and small earthquakes-none greater 

than magnitude 3-centered near 

Mount Margaret, 8 miles northeast of 

Mount St. Helens. 

The volcano is still emitting 

sulfurous gases, even though there 

were no eruptions of ash; the emission 

86 The First 100 Days of Mount St. Helens 

rates are several times higher than 

those measured before May 18. Concentrations of sulfur dioxide (S02) 

measured by Thomas Cassadeval on 

May 26 and 31 averaged about 150 

tons a day, in contrast to the few tens 

of tons a day measured before May 18. 

The team of gas specialists reports that 

the volcano is also emitting at least as 

much hydrogen sulfide (H2S) as S02. 

Forest Supervisor Tokarczyk announced that the Forest Service probably will recommend that Mount St. 

Helens and some of the devastated areas 

surrounding it be designated a "National Volcanic Area." Others are proposing that the area become a national 

monument or a national park. 

The Mount St. Helens Technical Information Network issued two bulletins today; one gives advice on driving in heavy ash areas (drive slowly; 

change oil, air filters, and other filters; 

and clean brakes occasionally), and the 

other suggests that exposure to the ash 

may have reduced the insect population significantly. Honey bee colonies, 

although damaged, apparently were 

not obliterated. 

Rod Preston of the Washington State 

University Animal Sciences Department reported that the only elements in 

the May 18 ash that concern animal 

scientists are copper and molybdenum. 

Although the concentrations of these 

elements in the ash are small, they 

might cause illness in livestock that eat 

feed containing unusually large 

amounts of ash. 

At the month's end, no lava has appeared at the surface. Recently, 

however, there have been several night 

observations of incandescent rocks, 

which probably are caused by hot 

gases streaming through the vents from 

a magma body not far below. 

Sunday, June 1 

E Day Plus 14 

The month has opened quietly. The 

volcano continues to vent steam, 

which rises in clouds to about 12,000 

feet. Poor weather has prevented good 
aerial observation, but field crews, 

transported by helicopters, continued 

making ground observations (fig. 47) 

and deploying monitoring instruments 

today. Measurements of the "new" 

Spirit Lake revealed that its depth is 

now about 100 feet or less, instead of 

its former depth of about 200 feet. The 

lake-water temperature was measured 

at 97°F (36 °C) at the surface and 95 op 

(35°C) on the bottom. 

Earthquakes were small and few, and 

harmonic tremor, which returned to 

the mountain a few days ago, decreased in amplitude by about twothirds early this morning. This 

decrease could mean that movement of 

magma under the volcano is subsiding, 

but no one knows. 

Winds blowing at about 25 miles an 

hour plagued parts of eastern 

Washington and northern Idaho by 

redistributing ash deposits from the 

May 18 eruption. Poor visibility 

caused temporary closure of sections of 

two highways in east-central 

Washington. 

USGS geologists warn that, although the volcano appears to be 

relatively quiet now, it still remains 

dangerous to anyone nearby. If a lava 

dome were to build in the crater-an 

event that would be in character for 

this volcano-the dome building 

would likely be accompanied by more 

explosive eruptions, pyroclastic flows, 

and mudflows. 

Search dogs have been used in 

ground searches for survivors and victims of the May 18th eruption; however, these searches have now been 

suspended. From now on, special 

search-and-rescue missions will be conducted only if the last known location 

of a possible victim can be closely 

fixed. The count now stands at 22 dead 

and 53 still missing. 

Monday, June 2 

E Day Plus 15 

Both eruptive activity and earthquake activity are quite low today. 

Ash plumes barely reach the crater 

rim, but the ash from the May 18 eruption has circled the Earth in the highaltitude air mass. A meteorologist with 

the Air Resources Laboratory of the 

National Oceanic and Atmospheric 

Administration said today, 'The ash is 

over the Aleutian Islands in Alaska, 

possibly up to the North Pole, and then 

extends south through Canada." He 

added that the ash is in the 20,000- to 

40,000-foot altitude zone and is in such 

low concentrations that it is invisible to 

the eye. 

Scientists generally agree that, 

although the worst dangers from 

Mount St. Helens may be over temporarily, the volcano remains dangerous. USGS geologists Crandell and 

Mullineaux, in a hazards statement, 

said, "At present there is a relatively 

high degree of risk in working in areas 

near the volcano. The degree of risk 

varies according to wind direction (for 

ash) and according to topography (for 

pyroclastic flows). By comparison with 

an ashfall of about 4,000 years ago 

[table 2], a major eruption now could 

result in the deposition of as much as 3 

feet of ash at a distance of 20 miles and 

1 foot at 50 miles. The sector affected 

would depend on wind directions and 

strengths. 

"Pyroclastic flows tend to move 

down valleys and other depressions, 

and clouds of hot ash accompanying 

them may affect areas beyond the sides 

and ends of pyroclastic flows. There is 

some risk even beyond the pyroclastic 

flow limits shown on [previous] volcano hazards maps because of the 

possibility that some will occur that are 

longer than those of the past. 

"A sector directly north of the 

volcano will be especially hazardous if 

and when a dome is formed in the 

crater because of the possibility of 

strong lateral blasts. 

"There is no unequivocal boundary 

anywhere around the volcano that 

sharply divides areas of risk from areas 

of no risk. Risk increases toward the 

volcano in all directions for all kinds of 

volcanic events, but the rate of increase 

is different for different kinds of 

volcanic events. 

"It is not possible to predict now 

what the volcano will be doing a 

month from now, or even a week from 

now. It should be assumed, for planning purposes, that a major explosive 

eruption could begin and progress to a 

climax very rapidly, so there would be 

essentially no time for warning." 

Governor Ray today changed the executive order that established the 

restricted zones around Mount St. 

Helens (fig. 13). The exact boundary of 

the Red Zone was defined, and new 

rules for entry were set forth. The 

Governor also asked today for more 

Federal aid, saying, "Clearly, neither 

this State nor its local sub-units of 

government can continue [on their 

own] to cope with the physical effects 

of the disaster, let alone the financial 

burden." 

A second manufacturer of dust 

masks suitable for use in volcanic areas 

donated 160,000 of them to the State of 

Washington to distribute to people in 

the "ash belt." 

A new report by the Mount St. 

Helens Technical Information Network 

said that, when the May 18 ash is 

viewed under the microscope, two 

main ingredients can be seen: (1) 

pumiceous volcanic glass and (2) 

crystal fragments of the mineral 

feldspar, which is composed of 

sodium, calcium, aluminum, and 

silica. These ingredients are "new" 

(juvenile) volcanic material, mixed 

with variable, small quantities of other 

minerals and particles of the "old" 

volcanic rock torn from the walls of 

the eruptive vent. 

When USGS researchers examined 

the ash, they found only minute 

amounts of the free-silica minerals 

(quartz, cristobalite, tridymite, flint, 

chalcedony, and opal) that have been 

of such great concern as a potential 

long-term hazard to the health of those 

breathing the ash. 

The ash is about as abrasive as finely 

crushed window glass. Its density is 

about two or three times as great as 

that of water, but it is almost insoluble 

in water. For that reason, it should 

Chronology of the First 100 Days 87 

FIGURE 47.-Fieldwork in the avalanche deposit. A, Geologists collecting samples 

at a weakly steaming fumarole in the 

May 18 debris-avalanche deposit. The 

view here is eastward; the fumarole is in 

the valley of the North Fork Toutle 

River, just south of the destroyed Coldwater II observation site and about 5 

miles north-northeast of the crater's 

center (see fig. 51). The debris-avalanche 

deposit, derived from the upper northern side of the mountain, here is about 

300 feet thick. Part of a new pond, 

covered with floating pumice and wood 

debris, is at the lower right. (Photograph 

by David Frank, USGS, June 7, 1980.) B, 

USGS geologist Robert L. Christiansen is 

dwarfed by the jagged landscape formed 

by debris from the avalanche and a 

tangle of uprooted trees at this site north 

of the western lobe of Spirit Lake. The 

view here is toward the southwest. 

(Photograph by Robert L. Smith, USGS, 

May 30, 1980.) 

weather slowly, giving up some plant 

nutrients such as lime, potash, and 

phosphorous in the process. Some 

potentially harmful substanceschiefly acids and salts-cling to the 

tiny particles, but the amounts of these 

substances are small. 

The USGS completed a new topographic map showing preeruption 

features in a 2, 700-square-mile area 

surrounding the volcano. An accurate 

single map showing features in the 

degree of detail needed for posteruption planning and rehabilitation had 

not been available previously. (Some 

earlier USGS maps showing features at 

a larger scale and in more detail are 

badly out of date with regard to roads, 

trails, and logged-off tracts.) 

Athough the death toll remains-at 

22, the list of missing persons is shrinking as some people, initially reported 

missing by worried friends or relatives, 

come forward to tell authorities that 

they survived. 

Tuesday, June 3 

E Day Plus 16 

Harmonic tremor, which has been 

fluctuating in a range of low 

amplitudes for the past several days, 

fell off to a very low level last night; 

then, about 2:00 a.m., it began to increase strongly. The University of 

Washington seismology center contacted USGS scientists in Vancouver 

and informed them that this pattern of 

harmonic tremor was similar to the one 

that had preceded the May 25 eruption. Furthermore, no earthquakes 

("none at all") have occurred since 

Mqnday morning, reminiscent of the 

gradual decrease in earthquakes that 

took place before the May 18 eruption. 

Because of these similarities, scientists 

are keeping an especially careful watch 

on the volcano. As of midnight, 

however, no eruption is evident. 

Measurements of sulfur dioxide production from Mount St. Helens today 

show that the volcano is emitting 

about 200 tons of S02 a day. This 

emission rate is about the same as the 

rates measured in late May. 

Two men, an injured professional 

photographer and his uninjured helper, 

were picked up from the flank of Mount 

St. Helens by a Forest Service 

helicopter and brought to Vancouver 

early this evening. They reportedly 

have been in the restricted zone taking 

pictures and eluding airborne 

observers most of the time since before 

the May 18 eruption. They may face 

both State and Federal prosecution for 

deliberately entering the restricted 

area. 

The Corps of Engineers reports that 

its plans for flood control and water 

rehabilitation include not only dredging the rivers and raising dikes along 

the Cowlitz but also constructing rockfill dams and settling ponds on the two 

forks of the Toutle River. The dams 

and settllng ponds are intended to 

catch additional sediment eroding from 

the area of the volcano blast and carried by the two river forks and, 

thereby, to lessen the filling of channels 

downstream. The captured sediment 

reportedly will be removed from catchment ponds later by earth-moving 

equipment. 

The National Weather Service office 

in Seattle began issuing "St. Helens 

plume trajectory forecasts" warning 

where ash will fall if more erupts. 

Enough rain fell today in Portland to 

permit cancellation of an "air-pollution 

alert" that has been in effect since the 

May 25 eruption dusted that city with 

fine ash. 

Automatic banking machines are the 

latest victims of the ash. Two bank 

machines in Yakima and 40 in Portland 

reportedly have been disabled by ash 

that has blown into their mechanisms. 

The ash may be useful in some 

manufacturing processes, however. A 

California firm announced that, when 

the ash is mixed with a plastic resin, it 

forms a porcelainlike material that can 

be used to make bathroom fixtures and 

other products. An instructor at 

Spokane Falls Community College 

(near Spokane) previously had 

reported that the ash is a "ready-made" 

glaze material for some ceramic products. 

Wednesday, June 4 

E Day Plus 17 

The volcano's plumes continued to 

be principally steam, which rose 

regularly to altitudes of 12,000 to 

14,000 feet. Earthquake activity was 

low. Harmonic tremor, which yesterday was stronger than it has been at 

any time since May 25, decreased in 

amplitude. Upward (inflationary) 

tilting on the volcano's southern side 

continues at a very slow rate, quite 

unlike the rapid bulging of the northern side before the May 18 eruption. 

Scientists continue to warn that the apparent quiet may be misleading-the 

volcano may be poised for another 

eruption. Despite the continuing apprehension of scientists, however, the 

Red Zone is scheduled to reopen today 

for loggers, residents, and news reporters if the volcano remains quiet. 

A hospital patient died today of 

burns received during the May 18 eruption. A body discovered about 3 miles 

west of the crater was identified as that 

of a missing Portland photographer, 

Robert Landsburg. These two events 

brought the death toll to 24 and reduced 

the missing persons total to SO. 

Chronology of the First 100 Days 89 
Thursday, June 5 

E Day Plus 18 

Eruptive and seismic activity at 

Mount St. Helens remained low today. 

USGS and University of Washington 

scientists have concluded that the 

ominous pattern of earthquakes and 

harmonic tremor earlier this week, 

which had been thought to indicate an 

impending eruption, "must be considered a false alarm." 

The Forest Service announced that it 

will set up seismographs at the visitor 

centers on Interstate Highway 5 

southwest of Mount St. Helens and at 

Lewis and Clark State Park northwest 

of the mountain, so that visitors can 

follow the recording of the volcano's 

earthquakes as they occur. 

Washington State University scientists in Pullman have determined, on 

the basis of experimental work with 

chickens, that the ash is not acutely 

toxic to domestic animals. Scientists 

are still concerned, however, that 

eating and breathing ash will have 

some effect on larger animals. 

There is no evidence that food raised 

in ashfall areas p9ses a health threat, 

the Technical Information Network reports, but careful cleaning of fruits and 

vegetables is recommended. 

The Coast Guard office in Portland 

reports that dredging of the Columbia 

River shoal has deepened the navigation channel to 33 feet, more than three 

times deeper than the 10-foot depth left 

after the May 18 and 19 floods from 

the Cowlitz River. 

Colleagues of photographer 

Blackburn, who died in the May 18 

eruption, found one of the remotecontrolled cameras that he had been 

operating from Coldwater I observation station. Film from the battered 

camera was processed, but it haq been 

fogged by the heat and showed no clear 

images of the May 18 blast that killed 

Blackburn. 

Friday, June 6 

E Day Plus 19 

Seismic activity remained low, and 

plumes consisting mostly of steam rose 

only about 15,000 feet above sea level. 

Loggers and property owners 

"swamped" State offices today seeking 

permits to get into the Red Zone, as 

Governor Ray's most recent executive 

order allows. 

Emission of S02 has increased significantly between June 3 and today. Today's measurement of about 900 tons a 

day is nearly four times greater than 

the June 3 measurements. 

Researchers from the National 

Center for Disease Control who 

analyzed four samples of volcanic ash 

for free silica found concentrations to 

be low-about 6 percent of the 

respirable size (less than 10 microns) by 

weight. Of this, two-thirds was in the 

form of the mineral cristobalite, and 

one-third was quartz. (Some chemical 

analyses previously had reported a 

high percentage of silica in the ash; 

most silica, however, was chemically bound in various other minerals, 

and it was not the dangerous "free 

silica," or Si02 .) Although exposure to 

free silica for many years can cause 

silicosis and exposure to large concentrations for a short time can cause an 

acute form of the disease, Federal 

health scientists do not think that 

short-term exposure to the ash is a significant public health hazard. They 

suggest that persons working in the 

ash, as well as those having respiratory 

diseases, should wear dust masks. 

Children should be cautioned not to 

play strenuously in ash-filled air, and 

they should not be allowed to play in 

deep ash. 

Tourists, the lifeblood of Washington's ocean beach communities, are 

"staying away in droves" after the traffic jams and accidents, strandings, and 

other problems that ashfall from the 

May 25 eruption created for Memorial 

Day travelers. The Ocean Shores 

Chamber of Commerce, according to 

the Tacoma News Tribune, reports 

that business in that normally busy 

resort community is "down 60 to 70 

percent." 

One huge industrial vacuum cleaner 

was operated for 2 days to remove 17 

tons of volcanic ash from the roof of 

the Yakima City Hall. 

90 The First 100 Days of Mount St. Helens 

Saturday, June 7 

E Day Plus 20 

Mount St. Helens continued its low 

eruptive activity today, sending steam 

plumes, but little ash, to an altitude of 

about 11,000 feet. No earthquakes 

were recorded, and harmonic tremor 

was as low as it has been since May 18. 

USGS water-quality specialists say 

that the chemical constituents of 

Mount St. Helens ash should not affect 

water supplies significantly. They 

soaked ash samples collected in 

Spokane and Richland, Wash. (near 

Pasco) (fig. 29G), and in Helena and 

Kalispell, Mont., in water for 4 hours 

and then analyzed the leachate (soaking water). The test simulated the effects of rain falling on one-half inch of 

ash. The test was designed to show a 

"worst case" -that is, to produce the 

highest likely concentrations of 

chemicals in water draining through 

the ash. 

