The 1961 Eruption 

of Kilauea Volcano 

Hawaii 

--" 

GEOLOGICAL SURVEY PROFESSIONAL PAPER 474-D 

) 

) 

The 1961 Eruption 

of Kilauea Volcano 

Hawaii 

By D. H. RICHTER, W. U. AULT, ]. P. EATON, and]. G. MOORE 

SHORTER CONTRIBUTIONS TO GENERAL GEOLOGY 

....... 

GEOLOGICAL SURVEY PROFESSIONAL PAPER 474-D 

A detailed account of the three summit eruptions 

and one flank eruption that occurred during I96I 

and the accompanying tumescence, sei~mic activity, 

and active faulting 

UNITED STATES GOVERNMENT PRINTING OFFICE, WASHINGTON : 1964 
UNITED STATES DEPARTMENT OF THE INTERIOR 

STEWART L. UDALL, Secretary 

GEOLOGICAL SURVEY 

William T. Pecora, Director 

FIRST PRINTING 1964 

SECOND PRINTING 1966 

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

Washington, D.C. 20402 - Price 35 cents (paper cover) 
CONTENTS 

Page Page 

Abstract __________________________________________ _ D1 

1 

4 

5 

5 

7 

Descripton of the eruption-Continued Introduction ______________________________________ _ Flank phase ___________________________________ _ D19 

23 

26 

27 

31 

34 

Pre-eruption tumescence and seismic activity __________ _ Volume and rate of extrusion of lava ______________ ---_ 

Description of the eruption _________________________ _ Temperature of the lava ____________________________ _ 

First summit phase ____________________________ _ Petrochemistry ____________________________________ _ 

Second summit phase __________________________ _ Ground movements during flank phase ____________ --- _ 

Third summit phase ____________________________ _ 11 References cited ______________ - ___ --- _____ - ----- ----

ILLUSTRATIONS 

Page 

FIGURE 1. Index m:ap of eastern Hawaii_ ____________________________________________________________________ ---- D2 

TABLE 

2. Map and section of Halemaumau before the 1961 summit eruption________________________________________ 3 

3. Ground-tilting of the Kilauea summit area------------------------------------------------------------- 4 

4. Map of the northeast collapse pit in Halemaumau crater ______________________________________ -- ____ ---- 6 

5. Northeast collapse pit in Halemaumau crater at 11h15m, February 24, 196L_______________________________ 7 

6. Northeast collapse pit in Halemaumau crater at 11h45m, March 7, 196L__________________________________ 9 

7. Northeast collapse pit iQ. Halemaumau crater at 11h45m, March 12, 196L __ ------------------------------- 10 

8. Northeast collapse pit in Halemaum·au crater at 15h()()m; March 20, 196L--------------------------------- 11 

9. Halemaumau crater before the third summit eruptive phase______________________________________________ 12 

10. Halemaumau crater at 06h0Qm, July 11, 1961_---------------------------------------------------------- 13 

11. Eruptive activity in Halemaumau crater at approximately 23h30m, July 10, 196L__________________________ 14 

12. Eruptive activity in Halemaumau crater at approximately 13h30m, July 11, 196L _ ------------------------- 15 

13. Same view as in figure 12, one-half hour later ________________________________________________________ - _ 16 

14. Halemaumau crater at 18h0Qm, July 11, 196L ______________________________________________ --- ___ -- _ -- _ 17 

15. Eruptive activity in Halemaumau crater ~t approximately 15hOOm, July 12, 196L___________________________ 18 

16. Halemaumau crater at 11 bOOm, July 13, 196L ____________________________________ --- ________ --- __ ------ 19 

17. Eruptive activity in Halemaumau crater at approximately 12h0Qm, July 17, 196L__________________________ 20 

18. Halemaumau crater on July 18, 1961_ __________________________________________ -- ___ --- ___ ---- _ ------- 21 

19. Halemaumau crater at approximately 12h3Qm, July 17, 1961_--------------------------------------------- 22 

20. Cross section of Haleniaumau ______________________________________________________ --- ___ ------------ 23 

21. Drifts of pumice along the southwest rim of Halemaumau_______________________________________________ 24 

22. Chronology of events during the September 1961 flank eruption__________________________________________ 25 

23. Aerial view showing the active zone along Kilauea's east rift zone at 12hOOm, September 22----------------- 26 

24. Map of part of the east rift zone of Kilauea _________________________________________ --- _- - - ----------- 27 

25. Lava fountains, 300 feet high, at the Heiheiahulu flow at 17hOOm on September 23 _______________ --- __ - _--- _ 28 

26. CaO variation diagram of 1961lavas-----------------------------------------------------------------:- 30 

27. Si02 variation diagram of 1961 lavas _________________________________________________ ----------------- 30 

28. Southeast-facing fault scarp midway between the Jonika and Kaumuki flows at 12hOOm on September 24_- _-- _ 32 

29. New south-facing fault scarp, al)out 20 feet high, between the Heiheiahulu and Kaumuki flows_______________ 33 

30. Same fault scarp shown in figure 28, 2 days later _________________________________ ---_-- _____ ---_------_ 34 

TABLES 

1. Volume and rate of lava extrusion during 1961 eruption of Kilauea ______________________________________ _ 

2. Volume and rate of lava extrusion and withdrawal during the third summit eruptive phase _________________ _ 

3. Lava temperatures during 1961 eruption of Kilauea _____________________________ ------------------------

4. Chemical·analyses, norms, and modal olivine of lavas from the 1961 eruption of Kilauea ____________________ _ 

III 

Page 

D25 

25 

27 

29 

SHORTER CONTRIBUTIONS TO GENERAL GEOLOGY 

THE 1961 ERUPTION OF KILAUEA VOLCANO, HAWAII 

By D. H. RICHTER, W. U. AuLT, J. P. EATON, and J. G. MooRE 

ABSTRACT 

The 1961 eruption or Kilauea Volcano, through the period 

February 24 to September 25, 1961, consisted of three summit 

eruptive phases followed by a flank eruptive phase. Tumescence 

of the Kilauea summit area, which began in the summer of 1960, 

continued virtually unchanged throughout and after the three 

periods of summit eruption. Rapid detumescence accompanied 

the flank eruption. Seismic activity during tumescence was 

moderate and persistent, but it gave no particular forewarning 

of imminent eruption. However, a swarm of relatively large 

earthquakes and strong harmonic tremor preceded the flank 

eruptive phase by about 16 hours. 

The three summit eruptive phases were confined to Halemaunrau, the deep crater within Knauea caldera. During the first 

summit phase, which lasted only 8 hours, on February 24, a 

small collapse pit on the floor of Halemaumau was filled with 

320,000 cubic yards of lava. Within a few hours after fountaining ceased, most of the new lava had drained back through the 

eruptive vents. During the second summit phase, which lasted 

from March 3 to 25, the same collapse pit was refilled. The 

third and most voluminous of the summit phases began on July 

10 when lava fountains burst from the crater floor along a zone 

more than 1,500 feet long. The eruption continued until July 17, 

forming a new lake of lava 210 feet deep and 17.3 million cubic 

yards in volume. Backfiow after fountaining resulted in a loss 

of approximately 1.3 million cubic yards. The 1961 eruptive 

cycle ended with a flank eruption along a 14-mile segment of 

Kilauea's east rift zon.e from September 22 to 25. Thirteen 

small, discontinuous lava flows, whose total volume was about 

1.9 :million cubic yards, were produced; and a large number of 

new cracks emitted volcanic fume and steam. Drainback of 

large volumes of lava into cracks apparently occurred at all the 

outbreaks, and no large flows were formed. 

The futal volume of new lava added to the surface by all the 

1961 eruptive phases is ·approximately 18.2 million cubic yards. 

Measured rates of extrusion ranged from 660 cubic yards per 

hour during the second summit phase to 114,000 cubic yards per 

hour during the third summit phase. 

Temperatures of the erupting lava ranged from 1,085° to 

1,127° C in the three summit eruptive phases. 

The lavas range from tholeiite basalt in the summit and upper 

rift zone areas to tholeiite olivine basalt lower on the rift zone. 

Variation diagrams based on eight new chemical analyses indi· 

ca:te that the composition of the 1961lavas was affected by three 

types of differentiation: {1) removal of magnesian olivine, (2) 

removal of augite and minor plagioclase, and {3) addition of 

magnesian olivine. The first type affected the composition of 

both the summit and flank lavas; the second type produced the 

characteristic differences between the summit and fi'ank lavas; 

and the third type was responsible for the range in composition 

of the flank lavas. 

Extensive faulting and cracking along the east rift zone preceded, accompanied, and followed the flank eruptive phase. New 

faults having as much as 20 feet of vertical displacement were 

formed, and many old faults were reactivated. The 1961 flank 

activity occurred a:long the north side of the rift zone, which is 

noticeably bipartite; the north side is characterized by gra•benhorst topography and the south side, by cinder cones. 

INTRODUCTION 

In February 1961, only 1 year after its spectacular 

1959-60 eruption, Kilauea Volcano resumed activity 

with a brief eruption at its summit. This eruption 

began a 7 -month period of sporadic activity consisting of four distinct eruptive phases which are collectively referred to as the 1961 eruption of Kilauea. 

This terminology, which was adopted for the sake of 

convenience, is not without a geologic· basis. All the 

individual eruptive phases of 1961 resulted from a 

single filling of Kilauea's magma reservoir and conformed to the previously described sequence of 

tumsecence, summit eruption, flank eruption, and 

detumescence (Richter and Eaton, 1960}. 

Kilauea Volcano, on the island of Hawaii (fig. 1}, is 

the southeasternmost, and probably the youngest, of 

the basaltic volcanoes that form the mid-Pacific Hawaiian Archipelago. Although Kilauea is only 4,090 feet 

above sea level at its summit and is dwarfed by its lofty 

13,700-foot neighbors Mauna Loa ahd Mauna Kea, it 

rises some 20,000 feet above the ocean floor and constitutes a volcanic pile m tremendous bulk. Historic 

eruptive activity of Kilauea has been confined to the 

summit caldera and to the two rift zones that extend 

down the flanks of the volcano from the summit to far 

below sea level. The relatively flat-floored summit 

caldera is indented by the deep crater Halemaumau 

(fig. 2}, the usual site of summit eruptive activity. 

D1 
D2 SHORTER CONTRIBUTIONS TO GENERAL GEOLOGY 

During the past decade (1952-62) Kilauea Volcano 

has shown a marked increase in the frequency of eruption. In June 1952 an 18-year period of quiescence was 

terminated by a 4%-month-long summit eruption in 

Halemaumau (Macdonald, 1955). A brief summit 

eruption in May 1954 (Macdonald and Eaton, 1957), 

followed by a flank eruption which lasted from February to May 1955 on the east rift zone (Macdonald 

,# 

0 2 4 6 

and Eaton, 1955) , waa the first of three successive eruptive periods in which a very close relation between 

summit and flank activity was observed. The second 

of these summit-flank eruptions began with the spectacular summit activity in Kilauea Iki crater in November and December 1959 and ended with the flank 

activity at Kapoho along the east rift zone in January 

and February 1960 (Richter and Eaton, 1960). The 

8 10 MILES 

Area shown In figure 24 

EXPLANATION 

... Seismograph station 

L_ __ _L __ ~----~---L--~ 

CONTOUR INTERVAL 1000 FEET 

DATUM IS MEAN SEA LEVEL 

FIGURE 1.-Index map of eastern Hawaii showing the summit region and east rift of Kilauea Volcano and the location of. U.S. Geological 

Survey seismogra.ph stations. Halemaumau Is shown on large-scale maps In figures 2, 10, 14, 16, and 18. Outlined area of Kilauea 

east rift zone Is shown in figure 24. 
N 

I 

A 3800' 

3400' 

3000' 

THE 1961 ERUPTION OF KlLAUEA VOLCANO 

OoBSERVATION 

PLATFORM 

z 

0 

f= 

u 

w 

1./l 

z 

EXPLANATION 

l//l 

Top and base of crater wall 

Principal scarps and cracks on 

floor of crater 

Talus 

! .... ·········· I 

1952 lava reextruded in 1960 

X3170 

Altitude by vertical angle, in feet 

A 3640 

Altitude at trianulation station, in feet 

D3 

0 400 800 1200 FEET 

DATUM IS MEAN SEA LEVEL 

A' 

~--~ r 2600'~--------------------------------------------------------------------------------------~ 

FIGUBIII 2.-Ma.p and section of Halemaumau crater, in the floor of Kilauea caldera, before the 1961 summit eruptions. All collapse features 

in the bottom of Halemaumau occuned during the summit subsidence of February-March 1960. (See fig. 20 for section A.-A.'.) 
D4 SHORTER CONTRIBUTIONS TO GENERAL GEOLOGY 

culmination of the 1959-60 eruption was the dramatic 

subsidence of the Kileauea summit area and the 350-

foot collapse of the bottom of Halemaumau. The 1961 

eruption followed the same pattern but had three separate summit phases and one very brief flank phase. 

