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Direct Temperature Measurements of Deposits, 

Mount St. Helens, Washington, 1980-1981

By Norman G. Banks and Richard P. Hoblitt

U.S. GEOLOGICAL SURVEY PROFESSIONAL PAPER 1387

UNITED STATES GOVERNMENT PRINTING OFFICE, WASHINGTON: 1996
U.S. DEPARTMENT OF THE INTERIOR 

BRUCE BABBITT, Secretary

U.S. GEOLOGICAL SURVEY 

GORDON P. EATON, Director

For sale by

U.S. Geological Survey, Information Services

Box 25286, Federal Center

Denver, CO 80225

Any use of trade, product, or firm names in this publication is for descriptive purposes only and does 

not imply endorsement by the U.S. Government

Edited by George A. Havach and Mary Lou Callas

Graphics by Norman G. Banks, Bobbie Myers, and Barbara Bernegger

Layout by Mary Lou Callas

Library of Congress Cataloging-in-Publication Data

Banks, Norman G.

Direct temperature measurements of deposits, Mount St. Helens, Washington, 1980-1981 / by Norman G. 

Banks and Richard P. Hoblitt.

p. cm. (U.S. Geological Survey professional paper : 1387

Includes bibliographic references.

Supt. of Docs, no.: I 19.16:1387

1. Volcanic ash, tuff, etc. Washington (State) Saint Helens, Mount Temperature. 2. Geology 

Washington (State) Saint Helens, Mount. I. Hoblitt, Richard P. II. Title. Ill Series. 

QE461.B273 1994

552'.23 dc20 93-14067

CIP
CONTENTS

Page

Abstract - 1

Introduction - 1

Acknowledgments 2

Previous temperature studies on pyroclastic-flow deposits 2

Methods 3

Evolution of the equipment and techniques 4

Eruptive history and stratigraphy 4

Temperature of the deposits 10

Debris avalanche of May 18, 1980 ~ 10

Blast of May 18, 1980 12

Pyroclastic-flow deposits of May 18, 1980 19

Pyroclastic-flow deposits of May 25, 1980 22

Pyroclastic-flow deposits of June 12, 1980 22

Pyroclastic-flow deposits of July 22, 1980 26

Pyroclastic-flow deposits of August 7, 1980 29

Pyroclastic-flow deposits of October 17, 1980 29

Other temperature data - 31

Summary and discussion 33

General 33

Important features of temperature data from pyroclastic-flow deposits produced by the blast of

May 18, 1980 33

Summary and discussion Continued 

General Continued

Important features of temperature data from postblast pumiceous pyroclastic-flow deposits of 

May 18, May 25, June 12, July 22, August 7, 

and October 17,1980 

References cited - - -

Appendix 1. Temperature measurement techniques, Mount

St. Helens, 1980 

Instrumentation and technique - 

The first days 

Pipe stations -

Problems with pipe station -

Other equipment - -

Time-efficient equipment and techniques -

Experimental methods -

Aerially emplaced thermocouple probes -

Ceramic paints -

Suggested procedures for future investigations -

Appendix 2. Mount St. Helens temperature data; tables

and plots -

Page

35

36

38

38

38

38

38

38

41

41

41

42

42

45

ILLUSTRATIONS

Page

FIGURE 1. Temperature-depth profiles measured in deposits of the blast of May 18 3 

2. Sketch map of Mount St. Helens area, showing generalized geography and products of May 18 eruption 5 

3 Map of Mount St. Helens area, showing products of the May 18 eruption and temperature stations on deposits of debris

avalanche and blast 6 

4. Generalized strati graphic section through deposit of the blast of May 18 8 

5-11. Photographs of:

5. Cross section through deposit of the blast of May 18, 13.5 km N. 37° W. of Mount St. Helens 8

6. Plane-parallel and dune-form features of surgelike unit in deposit of the blast of May 18, 4.4 km N. 33° W. of

Mount St. Helens - - 8

7. Cross section through deposit of the blast of May 18, 16.9 km N. 2° W. of Mount St. Helens 9

8. Temperature station 11 on flat ponded pyroclastic-flow deposit of the blast of May 18 10

9. Cross section through deposits of May 18, 6.9 km N. 40° E. of Mount St. Helens 11

10. Modification of pumiceous pyroclastic-flow deposits of May 18 eruption by phreatic explosions 11

11. July 22 eruption column 12

12. Sketch map of Mount St. Helens area, showing locations of stations and emplacement temperatures of deposits of debris

avalanche of May 18 - 12

13. Downflow temperature variation of deposits of debris avalanche of May 18 14

14. Sketch map of Mount St. Helens area, showing temperatures of deposits of the blast of May 18 15

15. Plot of emplacement temperatures of deposits of the blast of May 18 versus distance and azimuth of stations from vent - 18

16. Sketch map of Mount St. Helens area, showing distribution and temperatures of deposits of pumiceous pyroclastic flows

of May 18 20

17. Plots of temperatures of deposits of pumiceous pyroclastic flows of 1980 versus distance from vent 21

18. Sketch map of Mount St. Helens area, showing distribution and minimum temperatures of deposits of pumiceous pyroclastic flows of May 25 - 23

19. Sketch map of Mount St. Helens area, showing distribution and temperatures of deposits of pumiceous pyroclastic flows

of June 12 - - - 24

20. Composite thermal profile of deposits of pyroclastic flows of June 12 26

21. Thermal stratigraphy in pumiceous pyroclastic flows of 1980 - - 26

III
IV CONTENTS

Page

22. Sketch map of Mount St. Helens area, showing distribution and temperatures of deposits of pumiceous pyroclastic flows

of July 22 ...... .............................. . . 27

23. Sketch map of Mount St. Helens area, showing distribution and emplacement temperatures of deposits of pumiceous pyroclastic flow of August 7 30

24. Photograph showing installation of temperature station on vent rampart of August 7 eruption 31

25. Sketch map of Mount St. Helens area, showing distribution and temperatures of deposits of pumiceous pyroclastic flows

of October 17 ------------------------------------------------------------------------------------------------------------------ 32

26. Photographs and sketches of temperature-sensing equipment used in this study 39

27. Plot of time required for thermal equilibrium to be reestablished between a pyroclastic-flow deposit and an implanted

pipe and a thermocouple inserted directly into deposit 40

28. Comparisons of temperature-depth profiles 40

29. Photographs of air-dropped, radio-linked thermocouple probes 42

30. Photograph of approach to distal ponded deposits of pyroclastic flow of June 12 43 

31-37. Temperature-depth profiles (part of appendix 2) of deposits of:

31. Blast of May 18 ----------------------------------------------.-----------------------------------.....-.--......---- 64

32. Pumiceous pyroclastic flows of May 18 69

33. Pumiceous pyroclastic flows of May 25 70

34. Pumiceous pyroclastic flows of June 12 71

35. Pumiceous pyroclastic flows of July 22 73

36. Pumiceous pyroclastic flow of August 7 75

37. Pumiceous pyroclastic flows of October 17 76

TABLES

Page

TABLE 1. Generalized chronology and stratigraphy of Mount St. Helens deposits, 1980 8

2. Summary of temperature measurements of Mount St. Helens deposits, May 18-October 17, 1980 13

3. Temperatures of deposits of the debris avalanche of May 18, 1980 14

4. Temperatures of deposits of the blast of May 18, 1980 16

5. Temperatures of deposits of the pumiceous pyroclastic flows of May 18, 1980 19

6. Minimum temperatures of deposits of the pumiceous pyroclastic flows of May 25, 1980 22 

7-10. Temperatures of deposits of the pumiceous pyroclastic flows of:

' 7. June 12, 1980 25

8. July 22, 1980 - ------------- - - - - 28

9. August 7, 1980 ------------------------------------------------------------------------------ 29

10. October 17, 1980 -------------------------------------------------------------------------- 31

11. Basic equipment for temperature measurements in pyroclastic-flow deposits 44
DIRECT TEMPERATURE MEASUREMENTS OF DEPOSITS, 

MOUNT ST. HELENS, WASHINGTON, 1980-1981

By NORMAN G. BANKS and RICHARD P. HOBUTT

ABSTRACT

A program of temperature studies of the eruptive products of Mount St. 

Helens was established May 20, 1980, 2 days after the catastrophic eruption 

of May 18. Temperature-depth profiles were measured by thermocouple to 

determine the emplacement temperatures of deposits of the debris avalanche 

and blast of May 18 and of deposits of the pyroclastic flows of May 18, May 

25, June 12, July 22, August 7, and October 17, 1980.

At some of the localities where deposits had cooled appreciably before 

measurement, emplacement temperatures were recovered mathematically from 

data gathered from observations of the cooling histories of the deposits. In 

addition, methodologies and specialized temperature-measuring equipment 

were developed to maximize efficiency in data collection and to minimize risk 

to personnel.

In general, the more recent eruptive deposits were emplaced at higher temperatures than the earlier ones. Emplacement temperatures of deposits of the 

debris avalanche ranged from about 70 to 100°C. Temperatures of deposits of 

the blast ranged from about 100 to 325°C and varied with the azimuth of the 

measurement site from the vent; the higher temperatures were measured in the 

northeast sector. Emplacement temperatures of the later pumiceous pyroclastic-flow deposits ranged from about 300 to 680°C, and temperatures in nearvent facies were about 750 to 850°C.

The most important features shown by the data obtained from the deposits 

produced by the blast are (1) their generally lower temperature relative to deposits emplaced by the subsequent pumiceous pyroclastic flows, attributed to 

relatively low temperatures of the cryptodome and admixing of significant 

amounts of accidental material and air; (2) an azimuthal variation of emplacement temperatures, hotter toward the east, attributed to thermal inhomogeneities 

in the source material and differential cooling associated with differing grain 

sizes and terrains over which the blast traveled; (3) emplacement temperatures that exhibited little change with distance from the vent to distances as 

great as 20 km, attributed to little cooling along the path, preferential elutriation 

of the cooler, finer particles, preferential interaction between air and the blast 

material at the head of the flow, and production of heat during the flow, possibly by friction; (4) thermal stratigraphy observed in some of the ponded pyroclastic-flow deposits in major valleys, attributed in part to a grain-size effect 

(finer upward) and in part to longer residence of the younger deposits as veneer deposits on the adjacent ridges before their secondary mobilization into 

the valleys; and (5) temperatures in the veneer deposits and moving blast cloud 

that were possibly higher than emplacement temperatures of the ponded pyroclastic-flow deposits.

The most important features shown by the data obtained from the postblast, 

pumiceous pyroclastic-flow deposits are (1) generally hotter deposits in the 

later eruptions than in the earlier ones, attributed to less admixing of the pyroclastic material with air because of the observed progressive decrease in vigor 

of the successive eruptions; (2) little heat loss (100-200°C) of near-vent material 

during eruption, as predicted by simple adiabatic expansion; (3) little downflow 

cooling in the deposits after the first several hundred meters of travel, attribPublication authorized by the Director of the U.S. Geological Survey on March 13,1984.

uted to the same factors proposed for the blast deposits; (4) multiple flow 

units that were emplaced at different temperatures by most of the eruptions, 

attributed to differential cooling through differing amounts of admixed air in 

accordance with the vigor of the individual eruptive pulses; and (5) cooler 

material in the ash-cloud deposits than in the source pyroclastic flows because 

of more effective cooling of the elutriated finer material by the admixed air.

Descriptions of the materials and methods we used, and the tabular data 

and temperature-depth profiles that support our findings, are included as appendices.

INTRODUCTION

Temperature studies of the 1980 eruptive products of 

Mount St. Helens began 2 days after the paroxysmal eruption 

of May 18, 1980, and they continued into 1981. The objective 

of these studies was to establish emplacement temperatures 

across and along the paths of flow of pyroclastic deposits to 

provide data that might aid (1) interpretation of the mechanics 

of transportation and deposition of pyroclastic flows; (2) construction of predictive models of the eruptions of Mount St. 

Helens and similar volcanoes; (3) parallel studies of the deposits, such as the nature of welding, devitrification, vapor-phase 

crystallization, and development of thermal remanent magnetism; and (4) evaluation of indirect methods of obtaining temperatures in pyroclastic deposits, such as infrared absorption, 

thermal-infrared spectroscopy, thermal effects on buried wood 

fragments, and magnetic methods.

Emplacement temperatures were determined for deposits 

of the debris avalanche, of the blast of May 18, and of the pumiceous pyroclastic flows of May 18, June 12, July 22, August 

7, and October 17, 1980. Emplacement temperatures were not 

obtained for deposits of the pyroclastic flows of May 25.

Emplacement temperatures were considered to be established if a reasonable length of the temperature-depth profile 

was isothermal. If the original temperature-depth profile was 

parabolic, we labeled the maximum temperature on the curve 

as the minimum temperature for the deposit.

We gained confidence that the isothermal segments of 

profiles did, indeed, indicate emplacement temperatures by 

obtaining similar profiles from adjacent sites and from later, 

repeated measurements at the same site during the following 

days and months. Rarely, we labeled a single temperature 

measurement as an emplacement temperature if the single
DIRECT TEMPERATURE MEASUREMENTS OF DEPOSITS, MOUNT ST. HELENS, WASHINGTON, 1980-1981

temperature measurement fit the plot of an isothermal profile 

segment obtained in the deposit at a nearby site or at the same 

site on a later date.

Companion studies included (1) estimation of the emplacement temperatures of deposits by study of the thermal effect on included wood (Banks and Cutter, 1981; Banks and 

Hoblitt, 1981a, b), (2) indirect methods of estimating the temperature regime within moving flows by study of the thermal 

effects on plastics and standing trees (Davis and others, 1980; 

Hoblitt and others, 1980; Banks and Cutter, 1981; Banks and 

Hoblitt, 198Ib; Winner and Casadevall, 1981), and (3) calculation of in-place thermal properties and mathematical recovery 

of the emplacement temperatures of pyroclastic-flow deposits 

from data obtained by repeated measurement of the profiles 

(Hardee, 1981; Ryan and others, 1981, 1990).

Our study also included the development of experimental 

techniques of temperature measurement, such as aerially 

emplaced thermocouple probes that telemetered data to a hovering helicopter and the use of temperature-sensitive paints to 

directly determine temperatures in glowing cracks and in moving ash clouds.

ACKNOWLEDGMENTS

This study would have been virtually impossible without 

the skillful, courageous efforts of the helicopter pilots who 

shuttled us from place to place under conditions that sometimes 

were hazardous and always were punishing to their ships. The 

pilots with whom we worked most closely were Mike Holtsclaw, 

Lon Stickney, Michael Montgomery, and Robert Brown. In our 

labors in the field and the laboratory, we were assisted by many 

other workers, principally Terry Leighley, James Vallance, Bruce 

Furukawa, C.D. Miller, Joseph Rosenbaum, Christine Hannah, 

T.A. Duggan, Paul Greenland, Dallas Jackson, Michael Doukas, 

M.L. Summers, Peter Rowley, Edward Graeber, Lisa 

McBroome, and Herman Hoffschneider. This report is dedicated 

to David A. Johnston, our friend and colleague who lost his life 

on May 18, 1980, while studying Mount St. Helens. Our science suffers from his untimely death.

PREVIOUS TEMPERATURE STUDIES ON 

PYROCLASTIC-FLOW DEPOSITS

Few temperatures have been measured in pyroclastic-flow 

deposits of stratovolcanoes, owing to inaccessibility, long repose times, considerations of safety, and absence of appropriate equipment. The most comprehensive temperature studies 

were those by Griggs (1918), Sayre and Hagelbarger (1919), 

Alien and Zies (1923), and Zies (1924, 1929) in the Valley of 

Ten Thousand Smokes, Alaska; by Kozu (1934) on deposits of 

the 1929 Komagatake, Japan, eruption; and by Johnston (1978) 

and Kienle and Swanson (1980) on deposits of the 1976 eruption of Augustine Volcano, Alaska. These studies reported temperatures of 100 to 645°C in ash-flow deposits and in fumaroles rooted in them. Some studies also described the cooling 

histories of the deposits and fumaroles; however, none directly 

established the emplacement temperatures of deposits or the 

temperature distribution across and down flow paths.

Some additional data were reported by Gorshkov and 

Dubik (1970, p. 278), who measured temperatures of 250 to 

300°C at a depth of 30 cm in andesitic pyroclastic-flow deposits 10 days after their eruption in 1964 from Sheveluch Volcano, Kamchatka, Siberia. They also measured temperatures of 

400°C in fumaroles rooted in the deposits and (without citing 

the depths to which they probed or the details of the assessment) observed that these deposits were cold within 10 days of 

the eruption. Gorshkov (1959, p. 95) measured temperatures 

(100-200°C) in fumaroles in the deposits of the directed blast 

of Bezymianny Volcano, Kamchatka, 7 or 8 months after the 

eruption; and some more recent data for Bezymianny and 

Sheveluch Volcanoes were reported by Borisov (1960), Tokarev 

and Borisov (1961), Borisov and Nikitina (1962), Markhinin 

and others (1963), Dubik and Meniailov (1969), Kirsanov and 

others (1971), and Kirsanov (1979). On the basis of cooling 

curves of the fumaroles, Lovering (1957) estimated that the 1912 

deposit in the Valley of Ten Thousand Smokes was emplaced at 

temperatures higher than 800°C.

Temperatures of pyroclastic-flow deposits have also been 

inferred indirectly from the optical properties of ash flows, from 

the thermal effects on manufactured and biologic articles incorporated by or in the paths of ash flows, from magnetic studies, and from theoretical considerations. Macdonald and Alcaraz 

(1956, p. 173) estimated the temperature of an ash-flow deposit 

of December 6, 1951, of Hibok-Hibok in the Philippines to be 

higher than 700°C on the basis of the color and intensity of 

incandescence of the flowing mass. The ash flows from Mont 

Pelee that destroyed St. Pierre, Martinique, in 1902 were below 

the melting point of copper (1,058°C) but above the melting 

point of glass (650-700°C) (Cotton, 1952, p. 200). Van 

Bemmelen (1949, p. 192) judged that pyroclastic flows in Indonesia issued at 800 to 1,000°C (a deduction based on the temperature of the lava) and arrived at the base of the cones at 400 

to 450°C (based on the fact that bamboo huts were not generally set on fire by the distal ends of flows). Taylor's (1958) 

study of plastics and other articles exposed to the flows of the 

paroxysmal eruption of Lamington, Papua New Guinea, suggested flow temperatures of about 200°C. Maury and others 

(1973) and Mimura and others (1975) used infrared absorption 

analysis to determine the temperature (200^50°C) at which 

wood had become carbonized in various pyroclastic-flow deposits in Japan. Aramaki and Akimoto (1957), Suzuki (1962), 

and Hoblitt and Kellogg (1979), who inferred temperatures of 

100 to 550°C for prehistoric ash deposits at Mount St. Helens, 

used magnetic techniques to suggest emplacement temperatures. 

From theoretical considerations and experimental petrology, 

Gilbert (1938) estimated the emplacement temperature of the
METHODS

welded Bishop Tuff in eastern California at 750 to 800°C. Day 

and Alien (1925) found that Mount Lassen dacite softens at 

850°C, is fluid at 1,050°C and is molten at 1,260°C. Smith and 

others (1958) showed that dry welding of glass shards occurs at 

about 750°C and as low as 535°C in the presence of gases, and 

Smith (1963) estimated that welding occurs at temperatures that 

range from about 500°C in very thick deposits to about 1,000°C 

in thin deposits.

Petrologic parameters have been used to estimate temperatures of the magma erupted to form pyroclastic flows (for 

example, Johnston, 1978; Melson and others, 1980; Melson and 

Hopson, 1981), as have temperatures measured in lava flows 

and lava domes before and after ash eruptions. Domes of andesite 

at Merapi Volcano, Indonesia, were reported to have temperatures of 850 to 950°C (van Bemmelen, 1949, p. 197-198), and 

Stehn (1936) reported temperatures of about 800 to 850°C in 

cracks in Merapi domes. Temperatures in fumaroles in the craters of various other Indonesian volcanoes were reported by 

Neumann van Padang (1963) to be as high as 700°C; D.A. 

Johnston (in Kienle and Swanson, 1980) measured a temperature of 754°C in the 1976 dome of Augustine Volcano 3 years 

after it was emplaced; and temperatures as high as 750°C were 

"measured on Bezymianny domes by Dubik and Meniailov 

(1969), Kirsanov and others (1971), and Kirsanov (1979).

Both the direct and indirect temperature studies suggest 

that emplacement temperatures of pyroclastic flows of intermediate and acidic composition range from less than 500°C to 

nearly 1,000°C. Smith (1963) attributed this wide variation in 

emplacement temperatures to cooling of ejecta in a vertical eruption column rather than to profound differences in magmatic 

temperatures. Our data agree with Smith's assessment, and, in 

addition, they indicate that cooling which takes place during 

movement, and particularly during development, of flows is also 

important.

METHODS

Ideally, emplacement temperatures of pyroclastic deposits should be established by measurement immediately after 

emplacement of the flow. This usually was not practical or possible, particularly during the early stages of our study. Therefore, wherever possible, we obtained temperature-depth profiles and considered that we had determined emplacement 

temperatures when isothermal segments were observed in a profile. As noted above, measurement of profiles from adjacent 

sites and later repeated measurements of the same profiles during the following days and months added confidence that the 

isothermal segments of the profiles actually indicated the emplacement temperatures of the deposits (fig. 1). By subsequent 

profiling at the same sites, we also were able to establish that 

some of our single measurements, which were made soon 

enough after deposition in thin deposits or at depths of 1 to 30

m in thicker deposits, approached or had actually recorded the 

temperatures of emplacement.

Temperatures were measured with Chromel-Alumel and 

Pt-Pt-Rh thermocouples and direct-reading, electronically compensated (cold-junction) digital thermocouple meters. The thermocouples were inserted either directly into the deposits or into 

pipes that had previously been implanted and allowed to thermally equilibrate with the deposits.

The thermocouples and thermocouple meters were periodically checked against the melting point of ice during fieldwork. In addition, periodic checks were made on the internal 

consistency of the field data by measuring temperatures on one 

thermocouple (thermally equilibrated with the deposit) with 

from two to five digital meters from three manufacturers. Other 

tests involved measuring temperatures on several adjacent (2- 

to 3-m separation) thermocouples (of two types) implanted simultaneously to the same depth.

These field tests indicated that the field measurements 

were internally consistent to 2°C or better. Later, two of the 

meters and some of the thermocouples that were used in the

CO

DC 

LLJ

LLJ

? 3

50 100 150 

TEMPERATURE, IN DEGREES CELSIUS

200

FIGURE 1. Temperature-depth profiles measured in deposits of the Mount St. 

Helens blast of May 18 at two sites in the same locality (curves A and B) 

and at a nearby locality (curve C). Curve A, 4 days after emplacement; 

curve B, 16 days after emplacement; curve C, 6 days after emplacement.
DIRECT TEMPERATURE MEASUREMENTS OF DEPOSITS, MOUNT ST. HELENS, WASHINGTON, 1980-1981

field were checked in furnaces and against precision voltmeters 

in the laboratory. As was the case in the field tests, the laboratory tests indicated that the temperatures reported here do not 

deviate more than 2°C from actual values over the temperature 

range measured at Mount St. Helens (20-840°C).

EVOLUTION OF THE EQUIPMENT AND TECHNIQUES

The large area devastated by the blast (more than 600 km2) 

and limited initial access made it impossible to obtain a wide 

distribution of temperature sites before the deposits, particularly the thin unponded deposits, had cooled below levels adequate for satisfactory recovery of temperatures by mathematical extrapolation. The delays of access resulted from poor 

weather, limited helicopter support, and considerations of safety. 

In addition, in our early studies, we lacked appropriate equipment and experience with freshly deposited pyroclastic-flow 

material.

We believe that many of these early frustrations and gaps 

in our study would have been greatly minimized if published 

descriptions had been available that detailed the techniques 

needed and the problems inherent in temperature investigations 

of pyroclastic-flow deposits. Thus, for the benefit of readers 

with such interests, we include Appendix 1, which summarizes the instrumentation that we initially used, the problems 

that beset our studies as they evolved, and the techniques and 

equipment that eventually yielded the best data in the safest, 

most efficient manner. For the readers who wish to do additional modeling of the temperature data or to apply it to related 

studies such as magnetostratigraphy, vapor phase mineralization, and thermal effects on wood, we include all the data that 

we gathered in both tabular and graphical form (temperature-depth profiles, figs. 31-37) in appendix 2.

ERUPTIVE HISTORY AND STRATIGRAPHY

The 1980 eruptions at Mount St. Helens and the resultant 

stratigraphy are described in detail elsewhere (Lipman and 

Mullineaux, 1981). However, for those unfamiliar with the details, an outline is presented here so that our temperature data 

may be viewed in their proper context of map distribution (figs. 

2, 3), and chronologic occurrence (table 1).

The first sign that eruptive activity might recur at Mount 

St. Helens after 123 years of quiescence was a magnitude 

(M)=4+ earthquake beneath the summit at 1547 P.s.t. 1 March 

20, 1980. Earthquake activity continued, fluctuating between 

numerous isolated earthquakes and swarms that saturated the

1 Times are local times expressed on a 24-hr scale. P.s.t., Pacific Standard Time (Universal 

Time less 8 hr); P.d.s.t., Pacific Daylight Saving Time (Universal Time less 7 hr) from April 27 

through October 25, 1980.

seismometers. Many of these earthquakes were of M>4. Phreatic 

eruptions began at 1236 P.s.t. March 27. The preblast eruptions 

began at a relatively high level, followed by an overall decline 

in frequency and magnitude; there were brief cessations between 

April 22 and May 7 and in mid-May. Significant deformation 

high on the north flank of the mountain was visually obvious 

by late March, and harmonic tremor was first noted April 1. 

Deformation networks established in late April and early May 

indicated that an area about 2 km2 on the north flank of the 

mountain was being destabilized by lateral movement (with a 

minimal vertical component) northwestward at the remarkable 

rate of 1.5 to 2.5 m/d (Lipman and others, 198la).

At 0832 P.d.s.t. May 18, an M>5 earthquake mobilized 

the oversteepened north flank of the mountain and initiated a 

catastrophic debris avalanche consisting of 2.5 to 2.7 km3 of 

the north flank of the mountain (table 1; Voight and others, 1981). 