The first water draining through the 

ash did contain some chemical ions·(including chloride, fluoride, sulfate, ammonium, manganese, boron, cadmium, and selenium) in concentrations 

that exceed the water-quality standards 

for public water supplies. Later soakings yielded much lower concentrations of these ions. Under natural conditions, reactions within the soil and 

dilution by other ground water or sur-_ 

face water would lower these concentrations in the runoff or in water infiltrating from ashy lands. 

Manganese, one element that could 

prove to be annoying, was present in 

the leachate in concentrations as much 

as 100 times the recommended level. 

Although manganese could impart an 

objectionable taste to water and 

perhaps .cause staining of light-colored 

objects washed in affected water, it 

should not be a health hazard. 

Boron concentration in the leachate 

was as much as 2.5 times the maximum 

recommended for long-term irrigation 

of such boron-sensitive crops as apples 

and some berries. Under natural conditions, however, such strong concentrations would be unlikely to reach the 
roots of the plants before irrigation 

water had diluted them adequately. 

The ash could change acidity levels 

slightly but reportedly not enough to 

damage crops. The pH of the leachate 

was about 6.0 (very mildly acidic), 

slightly less acidic than the average for 

rainfall in the Northwest, which 

generally has a pH of about 5. 

The new State system for gaining entry to the Red Zone provides "blanket" 

30-day permits for logging corporations and other companies. To qualify, 

each company must: , 

• Have a method for identifying and 

locating each employee, agent, and 

(or) contractor authorized to be in 

the Red Zone. 

• Inform each employee of a predesignated escape route. 

• Monitor radio frequencies established by the local sheriff's department or other governmental agency 

for transmitting emergency signals 

about Mount St. Helens. 

• Check each authorized employee in 

and out daily. 

• Issue an identification card, tag, or 

other form approved by the Washington Director of Emergency Services to each worker. 

• Provide the foreman of each work 

crew with a two-way radio and require him to make regular contact 

with a central dispatcher. 

• Inform each worker that he must 

stay within a 15-minute walking distance of his vehicle. 

Weyerhaeuser, one of the largest 

owners of timberland in the Mount St. 

Helens area, reports that most of its 

downed timber seems to be salvageable 

and that the company expects to begin 

immediately restoring its equipment, 

facilities, and routes into the blowdown area. 

Loggers in ash-coated timber areas 

report that they must sharpen their 

saws about three times as often as they 

did before May 18. 

The Federal Emergency Management 

Agency closed most of its remaining 

disaster assistance centers in eastern 

Washington and northern Idaho this 

evening. Only the centers at Kelso, 

Spokane, and Moses Lake remain 

open. Agency officials report that 

more than 3,700 people have registered 

at centers in the two States to inquire 

about or apply for disaster assistance 

loans or grants or to seek counseling. 

Scientists are still warning that the 

volcano could explode or send out 

eruptions of pumice and ash. USGS 

geologist Richard Waitt said today that 

a larger eruption plume and a thicker 

ashfall are still "very possible. " 

Scientists in the field report the reappearance of small plants of the 

horsetail rush type, as well as small 

animals, in the devastated area. They 

also have seen fresh deer and cougar 

tracks in the ash. 

News reports remind the public that 

Mount St. Helens is not the only 

volcano now active. Mount Etna in 

Sicily is erupting and reportedly has 

killed nine people. Worldwide, probably 30 to 40 volcanoes are active now. 

Sunday, June 8 

E Day Plus 21 

Several nervous residents called the 

Mount St. Helens coordination center 

today to ask if the sharp lightning 

flashes visible over the volcano meant 

that it was erupting. It was not. 

The mountain remained quiet again 

today; only very low level harmonic 

tremor was recorded at the University 

of Washington seismology center. Rain 

and clouds kept observation aircraft 

grounded, but an Oregon Army National Guard airplane flew over the 

mountain to obtain radar and thermal 

infrared images. Radar showed the 

base of a steam plume that rose lazily 

through the rain clouds to an altitude 

of about 12,000 feet. The thermal infrared images showed a general 

heating, since late May, of the eruptive 

center that was active May 18. The images also showed that heat was still being emitted by the pyroclastic flows. 

Scientists used the sporadic periods 

of clear weather this weekend to 

reestablish some of the survey lines on 

the southwestern side of the mountain 

for ground-deformation studies. The 

lines are to be measured as regularly as 

weather conditions permit. 

Observers are watching closely for 

the formation of a dome-a buildup of 

extruded lava that is too pasty to flow 

far from the extrusion vent. A dome 

could signal a rebuilding of the mountain, although not necessarily the end 

of danger. Following previous eruptions, Mount St. Helens has formed 

other domes; the now-vanished Goat 

Rocks was probably the latest such 

dome (table 2). Dome-building activity 

in the inner (May 25) crater has been 

reported but not verified. 

Monday, June 9 

E Day Plus 22 

Steam plumes and some ash continue to be vented. No harmonic 

tremor was recorded today, and 

seismicity was low. New avalanches 

took place under the persistent cloud 

cover, but none was observed in progress. 

When observers were able to see into 

the crater, they noticed a new, 

crescent-shaped lake in the northern 

part of the crater floor. It was about 

1,000 feet long and 300 feet wide. 

On Friday (June 13), the moon will be 

at its closest proximity to the Earth 

since May 17, and strong tides will 

result. Although geologists generally 

agree that tides, by themselves, cannot 

cause volcanic eruptions, some concede that strong Earth tides might be 

"the straw that breaks the camel's 

back" if the volcano is already primed 

for an eruption. 

The persistence of ash from the May 

18 eruption has caused the Army to 

cancel its usual summer exercises at the 

extensive desert training center near 

Yakima. Normally, one or two battalions at a time would be using the 

Yakima Firing Center, but uncertainty 

about the effects of the dry, blowing 

ash on the health of soldiers and on 

precision equipment prompted the 

cancellation. 

Because volcano damage has been 

rare in this country, no one is certain 

how much of the private losses caused 

by the eruption will be covered by insurance. People who are listed as missing pose special problems for lifeinsurance companies and claimants. 

Chronology of the First 100 Days 91 
Tuesday, June 10 

E Day Plus 23 

The mountain remained quiet again 

today; only minor amounts of ash 

were vented in plumes of steam that 

rose less than 2,000 feet above the 

crater rim. No harmonic tremor and no 

earthquakes were recorded 

USGS scientist Arnold Okamura 

says that one tiltmeter on the southern 

side of Mount St. Helens has been 

showing a slight inflation of the 

southern flank for the past month. The 

rate of tilt has been relatively constant 

since about May 9, even through the 

eruptive periods of May 18 and 25. 

The Corps of Engineers reports that 

the dredge Art Riedel began operations 

in the mouth of the Cowlitz River. 

Previous dredging has been concentrated in the Columbia River navigation channel. 

Nearly 4,200 people reportedly had 

visited Federal disaster assistance 

centers in Washington and Idaho by 

this evening, when the centers in Spokane and Kelso were shut down. Plans 

call for the center at Moses Lake to be 

closed Thursday evening and for a new 

center to be set up in Centralia, Wash., 

that same day. 

Governor Ray, in an appearance 

yesterday before the U.S. Senate Appropriations Committee, had praise for 

the "timely warnings" about the Mount 

St. Helens eruptions. "We were warned 

of all possible consequences and tried 

to have a general plan, and as a result 

of that I believe many, many lives 

were saved," she said. 

No major population centers have 

reported serious problems with 

drinking-water quality as a result of 

volcanic ash, although some smaller 

water systems have been plagued by 

turbidity and equipment damage, nor 

has anyone reported toxic levels of 

metallic ions or other chemicals derived from ash in drinking water. 

However, washing away the ash taxed 

some water supplies, particularly at a 

time when many normal surface-water 

supplies were not usable. 

Wednesday, June 11 

E Day Plus 24 

No harmonic tremor, no unusual 

earthquake activity, and no strong 

eruption changed the even tenor of the 

day at Mount St. Helens. 

Officials of Federal agencies and the 

State of Washington told Congress today that the bill for damages caused by 

the Mount St. Helens eruptions will be 

about $2.7 billion. The total would 

have been even greater if volunteers 

had not assisted the State and Federal 

governments, according to the Washington Department of Emergency Services. Besides volunteer service groups, 

such as the Tri-County Search-andRescue Association, the Lower Columbia Amateur Radio Association, the 

Salvation Army, and the American 

Red Cross, many individual volunteers 

have been working steadily throughout 

the emergency. 

A machine specially designed to lift, 

comb, and shake ash-coated alfalfa is 

being manufactured in eastern Washington and is expected to salvage part 

of the hay crop in the "ash belt." 

Salmon can be killed if sharp ash 

particles damage their gills, according 

to a Washington Department of Fisheries investigation. The department 

concluded that fish probably could not 

survive a swim through the ash-filled 

Cowlitz River. 

The official death toll remains at 24. 

The removal of four more names from 

the list of missing persons has reduced 

its number to 46. 

Third Explosive 

Eruption 

Thursday, June 12 

E Day Plus 25 

The third explosive eruption of 

Mount St. Helens occurred tonight. It 

was preceded by a buildup of harmonic 

tremor, which began at low levels 

about midday and increased in 

92 The First 100 Days of Mount St. Helens 

amplitude throughout the afternoon. 

The University of Washington seismology center notified the Vancouver 

coordination center and the Washington Department of Emergency Services that a buildup in tremor similar to 

the one that preceded the May 25 eruption was occurring. A marked increase 

in the harmonic tremor was noted at 

7:05 p.m., and reports of an eruption 

cloud rising to an altitude of at least 

13,000 feet were received 5 minutes 

later. Tremor dropped off in strength 

immediately after the eruptive pulse and 

fluctuated at moderate amplitudes for 

more than 2 hours. 

This temporary lull was broken 

dramatically by a large increase in 

tremor amplitude at 9:11 p.m. Shortly 

thereafter, observers in a Forest Service 

airplane witnessed the very rapid climb 

of an eruption column to an altitude 

greater than 35,000 feet. About 400 

families living in the latest Red Zone 

were warned to evacuate, but many 

reportedy declined to do so. A flashflood watch was put in effect for the 

Toutle, Cowlitz, Kalama, and Lewis 

Rivers. 

National Weather Service radar 

observers in Portland tracked the 

eruption plume to an altitude of 50,000 

feet at 9:18 p.m. Forest Service airborne observers reported that the column was "several kilometers wide" at 

its base and was producing lightning. 

Cloud cover, however, prevented observers from seeing whether new mudslides or pyroclastic flows were occurring. The plume height as detected by 

radar fluctuated between about 15,000 

and 35,000 feet above sea level until 

about midnight, when it diminished. 

Prevailing winds are carrying ejected 

ash to the south and southwest, and 

pumice particles as large as one-half 

inch across are falling "like hailstones" 

on Cougar, about 11 miles downwind 

from the volcano. Ashfalls began in 

Vancouver and Portland about 10:50 

p.m. and are still continuing as of midnight. 

Recognition of the preemption pattern of the harmonic tremor warned 
emergency-services officials of the impending eruption and allowed them to 

warn the public quickly. No casualties 

were reported. 

Friday, June 13 

E Day Plus 26 

The eruption that began last night 

apparently continued sporadically into 

the early hours of this morning. At 

2:02 a.m., the Portland office of the 

National Weather Service reported 

that its radar showed "a heavy plume" 

up to 15,000 to 16,000. feet above sea 

level. The pilot of the Forest Service 

observation airplane reported at 2:31 

a.m. that, at his position 22 miles 

northwest of Pendleton, Oreg., he was 

"in ash" at an altitude of 24,000 feet 

and that the plane was being peppered 

with pumice particles as large as oneeighth inch in diameter. (The plane 

outdistanced the eastward-moving ash 

and landed safely in Spokane after 

having been warned away from Portland area airports). At 4:00 a.m., the 

National Weather Service radar 

showed the plume top to be at 13,000 

feet and the ash content to be slightly 

reduced. At 6:00 a.m., the University 

of Washington seismology center reported that steady, low-level harmonic 

tremor was being recorded. 

The Federal Aviation Administration closed airspace and airports as far 

away as 150 miles from Mount St. 

Helens (Portland International Airport 

reopened about 7 hours later). The National Weather Service issued travelers' 

warnings for anyone using roads 

within 50 miles of the mountain. By 

6:00a.m., the Washington Department 

of Emergency Services had announced 

that all Red Zone entry permits had 

been suspended and that only permanent residents would be allowed in the 

area. This action will keep more than 

200 loggers out of areas where they had 

resumed work only a few days ago. 

Although last night's eruption was 

shorter than the one on May 25 (about 

5 hours as opposed to more than 12 

hours), it may have spewed more ash, 

according to USGS geologists. The 

prevailing winds at most altitudes 

reached by the ash plume seem to have 

spread the ash mostly in the quadrant 

extending south to west from the 

volcano (fig. 48). Traces of ash, 

however, were reported falling as far 

away as Seattle to the north and Salem 

(and perhaps Medford) to the south. 

Vancouver received about one-eighth 

inch, and Portland received about onesixteenth inch. The coastal city of 

Tillamook, Oreg., nearly 100 miles 

southwest of Mount St. Helens, apparently lay directly in the path of the 

plume that reached the Oregon coast. 

As much as one-eighth inch of ash 

reportedly fell on that city, but little or 

none fell on nearby communities to the 

north and south. 

Seattle 

• Olympia 

WASHINGTON 

, _ MOUNT ST. HELENS 

----- ''-.. ......... ~20 

0 

I 

0 

OREGON ~ 10 s 10 

1//2~~ 

10 

I 

I 

20 

?// II \ ( 2 6 

7 4 6 ,.._...---

20 30 

I I 

I I I 

40 

. Vancouv~ 

'~-,. 

40 

I 

I I 

60 

• Portland 

50 MILES 

I 

I 

80 KILOMETERS 

FIGURE 48.-Generalized pattern of ashfall thickness from the June 12 eruption of Mount St. 

Helens (modified from Sarna-Wojcicki and others, 1981). Although winds at the different altitudes reached by the ash were blowing in different directions, most of the ash 

was distributed to the southwest of the volcano. information on the extent of trace 

amounts of ash was not available. Lines of equal ash thickness are designated in 

millimeters (1 inch=25.4 mm). 

Chronology of the First 100 Days 93 
The National Weather Service, 

which has been monitoring the movement of the airborne ash, predicts that 

some of the ash carried out over the 

Pacific Ocean last night will be blown 

back over northern California by 

tonight. (The curved path of the ash 

cloud may account for reports that ash 

reached ~edford, near the southern 

border of Oregon.) 

Day-long rains in much of the ashfall 

area settled the ash and helped cleanup 

efforts, but the rain also formed slick 

mud that made driving hazardous. A 

speed limit of 15 miles an hour that was 

imposed in Portland during the ashfall 

was lifted by midmorning. The flashflood watch for the Toutle, Cowlitz, 

Kalama, and Lewis Rivers, which was 

imposed last night, also was cancelled. 

In the 8 hours following last night's 

eruption, many small "aftershocks" 

were recorded at the University of 

Washington seismology center. 

Twenty-one of these shocks were 

strong enough that preliminary locations could be calculated. These quakes 

originated at depths of about 4 to 7 

miles below the surface and were located just west of the volcano's crater. 

Bad weather and the fuming volcano 

prevented observation of the crater today, but radar imagery obtained at 

about 2:00 p.m. by the Oregon Army 

National Guard clearly shows that the 

amphitheater a-nd rampart are about 

the same as they were when last seen 

and that what appears to be a dome 

now is in the position of the former inner crater. 

Helicopter reconnaissance around 

the mountain today could not verify 

the presence of the dome, but observers could see that the eruption had 

caused extensive new pumice flows 

north of the volcano and also minor 

mudflows that ended on the mountain 

itself. The pumice flows had poured 

out of the open end of the amphitheater and rushed downslope to the 

north, completely burying the ash flow 

from the ~ay 25 eruption and filling 

steam-explosion craters that formed in 

the ~ay 18 debris-avalanche deposits 

(fig. 30). One lobe flowed nearly 5 

miles, stopping within 30 yards of 

Spirit Lake. Another extended westward more than 1 mile in the upper 

part of the North Fork Toutle River 

valley. USGS geologist Peter Rowley 

said that the material ejected in the 

eruption was from fresh magma rather 

than old rock or ash from the larger 

(~ay 18) crater. Like those from the 

~ay 25 eruptions, the latest pyroclastic deposits contain dense dark-gray 

pumice and vesicular tan pumice. The 

deposits also contain blocks of dense 

gray dacite rock. Temperatures measured in the June 12 ash flows are more 

than 1,100°F (600°C)-hotter than any 

measured in the ~ay 18 ash flows and 

nearly hot enough to melt aluminum. 