Although the period 1952-62 appears to be one of 

relatively strong eruptive activity for Kilauea, the 

average annual rate of lava extrusion is only slightly 

greater than for all the historic period ( 1823-1962) . 

Between 1952 and 1962 approximately 42 million cubic 

yards of lava per year were added to the surface of the 

volcano, and according to the data of Stearns and 

Macdonald (1946), the rate during the last 139 years 

has been 33 million cubic yards per year. Of significance, however, is the increased flank activity and concomitant increase in volume of lava extruded from the 

rift zones of Kilauea in the last 10 years. During this 

period the annual rate of extrusion from the rift zones 

has been 28 million cubic yards per year, wheroos over 

the longer period the rate has been less than 5 million 

cubic yards per year. 

This paper summarizes the observations and data collected by members of the U.S. Geological Survey's 

Hawaiian Volcano Observatory during the 1961 eruption. We sincerely thank all our observatory co work1959-60 ERUPTION 

Summit Flank 

-- -

West (tumescence) 

East 

I 

(detumescence) 

(j) 

z 

~3 

c 

<( 

a:: 

2 

North ( tumescence) 

0 

t 

South (detumescence) 

1959 1960 

ers for their contributions and excellent support. The 

help of Hawaii Volcanoes National Park personnel and 

the support of the Hawaii Air National Guard in air 

reconnaissance are gratefully acknowledged. 

PRE-ERUPTION TUMESCENCE AND SEISMIC ACTIVITY 

In July 1960, only 4 months after the great summit 

detumescence of Kilauea that accompanied and followed the 1960 flank eruption, water-tube tiltmeters 

(Eaton, 1959) revealed a resumption of outward tilting 

along the northwest rim of the caldera. The renewed 

tumescence, when first detected by the east-west component of the permanent short-base tiltmeter at U wekahuna on the rim of the caldera, was extremely slight 

and gradual (fig. 3). During September the northsouth component of the instrument at Uwekahuna also 

began to indicate tumescence. Remeasurement at the 

network of long-base tiltmeter stations on the volcano 

in mid-November clearly showed that the entire summit region of Kilauea was swelling rapidly as magma 

accumulated in the relatively shallow reservoir a few 

kilometers beneath the caldera. 

Tumescence accelerated markedly on October 22 and 

continued at an extremely rapid rate until November 5, 

1961 ERUPTION 

Summit Flank 

I 2 3 

1961 1962 

FIGURE 3.-Ground tilting of the Kilauea summit area as indicated by daily readings of the short base water-level tiltmeter at Uwekahuna 

(fig. 1) from late 1959 to early 1962. Periods of eruption (actual extrusion of liquid lava) are shown at top. 
THE 19 61 ERUPTION OF KILAUEA VOLCANO D5 

when a sudden reversal of tilt was detected by the shortbase tiltmeters. By November 11, however, tumescence 

had resumed, and it rell}ained at a relatively high and 

fairly uniform rate until the fl·ank eruption in September 1961. The relation between ground tilting and 

change in volume of the Kilauea summit esta:blished 

during the 1960 subsidence indicated that the observed 

rate of tumescense between November 1960 and September 1961 could have been maintained by the addition of approximately 107 cubic yards of magma per 

month to. the shallow reservoir within the volcano. 

Seismic activity during the period of tumescence was, 

in general, moderate, and there was no indication of a 

gradual buildup prior to the summit eruption as there 

was prior to 11h.e 195-9 outbreak in Kilauea Iki (fig. 1) 

(Richter and Eaton, 1960). Beneath the summit of 

Kilauea, swarms of deep ( 55--60 kilometers) and intermediate (10-15 kilometers) earthquakes occurred principally during the early stages of tumescence. Throughout the period of tumescence, many shallow ( < 5 

kilometers) earthquakes and oocasional earthquakes 

from a depth of about 30 kilometers originated beneath 

the summit. The possibility that the early seismic activity was actually tracing the progress of the magma as it 

rose from its source in the mantle through the conduits 

leading into the volcano is intriguing but highly conjectural. The local seismic activity, on the other hand, 

did correlate very closely with the rate of tumescence 

and probably was the result of structural readjustment 

in the relatively thin carapace of brittle rocks overlying 

the inflating reservoir. 

In October 1960 two swarms of deep earthquakes, 

originating in the mantle 55-60 kilometers beneath 

Kilauea Volcano, were recorded on the seismograph net 

around the summit area (fig. 1). The first of these 

lasted from October 4 through 7 and consisted of more 

than 4,000 earthquakes and accompanying harmonic 

tremor; the second swarm had a like number of disturbances; it began gradually on about October 8, built 

up to a maximum of 900 earthquakes daily on October 

18 and 19, and ceased abruptly on October 20. In late 

October, seismic activity appeared to shift to a much 

shallower zone in the mantle beneath the volcano; occasional earthquakes began to emanate from a depth of 

30 kilometers. Coincident with the beginning of the 

30-kilometer deep activity, swarms of earthquakes and 

harmonic tremor also began to emanate from a depth 

of· 10-15 kilometers beneath the summit end of tJhe 

soutl~west rift. This intermediate-depth activity was 

short lived, and by October 28 it had virtually stopped. 

The deeper earthquakes at 30 kilometers, however, continued intermittently throughout the entire period of 

summit .tumescence. 

207-460 0-66-2 

Shallow earthquakes in the caldera area averaged 

30 per day through September and the first half of 

October 1960. During the period of accelerated tumescence in late October and early November, the number 

of local quakes increased dramatically, reaehing a maximum of more than 500 earthquakes per day on October 

31. The largest of these had a magnitude of 3.2; it occurred at 21 h 32m on October 27 and was centered along 

the outermost peripheral fault bounding the nort~ rim 

of the caldera. Although no evidence of vertical displacement was observed along the scarp, ground movement accompanying the quake damaged water tanks 

and caused extensive cracking of pavement in the 

Kilauea Military Camp area on the caldera's north 

rim. 

After the rapid tumescence in early November, the 

frequency of local earthquakes decreased; they averaged 

a;bout 100 per day from that time until the first summit 

eruption on February 24, 1961. Occasionally, the frequency of local earthquakes increased to nearly 300 per 

day during this period, hut there was no seismic forewarning of imminent eruption. Most of the local earthquakes were detected only by the short-period vertical 

seismometer at the North Pit station (fig. 1) on the 

caldera floor, although some of the larger disturbances 

were recorded at all stations in the Kilauea seismic net, 

and a few were felt by residents of the Kilauea summit 

area. 

DESCRIPTION OF THE ERUPTION 

FIRST SU:J.VDII~ PHASE 

At about 04hOOm on February 24, 1961, the seismographs in Kilauea summit ·area (fig. 1) began to record 

a minor swarm of small, shallow earthquakes and weak 

harmonic tremor that originated at shallow depths near 

Halemaumnu. The earthquake swarm lasted only 15 

minutes; the weak tremor, however, persisted. At rubout 

07h07m the harmonic tremor increased a;bruptly in intensity, heralding the beginning of eruption. 

A thin, inconspicuous column of bluish volcanic fume 

rising from Halema umau crater was seen from the east 

rim of Kilauea caldera at 07h20m, hut it was not until 

07h50m that observers first reached the crater rim. The 

eruptive activity was confined within the small, northeast collapse pit, 400 feet in dia.meter, on the floor of 

Halemaumau (fig. 4), where a lava fountain was spurting to heights of 50-100 feet in the southwest side of 

the pit ( loc. B, fig. 4), and a series of smaller fountains 

played from a line of vents along the extreme east side 

of the pit ( loc. A). By 08h10m the southernmost of the 

fountains at A was spurting to a height of 100 feet and 

two ne'v vents at C and D were also erupting. 
D6 SHORTER CONTRIBUTIONS TO GENERAL GEOLOGY 

The nearly flat talus-covered floor of the 140-footdeep pit was rapidly covered by new lava, and by 

08h35m the lava had risen to the level of the vent at 

locality B. Waves generated in the turbulent area at 

the base of the fountain swept across the pond, and a 

distinct but rather weak current moved in the opposite 

direction from the vents at localities A and C toward 

locality B. Although the level of the pond continued 

to rise, it was evident that lava was draining away 

through the drowned vent at locality B. 

At 09h02m the pond reached the level of the vent at 

locality D, and by 09h24m fountains at both localities 

B and D were reduced to violent surges that occasionally blasted lava to heights of about 50 feet. The most 

consistent fountaining was at locality C, where a single 

narrow jet shot to heights of 100 feet. A squat, massive fountain at A played from the southernmost vent, 

while from the smaller vents along the short rift extending northward from locality A several lava rivulets cascaded down the short slope into the pond. Hot 

turbulent air currents above the fountains carried light 

frothy pumice and Pele's hair higher than the rim of 

Halemaumau, 500 feet above the vents. Most of this 

N 

1 

Rim of 

100 200 FEET 

Preeruption altitudes by vertical angle 

EXPLANATION 

FIRST SUMMIT ERUPTION 

CFEB 24. 1961l 

.c 

Vents 

Maximum extent of lava 

SECOND SUMMIT ERUPTION 

<MAR 3-25. 19611 

oE Early vents 

-·-·-s-p~"tier·~;e-·-·-

Maximum extent of lava 

FIGURE 4.-Map of the northeast collapse pit in Halemaumau crater 

showing vents and maximum extent of lava -in the first and second 

summit eruptive phases of 1961. .A, B, C, and D are localities of 

vents of the February activity, and E and F, of the March activity. 

See figure 2 for setting in Halemaumau. 

pyroclastic material was carried over Halemaumau by 

the northeast tradewinds, but minor amounts fell on 

the crater rim above the collapse pit. The composition 

of this material is given in column 1, table 4. 

All the vents were covered by the rapidly rising lava 

by 10h15m, when the pond reached its maximum depth 

of about 110 feet. Lava draining into the vents at 

localities Band D frequently reduced the surging fountains to a rolling boil, and at 10h33m the pond began to 

pour back into the vent at B at an accelerated rate. 

Within a few minutes the crusted pond surface was 

lowered about 5 feet, leaving a glistening black ring 

to mark the high stand of the lava. Occasionally, activity revived at B, sending great surges of lava across 

the pond and impeding the backflow; but by 11h23m 

the vent was virtually dead. The level surface of the 

pond had subsided more than 10 feet and was continuing to drop rapidly (fig. 5). Large rafts of blackened 

crust continually moved across the pond toward the 

vent, where they plunged into the agitated orangeyellow fluid and disappeared. 

The fountaining at localities A, C, and D continued 

unchanged through this early period of strong backflow; at 13h30m the pond surface was about 50 feet 

below its high stand, and the vents at localities A and 

C were again exposed. By 14h30m, however, shortly 

after the vent at locality D reappeared above pond 

level, activity at the fountains began to wane. Fountaining ceased in the vents at 'locality A by 14h50m, and 

at locality C by 14h55m. The remaining fountain at D 

continued to emit spatter sporadically until 15h08m, 

when it too died, marking the end of the very brief 

first phase of the summit eruption. 