The debris flow traveled locally faster than 200 km/h (Voight 

and others, 1981) as a dry to moist hot fragmental mass that 

moved 27 km down the North Fork of the Toutle River and 

crossed over South Coldwater Ridge at two places (400-m relief, 8 km north of the mountain; figs. 2, 3). One lobe of the 

flow traversed the length of the west arm and part of the east 

arm of Spirit Lake, raising its water level about 60 m. Water 

from Spirit Lake, the Toutle River, melting snow and ice, and, 

possibly, ground water from the disrupted slopes of the volcano 

generated mudflows of various ages relative to the debris flow 

and later events. Mudflows traveled as much as 90 km down 

the North and South Forks of the Toutle River into the Cowlitz 

River about 55 km to the west and, finally, into the Columbia 

River; some mudflows originating on the south and east flanks 

of the mountain moved southeast as far as Swift Reservoir, a 

distance of 28 km.

While the debris flow was still in motion, probably within 

30 s of its initiation, a northward-directed explosive eruption 

emerged from the scarp left by the departing avalanche (Moore 

and Albee, 1981; Voight, 1981). The blast or hurricanelike eruptive cloud traveled at speeds locally faster than 400 km/h and 

devastated about 600 km2 of land in a 155° arc to the north of 

the mountain (figs. 2, 3; Moore and Albee, 1981; Moore and 

Sisson, 1981; Rosenbaum and Waitt, 1981). At leasts half (0.1 

km3 ) of the pyroclastic-flow deposit consisted of gray, varyingly vesiculated, hornblende-hypersthene dacite that is essentially identical in chemical composition to dacite in the later 

pumiceous pyroclastic eruptions (Hoblitt and others, 1981; 

Lipman and others, 1981b; Moore and Sisson, 1981; Waitt, 

1981).

The deposit of the blast can be described in terms of a 

veneer deposit with fourfold stratigraphy plus a pyroclastic-flow 

deposit (fig. 4; table 1; Hoblitt and others, 1981), although some 

workers prefer to combine the lowermost two units because of 

their gradational nature (Moore and Sisson, 1981; Waitt, 1981). 

Each of the units may be locally absent.

The basal unit of the veneer deposit consists predominantly of fragmental and shredded wood (near field, fig. 5) or
METHODS

fir and pine needles (far field) in a matrix of friable, silt- to cobble-size 

juvenile dacite and accidental lithic material (of local and distant origin). The basal unit grades upward into a massive unit that, almost 

everywhere in the inner 10 to 15 km, is a poorly sorted and generally 

ungraded, matrix-supported deposit containing varying amounts of lapilli 

and blocks of the juvenile dacite and accidental lithic clasts. Contact 

with the next higher unit, a sorted, graded, stratified, and cross-stratified surgelike unit (fig. 6), is either sharp or gradational. This surgelike 

deposit, which constitutes progressively more of the section in the outer 

15 to 28 km of the devastated area (compare figs. 5 and 7), probably 

was deposited from the ash or elutriation cloud of the blast. The fourth 

unit of the veneer deposit is fine to coarse ash, most commonly containing one or more layers of accretionary lapilli. In low-lying localities, ponded, rootless pyroclastic-flow deposits (fig. 8) lie between the 

surgelike and accretionary-lapilli units of the veneer deposits. These 

unstratified, unsorted, generally ungraded, matrix-supported deposits 

are much like the massive unit of the veneer deposits. Concentrations

of logs and wood fragments commonly occur near or on the tops of the 

ponded deposits.

Some of the ponded pyroclastic-flow deposits probably were 

primary (for example, adjacent to the mountain on the west and in 

some of the far-field drainages), and some were secondary deposits 

formed by immediate remobilization of the hot inflated ash momentarily deposited on the steep flanks of drainages. The ponded deposits 

formed before the accretionary-lapilli layer was deposited (Hoblitt and 

others, 1981). All but one of our temperature measurements in deposits 

of the blast were in the ponded pyroclastic-flow deposits

Eyewitness accounts indicate that the blast moved as a groundhugging mass. Some eyewitnesses also report that a westward directed 

lobe may have slightly preceded a northward- and eastward-directed 

lobe (Rosenbaum and Waitt, 1981); however, neither stratigraphic and 

lithologic studies (Hoblitt and others, 1981; Moore and Sisson, 1981; 

Waitt, 1981) nor satellite imagery (Moore and Rice, 1984) supports 

multiple emission events.

R.2E. 122°30' R. 3E. 122°22'30" R. 4E. 122°15' R. 5E. 122°07'30" R. 6E. 122°00' R. 7E.

EXPLANATION

Lava dome

Approximate limit of searing 

and weak blast effects south 

of crater of May 18

Pyroclastic-flow deposits 

Mudflow deposits and scoured areas 

Seared zone of blast deposits 

Devastated zone of blast deposits 

Debris-avalanche deposits 

Pre-1980 deposits

Collapsed summil 

rim Hachures point 

downslope in crater 

formed May 18

FIGURE 2. Sketch map of Mount St. Helens area, Washington, showing generalized geography and products of May 18 eruption. Modified from Luedke and others (1980).
DIRECT TEMPERATURE MEASUREMENTS OF DEPOSITS, MOUNT ST. HELENS, WASHINGTON, 1980-1981

122°30' 122°22'30"

EXPLANATION

May 18 to October 18, 1980, 

pumiceous pyroclasticflow deposits

Blast area above tree line

showing very little effect 46' 

from blast 22 30'

38883&$& Seared zone of blast deposits

Ponded pyroclastic-flow 

deposits of blast

DA1

20

Deposits of debris avalanche

Slopes of Mount St. Helens 

above treeline Area 

shows little effect from 

1980 eruptions except for 

blanket of air-fall deposits

Forested slopes of Mount St. 

Helens Area shows little 

effect from 1980 eruptions 

except for blanket of airfall deposits and mudflows 

along stream beds

-? Contact Dashed where 

approximately located; 

dotted where underwater; 

queried where unknown

Rim of crator formed May 

18 Hachures point 

downslope

Debris avalanche 

station See table 3

Blast station See table 4

FIGURE 3. Generalized map of 

Mount St. Helens area, 

showing products of the May 

18 eruption and temperature 

stations on deposits of debris 

avalanche and blast. Modified 

from Lipman and Mullineaux 

(1981). Note overlap between 

pages.

122°30'

Base from U.S. Geological Survey 

Mount St. Helens and vicinity, 

Wash-Oreg, June 1980

Universal Transverse Mercator Projection

122°22'30"

4 MILES

4 KILOMETERS

AREA OF MAP
METHODS

122°15' 122°07'30" 122°00'

46° 

22' 

30"

46° 

30"

122° 15' 122°07'30" 122°00'
DIRECT TEMPERATURE MEASUREMENTS OF DEPOSITS, MOUNT ST. HELENS, WASHINGTON, 1980-1981

TABLE 1. Generalized chronology and stratigraphy of Mount St. Helens 

deposits, 1980

Date

Mar. 27-May 18 

May 18

May 18 25

May 25

June 12 13

July 22 - 

Oct. 17

Time (P.d.s.t.)

0832

-0833

-0835 1930

0232

1905-0200

1825

1901

1623

nnoo

2112

Deposit type

Phreatic eruptions, mudflows.

Debris avalanche, mudflows.

Blast deposits.

Pumiceous pyroclastic flows, at

least 17 events.

Phreatic eruptions, mudflows.

Pumiceous pyroclastic flows.

Pumiceous pyroclastic flows.

Pumiceous pyroclastic flow.

Do. 1

Do. 1

Do. 1

Do. 1

Not including small-volume pyroclastic flows restricted to crater and 

upper part of amphitheater.

Well-sorted fine ash containing 

accretionary lapilli

Pyroclastic flow unit, matrix-supported, 

unstratified and generally ungraded, 

containing dacite lapilli, lithic clasts, 

and ash

Surgelike unit, stratified, cross-stratified, 

sorted to well-sorted, containing dacite 

lapilli, lithic clasts, and ash

Massive unit, generally unstratified, commonly ungraded and unsorted, containing dacite lapilli and blocks, lithic 

clasts, and ash

Basal unit, containing dacite blocks and 

lapilli, lithic clasts, and varying 

amounts of ash and organic debris

FIGURE 4. Generalized stratigraphic section through deposit of the Mount 

St. Helens blast of May 18.

FIGURE 5. Cross section through deposit of the blast of May 18, 13.5 km 

N. 37° W. of Mount St. Helens.

FIGURE 6. Plane-parallel and dune-form features of surgelike unit in 

deposit of the blast of May 18, 4.4 km N. 33° W. of Mount St. Helens.
METHODS

In the near field, north and northeast of the volcano, the 

presence of a beadlike layer of vesiculated tan and denser gray 

lapilli of hornblende-hypersthene dacite under the accretionary-lapilli unit indicates that the Plinian eruption developed very 

soon after the blast of the cryptodome (gray dacite) (fig. 9).

Continuing Plinian eruption of the tan pumice to heights 

of 20 km above the crater during the next 8 to 9 hours generated 

in the far field a tephra and ash blanket that extended 

northeastward of the volcano beyond the east Washington State 

line. In the near field, many pyroclastic flows (fig. 2) formed 

spotty and thin deposits in the amphitheater area north of the 

main crater and formed deposits with an aggregate thickness of 

as much as 50 m and a volume of 0.12 km3 in the Toutle River 

drainage and on the lower north flank of the volcano (Rowley 

and others, 1981). These deposits consist of tan, highly vesiculated pumice blocks and lapilli in a crystal and ash-shard matrix. They were more voluminous than any of the subsequent 

pyroclastic-flow deposits of 1980.

Minor phreatic eruptions continued in the vent area with 

decreasing frequency and intensity until the next magmatic erupJ» ^:- 

a

FIGURE 7. Cross section through deposit of the blast of May 18, 16.9 km 

N. 2° W. of Mount St. Helens.

tion on May 25 (table 1). Phreatic eruptions also occurred at the 

north foot of the mountain (fig. 10A; Christiansen and Peterson, 

1981; Rowley and others, 1981). These eruptions were rooted 

in deposits of the debris avalanche underlying the May 18 pyroclastic-flow deposits and produced surge deposits through 

column collapse (figs. 105, C).

The May 25 eruption produced three small (0.001 km3 ; 

Rowley and others, 1981) rootless pyroclastic-flow deposits. 

Two of these deposits were on the north flank of the volcano 

(subsequently buried or eroded away), and one is on the northeast flank (Rowley and others, 1981). A light dusting of tephra 

and ash accumulated south and west of the mountain from an 

eruptive cloud that rose 12 km over the summit. The tephra and 

ash-flow deposits contained both vesiculated tan and denser gray 

dacite, and the flow deposits had a much higher clast-to-matrix 

ratio than the May 18 deposits. As in the case of the May 18 

eruption, deposits in the amphitheater area north of the main 

crater area were spotty and thin.

Minor phreatic eruptions continued to issue from the vent 

through June 4, and on June 12 a brief eruption at 1905 P.d.s.t. 

was followed by a larger one that at 2111 P.d.s.t. sent an eruptive column 16 km above the summit. Other eruptive columns 

of lesser intensity formed until 0200 P.d.s.t. the next morning. 

The volume (0.02 km3 ; Rowley and others, 1981) of the pumiceous pyroclastic material deposited by the June 12 eruption is 

second only to that of the May 18 eruption. The flows, consisting of pumice blocks and lapilli of both tan and gray dacite, 

traveled as far as 7 km north of the vent and, in many places, 

left only a lag deposit of large dense blocks of gray dacite. The 

flow deposits were matrix supported, and some ponded to depths 

of more than 20 m in phreatic pits formed in the May 18 deposits (see figs. 29A, 30).

A lava dome was emplaced in the summit crater during 

or soon after the June eruption. This dome was partly blown 

away in the eruption of July 22, which produced, during two of 

three major events, a Plinian column (fig. 11)18 km above the 

crater and matrix-supported pyroclastic-flow deposits containing both gray and tan dacite blocks and lapilli. The flow deposits were smaller in volume (0.006 km3 ; Rowley and others, 1981) 

than the June deposits and were observed during their emplacement, one at about 1825 and a second at about 1901 P.d.s.t. Two 

stratigraphic units are recognizable in the resulting deposits. 

The lower unit is tan, and the upper unit is faint salmon pink. 

The thickness of these flows averaged about 1 to 2 m.

The eruption of August 7 produced a pumiceous pyroclastic flow that formed deposits 1 to 2 m thick during the first 

of three major pulses having column heights of about 12 km. 

These deposits consisted of lapilli to blocks of both gray and 

tan dacite pumice in a shard and crystal matrix, were intermediate in volume (0.004 km3 ; Rowley and others, 1981) between 

those of the July 22 and May 25 eruptions, and, though still 

matrix supported, had a higher clast-to-matrix ratio than all the 

previous flowage deposits except those of May 25. Anew dome 

was emplaced after the August 7 eruption.
10 DIRECT TEMPERATURE MEASUREMENTS OF DEPOSITS, MOUNT ST. HELENS, WASHINGTON, 1980-1981

Five separate eruptive plumes were generated during 

October 16 to 18. Two of these on October 17 produced thin 

(less than 2 m) matrix-supported flow deposits (tables 1, 2), 

and from 10 to 30 m of new pyroclastic material was deposited 

in the crater. The pumice lapilli and blocks of the deposits were 

off-white, and the deposit had a higher matrix-to-clast ratio than 

the August deposits (Rowley and others, 1981). A new dome, 

larger than the June 12 dome, grew from the vent during and, 

for a few days, after this eruption. The October eruption produced the last significant pyroclastic-flow deposits of 1980 at 

Mount St. Helens.

The final and largest dome of 1980, which grew at the 

site of the October dome between December 25 and 30, was 

preceded by several gas-release events that did not involve significant amounts of tephra. Several significant gas events, with 

some remobilization of insignificant amounts of ash, also occurred in July through October 1981.

TEMPERATURE OF THE DEPOSITS

Emplacement temperatures of flow deposits produced by 

Mount St. Helens in 1980 ranged from below 100°C for the

debris avalanche of May 18 to 850°C for some near-vent pyroclastic material. In general, the more recent eruptive deposits 

were emplaced at higher temperatures than the earlier ones. 

These data are summarized in tables 2 through 10 and presented 

in detail in appendix 2.

DEBRIS AVALANCHE OF MAY 18,1980

Temperatures of 68 to 98°C were measured at seven stations on the debris avalanche 6 to 12 days after emplacement of 

the deposit (fig. 12; tables 2, 3). Temperature-depth profiles in 

pipes at two of these stations (DA1, DA6) indicate that the deposit was nearly isothermal about 1 m below the surface and 

isothermal at the boiling point of water at depths below 1.3 to 

1.5 m. Measurements at four other stations (DA2 DA5) were 

obtained by direct insertion of thermocouples at four to seven 

sites over an area of about 1,000 m2 at depths of 1 to 1.5 m. The 

temperatures thus measured varied somewhat, as expected for 

the heterogeneous lithology of the deposit. However, in most 

places, they were closely grouped and are thought to represent 

emplacement or near-emplacement temperatures.

FIGURE 8. Temperature station 11 on flat ponded pyroclastic-flow deposit of the blast of May 18. View eastward.
TEMPERATURE OF THE DEPOSITS 11

Temperatures were measured in the bottoms of freshly 

dug pits in deposits of the debris avalanche at five other localities (9-33°C) by Barry Voight between May 30 and June 3 (written commun., 1980); however, all but one measurement (at sta. 

DA7, table 3) were in pits less than 0.5 m deep. The 0.5-m-deep 

pit was in the flow lobe north of Spirit Lake (inverted triangle, 

fig. 13A), and the temperature measured in it lies well below 

the temperature curve for the North Toutle and South Coldwater 

lobes (fig. 13A). This difference could be attributed to the shallow depth of the measurement, to cooling due to incorporation 

of Spirit Lake water, or to different source areas on the flank of 

the volcano for the different lobes of the debris flow.

The debris avalanche contains a low percentage of juvenile material and consists predominantly of highly altered and 

fractured rocks that composed the north flank of the mountain 

(Voight and others, 1981). Thus, the low temperatures measured 

in the deposit are consistent with its composition. The fractured 

old rock probably had been heated to near-boiling-water temperatures by steam or hot water of the hydrothermal system 

associated with the cryptodome.

Except for that measured at station DA7, the measured 

temperatures generally decrease away from the summit along 

the North Toutle-South Coldwater lobe (fig. 13A). This 

downflow cooling could reflect one or more of the following 

flowage mechanisms: (1) the rocks composing the colder, upper parts of the mountain flank traveled farther than the hotter, 

underlying flank rock (fig. 13B); (2) the flow was multiple and 

fed by progressively deeper (hotter) but less far traveled levels 

of the mountain (fig. 13C); or, less likely, (3) there was significant downflow incorporation of air, water, and debris from the 

riverbed (fig. 13£>).

FIGURE 9. Cross section through deposits of May 18, 6.9 km N. 40° E. of 

Mount St. Helens. A layer of vesiculated tan pumice lapilli occurs between 

surgelike and accretionary-lapilli units of deposit of the blast.

FIGURE 10. Modification of pumiceous pyroclastic-flow deposits of May 18 

eruption by phreatic explosions. A, Secondary phreatic eruption through 

deposits of May 18 that overlie buried North Fork Toutle River. View 

eastward. B, Dunes resulting from base-surge events associated with 

phreatic explosions shown in figure IOA. View southward from station k. 

C, Cross section at station k, showing plane-parallel and cross stratification 

in deposits from base-surge events associated with phreatic explosions 

shown in figure 10/1.
12 DIRECT TEMPERATURE MEASUREMENTS OF DEPOSITS, MOUNT ST. HELENS, WASHINGTON, 1980-1981

FIGURE 11. July 22 eruption column. Ash cloud to left of eruption 

column is from a pyroclastic flow. View eastward.

BLAST OF MAY 18, 1980

Temperatures were measured at 21 stations on the deposits produced by the blast. All but one station (12, figs. 3, 14; 

table 4) were on ponded pyroclastic-flow deposits in topographic 

lows. Data at 12 stations indicate that we were observing emplacement temperatures for at least one site, either directly 

(isothermal profile segments; see fig. 31 and tables in appendix 

2) or indirectly (from mathematical reconstruction). Data from 

another four stations (1, 3, 4, and 6) plotted on isothermal profiles obtained at stations in the same or nearby drainages and, 

for plotting purposes, are listed as estimated emplacement temperatures in table 4.

The emplacement temperatures thus obtained (17 stations) 

for the deposits of the blast range from 96 to 325°C (fig. 14; 

tables 2, 4). We failed to obtain direct data indicative of emplacement temperatures at four stations (8, 12, 16, 17).

122°30'

46° 

22' 

30"

122°22'30" 122°15' 122°07'30" 122°00'

46C 

15'

DA7

46C 

07' 

30"

EXPLANATION

Directed-blast deposits

Seared zone of directed blast

Debris avalanche

Temperature (in °C)

Temperature in bottom of 0.5-m-deep, freshly dug pit

[jDA2 Temperature profile in pipe penetrating debris avalanche deposits below 

blast deposits Open symbol in tongue in North Fork Toutle River

Temperature profile, multiple single measurements by direct insertion of 

thermocouple . ,

'ollapsed summit rim Hachures point 

downslope in crater formed May 18

 Approximate limit of searing 

and weak blast effects south 

of crater of May 18

I T

4 KILOMETERS

FIGURE 12. Sketch map of Mount St. Helens area, Washington, showing locations of stations and emplacement temperatures of deposits of

debris avalanche of May 18.
TEMPERATURE OF THE DEPOSITS 13

TABLE 2. Summary of temperature measurements of Mount St. Helens deposits, May 18-October 17, 1980

[Volumes and velocities from Moore and Albee (1981), Moore and Sisson (1981), Rosenbaum and Waitt (1981), Rowley and oihers (1981), Voight (1981), and Voight and others 

(1981). h, hours; U, upper flow unit; L, lower flow unit. Temperatures: E, measured emplacement; e, estimated emplacement; m, minimum temperature]

Time 

(P.d.s.t.) 

and date

Deposit 

type

Description

Distance

Temperature from 

(°C) vent (km)

Summary of measurements

0832 h, Debris Deposits as much as 120 m thick; heterMay 18. avalanche. ogeneous rockmass composed of north 

flank of volcano; emplaced dry; velocity, >200 km/h; volume, 2.5 km3 .

E68-E98 7.4-25.2 7 stations. Isothermal temperature profiles at 2 

stations; several single temperatures to 1.5-m 

depth at other stations.

May 18 Blast Explosive eruption, five-unit stratigra- m66-E325 3.7-19.3

phy, with 30->60 percent gray dacite 

of cryptodome; local ponded deposits 

as much as 10 m thick; velocity, 

200->400 km/h; area, 600 km2 ; volume, 0.19 km3 .

May 18 Pumiceous Flow deposits mostly north of vent; ash m97-e418 0.7-8.9 

pyroclastic and tan pumice lapilli and blocks, 

flows. thickening downflow: 0-0.3 m thick

0.3-2 km from vent, 1-m-thick with a

few 1- to 5-m-thick ponded deposits 2-

4 km from vent, and as much as 30+ m

thick 4-8 km from vent; fine-grained

ash-cloud deposit 8-20 km NNE of

volcano; volume, >0.12 kms.

May 25 Pumiceous Flow deposits of ash and gray and tan 

pyroclastic banded pumice lapilli and blocks; rootflows, less, <3 m thick; negligible volume.

June 12 Pumiceous Flow deposits of ash and gray and tan 

pyroclastic banded pumice lapilli and blocks; 

flows. generally 1-5 m thick ponded in

phreatic pits in May 18 deposits;

volume, 0.01 km3 .

ml55-ml56 2.7-4.4

E361-E602 4.4-6.9

1825 h, 

1901 h, 

July 22.

1623 h, 

Aug. 7.

0928 h, 

2112 h, 

Oct. 17

Pumiceous Flow deposits of ash and gray and tan 

pyroclastic banded pumice lapilli and blocks; <1- 

2 m thick; volume, 0.006 km3 .

flows.

Pumiceous Flow deposits of ash and gray and tan 

pyroclastic banded pumice lapilli and blocks; <1- 

2 m thick; negligible volume.

U, E640- 4.4-6.4

E688. 

L, E295-

m508.

E640-E850 0.2-5.2

flow.

Pumiceous 

pyroclastic 

flows.

-do- ll, m467-

m849.

L, E460.

One or more sites at 21 stations. Two or three flow 

units in some drainages. Several single measurements to 1.5-m depth at four stations. 22 temperature profiles, 11 isothermal for at least one 

flow unit. Little or no downflow variation but 

significant azimuthal variation in temperature.

13 stations north of vent, one on east flank of volcano. Temperature profiles at 6 stations, each 

isothermal or nearly so. Single temperatures to 

1.5-m depth at 6 stations; 2 stations in the same 

area but separated stratigraphically by 30 m of 

deposits suggest an isothermal section at a 

seventh station. Little crossflow or downflow 

variation in temperature.

Temperature profiles through deposits on two different tongues; curves were already parabolic 

when measured 6 days after the eruption.

13 stations on three tongues. Temperature profiles 

at each station, with isothermal or nearly isothermal segments on each profile, some suggesting two or three flow units (total, four units); 

older units were hotter (approx. 370, 450, 490, 

and 600°C). Little downflow variation in temperature.

7 stations on two tongues. Several temperature profiles at 3 stations 18-22 h after emplacement, and 

at 4 other stations during next 25 days. Lower 

(1825 P.d.s.t.) flow unit emplaced at lower temperature than upper (1901 P.d.s.t.) flow unit. 

Little downflow variation in temperature.

3 stations. Several temperature profiles at each 

station, with one or more isothermal or nearly 

isothermal segments. Highest temperatures in 

near-vent ejecta. Little downflow variation in 

temperature.

0.2-4.3 4 stations. Several temperature profiles at 2 stations. Single temperatures and partial temperature 

profiles at 2 stations. Lower (0928 P.d.s.t.) flow 

unit emplaced at lower temperature than upper 

(2112 P.d.s.t.) flow unit. Highest temperatures in 

near-vent ejecta. Little down-flow variation in 

temperature.
14 DIRECT TEMPERATURE MEASUREMENTS OF DEPOSITS, MOUNT ST. HELENS, WASHINGTON, 1980-1981 

TABLE 3. Temperatures of deposits of the debris avalanche of May 18, 1980

Station

(fig. 12)

F)A1

DA9

F)A^

DA4 

DAS Lsr\.~j 

DA6 

DA7 LJr\ I 

Date

(1980)

May 28-

May 28-

May 29-

May 29-

May 29-

May 24-

May 30-

Depth

(m)

1.4+

1.5

1.5

1.2

1.4

3.0+

0.5

Maximum

temperature

(°C)

98

91

72

68

74

97

72

Distance

traveled

(km)

7.4

11.0

15.5

20.8

25.2

11.6

7.4

Remarks

Temperature in pipe implanted May 24, 1980: 37°C at 20 cm; isothermal at 1.4-3.4 m.

Direct insertion of thermocouple; four random sites: 86, 87, and 91°C

at 1.5m, and70°Cat 1.4m.

Direct insertion of thermocouple; five random sites: 51°C at 90 cm,

and 46°, 45°, 66°, and 72°C at 1.5 m.

Direct insertion of thermocouple; six random sites: 42°C at 91 cm,

56°C at 103 cm, 62°C at 104 cm, 68°C at 128 cm, 67°C at 123 cm,

and 49°C at 128 cm.

Direct insertion of thermocouple; seven random sites: 64 and 74°C at

1.4 m, and 48, 50, 61, 66, and 70°C at 1.5 m.

Isothermal profile segment 3 to 4.6 m in pipe that penetrated

overlying ponded deposits of the blast.

Thermometer inserted into bottom of freshly dug pit (Voight and

others, 1981).

C/D 

2 110 C/D

LU

LU

LU

cr. 

o 90

LU OU

Q

z

LU 80

cr.

13

< 70 

cr

LU

Q_

^ fin

A

0 

A

_

V A A 

A

i i

0 10 20

DISTANCE OF TRAVEL, IN KILOMETERS

30

D

FIGURK 13. Downflow temperature variation at stations in deposits of debris 

avalanche of May 18. A, Temperatures versus distance of travel (see table 3). 