USGS volcanic hazards geologists 

today described the effects of the eruptions and the outlook for continued explosive activity to a U.S. Senate subcommittee hearing in Portland called 

by Oregon Senator Robert Packwood. 

By this evening, the volcano was still 

emitting steam but little or no ash. 

Saturday, June 14 

E Day Plus 27 

Although avalanches in the crater 

could be heard from the ground, the 

mountain itself was quiet today. All 

that could be seen was a small steam 

plume rising to an altitude of about 

15,000 feet. Poor visibility prevented 

viewing of the crater. Although the 

strength of the harmonic tremor continues to diminish, the University of 

Washington seismology center says 

that the mountain still is more 

seismically active than it was before 

the last eruption. 

Scientists began installing new 

tiltmeters near the cone, but they could 

not reach gravity-monitoring sites 

because of poor flying weather. 

Ground parties found that pyroclastic 

deposits from the eruption of Thursday 

and Friday were still very hot, coated 

with sulfur in places, and dotted with 

fresh pumice blocks. Temperature 

measurements made at a depth of 10 

94 The First 100 Days of Mount St. Helens 

feet in deposits filling . an old steamexplosion pit near the downslope end· 

of the pyroclastic flows registered nearly 1,100°F (600°C). 

Ash from the eruption of June 12 and 

13, collected dry in Vancouver, was 

soaked with distilled water, and the 

leachate was analyzed, as was that of 

the earlier ash. The chemical constituents of the leachate were about the 

same as those of the earlier ash, except 

that this leachate was more acidic (pH 

3.6-4.2). 

Designated State of Washington offices began reissuing permits today 

allowing residents to return to their 

homes in the Red Zone. 

Washington Department of Fisheries 

biologists say that salmon are 

"bleeding to death" in the ashy mud 

carried by the lower Cowlitz River; 

they doubt that fish will ever be able to 

adapt to river water made muddy by 

the ash. Dissection of the fish shows 

tiny, razor-sharp particles of silica 

lodged in their gills "cutting them to 

shreds." 

Agricultural experts, however, are 

now saying that ash damage to 

Washington's agriculture industry (fig. 

49) is less than originally estimated. 

Scientists from Federal and State 

FIGURE 49.- Effects of ash from the May 18 

eruption on agricultural areas in eastern 

Washington. A, Compacted ash 0.75 to 1 

inch thick smothered lentil plants in this 

field about 25 miles south of Spokane. 

The severe damage to this crop is obvious, but many crops in the "ash 

belt" produced profitable returns in 1980 

despite the ashfall. (Photograph by Earl 

Baker, U.S. Soil Conservation Service, 

July 1980.) B, Tractor towing a disc 

cultivator through a field at the Lind 

Agricultural Experiment Station, about 

12 miles southwest of Ritzville. As much 

of the ash as possible was mixed into the 

underlying soil in this manner. The thick 

cloud of ash dust raised by this rather 

gentle cultivation method shows why 

dust respirators were strongly recommended for agricultural workers in the 

"ash belt. " (Photograph by C. Kelley, 

U.S. Soil Conservation Service, summer 

1980.) 

FIGURE 50.-Aerial photographs of the lava dome that extruded into the crater of Mount St. 

Helens during the latter part of June 1980. The volcano's dacite lava has a pasty consistency when it is molten, and it tends to pile up rather than to flow laterally. This 

dome, which was largely destroyed in a subsequent eruption on July 22, 1980 (fig. 61B), 

was, at this stage, about 1,200 feet across and 200 feet high. Its rough, shattered appearance resulted mainly from the expansion and shattering of the solidified outer crust 

as more molten lava was forced upward by the great pressure in the magma chamber 

underlying the volcano. A, View through the amphitheater mouth from the northeast 

(direction of view same as that in fig. 46 but farther out). The lava extruded into a 

depression left by the June 12 explosive eruption. The curved ridge, or rampart, across 

the inner crater mouth is clearly visible in the middle of this photograph. At this time, 

fuming was strongest in the southern and eastern parts of the crater floor and inner 

crater walls and at places in the llmoat" around the base of the dome. Two cracks in the 

crater floor, radiating outward from the dome, are marked by rows of faint vertical 

vapor plumes (white streaks) at left center. (Photograph by Michael P. Doukas, USGS, 

June 28, 1980.) B, View from the west over the crater rim from a helicopter taking 

geologists to collect samples and measure temperatures inside the crater. The breadcrust texture of the dome's surface is well shown here. The white area inside the crater 

rim in the left foreground is sunlight reflecting from vapor and light-colored tephra . 

The tephra rampart is at the extreme left. (Photograph by Jules D. Friedman, USGS, 

June 29, 1980.) 

96 The First 100 Days of Mount St. Helens 

agricultural agencies today placed the 

total agricultural damage at between 

$175 and $186 million. Previous 

estimates were $200 million or more. 

Volcanic activity at Mount St. 

Helens has caused renewed concern 

about Mount Baker, the northernmost 

steaming volcano in Washington. The 

interagency "Mount Baker Information 

Committee, " formed in 1975 when that 

volcano heated up, has been reactivated. Recent flights over Mount 

Baker by USGS observers and others, 

however, have not yielded any indication of an increase in volcanic activity. 

Many "volcano watchers" in Vancouver are getting their first real taste 

of the aggravating personal effects of 

the persistent ash-effects that have 
been all too familiar to residents in the 

eastern Washington "ash belt." These 

include wearing dust masks whenever 

there is a need to go outside; careless 

drivers whose vehicles raise unnecessary dust clouds; the slipperiness 

of ash during a rain and the return of 

dust almost as soon as the rain stops; 

and the continual presence of ash on 

hair, clothing, furniture, and equipment. 

Lava Dome Grows 

Sunday, June 15 

E Day Plus 28 

Weather conditions today permitted 

detailed observations of the crater's interior for the first time since the latest 

eruptions, and the presence of the 

dome shown on radar images last Friday was confirmed visually (fig. 50). 

The dome was seen first this morning 

by observers in a Forest Service 

airplane and later from a helicopter at 

crater level. The dome is a symmetrical 

mass, circular in area, about 700 feet in 

diameter and rising 130 feet above the 

level of the crater floor. It is tan to light 

gray, and its surface is cracked into a 

pattern resembling large-scale breadcrust texture. A slight red glow 

emanates from within the hot dome 

through cracks in the crust of solidified 

lava. Almost its entire margin was 

fuming today, as was much of the 

crater floor near the steeper crater 

walls. Small steam explosions, concentrated mainly at the northeastern 

edge of the dome, were periodically 

spouting small amounts of gray ash up 

to heights of about 300 to 700 feet 

within the crat~r. A shallow moatlike 

depression lies between the dome and 

the rampart to the north. The dome is 

the cooling top of a column of magma 

rising from beneath the volcano. No 

flows or other obvious signs of rapid 

growth were seen today, however. 

The appearance of the dome doe::. 

not, scientists say, change the assessment of hazards from the volcano. 

Although the dome may represent a 

late, less highly explosive stage in this 

eruptive sequence, the flank of the 

volcano directly north of the breach in 

the crater (fig. 51) is still subject to 

small explosions, partly because of the 

crater's shape and partly because of the 

position of the new dome. Furthermore, the record of Mount St. Helens' 

previous eruptions shows many highly 

explosive eruptive sequences within 

long-term eruptive episodes. There is 

"life in the old girl yet," scientists point 

out, and highly explosive eruptions of 

both tephra and gas could reach into 

the stratosphere, and pyroclastic flows 

could speed down the volcano flanks 

into adjacent valleys. Although the 

dome may cap the present volcanic 

vent, it could be blown away by eruptions, or explosions from beneath 

Chronology of the First 100 Days 97 
98 The First 100 Days of Mount St. Helens 
FIGURE 51.-Aerial photograph of Mount 

St. Helens taken from about 7 miles to 

the north-northwest, looking over the 

site of the demolished Coldwater II 

observation post (marked by an X) and 

debris-avalanche deposits in the eastern 

part of the North Fork Toutle River 

valley. The location of the geologists 

shown in figure 47A is indicated by the 

vertical arrow (center foreground). 

(Photograph by Austin Post, USGS, June 

30, 1980.) 

could direct lateral blasts down the 

slopes at high speeds. 

University of Washington seismographs recorded vibrations caused 

when sections of the crater rim avalanched back into the crater; low-level 

harmonic tremor also was recorded, 

but there were no actual earthquakes. 

A few measurements of sulfur dioxide gas taken since the eruptions of 

Thursday night show that the emission 

rate has averaged about 1,000 tons a 

day during the initial growth of the 

dome. 

The most consistent of the Mount St. 

Helens tiltmeters, located about 3.5 

miles south-southwest of the volcano's 

center, stopped sending data today. 

That instrument, which had been 

operating during all three of the major 

eruptions, had indicated a nearly constant, though very small, inflation of 

the southern flank throughout May 

and early June but had shown little or 

no change in tilt beginning the second 

week of June . 

Warm, dry weather and light breezes 

combined to create zero-visibility conditions in some parts of northwestern 

Oregon that had received a substantial 

dusting of ash during last Thursday 

night's eruption. In the VancouverPortland metropolitan area, blowing 

ash also was causing problems. In 

Portland, a speed limit of 15 miles an 

hour was reimposed to reduce traffic 

hazards. Area residents spent much of 

their weekend hosing ash from cars, 

homes, sidewalks, and streets. Flushedoff ash clogging the filters of sewagetreatment plants necessitated dumping 

partly treated sewage into the Columbia River. 

Dust masks were a common sight on 

area residents and even on participants 

in the Portland Rose Festival, which 

ended today. The parade, a major 

event of the festival, took place yesterday despite ash-related problems. 

Three airlines temporarily suspended 

flights into Portland International Airport for fear that the ash would 

damage airplane engines. 

The Corps of Engineers reports that 

a second dredge has now begun working in the lower Cowlitz River channel 

to remove debris deposited by the 

flood of May 18 and 19. A third dredge 

is expected to move into the lower 

Cowlitz tomorrow. 

Monday, June 16 

E Day Plus 29 

It was a quiet day on the mountain; 

no harmonic tremor or significant 

earthquakes were recorded. Poor 

visibility prevented scientists from 

observing the height and size of the 

new dome. Mullineaux reminded news 

reporters that, although the dome 

represents the first lava to be seen during this year's eruptions, the building 

and destruction of lava domes have 

been repeated occurrences in the 

40,000-year history of Mount St. 

Helens. The previous summit was 

formed by a dome extruded 400 to 500 

years ago, and Goat Rocks was a dome 

formed in the mid-1800's (table 2). 

The Corps of Engineers reports that 

five dredges now have scooped out a 

narrow channel in the Columbia River 

shoal, off the mouth of the Cowlitz 

River, that will allow passage of ships 

having a maximum draft of 36 feet. 

The volcanic ash that powdered 

many forests may reduce the danger of 

forest fires in central and eastern 

Washington and northern Idaho this 

year, according to University of Idaho 

scientists. They say that the ash looks 

and acts just like some fire retardants 

now in use. They concede, however, 

that blowing ash could hinder firefighting efforts and also could reduce 

visibility from fire-lookout stations 

and thus allow small fires to grow 

before they are spotted. 

The Mount St. Helens Technical Information Network suggested ways to 

suppress the volcanic dust that has 

fallen so widely on the Northwest. One 

method is to mix the ash with 

agricultural lime and use the mixture as 

a cementing agent to form a windproof 

crust over ash dunes and other loose 

ash. A crust also could be formed by 

using lignin sulfonate (a byproduct of 

wood-pulp industry), asphalt components and emulsions, or soft asphalt 

itself. 

Tuesday, June 17 

E Day Plus 30 

Mount St. Helens has remained quiet 

since its eruption on June 12. Today 

was partially clear, but steam and gas 

continued to rise from the crater and 

formed clouds too dense to allow 

observation of the new dome. Shortly 

after 4:00 p.m., the volcano briefly 

ejected a plume of dense ash-the 

"most significant" since last week's 

eruption. The top of the dark plume 

leveled off at about 12,000 feet above 

sea level, and, because the air was still, 

most of the ash fell back into the 

crater. Seismographs recorded no 

significant local earthquakes and no 

harmonic tremor. 

Field crews remeasuring the deformation network on the mountain have 

found no appreciable change. A week 

ago, the southern side of the mountain 

was swelling slightly; now, it is stable. 

A light rain last night reduced the air 

pollution caused by persistent volcanic 

ash in the Portland-Vancouver 

metropolitan area. Most of the time 

since last Thursday night's eruption, 

both cities have been shrouded in a 

foglike cloud of ash dust that makes 

breathing uncomfortable and occasionally disrupts automobile and aircraft traffic. 

Autopsies have been performed on 

22 of the bodies so far recovered from 

the blast area. Sixteen deaths resulted 

from inhalation of hot ash, three from 

Chronology of the First 100 Days 99 
burns, and three from head injuries 

(two of these caused by falling trees). 

Two other people rescued as they were 

fleeing later died in the hospital from 

burn-related injuries. The death toll 

now stands at 24, and 45 are still officially missing. The Skamania County 

Coroner has been holding hearings 

about the last-known activities of persons still listed as missing. These hearings could result in the issuance of 

"presumptive death certificates" for 

some or all of the missing. 

Wednesday, June 18 

E Day Plus 31 

The mountain was quiet today. The 

University of Washington seismology 

center recorded one minor seismic 

event at 7:00a.m. that may have been 

caused by an avalanche in the crater or 

by cracking of the new dome's outer 

crust. Forest Service airborne 

observers said that the 7:00 a.m. 

seismic event was followed about 3 

minutes later by a burst of steam and 

ash that rose a few thousand feet above 

the crater before dissipating. An earthquake that was recorded at about 11:00 

a.m. registered as magnitude 2.8 and 

was located to the north of Mount St. 

Helens. About 5:30 p.m., the volcano 

again shot a plume of steam up to 

about 13,000 feet and then lapsed back 

to minor activity. 

The new dome has grown 60 feet in 

height since Sunday, or an average of 

about 20 feet a day. The height of the 

dome is difficult to estimate because 

the crater floor is irregular and largely 

obscured by steam. Another major 

eruption could destroy the dome entirely, or the dome could continue to 

grow, perhaps for decades. If the dome 

were to continue rising and if it were 

fluid enough, it could begin moving 

out to the north through the breach in 

the crater. If and when that were to 

happen, volcanologists say, the thick 

lava probably would flow downhill at 

a rate of no more than a few feet a 

day-a rate much slower than that of 

the more fluid basaltic lava flows from 

erupting Hawaiian volcanoes. 

The U.S. House of Representatives 

today passed a supplemental appropriations bill that includes more 

than $783 million for disaster relief 

programs in response to the Mount St. 

Helens eruptions. The funds will be 

used .to reimburse State and local 

governments for cleanup costs and to 

pay for dredging and debris removal, 

streambank restoration, construction 

of sediment-retention dams, restoration of farmlands, loans to businesses 

that suffered economic loss, and continuation of scientific study and 

monitoring of the volcano. 

USGS scientists Moto Sato and Ken 

McGee installed a hydrogen gas sensor 

today on the southern flank of Mount 

St. Helens at an altitude of 7,000 feet. 

The instrument will continuously 

monitor the hydrogen emissions from a 

cool crack (not a steaming fumarole) in 

a prehistoric lava flow; the data will be 

transmitted by radio to Vancouver. 

This information and other data being 

gathered about gas emanations from 

the volcano should lead to a better 

understanding of the volcano's internal 

processes. 

Oregon Governor Victor Atiyeh 

asked President Carter to declare 

Oregon a major disaster area. The 

Governor also called up 100 National 

Guard troops to help clean up the 

volcanic ash in Portland this coming 

weekend. 

Local newspapers report that a man 

with a gun commandeered a Portland 

city bus for a trip 30 miles east into the 

Columbia River Gorge after telling the 

driver, "I want to get out of town-out 

of all this ash." The hijacker ordered 

the driver to stop and fled on foot after 

an Oregon State Police car began following the bus. 

A meeting with officials of the 

Washington Department of Emergency 

Services was held in Kelso to present 

arguments for moving the Red Zone 

boundary 12 miles closer to the 

volcano. Mullineaux said that the basic 

issue was not that of being "safe" at 

some specific distance from the volcano but rather "the difficult decision 

of what is an acceptable risk." 