Lava drainage down the vent at locality Band heavy 

fuming from the other inactive vents continued through 

the rest of the day and into the evening. After dark, 

tJhe collapse pit resembled a small ·stool factory : a thin 

bright-red incandescent rihbon of lava flowed slowly toward locality B; a pale yellowish-blue fla.me issued from 

the vent at C ; and the orifice of the vents at locality A 

glowed brightly. At 21 hOOm 30-foot-high flames were 

also issuing from five vents at locality A ; by 23h50m, 

however, flaming was no longer visible, and the intensity 

of the glowing in all the vents had greatly diminished. 

By the next morning (February 25), evidence of the 

eruptive activity of the preceding day had virtually 

disapperured. Approximately 10 feet of broken lava 

crust remained in the bottom of the collapse pit, and a 

thin black coat of new la.va. lined its walls; the pit, however, was virtually the same size as before the e:ru ption. 

Of the 320,000 cubic yards of lava which filled the pit 

during the height of activity, probably less than 30,000 

cubic yards remained. Moreover, the vents at localities 
I 

THE 1 9 61 ERUPTION OF KILAUEA VOLCANO D7 

B, C, and D were not distinguishable on the rubblecovered floor, and only a minor amount of fume emission marked the line of vents at locality A, higher up on 

the wall of the pit. 

Harmonic tremor, which had remained at a relatively 

high level throughout the 8-hour eruption, abruptly decreased to about one-tenth of its eruption level when 

fountaining ceased. During the next 2 days the tremor 

continued to decrease, and by February 28 it had disappeared altogether. The eruption did not appear to 

affect the overall tilt pattern (fig. 3). Short-base tiltmeters around the caldera continued to show a steady 

inflation of the summit area during and after the eruption; remeasurement of the long-base tiltmeter stations 

indicated that the pattern and rate of tilting for the 

3-month interval ending with the eruption had not 

changed signifiC3.iD.tly from that of the previous 2-

month period. 

SECOND SUMMIT PHASE 

At about 22hQOm, on March 3, 1961, mild eruptive activity resumed in the northeast collapse pit in the floor 

of Halemaumau. Inclement weather, however, hampered visibility in the crater, and only occasionally could 

a reflected pink glow be seen on the clouds drifting 

over the pit. 

By the next morning (March 4, 1961) the weather 

had cleared, and a fume cloud rising from the pit was. 

FIGURE 5.-Northeast collapse pit in HaleiDAumau crater at 11"15m on February 24, 1961, about 1 hour· after lava pond reached its maxi-' 

mum depth. Backtlow down vent at locality B (arrow) has lowered pond surface about 10 feet, while vents along side of pit (left) 

continue to fountain. On level pond surface black patches of crust (dark gray) are surrounded and rafted toward vent at locality B 

by fluid incandescent lava (light gray) . View Is toward south from northeast rim of Halemaumau ; distance across pit is about 

400 feet. 
D8 SHORTER CONTRIBUTIONS TO GENERAL GEOLOGY 

cleady visible. Viscous lava tossed from two small 

vents (locs. E and F, fig. 4), slightly north of the February 24 vents at localities C and D, had already built 

up a small spatter oone on the floor of the pit, and a 

number of short flows were oozing from the periphery 

of a new flow that covered about half of the old floor. 

Viewed from the rim of Halemaumau directly above the 

east end of the pit, liquid lava could be observed rising 

and falling rhythmically every few seconds within two 

small caldrons that had developed over the vents. The 

rhythmic oscillation of the lava level was apparently 

controlled by intermittent release of gas. Large expanding bubbles of gas lifted the lava surface as they 

rose through the liquid contents of the caldrons. When 

they burst at the surface, spatter was thrown from the 

vent, and the liquid inside the vent dropped to its 

former level. 

As the harmonic trenror gradually increased, the 

eruptive activity also increased. By nightfall, bursts of 

spatter sprayed from the vents at intervals of about 1 

seiCOnd, and the surface of the new lava contained a 

myriad of incandescent cracks. From these cracks and 

from the base of the two spatter cones, short viscous 

flows were continually reforming the surface of the 

slowly filling pond. 

By 16h0()m on March 5 only the easternmost spatter 

vent (loc. E) remained active; the vent at locality F 

was covered by fresh spatter but was apparently the 

source of a loud hissing roar that emanated from the 

area. New lava nearly oovered the bottom of the pit; 

but, unlike the pond of February 24, a distinct slope 

could now be observed between the high area around 

the base of the spatter cone and the far edges of the new 

pond. The pond apparently was not O'Illy being filled 

by the meager spatter tossed from the vent but also by 

a number of shallow tubes leading out from the base of 

the caldron over the vent. 

Conditions of the eruption were little changed by the 

morning of March 6. The pond had risen slightly during the night, and new flows now covered the entire floor 

of the pit. Spa:tter, in bursts 30-40 feet high, blasted 

from the vent at locality E approximately once per 

second. The spattering was accompanied by loud, dull 

repqrts that might be compared to the noise emitted 

from a huge pot of boiling oatmeal. 

On March 7 the pond was about 20 feet deep, and the 

beginning of crustal foundering indicated that it had a 

fluid core covered by a relatively thin crust (fig. 6). 

At 11 h45m the caldron in the now large spatter cone was 

partly bridged by a thin cap of congealed spatter, from 

which hung long incandescent stalactites of pai:>'ty lava. 

Through the day more and more spatter froze on the 

cap, and by evening O'Illy three small apertures exposed 

the liquid beneath. 

During the night the cap collapsed, and by 10h00m 

on March 8 the 20-foot-wide caldron of sloshing lava 

was once more fully exposed. At the north . base of 

the spatter cone, a small window in the crust exposed 

a stream of lava surging in phase with the rise and 

fall of lava in the caldron. At 21 h30m the window in 

the tube was closed, and only the boiling caldron and 

a number of short flows oozing from cracks on the 

surface of the pond were still active. 

On Marcil 9 the pond was a;bout 60 feet deep. The 

orifice at the top of the 30-foot-high spatter cone had 

again been reduced in size by the accumulation of spatter, but the caldron beneath appeared to be larger. At 

14h30m a 100-foot-square section of the crust in the 

southwestern part of the pond was rapidly engulfed 

by upwelling, roaring liquid lava. Other smaller areas 

of the crust of the pond also foundered as the liquid 

lava in the pond broke through the sloping restraining crust and spread outward to establish a new, more 

nearly level surface. The most intense foundering occurred in the most steeply sloping part of the pond 

surrounding the base of the cone. 

The activity in the pit was somewhat reduced on 

March 10. Only a small, narrow opening remained in 

the top of the cone, and spatter emission was very 

sporadic. For t!he next 2 days this low level of activity changed little. The opening above the caldron remained small, and during the morning of March 12 it 

was completely closed by a thick cap of spatter (fig. 7). 

Even then, however, fume escaping from the porous 

top of the cone, together with a sloshing sound emanating from the cone, indicated that the caldron was 

still liquid filled. 

At 22hOOm on March 13 the harmonic tremor doubled 

in intensity and the rate of spatter emission increased. 

Spatter shot to heights of 100 feet from an enlarged 

orifice over the caldron, and by 23hOOm the entire east 

end of the pond around the spatter cone was aglow 

with many small flows. Through the next day (March 

14) the activity remained at this high level. Several 

small lava flows issued from a breach in the east side 

of the spatter cone; on the south· side of the cone, lava 

was extruded intermittently from a small vent which 

had a fascinating trapdoorlike lid. When lava rose 

in the caldron, the hinged "trapdoor" opened and a 

small amount of lava gushed out; as the lava receded in 

the caldron the "door" closed, shutting off the flow. 

At 13hOOm on Maroh 14, the pond was approximately 

90 feet deep, rising 30 feet during the preceding 5 days. 

However, because many surface features on the crust 
THE 1961 ERUPTION OF KILAUEA VOLCANO D9 

FIGURE 6.-Northeast collapse pit in Halema umau crater at Uh45m on March 7, 1961. Lava pond Is about 20 feet deep, and opening at 

top of new cone (compare with fig. 8) Is partially bridged over. Note the high lava mark of February 24 pond on wall of pit (arrow), 

which Is about 60 feet above level of pond In this photograph. VIew Is toward west from northeast rim of Halemaumau. 

that covered the pond were more than 3 days old, it was 

evident that much of the pond was filled by subsurface injection of new lava. Moreover, the crust was 

practically level everywhere except immediately 

around the cone, and crustal foundering had become 

negligible. 

By March 15 spatter activity had decreased again, 

and only occasionally could lava be seen splashing in 

the caldron over the vent. On March 16 collapse of 

the spatter-encrusted top of the cone ~nlarged the caldron orifice to approximately 25 feet in diameter, and, 

although spatter emission remained minor, liquid lava 

was generally visible in the caldron until March 24. 

The lava pond was filled to a depth of approximately 100 feet by March 17. Along the entire north 

and east sides of the pit, lava stood at the maximum 

level reached by the pond of February 24; only at the 

extreme west end of the pit was the pond some 5 feet 

below the level of February 24. Within 2 days the last 

trace of the February lava was covered and early in the 

morning on March 19 the pond level reached the height . 

of the lowest part of the narrow ridge that separated 

the northeast collapse pit from the larger peripheral 

subsidence crack on the main floor of Halemaumau. 

At llh30m a small stream of lava began to pour over 

the 20- to 30-foot-high scarp and into the deep crack 

at its base. The rate of flow of the pond lava into 

this crack increased rapidly during the next few hours, 

and by the afternoon of March 20 at least three vigorous streams were observed flowing from the pond. 
DlO SHORTER CONTRIBUTIONS TO GENERAL GEOLOGY 

Between March 20 and 23, frequent collapse of the 

unstable upper part of the cone occasionally allowed 

}ava to drain from t'he caldron and form small flows 

that spread over the east end of the pond (fig. 8) . On 

March 21 the largest of these caldron-fed flows sent a 

narrow tongue of lava to within a few feet of the breach 

in the west wall of the pit. 

On March 24 only a small glowing hole could be 

seen in the top of the spatter cone. There was no indication of lava flowing over the subsidence scarp, and 

only a few small lava oozes were active on the pond's 

surface. An occasional whooshing noise, accompanied 

by increased exhalation of fume from the vent indicated that liquid lava was still in the conduit. At 

20h00m on March 25 the amplitude of the harmonic 

tremor decreased to a very low level, and the eruption 

was virtually over. Throughout the next few days an 

occasional burst of harmonic tremor was recorded, but 

at no time was there any evidence of renewed surface 

activity. 

The lava pond in the small northeast collapse pit 

was approximately 105 feet deep ( 5 feet above the 

pond of February 24) at the cessation of activity. No 

measurable drainage of lava occurred either during or 

after the eruption; apparently the thick flanks of the 

spatter cone prevented backflow into the open vent. 

FIGURE 7.-Northeast collapse pit in Halemaumau crater at 11"45m on March 12, 1961. Lava pond is about 75 feet deep and a bout 15 

feet below the h igh lava mark of the February 24 pond (a rrow). Fume escapes from the top of the cone, which is compietely covered 

with a lid of congealed spatter. Viewpoint is the same aa in figures 6 and 8. 
THE 1961 ERUPTION OF KILAUEA VOLCANO Dll 

THIRD SUMMIT PHASE 

Evidence from the short-base tiltmeter at Uwekahuna indicated that the general tumescence of Kilauea's summit continued practically without interruption 

during and after the second summit eruption phase in 

March (fig. 3). Releveling of the long-base tiltmeter 

stations in February, May, and June, however, indicated that the rate of tilting during the period from 

May to June was about one-half the rate during the 

period from February to March. But even this reduced rate was large when compared to the tilting prior 

to the 1959 eruption of Kilauea I ki. 

During the last 2 weeks in June, a strong swarm of 

earthquakes originating in the upper end of the southwest rift zone of Kilauea was recorded on the Desert 

seismograph. The number of these earthquakes 

averaged more than 175 per day between June 17 and 

June 21; the number declined to about 100 per day 

during the last week in June, and to about 60 per day 

during the first week of July. Local shallow earthquakes in the caldera region, as recorded on the North 

Pit seismograph, increased from about 70 per day during June to about 120 per day in the 2-week period 

preceding the eruption in July. Only a few of these 

were felt. 