Open symbols, tongue in North Fork Toutle River; filled square, tongue in 

South Coldwater Creek; filled inverted triangle, tongue in west arm of

Spirit Lake (see fig. 12 for location and type of measurement). B-D. Alternative 

flowage mechanisms that might account for downflow decrease in 

temperatures. AL, accidental debris, water, alluvium, and air incorpor^* 

by moving mass; C, cooler; H, hotter.
TEMPERATURE OF THE DEPOSITS 15

In comparison with the subsequent pumiceous pyroclastic-flow deposits, deposits of the blast were emplaced at relatively low temperatures (table 2), a result consistent (1) with 

the observations by Hoblitt (1980), Hoblitt and others (1981), 

Moore and Sisson (1981), and Waitt (1981) that the blast deposits contain a large percentage of accidental material and (2) 

with the interpretation that most of the relatively dense juvenile 

dacite in the deposits came from partially solidified, cooler parts 

of the cryptodome that had been emplaced in the volcano during the preceding few months.

Field and temperature evidence suggest that, in some 

drainages, more than one flow unit composed the ponded deposits. An emplacement temperature of 119°C is suggested for 

deposits in the lower part of Castle Creek (sta. 5), whereas data 

from upflow stations plot on curves that become isothermal at 

about 96°C. Similarly, upward or upflow decreases in the temperatures of flow units is suggested for the ponded deposits in

South Coldwater Creek and Smith Creek. Because the stratigraphy in the hills surrounding these drainages does not suggest 

multiple blast episodes, we suspect that the pattern of lower 

temperatures higher in the section in the ponded deposits may 

reflect either (1) the grain-size distribution of the deposits (in 

Smith Creek, the lower deposits are coarser grained and thus 

lost less heat during transport than the overlying finer grained 

material) or (2) a longer residence time and cooling as a veneer 

deposit before secondary mobilization into the valleys.

Two additional features are notable in the data for the blast: 

(1) emplacement temperatures change little along radial flow 

paths between 4 and 20 km from the vent (figs. 15A, C, D), and 

temperatures may increase downflow along some flow paths 

(figs. 15E, F); and (2) emplacement temperatures appear to vary 

closely with the azimuth of the station from the vent (fig. \5B). 

Deposits in the east sector of the devastated area were emplaced 

at significantly higher temperatures than those in the north

122°30'

46° 

22' 

30"

122°22'30" 122°15' 122°07'30" 122°00'

46° 

15'

46C 

07' 

30"

EXPLANATION

Area of blast deposits of May 1 8 

Seared zone of blast deposits

325

6 Temperature station 

Temperature (in °C)

Measured emplacement 

240 0 Calculated emplacement 

"" O Estimated emplacement 

103 + Minimum

T Collapsed summit rim Hachures point 

>v cy } downslope in crater formed May 18

-Approximate limit of searing 

and weak blast effects south 

of crater of May 18

4 MILES

I

\4 KILOMETERS

FIGURE 14. Sketch map of Mount St. Helens area, showing temperatures 

of deposits of the blast of May 18. Circled number is for a veneer 

deposit; all others are for ponded deposits. Numbe-s separated by a

solidus (/) denote temperatures of deposits having thermal stratigraphy 

(younger/older). See table 4 for details.
16 DIRECT TEMPERATURE MEASUREMENTS OF DEPOSITS, MOUNT ST. HELENS, WASHINGTON, 1980-1981

TABLE 4. Temperatures of deposits of the blast of May 18, 1980 

[Temperatures: E, measured emplacement; e, estimated emplacement; c, calculated emplacement (Ryan and others, 1981, 1990); m, minimum; azm, azimuth]

Station Date 

(fig. 14) (1980)

Depth Tempera- Distance Direction

(m) ture (°C) from vent from vent

(km) (azm)

Locality Remarks

1 June 5 

2 June

June 9 

4 June 9 

5 June 9 

1.9 m83-e96 3.7

3.0+ E96 4.9

1.5 m82, e96 4.7

1.5 m82, e96 5.1

1.8 E119 5.3

6 June 11- 1.5 m67, ellO 10.6

7 . ._. June 5 

8 June 11-

1.2 m66, cllO 12.5 

1.5 m!03 19.3

10U - June

10L - June

315 Upper Studebaker Creek.

316 Middle Studebaker Creek.

307 Upper E. Castle 

Creek #1.

307 Upper E. Castle 

Creek #2.

310 Lower E. Castle 

Creek.

300 Upper E Jackson 

Creek.

308 Lower E Jackson 

Creek.

31 7 Hoffstadt Creek.

9- ._ June 3 3.7+ El90 8.4

2.5+ E109 9.4

3.0 El 16 9.4

UN May 23 3.0+ E143 10.5

US May 24 2.0 ml26 10.5

12 May 23 0.3 ml 25 13.7

341

354

354

331

331

Bench on N. 

side of Toutle River.

Upper unit, middle S. Coldwater Creek.

Lower unit, middle S. Coldwater Creek.

Lower S. Coldwater Creek.

323 Coldwater I Observation Post.

Ponded deposit of unknown thickness in same 

drainage as station 2; temperature profile to 1.9 

m by direct insertion; profile identical to that at 

station 2 from 0.5 to 1.9 m.

Thick ponded deposit; temperature profile to 4.5 

m, direct insertion at two sites to 1.5 m, 1.5-4.5 

m in pipe at one site; nearly identical upper 

profiles, isothermal at 3-4.5 m.

Same drainage as at stations 4 and 5; single measurements by direct insertion at 1 and 1.5 m at 

five sites plot on profile of station 2 in the next 

drainage east.

Same drainage as stations 3 and 5; single 

measurements by direct insertion to 1.5 m at 

five sites plot on profile of station 2.

Thick ponded deposit; temperature profile to 2.8 

m and single measurements at three other sites 

across direction of flow; erratic values 

(observed at no other locality) probably result 

from observed buried cold and smoldering 

logs.

Rootless ponded deposit, 3.3 m thick; single measurements by direct insertion downward to 1 m 

and horizontally 3 m, 1.5 m from surface in cut 

bank.

Rootless ponded deposit, 1.5 m thick; temperature 

profile by direct insertion to 1.5 m; parabolic 

curve.

Rootless ponded deposit, more than 3 m thick; 

water-saturated top and base but dry center; 

single measurements at several sites.

Ponded deposit more than 10 m thick; 

temperature profile to 4.2 m; direct insertion to 

1.5 m, 1.5-4.2 m in pipe; steep gradient 

between 2.7 and 3.7 m, isothermal at 3.7-4.2 m.

Ponded deposit stratigraphically higher than at 

station 10L; temperature profile by direct insertion to 3 m and single measurement at another 

site; isothermal at 2-3 m.

Ponded deposit in same drainage but stratigraphically higher than station 11; temperature profile by direct insertion to 3 m; isothermal 

profile 2.5-3 m.

Ponded deposit 20 m south of incising stream, 

lowest exposed unit in drainage at least 10 m 

thick; temperature profile to 5.9 m; direct insertion to 1 m, 1-5.9 m in pipe; isothermal at 1-5.0 

m, slight reversal at 5-5.9 m.

Ponded deposit, 60 m south of station UN, nearer 

to bedrock, probably only 3 m thick; temperature profile to 5.5 m; direct insertion to 1 m, 1- 

5.5 m in pipe; parabolic in upper 3 m, lower 

part (3-5.5 m) is isothermal and probably in 

deposits of the debris avalanche.

Primary veneer deposit of the blast, 0.75 m thick; 

temperature profile by direct insertion; sharp 

parabolic curve, maximum at 0.3-0.5 m.
TEMPERATURE OF THE DEPOSITS

TABLE 4. Temperatures of deposits of the blast of May 18, 1980 Continued

17

Station

(fig. 14)

Date

(1980)

Depth

(m)

Temperature (°C)Distance

from vent

(km)

Direction

from vent Locality

(azm)

Remarks

13E - May 27 1.2-2.5 E150, c!60 19.0

13W - May 27 1.1 E150 19.0

14 .. June 11- 2.5+ E109 11.0

15N- June 3 3.0+ E144 12.2

15S - May 22 3.5-4.5 E147 12.2

16 June 6 1.5-2.0 ml52 13.7

17 . June 8 1.0-1.3 ml 77 16.7

18U June 6 

18L - June 6

19.. June 9 

20 June 8 

21 June 6 

1.0-1.3 E182 7.7 

5.3 m248 7.7

1.8 ml63-e!70 8.1

1.5 ml 80, c240 10.4

1.5 m277, c325 12.3

334 West Schultz 

Creek.

334 -do. 

013 West Arm Spirit 

Lake.

019 Bench above 

Lang mine.

019 ----- do. ----- 

017 Bench on NW. 

side of Mount 

Margaret.

032 S. Green River058 W. Smith Creek. 

058

069 Lower Smith 

Creek.

049 Upper main 

Smith Creek.

064 Middle Bean 

Creek.

Rootless ponded deposit, about 3.2 m thick, 33 m 

from east edge of deposit; temperature profile 

to 3 m, direct insertion to 1.2 m, 1.2-3 m in 

pipe; isothermal at 1.2-2.5 m, slight temperature reversal of 4°C at 2.5-3 m.

Site 10 m west of station 13E, 43 m from east edge 

of deposit; temperature profile to 3.1 m; direct 

insertion to 1.1 m, 1.1-3.1 m in pipe; broad 

parabolic curve with the same maximum temperature (150°C) as isothermal temperature of 

station 13E profile.

Thick ponded deposit; temperature profile by 

direct insertion to 3 m downward and 3 m 

horizontally, 5 m from surface in cut bank; 

isothermal from 2.5 to 5 m.

Ponded deposit, 6-8 m thick; temperature profile 

to 3.7 m; direct insertion to 3 m, 3-3.7 m in 

pipe; isothermal at 3-3.7 m.

Site 40 m south of station 15N; temperature profile to 5.5 m; direct insertion to 1 m, 1-5.5 m 

in pipe; isothermal at 3.0-4.5 m, temperature 

reversal to 98°C at 4.5-5.5 m.

Rootless ponded deposit, 2.9 m thick, over ice; 

temperature profile by direct insertion to 2.9 m; 

sharp parabolic curve, maximum at 1.5-2 m.

Rootless ponded deposit, 2.4 m thick; temperature profile by direct insertion to 2.4 m at three 

sites; three nested broad parabolic curves, 

maximum at 1-1.3 m.

Rootless ponded deposit; temperature profile to 

5.3 m; direct insertion to 1 m, 1-5.3 m in pipe; 

temperature profile suggestive of two flow 

units, upper cooler unit approaching isothermal at 182°C at 1-3.3 m, then steep 

gradient at 3.3-5.3 m in lower unit; upper unit 

may be equivalent to that at station 19.

Rootless thick ponded deposit, downflow from 

station 18; temperature by direct insertion to 

1.8 m approaches isothermal (170°C) at 1.5-1.8 

m; may be equivalent to upper isothermal unit 

(182°C) at station 18.

Rootless ponded deposit, 2.7 m thick; temperature profile by direct insertion to 2.7 m; broad 

parabolic curve, maximum at 1.5 m.

Rootless ponded deposit, 2.93 m thick; temperature profile by direct insertion to 2.93 m; sharp 

parabolic curve.

sector, which, in turn, were hotter than those in the west sector 

(figs. 15C-F). These features in the data are explained in the 

section entitled "Summary and Discussion."

The cooling histories of the blast deposits were monitored 

at eight sites at six stations for as many as 307 days after the 

emplacement of these deposits (see appendix 2). Empirically,

these studies indicate that, in the absence of heavy precipitation 

and in deposits of the type produced by the blast, isothermal 

profile segments are still measurable (1) as many as 30 days 

after emplacement in deposits 4 to 5 m thick and (2) as many as 

9 to 10 days after emplacement in deposits 2 to 3 m thick but 

not (3) within as few as 5 days in deposits 1 m or less thick.
18 DIRECT TEMPERATURE MEASUREMENTS OF DEPOSITS, MOUNT ST. HELENS, WASHINGTON, 1980-1981

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FIGURE 15. Emplacement temperatures (from table 4) of deposits of the 

blast of May 18 versus distance (A) and azimuth (B) of stations from 

vent. Filled circles, measured emplacement temperatures; open circles, 

estimated emplacement temperatures; circled dots, calculated emplace20 0 5 10 15 

DISTANCE, IN KILOMETERS

20

ment temperatures; crosses, minimum temperatures; vertical lines connect 

two measurements at same site. Temperatures are shown within azimuth 

sectors on C (west), D (northwest), E (northeast), and F (east).
TEMPERATURE OF THE DEPOSITS 19

However, Ryan and others (1981,1990) showed that calculated 

emplacement temperatures can be obtained in deposits as thin 

as 1.5m from temperature-depth measurements beginning almost 3 weeks after emplacement.

In addition, the cooling studies allowed calculation of 

onsite thermal diffusivities of the blast deposits (ranging from 

2.2x10"3 to 4.0x10'3 cm2/s) and revealed that the bottoms of the 

deposits became cooler and the tops hotter than would be predicted by theoretical radiative- and conductive-cooling models. These anomalies probably were generated by the transfer 

of heat from the bottom to the top of the deposits by steam 

generated at or below the bottom of the deposits (Ryan and others, 1981, 1990).

PYROCLASTIC-FLOW DEPOSITS OF MAY 18,1980

Four stations on the pumiceous pyroclastic-flow deposits, within 5.04 to 5.67 km of the vent (stas. b, c, f, i, fig. 16; 

table 5), yielded isothermal temperature segments; emplacement temperatures ranged from 297 to 367°C (see tables in

appendix 2). Near-isothermal segments occurred in profiles from 

station a (418°C) in the flow deposits 0.7 km from the vent and 

from station m (159°C) in the ash-cloud deposit of the flows 

8.95 km north of the vent. In addition, an emplacement temperature is thought to be represented by two identical 307°C 

temperatures obtained 6.60 and 7.06 km from the vent at depths 

of 30 and 1.3 m, respectively, in a phreatic pit in the flow deposits (stas. j, 1). Attempts to obtain emplacement temperatures 

nearer than 0.7 km from the vent were frustrated by thin and 

spotty deposits that had cooled appreciably before they could 

be safely visited.

The emplacement temperatures vary only slightly in both 

the crossflow (70°C in approx 3 km) and downflow (110°C in 

approx 6 km) directions in the pumiceous pyroclastic-flow deposits of May 18 (figs. 16, \1A). In contrast, the temperature 

suggested for the cogenetic ash cloud was significantly lower than 

those in the flow deposits just 2 km to the south (figs. 16, \1A). 

This difference suggests that the elutriation clouds of the flow 

deposits were substantially cooler than their source flow deposits.

The emplacement temperatures of the May 18 flow deposits were relatively low in comparison to many subsequent 

pyroclastic-flow deposits (approx 300^+20°C), and stratigraphic

TABLB 5. Temperatures of deposits of the pumiceous pyroclastic flows of May 18, 1980 

[Temperatures: E, measured emplacement; e, estimated emplacement; m, minimum]

Station Date 

(fig. 16) (1980)

Depth Temperature 

(m) (°C)

Distance

from vent

(km) Locality Remarks

a - June 3- 3.9 E418

b -June 1 - 2.3+ E342

c June 24 5.4+ E326

d ~ May 31 1.5 m270

e May 31 1.4 m288

f May 28 1.3+ E297

g May 31 1.5 m297

h ~ May 31 1.5 m305

i . June 1 1.8+ E367

j . June 1 - 30 E307

k- June 1 - 1.5 m217

1 June 1 1.3 E307

m ... May 30 2.0 el59

n- May 27 1.0 m97

0.70 Crater amphitheater 

5.08

5.04

5.10

5.14

5.67

5.20

5.20

5.30

6.60

6.84 

7.06 

8.95

4.55

Middle of pumice

apron. 

Middle of pumice

apron.

Middle of pumice

apron. 

Middle of pumice

apron. 

Middle of pumice

apron. 

Middle of pumice

apron. 

Middle of pumice

apron. 

Middle of pumice

apron. 

SE. bottom of phreatic basin over

Spirit Lake 

Lodge. 

SW. rim of phreatic 

basin over Spirit 

Lake Lodge. 

NW. rim of phreatic 

basin over Spirit 

Lake Lodge. 

Headwaters of S Coldwater Creek.

Shoestring Glacier

apron.

Temperature profile to 6.1 m; direct insertion to 1.5m, 1.5-6.1 m

in pipe; irregular curve suggestive of two flows, hotter down

section. 

Temperature profile to 6.3 m; 0-1.5 m direct insertion, 1.5-6.3 m

in pipe, isothermal at 2.3-5.3 m, slight reversal at bottom. 

Temperature profile to 5.4 m; direct insertion to 1 m, 1-5.4 m

with Teflon-insulated permanent thermocouple, isothermal at

4.4-5.4 m. 

Single measurement.

Single measurement.

Temperature profile in pipe to 4.3-m depth; isothermal at 1.3-2.3

m; temperature reversal of 26°C from 2.3-4.3 m. 

Single measurement.

Spot temperature 120 m S. of station i at stratigraphically higher

level above breakaway slip face. 

Temperature profile to 2.8 m, 0-1.5 m direct insertion, 1.5-2.8 m

in pipe; isothermal at 1.8-2.8 m. 

Single measurement in pipe driven 3 m horizontally into deposit

at bottom of large phreatic and collapse(?) pit, 30 m below

surface.

Single measurement S. of SW. rim of phreatic pit of station j;

probe inserted 1.5 m into phreatic surge deposits of unknown

thickness. 

Single measurement, NW. rim of pit; 1.5-m probe inserted 1.3 m

into deposit through 0.2-m phreatic surge deposit.

Single measurement, with nearby temperature profile to 1.7-m in

ash-cloud deposit. 

Profile in pipe, isothermal at boiling point of water from 0.1 to

1m.
20 DIRECT TEMPERATURE MEASUREMENTS OF DEPOSITS, MOUNT ST. HELENS, WASHINGTON, 1980-1981

122° 14' 13' 12' 122°08'

EXPLANATION

Pyroclastic flows 

of May 18

a, Temperature station

Temperature (in degrees C) 

326 Measured emplacement

418 O Estimated emplacement 

270 + Minimum emplacement

2 KILOMETERS

CONTOUR INTERVAL 400 FEET

FIGURE 16. Sketch map of Mount St. Helens area, showing distribution and temperatures of deposits of pumiceous pyroclastic flows of May 18. 

Geology after Rowley and others (1981, fig. 295) and Lipman and Mullineaux (1981, pi. 1).
TEMPERATURE OF THE DEPOSITS 21

400

300

200

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I O

- May 18, 1980

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DISTANCE, IN KILOMETERS

- B

600 

500 C 

400 

I June 12, 1980

56 

DISTANCE, IN KILOMETERS

700

600 

500

DISTANCE, IN KILOMETERS

9 10

1C 

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DISTANCE, IN KILOMETERS

EXPLANATION

 Measured emplacement temperature 

O Estimated emplacement temperature 

+ Minimum temperature

 Down flow change in temperature in 

same flow unit

FIGURE 17. Temperatures of deposits of pumiceous pyroclastic flows of 1980 versus distance from the vent. A, May 18 (from table 5). B, June 12 (from table 7); 

a-d, thermal sequence from top to bottom. C, 1901 P.d.s.t. July 22 (from table 8). D, August 7 (from table 9). E, 2112 P.d.s.t. October 17 (from table 10).
22 DIRECT TEMPERATURE MEASUREMENTS OF DEPOSITS, MOUNT ST. HELENS, WASHINGTON, 1980-1981

variation of temperature was suggested in only one profile of 

the deposits station a (fig. 16; table 5; also see fig. 32A and 

tables in appendix 2). Moreover, the very low temperature of 

the upper 220°C unit at this near-vent station suggests that this 

unit probably resulted from secondary gravitational mobilization of hotter primary deposits higher on the crater walls, possibly even after cessation of the May 18 eruption.

The pumiceous flow deposits of May 18 consist of numerous 1- to 20-m-thick units (Rowley and others, 1981). The 

reasons for the observed paucity of thermal stratigraphy and 

the relatively low and uniform emplacement temperatures in 

the deposits are unknown. However, nearly uniform collapse of 

a rather energetic column, in combination with thermal equilibration between flow units before our measurements, is consistent with the data.

Single-depth minimum temperature measurements were 

made at five stations north of the vent (fig. 16; table 5). The 

lowest of these temperatures (217°C at sta. k) was measured in 

pyroclastic-flow material that had been remobilized by phreatic 

explosions to form surge deposits which locally mantle the flow 

deposits (figs. 105, C). Apparently this remobilized material 

cooled about 90°C during the phreatic eruptions and base-surge 

deposition.

The temperature of 97°C obtained from a May 18 pyroclastic-flow deposit east of the volcano (sta. n, fig. 16; table 5) 

also is not thought to be an emplacement temperature. This temperature equals the boiling point of water at the site, and the 

station was adjacent to a mudflow that postdated the pyroclastic flow.

Monitoring of the cooling histories of deposits of the pumiceous pyroclastic flows of May 18 was initiated at five stations. Although two of these stations (a, i, fig. 16) were destroyed by pyroclastic flows of the June 12 eruption, studies at 

the other stations (b, c, f) continued for as many as 266 days 

after emplacement before being destroyed by erosion (see figs. 

32B-D and tables in appendix 2). Empirically, these studies show 

that, in the absence of heavy rainfall, isothermal profile segments can be recovered in thick (more than 20 m) pyroclasticflow deposits similar to those of the May 18 pyroclastic flows

(1) 3 to 4 months after emplacement at depths of 3 to 4 m and

(2) as long as 5 months after emplacement at depths greater 

than 5 m.

PYROCLASTIC-FLOW DEPOSITS OF MAY 25,1980

Pyroclastic-flow deposits of the May 25 eruption were 

small. Temperature profiles were obtained from the largest of 

these deposits, near their distal ends where they were thickest 

(max 2.5 m): one at 1,170-m (3,900-ft) elevation, and one east 

of the main avalanche valley on the Forsyth Glacier at 1,585-m 

(about 5,200-ft) elevation (fig. 18; table 6). Because of poor 

weather, these deposits were not discovered until 2 days after 

the May 25 eruption. Temperature measurements were not made 

until 6 days after emplacement, when the profiles no longer 

contained isothermal segments. The maximum temperatures on 

the two profiles were 156 and 155°C (fig. 18; tables 2, 6; see 

fig. 33 and tables in appendix 2).

PYROCLASTIC-FLOW DEPOSITS OF JUNE 12,1980

Emplacement temperatures of 361-389°C, 450-460°C, 

495°C, and 602°C were obtained from isothermal profile segments of several sites at five stations on deposits of the June 12 

pyroclastic flows (fig. 19; table 7; also see fig. 34 and tables in 

appendix 2). These stations span a downflow distance of more 

than 3 km on the three main lobes of the deposits (fig. 19). The 

June 12 emplacement temperatures generally were higher than 

those of the deposits of the previous two eruptions (table 2). 

Measurements at the first station on the June 12 deposits began 

10 hours after cessation of the eruption (sta. 6-4, figs. 19, 34), 

and the last station of the initial series was located only 27 hours 

later. This early access resulted in many features in the temperature data which indicate that the flow units, matrix, and 

pumice blocks had not yet reached thermal equilibrium.

An abrupt temperature change with depth on the profile 

of station 6-3C occurred at the exposed stratigraphic contact 

between two flow units (figs. 19, 34D). The upper unit was 

emplaced at 361°C. Profiles for several sites at station 6-4 (see 

figs. 19 and 34£ and tables in appendix 2) indicate that the 

emplacement temperature of the underlying unit was 450-460°C.

Later deeper profiling at station 6-4F revealed a second 

abrupt temperature increase, followed by a 490-495°C isothermal 

profile. These data are thought to indicate the presence of a

TABLE 6. Minimum temperatures of deposits of the pumiceous pyroclastic flows of May 25, 1980

Station Date Depth Temperature Distance 

(fig. 18) (1980) (m) (°C) from vent Locality

(km)

Remarks

25-1 - May 31 2.4 156 2.70 

25-2 - May 31 2.1 155 4.40

Forsyth Glacier E. Rootless deposit 2.7 m thick; temperature profile through deposit 

of Sugar Bowl. to 3.9 m; direct insertion of thermocouple to 1.4 m, 1.4-3.9 m

in pipe; sharp parabolic curve.

Base of the stair- Rootless deposit 2.5 m thick; temperature profile to 3.6 m; direct 

steps. insertion of thermocouple to 0.9 m, 0.9-3.6 m in pipe; sharp 

parabolic curve.
TEMPERATURE OF THE DEPOSITS 23

122° 14' 122°08'

a

SPIRIT LAKE

EXPLANATION

Pyroclastic flows 

of May 25

Temperature station 

Shows station number 

and minimum temperature 

in degrees C)

Limit of flow Dashed where 

approximate

CONTOUR INTERVAL 400 FEET

FIGURE 18. Sketch map of Mount St. Helens area, showing distribution and minimum temperatures of deposits of pumiceous pyroclastic flows of 

May 25. Geology after Rowley and others (1981, p. 493, 496; Lipman and Mullineaux (1981, pi. 1).
24 DIRECT TEMPERATURE MEASUREMENTS OF DEPOSITS, MOUNT ST. HELENS, WASHINGTON, 1980-1981

122° 14' 13' 12' IT 10' 122°08'

46° 

16'

15'

141

13'

46° 

12'

EXPLANATION

Pyroclastic flows 

L _a of June 12

6-2, Temperature station number /

Temperature (in degrees C)( 

602 Measured emplacement \

545 + Minimum emplacement \

(a) Part of thermal sequence

(a-d, top to bottom) 

0 2 KILOMETERS

I_________|_________| 

CONTOUR INTERVAL 400 FEET

I____________I____________I

FIGURE 19. Sketch map of Mount St. Helens area, showing distribution and temperatures of deposits of pumiceous pyroclastic flows of June 12.

Geology after Rowley and others (1981, fig. 295).
TEMPERATURE OF THE DEPOSITS

TABLE 7. Temperatures of deposits of the pumiceous pyroclastic flows of June 12, 1980 

[a-d, thermal sequence from top to bottom of deposit. Temperatures: E, measured emplacement; e, estimated; m, minimum; p, temperature against pumice block]

25

Station 

(fig- 18)

6-1- 

6

^

6

<-\

6

o/^

Date 

(1980)

June 14 

-June 13 

June 14 

June 14 

Depth 

(m)

1.5

0.8 

1.5 

0.5+

Temperature (°Q

E389a 

p420

E602d 

m414b 

E361a

Distance 

from vent 

(km)

4.44

5.56 

6.56 

6.56

Locality

Top of N. pumice 

apron.