100 The First 100 Days of Mount St. Helens 

An early warning system is planned 

to alert those who might be endangered 

by floods during the coming winter. 

Floods may be worse than usual this 

year because waterways already 

clogged with sediment and debris will 

be filled further when more sediment 

washes downstream from the blast 

area. Although the Corps of Engineers 

has been dredging and today brought 

in a fourth dredge to speed sediment removal from the lower Cowlitz River, 

how much of the clogged channel can 

be opened up before the next flood is 

not known. In order to monitor flood 

threats more closely, 22 new river 

gages will be installed; the Corps of 

Engineers plans to install 8, the USGS 

2, and the National Weather Service 

12. The Weather Service also plans to 

install nine new precipitation gages 

linked by radio to emergency-services 

centers. 

USGS hydrologists completed detailed surveys of the Cowlitz and Toutle Rivers and computed a second set of 

floodwater profiles for several 

postulated conditions of runoff from 

rainfall and snowmelt. These data were 

sent to the Federal Emergency Management Agency. They showed that, if no 

changes are made in the choked channels, Castle Rock could be flooded this 

year by runoff from precipitation that 

is no greater than normal. If the channels are not opened up and the winter 

brings an extended period of moderate 

rainfall, the result could be a recordbreaking flood at Castle Rock, as well 

as severe flooding on the Cowlitz in the 

area of Kelso and Longview. 

The missing-persons list was reduced 

to 44 today when a Seattle man called 

authorities to report that he is alive and 

well. 

Thursday, June 19 

E Day Plus 32 

The weather today was clear enough 

for good viewing of the crater and for 

aerial photography. Photographs to be 

used in mapmaking were obtained by 

the National Aeronautics and Space 
Administration and by a contractor for 

the Washington Department of 

Natural Resources. 

Mount St. Helens was inactive today, except for steaming inside the 

crater. The dome has grown another 6 

to 10 feet since yesterday, and its top 

now stands about 200 feet above the 

crater floor. 

Thermal infrared surveys of the 

volcano were made from U.S. Navy 

and Oregon Army National Guard aircraft. These surveys reveal a circular 

pattern of fumaroles on the crater floor 

southeast of the dome and about the 

same size as the dome. Some scientists 

speculate that the circular area may be 

a forerunner of a second lava dome or 

of a new lobe on the present one. 

A new instrument station was 

established this morning on the high 

point of a ridge about 5 miles north of 

the crater floor (fig. 52). The ridgetop 

provides a good view directly into the 

crater, and several distinctive features 

of the dome top can be tracked from 

there with a theodolite (telescopic 

surveying instrument). The station is 

FIGURE 52.-A scientist aims a laser beam at 

one of several reflecting targets on steaming Mount St. Helens to measure precisely any change in distance that might indicate swelling of the mountain or provide other clues to the likelihood of an 

eruption (see fig. 3). This instrument site 

is about 5 miles north of the crater floor 

on a ridge informally called "Harry's 

Ridge" because it overlooks the former 

location of Mount St. Helens Lodge (out 

of view to the left), where proprietor 

Harry Truman presumably died during 

the May 18 eruption. (USGS photograph.) 

Chronology of the First 100 Days 101 
informally known as "Harry's Ridge" 

because it overlooks the now-buried 

site of Mount St. Helens Lodge, where 

proprietor Harry Truman presumably 

was killed during the May 18 eruption. 

Use at this station of other instrument~..~ 

including a remote-controlled television camera, is planned. 

Friday, June 20 

E Day Plus 33 

No sizable steam or ash plumes 

were seen today. No seismic events 

were recorded, other than those that 

could be attributed to avalanches 

down the inner slopes of the crater. 

Cloudy weather prevented measurements of the dome. Last night, 

however, observers again saw the 

glowing red cracks in the lava dome, as 

they have for the past few nights. 

Clement Shearer, USGS hazards 

geologist, said that there is no way to 

know whether the dome will eventually build up to become the mountain's 

new top, as at least one volcanic dome 

became in the past (table 2), or whether 

this dome will be blasted out in a new 

series of eruptions. 

University of Washington geologist 

Anthony Irving believes that the 

growth of the dome is "probably the 

best thing that could happen" because, 

as long as the lava oozes out, the 

pressure in the magma chamber 

beneath Mount St. Helens is unlikely 

to build up to an explosive eruption. If 

the growth stops "for a period of 

weeks," he says, the danger of an explosion will increase. 

The Washington Department of 

Emergency Services announced that it 

has decided not to decrease the size of 

the Red Zone (fig. 13), as had been requested last Wednesday. 

Several streams that formerly flowed 

into the upper (eastern) part of the· 

North Fork Toutle River were blocked 

near their mouths when the May 18 

avalanche sent debris into that part of 

the river valley. These tributary 

streams include Coldwater, South 

~oldwater, and Castle Creeks (fig. 7), 

Studebaker Creek (fig. 5), and a few 

smaller streams. Ponds have formed 

behind dams of avalanche debris, and 

water levels generally have been rising 

since May 18 as the streams continue to 

flow into these ponds (fig. 45). Some of 

the ponds, which already contain large 

volumes of water, might continue to 

grow until they overtop or break 

through the debris dams. The consequent outflows could increase in 

volume as they incorporate the easily 

erodible debris, and a major mudflow 

coursing down the channel of the 

North Fork Toutle River and further 

damaging downstream areas might 

result. Geologists are assessing the 

stability of the debris dams, while 

hydrologists are calculating how much 

water is in the ponds and watching the 

rates of water-level rise to determine 

whether and when steps should be 

taken to drain the ponds artificially. 

Saturday, June 21 

E Day Plus 34 

The volcano is very quiet. When the 

dome was measured last on Thursday, 

it was growing at a rate of about 6 to 

10 feet a day, and so the crater area still 

must be considered unstable and dangerous. Clouds and plumes of steam 

that rose to an altitude of about 11,000 

feet obscured the view into the crater. 

Seismometers on the mountain's flanks 

were jiggled today but only by avalanches of rock crashing down the inner wall~ of the crater. 

About 180 National Guardsmen 

used shovels and powered streetcleaning equipment today in Portland 

to assist in cleaning up ash from the 

June 12 eruption. About 235 of an 

estimated 350 miles of main streets 

already had been cleaned before the 

Guardsmen started. Air quality 

generally improved throughout the 

city. The Oregon Department of Environmental Quality suspended an airpollution warning for the Portland 

metropolitan area, but it kept in effect 

the warning for Tillamook County on 

the coast. 

102 The First 100 Days of Mount St. Helens 

The mayor of Ritzville, a farming 

community of less than 2,000 people 

that received more than 3 inches of ash 

on May 18, said that conditions are far 

from normal now, more than a month 

after the ashfall. The ash is still very 

troublesome, despite valiant cleanup 

efforts by local residents and National 

Guard troops. The town is surrounded 

by flat to gently rolling farmland, and, 

when the frequent winds blow, the ash 

cannot be prevented from "redistributing itself." The mayor added that, 

although about 65 percent of the ash in 

town has been cleaned up, it is the 

other 35 percent that is causing much 

of the problem. 

Sunday, June 22 

E Day Plus 35 

Mount St. Helens has spent a quiet 

weekend. No earthqu~ke or harmonic 

tremor was recorded, but there were 

minor seismic jiggles, probably caused 

by avalanches. Persistent clouds of 

steam and fumes continue to rise above 

the crater to altitudes as high as 14,000 

feet. Although the dome could be 

glimpsed within the crater, visibility 

was too poor to permit measurements 

of its growth. 

The scientific team continues to 

work hard to learn as much as possible 

about Mount St. Helens and, consequently, about this type of volcano in 

general. The main thrust of the work 

so far has been hazard evaluation; in 

this effort, many team members have 

been voluntarily working 16 to 18 

hours a day. Geologist Rowley says 

that they really believe that they will 

learn enough from Mount St. Helens to 

help save many lives during future 

eruptions of other volcanoes. The 

USGS crew at Vancouyer numbers 

about 20 to 25 at any given time, but 

many more can be recruited, if needed, 

from other USGS installations. At the 

pace now being maintained, "people 

get 'burned out,' " Rowley said, "and 

we bring others in." 

The official casualty count-24 dead 

and 44 missing-presumably will 
change tomorrow. A geologist riding 

in a Forest Service helicopter today 

spotted another body, which will be 

recovered tomorrow, if possible. 

Monday, June 23 

E Day Plus 36 

This morning, a steam plume rose 

briefly-first to about 13,500 feet and 

then to only 11,000 feet-before 

dissipating. Otherwise, neither eruptive nor seismic activity was recorded 

on the mountain. Most of the day, the 

mountain again was shrouded in 

clouds, and scientists could not see into 

the crater to observe the dome. 

USGS scientist Joseph Rosenbaum 

has reported on some of the details of 

the lateral blast-the great northdirected "wind" caused by the sudden 

release of gases that had been held 

within the magma. Blast damage was 

caused, he believes, not by a shock 

wave or by an ultrahigh-speed wind 

but by a hurricane-speed wind heavily 

laden with debris. Such a particleladen wind that could "sandblast" 

everything in its path would explain 

the pattern of destruction, according to 

Rosenbaum. Trees, stumps, and even 

soil were removed from exposed ridges 

nearest the mountain; only bare rock 

was left. Farther from the volcano, 

trees were snapped off at the ground, 

and bark was cleanly removed from 

trunks. A normal wind would have 

had to reach speeds of 150 to 200 miles 

an hour to destroy the trees in that 

manner. If the density of the "wind 

cloud" were increased by suspended 

rock particles, however, a wind moving at lesser speeds could achieve the 

same results. Investigations in the 

devastated area give ample proof that 

the blast wind was carrying pulverized 

rock (stones up to 4 inches across carried at least 8 feet off the ground) as 

well as other debris picked up in its 

outward rush. 

The Forest Service is asking Congress for additional funds to pay for 

monitoring smoldering timber debris 

under the ash and blast deposits on 

and near Mount St. Helens. Several 

hundred fires caused by lightning and 

hot ejecta from the May 18 eruption 

still burn beneath the ash. The ash is 

acting as a fire retardant, but Forest 

Service officials expect that, when it 

dries and the wind blows it away, 

flames and sparks could spread fires to 

neighboring timber stands. 

Governor Ray announced today that 

tourism in Washington so far this year 

is only about half the amount expected, largely because of adverse 

publicity about ash dangers. 

Financial institutions across the 

country apparently are wary of investing in some Pacific Northwest 

bond issues because of disruptive effects and economic risks attributed to 

the ashfall from Mount St. Helens. A 

San Francisco bank official estimates 

that this perceived increase in financial 

risk could drive up interest rates for 

borrowers such as school districts and 

city or county governments in affected 

areas. 

The body sighted yesterday was 

recovered by a helicopter team today 

and identified by Lewis County officials. The official number of dead is 

now 25; 43 are still missing. 

Tuesday, June 24 

E Day Plus 37 

The crater remained obscured by 

clouds all day, and light snow began 

falling on the mountain tonight. The 

volcano emitted only occasional bursts 

of steam that rose above the clouds. 

Tonight, two episodes of harmonic 

tremor were recorded-the first since 

June 15. The tremor was very weak, 

and it was detected only by the 

seismometer nearest the mountain. 

USGS glaciologist Melinda Brugman 

reports that about 70 percent, or 170 

million cubic yards, of Mount St. 

Helens' glacial ice mass was lost during 

the May 18 eruption. All of Leschi and 

Loowit Glaciers, most of Wishbone 

Glacier, and the upper parts of Forsyth, Nelson, Ape, and Shoestring 

Glaciers (fig. 5) disintegrated on May 

18. Toutle and Talus Glaciers now appear to be significantly thinner than 

they were before; large amounts of 

snow were removed from the surfaces 

of these two glaciers and Shoestring 

Glacier by both the heat of tephra and 

scouring. Only Swift and Dryer 

Glaciers appear largely unchanged. 

Surprisingly, the melting rate of the 

surviving glaciers at their surfaces of 

contact with the mountain's rock 

flanks does not seem to have increased. 

Increased melting probably would 

cause accelerated downslope ice movement and (or) increased flows in 

streams still draining Mount St. 

Helens'· glaciers, but neither effect has 

been seen so far. 

A controversy has developed between people who think that the timber 

downed by the May 18 blast should be 

left as a testament to the awesome 

force of the volcano and those who 

believe that the timber should be 

salvaged. Foresters point out that 

downed ash-coated timber is likely to 

be a threat to nearby healthy forests 

because it increases the risk of fire, tree 

disease, and insect infestation. Private 

timber companies plan to begin removing all salvageable trees from their 

lands soon. Forest Service official Norman Anderson said that it probably 

will take several months to work out 

plans for salvaging downed timber on 

national forest lands without jeopardizing adequate scientific study of the 

eruption aftermath. Some areas of 

blown-down forest probably will be 

left for public exhibit. 

Wednesday, June 25 

E Day Plus 38 

The volcano continued to expel 

plumes of steam, which occasionally 

contained light ash, several thousand 

feet above the crater rim. The ash barely tinged the white of last night's snow 

on the upper part of the mountain. 

Seismic activity increased again today; two small earthquakes (magnitudes 2 and 2.5) occurred, as did more 

harmonic tremor. The University of 

Washington seismology center reports 

that this morning's earthquakes were 

centered about 7 miles southeast of 

Chronology of the First 100 Days 103 
Mount St. Helens. The quakes were 

not of volcanic origin but were perhaps 

the result of a crustal adjustment to recent volcanic and seismic activity at 

Mount St. Helens. Soon after the 

earthquakes were recorded, "sustained 

harmonic tremor" began. 

Scientists cannot tell how the latest 

harmonic tremor may relate to conditions in the volcano's crater because 

poor weather and dense clouds of 

steam and fumes have prevented observations of the crater floor and dome 

for the past several days. 

Thursday, June 26 

E Day Plus 39 

Harmonic tremor occurred early this 

morning (3:30 a.m.) but ended about 

9:00 a.m. No earthquakes were recorded, and no unusual eruption 

plumes were seen. 

Airborne observers got a brief look 

at the dome inside the crater, but they 

were unable to see well enough to 

judge whether the dome has grown 

during the past week. 

Forest Service biologist William 

Ruediger reports finding some encouraging signs of wildlife in the generally 

bleak areas covered by Mount St. 

Helens ash. Eggshells from hatched 

eggs have been discovered, an indication that some birds stayed with their 

eggs during the ashfall. Native rainbow 

trout also have been found "surviving 

remarkably well." Conversely, cutthroat trout appear thin, sick, and less 

likely to survive. 

In Japan, according to the Associated Press, geophysicist Motokazu 

Hirono reportedly has measured microscopic particles, which he ascribes 

to ash from the May 18 eruption of 

Mount St. Helens, at an altitude of 

about 11 miles in concentrations that 

might block sunlight and lower the 

Earth's temperature. Hirono cites the 

example of the stratospheric ash band 

from the 1883 eruption of Mount 

Krakatoa in Indonesia (see fig. 62), 

which caused record low temperatures 

and severe crop damage in Japan and 

elsewhere the following year. Scientists 

from the National Weather Service and 

the University of Washington, however, dispute Hirono's evidence for that 

much Mount St. Helens ash in the 

stratosphere and, especially, his comparison to the Indonesian eruption. 

Krakatoa blew a volume of ash into the 

stratosphere much larger than the entire mass of material blown out of 

Mount St. Helens so far this year. 

"Comparing Krakatoa to [Mount] St. 

Helens is like an elephant versus a 

gnat," says one scientist. 

Friday, June 27 

E Day Plus 40 

The 100th day of activity at Mount 

St. Helens showed evidence that 

magma is still moving beneath the 

volcano. Harmonic tremor, which 

preceded the last two major eruptions, 

was recorded again today. Seismologists at the University of Washington 

said that, although today's harmonic 

tremor was the strongest since June 12, 

it had only about one-fourth the amplitude of the tremor preceding the June 

12 eruption . Seismologists also 

reported a small (magnitude 2-2.5) 

earthquake that seemed to be centered 

about 7 miles north of the volcano. 

The volcano continued to vent steam 

to an altitude of 11,000 feet today, but 

airborne observers were able to see into the yawning crater and reported that 

the dome of solidified lava looks no 

larger than it did when it was seen last. 

It was previously measured from photographs as about 1,200 feet across and 

200 feet high. 