FIGURE B.-Northeast collapse pit in Halema uma u crater at 15•00'" on March 20, 1961. Lava pond has reached its maximum depth of 

about 10[) feet, completely covering the February 24 lava , and is spilling into peripheral subsidence crack (upper left) near outer 

ed~;e of main cra t er floor. Ca ldron of flui d hl,·u i~ visible in spatter cone. Viewpoi nt is the same us in figures 6 a nd 8. 
D12 SHORTER CONTRIBUTIONS TO GENERAL GEOLOGY 

FIGURE 9.-Halemaumau crater before the third summit eruptive phase showing the collapse features forme.d during the summit subsidence 

In February 1960. Over central collapse pit (bottom left) and southwest colla.pse pit (center right) the crater Is approximately 700 

feet deep. View is toward the southwest from the northeast rim of Halemaumau. The northeast collapse pit (site of the February 

and .March 1961 eruptive phalles) is out of view to bottom left. 

At about 19hOOm on July 10 weak harmonic tremor, 

accompanied by a series of small to moderate shallow 

earthquakes, began to record on the seismographs 

around the summit of Kilauea. For about 1 hour, 

tremor and earthquakes gradually increased in magnitude, and one quake at 19h50m was felt on the north rim 

o£ the caldera. At the onset of tremor and earthquakes, the traces on the long-period horizontal-component Press-Ewing seismograms at Uwekahuna began 

an hour-long excursion owing to rapid northwestward 

tilting a way from Halemaumau (tumescence). The 

maximum rate of tilting occurred at 19h35m, and by 

201105m tilting had ceased. 

A brightly illuminated fume cloud lit the sky above 

Halemaumau at 2011 15m on July 10, and at 201130m the 

top of a tall lava fountain could be seen spurting above 

the west wall of the crater from the U.S. Geological 

Survey Volcano Observatory at U wekahuna. At 
THE 19 61 ERUPTION OF KILAUEA VOLCANO Dl3 

0 400 BOO 1200 FEET 

IT 

Extent of lava 

, ......... 1 

········· Cinder-pumice cone 

Initial 

~ vents 

l±fi#l 

Lava and spatter cone 

of March 1961 

FIGURE 10.-Halemaumau crater at 06•oom, July 11, 1961. Dotted line 

under the new lava outlines bottom of the central collapse pit. 

20h32m observers reached the south rim of Halemaumau, 

after driving through falling pumice along the craterrim road half a mile southwest of the crater, and found 

lava fountains erupting from the central and southwest 

1960 collapse pits on the crater floor (figs. 2, 9). 

In the southwest collapse pit, fountains at localities 

A and B (fig. 10) were reaching heights of 50 and 100 

feet, respectively; at locality D, in the central collapse 

pit, a number of lower fountains '"ere playing along 

a short arcuate rift halfway up the northwest wall of 

the pit (fig. 10). By 2Qh35m the vent at B was 

inactive, but a new vent at C on the east side of 

the southwest collapse pit had opened, and a fountain was playing to heights of 100-200 feet. All the 

vents, including those of the February-March eruptions, lay approximately along a line trending about 

N. 65° E. across the floor of Halemaumau, which was 

virtually coincident with the alinement of the 1952 and 

1954 eruptive fissures in Halemaumau (Macdonald and 

Eaton, 1957). 

Lava from the vents at localities A and C rapidly 

filled the 120-foot-deep southwest collapse pit, and by 

22h3Qm lava began to overflow onto the main floor of 

Halemaumau. In the larger central collapse pit lava 

had reached the base of the fountains, forming a pond 

which was 40-50 feet deep. Small spatter ramparts 

around the vents at D, which had built up to the level 

of the main floor around the pit, were also inundated 

rapidly by the rising lava, and by 22h5Qm lava was overflowing into the large peripheral cracks around the central pit. At 22h57m lava flows from the southwest pit 

reached the central pond, and by 23h3Qm a well-defined 

lava river had formed between the two ponds (fig. 11). 

The velocity of sla·bs of darkened crust that were rafted 

from the outlet of the southwest pond to the central 

pond was approximately 3 miles per hour. The vents 

in the central pit had been completely submerged by 

the rising lava, and by 01h3Qm on July 11 the activity 

was reduced to a small number of low, surging boils. 

In the southwest pit, the vent at locality C was also 

covered by the rising liquid lava, but the fountain continued to blast through the pond to heights of 50-100 

feet. Composition of the pumice ejected at 02hOQm is 

given in column 2, table 4. 

Soon thereafter the fountains surging through the 

pond above the vents in the central pit began to pulsate 

and for more than 1 hour created a remarkable wave 

pattern across the pond. By 03h2Qm, however, activity 

from the vents beneath the central pond was reduced 

to a feeble bubbling, and a crust formed over most of 

its surface. As the crust thickened and became more 

rigid, agitation of the liquid in the pond induced hy an 

occasional surge from the vents locally forced lava out 

over the surface and formed a new crust. 

At daybreak the lava was still largely confined to the 

separa,te ponds in the two collapse pits, and there were 

minor overflows onto the main floor north of the central 

pit (fig. 10). The large arcuate cracks immediately 

peripheral to the central pit were almost completely 

covered. The lava river pouring out of the southwest 

pit flowed between natural levees which it had built 

up on the broad area of new lava between the two 

ponds, and another smaller stream was beginning to 

encircle the 1952 cones on their north side. 

The height of the main fountain at locality A decreased from 300-600 feet in the morning to about 200-

300 feet throughout the rest of the day. Pumice and 

spatter throw·n out by the fountain built up spatter 

ramparts around the vent, and thus the orifice was continually being raised above the level of the pond. 
Dl4 SHORTER CONTRIBUTIONS TO GENERAL GEOLOGY 

FIGURE 11.-Elruptlve activity In Halemaumau crater at approximately 23•3om, July 10, 1961. Lava erupted from the vents at locality .A 

(out of picture to the left) and locality C (left) has filled the southwest collapse pit, and a lava river carries the overtlow to the central 

collapse pit. (See fig. 10 for localities). Lava fountains at the vents at locality D (right) In the wall of the central collapse pit are 

shooting to heights of 150 feet. View Is toward the north.from the southwest rim of Halemaumau. 

Abundant pumice was also :falling on the rim of 

Halemaumau above the :fountain and on the caldera 

floor toward the southw~t . . The surging :fountain 

at locality C continued unchanged, whereas at 

locality D, in the central pond, activity increased 

slightly during the morning, and occassional blasts 

of spatter reached heights as great as 50 feet. · 

During the morning, the two ponds coalesced, leaving 

the 1952 cones and the cracked pressure ridge connecting the two collapse pits as an island in the rising lava 

lake. At noon on July 11 a large part o:f the lake over 
THE 1 9 61 ERUPTION OF KILAUEA VOLCANO D15 

FIGURID 12.-Eruptive activity in Halemaumau crater at approximately 13h30m, July 11, 1961. Lava pond over the central collapse pit Is 

confined by a natural rubble levee 10-15 feet high. In left background the lava river pours from base of main fountain (loc. A, fig. 

10), and In the central poml a small burst of spatter shoots above the vents at locality D (right). View is toward the west from the 

east rim of Halemaumau. 

the central pit was impounded by a natural rubble levee 

which maintained the lake surface more than 10 feet 

a:bove the surrounding terrain (fig. 12). This transient 

feature was formed by lava spreading outward from 

the agitated boiling area at locality D to the margin of 

the lake, where it plunged downward behind the levee 

and deposited its load of frozen crustal fragments. 

Small secondary fountains that were produced where 

the lava plunged downward behind the levee added 

minor amounts of reinforcing spatter to the harrier. 

Through the early afternoon, lava flows disoharged 

from the mouth of the river advanced rapidly eastward 
D16 SHORTER CONTRIBUTIONS TO GENERAL GEOLOGY 

FIGURE 13.- Sa.me view as in figure 12, one-h·alf later, showing the r aieed lava pond · over the central collapse pit being covered by ftows 

discharging from the lava river. 

across the lake, and within a few hours all vestiges of 

the raiserl pond had boon covered by new flows (fig. 13). 

This confinement of a lava lake by a levee of its own 

making has been observed many -times in Halemaumau 

and is evidently a common phenomenon of lava-lake 

activity (Macdonald, 1955). 

The conditions in Halemaumau at 18hOOm are shown 

in figure 14. By this time the lake had expanded laterally over a large part of the crater floor, leaving the 

pressure ridge and the 1952 cones as three isolated 

islands. Activity in the vent at locality D had decreased again by 17h00m, and at 21h35m activity at the 

vents at localities C and D had ceased. By 23h00m the 

one remaining fountain. at locality A, was averaging 

only 100 feet in height, and even it, occasionally, subsided to a massive center of boiling lava. 
THE 19 61 ERUPTION OF KILAUEA VOLCANO D17 

0 400 BOO 1200 FEET 

I I 

Extent of lava 

Cinder-pumice 

~ 

~ cone 

CLJ 

Active vents 

Lava ar.~d 

~ spatter cone 

of March 1961 

FIGURE 14.-Halemaumau crater at lSbOOm, July 11, 1961. 

During the night the lava--river changed course, and 

by morning on July 12 it was flowing in a broad stream 

almost due east between the 1952 cones and the pressure 

ridge, o:f which only the very tops still remained above 

the level o:f the lake (fig. 15). Pieces o:f darkened crust 

were rafted along this stream at about 6 miles per hour. 

'Throughout the day the surface o:f the lava lake rose 

steadily, and at 10h0()W it covered an area o:f about 70 

acres to a depth of 140 feet above tJhe central collapse 

pit. By 11 boom the :fountain had built up a large cinderpumice cone on the talus behind the vent, and slumping 

:from the cone into the vent occasionally deflected the 

spray o:f the :fountain to th~ east. The accumulation o:f 

spatter around the base o:f the :fountain continued to 

maintain t:he level of the vent above the level of tJhe lava 

lake. At night the lake surface was aglow :from the 

myriad of incandescent cracks that criss-crossed its sur-

:face. Lava oozed :from these surface cracks and from 

around the periphery of the lake, and crustal foundering was continually exposing large patches of incandescent, fluid lava. 

On July 13 at 00b30m the :fountain at locality A rose 

to heights o:f 800 feet and vigorously threw out large 

chunks o:f pumice as much as 1 foot across. Within 

a :few minutes, however, the fountain subsided to 

heights o:f 100-500 feet and continued at these heights 

for the rest of the night. By 11 boom the three islands 

were completely covered, and the broad lava river 

flowed directly over them (fig. 16). The lake surface, 

which covered most o:f the central nearly flat part o:f 

the main saucer-shaped collapse pit in Halemaumau, 

had increased to about 90 acres. An exceedingly active and probably higher area, which was marked by 

numerous lava oozes and local patches of crustal foundering, extended from the central deeper part o:f the 

lake northward to the margin of the lake. Spatter 

:falling on the south rampart of the enlarged cinder cone 

throughout the day :fed a number of viscous rootless 

flows that moved sluggishly down the outer slope of 

the cone and out over the lake (composition of pumice 

given in column 3, table 4). 

On July 14 the height o:f the fountain generally fluctuated between 100 and 300 feet, but at times the fountain diminished to a huge boiling mass . . About 23bOOm 

a new vent was first noticed at the base of the spatter 

rampart just north o:f the inain fountain. This vent 

discharged a small steady stream o:f lava that poured 

directly into the main river. 

Fountain heights continued to decrease on July 15, 

but the rate of lava extrusion remained about the same. 

By noon the lava lake was more than halfway up the 

steep part of the large saucer-shaped collapse pit of 

1960, and its surface, which now covered 101 acres, 

exhibited an intricate pattern formed by hundreds of 

small pahoehoe flow units (fig.17). 

In the afternoon it was evident that the rising lake 

was slowly encroaching upon the vent area, and by 

nightfall the lava river was running wide and slowly. 

In the disturbed area where the river sluggishly emptied into the central part of the lake, many "lightningshaped" cracks radiated out over the entire lake surface. 