E. end of phreatic 

basin over Spirit 

Lake Lodge. 

E. end of phreatic 

basin.

Remarks

Late coarse-grained deposit, thickness unknown; temperature by 

direct insertion of thermocouple; essentially isothermal at 0.75- 

2 m, with one high reading of 420°C against an obstruction at 

1.5 m (pumice block); spot temperature at a second site 30 m to 

W. plots on the profile. 

Distal end of western tongue, 1.5 m thick; temperature profile by 

direct insertion to 1.3 m, isothermal atO.8-1.1 m; measurement 

taken 14 hours after emplacement. 

Ponded deposit more than 20 m thick; temperature profile by direct 

insertion to 1.5 m, very steep gradient from 0.75 to 1.5 m.

Late coarse-grained deposit at station 6-3, 2.45 m thick; temperature profile to 2 m; isothermal at 0.5-1.5 m, temperature

6-4A - 

B - 

C - 

DEF -

June 13- 

June 13- 

-June 13- 

June 13- 

June 13- 

June 14-

6-5 - Aug. 5-

6-6 Aug. 6 

6-7- June 13-

1.0+

1.5

1.0+

1.0, 1.8

1.5,2.5 

1.5,4+

6.5 

6.0

0.75+

E460b 

m448, e450

E450b

E460b, E490c

E463b, E495c

E460b, E495c,

p528

m535d 

m545d

E495c 

p521 

p422

6.71

6.72

6.73

6.74

6.75

6.75

6.88

6.94

6.75

Center of phreatic 

basin over Spirit 

Lake Lodge.

W. end of phreatic 

basin over Spirit 

Lake Lodge.

W. end of phreatic 

basin over Spirit 

Lake Lodge.

Spirit Lake tongue 

increase at 1.5 m.

Ponded deposit, more than 20 m thick; temperature profiles at six 

sites on N.-S. traverse from S.-central of edge of deposit, as 

follows: 10 m (A), 20 m (B), 30 m (C), 40 m (D), 50 m (E), 53 

m (F); by direct insertion of thermocouples except for 3-5.3 m 

in pipe at F. A, approaching isothermal at 1-2 m; B, approaching isothermal at 1.5 m; C, isothermal at 1-1.5 m; D, isothermal 

at 1-1.5 m at 460°C, step to 495°C at 1.8 m; E, as at D with step 

at 2.2 m; F, as at D with step to 495°C at 2.8 m, 528°C at 2 m 

against probable pumice block. Measurements at.A-E taken 10 

hours after emplacement.

Ponded deposit, more than 20 m thick; temperature profile to 6.5 m, 

0-1 m by direct insertion, 1.5-6.5 m in buried pipe; steep gradient below 3.5 m.

Ponded deposit, more than 20 m thick; temperature profile to 6 m, 

0-1 m by direct insertion, 1.5-6 m in buried pipe; steep gradient 

from 3.5 to 6m.

Eastern tongue, 2-3 m thick; temperature profile by direct insertion of thermocouple to 1.9 m, isothermal at 0.75-1.9 m; single 

measurements at 0.75 and 1.5 m at three other sites lie on the 

profile except for one high of 521°C and one low of 422°C 

against blocks; measurement taken 17 hours after emplacement.

flow contact between the 450-460°C unit and a buried unit that 

may be correlative with the surficially exposed 495 °C flow unit 

at station 6-7 (fig. 19).

Evidence that the pumice blocks had not thermally equilibrated with the matrix was obtained from examples at stations 

6-1, 6-4F, and 6-7 where, in otherwise-smooth isothermal temperature-depth profiles, significantly higher or lower temperatures were obtained when the thermocouples encountered hard 

obstacles that are interpreted to be pumice blocks (see fig. 34 

and tables in appendix 2).

The thermal stratigraphy of the June 12 temperature data 

is summarized in figure 20. The basal location of the hottest 

unit (sta. 6-2, fig. 19) is from a tentative correlation (fig. 21) 

between the 602°C unit at station 6-2 and the 545°C material at 

6 m at station 6-6 (fig. 19), obtained by deep profiling using the 

aerial penetrator type A (see fig. 29A and "Instrumentation and

Techniques" of appendix 1) after thermal discontinuities between flow units had disappeared.

The correlation of the surficial 389°C unit at station 6-1 

with the surficial 361°C unit at station 6-3C (fig. 21) also is 

tentative, because the required mapping was delayed by poor 

weather and other duties and because the pertinent outcrops were 

subsequently destroyed during the July 22 eruption. However, 

if the correlations in figure 21 are valid, downflow temperature 

variations were small in the youngest and the oldest units 

emplaced in the June 12 eruption (fig. 17fi).

Conclusions regarding the cooling of pyroclastic-flow 

deposits were greatly aided by our early and repeated access to 

the deposits of June 12. For the first time, we determined directly that single measurements at the centers of deposits as 

thin as 1.5m can detect emplacement temperatures if taken 

within 12 hours of deposition. We also determined that after 24
26 DIRECT TEMPERATURE MEASUREMENTS OF DEPOSITS, MOUNT ST. HELENS, WASHINGTON, 1980-1981

hours the emplacement temperatures were still preserved at 3- 

m depths in thick deposits but that a parabolic temperature-depth 

profile developed in a 1.5-m-thick deposit.

Our long-term temperature monitoring of the June 12 

deposits continued for as many as 241 days after emplacement 

(see tables in appendix 2), until the sites were flooded and buried by alluvium in early 1981. Cooling of the June deposits 

appears to have proceeded more rapidly than that of the May 

deposits, possibly because of the higher clast-to-matrix ratio of 

the June deposits (Kuntz and others, 1981). However, essentially unchanged temperatures were observed at 6 m at station 

6-5 for more than 150 days after emplacement.

PYROCLASTIC-FLOW DEPOSITS OF JULY 22, 1980

Emplacement temperatures of 642 to 688°C and 658° to 

678°C were obtained at several sites at two stations in the 

younger of the two pyroclastic-flow units emplaced July 22 (stas. 

7U-1, 7U-4, respectively, fig. 22; table 8). These temperatures 

are more than 50°C higher than the highest temperature measured in the June 12 deposits. The measurements were obtained 

from 18 hours to 4 days after deposition, and emplacement temperatures were essentially unchanged along a downflow distance of 1.3 km between the two stations (fig. 17C).

200 400 

TEMPERATURE, IN DEGREES CELSIUS

600

FIGURE 20. Composite thermal profile (from fig. 34) in deposits of pyroclastic flows of June 12. Squares represent temperatures of pumice 

blocks encountered during profiling.

As was the case in the June 12 deposits, several profiles 

suggest incomplete thermal equilibrium between pumice blocks 

and the ash matrix (671-705°C; sta. 7U-1, fig. 22; see fig. 35£ 

and tables in appendix 2).

We failed to obtain isothermal profiles in the upflow stations on the lower (1825 P.d.s.t.) unit of the July 22 deposits, 

probably because at these sites the deposits were thin (about 1 

m thick) and had developed parabolic temperature-depth profiles before our measurements (fig. 22; table 8; also see figs. 

35/4, B, D, and tables in appendix 2). However, a somewhat 

ragged isothermal segment can be postulated from the profiles 

obtained at the toe of the longest tongue of the unit (sta. 7L-7; 

see fig. 35D and tables in appendix 2), although the indicated 

emplacement temperature (avg 295°C) is about 200 and 150°C 

lower than the minimum temperatures obtained 2 to 30 hours 

later at the upflow sites (stas. 7L-4, 7L-2, respectively, fig. 22; 

table 8).

The low temperature in the toe of the 1825 P.d.s.t unit 

indicates an appreciable downflow decrease in emplacement 

temperature. This relation was not observed in any other flow 

deposits in our studies at Mount St. Helens, and this temperature is the lowest temperature measured in the post-May 18 

pumiceous flow deposits of Mount St. Helens.

The station was the only one in our studies that was located on the toe of a deposit, and, in most cases, we and Kuntz 

and others (1981) observed that the toes of flow lobes were 

areas where pumice blocks and the coarsest particles were concentrated relative to material in the flow channels. Thus, one

297- 

367

«418

Pumice Amphitheater 

apron

May 18 flows

495

East 

lobe

=361

460±10

490

>545

389

602

Main 

lobe 

pond

June 12 flows

Upper 

apron

West 

lobe

Upper flow fifin+10 (1901 P.d.s.t.) 660±1 °

Lower flow Kna 

(1825 P.d.s.t.) >bUB

Upper flow

Lower flow

Main lobe East lobe 

July 22 flows

Upper apron 

October 17 flows

FIGURE 21. Thermal stratigraphy in pumiceous pyroclastic flows of 1980. 

Dashed lines indicate possible lateral correlations. Values from figures 16, 

19, 22, and 25, in degrees Celsius, a-d, thermal sequence from top to 

bottom.
TEMPERATURE OF THE DEPOSITS 27

122°14 122°08'

EXPLANATION

Pyroclastic flows 

of July 22

7L-1, Temperature station number; 

L, lower flow; U, upper flow

Temperature (in degrees C) 

320 Measured emplacement

412 + Minimum emplacement

0 2 KILOMETERS

I I

CONTOUR INTERVAL 400 FEET

FIGURE 22. Sketch map of Mount St. Helens area, showing distribution and temperatures of deposits of pumiceous pyroclastic flows of July 22.

Geology after Rowley and others (1981, fig. 295).
28 DIRECT TEMPERATURE MEASUREMENTS OF DEPOSITS, MOUNT ST. HELENS, WASHINGTON, 1980-1981

would expect rapid postdepositional cooling of the material in 

the toe through free circulation of air and steam. In this particular case, however, the toe material was very fine grained. Therefore, the data may indicate that the toe area of the flow is a 

region where interaction with air strongly cooled the pyroclastic material or that the deposit was transitional to an ash-cloud 

deposit.

Although long-term cooling studies were not done on the 

July 22 deposits, temperatures measured 21 and 25 days after 

emplacement at stations 7U-3,7U-5, and 7U-6 in the upper flow 

unit and at station 7L-6 in the lower flow unit suggest empirically that the July 22 deposits cooled at about the same rate as, 

or possibly somewhat slower than, the slightly finer grained 

(Kuntz and others, 1981) June 12 deposits.

TABLE 8. Temperatures of deposits of the pumiceous pyrodastic flows of July 22, 1980 

[E, measured equilibrium temperature; m, minimum temperature; p, temperature against probable pumice block]

Distance

Station Date Depth Temperature from vent 

(fig. 21) (1980) (m) (°C) (km)

Locality Remarks

Upper, salmon-colored flow (1901 P.d.s.t.)

7U-1 - July 23 0.5-1.75+ E642-688,

p705

7U-3- Aug. 16 1.0 m488

7U-4 - July 23 0.1-1.0 E658-678

7U-5- Aug. 12 1.0+ m412

7U-6 - Aug. 12 1.0+ m468

4.38 100 m NNW. of bottom of

the stairsteps.

5.6 1,000 m N. of distal end of

Aug. 7 western tongue.

5.64 3,640-ft elevation on E.

edge of main (western)

flow.

6.01 300 m SSW. of distal end of

E. tongue.

6.10 200 m SSW. of distal end of

E. tongue.

Thickness unknown; profiles by direct insertion

of thermocouples; four profiles measured 22

hours after deposition, two at 4 days; profiles

are essentially isothermal from 0.5 to 1.75 m

at 640±30°C, with higher temperatures against

probable pumice blocks.

Deposit 2 m thick; direct insertion of thermocouple to 1.5 m; broad parabolic curve.

Deposit about 1.5 m thick; single measurement

(658°C) 35 minutes after deposition; four temperature profiles by direct insertion of thermocouples 18 hours after deposition; three profiles and the 35-minute temperature describe

isothermal profiles from 0.10 to 1.0 m of

670±10°C.

Direct insertion of thermocouple to I m at two

sites; identical shallow gradients to 412°C.

Direct insertion of thermocouple to 1 m; shallow

gradient to 468°C.

Lower, tan-colored flow (1825 P.d.s.t.)

7L-2 - July 24 

7L-4 - July 23

7L-6- 

7L-7-

Aug. 12 

July 23

.3

.3

1.0

m442

m508

m264

0.5-1.0+ E269-320

4.63

5.64

6.1

6.44

800 m NNW. of base of the 

stairsteps.

Direct insertion of thermocouples to 1.5 m at four 

sites; profiles describe closely clustered, sharp 

parabolic curves.

See 7U-4 above Direct insertion of thermocouples to 1 m at four

sites; profiles describe closely clustered, sharp 

parabolic curves. Measurements taken 18 hours 

after emplacement.

See 7U-6 above Direct insertion of thermocouples to 1 m; profile

describes upper part of a broad parabolic curve. 

Distal area of flow; profiles by direct insertion of 

thermocouples at three sites, one single measurement (highest), 320°C, 55 cm, possibly two 

flow units. Parabolic curves to 0.5 m; maximum temperature, 260-304°C; isothermal 

between 0.75 and 1.2 m at 265-269°C. Measurements taken 16 hr after emplacement.

Just S. of SE. corner of 

phreatic basin over 

Spirit Lake Lodge at 

3,400-ft elevation.
TEMPERATURE OF THE DEPOSITS 29

PYROCLASTIC-FLOW DEPOSITS OF AUGUST 7,1980

Emplacement temperatures of 645±5°C were obtained 

from isothermal and nearly isothermal profile segments measured at several sites at two stations on the flow deposits of August 7 within 20 hours of their deposition (fig. 23; tables 2, 9). 

Temperatures measured in the medial and lateral levees (see 

stas. 8-2,8-3, figs. 36B, C, and tables in appendix 2) were slightly 

higher than those in the centers of the deposits, presumably 

because the thicker levees had lost less heat by convection and 

radiation before the measurements and contained a higher proportion of coarse clasts than the channels.

Temperature-depth profiles also were measured for the 

first time on the ejecta rampart around the vent (fig. 24). Measurements made as deep as 2.7 m at seven sites by August 13 

yielded temperatures of 725 to 830°C (calculated emplacement 

temperature, 850°C; Ryan and others, 1981, 1990).

Attempts to drive pipes deeper than 2.7 m at some 20 

other sites on the rampart were futile. Penetration generally 

ceased rather uniformly at about 1 to 1.5 m except in the thickest, coarsest, and lowest temperature deposits on the east part 

of the rampart (2-2.7 m in depth). The high temperatures and 

the nearly uniform depth of penetrability suggest that the nearvent facies of the August 7 deposits might be partially welded. 

An incipiently welded unit was observed in an older (June 12 

or July 22) near-vent unit exposed by slumping of the north 

side of the vent rampart in August. However, the temperatures 

of welding of this older unit are unknown.

In early October, cracks radial to the August 7 dome 

opened, and the exposed material glowed visibly in shades of 

yellow and red even during daylight. A temperature of 838°C, 

measured at a depth of 3 m in one of these cracks, plots directly

on the hottest temperature-depth profiles measured in mid-August.

Temperatures of the vent facies of the August 7 deposits 

indicate that eruption cooled the pyroclastic material by only 

about 140°C (magmatic temperature, 990°C; Melson and others, 1980; Melson and Hopson, 1981). However, even greater 

cooling of the pyroclastic material (approx another 200°C) occurred somewhere between the vent rampart and 2 km downstream (figs. 17D, 23). Thereafter, however, material in the deposit apparently cooled little or not at all along the rest of the 

path of flow.

Repeated measurement of profiles in the vent deposits 

provide data that indicate onsite thermal diffusivities of 

2.8xlQ-3 to 3.0xlO-3 cm2/s (Ryan and others, 1981,1990). These 

diffusivities do not differ appreciably from those obtained by 

Ryan and others (1981, 1990) for deposits of the blast of May 

18.

Long-term cooling studies were not possible in the thin 

downflow deposits of August 7. However, from the limited available data, these deposits cooled faster than the flow deposits of 

similar thickness from earlier eruptions, possibly because their 

comparatively higher clast-to-matrix ratios (Kuntz and others, 

1981) allowed faster convective cooling.

PYROCLASTIC-FLOW DEPOSITS OF OCTOBER 17, 1980

Temperature data for the October 17 deposits are relatively poor. Temperature-depth profiles to 1-m depth were measured at only one station (10-4L) near the terminus of the older 

(0928 P.d.s.t.) of the two main flow units (tables 1, 2, 10). 

However, two of the five profiles at that station suggest an

TABLE 9. Temperatures of deposits of the pumiceous pyroclastic flow of August 7. 1980 

[Temperatures: E, measured emplacement; c, calculated emplacement (Ryan and others, 1981, 1990); e. estimated emplacement; m, minimum]

Station 

(fig. 23)

Date 

(1980)

Depth Temperature 

(m) (°C)

Distance

from vent

(km)

Locality Remarks

-1 - Aug. 13 1.5+ E725-830, 0.20 

c850

5-2- Aug. 8. 1.0+ E647 2.16

3-3 -Aug. 8- 1.0+ m621-639, 5.17 

e640

Top of ejecta rampart 

NE. of dome.

Near top of the Stairsteps at 5,180-ft 

elevation, western 

tongue.

30 and 40 m from distal end of western 

tongue.

Profiles at six sites and single measurement at one other site along E. 

and NE. top of ejecta rampart adjacent to the August dome; 

temperatures to 1 m by direct insertion of thermocouples, temperatures between 1.0 and 2.65 m in pipes; pipes could not be 

driven below 2-2.65 m; measurements lie between two profiles 

that were essentially isothermal (725 and 830°C) below 1.5 m.

Deposit less than 1 m thick, with medial and lateral levees to 2 m 

thick; temperature profiles by direct insertion of thermocouples 

at three sites (two in levees) and single measurements at several 

depths at two other sites (one in a levee); isothermal in thickest 

levee at 1-1.5 m, other temperatures parallel this profile but are 

100-150°C cooler. Measurements taken 20 hours after emplacement.

Deposit about 2 m thick; profiles at two sites by direct insertion of 

thermocouples; nearly identical readings at both sites; steep 

gradients between 0.5 and 1.5 m. Measurements taken 18 hours 

after emplacement.
30 DIRECT TEMPERATURE MEASUREMENTS OF DEPOSITS, MOUNT ST. HELENS, WASHINGTON, 1980-1981

122°14' 13' 121 122°08'

EXPLANATION

Pyroclastic flows 

of August 7

8-3, Temperature station number

Temperature (in degrees C) 

Measured emplacement

850 ® Calculated emplacement 

0 2 KILOMETERS

I___________________I

CONTOUR INTERVAL 400 FEET
TEMPERATURE OF THE DEPOSITS 31

TABLE 10. Temperatures of deposits of the pumiceous pyroclastic flows of October 17, 1980 

[Stations: U, upper flow (2112 P.d.s.t.); L, lower flow (0928 P.d.s.t.). Temperatures: e, estimated emplacement; m, minimum]

Station Date (1980) Depth Temperature ^stance Locality 

(fig. 25) (m) (°C) r VAn

Remarks

10-1U- Oct. 22 

10-2U - Oct. 19 

10-3U - Oct. 18 

10-4U Oct. 18 

10-4L - Oct. 17 

0.10

0.43

0.50

0.40

1.00

m849

m730

m684

m567

m457, e465

0.24

0.70

2.04

4.32

4.34

South of dome -

100-200 m N. of

ejecta rampart.

Top of the stairsteps.

Base of the stairsteps.

....do ------ 

Single measurement.

Deposit about 1.5 m thick, partial profiles (2-3 measurements) at 3 sites

describe steepening but relatively shallow gradient.

Deposit 0.4-1.5 m thick, profiles and partial profile at one site and

several partial profiles at another site do not describe a recognizable

average profile; measurements taken 13 hours after emplacement.

Terminus of flow, about 1 .5 m thick; four profiles by direct insertion of

thermocouples; no isothermal segments. Measurements taken 14

hours after emplacement.

15 m from terminus of flow; 1.3 m thick, with very low ratio of matrix to

lapilli; profiles by direct insertion of thermocouple to 1 m at five

sites; profiles describe parabolic curves, with segments approaching

isothermal. Measurements taken 5 hours after emplacement.

I FIGURE 23. Sketch map of Mount St. 

Helens area, showing distribution and 

emplacement temperatures of deposits of 

pumiceous pyroclastic flow of August 7. 

Geology after Rowley and others (1981, 

fig. 295).

FIGURE 24. Installation of temperature station on vent rampart of August 7 

eruption. View southward.

emplacement temperature of about 465°C (fig. 25; table 10; 

also see fig. 37A and tables in appendix 2). Hazardous conditions nearer the vent and burial of the 0928-P.d.s.t. unit during 

the 2112-P.d.s.t. eruption prevented determination of the 

downflow variation in emplacement temperature.

Although measured within 14 hours of emplacement, profiles at two stations in the 2112-P.d.s.t. unit were too shallow to 

obtain isothermal segments. The data do suggest, however, that 

the 2112-P.d.s.t. unit was emplaced at temperatures at least 

200°C higher than the 0928-P.d.s.t. unit.

Temperatures measured in near-vent deposits of the 2112- 

P.d.s.t. unit were several hundred degrees higher than those 

measured in the downflow deposits 2 days before. The highest 

vent-facies temperature was 849°C, almost identical to temperatures measured in the August 7 vent-facies material.

In January 1981, temperatures of 765 to 778°C (Jan. 1) 

and 785°C (Jan. 19) were measured at depths of 1 to 3 m in new 

cracks that opened in the pyroclastic deposits within the crater. 

No other cooling data were collected on the October 17 deposits.

OTHER TEMPERATURE DATA

Persistent fumaroles emitted superheated steam from fissures near and along the base of the east and south walls of the 

crater throughout 1980 after the May 18 crater-forming event. 

On August 25, temperatures measured at depths of I m in these 

fumaroles ranged from 133 to 145°C. The water vapor condensed about 1 to 2 m above the orifices of the fumaroles. There 

was no odor of H2S or SO2 in the steam and very little deposition of sulfur sublimate around the fumaroles.
32 DIRECT TEMPERATURE MEASUREMENTS OF DEPOSITS, MOUNT ST. HELENS, WASHINGTON, 1980-1981

122°14' 13' 122°08'

EXPLANATION

nyroclastic flows 

of October 17

10-3U, Temperature station number; 

L, lower flow; U, upper flow

Temperature (in degrees C) 

457,QN Estimated emplacement 

465 and minimum

684 + Minimum emplacement

CONTOUR INTERVAL400 FEET
SUMMARY AND DISCUSSION 33

Following the August 7 eruption, the vent area consisted 

of a steep-walled depression whose floor was composed largely 

of a small dome. Several attempts were made in early September 

1980 to assess whether the depression could be safely entered 

to collect rock and gas samples. Measurements were done with 

the prototype short-lived, aerially emplaced, radio-linked 

penetrators (type B; see fig. 26P and appendix 1) and by lowering of metal strips coated with temperature-sensitive paints into 

the crater.

The probe was dropped by helicopter on September 4, 

1980, about midway between the dome and the wall of the dome 

crater. It landed as intended on a tephra deposit around an inactive vent at the west base of the dome. The upper thermocouple 

junction stopped 30 cm above, and the lower thermocouple junction stopped 30 cm into, the tephra deposit. The lower thermocouple was encased in 1 '/2-in.-diameter pipe, with the tip a few 

millimeters below the surface of the pipe. Thus, the temperature of about 300°C recorded by the buried thermocouple at the 

end of the maximum recording period at the receiver (8 minutes) was well below the actual temperature of the deposit because of the high thermal inertia of encasing pipe. Likewise, 

the temperature of 85°C registered at the upper thermocouple 

(encased in a 2-in. pipe) was even farther below the actual temperature of the atmosphere in the crater. Extrapolation of the 

time-temperature response of this upper thermocouple indicates 

that the atmospheric temperature at the exposed thermocouple 

exceeded 200°C.

On September 8, 1980, an attempt was made, using metal 

strips coated with temperature-sensitive ceramic paints (see fig. 

26M and tables in appendix 2), to determine temperatures in 

glowing cracks in remnants of the June 12 dome, which had 

become vertical walls of the dome crater. The metal strip was 

lowered by cable past a crack, left hanging for 15 minutes in 

the crater near, but not against, the gray walls, raised for a 1- 

minute pause against the glowing crack, and then recovered. 

Paints with melting points as high as 343 °C had been vaporized 

from the metal, and paints with melting points as high as 649°C 

but below 704°C had been melted.

Temperatures of 888 and 897°C were measured by Terry 

Leighley and Don Swanson on March 9, 1981, at depths of 15 

and 50 cm, respectively, in a crack of the February 1981 dome. 

These temperatures are only about 100°C below the average 

temperature suggested by Melson and others (1980) and Melson 

and Hopson (1981) for the crystallization temperature at depth 

of Fe-Ti oxides in magma. Temperatures measured on the dome 

in 1982-1984 by Don Swanson (oral commun., 1984) exceeded 

900°C.

I FIGURE 25. Sketch map of Mount St. Helens area, showing distribution 

and temperatures of deposits of pumiceous pyroclastic flows of October 

17. Geology after Rowley and others (1981, fig. 295).

SUMMARY AND DISCUSSION

GENERAL

Emplacement temperatures were measured in most of the 

major flow deposits from the 1980 Mount St. Helens eruptions. 

In addition, specialized temperature-measuring equipment and 

methodologies were developed to maximize efficiency in data 

collection and to minimize risk to personnel.

Measurements were obtained both down and across the 

paths of flows; temperature-depth profiles were obtained at most 

stations. Many of these profiles were repeatedly measured to 

establish cooling histories of the deposits and to provide data 

for mathematical recovery of inplace thermal properties and 

additional emplacement temperatures (Ryan and others, 1981, 

1990).

Emplacement temperatures for the debris avalanche of 

May 18 show a 30°C downflow decrease from about 98 to 68°C. 