USGS geologist Tim Hait said that, 

if the dome has really stopped growing, gases may be building up in the 

volcano. He repeated earlier warnings 

that the volcano could still explode 

without warning into further large 

eruptions of ash, along with pyro104 The First 100 Days of Mount St. Helens 

clastic flows of superheated gas and 

shattered rock. "It still is a mighty 

dangerous area," Hait said. 

Water from the pond on Castle 

Creek (fig. 45), which was dammed by 

avalanche debris, has emerged from 

the debris deposits about 1 mile 

downstream from the pond after apparently seeping out along its buried 

channel deposits. The outflow is 

eroding a new creek channel through 

the valley-fill deposits. The debris dam, 

which contains timber debris as well as 

rock material, probably will not be 

undermined by outflow at the rate seen 

today. The water now is flowing into 

the next pond downstream, however, 

and may increase the danger of an outburst from that smaller pond. 

The Corps of Engineers is moving a 

large dredge farther upstream (to river 

mile 6.3) in the Cowlitz River, which is 

still clogged by millions of cubic yards 

of volcanic flood debris. The dredge is 

intended to help clear a channel 25 

miles long in the lower Cowlitz for 

flood passage and navigation. The 

dredge was moved from the mouth of 

the Cowlitz River, where it had been at 

work since June 10. 

FIGURE 53.-Views of Mount St. Helens and 

Spirit Lake from the north-northeast 

before (top) and after (bottom) the eruptions of May and June 1980. The dashed 

outline in the bottom view shows how 

much of the original volcano cone was 

lost during the early part of the May 18 

eruption. Spirit Lake (bottom view) now 

is more extensive and shallower, and its 

shoreline is about 200 feet higher than it 

was formerly. The lake now is choked 

with thousands of logs blown into it by 

the initial blast. (Paintings by Dee 

Molenaar, USGS.) 
AT THE END OF THE FIRST 100 DAYS 

Summary of 

Conditions 

At the end of its first 100 days of 

1980 activity, which began with the 

sudden earthquakes of March 20, 

Mount St. Helens is quiet, but it cannot 

be considered stable or safe. 

A 

Mount St. Helens has been called "a 

volcano in a hurry. " In 11 weeks 

(March 27-June 13), the volcano has 

had three major eruptions of ash and 

pumice and related pyroclastic flows, 

as well as countless smaller eruptions 

involving only ash, steam, and other 

fumes. It has lost an estimated 3.4 

billion cubic yards (0.63 cubic mile) of 

its cone (fig. 53) and has pulverized 

about 400 million cubic yards (0.07 

cubic mile) of new magma; it has scattered volcanic ash and pumice over 

much of the Northwest and has begun 

to build a new dome inside its new 

crater. Volcanologists say that many 

volcanoes of this type require months 

or even years to complete these steps. 
FIGURE 54. -Aerial view of Mount St. Helens from the southeast showing extensive 

mudflows on the eastern flanks. The larger mudflows originated from or near Shoestring Glacier, which now heads at the deeper notch in the crater rim. Many smaller 

mudflows cover the upper slopes on all sides of the mountain, but the dark areas seen 

here on the upper slopes are mostly ash that had been wetted by underlying snow or 

ice. The major streams shown here are the Muddy River, which leaves the photograph 

at the lower right, and Pine Creek, which leaves at bottom center. The pattern on the 

land to the left of Pine Creek is the result of logging before the eruptions. The haze in 

the picture is mainly from windborne volcanic ash, which is present near the volcano 

most of the time. (Photograph by Ralph Keuler, USGS, July 1, 1980.) 

Above the timberline (on the sides of 

the volcano where timber still 

survives), the stubbed-off cone is ash 

gray streaked with brown from countless mudflows (fig. 54). Snow and ice 

remain on the upper slopes beneath the 

insulating blanket of ash but can be 

seen from the air only where the 

melt water has darkened the overlying 

ash or where steep ice faces have shed 

the ash. Many mudflows reach downslope into dusty timber, and the larger 

flows extend down the courses of 

preeruption streams. Tongues of 

mudflow deposits have killed some of 

the standing conifer trees and turned 

them brown. 

Observations of the volcano, as well 

as general visibility in the area are 

often hampered by cloudy weather, by 

haze caused by blowing ash, and by 

smoke from hundreds of fires. These 

fires, which originally were started by 

lightning and hot pyroclastic material 

during the May 18 eruption, still 

smolder beneath the volcanic deposits. 

The fumaroles in the vicinity of Spirit 

Lake and the upper valley of the North 

Fork Toutle River that formerly were 

so effuse have dwindled greatly in their 

output. 

The cratered cone yawns open to the 

north. The rampart on the northern 

side of the inner crater at its lowest 

point is now at an altitude of about 

6, 150, about 2,200 feet lower than the 

highest part (8,364 feet) of the sharp, 

jagged crater rim on the southwestern 

side. A broad ramp of avalanche debris 

and older rocks, somewhat smoothed 

by a mantle of pyroclastic deposits, 

descends northward from the rampart 

into the valley of the North Fork Toutle River and to the southern shore of 

the raised Spirit Lake (fig. 55). Avalanches frequently bring showers of 

rock and some blocks of glacier ice left 

at the crater rim down the inside crater 

106 The First 100 Days of Mount St. Helens 

walls. The horseshoe-shaped crater, 

which stretches about 7,000 feet (1.33 

miles) from rim to rim in an east-west 

line, tapers to about half that width at 

its irregular inner floor, which, in 

places, is lower than the northside rampart by about 100 fee.t. North of the 

center of the inner crater floor is the 

roughly circular dome of gray, broken 

lava rock, surrounded by a "moat." 

Steam rises from the margin of the 

dome, but most of the steam now 

emanating from the volcano comes 

from a concentration of vents along the 

southern, or closed, part of the crater 

floor and the lower crater walls. During most of the period from June 15 to 

June 27, there was no running or standing water on the crater walls and floor; 

by June 28, however, a small pond had 

formed in the southwestern part of the 

crater floor. 

The profile of the lava dome remains 

much as it was when it was fir.st seen 

on June 19. The dome grew rapidly the 

first few days after its appearance, but 

its growth now seems to have slowed 

or stopped. No one knows what the 

final size of the dome will be (it is now 

roughly 24 acres in area) or what the 

volcano will do next. (This dome was 

almost completely blown away by an 

explosive eruption on July 22, 1980, 

which is shown in progress in figure 

61B. Thereafter, dome building resumed.) USGS and State of Washington mapmakers are hoping that 

there will be no major changes in the 

FIGURE 55.-Views from Mount St. Helens 

northeastward across Spirit Lake toward 

Mount Rainier before (top) and after 

(bottom) the eruptions of May and June 

1980. Decades may pass before the barren ridges and log-choked Spirit Lake 

return to something like their former 

beauty. However, the coating of ash on 

Mount Rainier(bottom, background) was 

soon hidden beneath fresh snow. (Paintings by Dee Molenaar, USGS.) 

landscape for a while, since they are 

busy preparing maps of the "new" 

Mount St. Helens and vicinity. 

Sulfur dioxide emissions from the 

volcano were about the same at the end 

of June as they had been since midmonth-that is, about 1,200 tons a 

day. The presence of this gas proves 

that the volcanic fumes are corning 

from an underground source that remains very hot, and the rapid rate of 

emission makes Mount St. Helens the 

greatest point source of so2 air pollution in the Pacific Northwest. 

The size of the area devastated by 

the May 18 lateral blast and the scale of 

the changes wrought by the eruption 

are often difficult to comprehend, 

especially from the air (fig. 56). Only 

when the v_iew includes a familiar object such as a low-flying aircraft or 

when the observer is reminded that the 

tumbled mass of "matchsticks" may 

consist of trees 80 to 100 feet long does 

the immensity of the disaster become 

apparent. 

On the ground, there is heartening 

evidence of the resurgence of vegetation and wildlife. A few green plants 

are emerging from the ash and blast 

deposits (fig. 57), and deer and other 

animals have been seen in the blast 

area. The restorative part of the cycle, 

repeated many times before at this 

volcano and others in the Cascade 

Range, has begun once more. 

The Red Zone is still closed. Its 

boundary, established on June 2, remains at a distance of about 17 to 27 

miles from the mountain (fig. 13). The 

Blue Zone boundary extends beyond 

that of the Red Zone to the east, south, 

and north. Individual entry into the 

Red Zone is by permit only; the only 

human activities legally allowed are 

logging, scientific studies, law enforcement, firefighting, and searching for 

those still missing and presumed dead. 

State officials are receiving requests to 

decrease the size of the restricted zone, 

despite the facts that the three major 

eruptions have spewed out hot pyroclastic flows and that no one can be 

sure if there are more eruptions to 

come. 

Salvage of about a billion board-feet 

of blasted-down timber has begun 

slowly. Work is greatly hampered by a 

lack of access roads and even pathways 

between the large, tumbled trees and 

by the blinding, choking ash that rises 

in clouds at each disturbance. The ash 

affects machinery, as expected, by increasing wear and necessitating frequent maintenance. To humans working in ash areas, however, the ash is 

FIGURE 56.-Aerial view of Mount St. 

Helens across the devastated area from 

about 13 miles to the north-northwest. 

The viewpoint is well within the area of 

blown-down trees. Elk Lake (lower 

center) and the quarter-mile-long 

Hanaford Lake (center) are among about 

30 small lakes and ponds, formerly 

jewellike in forested settings, that were 

turned brown and desolate by blast and 

ashfall in a few minutes. Coldwater II 

observation station, where David 

Johnston was on duty at the time of the 

May 18 blast, is at right center. 

(Photograph by Austii1 Post, USGS, June 

30, 1980.) 
FIGURE 57.-Life returns to the vicinity of 

Mount St. Helens. A, Ferns and other 

small plants pushed up through a blanket 

of ash 4 inches thick on the southern 

flank, 3 weeks after the May 18 eruption. 

(Photograph by J. R. Stroh, U.S. Soil 

Conservation Service .) B, Avalanche 

lilies (Erythronium montanum) growing 

through blast deposits from the May 18 

eruption, about 10 miles northwest of the 

volcano. (Photograph by Joseph G. 

Rosenbaum, USGS, June 8, 1980.) 

At the End of the First 100 Days 109 
proving to be even more troublesome. 

Some dust masks and respirators that 

are effective in filtering out the ash are 

unpleasant to wear and make strenuous labor difficult. Other masks leak, 

and some respirator filters are difficult 

to keep clean. 

In the eastern part of the North Fork 

Toutle River valley, the debris avalanche has left a hummocky deposit 

(estimated volume, two-thirds of a 

cubic mile) that extends about 14 miles 

westward down the valley from the 

avalanche source on the flank of the 

volcano (fig. 47). The former valley 

floor is buried under more than 600 

feet of avalanche debris directly north 

of the crater, but the debris deposit 

thins gradually in the downvalley 

direction. Farther west in the valley of 

the North Fork and also in the valley of 

the South Fork Toutle River, the 

former valley floors were buried by extensive but thinner mudflow deposits 

(fig. 31). 

The valley of the main Toutle River, 

which is a scene of mud-plastered tree 

trunks, shattered buildings, missing bridges, and barren mudflow 

deposits, is slowly beginning to recover 

(fig. 58). The rebuilding of damaged or 

destroyed homes (fig. 32) has been 

110 The First 100 Days of Mount St. Helens 

slowed by the destruction of many access roads and driveways, by the 

widespread loss of income among loggers, farmers, and merchants, and by 

the threat of future floods. 

Even the valleys of the North and 

South Forks of the Toutle River are 

coming back to life. At logging camps 

in both valleys, the chaos caused by 

the May 18 floods is beginning to be 

overcome. The tangled masses of logs 

and machinery are gone, and the logs 

have been restacked in neat storage 

piles. Logging trucks are moving along 

some roads again, trailing clouds of 

ash behind them. 
B 

FIGURE 58. -Effects of the Mount St. Helens eruptions in the upper valley of the South Fork 

Toutle River. A, Aerial photograph of mudflow deposits on the valley floor, looking 

east toward steaming Mount St. Helens and Mount Adams, in the distance. 

(Photograph by Austin Post, USGS, June 30, 1980.) B, A tongue of the hot lateral 

blast, which generally went to the north and east of this area, jumped across the ridge 

from the valley of the North Fork Toutle River and left an area of blown-down and 

scorched trees in the valley of the South Fork. The view here is to the northeast, at the 

point marked by the arrow in A. (Photograph by Edwin McGavock, USGS, May 20, 

1980.) 

The channels of Pine Creek, Muddy 

River, the Toutle River system, and the 

lower Cowlitz River are still largely 

choked with sediment and debris. Near 

the volcano, the streams are eroding 

new courses through the avalanche and 

mudflow deposits (fig. 59). Farther 

downstream, most original stream 

channels have been reoccupied by 

postflood streams, but they are obviously very shallow. Where former 

streams were deep and clear, many 

bars and shallows show through the 

muddy brown water. These channels 

probably will not enlarge much naturally before the period of increased 

runoff begins next autumn during the 

wet season. 

Travelers along Interstate Highway 

5 can easily see the effects of flooding 

at the bridge across the Toutle River 

and southward beyond Castle Rock. 

Most trees standing near the highway 

seem to have survived the flooding. 

Some leafy trees, however, are changing to their dormant coloring, giving 

the impression of an early autumn. 

Farther downstream on the Cowlitz 

River, the Corps of Engineers is 

operating dredges to restore as much of 

the channel capacity as possible before 

the next wet-season floods begin (fig. 

60). Off the mouth of the Cowlitz, 

dredging has restored the depth, if not 

the full width, of the Columbia River 

ship channel. As the dredges operate, 

areas of brown dredge spoil grow daily 

along the Cowlitz riverbanks and on 

the Columbia channel islands. 

In the "ash belt" of eastern 

Washington, light-gray volcanic ash 

still borders the highways and blankets 

many uncultivated areas. Where the 

At the End of the First 100 Days 111 
ashfall was thick, workers in the fields 

(fig. 49) face the same kinds of problems with breathing protection and 

machinery wear and maintenance as 

the loggers near Mount St. Helens. The 

ash rises into the air at the slightest 

disturbance, unless it is wet. Fortunately, rainfall in the main ashfall areas 

during June 1980 was unusually frequent and abundant (20 to 25 percent 

greater than normal) and greatly 

alleviated the dust problem in the 

region. Ash is still being removed from 

highways in eastern Washington, and 

motorists may experience some delay 

during the upcoming Independence 

Day holiday. 

Some insect populations in eastern 

Washington have been badly depleted 

by the ash, and other competing 

species have flourished as a result 

Many crops have suffered at least some 

damage, even if it is only stunted 

growth because the ash on leaves 

retarded photosynthesis this spring. 

Crops that still bear the persistent 

coating of fine ash bring lower prices 

on commodity markets. 

In southwestern Washington and 

northwestern Oregon, evidence of the 

ash also persists, even in the cities of 

Portland and Vancouver, which received relatively light ashfalls and 

where cleanup efforts were extensive. 

However, by this time, little ash remains in the air, and deposits on 

buildings and streets are becoming less 

apparent. 

Spokesmen for the tourist industry 

in Oregon and Washington are warning of dire impacts on that industry, 

which ranks third largest in both 

States. Ripple effects could be felt 

throughout local commercial struc112 The First 100 Days of Mount St. Helens 

tures unless the Northwest can manage 

to shed the "image of a hazardous 

volcanic disaster" and turn Mount St. 

Helens from a liability into a tourist attraction. 

Economic losses in the State of 

Washington have been estimated officially at $860 million, down substantially from earlier estimates. The 

largest loss, reported to be $450 

million, was standing timber in areas 

affected by the lateral blast and 

mudflows. Losses in agricultural output, which apparently are less than officials had expected, may range from 

$40 to $100 million. Except for losses in 

areas near the volcano, most economic 

damages were caused by ashfall. 

Notable exceptions are the flood 

damage along the Toutle and lower 

Cowlitz Rivers, the costs of dredging 

and levee building, and economic 

losses related to interrupted shipping 
& 

~FIGURE 59.-Debris from the May 18 eruption in the valley of the North Fork Toutle River. 

A, View eastward up the debris-choked valley toward steaming Mount St. Helens (the 

edge of the crater mouth is barely visible). This area is near the southern fringe of the 

blast zone. (Photograph by Austin Post, USGS, June 30, 1980.) B, Stream eroding a 

new channel in avalanche and mudflow deposits in the valley of the North Fork Toutle 

River. This kind of erosion will go on for years, or even decades, until the stream network reestablishes itself into a new, stable system. (Photograph by Edwin McGavock, 

USGS, June 23, 1980.) 