Around the margin of the lake several large flows were 

active, and at about 20boom the first lava from the 
D18 SHORTER CONTRIBUTIONS TO GENERAL GEOLOGY 

FIGURE 15.- Eruptive activity In Halemaumau crater at approximately 15•oom, July 12, 1961. The main lava fountain, at base of new cinderpumice cone, Is about 200 feet high. The lava river pouring from ·base of fountain has changed cour~ (see figs. 12 and 13) and is running between the remnant 1952 cones (black arrows) and the 1960 pressure ridge (white arrow) . View Is towardl the northwest from 

the south rim of Halemaumau. 

lake began to pour into the outermost large peripheral 

subsidence crack of 1960 along the/ south side of the 

crater. 

A low massive fountain continued unabated throughout July 16, and an occasional deluge of spatter from 

the fountain fell on the cone around the vent. (Composition of pumice is given in column 4, table 4.) 

The small gushing vent had ceased erupting during the 

night and was no longer visible. By late afternoon 

lava was rapidly filling the peripheral subsidence crack 

along the south side of the crater and was beginning 

to flow into this crack on the north side. At 21 h30m 

the lake reached the level of the vent and forced the 

fountain to jet through an ever-increasing cover of 

liquid lava. This agitation at the vent occasionally 

sent out waves across the lake surface, adding more 

cracks to the maze of incandescent cracks already lacing 

the surface. 
THE 1 9 61 ERUPTION OF KILAUEA VOLCANO D19 

N 

I 0 400 800 1200 FEET Cinder-pumice 

~ 

~ 

cone 

CLJ 

Active vents 

Lava and spatter cone 

of March 1961 

FIGURE 16.- Ha1emaumau crater at 1l-•oom, July 13, 1961. 

At 031150m on July 17 the fountain was covered by 

the rising lake and died. For several hours a small 

secondary fountain played over the vent area as a small 

stream of lava poured back into the vent from the 

lake. Even after a stable crust formed over the vent, 

lava continued to drain from the lake. As the lake 

surface lowered, the crust continually foundered and 

reformed; often when large sheets of lava swept rapidly over the surface, small secondary fountains, produced by release of air trapped in the old- crust, played 

briefly from the fluid. By early afternoon, when all 

backflow appeared to have ceased, the central part of 

the lake and the area near the vent were distinctly 

lower than the rest of the lake. Around most of this 

area a scarp as much as 15 feet high was visible, and 

scattered over the subsided floor were many small islands, perhaps remnants af former pressure ridges and 

other solidified masses that had formed during the late 

stages of lake filling but which were not disturbed by 

crustal foundering (figs. 18 and 19). Once formed, 

many of these solidified masses continued to grow and 

served as degassing chimneys. 

The eruption lasted 16% hours less than 1 week. 

During this period the total volume of lava extruded 

was approximately 17.3 million cubic yards, which 

formed a new lava lake in Halemaumau 210 feet deep 

with a total surface area of about 112 acres. The progress of crater filling is shown graphically in the crosssection on figure 20. 

Pumice produced from the main lava fountain was 

carried as far as 2 miles southwest of Halemaumau by 

the northeast trade winds. It fell as a thin blanket 

ranging in thickness from a fraction of an inch downwind from the crater to more than 2 feet near the 

crater. On the caldera floor directly above the fountain area, strong, turbulent updrafts swept up out of 

the crater and continually reworked the light pumice. 

In places along the rim of the crater where downsweeping eddy currents were strongest, drifts of pumice 

more than 4 feet deep were formed (fig. 21). 

FLANK PHASE 

The 17 million cubic yards of lava erupted into 

Halemaumau in July did not reduce the pressure 

within the volcanic reservoir, and by September 1961 

the volcano appeared to be capable of imminent eruption. The degree of tumescence of the summit of 

Kilauea was approaching that which prevailed before 

the flank eruption of early 1960, and the rate of tumescence was considerably greater than at that time 

(fig. 3). 

At 121136m on September 21 a swarm of large, shallow 

earthquakes accompanied by strong harmonic tremor 

began to emanate from the vicinity of N apau Crater on 

the east rift zone of Kilauea Volcano 7 miles from 

the summit. The earthquakes and tremor continued 

through the afternoon; about 30 quakes were reported 

felt by residents of the National Park and of the small 

community of Volcano, 2 miles east of the park. 
D20 SHORTER CONTRIBUTIONS TO GENERAL GEOLOGY 

FIGURE 17.-Eruptlve activity In Halemaumau crater at approximately 12•oom, July 17, 1961. Relatively level lava lake covers 101 acres, 

and the lava river pouring from base of fouLtaln flows d'Own only a slight gradient. Mauna Loa Volcano Is visible on the western 

horizon. VIewpoint Is the same as In figure 12. 

By late afternoon the number and intensity of the 

earthquakes decreased, and the harmonic tremor subsided. A rapid detumescence of the summit of Kilauea 

appears to have accompanied the earthquakes and 

tremor. The permanent short-base tiltmeter at Uwekahuna indicated that in the 24 hours from 09hQQm on 

September 21 to 09hQQm on September 22 the summit lost 

more than one-half the inflation it had undergone during the previous 14 months. Moreover, deflections of 

the traces of the horizontal-component Press-Ewing 

seismographs at U wekahuna indicate that much of this 

subsidence occurred in 1 hour (fig. 22). These instruments showed marked deflection beginning at 13h3Qm, 

becoming very rapid at 13h55m, and tapering off by 

14h34m. It was evident that magma was moving rapidly 

from its reservoir beneath the summit of Kilauea, but 

the time or location of ·a possible outbreak could not be 

determined. 
THE 19 61 ERUPTION OF KILAUEA VOLCANO D21 

N 

1 

0 400 800 1200 FEET 

1·•········1 Extent of lava 

Cinder-pumice 

~ 

~ 

cone 

Lava and 

~ spatter cone 

of March 1961 

FIGURE 18.- Halemaumau crater on July 18, 1961, at the end of the 

third summit phase of the 1961 eruption. 

Next morning (September 23) before sunrise, a glow 

in the east was seen by tourists at the Volcano House 

Hotel and a strong smell of wood smoke, at times mixed 

with a slight odor of sulfur dioxide pervaded the summit area. Unfortunately, however, most of the summit 

region and the east rift zone was covered by a low heavy 

cloud bank. By 06h45m the clouds over the area south 

of the summit had dissipated, and a hazy band of 

brownish-gray volcanic fume extending southwestward 

for almost 15 miles was revealed. 

The first ll!ttempts to locate the apparent outbreak 

were not successful. Puu Huluhulu, a cinder cone on 

the upper east rift zone, was clim'bed at 08hOOm, and 

although visibility from its top was less than onequarter mile owing to heavy overcast, wood smoke and 

volcanic gases were strong enough to cause eye irritation. Further reports of glow over the east rift zone, 

the earliest of which was observed at 04h30m, soon began 

to be received at the observatory; and at about 08hOOm 

a pilot on a regular tourist flight saw lava fountains, 

through a 'break in the clouds, near Kalalua Crater, 12 

miles east of the summit. The fountains were feeding 

a small lava flow moving northward. 

Through the cooperation of the Hawaii National 

Guard, our first flight over the east rift zone, at 12h00m, 

revealed a number of discontinuous fissures, some as 

long as 1,000 feet, extending from west of Napau Crater 

to east of Kalalua Crater, a distance of approximately 

9 miles (fig. 23; see also fig. 24). There was no lava 

fountaining, but all fissures were emitting copious steam 

and blue-tinted volcanic fume, and around three of the 

fissures small pads of new lava were visible. 

At 14hOOm a ground party reached the westernmost 

of the steaming fissures between N apau and Makaopuhi 

Craters. This fissure, a few feet wide and about 700 

feet long, was emitting steam and minor volcanic fume. 

The heat, as well as sulfur deposited by the fume, had 

killed the vegetation within a few feet of the crack. 

As most of the active part of the rift was in nearly 

impenetrable rain forest, only the westernmost flow of 

September 22 was examined. However, aerial reconnaissance and photography during the eruption was 

adequate to map the flows and estimate their volume. 

Lava had been extruded from six of the newly formed 

fissures (fig. 24), but the resultant flows were all small; 

they covered a total of only 16 acres and comprised 

about 0.15 million cubic yards of new lava. As most of 

these flows swept through the jungle, the trees were 

burned off at their bases and the unburned upper parts 

fell on top of the flow. The result is a thin, shelly pahoehoe flow covered by entangled fallen trees. 

On September 22 tremor recorded at the summit 

abated somewhat, but tremor recorded at Pahoa, near 

the east rift zone 24 miles from the summit, intensified 

(fig. 22). At 17h02m a large shallow earthquake in the 

vicinity of Kalapana, 6 miles southeast of Kalalua 

Crater, rocked the entire island. These events suggested that the next outbreak would be farther down the 

rift, east of the earlier surface activity. 
D22 SHORTER CONTRIBUTIONS TO GENERAL GEOLOGY 

FIGURE 19.-Halemaumau crater at approximately 12b30'" July 17, 1961, less than 9 hours after the cessation of fountaining. Backtlow has 

lowered the central part of the lake about 15 feet, leaving a number of islands protruding above the surface. 'l'wo light-gray areas (near 

vent and at left center) are tluid lava welling up over the surface. Viewpoint is the same as in figures 12 and 17. 

At about lOhOOm on September 23 a series of audible 

explosions heralded the resumption of eruptive activity 

along a discontinuous series of rifts 2% miles long, 

centered about 5 miles east of the activ ity of the preceding day. Most of this activity was very shortlived, as 

at 10h20m the only fountains observed from the air were 

along a single erupti ,·e fissure, more than 700 feet long, 

northwest of Heiheiahulu Crater (fig. 24). ·when first 

seen, these foll'ntains \Yere srriall, but by 10h30m they were 

shooting to heights of 300 to 400 feet (fig. 25). From 

the fountains, thin but voluminous lava flows began to 

spread rapidly through the dense forest and down both 

the north and south flanks of a slight ridge which marks 

the east rift zone in this area. At 121130m the Civil Defense Agency ordered evacuation of towns along the 

seacoast south of Pahoa. Most of the lava poured back 

into a large sumplike crack several hundred feet southeast of the eruptive rift, however, and no extensive flow 

resulted. 
THE 1 9 6 1 ERUPTION OF KILAUEA VOLCANO D23 

A A' 

3800' 

3600' 

3400' 

3200' 

3000' :, :~ 1

' Southwest Central collapse pit 

2800, .__ _ _ ___:C::::OI.:.::Ia!:.::ps:.::.e..<::pic.:... t __ :::_:: CO::.:; IIa;:.c: P;c:: Se..!:p::..:.it _ ___ _ __ __, 

EXPLANATION 

LAVA LAKE LEV EL 

lOh oorn, July 18 Ed 

~ 

Ci nder-pumice cone 04' oom' July 17 - ------

llh oom. July 15 --------- --

11" oom' July 13 ---------------

18h oom. July 11 --------------

06hoom,Julyll -· Lava of Feb-Mar 1961 

0 400 800 1200 FEET 

DATUM IS MEAN SEA LEVEL 

VERTICAL EXAGGE RATI ON X 2 

FIGURE 20.-Cross l!ect!on of Halemaumau along A-A' of figure 2 showing formation of the lava lake during the third summit eruptive 

phase. 

The strong fountaining near Heiheiahulu Crater 

ceased about 01 hQQm on the morning of September 24. 

At this time harmonic tremor subsided at all the seismograph stations on Kilauea, and the rift zone was relatively quiet. Reconnaissance from a helicopter later in 

the morning revealed no activity along any of the erupting rifts of the preceding day, except the emission of 

volcanic fume. In the large fountain area (fig. 25) the 

vent fissure was brightly incandescent for a distance 

of about 600 feet, but elsewhere the vents were dark. 

Six new lava flows, covering a total of approximately 

175 acres, were produced during the September 23 activity. For convenience in description, the three largest 

are called, from west to east: Heiheiahulu flow (148 

acres, Kaumuki flow (16 acres), and Jonika flow (9 

acres). (See fig. 24.) Associated with the flows 

throughout this part of the rift zone are a large number 

of new cracks and faults, many of which discharged 

only volcanic fume. The largest of these faults can be 

detected on aerial photographs of the region taken 

shortly after the eruption, and, where they produced 

displacements large enough to be seen clearly, they 

outline a series of grabens parallel to the rift zone. 