These relatively low temperatures can be attributed to the fact 

that the bulk of the deposit is composed of old flank rocks which 

probably were heated to temperatures near the boiling point of 

water by the geothermal system in the volcano. Emplacement 

temperatures (96-325°C) of the ponded deposits of the blast 

generally were lower than those of the following pumiceous 

pyroclastic-flow deposits of May 18 through October 17. Emplacement temperatures of the pumiceous pyroclastic-flow deposits of May 18, June 12, July 22, August 7, and October 17 

ranged from about 300 to 730°C, and temperatures in vent fades ranged up to 850°C. Most of the eruptions produced more 

than one flow unit, and some of these units showed thermal 

stratigraphy. Emplacement temperatures were not obtained on 

deposits of the May 25 eruption, most of the early depositional 

unit of July 22, or the late unit of October 17.

IMPORTANT FEATURES OF TEMPERATURE DATA FROM

PYROCLASTIC-FLOW DEPOSITS PRODUCED BY THE BLAST OF

MAY 18,1980

The most important features of the data obtained from 

the deposits produced by the blast, and our interpretations of 

these features, are summarized here.

1. In general, in comparison with deposits emplaced 

by the subsequent pumiceous pyroclastic flows, emplacement 

temperatures of the deposits produced by the blast were relatively low.

The relatively low emplacement temperatures of the blast 

deposits can be attributed to two causes. First, a significant fraction of the blast deposit is nonjuvenile. This nonjuvenile material was derived from the former north flank of Mount St. Helens 

and must have been at a much lower temperature than the juvenile component when the blast was initiated. Second, air-cooling must have been an important process, at least early in the 

blast, as the lateral explosion caused ejecta and air to mix.
34 DIRECT TEMPERATURE MEASUREMENTS OF DEPOSITS, MOUNT ST. HELENS, WASHINGTON, 1980-1981

Several data suggest that air was a significant and possibly the dominant gaseous component of the blast cloud. Persons who were engulfed by the cloud and survived (Rosenbaum 

and Waitt, 1981) reported that they could breath; most did not 

recognize any other gases. In addition, Eisele and others (1981; 

and oral commun., 1981) found from autopsies that most of 

those that did not survive the blast died of pulmonary occlusion 

rather than from the effects of high levels of volcanic gases 

(CO, CO2, and sulfur gases). Finally, as indicated by its low 

vesicularity, the dacite from the cryptodome was probably not 

a major source of gas in the blast cloud.

2. In the western sector, between azimuths of 300° and 

320° from the vent, emplacement temperatures were relatively low. In the eastern sector, between azimuths of 40° 

and 70° from the vent, emplacement temperatures were relatively high. In the intervening sector, the emplacement-temperature pattern was transitional.

One possible explanation for the emplacement-temperature pattern is that the source material for the blast was thermally inhomogeneous and that this material was asymmetrically distributed by the blast. Before the blast, a temperature 

difference certainly existed between the cryptodome and the 

older rocks that constituted the north flank of the mountain. 

Furthermore, the cryptodome itself may have been thermally 

inhomogeneous. Fortuitous projection of hotter debris to the 

eastern sector thus may explain the observed emplacement-temperature distribution, although we have no independent evidence 

with which to test this possibility.

Another possible explanation may lie in differing terrains 

of deposition. The western sector consists largely of the open, 

rather unobstructed areas of the Castle Creek, Studebaker Creek, 

and North Fork Toutle River valleys. The eastern sector is composed of rugged terrain of high relief. The relief of the terrain in 

the intervening sector is transitional: the relief is moderate in 

the western part of the transitional sector and high in the eastern part. Either the changes in emplacement-temperature patterns fortuitously coincide with changes in terrain relief, or the 

terrain may have influenced the emplacement-temperature patterns.

Terrain could influence emplacement temperatures by 

controlling the volume of air incorporated by the blast cloud; 

rugged terrain of high relief would cause more air to be turbulently mixed with the hot density current than terrain of 

low relief. Heating of the air would expand the density current, and particles providing the heat would cool in accordance with their sizes and shapes. The expanding air would 

preferentially elutriate the finer (cooler) grains from the blast 

cloud, leaving a residuum of coarser (hotter) particles. Thus, 

mixing with air would cause opposing temperature effects 

in the blast cloud: cooling due to heat exchange, and effective heating due to preferential elutriation of fine particles. 

We do not have the quantitative data that support this alternative as the explanation or contributory mechanism to the 

hotter-eastward temperature distribution; however, in general, deposits in the eastern sector are deficient in fine grain 

sizes relative to deposits to the west.

3. In the western and northern sectors, emplacement 

temperatures exhibit little change with distance from the 

vent to distances as great as 20 km. In the eastern sector, 

emplacement temperatures may have increased with distance from the vent.

Conservation of heat along flow paths of pyroclastic 

flows is well documented in the literature. Smith (1963) suggested, on the basis of discrepancies between welding patterns in ash flows and those expected from theory, that most 

cooling results from mixing with air in eruption columns. 

Sparks and others (1978) reached the same conclusion on 

the basis of theoretical models. Suzuki (1962), using thermal paleomagnetic techniques, found near uniformity in 

emplacement temperatures as far as 26 km from the vent of 

the Shikotsu pumice flows in Japan.

There are several possible explanations for the uniformity 

of temperatures to such distances from the vent: (1) Incorporation of cold air was relatively unimportant along the path; (2) 

there was significant mixing with cold air along the entire path 

of flow, but essentially all interaction and heat transfer with 

cold air occurred at the head of the flow, as the cooler fines 

were elutriated to form an ash cloud and the hotter (coarser) 

material was deposited or incorporated in the overriding flow 

(see Wilson, 1980; Wilson and Head, 1981); and (3) heat was 

produced during the flowage as particles were abraded by collision with one another.

4. Temperature profiles at some localities indicate the 

presence of (at least) two depositional units possessing different emplacement temperatures.

Thermal stratigraphy was observed at three localities, each 

in thick pyroclastic-flow deposits in major valleys. After erosion of these deposits, multiple flow units became visible. These 

deposits clearly formed as debris flowed off of steep slopes and 

ponded in topographically low areas (Hoblitt and others, 1981). 

At thermal-stratigraphy localities the lower unit was hotter than 

the upper. At least at station 18 (Smith Creek), the thermal 

stratigraphy may be attributed in part to a grain-size effect; that 

is, we suggest that the lower units contained more coarse debris 

than the upper units and that the coarse debris had retained more 

of its heat during transport than the fine debris. Although the 

granulometric data necessary to apply the grain-size effect to 

the cooler-upward stratigraphy are absent at the other localities, a general feature of the blast deposits is that upper units 

tend to be finer grained than the units beneath them. Coolerupward stratigraphy may also have resulted from longer residence of the younger deposits as veneer deposits on the adjacent ridges before their secondary mobilization into the valleys.

5. Temperatures in the veneer deposits and moving 

blast cloud may have been higher than emplacement temperatures of the ponded pyroclastic-flow deposits.

Studies of the included wood and of wood and plastic 

exposed to, but not buried by, the blast suggest higher tempera-
SUMMARY AND DISCUSSION 35

tures within the moving blast material and veneer deposits than 

in the ponded deposits (Davis and others, 1980; Banks and 

Cutter, 1981; Banks and Hoblitt, 198la; Moore and Sisson, 

1981). Because many of the ponded deposits resulted from secondary mobilization of the veneer deposits, the higher temperatures in both the moving blast cloud and the veneer deposits are 

not unexpected.

IMPORTANT FEATURES OF TEMPERATURE DATA FROM

POSTBLAST PUMICEOUS PYROCLASTIC-FLOW DEPOSITS OF

MAY 18, MAY 25, JUNE 12, JULY 22, AUGUST 7, AND

OCTOBER 17,1980

The most important features of the data obtained from the 

postblast, pumiceous pyroclastic-flow deposits, and our interpretations of these features, are summarized here.

1. In general, pumiceous pyroclastic-flow deposits of 

May, June, July, August, and October were emplaced at progressively higher temperatures.

The increase in temperature accompanies general decreases 

in silica content (Lipman and others, 1981b), vesicularity (Kuntz 

'and others, 1981), and the volume of ejecta produced by successive eruptions (Rowley and others, 1981). Thus, instead of a progressive increase in magmatic temperature, the emplacement-temperature increases probably reflect the observed progressive 

decrease in the vigor of successive eruptions. A similar progressive decrease in eruptive vigor has been noted at several other historical eruptions and is generally attributed to a progressive decrease in the volatile content of the magma, although changing 

vent geometry might also contribute. Presumably, emplacement 

temperature is related to eruptive vigor because the ejecta looses 

heat primarily through mixing with air; more energetic eruptions 

will produce smaller fragments and will propel them to greater 

heights and involve larger volumes of ambient air.

2. Emplacement temperatures of the near-vent deposits were only 100 to 200°C lower than the probable magmatic temperature.

The relation of near-vent deposits to the pumiceous pyroclastic-flow deposits is uncertain. The near-vent deposits appear to 

contain a greater proportion of coarse material that is more angular 

and less vesicular than that contained in the flowage deposits. We 

interpret the near-vent material to be a lag facies of the flowage 

deposits or ballistic debris ejected during the closing moments of 

the eruptions. The near-vent material lost surprisingly little heat 

during transport: the near-vent deposits of the August and October 

eruptions were emplaced at about 850°C, about 50°C less than 

measurements obtained from dome cracks and about 140°C less 

than the probable magmatic temperature at depth (Melson and others, 1980; Melson and Hopson, 1981). The magnitude of this temperature drop is similar to that expected from adiabatic cooling of 

the ejecta (Sparks and others, 1978) in the absence of air cooling.

3. Most cooling of pumiceous pyroclastic-flow deposits occurred within several hundred meters of the vent; beyond this distance, individual flow units generally exhibited 

little variation in emplacement temperature.

Several hundred meters from the vent, the flowage deposits 

of August and October yielded temperatures about 200°C less 

than the near-vent measurements, and deposits of the more vigorous May 18 eruption were 400°C cooler, assuming similar 

temperatures for the near-vent deposits. The emplacement temperatures of the June and July deposits at this distance from the 

vent are not known. Along the remaining 2 to 6 km of the flow 

path, emplacement temperatures on individual flow deposits 

remained approximately uniform. Thus, most cooling occurred 

within several hundred meters of the vent.

We conclude that most heat transfer occurred near the vent 

as fountaining ejecta mixed with air. This mixture of ejecta and 

air spawned pyroclastic flows and pyroclastic surges (Hoblitt, 

1986). The importance of air-mixing is supported by the impressive elutriation clouds over the fresh deposits and analyses 

of gases collected from rootless fumaroles in them. Air was the 

overwhelming component in actively (some violently) venting 

fumaroles; magmatic gases became a significant but still subordinate component in only some of the fumaroles and only 

after the venting decreased to very low levels many days after 

emplacement (Casadevall and Greenland, 1981, p. 223).

Again our data confirm Smith's (1963) and Sparks and 

others' (1978) suggestions that most cooling results from mixing with air in eruption columns, and we suggest that one or 

more of the alternatives offered to explain the uniformity of 

temperatures along the flow path of the blast may also apply 

here.

4. All eruptions, except possibly that of May 25, produced multiple flow units; with the possible exception of the 

pumiceous deposits of May 18, different flow units were 

emplaced at different temperatures.

The different emplacement temperatures exhibited by individual flow units are attributable to a variation in eruptive vigor. 

Each eruption consisted of multiple eruptive pulses, some of which 

produced pyroclastic-flow units. If the vigor of successive eruptive pulses varied, the amount of ejecta fragmentation and the 

amount of air mixed with the ejecta varied. Thus, the emplacement 

temperatures of individual flow units varied.

5. Deposits from the ash clouds were cooler than deposits of the accompanying pyroclastic flows.

Emplacement temperatures of the ash-cloud deposits of May 

18 were significantly cooler than those of the pyroclastic-flow deposits, and the ash-cloud deposits of October 17 apparently were 

much cooler than their associated pyroclastic-flow deposits. Temperatures of individual clasts in some of the deposits were higher 

than those of the ash matrix that enclosed them. We attribute these 

relations to cooling of the pyroclastic material by admixed air, with 

the cooling rate of a particle being a function of its size. As ejecta 

mixed with air in the eruption fountain, small particles quickly lost 

heat as they underwent rapid thermal equilibration with the surrounding gas mixture. In contrast, large clasts cooled less before 

their incorporation into the pyroclastic flow.
36 DIRECT TEMPERATURE MEASUREMENTS OF DEPOSITS, MOUNT ST. HELENS, WASHINGTON, 1980-1981

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38 DIRECT TEMPERATURE MEASUREMENTS OF DEPOSITS, MOUNT ST. HELENS, WASHINGTON, 1980-1981

APPENDIX 1. TEMPERATURE MEASUREMENT TECHNIQUES, MOUNT ST. HELENS, 1980

INSTRUMENTATION AND TECHNIQUES

This section summarizes the instrumentation we initially 

used, the problems that sometimes beset our studies as they 

evolved, and the techniques and equipment that eventually 

yielded the best data in the safest, most efficient manner.

THE FIRST DAYS

On hand for the temperature studies were appropriate thermocouple meters and adapters, and a few flexible sheathed and 

beaded thermocouples (figs. 26A-E). We also had several short 

(30- to 100-cm), heavier gauge sheathed thermocouples. These 

supplies were suitable for temperature measurements in fumaroles and low-viscosity basalt lavas, but not in fresh pyroclastic-flow deposits because most of the thermocouples proved to 

be too short or too flexible to allow direct insertion to the depths 

required to obtain isothermal temperature profiles. However, 

we were able to obtain deep profiles by driving our one set of 

stainless-steel pipes into the deposits, allowing it to equilibrate 

thermally, and measuring the temperatures by stepwise insertion of a flexible thermocouple into the pipe (figs. 26F, G).

PIPE STATIONS

We obtained identical temperature profiles in thermally 

equilibrated pipe as by directly inserting the thermocouples into 

the ground (fig. 27). However, the pipe technique took about 4 

to 5 hours 3 l h hours for pipe equilibration and 5 to 10 minutes for thermocouple equilibration at each point on the profile 

(fig. 27). This limited the number of sites that could be measured in a single day to one or two, and many of the thinner 

deposits began to develop parabolic thermal profiles before they 

could be measured. This limitation, in turn, required even more 

time-consuming efforts of repeated profiling to obtain the data 

needed to recover the emplacement temperatures mathematically (Ryan and others, 1981, 1990).

To remedy these problems, we obtained a large supply of 

Vi-in.-diameter common plumbing pipes on the second day of 

the studies, 4 days after the May 18 eruption. With these pipes, 

we established permanent pipe stations that were left to equilibrate at many sites for measurement later in the day and during 

subsequent days and weeks. These permanent stations increased 

to three or four the number of temperature-depth profiles that 

could be obtained or remeasured in a single day.

PROBLEMS WITH PIPE STATIONS

To minimize air circulation, the permanent pipes were 

capped. The temperatures obtained at the bottom of pipes implanted in very thick (more than 20-m) deposits remained identical to the actual temperatures of the deposit for months (fig. 

28A). However, the fact that within 7 to 10 days, profiles measured in the upper sections of the permanent pipes became undercooled relative to the actual temperatures in the deposit (compare curves E and F, fig. 28A) emphasizes the need for caution 

in interpreting data from pipe stations left in deposits more than 

a week. This undercooling resulted from conductive and radiative heat losses from the exposed pipe and from cooling by steam 

formation and venting to the surface through the disturbed deposit adjacent to the pipe.

Pipe stations in thin (3- to 6-m-thick) deposits developed 

aberrant temperature-depth profiles much sooner than those in 

thicker deposits. Some aberrant bottom profiles in pipes that 

penetrated to or through the hotter, central part of a deposit could 

be observed on the day of implantation (compare curves B and 

E, fig. 285). Furthermore, the entire profile, not just the upper 

part, generally became undercooled within 7 to 10 days relative 

to the actual temperatures in the deposit (compare curve D with 

curves C and E, fig. 285). Profile aberrations also can occur at 

joints in the pipe (curve D, fig. 285).

The rapid undercooling and aberrant bottom and midsection profile shapes probably resulted from steam (from the lower, 

cooler part of the deposit) traversing the interior and exterior of 

the pipe. Thus, pipes inserted in thin deposits ceased to provide 

usable data much sooner than those implanted in thicker deposits.

OTHER EQUIPMENT

We also ordered various more appropriate commercial 

thermocouple supplies, with emphasis on sheathed 6-mmdiameter thermocouples (1 and 3 m long; fig. 26/f), spare 

thermocouple meters, and additional 1.5-mm-diameter flexible 

thermocouples. The new equipment arrived 16 days after the

,. FIGURE 26. Temperature-sensing equipment used in this study. 

Rulers are in inches. A, Flexible, 1.5-mm-diameter, Inconel-sheathed 

Chromel-Alumel thermocouple, as much as 10 m long. B, Heavy-gauge 

Chromel-Alumel thermocouple with ceramic-bead insulation, as much 

as 10 m long. C, Appropriate adapters. D, and E, Digital thermocouple 

meters. F, Pipe assembly of stainless steel, for deep penetration of 

deposits. G, Diagram illustrating pipe insertion into deposit. H, Heavygauge (6-mm-diameter) Inconel-sheathed Chromel-Alumel 

thermocouple, as much as 3 m long. /, Short (1-m long) multitipped 

thermocouple. J, Diagram illustrating insertion of permanent 

multitipped thermocouple string, t, thermocouple-junction tip. K, 

Anchor for thermocouple string. L, Permanent thermocouple string. 

M, Stainless-steel strip with temperature-sensitive paints. N, Stainlesssteel strip sandwiched between protective steel plates. O, Two painted 

stainless-steel strips in place along expected flow path of a pyroclastic 

flow. P, Prototype of aerially emplaced radio-linked type B 

thermocouple probe.
APPENDIX 1. TEMPERATURE MEASUREMENT TECHNIQUES, MOUNT ST. HELENS, 1980

£, : «» Q

39

E

PL.

 ,V>

H
40 DIRECT TEMPERATURE MEASUREMENTS OF DEPOSITS, MOUNT ST. HELENS, WASHINGTON, 1980-1981

C/3

|io2

Z 103 

5 104

106

B

'150 200 250 300 350 

TEMPERATURE, IN DEGREES CELSIUS

400

FIGURE 27. Time required for thermal equilibrium to be reestablished between 

a pyroclastic-flow deposit and an implanted pipe (curve A) and a 

thermocouple (sheathed, 6-mm diameter) inserted directly into deposit 

(curve B). Pipe (squares) and thermocouple (circles) were inserted 

simultaneously about 3 m apart, and thermocouple tip was at same depth 

in deposit as pipe (2 m).

paroxysmal eruption, and the sheathed 6-mm-diameter thermocouples proved to have sufficient rigidity to allow their direct 

insertion to depths of 3 m in most of the fresh deposits erupted 

in 1980 at Mount St. Helens. This ability increased the number 

of new temperature stations that could be established in one 

day to five or six about triple the number previously possible. 

The 3-m-long probes could be coiled repeatedly and easily for helicopter transport. Probes longer than 3 m were found 

to have no advantage because friction on the sheath and (or) 

layers of large pumice blocks (tops of buried reverse-graded 

pumiceous deposits) generally combined to limit the depth of 

insertion to no more than 3 m. Longer, but necessarily thicker 

and more rigid, commercial thermocouples likewise have no 

advantage because they are not readily available, are not easily 

coiled for transportation, and take too much time to equilibrate 

with the deposit. Thus, for the less penetrable deposits and for

100 200 300 

TEMPERATURE, IN DEGREES CELSIUS

400

Q_ 

LU 

O

50 100 150 200 

TEMPERATURE, IN DEGREES CELSIUS

FIGURE 28. Comparisons of temperature-depth profiles. A, Profiles in 

thick (more than 10-m) deposit of pumiceous pyroclastic-flow deposits 

of May 18. Curves A and B, 14 days after eruption: curve A by direct 

insertion of thermocouple, and curve B in thermally equilibrated pipe 

on the day implanted. Curves C and D, 17 days after eruption: curve 

C by direct insertion of thermocouple, and curve D in pipe. Curves E

and F, 94 days after eruption: curve E by direct insertion of thermocouple, 

and curve F in pipe. B, Profiles in 6-m-thick deposit of the blast of May 

18. Curves A and B, 6 days after eruption: curve A by direct insertion of 

thermocouple, and curve B in pipe. Curves C and D, 17 days after 

eruption: curve C, by direct insertion of thermocouple, and curve D in 

pipe. Curve E, 32 days after eruption, by direct insertion of thermocouple.
APPENDIX 1. TEMPERATURE MEASUREMENT TECHNIQUES, MOUNT ST. HELENS, 1980 41

deeper measurements (max 9 m), we continued to obtain profiles by implanting plumbing pipe and inserting the lighter gauge 

(1.5-mm-diam) thermocouples into the thermally equilibrated 

pipe.

TIME-EFFICIENT EQUIPMENT AND TECHNIQUES

The number of sites requiring periodic remeasurement 

increased with each new eruption, necessitating increased efficiency in our data collection. This increased efficiency was 

achieved by the use of continuously recording chart recorders 

at selected sites and the development of multijunctioned thermocouples of two types: (1) Rigid 1-m-long metal-sheathed 

thermocouples with junction tips at 1, 5, 10, 20, 30, 50, 75, and 

100 cm (fig. 267); and (2) flexible 10-m-long Teflon-sheathed 

thermocouples with junction tips at 1-m intervals along the string 

(figs. 26J, K).

All eight junctions of the 1-m-long multijunctioned metalsheathed thermocouples equilibrated and could be read within 

5 to 10 minutes of insertion (fig. 27). Previously, the measurement of such a 1-m-long profile through step-by-step insertion 

and equilibration of the thermocouple took 1 '/2 hours. Typically, 

we carried as many as five of these short multij unction units 

and inserted them in a row across the axis of flow of a deposit. 

In about 30 to 40 minutes, we could determine (1) the temperature variation across the flow at that locality, (2) whether the 

more time consuming, step-by-step profiling to greater depths 

was required to establish emplacement temperatures, and (3) 

the best site at which to continue a deeper profile.

The multijunction Teflon-insulated thermocouple strings 

were used in three modes: (1) Inserted into a pipe and removed 

after equilibrium had been reached and readings had been taken 

(10-20 minutes); (2) inserted and left (for remeasurement) in 

pipe that was filled with fine pyroclastic material, to minimize 

circulation of steam; and (3) implanted directly into a deposit. 

Direct implantation was accomplished by attaching the thermocouple string to a flared anchor (fig. 26L) that was loosely 

fitted to a pipe driven in by hammer. The anchor held the thermocouple string in place in the deposit while the pipe was extracted (fig. 267).

One advantage of the permanent Teflon-insulated thermocouples was that they only minimally disturbed the thermal 

regime of the deposit. Their disadvantage was the Teflon's low 

limit of thermal stability (it decomposes to toxic gases at about 

450°C). Thus, for deposits emplaced above 400°C, we used 

strings made of groups of 1.5-mm-diameter Inconel-clad thermocouples. As with the pipes, permanent insertion of the metalsheathed thermocouples caused abnormal upper temperaturedepth profiles, owing to rapid conduction of heat to the surface 

by the metal. However, this heat loss was much less in comparison with that in the permanently implanted pipes, particularly at depths below 2 to 3 m.

EXPERIMENTAL METHODS

AERIALLY EMPLACED THERMOCOUPLE PROBES

In late May, we began to develop (with Sandia Laboratories) aerially emplaced, radio-linked thermocouple probes so 

as to obtain early temperature data safely. The importance of 

early measurements was underscored by the experience we had 

in working with the relatively cool deposits of May 18 and 25. 

Immediate measurement in the deposit (1) eliminates the necessity of obtaining deep profiles or mathematical solutions from 

parabolic profiles and (2) provides temperature-depth profiles 

before thermal homogenization of the deposit and thus yields 

valuable data about the mechanisms of transport and deposition of the flow. Moreover, placement of the probes by air eliminated the hazards of sinking into hot inflated deposits and of 

extended exposure to potential subsequent flows.

The aerially emplaced probes were of two types: type A, 

a penetrator trailing a long string of thermocouples with a softlanding, long-lived transmitting package (fig. 29A); and type 

B, a relatively inexpensive, short-lived penetrator (figs. 26P, 

295). They enabled measurements to be taken close to the vent 

or in flows of all thicknesses immediately after their emplacement. Both types of aerial penetrators were designed to be 

dropped by helicopter at low altitudes and to transmit data directly to the helicopter.

The prototype of the type A probe was field tested with 

moderately successful penetration to 6 m in pyroclastic-flow 

deposits (fig. 29A). However, by mid-August and before the 

aerially emplaced prototypes could be mass produced, opportunities had been presented for walking on the ponded and 

unponded deposits of June 12, July 22, and August 7 very soon 

after their emplacement at 600 to 700°C.

Minutes after our arrival on the June 12 deposits, 10 hours 

after their emplacement, we learned that by use of snow gaiters, appropriate caution, and a rapid foot-patting of the surface 

before shifting weight onto the foot, we were able to traverse 

highly inflated flows (fig. 30). The foot-patting caused local 

degassing and enough local compaction of the deposit to allow 

the support of a person, much like standing in snowshoes on 

powdery snow.

However, when balance was lost or if a foot was placed 

on a large pumice clast that rolled under full weight, the next 

step commonly resulted in rapid sinking of one or more appendages until the compacting deposit set up enough to support 

the body weight. While this material set up adjacent to the body, 

however, it caused painful burns, some serious, and made selfextraction difficult.

Therefore, development of the short-lived, aerially 

emplaced probes (type B) continued, with the expectation that 

their presence in our equipment inventory would reduce hazards to personnel and allow earlier near-vent temperature measurements. Two 15-kg prototypes (fig. 26P) were field tested in 

early September (fig. 295). These devices had two thermocouples
42 DIRECT TEMPERATURE MEASUREMENTS OF DEPOSITS, MOUNT ST. HELENS, WASHINGTON, 1980-1981

*« " - itJ'

*- % ".-*

FIGURK 29. Air-dropped, radio-linked thermocouple probes. A, Air-dropped, 

long-lived, soft-landing probe (type A) in ponded deposits of June 12 

pyroclastic flow. Battery and transmitter lie next to buried probe. Tailcone stabilizer lies in lower right. View southward; Mount St. Helens in 

background. B. Short-lived probe (type B) implanted in deposits of August 

7 eruption by dropping from altitude of 100 m. Thermocouples (TC) were 

inserted into deposit next to probe to assess probe's thermal inertia.

placed at expected depths of penetration of 25 and 75 cm. The 

emplacement (in both hovering and flying mode), penetration, 

radio linkage, data recording, and data reduction on these prototypes met all our expectations.