FIGURE 60.-0ne of several dredges that ~ 

were clearing mudflow debris from the 

dangerously filled channel of the Cowlitz 

River during the summer of 1980. The 

floating pipeline carries dredge spoil 

(mud) to the dumping ground on the 

river flood plain. (Photograph copyright 

1980 by Bud Kimball.) 
on the Columbia River. The economic 

impacts on communities in the "ash 

belt" varied greatly, but, as a general 

rule, the greater the ashfall thickness, 

the greater the economic loss. 

Oregon also has suffered economic 

losses, mostly because of ash effects 

and cleanup costs. A notable 

agricultural loss in northwestern 

Oregon (and also in southwestern 

Washington) occurred after the ashfall 

of June 12 and 13. Much of the 

strawberry crop rotted in the fields 

when ash-laden leaves pressed the fruit 

against the soil. Other losses to berry 

crops occurred because ash could not 

be washed from the fruit. 

Most economic loss in the PortlandVancouver metropolitan area has been 

related to ash cleanup, but a major loss 

also has resulted from the disruption of 

shipping on the lower Columbia River. 

For example, the Port of Portland 

reportedly expects to lose at least $5 

million in revenues through the month 

of August 1980 because of closure of 

the Columbia River shipping channel. 

In addition, workers dependent on 

port business reportedly are losing 

about $4 million a month, and shipping firms also are suffering loss of 

business. 

The number of victims stands at 25 

dead and 37 missing and presumed 

dead as of late June. Searches for the 

missing now are being made only when 

there is evidence that can be used to 

pinpoint areas of search. Search dogs 

are often brought in by helicopter to 

help find human remains. Still, no 

trace of USGS volcanologist Johnston 

has been found. 

How many lives were saved because 

essential information about the 

volcanic hazards was available and 

was used to reduce public risks? There 

will, of course, never be a precise 

answer, but estimates can be made. 

Forest Service records indicate that, 

during a nice spring weekend, as many 

as 2,000 visitors normally would have 

been in the Spirit Lake area. The added 

attraction of an active volcano might 

have brought as many as several thousand people into the area of destruction, had it not been for the designation and closure of the hazard zone. 

Continuing 

Hazards 

Potential hazards related to the 

Mount St. Helens eruptions have continued beyond the first 100 days. Information about these hazards comes 

from several sources. The discussion of 

hazards from ashfall, lateral blasts, 

pyroclastic flows, lava flows, and 

mudflows is taken mostly from an information bulletin (Federal Emergency 

Management Agency, 1980) prepared 

by Crandell. (Although he compiled 

that information before the June lava 

dome was seen, he anticipated its appearance.) Infor rna tion on flood 

hazards is modified from a description 

prepared by USGS hydrologists to 

accompany a May 29 Hazards Watch 

update. Information on fire hazards 

comes from a variety of sources, including discussions with Forest Service 

officials. The following perceptions of 

hazards, as well as the hazardous conditions themselves, undoubtedly will 

change in the future. 

ASHFALL 

Because Mount St. Helens is still in 

an explosive eruptive phase, eruptions 

similar to those of May 25 and June 12 

should be expected. Either a coarser 

grained pumice and ash eventually will 

erupt from the volcano, or else magma 

will form a dome within the present 

crater. The formation of a dome also 

could be accompanied by an eruption 

of ash, probably smaller than the eruptions of May 18 and 25. As of June 

1980, it was not known whether such 

changes would take days or weeks. 

If the maximum expectable eruption 

of pumice and ash were to occur, appreciable amounts could fall in any 

direction from the volcano but would 

be more likely in southeasterly, easterly, and northeasterly directions 

because of the most probable wind patterns. As the May 25 and June 12 

114 The First 100 Days of Mount St. Helens 

ashfall patterns show, however, areas 

in other directions cannot be considered immune. The actual areas 

covered by future ashfalls would de-

. pend on the directions and strengths of 

winds at the altitudes reached by an 

ash column at the time of an eruption. 

The effects of the May 18 ashfall, bad 

as they were, would have been incalculably worse if the winds had carried the ash northward over the major 

cities of northwestern Washington. 

Autopsies on people killed by the 

May 18 eruption indicate that the inhalation of hot ash was a major cause 

of death. Thus, hot ash clouds from the 

volcano, even from an eruption otherwise considered to be "light" or 

"moderate," can be an extreme hazard 

to humans and animals nearby. 

LATERAL BLASTS 

Present conditions at the volcano 

suggest that another lateral blast 

similar in force to the one of May 18 is 

unlikely unless a prolonged period of 

increasing seismicity and ground deformation occurs. However, the extrusion 

of a dome within the crater might be 

accompanied by lateral blasts that 

could carry rock debris outward at 

high velocity. The present shape of the 

crater suggests that lateral blasts from 

a growing dome most likely would be 

directed northward; blasts in other 

directions would tend to be deflected 

upward by the crater walls. If a dome 

were to grow to a height above the 

crater rim, however, lateral blasts also 

could affect the western, southern, or 

eastern sides of the volcano. 

Magma could move into subsurface 

parts of the volcano at some point east, 

south, or west of the existing crater. 

Such movement probably would cause 

inflation that could be detected by 

surveys and perhaps also by visual 

observation, as the north-flank bulge 

of March 27 to May 18 was. Surveying 

and tiltmeter observations have been 

resumed, but, at the end of June 1980, 

no such bulge or other sign of instability had been detected on the other 

flanks. 
LAVA FLOWS 

Explosive eruptions of dacite, like 

those of May 18 and 25 and June 12, 

typically are not accompanied by lava 

flows. Molten dacite is relatively 

viscous and would tend to pile up 

around a vent and form a dome rather 

than a lava flow. The past history of 

the volcano suggests that, as this eruption progresses, magma of a more fluid 

type could be extruded and might form 

lava flows. Flows, however, are not 

anticipated in the near future. 

PYROCLASTIC FLOWS 

Pyroclastic flows can form during an 

eruption of pumice and ash. The 

largest and longest pyroclastic flows, 

which could be expected during an 

eruption of coarse pumice, would occur as a large eruption column was rising above the volcano. Pyroclastic 

flows of this kind most probably 

would follow the valleys of the North 

Fork Toutle River, Muddy River, and 

Pine Creek because the present northward opening of the crater rim and the 

notch in the southeastern wall of the 

crater would direct them toward these 

valleys. They are less likely, although 

possible, on all other sides of the 

volcano. 

Pyroclastic flows probably would 

occur also during the eruption of a 

large dome. Such flows could be 

formed as the steep and unstable flanks 

of the dome crumbled and avalanched 

or as they were disrupted by earthquakes and volcanic explosions. 

Pyroclastic flows ~f this type probably 

would not extend into the North Fork 

Toutle River valley more than 10 miles 

from the dome, and they would not occur at all in the other valleys as long as 

the crater rim retained its present 

shape. 

MUDFLOWS 

The debris-avalanche deposit that 

now forms the floor of the upper North 

Fork Toutle River valley appears to be 

stable in the opinion of soil-mechanics 

experts who have examined it. The 

possibilities of piping (erosion along 

subsurface water conduits) or of sudden liquefaction of the deposit during a 

strong earthquake appear to be negligible in view of the fairly gradual general 

slope of the deposit and its poorly 

sorted texture. Mudflows may occur as 

streams cut down through the debrisflow deposit, but they probably would 

be small in volume in the immediate 

future and would not reach the heights 

or distances of the May 18 and 19 

mudflows. Probably the greatest 

potential for major mudflows lies in 

the possibility that water in ponds 

behind the debris dams blocking 

tributary streams along the valley of 

the North Fork Toutle River could 

break out. A sudden outburst of this 

impounded water, especially from the 

largest pond at the mouth of Coldwater Creek (fig. 45), could rush down 

the valley of the North Fork, increasing 

in volume as it mixes with the easily 

erodible mudflow deposits, and might 

become large enough to inflict damage 

in the main Toutle River valley. The effects of such an outburst, if it were to 

occur, would be intensified by the 

diminished capacities of the stream 

channels. The principal danger zone of 

such mudflows would be in the North 

Fork Toutle River valley. Ample warning of any such outburst mudflow 

probably can be assured by continuous 

monitoring of water levels in the 

ponds. 

Mudflows could also be caused by 

pyroclastic flows occurring during 

heavy rainfall or moving across snowcovered flanks of the volcano. Although this type of mudflow could occur in any valley that heads at the 

volcano, it would be most likely in the 

valleys of the North and South Forks 

of the Toutle River, Pine Creek, and 

Muddy River, which are the most 

probable routes for pyroclastic flows. 

Mudflow hazard zones should be 

regarded as extending up to and onto 

the flanks of the volcano. 

In the long run, increased discharge 

into Spirit Lake by streams in its 

drainage basin could occur during 

periods of heavy precipitation and (or) 

rapid snowmelt. Although the lake 

currently has no surface outlet, water 

from the lake is se~ping into and 

through the debris flow. During times 

of rapid inflow into the lake, water 

could enter the lake faster than seepage 

through the debris flow could carry it 

away. In such a situation, the lake 

water might rise to the top of the valley 

fill west of the lake, spill over, and 

begin to erode a new outlet channel. If 

the rate of spillover from the lake were 

adequate and if water were available 

from other sources, such as ponds behind debris dams at the mouths of 

tributaries, mudflows could form in 

the North Fork Toutle River valley. 

USGS hydrologists are studying this 

situation. 

FLOODS 

Sediment and debris in the channels 

of the Toutle and Cowlitz Rivers have 

increased greatly the short-term 

flooding hazard posed by even 

relatively small storms. Moreover, the 

threat of flooding in the Toutle River 

valley and along the Cowlitz River 

from the mouth of the Toutle downstream to the Columbia River may remain one of the greatest residual 

hazards associated with the volcanic 

activity. 

The Cowlitz channel was filled as 

much as 15 feet above its normal 

depth. The flood-carrying capacity of 

the channel thus was reduced by about 

85 percent, from a former ability to 

carry 76,000 cubic feet per second to a 

capacity of about 10,000 cubic feet per 

second. A flow of 10,000 cubic feet per 

second is about the average annual 

discharge of the river, and wet-season 

freshets often cause flows at several 

times that rate. Therefore, unless the 

channel can be restored and maintained at or near its former capacity, 

more frequent flooding seems inevitable. 

Although dredging of the Cowlitz 

channel undoubtedly will help, at least 

At the End of the First 100 Days 115 
during the first major flood, the problem is complicated by the vast amount 

of easily erodible sediment in the Toutle drainage area. This sediment will 

move downstream, mostly during 

periods of high flow, and may occasionally add to the sediment "plug" in 

the Cowlitz channel. 

FIRES 

As of June 1980, hundreds of 

smoldering fires still were burning in 

the timber beneath the volcanic ash 

near Mount St. Helens. The danger of 

these fires breaking out and spreading 

to standing timber is greatest during 

the dry season and is a threat to timber 

on Federal, State, and private lands. 

Hot spots caused by the buried fires 

can be located by using infrared sensors carried on aircraft, but reaching 

and extinguishing the fires pose other 

problems. Firefighters are hampered by 

a lack of ready access, by the aggravating ash, and, most of all, by the 

OUTLOOK FOR THE FUTURE 

The question of greatest interest concerning the future of Mount St. Helens 

probably is, "Will Mount St. Helens 

continue to erupt?" 

The answer is, "Yes." The volcano 

most probably will go through a period 

of repeated small- to moderate-scale 

eruptions producing ash, pyroclastic 

flows, and lava-dome growth. No one 

can predict how long that period will 

continue or how many such eruptions 

will take place. Less likely, but not impossible, is another large eruption 

among the expected smaller eruptions. 

The natural evolution of Mount St. 

Helens and a few other Cascade Range 

volcanoes, as geologic evidence accumulated over the last several decades 

indicates, has included repeated explosive destruction of parts of the 

volcanic cones followed by generally 

longer periods of cone rebuilding. Both 

the destructive and the rebuilding 

phases have involved eruptions that 

could (and often did) damage the surrounding countryside. No one can be 

certain yet that Mount St. Helens is 

truly in a rebuilding phase; moreover, 

even if it is, the volcanic activity may 

take a different course this time. For 

example, the rebuilding may include 

long periods of nonexplosive lava 

eruptions, similar to those at Bezymianny, Siberia, in the U.S.S.R.(Gorshkov, 1959) (fig. 61A). Conversely, 

frequent explosive eruptions that 

remove accumulated lava might continue for years in the future (fig. 61B). 

Seismologists at the University of 

Washington and USGS are cautiously 

optimistic that a pattern of preeruptive 

seismic activity at Mount St. Helens 

may provide advance warning of 

future eruptions. The key to forecasting volcanic activity may be the 

pattern of harmonic tremor. Before 

both the May 25 and the June 12 eruptions, the tremor built up steadily and 

then stopped for a time just before the 

explosive eruptions. The pattern must 

be used cautiously, however, because 

it was seen on June 2 and 3 as well, and 

no eruption occurred. If, however, the 

seismic pattern proves to be a useful 

predictive tool at Mount St. Helens, it 

may be useful for other volcanoes, as 

well. Some scientists believe that using 

this seismic clue to predict and assess 

volcanic activity could help save lives. 

Other Cascade volcanoes also will 

erupt in the future, just as surely as 

they have erupted in the past. There is 

every reason to believe that the oceanic 

crustal plates will continue to thrust 

under the North American plate and 

generate magma to feed future eruptions (figs. 1 and 2). The rate of underthrusting is relatively slow, how116 The First 100 Days of Mount St. Helens 

need for heavy machinery to uncover 

and unpile the smoldering logs. 

All or most of the fires still burning 

beneath the ash were set by the lightning and hot debris that fell during the 

May 18 eruption, and more fires could 

be set by lightning accompanying 

future eruptions of ash and ash avalanches. Many of the volcano's previous heavy eruptions of ash were accompanied by lightning, so it is 

reasonable to assume that future eruptions might bring ash-generated lightning into standing forests. 

ever-on the order of 1 inch a yearso, in the long run, Cascade volcanoes 

may be expected to erupt less frequently than some other groups of volcanoes 

around the Pacific Ocean's "Ring of 

Fire." The possibility still exists, however, that any volcano could erupt 

again at any time. Although scientists 

are not now capable of predicting 

which of the other Cascade volcanoes 

will be the next to erupt, the lessons 

learned from Mount St. Helens may 

allow them to forecast more accurately 

when a volcano is approaching eruption and to better anticipate when that 

eruption will occur. Volcanoes, 

however, are notoriously individualistic; therefore, much of what is learned 

by studying the activity at Mount St. 

Helens might not be valid if another 

Cascade volcano came to life. 

The May 18 eruption of Mount St. 

Helens was not a large eruption by 

world historical standards or even 

among prior Cascade eruptions, 

although it was by far the most powerful of the year and, perhaps, of the last 

decade. Mount St. Helens is only one 

of perhaps 50 volcanoes worldwide 

that were active during 1980. As figure 

62 shows, the amount of volcanic 

material thrown out of Mount St. 

Helens on May 18 (less than one-tenth 

cubic mile) was only about oneeightieth of the volume ejected during 

the 1815 eruption of Tambora volcano 

in Indonesia and less than onehundreth of the estimated ejecta from 
FIGURE 61.-Two possible futures for 

Mount St. Helens. A, The recent history 

of Bezymianny, Siberia, in the U.S.S.R., 

suggests one possible behavior pattern 

for Mount St. Helens in the near future. 

After exploding violently in March 1956 

with a lateral blast that created an amphitheater crater similar to that of Mount 

St. Helens, Bezymianny has remained active; dome-building lava extrusions have 

dominated the volcanic activity. However, explosive eruptions also have occurred, the last in 1979. (Photograph by 

S. Gorshkov, May 1957, from Bulletin 

Volcanologique, 1959.) B, Mount St. 

Helens may continue in the near future 

having occasional explosive eruptions 

that remove accumulated lava. An eruption on July 22, 1980, shown here in 

progress, blew away nearly all of the 

June dome and thus confirmed the expectation of most volcanologists that explosive activity was not ended by the appearance of that dome. (Photograph 

copyright 1980 by J. Stewart Lowther, 

University of Puget Sound.) 
5000 B.C. 