Lava tree molds, some standing 14 feet high, are 

abundant on the flows of September 23. They were 

produced where fluid lava flowing through the forest 

became chilled around the larger trees. After most of 

the lava drained away and the lava surface was lowered, 

the vertical molds around the trees, most of which had 

burned away, remained standing. The tree molds are 

especially well preserved on the J onika flow and have 

been described in another paper (Moore and Richter, 

1962). 

Activity resumed again at about 14h15m on September 24, when a number of small lava fountains began 

to play from a 500-foot-long fissure 1 mile northeast of 

Kalalua Crater and southwest of the activity of the 

previous day (fig. 24). The fountains were generally 

less than 50 feet high, and most of the lava fell hack 

into the vent or onto the flanks of the two small elongated cones which were built up. Later in the evening 

a short-lived series of large shallow earthquakes originating in the Kalapana area (fig. 1) shook the island. 

Three of these quakes were felt over the entire island, 

and the largest, at about 19h3Qm, had a magnitude of 5.5. 

By early next morning (September 25) the eruption 

was over. Minor displacement on the faults at the east 

end of the eruptive area continued at a decreasing rate 

for a few days, and great amounts of steam and fume 

boiled from the vents for at least 2 weeks. The rapid 

and dramatic subsidence of the summit, which resulted 

from the withdrawal of about 70 million cubic yards 

of magma, halted very abruptly on September 25 more 

or less contemporaneously with the cessation of fountaining (fig. 22) . 

VOLUME AND RATE OF EXTRUSION OF LAVA 

The total volume of lava extruded during all four 

phases of the 1961 eruption was approximately 21.2 

million cubic yards (table 1). However, both during 

and immediately after most of the eruptive phases, part 

of the lava, totaling about 2.9 million cubic yards, was 

withdrawn, leaving a net accumulation of approximately 18.3 million cubic yards of new lava on the surface. The greatest accumulation occurred during the 

week-long third summit phase, when 17.3 million cubic 
D24 SHORTER CONTRIBUTIONS TO GENERAL GEOLOGY 

FIGURI!l 21.-Drifts of pumice along the wuthwest rim of Halemaumau (right) on the floor of Kilauea caldera. Kilauea caldera wall Is 

visible in the background. 

yar.ds, or about 82 percent of the total volume extruded 

during the entire eruption, filled the bottom of Halemaumau. The 1.9 million cubic yards of lava remaining on the · surface after the 3-day flank phase is distributed among 13 small flows scattered along a 12-mile 

segment of the east rift zone. Of this amount, more 

than 90 percent (1.7 million cubic yards) is in the six 

flows extruded on September 23, the second day of flank 

eruptive activity. The Heiheiahulu flow of September 

23, largest of the flank flows, contains about 1.5 million 

cubic yards, more than three times the volume of lava 

in the other 12 flows. 

The rate of lava extrusion varied considerably between different eruptive phases, but, with the exception 

of the flank eruption with its many outbreaks, it was 

fairly constant during a given phase. Table 2 shows 
THE 1 9 61 ERUPTION OF KILAUEA VOLCANO D25 

I 

HARMONIC 

Relative om 

6 seismoor 

TREMOR 

plitude at 

aphs 

ERUPTION s Relative vo 

lovo extrud 

lumes of 

ed 

DETUMESC ENCE 

Ground tilt 

Uwekohuna 

ing at 

.. 

.. 

\"-. 

- Mauna Loa 

- Ahua 

1-- Desert 

North Pit 

~ Pahoa 

- Hilo 

0.15 a 0.01 Million cubic yards 

- -

~ 0 . 

r---s-- No. 

FAULTING 

Growth of 

1/4 mile w 

DATE 

I new fault scarp 

est of Jo

1

nika flo~ 

2.0 2.1 2.2. 

~ 

~ 

~ff ~ 

,, ~ 

/ 

23 24 25 2.6 ~:?_____~ 8 

SEPTEMBER 1961 

FIGURE 22.-Chronology of events during the September 1961 flank 

eruption. 

the volume and rate of lava extrusion and withdrawal 

as measured daily by vertical angles from the rim of 

Halemaumau for the third summit phase. Rates of extrusion based on these daily measurements ranged from 

74,000 to 149,000 cubic yards per hour; the average 

rate over the entire week was 114,000 cubic yards per 

hour. This rate, which was the highest measured for 

TABLE 1.-Volume and rate of lava eilltrusion durirtu the 1961 

eruption of Kilauea 

Volume of Average Volume of Volume of 

lava rate of lava lava re- extruded extrusion withdrawn malnlngon (cubic (cubic (cubic surface 

yards) yards per yards) (cubic 

hour) yards) 

First summit phase (07h07m- 15h08m, Feb. 24, l!l61) _. ____ . __ . 320,000 40,000 290,000 30,000 Second summit K}'ase, (22h00m, Mar.3-20h00m, ar. 25, 1961) ___ 350,000 660 0 350,000 Third summit phase (20h15m, July 10-03h50m, July 17, 1961) ___ 17,300,000 114,000 1,300,000 16,000,000 Flank phase (04h30m, Sept. n. Sept. 25, 1961) ... __ _____________ 13,200,000 ------------ 1 1,340,000 1,860,000 

TotaL.-------------------- 21,170,000 ------------ 2,930,000 18,240,000 

1 Based on visual estimates only. 

any comparable length of time during the eruption, is 

similar to extrusion rates observed in past Halemaumau 

eruptions. The lowest average extrusion rate, on the 

other hand, was 660 cubic yards per hour during the 

relatively feeble 3-week-long second summit phase. Except for the periods of lava lake activity in Halemaumau prior to 1924, this extremely low rate is probably 

unique for a complete eruptive phase in the recorded 

history of Kilauea. 

TABLE 2.-Volume and rate of lava eilltruswn and withdrawal 

during the third summit eruptive phase 

Date 

July 1! ______________ 12 ___________________ 

13.------------------ 14_ ------------------ 15_ ------------------ 16_ ------------------ 1717 _ 

____ ------------------ _______________ 

18 ___ ---------------- For period of 

extrusion only _____ 

[Eruption began at 20h15m on July 10] 

Time 

10b0Qm 

10b0Qm 

l!hOOm 

12b0Qm 

llbQOm 

llbOQm 

03h5Qm 

lQbOOm 

10b0Qm 

------------

Duration 

since last measurement 

(hours) 

13H 

24 

2!l 

25 

23 

24 

16~ 

6~ 

24 

151~ 

Volume 

(cumulative) of new lava 

Volume (cumula- Average tive) of rate lava (cubic 

withdrawn yards per hour) 

Cubic yards 

2,000,000 0 145,000 

5,400,000 0 142,000 

7,800,000 0 96, COO 

10,100,000 0 92,000 

11,800,000 0 74,000 

14,800,000 0 125,000 

17,300,000 0 149,000 

16,500,000 800,000 128,000 

16,000,000 1,300,000 21,000 

17,300,000 ------------ 114,000 

During the flank phase, visual estimates of the rate 

of extrusion range from a few thousand to 200,000 cubic 

yards per hour for the different eruptive rifts. The 

most voluminous outpouring of lava, 200,000 cubic 

yards per hour at the Heiheiahulu vents, which continued for about 15 hours, is similar to rates measured 

during the 1960 and 1955 flank eruptions of Kilauea. 

Backflow of lava into source vents and other fissures was common during all but the second summit 

phase. In the first summit phase about 90 percent of 

the extruded lava poured back into the eruptive vents 

within a few hours after the cessation of activity. 

During the flank phase lava disappeared below the surface apparently at aJll tJhe major outbreaks. Most of 

the backflow occurred along cracks and fissures that 

paralleled the structural grain of the rift zone but 

which were generally unrelated to the immediate 

source vents. Some of these cracks and fissures marked 

fault scarps adjacent to the eruptive rift, but many 

were long open tension cracks tha.t showed no evidence 
D26 SHORTER CONTRIBUTIONS TO GENERAL GEOLOGY 

FIGUR!l 23.-Aerial view toward the southwest, photographed directly above Kalalua crater, showing the upper part of the active zone along 

Kilauea's east rift zone at 12•oom on September 22. The low secondary lava cone, Kane Nul o Hamo, is visible just below the skyline on 

right, and Napau Crater is between the two farthest vents. Note the en echelon arrangement of the vents. 

of vertical or lateral movement. Maximum backflow 

occurred a:t the Heih'eiahulu outbreak, where the rate 

of withdrawal appeared to equal the rate of extrusion 

during the greater part of the eruption. 

TEMPERATURE OF THE LAVA 

Temperatures of the erupting lava were measured 

throughout the three summit eruptive phases by two 

incandescent filament-type optical pyrometers. No 

measurements were made during the flank phase owing 

to the inaccessibility of the eruptive vents. All observations of the summit eruptions, with the exception 

of those of the first phase, were made at night from 

the rim of Halemaumau, at a distance of 600- 800 feet 

from the vents. The observed temperatures are listed 

in table 3. No corrections have been made for adsorption between fountain and pyrometer or for emissivity 
THE 1 9 6 1 ERUPTION OF KILAUEA VOLCANO 

TABLE 3.-Lava temperatures during 1961 eruption ot Kilauea 

Eruptive period Temperature ( '0) 

First summit p-hase _____________ ______________ __ 1, 095--1, 125 

Second summit phase ___________________________ 1, 096-1, 114 

Third summit phase---------------------------- 1, 08'5--1, 127 

of the lava, and abnormally low readings resulting 

from visible fume or mist between the pyrometer and 

the vent have been omitted. 

Lava temperatures in the short first summit phase 

were necessarily measured during daylight hours. Although care was exercised to read temperatures only 

when the lava fountains were in the shade, the temperatures listed may be slightly high because of reflected 

sunlight. During the second summit phase, conditions 

were excellent for optical pyrometer measurements. 

The boiling caldron of lam over the vent, with a r~atively small orifice opening to the surface, formed a 

nearly perfect cavity-type black body. Temperatures 

of lava in the third summit phase were measured in 

the core of the lava fountain where heat loss by radiation was held at a minimum (Ault and others, 1961). 

As discussed in the following section on petrography, 

the temperature range of 1,085°-1,127° C for the summit lavas seems to correlate closely with their chemistry and mineralogy. Throughout the br-ief first phase 

and the much longer second summit phase there was 

no observed variation in temperature with time. However, the possibility of consistently high measurements 

during the first phase and the lack of measurements, 

owing to poor visibility, through the early part of the 

second phase may have precluded the detection of any 

systematic temperature change. In the more voluminous third phase, the range of temperatures increased 

from 1,085°-1,087° C during the first 4 hours of eruption to 1,106°-1,127° C during tlhe rest of the eruption. 

This change apparently resulted from the withdrawal 

of heat from the early lava as it rose to the surface 

through the relatively cool rocks in the higher part of 

the volcanic edifice. 

PETROCHEMISTRY 

The lavas of the 1961 eruption are tholeiite basalts 

and tholeiite olivine basalts. The distinction between 

the two types is based chiefly on the amount of modal 

olivine present as phenocrysts; those lavas containing 

less than 5 percent olivine are called basalts, whereas 

those containing more than 5 percent olivine are called 

olivine basalts (Macdonald, 1949). Although none of 

the 1961 lavas examined were completely devoid of olivine phenocrysts, the olivine content in the lavas 

erupted at the summit is less than one-half of 1 percent 

by volume. The groundmass of the

-lavas erupted during the flank activity and the related pyroclastic ejecta 

~ 

~ 

0 

:> 

< 

I 

z 

0 

f-

<0: 

z 

..: 

..J 

a. 

X 

w 

<J) 

"j 

"' 

N 

0 

0 

0 

D27 

.<:1 "'

.... 

"' "' 
D28 SHORTER CONTRIBUTIONS TO GENERAL GEOLOGY 

FIGURE 25.- Lava fountains 300 feet high at the Heihelahulu tlow, 17hOOm on September 23. Note trees burning around the active margin 

of the tlow. 

from both the summit and flank activity range from 

completely glassy in the pumice and in rapidly cooled 

tops of flows to intersertal in more slowly cooled interiors of flows. Very small laths of plagioclase and 

small poorly formed stubby prisms of clinopyroxene 

constitute the groundmass minerals. No hypersthene 

was observed in any of the sections studied. 