The main shortcomings of the prototypes to the type B 

probe were their high thermal inertia, the limited length on the 

recording tape, and the short life of the transmitter battery. Together, these shortcomings did not allow equilibrium of the thermocouples before cessation of data acquisition. However, these 

shortcomings could be overcome by directly exposing the tips 

of thermocouples of low thermal inertia by using a breakaway 

anchor that pulls a coiled string of lightweight thermocouples 

from the surface transmitter platform into the deposit.

CERAMIC PAINTS

We also tried to measure temperatures in both freshly 

deposited and moving ash clouds (nuees ardentes) associated 

with the pyroclastic flows, expecting that such data might contribute to our understanding of the flow processes. Because these 

measurements could not be made safely in person, fences of 

stakes with temperature-sensitive ceramic paints were erected 

along the expected paths of future pyroclastic flows.

The paints (spanning the temperature range of 300 to 

900°C in about 50°C steps) were applied to stainless-steel strips 

over numbers stamped in the metal for identification (fig. 26M). 

The paints were protected from erosion by sandwiching the 

painted strip with a facing stainless-steel strip (fig. 26AO- One 

sandwich was bolted at ground level, and another at 1-m height 

on standard metal fence stakes (fig. 260).

The flows of August 7 failed to reach the stakes. However, pyroclastic flows of the October 17 eruption overran a 

newly emplaced array of stakes. As expected, most of the overrun stakes were buried or carried away. The paint on stakes that 

survived exposure to the ash clouds did not melt. Either the ash 

cloud was relatively cool (less than 300°C), or, less likely, duration of the exposure was insufficient for thermal equilibrium 

to take place. Subsequently, we redesigned the experiment, using material of lower thermal inertia. However, no subsequent 

ash flows occurred to test the experiment.

SUGGESTED PROCEDURES FOR FUTURE INVESTIGATIONS

The above-described modifications of our original equipment resulted in what we consider to be a basic equipment inventory for obtaining emplacement temperatures of pyroclastic-flow deposits (table 11). In addition, we found that the 

following strategy maximized the quality, quantity, and usefulness of temperature data obtained from deposits of pyroclastic 

flows. In practice, particularly in the early days of our studies,
APPENDIX 1. TEMPERATURE MEASUREMENT TECHNIQUES, MOUNT ST. HELENS, 1980 43

circumstances commonly prevented strict adherence to the strategy.

1. Early access should be gained.

2. For deposits less than a meter thick, measurements should begin 

within an hour of deposition, if possible, and not more than 

24 hours later. After 24 hours, all thin deposits probably will 

require measurement of temperature-depth profiles.

3. For lobate deposits, temperature-depth profiles should be 

measured at several sites perpendicular to the axis of the 

deposit in three or more places (distal, middle, and proximal), followed when possible by similar observations 

between these localities.

4. For radial or sheetlike deposits, the first profiles should be in the 

nonponded (veneer) deposits inward first from distal to 

middle, and then to proximal localities along at least three 

evenly spaced rays toward the vent. The next profiles should 

be measured first in the thinner and then in the thicker ponded 

deposits along these rays. If time allows, further measurements should be made, first in other thin veneer deposits, 

and later in any remaining ponded deposits. 

5. At sites visited too late to observe isothermal profile segments, obtain the thermal properties of the deposit or facilitate calculation of emplacement temperatures in the 

following manner: (1) Temperature-depth profiles must 

be obtained at least twice at the same site at times that are 

sufficiently separated to produce appreciably different 

profiles, and (2) the thickness of the deposit must be determined (Ryan and others, 1981, 1990). Thicknesses can 

be obtained by using a metal probe or acoustic profiler 

(see table 11), by waiting until the deposit is dissected by 

erosion, or, for thick deposits, by calculations using published preemplacement topographic information and calibrated altimeter readings. Multiple profile measurements 

in deposits that are thick or that harden quickly are facilitated by early implantation of strings of low-thermal-mass 

permanent thermocouples (table 11; figs. 26A, J).

FIGURE 30. Approach to distal ponded deposits of pyroclastic flow of June 12 (temperature 450-600°C), 14 hours after emplacement. View northwestward.
44 DIRECT TEMPERATURE MEASUREMENTS OF DEPOSITS, MOUNT ST. HELENS, WASHINGTON, 1980-1981

TABLE 11. Basic equipment for temperature measurements in pyroclastic-flow deposits

Equipment needed Number Remarks

Battery-powered digital thermocouple meter, 

adaptors, spare batteries.

1-m-long Chromel-Alumel Inconel-sheathed 

6-mm-diameter thermocouple with 6 

Inconel-sheathed 1.5-mm-diameter 

thermocouples.

3-m-long Chromel-Alumel Inconel-sheathed 

6-mm-diameter thermocouple.

20-m-long Chromel-Alumel Inconelsheathed 3-mm-diameter thermocouple.

1- to 1.5-m-long 3/4-in pipe, couplings, and 

caps.

Metal probe (1-m-long connecting sections) 

and seismic or acoustic profiler.

Strings of 10-m-long Teflon-insulated or 

Inconel-sheathed 1.5- to 3-mm-diameter 

thermocouple with junction tips atl-m 

spacing.

Temperature-sensitive paints, metal strips, 

cable, and stakes for deployment.

Aerially emplaced radio-linked penetrator 

with thermocouple tips placed at several 

depths along the probe; receiving 

equipment.

Several None.

3 to 5- Weld 1.5-mm thermocouples to large thermocouple 

with tips at 25, 50, 70, 80, 90, and 95 cm above 

the bottom of the large thermocouple.

Several None.

1 or more None.

Large supply None.

] Use probe or profiler to obtaithickness of deposit 

and to estimate optimum depth for thermocouple 

placement.

1 for each permanent Tool implanting anchor heads to fit loosely inside 

station. 3/4-in. pipe.

4 or 8 oz for each tern- Range of paints, 200-1,000°C in 50°C steps. Large

perature interval. number of strips and deployment hardware.

2 or more per flow Optional.
APPENDIX 2. MOUNT ST. HELENS TEMPERATURE DATA 45

APPENDIX 2. MOUNT ST. HELENS TEMPERATURE DATA

The following data sets present field measurements at 

stations on the blasts deposits of May 18 and on the pumiceous pyroclastic-flow deposits of May 18, May 25, June 12, 

July 22, August 7, and October 17, 1980. Most are temperature-depth profiles that describe the cooling histories of the deposits during 1980 and, in some cases, into 1981. Several stations are described without tabular data because only one or two 

temperatures were measured. Graphic presentation of the complete data sets is found in figures 31-37, prepared by N.G. 

Banks and Bobbie Myers, at the end of this appendix.

Unless otherwise designated, all temperatures were 

measured with Inconel-sheathed Chromel-Alumel or PtPt+Rh thermocouples inserted directly into the deposits. 

Readings were made by electronically compensated digital 

volt meters that were calibrated in the laboratory and checked 

with an electronic ice-point calibrator while in the field.

STATION 1. Upper part of 

Studebaker Creek, 1,265-m 

elevation

[Ponded deposit, thickness unknown 

but more than 4 m. All temperatures measured June 5]

Depth

(m)

0.01 

.05 

.10 

.20 -

.30 

.50 

.75 ..

1.0 .

1.5 ..

1.9 ......

Temperature (°C) 

18 days

5

9

13

on

o<

50

A"J

79.

Q^

TEMPERATURES OF DEPOSITS OF THE BLAST OF MAY 18,1980

(See figs. 3 and 14 for locations and fig. 31 for graphs of data)

STATION 2. Middle part of STATION 3. Upper east fork of Castle Creek, 1,160-m elevation

Studebaker Creek, 1,120-m 

elevation

[Ponded deposit, thickness unknown but 

more than 5 m. p, temperature in pipe 

implanted in deposit June 9. All temperatures measured June 9]

Depth 

(m)

0.01 

.05 

.10 .

.20 

.30 

.50 

.75 

1.0- 

1.5 

2.0 

2.3 

3.0 

A n

4.5 

Temperature (°C) 

22 days

Sitel

15

1 Q

- 20

- 32

- 36

~ 42

- 55

67

89

Site 2

16 

18 

20 

28 

35 

47 

60 

71 

75 

91p 

91 

95p 

96p 

96p

STATION 4. Upper east fork of Castle Creek, 1,100-m elevation

[Five sites equally spaced along 30-m traverse down valley. Ponded deposits, 

thickness unknown but more than 5 m. All temperatures measured June 9. 

Comment: Sites are upstream of station 5, no burning logs in deposit; data 

plot on profiles of stations 1 and 2 (east of this station)]

Depth

(m)

1.0 

1 s ............

Temperature (°C)

22 days

Site 1 Site 2 Site 3 Site 4

75 70 66 70

89

SiteS

70

[Five sites equally spaced along 30-m traverse down valley. Ponded deposit, 

thickness unknown but more than 5 m. All temperatures measured June 9. 

Comment: Sites are upstream of station 5, no burning logs in deposit; data 

plot on profiles of stations 1 and 2 (east of this station)]

Depth

(m)

1.0 

1.5 

Temperature (°C)

22 days

Site 1 Site 2 Site 3 Site 4 Site 5

68 68 69 70 70

82

STATION 5. Lower east fork of Castle Creek, 

1,040-m elevation

[Ponded deposit, thickness unknown but more than 5 m. p, temperature in pipe implanted in deposit. All temperatures measured June 9. Comment: Wide variation in temperatures may 

be due to heat generated by presence of many burning and burned 

logs in deposit at this locality]

Temperature (°C) 

22 days

Depth 

(m)

0.01 

.05 

.10 

.20 

.30 

.50 

.75 

1.0 

1.5 . 

t Q _____________

9 8 ............

Site 1, Site 2, 

in pipe, 2 m W. 

E. edge of of pipe 

drainage

24p

">1r>

41p 

48p 

64p 

84p

1 1 1r»

177p 115 

183p 195 

119p

Sin

Site 3, Site 4, 

8 m W. 50 m W. 

of pipe of pipe

-

83 94

-
46 DIRECT TEMPERATURE MEASUREMENTS OF DEPOSITS, MOUNT ST. HELENS, WASHINGTON, 1980-1981

TEMPERATURES OF DEPOSITS OF THE BLAST OF MAY 18, 1980 Continued

STATION 6. Upper reach of east fork of Jackson Creek, 1,020-m elevation. 

Rootless ponded deposit, 3.3 m thick. Temperature 67°C at 1 and 1.5 m, 

measured June 11.

STATION 7. Lower east fork of 

Jackson Creek, 635-m elevation

[Rootless ponded deposit, 1.5 m thick. 

Temperatures measured June 5 and 9]

Depth

(m)

0.01- 

.05- 

.10- 

.20- 

.30- 

.50- 

.75 - 

1.0 

1.15 

1.5 

Temperature (°C)

18 days 22 days

is i f\

17 20

"is "\(\

48 42

58 42

f'-J c -3

f*f\ *iQ

57

Soil

STATION 8. South fork ofHoffstadt Creek, 685-m elevation. Single measurements at several sites in ponded deposit, 3 m thick, upper 1 m water saturated. Direct insertion of thermocouple to 2.5 m; maximum temperature 

of 103°C, measured June 11.

STATION 9. Bench on north side of 

North Fork ofToutle River, south 

Coldwater Ridge, 1,035-m elevation

[Rootless ponded deposit, about 10 m 

thick. All temperatures measured June 

3. p, temperature in pipe implanted in 

deposit]

Depth 

(m)

0.01 

.05 

.10 

.20 

.50 

.75 .

1.0 

1.5 -

1.7 

2.7 

3.7 

4.2 

Temperature (°C) 

16 days

11

25

32

39

60

101

120

147

161p

179p

189p

190p

STATION 10 (U, L). Middle reach of South 

Coldwater Creek, 975-m elevation

[Two flow units in ponded sequence, thickness unknown 

but more than 5 m. Unit 10U overlies unit 10L, 

and both are stratigraphically younger than the unit 

at station 11. Sites 1 and 2 are in unit 10L, site 3 is 

in unit 10U. All temperatures measured June 9]

Depth

(m)

0.01 

.05- 

.15- 

.35 

.60- 

ss

1.0 

2.0 

2.5 -

3.0 

Temperature (°( 

22 days

Site 1 Site 2

- 20

- 20

OQ

IS

- 50

60

70 64

99

- 114

-)

Site 3

82

90

109

109
APPENDIX 2. MOUNT ST. HELENS TEMPERATURE DATA 47

TEMPERATURES OF DEPOSITS OF THE BLAST OF MAY 18, 1980 Continued

STATION UN. Lower reach of South Coldwater Creek; north pipe station, 775-m elevation

[Ponded deposit, thickness unknown but more than 5 m. p, temperature in pipe implanted in deposit on May 24; t, Teflon-insulated

permanent thermocouple]

Temperature (°C)

Depth 

(m)

0.01 

.05 

.10 

.20 

.30 

.50 

.70 

.75 . -

1.0 

1.5 .........

1 7 ............

2.0 

2 5 ............

2 7 ...

3.0 

3.5 ......

3.7 ......

4.0 

4.5 .........

4.7 ......

5.0 

5.5 

S 7

5 9 _____

May 23 

5 days l

11 

17 

25 

46

99

116 

120p 

126p

134p 

131p

99p

-

--

-

May 24 

6 days

21 

26 

31

51 

109

129 

139

138p 

138p

137p 

141p

141p 

137p

128p 

104p

98p

May 27 

9 days

17 

23 

28 

42

89

107 

109

140p

141p 

141p 

137p

109p

June 4 

17 days

28 

31 

33 

37 

43 

60

91 

106

137

141 

142

143 

lllp

HOp 

105p

105p 

lOOp

96p

June 8 

21 days

23 

24 

26 

32 

39 

58

88 

110

--

June 19

32 days

30 

34 

37 

45 

54 

70 

88t 

84 

94

119t

138t

138t 

133t 

127t

JulyS 

48 days

29 

30 

29 

32 

37 

49 

72t 

63 

70

116t

135t 

134t 

127t 

121t

Aug. 12 

86 days

31 

31 

32 

35 

39 

47 

63t 

56 

66 

94

102 

111 

119t 

116

123t 

118t 

115t

Oct. 7 

142 days

30 

29 

27 

29 

33 

39 

45t 

47 

54

103t 

lilt 

112t 

lilt

Dec. 16 

212 days

2 

6 

7 

10 

16 

22t 

22 

31

80t 

98t

104t 

106t

Temporary pipe, 100 m east of permanent pipe.
48 DIRECT TEMPERATURE MEASUREMENTS OF DEPOSITS, MOUNT ST. HELENS, WASHINGTON, 1980-1981

TEMPERATURES OF DEPOSITS OF THE BLAST OF MAY 18, 1980 Continued

STATION US. Lower reach of South Coldwater Creek; south pipe 

station, 775-m elevation

[Near south edge of ponded deposit, about 3 m thick, overlying deposit of the 

debris avalanche more than 80 m thick, p, temperature in pipe implanted in 

deposit on May 23]

Depth

(m)

o 01

.05 

.10 

.20 

.30 

.50 

.75- 

1.0 

i c

9 n

9 7

3.0 

May 23 

5 days

1 1

 - 17

 - 25

 - 49

 97

 116

 ~ 120

 106p

Probable base of blast 

3 5__ __ a-?..

4.5- 

4.6- 

5.0 

5.5- 

*'V

----- 97p

97p

Temperature (°C)

May 24 May 27 June 4 June 4 

6 days 9 days 17 days 17 days

17 25

20 29

24 31

34 32

37

91 87 53 86p 

106 84

108 95 98p 

- 107 98p 

126p 98p 102 98p

- - 97 98p

105p 97p 96 96p 

deposit; debris avalanche material below

97p 97p 96p

- - - 96p

- - - 96p

STATION 12. Coldwater I observation 

site, 925-m elevation

[Primary mantle deposit of blast, 0.75 m 

thick. All temperatures measured 

May 23]

Depth Temperature (°C) 

(m) 5 days

0.01 - 17

.05 - 25

.10- -

.20 

.30- 125

.50- 119

.75 5

Soil

STATION 13E. West fork ofShultz Creek, east pipe 33 mfrom 

east bank, 680-m elevation.

[Rootless ponded deposit, 3.2 m thick, p, temperature in pipe implanted in 

deposit May 27. Comment: Slumping of creek August 12 exposed an 

upper 0.5-m thick saturated zone above dry deposit]

Temperature (°C)

Depth

(m) May 27 June 4 June 24 Aug. 12 

9 days 17 days 37 days 86 days

0.01- 17 21 15 30

1f> 98 9Q 99 97

.20- 42 35 30 29

.30- 42 50 31

.50 100 65 48 36

.75 - 132 103 62 42

1.0 146 129 85 50

1.2 150 143 100

1.5 I44p 60

1.7 _ _ H8

2.0 148p 139 72

2

0 ino

2.5 149p 133 73 

3.0 145p 129

Oct. 7 

142 day;

29 

27 

24 

21 

22 

26 

29 

34

43

-

Soil
APPENDIX 2. MOUNT ST. HELENS TEMPERATURE DATA 49

TEMPERATURES OF DEPOSITS OF THE BLAST OF MAY 18, 1980 Continued

STATION 13W. West fork of Shultz Creek, west 

pipe 43 mfrom east bank, 680-m elevation

[Rootless ponded deposit, 3.2 m thick, p, temperature 

in pipe implanted in deposit May 27]

Temperature (°C)

Depth 

(m)

0.01 .

.05 

.10 

.20 

.30 

.50 

.75 .

1.00 -

1.1 ...

1.5 ...

7 o

T. 1 __ . ...

May 27 

9 days

17

- 22

- 27

42

- 97

- 130

- 146

- 150

- 143p

- 137p

1 ISn

May 28 

10 days

25 

32 

39 

48

90 

132 

144 

150

--

June 4 

17 days

21 

24 

28 

33 

40 

61 

99 

122

128 

110 

96 

92

STATION 14. Confluence of Bear 

Creek and west arm of Spirit 

Lake, 1,040-m elevation

[Ponded deposit, thickness unknown 

but more than 5 m. All temperatures measured June 11]

Depth Temperature (°C) 

(m) 24 days

0 OS -

.10 

90

.30 

.50 

.75 

1.0 

1.5 

2.0 

2.5 

3.0 

5.0 

16 

18 

22 

26 

34 

46 

68 

95 

105 

107 

109 

108

STATION 15N. Bench above Lang 

Mine; north pipe, 1,280-m 

elevation

[Ponded deposit, about 6 to 8 m thick. 

All temperatures measured June 3. 

p, temperature in pipe implanted 

in deposit May 24]

Depth Temperature (°C) 

(m) 16 days

0.01 - 

.05 

.10 -

.20- 

.30 

.50 

.75 -

1.0 

1 <

2.0 

2 5 __ 

3.0 

3.3 

^ i .... ....

15 

19

20 

24 

28 

42 

67 

93 

120 

131 

137 

142 

144p

lAAn

Soil
50 DIRECT TEMPERATURE MEASUREMENTS OF DEPOSITS, MOUNT ST. HELENS, WASHINGTON, 1980-1981

TEMPERATURES OF DEPOSITS OF THE BLAST OF MAY 18, 1980 Continued

STATION 15S. Bench above Lang Mine; south pipe, 1,280-m elevation

[Ponded deposit, about 6 to 8 m thick, p, temperature in pipe implanted in deposit May 22; t, Teflon-insulated permanent thermocouple. 

Comment: On August 8, deposit was difficult to penetrate at 0-1.3 m and 2.5-3 m but easily penetrated at 1.3-2.5 m]

Temperature (°C)

Depth 

(m)

0.01 - 

.05 .

.10 .

.20 .

.22 ------ 

.30 -

.50 .

.75- 

1.00 -

1.22 -

1.50 

2.00 

2.22- 

2.50- 

3.00 -

3.50 

4.00- 

4.22- 

4.50 -

5.00- 

5 22 ____ -

5 sn. __ .

May 22 

4 days

- 49

- 69

- 84

- 101

94p 

1 1 1«

- 118p

- 132p

- 146p

Q8n

May 24 

6 days

12 

16

23

86 

108 

128

133p 

139p

143p 

146p

147p 

146p

June 1 1 

24 days

5 

18 

26

31 

42 

56 

81 (95p)

118 

124 (95p)

137 

144 (96p)

lllp

June 19 

32 days

24 

26 

23 

23 

27t 

35 

35 

45 

57 

83t

126t 

148t 

129t 

83t

JulyS

48 days

20 

21 

19 

20 

22t 

24 

32 

41 

54 

75t

131t

140t

117t 

80t

Aug. 12 

86 days

26 

13 

22 

25 

26t 

29 

34 

40 

46 

59t 

73 

95 

106t 

106 

112 

119t

102t 

75t

Oct. 7

142 days

22 

21 

19 

18 

18t 

20 

24 

28 

33 

38t

77t 

93t 

87t 

71t

Dec. 10 

206 days

3 

5 

3t 

8 

11 

15

20t 

40t 

55t 

66t

60t

3/21/81 

307 days

2t

8t 

14t

19t 

22t 

20t
APPENDIX 2. MOUNT ST. HELENS TEMPERATURE DATA 51

STATION 16. Bench on northwest 

flank of Mount Margaret, 

1,530-m elevation

[Rootless ponded deposit, 2.9 m thick. 

All temperatures measured June 6]

TEMPERATURES OF DEPOSITS OF THE BLAST OF MAY 18, 1980 Continued

STATION 17. South fork of Green River, 

910-m elevation

[Rootless ponded deposit, 2.4 m thick. All 

temperatures measured June 8]

Depth 

(m)

0.01 

.05 

.10 

.20 

.30 

.50 

.75 

1.0 .

1.5 

o n

O 'N

2.9 .

Temperature (°C) 

19 days

15

on

O"3

29

 3 *~

51

67

99

152

150

106

67

Ice

Depth

(m)

0.01 

.05 

.10 

.20 

.30 

.50 

.75 

1.0 

1.25 

1.4 

1.5 

1.75 

1.9 

2.0 

2.4 

Temperature (°C) 

21 days

SSite

18

22 

24 

27 

37 

71 

106 

127

128 

123

98

51

N Site 1

21 

24 

28 

34 

51 

93 

130 

150 

148

131 

104

73 

38

N Site 2

24 

27 

31 

38 

59 

112 

155 

177 

174

166

151

136

Soil

STATION 18 (U, L). North side of 

lower west fork of Smith Creek, 

640-m elevation

[Rootless ponded deposit, thickness unknown but more than 5 m. p, temperature in pipe implanted in deposit 

June 6. Comment: Configuration of 

profile suggests upper unit U 

emplaced at 182°C and lower unit L 

emplaced at more than 248°C]

Depth 

(m)

0.01 

.05 -

.10 

.30 

.50 

.75 -

1.0 .

1.3 .

1 Q

O "3

o 0

4.3 .

4.8 .

5.3 .

Temperature (°C) 

19 days

on

30

^Q

-70

90

130

175

155p

1 QO«

100

200p

236p

248p

STATION 19. Lower part of main 

fork of Smith Creek, 560-m 

elevation

[Rootless ponded deposit, thickness 

unknown but more than 5 m. All 

temperatures measured June 9]

Depth

(m)

0.20 

T.f\ __

.50 .

.75- 

1.0 

1.5 

1 S

Temperature (°C) 

22 days

41

60

0*7

114

1 1Q

163

STATION 20. Upper main fork of 

Smith Creek, 880 m elevation

[Rootless ponded deposit, 2.7 m thick]

Temperature (°C)

Depth

(m)

0.01 

.05 -

.10 

on

orv

.50 

.75 .

1.5 

1.75 .

2.0 - 

-> fi» ____ .

June 8 

21 days

-- 20

OQ

IS

- 64

- 84

- 123

1 ^Q

i on

- 170

1 ^S

- 117

- inn

Aug. 12 

86 days

-

36 

35 

36 

49 

54 

56 

65

66 

63 

fi!

STATION 21. Middle reach of Bean Creek, 

745-m elevation

[Rootless ponded deposit, 2.93 m thick]

Temperature (°C)

Depth

(m)

0.01 

.05 

.10 

on

.30 

.50 

.75 

1.0 

1.5 

o n

2.5 

2.93- 

June 6 

19 days

22 

32 

42 

84 

119 

173 

224 

253 

277 

262 

214 

159

June 1 1

24 days

38 

50 

83 

110 

156 

222 

233 

256

-

Aug. 12 

86 days

41 

45 

52 

61 

77 

96 

109 

122 

118 

107 

93

Soil

Soil
52 DIRECT TEMPERATURE MEASUREMENTS OF DEPOSITS, MOUNT ST. HELENS, WASHINGTON, 1980-1981

TEMPERATURES OF DEPOSITS OF THE PUMICEOUS PYROCLASTIC FLOWS OF MAY 18,1980

(See fig. 16 for locations and fig. 32 for graphs of data)

STATION a. East side of amphitheater at top of stairsteps, 1,768-m 

elevation

[p, temperature in pipe implanted in deposit June 3. Comment: Station destroyed during June 12 eruption]

Depth

(m)

0.01 

.05- 

.10 

.20 

.30 

.50 

.75 

1 00

1.4 ..

1.5 

2.1 

1 *C

3.1 

3.4 .

3.9 

4.1 

5.1 

fi i _____ .

Temperature (°C)

June 3

10

i a

19

46

66

- 119

-- 159

- 196

010

- 418p

June 4

17 

24 

31 

46 

64 

103 

157 

191 

214

227p

264p 

317p

347p 

410p 

onor.