A.D. 79 

1707 

1815 

1842-

1857 

1883 

1912 

1956 

1980 

Vesuvius, Italy 

Fuji, Japan 

" 1" ", -r,;; ~- - -- ~ "'"~ .,t·;"" : "'o.t 

' ~ 

~ " ~ ~ ~ 

v ' 

I Mount St. Helens 

Krakatoa, Indonesia 

Mount Katmai, Alaska 

I Bezymianny, Kamchatka 

I MOUNT ST. HELENS 

0 2 3 4 5 6 - 7 8 9 10 

Volume, in cubic miles 

FIGURE 62.-Comparison of the volumes of ejecta thrown out by selected volcanoes during 

historic eruptions. The volume of ejecta from the May 18 eruption of Mount St. Helens 

(less than one-tenth of a cubic mile, not including avalanche or mudflow deposits) is 

relatively small in comparison with amounts from several earlier eruptions, including 

those from Mount Mazama (Crater Lake) in Oregon. (Data from Hedervari, 1963; 

Friedman and others, 1981; other USGS sources.) 

118 The First 100 Days of Mount St. Helens 

Mount Mazama during the eruptive 

period that resulted in Crater Lake. 

Therefore, future eruptions of large 

Cascade volcanoes, including Mount 

St. Helens itself, might be even larger 

than the May 18 eruption. 

So far as volcano experts know, the 

magma reservoirs deep beneath the 

Cascade volcanoes are not interconnected-at least not to the degree that 

an eruption at one volcano increases 

(or lessens) the chances of eruption at 

another. Nor are the region's earthquakes typically related to volcanic activity, except for the unusual shallow, 

frequent quakes ("swarms") of the kind 

that preceded the March 27 eruption of 

Mount St. Helens. The normal, deeper 

earthquakes are related to volcanic activity only indirectly-that is, only in 

the sense that earthquakes and 

volcanic activity all result from the 

same complex system of moving 

crustal plates (Hamilton, 1977). 

Erosion of the volcano's deposits, as 

well as transport and deposition of the 

sediment derived from this erosion, 

will continue at a rate that is historically unprecedented in southwestern 

Washington. Moderate to intense 

rainstorms or even rapid melting of 

snow are now much more likely to 

cause flash floods and mudflows than 

they were before May 18, because little 

vegetation remains in the blast area to 

retard runoff and erosion and because 

all the volcano-related deposits are 

readily erodible. The erosion is most 

rapid on bare or ash-covered steep 

slopes, especially where avalanche 

debris and mudflow deposits have 

buried former stream channels at considerable depths. These deposits have 

disrupted greatly the natural stream 

gradients, which adjust automatically 

to the cdmbination of sediment load, 

water available to carry the sediment, 

and differences in the altitudes of the 

headwaters of the channel system and 

of the stream mouth. Stream channels 

began adjusting (by erosion and sediment deposition) to the new volume of 

sediment supplied by the volcano during the floods of May 18 and 19 and 

will continue to do so for the fore-
seeable future-probably for several 

decades. Erosion occurs most rapidly 

during periods of high runoff and 

floodflows, and sediment is deposited 

largely as floods begin to subside. In 

western Washington, more than 90 

percent of sediment transport by 

streams takes place during brief 

periods of high runoff from rainstorms 

and rapid snowmelt. The sediment 

loads carried by the Toutle River to the 

lower Cowlitz River and by the 

Cowlitz to the Columbia River also are 

greatest during these high-runoff 

periods, which usually occur during 

winter, spring, or late autumn. 

Sediment transport from the Toutle 

River system will be an integral part of 

the stream-gradient readjustment; it is 

inevitable and will be largely uncontrollable by human intervention. Flood 

hazards along the lower Cowlitz River, 

however, can be reduced by dredging 

out previous flood deposits to increase 

channel capacity before the arrival of 

each succeeding flood and its new load 

of sediment. 

Some areas that probably will be 

subject to a great deal of erosion or 

sediment deposition can be identified 

now; other areas where such changes 

may occur in the future will be found 

through studies now being conducted 

by the USGS and other organizations. 

After a few annual cycles of high and 

low streamflow, the patterns and 

trends of erosion, flooding, and sediment deposition will be more apparent 

than they are at present. 

Revegetation is occurring in the 

blast-cleared areas, with and without 

human assistance. Surviving trees and 

other plants around the devastated 

area, especially the few small stands of 

remaining old-growth trees, would 

seem to be of critical importance in 

reestablishing the forest ecosystem. 

New vegetation eventually will slow 

erosion on the slopes but, in the short 

run, will have little effect on the readjustment of major stream channels 

themselves. 

At times when the capacity of the 

lower Cowlitz River channel is substantially smaller than it was before 

May 18, the susceptibility of the lower 

Cowlitz to flooding may complicate 

the management and operation of 

hydropower reservoirs upstream. The 

reservoirs upstream from the Toutle 

River conceivably could be managed 

so that they provide more flood control than they have in the past. That is, 

reservoir levels could be controlled so 

that there would be storage volume 

available to retain peak flows from the 

upper Cowlitz basin when floodflows 

of the Toutle River (or other downstream tributaries) threaten to exceed 

the limited channel capacity of the 

lower Cowlitz. Operating those reservoirs to increase their flood-controlling 

capacity, however, might reduce the 

amount of electrical power that they 

can provide. 

The low-level flows of streams that 

drain the flanks of the volcano and that 

are sustained largely by melt water 

from glaciers and snowfields on the 

mountain will be reduced to some extent because much glacial ice was lost 

on May 18. How the remaining glaciers 

will adjust and what the effects of this 

adjustment on the flows of the various 

streams are likely to be are now being 

studied by USGS hydrologists and 

glaciologists. If eruptions were to become less frequent and the volcano 

were to cool and stabilize in its present 

form, year-round snowfields or even a 

glacier might grow inside the largely 

shaded amphitheater. A crater lake 

also might form; if it did, it probably 

would act like a reservoir for a stream 

(or streams) draining from it, 

presumably to the North Fork Toutle · 

River. 

The main uses of land on and near 

Mount St. Helens before the 1980 eruptions were generally well suited to an 

area of long-term volcanic hazards, 

and these uses probably will be resumed. Forestry, farming, recreation, 

and hydropower generation seem to 

have struck a reasonable balance between using the land productively and 

minimizing human risk. In view of the 

known volcanic mudflow deposits in 

the major river valleys (including the 

site of the town of Castle Rock) and the 

frequency of historical volcanic activity, human occupancy of the flood 

plains was probably a less appropriate 

use. As volcanic activity decreases in 

the future and as former land uses are 

resumed, new flood plains (mudflow 

deposits) can be used more appropriately for nonresidential purposes. These valley-floor areas, along 

with the areas near and north of the 

crater mouth, should be considered the 

most hazardous places, unless changes 

occur indicating increased volcanic activity or related hazards on other sides 

of the mountain, as well. 

Human reactions to the hazards 

and to warnings about them are being 

studied, and the lessons learned from 

the first 100 days of Mount St. Helens' 

activity doubtlessly will be applied to 

future hazard warnings and responses 

of emergency-services agencies. 

Visitor information centers such as 

those already established near Interstate Highway 5 are of great benefit 

in informing the public about eruptions, about volcanic hazards, and 

about the natural-hazards warning 

procedures. An essential prelude to 

good education already has been 

achieved; Mount St. Helens' eruptions 

have increased the American public's 

awareness of and interest in volcanic 

activity in the Cascade Range and elsewhere in the world. 

State of Washington officials, looking 

beyond the dampening effect that the 

eruptions have had on the State's important tourist industry, envision a 

future that includes a Mount St. Helens 

National Park (or Monument or 

Volcano Area); as many as 2 million 

visitors to the volcano each year; more 

motels, restaurants, and visitor centers 

near the mountain; and a resultant 

$150 million boost to the State 

economy. 

Even President Carter, when he 

visited the devastated area, predicted 

that, "People will come from all over 

the world to observe-when it's safe. It 

will be a tourist attraction to equal the 

Grand Canyon." 

Public tours of the volcano itself, 

however, may be a long time off. 

Outlook for the Future 119 
Volcanologists warn that relatively 

small but dangerous eruptions might 

be expected for an indefinite time. 

Mount St. Helens' eruptive period during the mid-1800's apparently spanned 

at least 15 years. 

How soon it will be "safe" to approach the volcano on its northern 

side, no one can answer simply. Part of 

the answer depends, as Mullineaux 

recently said, on "how much risk one is 

willing to assume" (fig. 63). Some difficult decisions will have to be made 

about when and where to open the 

restricted areas. For the foreseeable 

future, a continuing flow of sound 

scientific information will be needed to 

guide these decisions and others like 

them; the USGS intends to provide 

such geologic and hydrologic information as long as it is needed. If intermittent explosive eruptions and dome 

building continue as expected, the need 

for such information may extend for 

years or even decades. 

120 The First 100 Days of Mount St. Helens 

FIGURE 63.-The June 1980 dome viewed 

though "the gun barrel, " the northsloping ramp bounded by sidewalls of the 

Mount St. Helens crater. This informal 

name, used by scientists and officials, 

acknowledges the continuing hazards of 

working in the area north of the crater 

mouth. This ramp, sculpted by the May 

18 lateral blast, was the route taken by 

several later pyroclastic flows that would 

have cremated anyone caught in their 

paths. (Photograph copyright 1980 by 

Bud Kimball.) 
GEOLOGIC HAZARD RESPONSIBILITIES 

The broad responsibilities assigned 

to the USGS by the Organic Act of 

1879 include collecting, analyzing, and 

dissemina ting information about the 

Earth, its processes, and its wa ter and 

mineral resources. As part of its basic 

historical mission, the USGS has, for 

many decades, undertaken studies of 

earthquakes, volcanoes, and other 

natural hazards. In recent years, as 

knowledge of these phenomena and 

related geologic processes has increased, the USGS has developed capabilities for predicting some potentially 

hazardous events in certain areas. The 

USGS has an implicit obligation to inform civil authorities and the public of 

all such predictions. 

The USGS mechanism for assuring 

that the public and its officials get 

needed information quickly and in a 

form suitable to their needs is the 

Hazards Warning and Preparedness 

Program, developed in 1976 in 

response to previous Federal legislation. Under the provisions of Public 

Law 93-288, the "Disaster Relief Act of 

1974" (88 Stat. 143), and subsequent 

delegations of responsibility, the Director of the USGS is required to " . . . 

provide technical assistance to State 

and local governments to insure that 

timely and effective disaster warning is 

provided ... for an earthquake, volcanic eruption, landslide, mudslide, or 

other geological catastrophe." 

A USGS Hazards Information Coordinator receives information about a 

potential geologic hazard and then is 

responsible for obtaining expert review 

of the data and conclusions and for 

disseminating information to the 

public, government officials, and news 

agencies. The program's procedures, 

outlined in the Federal Register of 

April 12, 1977, define three levels of 

geologic-hazard information and 

notification: 

• Notice of Potential HazardInformation on the location and 

possible magnitude of a potentially 

hazardous geologic condition. 

• Hazard Watch-Information, as it 

develops from monitoring or from 

observed precursors, that a potentially catastrophic event of a generally predictable magnitude may 

occur within an indefinite time 

(possibly months or years). 

• Hazard Warning-Information (prediction) as to the time, location, and 

magnitude of a potentially disastrous geologic event. 

Notices are then sent to appropriate 

local, State, and Federal agencies and, 

through the news services, to the 

public. 

These procedures do not apply to 

flood warnings, even if the floods are 

related to volcanic activity. Flood 

warnings, as well as predictions about 

windborne ash distribution, are the 

responsibility of the National Weather 

Service of the National Oceanic and 

Atmospheric. Administration. 

Concern about potential hazards 

posed by Cascade Range volcanoes led 

the USGS to establish a Volcanic 

Hazards Project in 1967. This project is 

based on the concept that a volcano's 

behavior pattern can be determined by 

studying deposits formed by its past 

eruptions. This project assesses the 

potential threat of a volcano by a 

special kind of geologic "detective 

work. " Such investigations involve 

determining (1) the ways in which 

various volcC!nic rock materials and 

deposits originated, (2) the order and 

sequence in which rock materials from 

the volcano and other deposits interbedded with them were deposited, (3) 

the timing of past volcanic events as indicated by the deposits that they produced, and (4) the various areas that 

received deposits from and, therefore, 

were affected by past eruptions. Modern eruptions of a volcano may not affect exactly the same areas exactly the 

way that a geologic study might indicate; such studies of areas affected in 

the past are, however, the best gage 

available and are used as a rough guide 

to the potential impacts of future eruptions. 

GLOSSARY OF VOLCANIC 

AND RELATED TERMS 

Active volcano : A volcano that is 

erupting . Also, a volcano that is 

not presently erupting but that has 

erupted within historical time and 

is considered likely to do so in the 

fu ture (there is no distinction between "active " and "dormant" in 

this sense). 

Andesite : Volcanic rock (or lava ) characteristically medium da rk in 

color and containing 54 to 62 percent silica and moderate amounts 

of iron and magnesium. 

Ash (volcanic): Fine pyroclastic material in fragments less than 4.0 

millimeters in diameter. "Ash" in 

this sense is quite distinct from the 

ash produced by common combustion because the rocks do not 

catch fire and burn during a volcanic event. 

Ash cloud: Eruption cloud containing 

appreciable amounts of ash. 

Ashfall (airfall): Volcanic ash that has 

fallen through the air from an 

eruption cloud. A deposit so 

formed is usually well sorted and 

layered. 

Ash flow : A pyroclastic flow consisting 

predominantly of ash-sized (less 

Geologic Hazard Responsibilities 121 
than 4 millimeters in diameter) 

particles. Also called a glowing 

avalanche if it is of very high 

temperature. 

Avalanche: A large mass of material 

or mixtures of material falling or 

sliding rapidly under the force of 

gravity. Avalanches often are 

classified by their content, such as 

snow, ice, soil, or rock avalanches. A mixture of these 

materials is a debris avalanche. 

(See also Debris avalanche.) 

Basalt: Volcanic rock (or lava) that 

characteristically is dark in color, 

contains 45 to 54 percent silica, 

and generally is rich in iron and 

magnesium. 

Crater: A steep-sided, usually circular 

depression formed by either explosion or collapse at a volcanic vent. 

Dacite: Volcanic rock (or lava) that 

characteristically is light in color 

and contains 62 to 69 percent silica 

and moderate amounts of sodium 

and potassium. 

Debris avalanche: A rapid and unusually sudden sliding or flowage 

of unsorted masses of rock and 

other material. As applied to the 

major avalanche involved in the 

eruption of Mount St. Helens, a 

rapid mass movement that included fragmented cold and hot 

volcanic rock, water, snow, 

glacier ice, trees, and some hot 

pyroclastic material. Most of the 

May 18 deposits in the upper 

valley of the North Fork Toutle 

River and in the vicinity of Spirit 

Lake are from the debris avalanche. 

Dome: A steep-sided mass of 

viscous (doughy) lava extruded 

from a volcanic vent, often circular in plan view and spiny, 

rounded, or flat on top. Its surface 

is often rough and blocky as a 

result of fragmentation of the 

cooler, outer crust during growth 

of the dome. 

Dormant volcano: A volcano that is 

not presently erupting but that is 

considered likely to erupt in the 

future. (See also Active volcano.) 

Ejecta: Material that is thrown out 

by a volcano, including pyroclastic material (tephra) and, 

from some volcanoes, lava 

bombs. 

Extinct volcano: A volcano that is 

not presently erupting and is not 

likely to do so for a very long time 

in. the future. 

Fumarole: An opening at the Earth's 

surface from which water vapor 

and other gases are emitted, often 

at high temperature. 

Graben: An elongate crustal block 

that is relatively depressed 

(downdropped) between two fault 

systems. 

Harmonic tremor: A continuous 

release of seismic energy typically 

associated with the underground 

movement of magma. It contrasts 

distinctly with the sudden release 

and rapid decrease of seismic 

energy associated with the more 

common type of earthquake 

caused by slippage along a fault. 

Lava: General term for magma 

(molten rock) that has been 

erupted onto the surface of the 

Earth. 

Lava flow: An outpouring of lava 

onto the land surface from a vent 

or fissure. Also, a solidified 

tonguelike or sheetlike body 

formed by outpouring lava. 

Magma: Molten rock beneath the 

surface of the Earth. (See also 

Lava.) 

Magnitude: A numerical expression 

of the amount of energy released 

by an earthquake, determined by 

measuring earthquake waves on 

standardized recording instruments (seismographs). The number scale for magnitudes is logarithmic rather than arithmetic; 

122 The First 100 Days of Mount St. Helens 

therefore, deflections on a 

seismograph for a magnitude 5 

earthquake, for example, are 10 

times greater than those for a 

magnitude 4 earthquake, 100 

times greater than for a magnitude 

3 earthquake, and so on. 