Eight new chemical analyses- four from the first 

and third summit eruptive phases and four from the 

flank eruptive phase- are presented in table 4, together 

with the calculated norms for all the analyzed samples 

and the modal olivine content for the flank lavas. 

The summit lavas, as indicated by the chemical analyses of pumice thrown up on the rim of Halemaumau by 

the lava fountains, are all very similar in composition. 

A sub~le difference in content of Si02, Al20 3, and MgO 

between the lavas of the first and third summit phases 

may reflect changes caused by the removal of minor 

olivine or the assimilation of feldspar and glass, or a 

combination of both. Within the week-long third summit phase, however, there was virtually no change in 

the composition of the 17.3 million cubic yards of lava 

erupted. Samples collected a few hours after the beginning of eruption (analysis 2, table 4), during the middle 

of the eruption (analysis 3, table 4), and within a few 

hours of the cessation of activity ( amalysis 4, table 4), 

do not vary in silica composition by more than 0.03 of 1 

percent and for all intents and purposes are identical 

in this respect. Thin sections of the pumices of the 

third summit phase reveal a few small (as much as 1 mm 

in diam.) phenocrysts and micro phenocrysts of sharply 

euhedral olivine (Fa14 ) ; heavy-mineral concentrates 
THE 1 9 61 ERUPTION OF KILAUEA VOLCANO D29 

from crushed bulk samples of the pumice contain a few 

small crystals of clinopyroxene as well as olivine. 

Smaller bulk samples of pumice from the first summit 

phase also contained olivine phenocrysts of approximately the same composition as those in pumice of the 

third phase, but they apparently were lacking in 

clinopyroxene. 

TABLE 4.-Chemical analyses, norms and modal olivine of lavas 

from the 1961 eruption of Kilauea 

[Analysts: E. L. Munson (samples 1-4) and C. L. Parker (samples 5-8)] 

Chemical analyses 

$i02----------- 50.22 50.36 50.39 50.39 50.26 

AbOa •••. ------ 13.64 13.70 13.69 13.69 13.87 

Fe20a ... ------ 1. 29 1. 44 1. 41 1.28 2.94 

MgO FeO ... -------- 9.63 9.54 9. 59 9.68 8.62 __________ 7. 74 7.54 7.49 7.53 6. 75 cao __________ 11.34 11.31 11.36 11.36 10.88 Na20 __________ K.o 2.32 2.36 2.33 2. 31 2.45 ___________ .55 .54 . 53 .54 .59 

H20+--------- .04 .00 .02 .04 .02 H.o-_________ .04 .01 . 01 .00 .02 

Ti02.--------- 2. 76 2. 77 2. 76 2. 78 3.04 

MnO P20s. --------- .27 .'17 .27 .27 .30 __________ .17 .17 .17 .17 .18 

C02.---------- . 01 .01 .00 .01 .05 

CL .. ---------- .02 .02 .02 .02 .02 

F ------------- . 04 .04 .04 .03 .04 ---------- 100.08 100.08 100.08 100.10 100.03 Less o ________ .03 .03 .03 .02 .02 ---------- TotaL •• 100.05 100.05 100.05 100.08 100.01 

Norms 

Q _____________ Or 0.00 0.96 0.96 1. 02 2.88 ____________ 3.34 2. 78 2. 78 2. 78 3.34 

Ab------------ An 19.91 19.91 19.91 19.39 20.96 ____________ 24.74 25.30 25.30 25.58 25.02 

DL Hy .•• -------- 24.23 23.31 23.80 23.58 21.89 ____________ 19.99 19.56 19.22 19.82 14.00 

OL •• ---------- 0.00 0.00 0.00 0.00 0.00 

n Mt. _____________ ----------- 1.86 2.09 2.09 1.86 4.18 

5.32 5.32 5.32 5.32 5. 78 

AP------------ 0.67 0.67 0.67 0.67 0.67 ---------- 100.06 99.90 100.05 100.02 99.95 

Modal olivine 

50.38 49.96 

13.68 13.30 

3.36 2. 75 

8.06 8. 73 

7.30 8.56 

10.57 10.34 

2.45 2.34 

.59 .57 

.01 .04 

.03 .02 

3.02 2.91 

.30 .25 

.17 .18 

. 01 .01 

.02 .02 

.04 .04 

---- 99.00 100.02 

.02 .02 ----

99.97 100.00 

3.36 1. 32 

3.34 3.34 

20.96 19.91 24.46 23.91 

20.80 20.36 

15.43 20.84 

0.00 0.00 

4.87 4.18 

5. 78 5.47 

0.67 0.67 ---- 00.90 100.00 

I 

50.22 

13.28 

1.69 

9. 70 

8.44 

10.28 

2.39 

.59 

.06 

.01 

2.92 

.26 

.18 

.02 

.01 

.04 --

100.09 

.02 

--

100.07 

0.1 8 3.34 

20.44 

23.63 

20.73 

23.0 

0.0 5 

0 2.55 

5.47 

0.67 

100.0 6 

OL.----------1 (') I <'> I <'> J <'> I o. 31 o. 41 5.1 I 1. 3 

1. Tholeiitic basaltic pumice erupted Feb. 24, 1961, from Halemaumau. 

2. Tholeiitic basaltic pumice erupted 02hOOm, July 11, 1961, from Halemaumau. 

3. Tholeiitic basaltic pumice erupted 12hOOm, July 13, 1961, from Halemaumau. 

4. Tholeiitic basaltic pumice erupted 13hOOm, July 16, 1961, from Halemaumau. 

5. Tholeiitic basalt erupted Sept. 22, 1961, Kilauea east rift zone, 9 miles from summit 

(lava flow one half mile northeast of Napau Crater). 6. Tholeiitic basalt erupted Sept. 23, 1961, Kilauea east rift zone, 17 miles from summit 

(Heiheiahulu lava flow). 7. Tholeiitic olivine basalt erupted Sept. 23, 1961, Kilauea east rift zone, 18 miles 

from summit (Kaumuki lava flow). 

8. Tholeiitic olivine basalt erupted Sept. 23, 1961, Kilauea east rift zone, 19 miles 

from summit (Jonika lava flow). 

1 Not determined. 

Lavas from the flank eruptive phase, on the other 

hand, are markedly different from those extruded during the summit phases and, as a group, show an indistinct but apparently systematic change along the rift 

zone. The flank lavas are higher in total iron, titania, 

and soda and are lower in lime than the summit lavas of 

similar silica content. This difference is also reflected in 

the norms of the two groups, as magnetite, ilmenite, and 

albite are richer and diopside is poorer in the flank 

lavas. The systematic change in composition of the 

flank lavas along the rift zone is best shown by the 

progressive increase in normative hypersthene and 

modal olivine away from the summit. At the westernmost flow (analysis 5, table4), just east of Napau Crater 

(fig. 24) , the lavas are macromineralogically simila.r to 

those erupted at the summit but contain only 15 percent 

normative hypersthene. Nine miles farther down the 

rift, at the Heiheiahulu flow (analysis 6, table 4), botlh 

modal olivine and normative hypersthene are slightly 

more abundant; some of the olivine phenocrysts are as 

much as 4 mm in diameter. At the Kaumuki (analysis 

7, table 4) and J onika (analysis 8, table 4) flows along 

the extreme east end of the 1961 outbreak zone, the increase in olivine content and normative hypersthene is 

even greater. In the J onika flo·w, \Y her:e conspicuous 

phenocrysts of olivine as large as 5 mm in diameter constitute more than 7 percent by volume of the lava, normative hypersthene reaehes a maximum of 23 percent. 

Some of the larger olivine phenocrysts in the Jonika 

and Kaumuki flows appear to have undergone incipient 

resorption around their margins but most are euhedral 

and a few of the smaller phenocrysts are skeletal. The 

fayalite content of the olivine decreases from Fa1s at 

the westernmost flow to Fa12 in the larger phenocrysts 

at the Jonika flow. As in the westernmost flow, however, the smaller skeletal olivine phenocrysts in the 

J onika and Kaumuki flows may represent a more fayalitic olivine phase. Microphenocrysts of clinopyroxene 

(a pprox, W o40En50Fsto) and plagioclase feldspar 

( An6o-64) are present in all the flank lavas in amounts 

ranging from a few tenths of 1 percent to 3 percent by 

volume. 

The difference in composition between the flank and 

summit lavas and the change in composition of the 

flank lava with respect to distance from the summit 

is well shown on the CaO variation diagram on figure 

26. CaO was chosen as a reference base ( abscissa) in the variation diagram because of its 

relatively wide range in the 1961 lavas (10.28-

11.36 percent) and its sensitivity to slight 

changes in olivine content. Superposed on the 

diagram are the control lines 1 for olivine ( F~s), 

augite (Wo40En49Fs11 ), and plagioclase (An6a); the 

augite-plagioclase control "field" is stippled. Assuming that the lava erupted during the third and final 

summit phase represents the "parental" magma of the 

flank lavas, one may conclude from the variation dia.-

gram that the compositional shift between the last summit lavas (large open circle) and first flank lava (No. 

5) could not have been brought about by either the 

1 Compositions of the control minerals are from the following sources : 

Olivine, Murata and Richter (1961, table 1, analysis 10) ; augite, Muir 

and Tilley (1957, table 4, analysis 4a) ; plagioclase, Hess (1960, table 

10, analysis EBL41). 
D30 SHORTER CONTRIBUTIONS TO GENERAL GEOLOGY 

addition or loss of olivine. The shift does, however, 

appear to be controlled by the removal of augite and 

minor plagioclase. On figure 26 the field between the 

augite and plagioclase co~trol lines indicates the effect 

which removal, or addition, of a mixture of these two 

constituents will have on a liquid similar in composition 

to the lavas of the third summit phase. Upon removal 

of a mixture of augite and plagioclase, the composition 

of the resultant liquid will shift away from the augite 

and plagioclase compositions (to the left) along a line 

which, if extended back (to the right), lies in the control field. Regardless of the width of the control field, 

the shift due to augite-plagioclase removal is remarkably consistent and indicates that the proportion 

(roughly 5 to 1, augite to plagioclase) of these two 

minerals removed from the system was constant. 

Furthermore, the diagram also shows the nature and 

plausible mineralogic control of the chemical changes 

within the flank lavas. Invariably, the plots showing 

oxide in relation to CaO form a straight line parallel 

15 

12 

FeO 

11 Fe:o ~-=-oiMne-----=::::::::::::::~ 

en 10 LLJ 

0 

x 

0 9 

0:: 

LLJ 

~ 8 0 

1-

~ 7 (.) 

0:: 

LL.I 

a. 6 

5 

4 

3 

2 

9o.o 

Summit lavas 

0 

Flank lavas 

Numbers correspond to analyses 

in table 4 and are in order of 

?loq\oclose 

Augite 

12.2 

FIGURE 26.-CaO variation diagram of 1961 lavas showing the olivine, 

augite, and plagioclase control lines. Stippled area denotes control 

"field" of mixtures of augite and plagioclase. Heavy arrow shows 

!Shift in composition from last summit lavas to first flank la.vas, and 

dashed line denotes trend of flank lavas. 

to the olivine control line. Clearly, these data, together with the norms and olivine modes of the flank 

lavas, show that the magma feeding the flank eruptions 

became progressively enriched in olivine at lower elevations a way from the summit. 

In spite of the extremely limited range in silica content ( 49.96-50.39 percent) in the 1961 lavas, a similar 

chemical-mineralogical relation between the summit 

and flank lavas is evident on the normal SiOz variation 

diagram shown on figure 27. Again, as with the CaO 

variation diagram, the compositional shift between the 

late summit lavas and first flank lavas cannot be attributed to olivine control but rather to the removal 

of augite and minor plagioclase. As would be expected 

with such slight variations in silica content, the changes 

in composition within the flank lavas are not too clearly 

defined or orderly. Trend lines for CaO, FeO+ Fe20 3, 

N a20 and Ti02 do, however, parallel their respective 

olivine control lines, but for Alz03 and MgO the scatter 

is too great to reliably determine any trend. 