STATION b. Middle of north pyroclastic-flow apron, west side, 

1,110-m elevation

[p, temperature in pipe implanted in deposit June 1]

Temperature (°C)

Depth 

(m) May 3 1 

13 days

o ni

.05 - 

.10 

.20 

.30 

^n

7^

.90 - 

1.0 

1.5 330

o n

2.5 

2.8 

3.0 

3 3 _____

4.3 

5.3 

June 1 

14 days

16 

25 

68

173

310 

321

338p 

340p

341p 

342p 

341p 

332p

June 4 

17 days

23 

31 

39 

55 

69 

128 

215

273 

327

334p 

341p

342p 

341p 

339p 

338p

Aug. 20 

94 days

23 

22 

24 

31 

38 

60 

95

126 

173 

228

268 

281

302p 

322p 

328p

Dec. 8 

204 days

-

96p 

97p

98p 

97p 

97p

2/8/81 

266 days

96p 

96p

96p 

96p 

96p
APPENDIX 2. MOUNT ST. HELENS TEMPERATURE DATA 53

TEMPERATURES OF DEPOSITS OF THE PUMICEOUS PYROCLASTIC FLOWS OF MAY 18, 1980 Continued

STATION c. Middle of north pyroclastic-flow apron, west side, 

1,113-m elevation

[t, Teflon-insulated permanent thermocouple implanted in deposit 

June 24. Comment: Station destroyed by erosion January 1981]

Temperature (°C)

Depth 

(m)

0.01- 

.05- - 

.10 

.20- 

.30 

44 ____

.50- 

75 ____

1.0 ..

15 ... _

7 n

2.44- 

2.5 .

3 o _____

3 4<\

4 44 -

5 44 ____

June 24 

37 days

70t

181t

272t

311t 

324t 

325t

July 5 

48 days

24 

29 

33 

40 

49 

64t 

65 

88 

145 

224t

302t

322t 

326t 

326t

Aug. 20 

94 days

23 

24 

25 

32 

38 

47t 

49 

78 

114 

175t 

172 

230 

262t 

257 

287 

311t 

322t 

325t

Oct. 7

142 days

28 

31 

34 

37 

42 

49t 

52 

63 

74 

136t

234t

297t 

316t

323t

Dec. 8 

204 days

22

51 

94 

97t 

97 

97 

97 

97t

98t

99t 

290t 

314t

STATION d. Middle of north pyroclastic-flow apron, 1,125-m elevation. 

Temperature of 270°C at 1.5-m depth, measured May 31.

STATION e. Middle of north pyroclastic-flow apron, 1,125-m elevation. 

Temperature of 288°C at 1.4-m depth, measured May 31.

STATION f. Middle of north pyroclastic-flow apron, 1,080-m elevation

[p, temperature in pipe implanted in 

deposit May 27 and filled with ash]

Temperature(°C)

Depth 

(m)

0.30 

1.3 

2.3 

3.3 

4.3 

May 28 

10 days

149p 

297p 

296p 

290p 

270p

Dec. 10 

206 days

-

97p

STATION g. Middle of north pyroclastic-flow apron, 1,125-m elevation. Temperature of 297°C at 1.5-m depth, measured May 31.

STATION h. Middle of north pyroclastic-flow apron, east side, 1,190-m elevation in next flow unit up from, and 120 m south of, station i. Temperature 

of 305°C at 1.5-m depth, measured May 31.

STATION i. Middle of north pyroclastic-flow 

apron, east side, 1,130-m elevation

[p, temperature in pipe implanted in deposit May 30. 

Comment: Station destroyed by pyroclastic flows 

of June 12]

Temperature ('

Depth 

(m) May 3 1 

13 days

0.01 

.05 

.10 

.20 

.30 

.50 

.90 

1 n

1.5 342

1 g _____ 

2 3 _____

9 a

June 1 

14 days

28 

50 

65 

88

159

273

367p 

367p 

367p

D C)

June 4 

17 days

33 

52 

70 

89 

98 

124

299

350p 

361 p 

362p
54 DIRECT TEMPERATURE MEASUREMENTS OF DEPOSITS, MOUNT ST. HELENS, WASHINGTON, 1980-1981

TEMPERATURES OF DEPOSITS OF THE PUMICEOUS PYROCLASTIC FLOWS OF MAY 18, 1980 Continued

STATION j. Distal area of north pyroclastic-flow apron, 1,035-m elevation, over former position of Spirit Lake Lodge. Temperature 

of 307°C at bottom of phreatic crater, 30 m below surface of May 

18 flows, measured June 1.

STATION k. Distal area of north pyroclastic-flow apron, 1,005-m elevation, over former position of Spirit Lake Lodge. Temperature 

of 217°C at 1.5-m depth in ejecta blanket from phreatic crater in 

May 18 flows, measured June 1.

STATION 1. Distal area of north pyroclastic-flow apron, 1,000-m 

elevation. At top of phreatic crater, over former position of 

Spirit Lake Lodge. Temperature of 307°C at 1.5 m through 0.2 m 

of phreatic ejecta (1.3 m into surface unit of May 18 flows), measured June 1.

STATION m. Headwaters, South 

Coldwater Creek, 1,274-m 

elevation

[Ash-cloud deposit]

Depth

(m)

Temperature (°C)

May 30 June 6

12 days 19 days

0.01 -

.05 

.10- 

.20 

.30 - 

.50 - 

.75 

1.0 

1.5 

1.7 

2.0- 

7

12

28

36

51

77

108

137

137

 159

STATION n. Eastern pyroclastic-flow apron, Shoestring Glacier 

outwash, 1,189-m elevation. Deposit saturated with water and steam. 

Temperature of 97°C at 1-m depth in pipe, measured May 27.

TEMPERATURES OF DEPOSITS OF THE PUMICEOUS PYROCLASTIC FLOWS OF MAY 25,1980

(See fig. 18 for locations and fig. 33 for graphs of data)

STATION 25-1. On Forsyth Glacier, 

1,585-m elevation

[Rootless deposit, 2.7 m thick, p, temperature in pipe implanted in deposit. All temperatures measured 

May 31]

Depth 

(m)

0.01 

n<\

i n

.20 -

.50 

70

on

1.4 .

2.7 .

3.3 .. .

1 O

Temperature (°C) 

6 days

22

i s

41

51

156p

125p

STATION 25-2. Base of stairsteps, 

1,171-m elevation

[Rootless deposit, probably 2.5 m 

thick, p, temperature in pipe implanted in deposit. All temperatures meas-ured May 31. Comment: Station buried by June 12 

pyroclastic-flow deposits]

Depth

(m)

0.01 -

.05 

.10 

.20- 

.50 -

.70 

.90 -

1.1 -.

2.1 

9 ^ _____ .

Temperature (°C) 

6 days

21

40

y- ^

O-7

105

113

113p

155p

Firm; hrvttnm ( ?'*

3.0 131p 

3.6 132p
APPENDIX 2. MOUNT ST. HELENS TEMPERATURE DATA 55

TEMPERATURES OF DEPOSITS OF THE PUMICEOUS PYROCLASTIC FLOWS OF JUNE 12,1980

(See fig. 19 for locations and fig. 34 for graphs of data)

STATION 6-1. Base of 

stairsteps, 1,152-m elevation

[Uppermost flow unit. All temperatures measured June 14]

Depth Temperature (°C) 

(m) 2 days

0.05 - 

.10- 

.20- 

.30 

.50 

.75 - 

1.0- 

1.5_ 

1.75- 

2.0- 

118 

165 

250 

299 

345 

369 

381 

] 420 

387 

389

STATION 6-2. Terminus of west tongue, 

1,055-m elevation

[All temperatures measured June 13]

Pumice block(?)

Depth 

(m)

0.01 - -

.05 -- 

.10 -

.30 - 

.50 

.75 

1.0 ~

1.1 

1.3 

2.0 

Temperature (°C) 

14 hours

93

155

189

354

450 

552 

578 

602

fi09

£f\f~\

565

STATION 6-3. Southeast side of 

distal ponded deposits of 

northwest tongue, 1,021-m 

elevation

[Surface unit of ponded deposit. All 

temperatures measured June 14]

Depth 

(m)

0.01 

.05 

10

90

30 ___ -

.50 

.75 

1.0 

1.5 -

Temperature (°C) 

2 days

33

70

135

246

311

777

397

406

414

STATION 6-3C. Southeast side of 

distal ponded deposits of northwest tongue, 1,021-m elevation

[Terminus of coarse-grained late-flow 

unit overlying surface unit of ponded 

deposit. All temperatures measured 

June 14]

STATION 6-4A. 10 m northeast of south edge of 

center of distal ponded deposits of northwest 

tongue, 1,021-m elevation

STATION 6-4B. 20 m northeast of south edge of 

center of distal ponded deposits of northwest 

tongue, 1,021-rn elevation

Depth 

(m)

0.01 

.05 

.10 

.20 

.30 

.50 

.75- 

1.0 

i «

Temperature (°C) 

2 days

55

104

172

269

315

361

^61

361

1A1

Contact with flow unit c

1.5 100

9 n . . j.9 n

Temperature (°C)

Depth 

(m)

0 01

.05 

.10 

.20 

.30 

.50 -

.75 

1.0 

1.5 

2.0 

June 13 

10 hours

115 

174 

259 

374 

417 

436 

445 

461 

460 

462

June 14 

2 days

68 

122 

175 

270 

352 

414 

441 

461

Aug. 16 

65 days

28 

40 

53 

76 

102 

153 

268 

261 

340 

384

Depth 

(m)

0.01 

.05 

.10 

.20 

.30 

.50- 

.75 

1 0

1.5 

2.0 

Temperature (°

June 13 June 14 

1 0 hours 2 days

71

121

212

296

367

436

443

- 448

c,

Aug. 16 

65 days

T O

53

67

96

123

173

999

324

7QO
56 DIRECT TEMPERATURE MEASUREMENTS OF DEPOSITS, MOUNT ST. HELENS, WASHINGTON, 1980-1981

TEMPERATURES OF DEPOSITS OF THE PUMICEOUS PYROCLASTIC FLOWS OF JUNE 12, 1980 Continued

STATION 6-4C. 30 m northeast of south edge of 

center of distal ponded deposits of northwest 

tongue, 1,021-m elevation

Depth 

(m)

0.01 

.10 

.30 -

.50- 

.75 

1.0 

1.5 

2.0 

7 «

i n

Temperature (°

June 13 June 14 

10 hours 2 days

109

300 

371

c,

Aug. 16 

65 days

30

47 

60

117

1 <O

onA

259

328

391

446

STATION 6-4E. 50 m northeast of south edge of 

center of distal ponded deposits of northwest tongue, 1,021-m elevation

Temperature (°C)

Depth 

(m) June 13 

10 hours

n n^

10 .. .......

.20- 

in

.75 

1.0 

1.5 463

2.0 

3.0 493

June 14 

2 days

97 

179

248 

369 

430 

449 

451 

454 

464 

467

June 19 

7 days

58

136 

203 

260

345 

411 

445

STATION 6-4F. 53 m northeast of south edge of center of distal ponded deposits of northwest tongue,

1,021-m elevation

[p, temperature in pipe implanted in deposit June 19; pipe was destroyed by airwave in front of July 22 flow]

STATION 6-4D. 40 m northeast of south edge of 

center of distal ponded deposits of northwest 

tongue, 1,021-m elevation

Temperature (°C)

Depth 

(m) June 13 

10 hours

0 oi -

05 ....

.10 

.20 

.30 

.50 442 

.75 

1 5

1.8 493

2.0 

2.5 

3.0 

June 14 

2 days

138 

221 

327 

384 

435 

448 

457

Aug. 16 

65 days

28 

41 

57 

87 

116 

166 

217 

265 

327

387 

423 

446

Temperature (°C)

Depth 

(m)

0.01- 

.05 

.10 

.20 

.30 

.50 -

.75 

1.0 

1.3 .

1.5 .

1 O

2.0 -

2 3 ____ .

9 8

10-

1 o

4.3 -

4.8 .

5.3 -

June 14 

2 days

- 448

- 460

- 479

June 19 

7 days

81 

114 

175 

234 

328 

428 

439 

379p

438p 

461p

478p

487p 

490p 

493p 

495p 

496p

June 22 

10 days

_

103p

379p 

449p 

465p 

484p

488p 

483p 

485p 

483p

June 24 

12 days

28 

65 

89 

174 

246 

330 

400 

448

--

Aug. 16 

65 days

38 

50 

63 

89 

117 

165 

215 

262

333 

394

432

458

Aug. 26 

75 days

41 

48 

57 

85 

117 

161 

213 

260

325 

380 

419

444

-

Sep. 8 

81 days

24 

30 

36 

49 

68 

133 

192 

242

313 

389

-

-

Sep. 8 

88 days

35 

40 

43 

52 

62 

96 

168 

225

305 

359

-

Pumice block(?)
APPENDIX 2. MOUNT ST. HELENS TEMPERATURE DATA 57

TEMPERATURES OF DEPOSITS OF THE PUMICEOUS PYROCLASTIC FLOWS OF JUNE 12, 1980 Continued

STATION 6-5. Center of distal ponded deposits near end of northwest tongue, 1,021-m elevation

[Temperatures at 1.5-m depth and below measured with permanently installed string of 3-mm-diameter Inconel-sheathed 

thermocouples. First measurements August 5, made before equilibration of thermocouples with deposit]

Temperature (°C)

Depth 

(m)

0.01 - 

.05 -

.10 

.20 

.30 

.50 .

.75 -

1 n

1.5............

3.5 

4.5 ,

5.5---_. _.

6 5 ____ _

Aug. 5 

Aug. 6

55 days 

54 days 54 days

- 353 351 357 

. 446 475 492 

- 487 503 513 

- 513 521 526

- 531 533 535

Aug. 16 

65 days

38 

50 

63 

89 

117 

165 

215 

262 

354 

480 

513 

526 

534

Oct. 7 Nov. 1 1 

117 days 152 days

32 

39 

46 

55 

65 

81 

118 

182 

277 98 

464 442 

501 489 

521 514 

532 529

Dec. 8 

179 days

5 

51 

61 

88 

99 

99 

99 

99 

99 

122 

466 

522

2/8/81 

241 days

96 

98 

109 

112 

403

STATION 6-6. Near west end of distal ponded 

deposits of northwest tongue, 1,021-m elevation

[Temperatures at 1.5-m depth and below measured with 

permanently installed string of 3-mm-diameter 

Inconel-sheathed thermocouples]

Temperature (°C)

Depth 

(m)

0.01- 

.05 

.10 

.20 - 

i A

.50 

.75 

1.0 

1.5 

O A

3.0 

4.0 

5.0 

6.0 

Aug. 6 

55 days

~

~

--

367 

420 

487 

519 

536 

545

Aug. 16 

65 days

38 

50 

63 

89 

117 

165 

215 

262

417 

474

520 

538

Oct. 7 

117 days

32 

40

46 

55 

64 

81 

130 

189 

230 

351 

449 

498 

527 

542

STATION 6-7. Near terminus of Spirit Lake tongue, 

1,059-m elevation

[All temperatures measured 17 hours after emplacement, June 13]

Depth

(m)

0.05 

.30 

.50 

.75 .

1 5

1.9 . .

Site A

- 171

- 437

- 484

/IQQ

 l 422

Temperature (°C)

Site B Site C

488 495

488 495

SiteD

1 521

1 Pumice block(?)
58 DIRECT TEMPERATURE MEASUREMENTS OF DEPOSITS, MOUNT ST. HELENS, WASHINGTON, 1980-1981

TEMPERATURES OF DEPOSITS OF THE PUMICEOUS PYROCLASTIC FLOW OF 1825 P.cLs.t., JULY 22, 1980

(See fig. 22 for locations and fig. 35 for graphs of data)

STATION 7L-2. West tongue, 800 m north of base of 

stairsteps, 1,137-m elevation

[Thickness 1 to 2 m. All temperatures measured July 24]

Depth 

(m)

0.01 -

.05 

.10 

.20- 

.30- 

.50- 

.75 

10 

1.5-. ....

Temperature (°C) 

2 days

Site A

 - 65

 - 127

 - 351

 - 413

 - 391

 - 273

 196

SiteB

72

220 

348 

414 

381 

230 

189

SiteC

81 

144 

239 

377 

442 

410 

264 

194

SiteD

253

STATION 7L-6. 200 m southsouthwest of terminus of east 

tongue, 1,079-m elevation

[Thickness 2 m. All temperatures 

measured August 12]

Depth 

(m)

0.01 

.05 

.10 

.20- 

.30 

.50 

.75 

1.0 

Temperature (°C) 

21 days

44

60

77

111

i ao

230

264

STATION 7L-4. West side, middle of west tongue, 

1,110-m elevation

[Thickness, 1.5 to 2 m. All temperatures measured 18 hours after 

emplacement, July 23]

Depth 

(m)

0.05 

.10 

.20 

.30 

.50 

.75 

1.0 

Temperature (°C)

Site A

- 350

- 448

~ 434

-- 179

OOQ

SiteB

237 

319 

422 

424 

266 

173 

216

SiteC

267 

366 

481 

508 

395 

192 

182

SiteD

240 

338 

443 

448 

335 

175 

172

STATION 7L-7. Terminus of west tongue, adjacent to 

south edge of June 12 ponded deposits, 1,036-m elevation

[Terminus of west tongue, 0.8 to 1.5 m thick. All temperatures 

measured 16 hours after emplacement, July 23]

Depth 

(m)

0.01 

.05 

.10 

.20 

.30 

.50 

.55 

.75... ......

1.0- 

1 1 S

Temperature (°C)

Site A

- 47

81

-- 139

- 229

noa

- 289

9^0

SiteB

61 

88 

137 

220 

284 

304

263

253

SiteC

101 

143 

188 

250 

264 

253

190 

86

SiteD

-

320

-
APPENDIX 2. MOUNT ST. HELENS TEMPERATURE DATA 59

TEMPERATURES OF DEPOSITS OF THE PUMICEOUS PYROCLASTIC FLOW OF 1901 P.d.s.t., JULY 22,1980

(See fig. 22 for locations and fig. 35 for graphs of data)

STATION 7U-1. 700 m north of base of stairsteps, 1,146-m elevation

[Temperatures at sites A through D measured July 23; temperatures at sites E and F 

measured July 26]

Depth 

(m)

0.01 -

.05- 

.10- 

.15- 

.20- 

.25- 

.30 

.35- 

.45- 

.50 

.55- 

.65 

.75- 

OC

.95 

1,0 

1.05- 

1.1 

1.5 

1 Q

Temperature (°C)

22 hours 4 days

Site A SiteB SiteC Site D SiteE SiteF

 - 138 116 154 180 126

 - 257 231 272 276 203 196

 - 373 355 389 465 278

9QQ

 - 497 501 526 488 390

404

 - 560 569 592 547 464

479

C-31

 605 608 620 589 559

573

/£OO

 - 611 612 616 602 611 617

f\\~>

ftA'*.

 - 620 616 619 631 633

6^0

6<-j

ftftl

. 642 ~ - 1 705

1 f-r.

STATION 7U-3. Middle of north pyrodasticflow 1,000 m north of base 

of stairsteps, 1,127-m elevation

[Thickness, 2 m]

Temperature (°C)

Depth 

(m)

0.01 

.05 

.10 .

.20 

.30 

.50 

.75 .

10- 

1.5 

Aug. 16 

25 days

65

- 105

- 153

- 294

-- 397

-- 457

/tee

- 446

Sep. 4 

44 days

115 

270

Pumice block(?)
60 DIRECT TEMPERATURE MEASUREMENTS OF DEPOSITS, MOUNT ST. HELENS, WASHINGTON, 1980-1981

TEMPERATURES OF DEPOSITS OF THE PUMICEOUS PYROCLASTIC FLOW OF 1901 P.d.s.t., JULY 22,1980 Continued

STATION 7U-4 West side, middle of west tongue, 

1,110-m elevation

[Thickness, 1.5 to 2 m. All temperatures measured 20 hours 

after emplacement, July 23]

Depth 

(m)

0.05 

.10 

.15 

.20 

.30 

.50 

.60 

.70 

.75 

on

QO

1.0 

1.1 

1.2 

1 i ...........

Temperature (°C)

Site A

-- 313

- 412

^99

- 264

- 153

SiteB

603

639 

650 

660 

664

666 

661 

655 

630 

614

^£0

SiteC

271 

396

558 

631 

670

674

678 

674 

658 

fi/n

SiteD

341 

455

589 

646 

670

669 

676

STATION 7U-5. 300 m southsouthwest of terminus of east 

tongue, 1,082-m elevation

[Thickness, 2 m. All temperatures 

measured August 12]

Depth 

(m)

0.01 

.05 - 

.10 

.20 

.30- 

.50 

.75 

1.0 

Temperature (°C) 

21 days

Site A

42 

61 

100 

166 

220 

303 

373 

412

SiteB

43 

74 

114 

176 

227 

304 

362 

400

STATION 7U-6. 200 m southsouthwest of terminus of east 

tongue, 1,079-m elevation

[Thickness, 2 m. All temperatures 

measured August 12]

Depth 

(m)

Temperature (°C) 

21 days

0.01- 

.05- 

.10 

20-_____ 

.30- - 

.50- 

.75 

1.0 

78

112

152

210

267

354

421

468
APPENDIX 2. MOUNT ST. HELENS TEMPERATURE DATA 61

TEMPERATURES OF DEPOSITS OF THE PUMICEOUS PYROCLASTIC FLOW OF AUGUST 7,1980

(See fig. 23 for locations and fig. 36 for graphs of data)

STATION 8-1. North top ofejecta rampart around August dome, 1,902-m elevation STATION 8-2. First step down on stairsteps, 1,579-m

elevation, west tongue 

[Sites A, A', B, C, and D, top of ejecta rampart around vent: A, east side; A', inner rim of ejecta rampart

around vent, east side; B, 30 mN of Site A, east side; C, 60 mN of Site A; D, 90 m NW of site A. Site [Sites: A. center of westernmost of two adjacent lobes (1 m thick); 

E, 130 m NW of site A, top of dome rampart, N. 45° E. of dome center, p. temperature in pipes B, center of easternmost lobe; C, east levee of east flow; D, medial 

implanted in deposit August 13] levee of east flow; E, medial levee of east flow, second station. All 

____________________________________________________________ temperatures measured August 8, 20 hours after emplacement]

Temperature (°C)

Depth Temperature (°C)

(m)

Depth Aug. 13 Aug. 11 Aug. 13 Aug. 16 Site A SiteB SiteC Site D SiteE 

(m) 6 days 4 days 6 days 9 days

0.01 - 108 - - - 111 

Site A Site A1 SiteB SiteC Site D SiteE SiteE SiteE .(jj ~ ~ 2,2\) o i iyy

.10 -- -- - 223 276

0.01 - - - - - - 118

.05---- - 96 83 - - .15- 285

.10 ...... _ _ .. .. 76 _ .. .. -20- ~ " - " 386

. 15 - 210p 223 - - - 216 186 3° " ^ " 29° 48?

.20 - - - - - - - 336 - 35~--- 38°

.25 - - 362 - - - - 299 .50 - - 420 - 410 502

.30 - _...._ 483 444 - - 60 ~ 465

.35 - - - - 272 - - - - 75 " " - 44° 591

QC

.45 ........ - _ 550 - - - - 489

.50 - - - - - - - 603 - L0 " " "3 " ^

.55- - - - - - 705 - - 1 - 5 ---- " " 59° " ^

.60 - - - 641 673

.65 - 395p 473p -

.70- - _ 702 - - - - 667

.75 ------ 735 741

.95 - - 785 - - 777

, _ STATION 8-3. North of base of stairsteps, 1,134-m elevation,

1.15 595p 638p - - - - - - neardistal end of west tongue

1.5 - - - - - - 830p 820p

I g5_____ ,-m 7QI __ , [Sites; A, 30 m from distal end, center of

longest lobe; B, 40m from distal end,

2.15 710p - - i n medial levee. All temperatures

2.65 725p _ __- .. measured August 8, 18 hours after 

 emplacement]

Depth 

(m)

0.01 

.05 

.10 

.20- 

.30 

.50 

.75 

1 n ____ .

Temperature (°C)

Site A

250

327

407

500

544

567

573

^SQ

SiteB

153 

252 

350 

479 

517 

564 

591

fi'lQ
62 DIRECT TEMPERATURE MEASUREMENTS OF DEPOSITS, MOUNT ST. HELENS, WASHINGTON, 1980-1981

TEMPERATURES OF DEPOSITS OF THE PUMICEOUS PYROCLASTIC FLOW OF 0928 P.d.s.t. OCTOBER 17,1980

(See fig. 25 for locations and fig. 37 for graphs of data)

STATION 10-4L. Base of stairsteps, 1,150-m elevation.

[Thickness 1.3 m. All temperatures measured October 17, 5 hours after emplacement. Comment: Locality covered by ash flow of 2112 P.d.s.t. October 17]

Depth

(m)

0.05 

.10 

.15 

.20 

.30 

.45 

.50 

.70 .

.75 ,

.90 

1.0 

Temperature (°C)

Site A SiteB SiteC SiteD SiteE

osn

135

OSTQ O/I Q 11O OHO

211

'l/^T T3C OT1 T2/I

341

81

403 203 74 457

TEMPERATURES OF DEPOSITS OF THE PUMICEOUS PYROCLASTIC FLOW OF 2112 P.d.s.t. OCTOBER 17,1980

(See fig. 25 for locations and fig. 37 for graphs of data)

STATION 10-1U. 30 m south of October 17 dome, 1,910-m elevation. Temperatures measured at several sites on October 22; maximum measured, 

849°C at 0.1-m depth.

STATION 10-2U. 100 to 200 m north of ejecta rampart 

around dome, 1,830-m elevation

[All sites north of ejecta rampart: A, 170 m; B, 200 m; C, 230 m; 

D, 260 m. Thickness 1.5 m. All temperatures measured October 19]

Depth 

(m)

.25 - 

.32 

.33 

.41 . .

.43- 

Temperature (°C) 

2 days

Site A Site B Site C

550

345 - 553

600

f\f\~l

730

SiteD

565

555

^sn
APPENDIX 2. MOUNT ST. HELENS TEMPERATURE DATA 63

TEMPERATURES OF DEPOSITS OF THE PUMICEOUS PYROCLASTIC FLOW OF 2112 P.d.s.t. OCTOBER 17, 1980 Continued

STATION 10-3U. Top of stairsteps, 

approximately 1,660-m elevation

[Thickness 0.4-1.5 m. Profiles and partial profiles at 

two sites do not describe a recognizable emplacement temperature; maximum measured, 684C C. All 

temperatures measured October 18, 13 hours after 

emplacement]

Depth

-(m)

0.05 

.10- 

.20 

.30 

.40 

.45 

.50 - 

.55 

.60- 

.70 

.75 

Temperature (°C)

Site A Site B Site C

57 80

115 255

 "XQ

^S7

167

7QC

97 684 327

OS'7

TCS

STATION 10-4U. Base of stairsteps, 1,160-m elevation

[Thickness 1 to 1.5 m. Temperatures at sites A through C measured 

October 18; temperatures at site D measured October 24]

Temperature (°C)

Depth 1 4 hours 

(m)

Site A Site B Site C

0.05- -- 80

.10 251 145

.20- - 246 193

.30 - 402

.35 251 - 316

-40- - - ! 567

.50- - 504

.55- - -. 494

.60- 103 557

.80 - - - 479

i n - 147

7 days

SiteD

132 

295

428

519

Probable pumice block
64 DIRECT TEMPERATURE MEASUREMENTS OF DEPOSITS, MOUNT ST. HELENS, WASHINGTON, 1980-1981

0 20 40 60 80 100 

TEMPERATURE, IN DEGREES CELSIUS

O Station 3, all sites

n Station 4, all sites

T Station 5, pipe

o Station 5, near buried log

0 50 100 150 200 

TEMPERATURE, IN DEGREES CELSIUS

FIGURE 31. Temperature-depth profiles in deposits of the blast of May 18. 