Mudflow: A flowage of watersaturated earth material possessing a high degree of fluidity during 

movement. A less-saturated flowing mass is often called a debris 

flow. A mudflow originating on 

the flank of a volcano is properly 

called a lahar. 

Phreatic eruption (explosion): An 

explosive volcanic eruption 

caused when water and heated 

volcanic rocks interact to produce 

a violent expulsion of steam and 

pulverized rocks. Magma is not 

involved. 

Pumice: Light-colored, frothy volcanic rock, usually of dacite or 

rhyolite composition, formed by 

the expansion of gas in erupting 

lava. Commonly perceived as 

lumps or fragments of pea size and 

larger but can also occur abundantly as ash-sized particles. 

Pyroclastic: Pertaining to fragmented (clastic) rock material 

formed by a volcanic explosion or 

ejection from a volcanic vent. 

Pyroclastic flow: Lateral flowage of 

a turbulent mixture of hot gases 

and unsorted pyroclastic material 

(volcanic fragments, crystals, ash, 

pumice, and glass shards) that can 

move at high speed (50 to 100 

miles an hour). The term also can 

refer to the deposit so formed. 

Rhyolite: Volcanic rock (or lava) that 

characteristically is light in color, 

contains 69 percent silica or more, 

and is rich in potassium and 

sodium. 

Tephra: Materials of all types and 

sizes that are erupted from a crater 

or volcanic vent and deposited 

from the air. 
MORE ABOUT MOUNT ST. HELENS 

AND OTHER VOLCANOES 

Anderson, C. A. , 1980, Volcanoes: 

U.S. Geological Survey information 

leaflet 341-618-28, 9 p. 

Atwater, Tanya , 1970, Implications 

of plate tectonics for the Cenozoic tectonic evolution of Western North 

America: Geological Society of 

America Bulletin, v. 81 , p . 3513- 3536. 

Beget, J. E., 1979, Late Pleistocene 

and Holocene pyroclastic flows and 

lahars at Glacier Peak, Washington 

[abs.]: Geological Society of America 

Abstracts with Programs, v. 11, pt. 3, 

Cordilleran Section, p. 68. 

Bartleson, G. C., Wilson, R. T ., and 

Foxworthy, B. L., 1977, Water-quality 

effects on Baker Lake of recent 

volcanic activity at Mount Baker, 

Washington: U.S. Geological Survey 

Professional Paper 1022-B, p. B1- B30. 

Brugman, M . M. , and Post, Austin , 

1981, Effects of volcanism on the 

glaciers of Mount St. Helens: U.S. 

Geological Survey Circular 850-D, p. 

D1-D11 . 

Christiansen , R. L., 1980, Eruption 

of Mount St. Helens: Volcanology: 

Nature. v. 285, no . 5766, p. 531- 533. 

Crandell, D . R. 1971, Postglacial lahars 

from Mount Rainier volcano, 

Washington: U.S . Geological Survey 

Professional Paper 677, p. 75. 

----1976, Preliminary assessment of 

potential hazards from future eruptions in Washington: U.S. Geological 

Survey Miscellaneous Field Studies 

Map MF-774, scale 1:1,000,000 (with 

text). 

----1980, Recent eruptive history of 

Mount Hood, Oregon, and potential 

hazards fom future eruptions: U.S. 

Geological Survey Bulletin 1492, 81 p. 

Crandell, D. R., and Mullineaux, D. R. , 

1967, Volcanic hazards at Mount 

Rainier, Washington : U.S. Geological 

Survey Bulletin 1238, p. 26 . 

----1973, Pine Creek volcanic 

assemblage at Mount St. Helens, 

Washington: U.S. Geological Survey 

Bulletin 1383- A, 23 p . 

----1975, Technique and rationale 

of volcanic-hazards appraisals in the 

Cascade Range, northwestern United 

States: Environmental Geology, v. 1, 

no. 1, p. 23- 32. 

----1978, Potential hazards from 

future eruptions of Mount St. Helens 

volcano, Washington: U.S. Geological 

Survey Bulletin 1383-C, 26 p. 

Crandell, D. R., Mullineaux, D. R., and 

Rubin, Meyer, 1975, Mount St. Helens 

volcano: Recent and future behavior: 

Science, v. 187, no. 4175, p. 430- 441. 

(Reprinted in The Ore Bin, 1975, v. 37, 

no. 3, p. 41-48.) 

Cummans, John, 1981, Mudflows resulting from the May 18, 1980, eruption of Mount St. Helens, Washington: 

U.S. Geological Survey Circular 

850-B, p. B1-B16. 

Day, A. L., and Allen, E. T., 1925, The 

volcanic activity and hot springs of 

Lassen Peak: Carnegie Institution of 

Washington Publication 360, 190 p . 

Endo, E. T ., Malone, S. D., Noson, L. L., 

and Weaver, C. S., 1981, Locations, 

magnitudes, and statistics of the March 

20- May 18 earthquake sequence, in 

Lipman, P. W., and Mullineaux, D. R., 

eds., The 1980 eruptions of Mount St. 

Helens, Washington: U.S . Geological 

Survey Professional Paper 1250, p. 

93-107. 

Federal Emergency Management Agency, 

1980, Current volcanic hazards at 

Mount St. Helens, Washington: 

Mount St. Helens Technical Information Bulletin 4, 8 p. 

Friedman, J. D., Olhoeft, G . R., Johnson, 

G. R., and Frank, David, 1981, Heat 

content and thermal energy of the June 

dacite dome in relation to total energy 

yield, May-October 1980, in Lipman, 

P. W., and Mullineaux, D. R., eds., 

The 1980 eruptions of Mount St. 

Helens, Washington: U.S . Geological 

Survey Professional Paper 1250, p. 

557-567. 

Fruchter, J. S., and others, 1980, Mount 

St. Helerts ash from the May 18 eruption-Chemical, physical, mineralogical, and biological properties: 

Science, v . 209, no. 4461, p. 

1116-1125. 

Greeley, R., and Hyde, J. H., 1972, Lava 

tubes of the Cave Basalt, Mount St. 

Helens, Washington: Geological Society of America Bulletin, v. 83, p. 

2397-2418 . 

Griggs, R. F., 1918, The Valley of Ten 

Thousand Smokes: National Geographic, v . 33, no. 2, p. 115- 169. 

Gorshkov, G . S., 1959, Gigantic eruption 

of the volcano Bezymianny: Bulletin 

Volcanologique, ser. 2, v. 20, p. 

77- 109. 

Hamilton, Warren, 1977, Plate tectonics 

and man: U.S. Geological Survey 

Yearbook, Fiscal Year 1976, p. 39- 53. 

Harris, S. L., 1980, Fire and ice: The 

Cascade volcanoes: Seattle, Mountaineers-Pacific Search Press, 316 p. 

Hedervari, P., 1963, On the energy and 

magnitude of volcanic eruptions: 

Bulletin Volcanologique, v. 25, p. 

373- 385. 

Hill, M . R., 1970, Mount Lassen is in 

eruption and there is no mistake about 

that: California Division of Mines and 

Geology Mineral Information Service, 

v. 23, no. 11, p. 211-224. 

Hopkins, K. D., 1969, Late Quaternary 

glaciation and volcanism on the south 

slope of Mount Adams, Washington 

[ abs.]: Geological Society of America 

Abstracts with Programs, 1969, v . 1, 

no . 3, Cordilleran Section, 27 p. 

Hopson, C. A., and Melson, W. G ., 1980, 

Mount St. Helens eruptive cycles since 

100 A .D. [abs.]: EOS, Transactions of 

the American Geophysical Union, v . 

61, no . 46, p. 1132-1133. 

Hunt, C. E., and MacCready, J. S., 1980, 

The short-term economic consequences of the Mount St. Helens 

volcanic eruptions in May and June, 

1980: Olympia, Washington State 

Department of Commerce and Economic Development, 56 p. 

Hyde, J. H., 1975, Upper Pleistocene 

pyroclastic-flow deposits and lahars 

south of Mount St. Helens volcano, 

Washington: U.S . Geological Survey 

Bulletin 1383- B, 20 p. 

Kieffer, H. H., Frank , David, and 

Friedman, J. D., 1981, Thermal infrared surveys at Mount St. 

Helens-Observations prior to the 

eruption of May 18, in Lipman, P. W., 

and Mullineaux, D. R., eds., The 1980 

eruptions of Mount St. Helens, ·washington: U.S. Geological Survey Professional Paper 1250, p. 257-277. 

Korosec, M. A., Rigby, J. G., and Stoffel, 

K. L., 1980, The 1980 eruption of 

More About Mount St. Helens and Other Volcanoes 123 
Mount St. Helens, Washington, pt. I, 

March 20-May 19, 1980: Washington 

State Division of Geology and Earth 

Resources Information Circular 71, 27 

p. 

Krafft, Maurice, and Krafft, Katia, 1975, 

Volcanoes: New York, Harry N. 

Abrams, 174 p. 

Lawrence, D . B., 1939, Continuing 

research on the flora of Mount St. 

Helens: Mazama, v . 21, no. 12, p . 

49-54. 

Lipman, P. W., and Mullineaux, D. R., 

eds., 1981, The 1980 eruptions of 

Mount St. Helens, Washington: U.S. 

Geological Survey Professional Paper 

1250, 844 p. 

Lombard, R. E., Miles, M . B., Nelson, 

L. M., Kresh, D . L., and Carpenter, 

P. J., 1981, Channel conditions in the 

lower Toutle and Cowlitz Rivers 

resulting from the mudflows of May 

18, 1980: U.S. Geological Survey Circular 850-C, p . C1-C16. 

Macdonald, G. A., 1972, Volcanoes: 

Englewood Cliffs, N . J., Prentice-Hall, 

510 p. 

Macdonald, G. A. , and Katsura, Takashi, 

1965, Eruption of Lassen Peak, 

California, in 1915: Example of mixed 

magmas: Geological Society of 

America Bulletin, v. 76, p. 475- 482. 

Malone, S. D. , and Frank, David, 1975, 

Increased heat emission from Mount 

Baker, Washington: EOS, Transactions of the American Geophysical 

Union, v. 56, no. 10, p. 679-685. 

Mathews, W . H ., 1952, Mount Garibaldi, 

a supra-glacial volcano in southwestern British Columbia : American 

Journal of Science, v. 250, p. 81-103. 

McKee, Bates, 1972, Cascadia-The 

geologic evolution of the Pacific 

Northwest: New York, McGraw-Hill, 

394 p. 

Miller, C. D ., 1980, Potential hazards 

from future eruptions in the vicinity of 

Mount Shasta volcano , northern 

California: U.S. Geological Survey 

Bulletin 1503, 43 p. 

Moore, J. G., and Albee, W. C., 1981, 

Topographic and structural changes, 

March-July 1980-Photogrammetric 

data, in Lipman, P . W. , and 

Mullineaux, D. R., eds., The 1980 

eruptions of Mount St. Helens, 

Washington: U.S. Geological Survey 

Professional Paper 1250, p. 123-134. 

Mullineaux, D. R., and Crandell, D. R., 

1962, Recent lahars from Mount St. 

Helens, Washington: Geological Society of America Bulletin, v. 73, p. 

855-870. 

Mullineaux, D . R., Hyde, J. H. , and Rubin, 

Meyer, 1975, Widespread late glacial 

and postglacial tephra deposits from 

Mount St. Helens volcano, Washington: Journal of Research of the U.S. 

Geological Survey, v. 3, no. 3, p. 

329-335. 

National Oceanic and Atmospheric 

Administration, 1980, Reprise at 

Mount St. Helens: NOAA, v . 10, no . 

4, p . 22- 23 . 

Phillips, K. N. , 1941, Fumaroles of Mount 

St. Helens and Mount Adams: 

Mazama, v. 23, no. 12, p . 37-42 . 

Posey, Carl, 1980, Down to St. Helens 

inferno : NOAA, v. 10, no. 4, p . 18- 21. 

Riddihough , R. P ., 1978, The Juan de Fuca 

Plate : EOS , Transactions of the 

American Geophysical Union, v. 59, 

no . 9, p . 836-842. 

Rose, W. 1. , and Harris, D. M. , 1980, 

Radar observations of ash clouds from 

the May 18, 1980, Mount St. Helens 

eruption [abs.]: EOS, Transactions of 

the American Geophysical Union, v. 

61 , no. 46, p . 1136. 

Sarna-Wojcicki, A. M., Shipley, Susan, 

Waitt, R. B., Jr. , Dzurisin, Daniel, and 

Wood, S. H., 1981, Aerial distribution, thickness, mass, volume, and 

grain size of air-fall ash from the six 

major eruptions of 1980, in Lipman, 

P . W. , and Mullineaux, D. R. , eds. , The 

1980 eruptions of Mount St. Helens, 

Washington: U.S. Geological Survey 

Professional Paper 1250, p. 577- 600. 

Sheets, P. D., and Grayson, D. K., eds. , 

1979, Volcanic activity and human 

ecology : New York, Academic Press, 

p. 644. 

Srivastava, S. P., Barrett, D. L., Keen, 

C. E. , Manchester, K. S. , Shih, K. G., 

Tiffen, D. L., Chase, R. L., Thomlinson, A . G., Davis, E. E. , and Lister, 

0. R. B. , 1971, Preliminary analysis of 

124 The First 100 Days of Mount St. Helens 

geophysical measurements north of 

Juan d~ Fuca Ridge: Canadian Journal 

of Earth Sciences, v. 8, p . 1265. 

Strong, Emory, 1969, Early accounts of 

the eruption of Mount St. Helens: 

Geological Society of the Oregon 

Country Geological News Letter, v . 

35, no. 1, p. 3-5. 

Tabor, R. W., and Crowder, D. F., 1969, 

On batholiths and volcanoes-Intrusion and eruption of Late Cenozoic 

magmas in the Glacier Peak area, 

North Cascades, Washington: U.S. 

Geological Survey Professional Paper 

604, 67 p. 

Tilling, R. 1., 1977, Monitoring active 

volcanoes: U.S. Geological Survey 

Yearbook, Fiscal Year 1977, p. 36-40. 

Unger, J. D., 1974, Scientists probe 

Earth's secrets at the Hawaiian 

Volcano Observatory: U.S. Geological 

Survey Earthquake Information 

Bulletin, v. 6, no. 4, p. 3-11. 

U.S. Soil Conservation Service, 1980, 

Mount St. Helens ash fallout impact 

assessment report: Spokane, U.S. 

Department of Agriculture, 78 p. 

University of Washington Geophysics 

Program, 1980, Eruption of Mount St. 

Helens-Seismology: Nature, v. 285, 

no. 5766, p. 529-531. 

Veerhoogen, Jean, 1937, Mount St. 

Helens- A recent Cascade volcano: 

University of California Publications 

in Geological Sciences, v. 24, no. 9, p. 

263-302. 

Wilcox, R. E., 1959, Some effects of 

recent volcanic ash falls, with especial 

reference to Alaska: U.S. Geological 

Survey Bulletin1028-N,p.N 409-N476. 

Williams, Howell, 1935, Newberry 

Volcano, central Oregon: Geological 

Society of America Bulletin, v. 46, no. 

2, p. 253-304. 

--- 1942, The geology of Crater 

Lake National Park, Oregon: Carnegie 

Institution of Washington Publication 

540, 162 p. 

----1944, Volcanoes of the Three 

Sisters region, Oregon Cascades: 

University of California Department of 

Geological Sciences Bulletin, v. 27, no. 

3, p. 37-84. 
UNIT CONVERSION 

Quantitative information in this report is given in the traditional (English) units 

of measurement that are most familiar to the general population of the United 

States, the intended major readership for this report. This conversion table is for 

the convenience of those who prefer metric units. 

Multiply inch-pound unit By To obtain 51 unit 

acre 4,047 square meter 

.4047 hectare 

cubic yard .7646 cubic meter 

cubic feet per second 28.32 liters per second 

.02832 cubic meters per second 

cubic mile 4.166 cubic kilometer 

foot .3048 meter 

gallon .003785 cubic meter 

3.785 liter 

gallons per minute .06309 liters per second 

inch 2.540 centimeter 

mile 1.609 kilometer 

miles per hour 1.609 kilometers per hour 

square mile 2.59 square kilometer 

ton, short (2,000 pounds) .9072 ton, metric 

907.1848 kilograms 

Unit Conversion 125