Open symbols, data obtained from thermocouples inserted directly into 

deposit; filled symbols, data obtained in pipe thermally equilibrated with 

the deposit. A, Station 1, in ponded deposit in upper part of Studebaker 

Creek, 18 days after emplacement. B, Station 2, in ponded deposit in middle 

part of Studebaker Creek, at two sites 22 days after emplacement. C, 

Stations 3, 4, and 5, in ponded deposits in Castle Creek, 22 days after 

emplacement. Curve A defines probable emplacement temperature of about 

119°C at station 5. Many buried logs, both cold and burning, at station 5; 

points that plot off of curve A probably reflect proximity of probe tips to 

these logs. Curve B is reference curve from station 2, in next drainage to 

the east. Data from stations 3 (circles) and 4 (squares) were obtained upflow 

of station 5 and plot along curve B rather than curve A. D, Station 6 

(triangles, 24 days after emplacement), in ponded deposit in upper reach 

of Jackson Creek, and Station 7 (two curves), in ponded deposit in lower 

Jackson Creek. Curve A, 18 days after emplacement; curve B, 22 days 

after emplacement.

w

DCuj 2

UJ

o Site 1

n Site 2

 Site 2, pipe

B Station 2

0 20 40 60 80 100 120 

TEMPERATURE, IN DEGREES CELSIUS

-Soil, at Station 7

D

o A, Station 7

n B, Station 7

A Station 6

0 20 40 60 80 

TEMPERATURE, IN DEGREES CELSIUS
APPENDIX 2. MOUNT ST. HELENS TEMPERATURE DATA 65

o Station 9, direct 

 Station 9, pipe

0 50 100 150 200 250 

TEMPERATURE, IN DEGREES CELSIUS

Station 10 

C" o A, Sites 1 and 2

0 50 100 150 200 

TEMPERATURE, IN DEGREES CELSIUS

H Station 11S A

, I i I . I , I

0 30 60 90 120 150 

TEMPERATURE, IN DEGREES CELSIUS

50 100 150 

TEMPERATURE, IN DEGREES CELSIUS

FIGURE 31. Continued. E, Station 9, in ponded deposit on south side of 

south Coldwater Ridge, 16 days after emplacement. F, Station 10, in 

ponded deposit in upper part of South Coldwater Creek; three sites 22 

days after emplacement; curve A, 2 sites through upper and lower flow 

units (sta. 10U); curve B, in lower flow unit (sta. 10L); curve C, 

comparison profile downstream (sta. UN) in lower part of South 

Coldwater Creek. G, Station UN, in ponded deposit in lower part of 

South Coldwater Creek, north pipe. Curve A, 5 and 6 days after 

emplacement; curve B, 9 days after emplacement; curve C, 17 days 

after emplacement; curve D, 21 days after emplacement; curve E,

200

32 days after emplacement; curve F, 48 days after emplacement; curve G, 

86 days after emplacement; curve H, 142 days after emplacement; curve I, 

212 days after emplacement. Reversals in curves A and C result from 

cooling of pipe by steam (generated in base of deposit) that entered bottom 

and joints of pipe. H, Station US, in ponded deposit in lower part of 

South Coldwater Creek, south pipe. Curve A, 5 and 6 days after 

emplacement; curve B, 9 days after emplacement; curve C, 17 days after 

emplacement. Isothermal segments of curves are thought to indicate 

emplacement temperature of underlying deposits of debris avalanche.
66

0.5

1.0

DIRECT TEMPERATURE MEASUREMENTS OF DEPOSITS, MOUNT ST. HELENS, WASHINGTON, 1980-1981

0

Soil

Station 12

0 30 60 90 120 150 

TEMPERATURE, IN DEGREES CELSIUS

0 50 100 150 200 

TEMPERATURE, IN DEGREES CELSIUS

Station 15N 

Station 15N, pipe

0 25 50 75 100 125 150 175 

TEMPERATURE, IN DEGREES CELSIUS

0 50 100 150 200 

TEMPERATURE, IN DEGREES CELSIUS

CO 

£ 2

± 3 

nf

Q. 

LU 

Q 4

O

Station 14 

I , . I i

0 30 60 90 120 150 

TEMPERATURE, IN DEGREES CELSIUS

FIGURE 31. Continued. Temperature-depth profiles in deposits of the blast of May 18. 

Open symbols, data obtained from thermocouples inserted directly into deposit; filled 

symbols, data obtained in pipe thermally equilibrated with the deposit. I, Station 12, in 

primary mantle deposit of blast at Coldwater I observation site, 5 days after emplacement. 

J, Station 13E, in ponded deposit in west fork of Shultz Creek, east pipe. Curve A, 9 days 

after emplacement; curve B, 17 days after emplacement; curve C, 37 days after 

emplacement; curve D, 86 days after emplacement; curve E, 142 days after emplacement. 

K, Station 13W, in ponded deposit in west fork of Shultz Creek, 10 m west of east pipe. 

Curve A, 9 days after emplacement; curve B, 10 days after emplacement; curve C, 17 

days after emplacement. L, Station 14, in ponded deposit at confluence of Bear Creek 

and west arm of Spirit Lake, 24 days after emplacement. M, Station 15N, in ponded 

deposit in Lang Mine Creek above Lang Mine, north pipe, 16 days after emplacement.
APPENDIX 2. MOUNT ST. HELENS TEMPERATURE DATA 67

t

LU 

Q

0 50 100 150 200 

TEMPERATURE, IN DEGREES CELSIUS

CO

DC 

LU

0.5

1.0

1.5

2.0

2.5

o S Site

n N Site 1

A N Site 2

Soil

a cT Soil

Station 17

0 50 100 150 200 

TEMPERATURE, IN DEGREES CELSIUS

t

LU 

Q

0 40 80 120 160 

TEMPERATURE, IN DEGREES CELSIUS

FIGURE 31. Continued. N, Station 15S, in ponded deposit in Lang 

Mine Creek above Lang Mine, south pipe. Curve A, 4 days after 

emplacement; curve B, 6 days after emplacement; curve C, 24 days 

after emplacement; curve D, 32 days after emplacement; curve E, 

48 days after emplacement; curve F, 86 days after emplacement; 

curve G, 142 days after emplacement; curve H, 206 days after 

emplacement; curve I, 307 days after emplacement. Data obtained 

in pipe for curve A are anomalous because they were obtained before

CO

DC 

UJ

3 -

Q

18U

Flow contact (?) 

18L

Station 18 

Station 18, pipe

100 200 300

TEMPERATURE, IN DEGREES CELSIUS

pipe had equilibrated thermally with the deposit and because pipe was cooled 

by steam from base of the deposit. O, Station 16, in ponded deposit on northwest 

flank of Mount Margaret, 19 days after emplacement. P, Station 17, in ponded 

deposit in south fork of Green River, at three sites 21 days after emplacement. 

Q, Station 18, in ponded deposit on north side of west fork of Smith Creek, 19 

days after emplacement. Discontinuity in data is thought to represent a flow 

contact; upper unit (18U) emplaced at about 182°C and lower unit (18L) 

emplaced at higher than 248°C.
DIRECT TEMPERATURE MEASUREMENTS OF DEPOSITS, MOUNT ST. HELENS, WASHINGTON, 1980-1981

£ 1 LLI

Q. 

LU 

Q

R Station 19

0 50 100 150 200 

TEMPERATURE, IN DEGREES CELSIUS

Station 20

LLI

LLI

2

? 2

CL 

LLI 

Q

Soil

Station 21

0 50 100 150 200 

TEMPERATURE, IN DEGREES CELSIUS

FIGURE 31. Continued. Temperature-depth profiles in deposits of the blast 

of May 18. Open symbols, data obtained from thermocouples inserted 

directly into deposit; filled symbols, data obtained in pipe thermally 

equilibrated with the deposit. R, Station 19, in ponded deposit in lower 

part of Smith Creek, 22 days after emplacement. 5, Station 20, in ponded 

deposit in upper part of Smith Creek. Curve A, 21 days after emplacement; 

curve B, 86 days after emplacement. T, Station 21, in ponded deposit in 

Bean Creek. Curve A, 19 days after emplacement; curve B, 24 days after 

emplacement; curve C, 86 days after emplacement.

0 50 100 150 200 250 300 

TEMPERATURE, IN DEGREES CELSIUS
CO 

DC 

LJJ

LJJ

2 

I

LJJ 

Q

u

1 

2

3 

4 

5

6

7

^ei^. ' ' ' ' ' ' '

^So

 _ V. :

o A x ^'--.

 A, pipe \ '»

_ D B \ ' 

 B, pipe T 

\ A' - 

\

Debris avalanche contact (?) ^

A Station a

1 , 1 , I , ! ,

APPENDIX 2. MOUNT ST. HELENS TEMPERATURE DATA 69

100 200 300 400 500 

TEMPERATURE, IN DEGREES CELSIUS

100 200 300 400 

TEMPERATURE, IN DEGREES CELSIUS

FIGURE 32. Temperature-depth profiles in deposits of pumiceous 

pyroclastic flows of May 18. Open symbols, data obtained from 

thermocouples inserted directly into deposit; filled symbols, data 

obtained in pipe thermally equilibrated with deposit. A, Station 

a, on east side of amphitheater at top of stairsteps. Curve A, 16 

days after emplacement; curve B, 17 days after emplacement. Station 

was destroyed by a pyroclastic flow 25 days after emplacement. 

This profile is one of the least satisfactory of the study. Pipe kinked 

below the surface at several joints during implantation. Thus, when 

profile was first measured, the bends obstructed thermocouple 

penetration at 4 m. Next day, thermocouple was worked to 6-m 

depth, where a temperature reversal indicated that underlying 

deposits of debris avalanche had been penetrated. However, middle 

of profile shows a 70°C cooling within 24 hours of pipe insertion. 

No other data set shows such rapid cooling except where pipes 

penetrated through deposits and were cooled by steam (generated 

at or below base of hotter deposits) that traversed pipe-disturbed

CO 

DC 

LJJ tn s

o A

n B

 B, pipe

A C, pipe

v D

v D, pipe

* E and F

4

Station b

, , 1 , , 1 1 I I ! 1

0 100 200 300 400 

TEMPERATURE, IN DEGREES CELSIUS

u

1

CO 

DC 

LU

1 2

^

Q. 

LJJ 

Q

4

c;

1 ' 1 ' 1 ' 1 ' 1

"""* ^N

 A, pipe j

 B, pipe L

. D " Station f 

1.1,1,1,1. i

0 50 100 150 200 250 300 350 

TEMPERATURE, IN DEGREES CELSIUS

sediment or entered broken joints. Thus, curve A' is thought to show best 

interpretation of data, and discontinuity in the data at 2 m may represent a 

contact between an upper unit emplaced at 220°C and a lower unit emplaced 

at about 418°C. B, Station b, in middle of northern pyroclastic-flow apron, on 

west side. Point A, 13 days after emplacement; curve B, 14 days after 

emplacement; curve C, 17 days after emplacement; curve D, 94 days after 

emplacement; curves E and F, 204 and 266 days, respectively, after 

emplacement. C, Station c, in middle of northern pyroclastic-flow apron, on 

west side. Curve A, 37 days after emplacement, immediately after insertion of 

permanent thermocouple string; curve B, 48 days after emplacement; curve C, 

94 days after emplacement; curve D, 142 days after emplacement; curve E, 

204 days after emplacement. Curve A is anomalous because data were obtained 

before thermocouple had equilibrated thermally with the deposit. D, Station f, 

in middle of northern pyroclastic-flow apron, on west side. Curve A, 10 days 

after emplacement; point B, 206 days after emplacement. Slight temperature 

reversal with depth may be result of steam entering bottom of pipe.
70 DIRECT TEMPERATURE MEASUREMENTS OF DEPOSITS, MOUNT ST. HELENS, WASHINGTON, 1980-1981

100 200 300 400

TEMPERATURE, IN DEGREES CELSIUS

FIGURE 32. Continued. Temperature-depth profiles in deposits of pumiceous 

pyroclastic flows of May 18. Open symbols, data obtained from 

thermocouples inserted directly into deposit; filled symbols, data obtained 

in pipe thermally equilibrated with deposit. E, Station i, in middle of 

northern pyroclastic-flow apron, on east side. Point A, 13 days after 

emplacement; curve B, 14 days after emplacement; curve C, 17 days after 

emplacement; station destroyed by pyroclastic flows 25 days after 

emplacement. F, Station m, at headwaters of South Coldwater Creek. Point 

A, 12 days after emplacement; curve B, 19 days after emplacement. 2.5

25 75 100 125 150 175

TEMPERATURE, IN DEGREES CELSIUS

o Station 25-1

 Station 25-1, pipe

May 18 deposit

May 25 deposit

A

o Station 25-2

 Station 25-2, pipe

May 18 deposit

B

May 25 deposit

0 50 100 150

TEMPERATURE, IN DEGREES CELSIUS

200 0 50 100 150

TEMPERATURE, IN DEGREES CELSIUS

200

FIGURK 33. Temperature-depth profiles in deposits of pumiceous 

pyroclastic flows of May 25. Open symbols, data obtained from 

thermocouples inserted directly into deposit; filled symbols, data

obtained in pipe thermally equilibrated with deposit. A, Station 25-1, 

on Forsyth Glacier below Sugar Bowl, 6 days after emplacement.. 

B, Station 25-2, at base of stairsteps, 6 days after emplacement.
APPENDIX 2. MOUNT ST. HELENS TEMPERATURE DATA 71

Station 6-1

DC 0 100 200 300 400 500 LII

uj 0

Station 6-3

100 200 300 400 500

100 200 300 400 500 

TEMPERATURE, IN DEGREES CELSIUS

FIGURE 34. Temperature-depth profiles in deposits of pumiceous 

pyroclastic flows of June 12. Open symbols, data obtained from 

thermocouples inserted directly into deposit or from permanent Inconelsheathed thermocouples implanted in deposit 54 days after 

emplacement; filled symbols, data obtained in pipe thermally 

equilibrated with deposit. A, Station 6-1, at base of stairsteps, in 

youngest flow unit, 2 days after emplacement. B, Station 6-2, at 

terminus of west tongue, 14 hours after emplacement. C, Station 6-3, 

at southeast side of ponded deposits of northwest tongue, 2 days 

after emplacement. D, Station 6-3C, at terminus of late coarse-flow

c/D

CC 

LU

111

0 100 200 300 400 500 600 700 

TEMPERATURE, IN DEGREES CELSIUS

Observed flow contact

\ Coarse flow

Finer-grained flow

D Station 6-3C

100 200 300 400 500

0 100 200 300 400 500 

TEMPERATURE, IN DEGREES CELSIUS

lobe at Station 6-3, 2 days after emplacement. E, Station 6-4A, 10 m 

northeast of south edge, near center of ponded deposits of northwest 

tongue. Curve A, 10 hours after emplacement; curve B, 2 days after 

emplacement; curve C, 65 days after emplacement. F, Station 6-4B, 

20 m northeast of south edge, near center of ponded deposits of northwest 

tongue. Point A, 10 hours after emplacement; curve B, 2 days after 

emplacement; curve C, 65 days after emplacement.
72 DIRECT TEMPERATURE MEASUREMENTS OF DEPOSITS, MOUNT ST. HELENS, WASHINGTON, 1980-1981

100 200 300 400 

TEMPERATURE, IN DEGREES CELSIUS

500

Flow contact

Station 6-4E -

600

100 200 300 400 500 

TEMPERATURE, IN DEGREES CELSIUS

600

0 100 200 300 400 500 600

100 200 300 400 500 

TEMPERATURE, IN DEGREES CELSIUS

FIGURE 34. Continued. Temperature-depth profiles.in deposits of pumiceous 

pyroclastic flows of June 12. Open symbols, data obtained from thermocouples 

inserted directly into deposit or from permanent Inconel-sheathed 

thermocouples implanted in deposit 54 days after emplacement; filled symbols, 

data obtained in pipe thermally equilibrated with deposit. G, Station 6-4C, 

30 m northeast of south edge, near center of ponded deposits of northwest 

tongue. Point A, 10 hours after emplacement; curve B, 2 days after 

emplacement; curve C, 65 days after emplacement. H, Station 6-4D, 40 m 

northeast of south edge, near center of ponded deposits of northwest tongue. 

Points A, 10 hours after emplacement; curve B, 2 days after emplacement; 

curve C, 65 days after emplacement. /, Station 6-4E, 50 m northeast of south 

edge, near center of ponded deposits of northwest tongue. Points A, 10 hours 

after emplacement; curve B, 2 days after emplacement; curve C, 7 days after 

emplacement. J, Station 6-4F, 53m northeast of south edge, near center of

ponded deposits of northwest tongue. Curve A, 2 days after emplacement; 

curve B, 7 days after emplacement; curve C, 10 days after emplacement; 

curve D, 12 days after emplacement; curve E, 65 days after emplacement; 

curve F, 75 days after emplacement; curve G, 81 days after emplacement; 

curve H, 88 days after emplacement. Upper readings in pipe of curves B and 

C (which plot together as filled star off curves) reflect surficial cooling of 

pipe. FC?, probable flow contact. K, Station 6-5, at center of distal ponded 

deposits near end of northwest tongue. Curve A, 55 days after emplacement; 

curve B, 65 days after emplacement; curve C, 117 days after emplacement; 

curve D, 152 days after emplacement; curve E, 179 days after emplacement; 

curve F, 241 days after emplacement. L, Station 6-6, near end of distal 

ponded deposits of northwest tongue. Curve A, 55 days after emplacement; 

curve B, 65 days after emplacement; curve C, 117 days after emplacement.
APPENDIX 2. MOUNT ST. HELENS TEMPERATURE DATA 73

* FIGURE 34. Continued. M, 

Station 6-7, near terminus of 

northeast tongue, at four sites 17 

hours after emplacement.

o Site A

D Site B

* Site C

v Site D

M

Pumice blocks

Station 6-7

100 200 300 400 500 

TEMPERATURE, IN DEGREES CELSIUS

600

o Site A

D Site B

h- A SiteC

v Site D

1.0

1.5

Station 7L-2

0 100 200 300 400 500 

TEMPERATURE, IN DEGREES CELSIUS

1.0

1.5

B

o Site A

a Site B

A SiteC -

v Site D

Station 7L-4

0 100 200 300 400 500 600 

TEMPERATURE, IN DEGREES CELSIUS

0.25

0.50

I 0.75

CL 

LLJ

Q 1.00

1.25

Station 7L-6

0 100 200 300 400 

TEMPERATURE, IN DEGREES CELSIUS

co 

tr

LLJ

0

°'25 

0.50

X 0.75

CL 

LU

° 1.00

1.25

o Site A

n Site B

A Site C A'

v Site D /' /

A' $ '" I

\

 A'

D Station 7L-7

0 100 200 300 400 

TEMPERATURE, IN DEGREES CELSIUS

FIGURE 35. Temperature-depth profiles in deposits of the pumiceous 

pyroclastic flow of July 22. All data obtained on thermocouples inserted 

directly into deposit. A, Station 7L-2, 800 m north of base of stairsteps, 

in 1825 P.d.s.t. flow unit, at four sites (A-D) 2 days after emplacement. 

B, Station 7L-4, west side, middle of west tongue of 1825 P.d.s.t. flow unit,

at four sites (A-D) 18 hours after emplacement. C, Station 7L-6, near 

terminus of east tongue of 1825 P.d.s.t. flow unit, 21 days after 

emplacement. D, Station 7L-7, at terminus of west tongue of 1825 

P.d.s.t. flow unit, at four sites (A-D) 16 hours after emplacement.
74

CO 

DC 

LU

LU

DIRECT TEMPERATURE MEASUREMENTS OF DEPOSITS, MOUNT ST. HELENS, WASHINGTON, 1980-1981

0

o Site A 

Site B 

A Site C 

v Site D 

Site E 

Site F

100 200 300 400 500 600 700 800 

TEMPERATURE, IN DEGREES CELSIUS

CO 

DC 

LU

LiJ

Q_ 

LiJ 

O

. I

Station 7U-3

100 200 300 400 500 600 

TEMPERATURE, IN DEGREES CELSIUS

CO 

DC 

LiJ

LU

CL 

LiJ 

Q

G

200 400 600 

TEMPERATURE, IN DEGREES CELSIUS

800

CO

£ 0.5 

tD

I

fc 1.0

Q

1.5

H

o Site A 

n Site B

Station 7U-5 

i I i

0 100 200 300 400 500 

TEMPERATURE, IN DEGREES CELSIUS

0

CO °'25

DC

LU

LU 0.50

I 0.75

Q_ 

LiJ

° 1.00

1.25

Station 7U-6

0 100 200 300 400 500 600 

1.5 TEMPERATURE, IN DEGREES CELSIUS

FIGURE 35. Continued. Temperature-depth profiles in deposits of the 

pumiceous pyroclastic flow of July 22. All data obtained on 

thermocouples inserted directly into deposit. E, Station 7U-1, 100 

m north of base of stairsteps, 1901 P.d.s.t. flow unit. Curves A through 

D, 22 hours after emplacement; curves E and F, 4 days after 

emplacement. F, Station 7U-3, in middle of north pyroclastic flow 

apron, in 1901 P.d.s.t. flow unit. Curve A, 25 days after emplacement; 

points B, 44 days after emplacement. G, Station 7U-4, west side, 

middle of west tongue, in 1901 P.d.s.t. flow unit. Point A, 35 minutes 

after emplacement. Curves A'-D, 20 hours after emplacement at sites 

A-D, respectively. H, Station 7U-5, near terminus of east tongue of 

1901 P.d.s.t. flow unit, at two sites (A, B) 21 days after emplacement. 

/, Station 7U-6, near terminus of east tongue of 1901 P.d.s.t. flow 

unit, 21 days after emplacement.
APPENDIX 2. MOUNT ST. HELENS TEMPERATURE DATA 75

DC 

111 Site A, pipe 

Site A', pipe 

SiteB 

SiteC 

O Site D 

SiteE 

Site E1 

Site E"

0.5

1.0

1.5

2.0

o Site A

a Site B

A Site C

v Site D

O Site E

B Station 8-2

I___,

0 200 400 600 800 

TEMPERATURE, IN DEGREES CELSIUS

200 400 600 800 1000 

TEMPERATURE, IN DEGREES CELSIUS

0.5

1.0

1.5

2.0

Station 8-3

0 200 400 600 800 

TEMPERATURE, IN DEGREES CELSIUS

FIGURE 36. Temperature-depth profiles in deposits of the pumiceous 

pyroclastic flow of August 7. Open symbols, data obtained on 

thermocouples inserted directly into deposit; filled symbols, data obtained 

in pipe thermally equilibrated with the deposit. A, Station 8-1, in ejecta 

rampart around vent of August 7. Curves A and A', 6 days after emplacement 

at two sites; curves B, C, and E, 4 days after emplacement at sites B, C, 

and E; points D, 4 days after emplacement at site D; curve E', 6 days after 

emplacement at site E; curve E", 9 days after emplacement at site E. B, 

Station 8-2, in first step down on stairsteps, five sites (A-E) 20 hours after 

emplacement. C, Station 8-3, near terminus of west tongue, two sites (A, 

B) 18 hours after emplacement.
76 DIRECT TEMPERATURE MEASUREMENTS OF DEPOSITS, MOUNT ST. HELENS, WASHINGTON, 1980-1981

LU 

Z

I

LU 

Q

0.25

0.50

0.75

1.00

1.25

C 0-"

Station 10-4L

£ 0.25

0.50

g 0.75

1.00

0 100 200 300 400 500 600 

TEMPERATURE, IN DEGREES CELSIUS

0.5

1.0

-os - _ l 

o

 o

o Site A

a Site B

A Site C

Station 10-3U

200 400 600 

TEMPERATURE, IN DEGREES CELSIUS

800

o Site A

 n Site B

A Site C

v Site D

B Station 10-2U

200 400 600 800 

TEMPERATURE, IN DEGREES CELSIUS

0.5

1.0

1.5

.^ 

U

o Site A

n Site B

A Site C

v Site D

Station 10-4U _

0 100 200 300 400 500 600 

TEMPERATURE, IN DEGREES CELSIUS

FiGURh 37. Temperature-depth profiles in deposits of pumiceous pyroclastic 

flows of October 17. All data obtained on thermocouples directly inserted 

into deposit. A, Station 10-4L, at base of stairsteps, in 0928 P.d.s.t. flow 

unit, at five sites (A-E) 5 hours after emplacement. B, Station 10-2U, 

100-200 m south of ejecta rampart in 2112 P.d.s.t. flow unit, at four sites 

2 days after emplacement: site A, 170 m north of ejecta rampart; site B, 

200 m north of ejecta rampart; site C, 230 m north of ejecta rampart; and

site D, 260 m north of ejecta rampart. C, Station 10-3U, at top of stairsteps, 

in 2112 P.d.s.t. flow unit, at three sites: site A, 13 hours after emplacement; 

site B, near site A, 13 hours after emplacement; and site C, composite of 

several sites on first step down from amphitheater, 2 days after 

emplacement. D, Station 10-4U, at base of stairsteps, terminus of 2112 

P.d.s.t. flow unit, at four sites: sites A through C (curves A-C), 14 hours 

after emplacement; and site D (curve D), 7 days after emplacement.

U.S. GOVERNMENT PRINTING OFFICE: 1996 - 774-045 / 20048 REGION NO. 8
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