15 

14 

13 

12 

II 

en 10 

LLJ 

0 

§ 9 

0:: 

LLJ 

~ 8 0 

1-

z 

LLJ 

(.) 

0:: 

LLJ 

c.. 6 

EXPLANATION 

Summit lavas 

0 

Flank lavas 

Numbers correspond to analyses 

in table 4 and are in order of 

distance from summit FeO L..--.::=~..:.=:.:-==----..,----' 

5 I + Fe203 

3 

( O!jyine 

Olivin 

Olivine 

FIGURE 27.-Si02 variation diagram of 1961 lavas showing the olivine, 

augite, and plagioclase control lines. Stippled area denotes control 

"field" of mixtures of augite arid plagioclase. Heavy arrow shows 

shift in composition from last summit lavas to first flank lavas. 
THE 1 9 61 ERUPTION OF KILAUEA VOLCANO D31 

From the evidence shown on the variation diagrams, 

the following three steps are postulated to have taken 

place in the differentiation of the 1961 la.vas. 

1. Removal of early-formed magnesian olivine from 

magma in upper part of magma reservoir. 

2. Removal of augite and minor plagioclase from 

olivine-poor magma produced in step 1. 

3. Addition of magnesian olivine-rich magma to 

magma produced in step 2. 

The first step in the differentiation scheme affected the 

composition of both the summit and flank lavas; the 

second step accounts for the characteristic compositional difference between the summit and flank lavas; 

and the third step is responsible for the range in composition of the fla.nk lavas. 

It is not unreasonable, in view of the many analyses 

now available of Kilauean lavas, to assume that the primary magma within the shallow reservoir beneath the 

summit of Kilauea which fed the 1961 eruptive vents 

was of the appropriate composition ( 49-50 percent 

Si02 , 8-10 percent MgO) to induce crystallization of 

relatively large amounts of magnesian olivine. Between September 1960 and the flank eruption in September 1961, during which time the shallow magma 

reservoir was rapidly filling, olivine evidently began to 

crystallize and sink, and so the upper part of the reservoir was depleted of olivine (step 1). This upper part 

was then tapped by the summit eruptions in February, 

March, and July 1961, without undergoing any further 

marked differentiation. 

The differentiation which brought about the change 

in composition of the flank lavas very likely occurred 

during the early period of magma transit through the 

relatively cool rocks of the upper part of the rift zone. 

During passage along the 10- to 20-mile-long course, 

the magnesian olivine-free magma continued to crystallize in a normal manner. As temperatures decreased, 

first augite and then plagioclase, both accompanied by 

minor amounts of increasingly fayalitic olivine, began 

to a.ppear as crystalline phases in the mJt,gma. Most of 

the augite and some of the plagioclase were apparently 

removed somewhere in transit; therefore, the flank 

lavas are relatively poor in lime and rich in iron and 

titania, as compared with the summit lavas (step 2). 

This same type of differentiation has been invoked by 

Tilley and Scoon (1961) to explain the evolution of 

flank lavas of the 1955 Kilauea eruption. The nature 

of the mechanism which isolated these phases from the 

systemj however, remains obscure. The removal of 

augite and minor plagioclase might have been caused 

by gravity settling, or by the formation of a rind-on 

the cold walls of the conduit-enriched in the higher 

melting phases, particularly in augite, calcic plagioclase, and minor olivine. 

The last changes in the composition of the flank lavas 

are due principally to olivine control (step 3). Evidently as the flank eruption continued, and more and 

more magma moved down the east rift zone toward 

the vents, the deeper olivine-rich parts of the magma 

reservoir beneath the summit were tapped. Mixing 

of this olivine-rich magma with the early flank magma 

affected most of the lava extruded along the flank, the 

lava becoming progressively more mafic away from the 

summit while still reflecting the change caused by the 

removal of augite and plagioclase. 

Although the changes in composition due to olivine 

control (step 3) during the 1961 eruption are subtle, 

they are apparently somewhat analogous to the changes 

that occurred in the 1840 eruption of Kilauea, in which 

the lavas erupted near the summit were generally 

olivine poor and those erupted at lower elevations along 

the east rift zone were olivine rich. Macdonald (1944) 

has proposed that the upper 1840 vents tapped higher 

parts of the magma chamber from which olivine had 

been lost by gravity settling, whereas the lower 1840 

vents were fed by magma enriched in olivine from the 

lower part of the chamber. In part, this same phenomenon was observed during the summit phase (Kilauea 

Iki) of the 1959-60 eruption, in which the lavas changed 

from olivine poor to olivine rich in the first 3 days of 

eruption (Murata and Richter, 1962). During this 

early 3-day peri'Od the lavas were very similar in tempeT'ature (1,075°-1,130° C) and in composition (49.6--

50.1 percent Si02) to the 1961 summit lavas. After the 

first 3 days of t!he 1959 eruption, tJhe temperature increased rapidly, the Si02 oontent decreased, and phenocrystic olivine became very abundant. Thus it appears 

that the upper part of the Kilauea magma reservoir, 

whi!Oh erupts first, h11S b~en depleted of MgO and enriched in Si02 by the early crystallization and seittling 

of olivine. In the 1961 eruption, olivine-rich lavas were 

not erupted at the summit because the eruption ceased 'before the deeper magmas were tapped. However, olivinerich material was eventually tapped and erupted during 

the flank phase, but only after other compositional 

changes, brought about by the removal of augite and 

plagioclase, had occurred during the passage of magma through the relatively cool rift conduits leading 

from the summit reservoir to the site of the flank outbreak. 

GROUND MOVEMENTS DURING FLANK PHASE 

During the period of tremor which preceded the actual eruptive outbreak, the entire summit region of 

Kilauea subsided, presumably because the magma stored 
D32 SHORTER CONTRIBUTIONS TO GENERAL GEOLOGY 

in the reservoir beneath the caldera moved eastward 

within the rift zone. The fact that much of this subsidence occurred within 1 hour indicat.es that dmining 

of the reservoir was extraordinarily rapid. The magnitude of subsidence at the summit of the volcano is equal 

to a decrease of volume of rubout 70 million cubic yards; 

presuma:bly this decrease in volume was due to the withdrawal of that much magma from ·below the summit 

region into the rift zone. Only about 3.2 million cubic 

yards of lava were extruded, however, and the history 

of the rest is perplexing. It is very possible that the 

unaccounted magma is still in chambers within the rift 

zone or that it has been injected into deep fissures to 

form dikes along the rift zone. A 3-foot-wide fissure 

that is 14 miles long, or almost the totlllllength of the 

zone affected by the September eruption, and that extends to a depth of 2 miles could receive more than 70 

million cubic yards of magma. Although seismic evidence a.rgues strongly to the contrary, it is conceivable 

that the magma oontinued to drain eastward through the 

rift zone, feeding a submarine eruption somewhere 

along the 45-mile extension of the rift zone. 

Cracking and faulting along the rift began early in 

the eruption and continued for several days after extrusion of lava had ceased. Complete observation of 

this cracking and faulting unfortunately was not possible, and the precise time relations between cracking 

and faulting, seismic activity, and eruption are not fully 

known. However, it is known that some cracking occurred very early to produce the en echelon arrangement of fissures, which on the morning of September 23 

were observed from the air to be emitting steam and 

volcanic fume, and that some faulting continued for 

more than 3 days after all eruptive activity had ceased. 

The actual observed vertical displacement on a southfacing fault scarp which offsets a jeep trail between the 

J onika and Kaumuki flows is plotted on figure 22. A 

farmer of that area walked this trail at 13h30m on September 23 and saw no offset. At the time of his visit 

all the lava had been extruded at the Jonika flow but 

the fountains were still playing a few hundred yards 

toward the southwest at the Kaumuki outbreak. At 

14h()()m on September 24 the fault scarp was 7 feet high 

(fig. 28) ; the fault scarp continued to grow until September 28, when it reached a height of 10.8 feet (fig. 

30). Hence, this faulting occurred during and after the 

last part of the eruption. 

One of the highest new scarps is between the Kaumuki and the Heiheiahulu flows. This south-facing 

fault scarp is 20-25 feet high in some places and is commonly bordered on the downthrown side by a crack 

more tharn 25 feet deep below the surface of the downthrown block (fig. 29) Much of this fault has formed 

FIGURE 28..-Southeast-factng fault scarp midway between the Jonlka 

and Kaumukl ftows at 12hOOm on September 24. Vertical displacement Is 7 feet, with the southeast (left) side down. 

along the site of a preexisting scarp, and the latest 

movement has added from a few feet to more than 20 

feet to the height of the scarp. Because fresh lava 

which ponded in the newly formed depression at the 

base of the scarp has been offset to some extent by movement along the fault, it is apparent that faulting occurred both before and after the formation of the flow. 

The en echelon arrangement of the September eruptive rifts and steaming fissures is such that each successive break to the west is offset to the north. The same 

pattern was noted by Macdonald (1959, p. 57) in the 

southwestern vents area of the 1955 flank eruption, but 

he noted that the pattern is reversed in the northeastern 

vent area. 

All the vents, faults, and fissures visible on aerial photographs along the major part of Kilauea's east rift 

zone are shown on figure 24. The map also delineates 

all known historic eruptive vents. . In the inaccessible 

and uninhabited region along the rift zone between 

Kaumuki and Napau Crater, the map is no doubt incomplete, and very possibly several recent-looking vents 

and lava flows in this region were produced during the 

1840 eruption. 

The en echelon arrangement of features along the rift 

is shown not only by the 1961 and 1955 fissures, but 
THE 19 61 ERUPTION OF KILAUEA VOLCANO D33 

FIGURE 29.- New south-faciilg fauLt scarp about 20 feet high between the Helhelahulu and Kaumukl tl.ows. Dangling roots and too vines 

'Stretched between the upthrown and dlownthrown blocks Indicate the recent movement. Man In center of the photograph Indicates 

scale. 

also by the overall pattern of all the elements of the 

rift. Moreover, the reversal in the direction of the 

en echelon elements is a major feature of the structure 

of the rift. This reversal occurs roughly near Puu 

Kaliu about 3 miles southeast of Pahoa (fig. 24); both 

to the west and to the east, the vents of the 1955 eruption are successively offset to the north. Hence, the 

vents west of Puu Kaliu are offset to the right and east 

of Puu Kaliu, to the left. However, the 1840 vents 

south of Pahoa are offset to the left and perhaps represent a shift of the region of reversal. The reasons for 

the en echelon arrangement and for the reversal of 

direction are not known. Perhaps the pattern of vents 

in future flank eruptions will shed more light on this 

problem. 

The map of the east rift zone (fig. 24) also shows the 

bipartite division of the rift into two overlapping belts. 

The northern belt, which contains the September 1961 

eruptive vents, is composed of subparallel fissures and 

faults which produce a graben and horst topography. 

The southern belt is marked by cinder cones and some 

pit craters. A preliminary study of the southwestern 

rift zone of Kilauea shows a similar dual structure. 

The fissure-fault belt is on the northwest and the cinder 

cone-pit crater belt is on the southeast. Exactly the 

same pattern is repeated on a much smaller scale in 

the 196.1 eruptive area. The vents of the Heiheiahulu, 

Kaumuki, and Jonika flows from which the small lava 

flows originated generally are on the south side of the 

zone of faulting. 
D34 SHORTER CONTRIBUTIONS TO GENERAL GEOLOGY 

FIGPRE 30.-Same fault scarp shown in figure 28, 2 days later (12•oom, 

September 26), with the men standing at approximately the same 

positions. Vertical displacement has increased to 10.8 feet. 

The significance of this dual structure, both on a 

large and small scale, is not clearly understood, and a 

fuller interpretation must await critical study of seismic 

data recorded during the eruption. One possibility is 

that the rift zone, which represents a major tensional 

feature, is not vertical, but rather dips to the south. 

The northern belt of faults and fissures represents its 

actual intersection with the surface, whereas the southern belt of cinder cone is produced by volcanic conduits 

piercing vertically through the hanging wall of the 

structure. 

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Eaton, J. P., 1959, A portable water-tube tiltmeter: Seismol. Soc. 

America Bull., v. 49, no. 4, p. 301-316. 

Hess, H. H., 1960, Stillwater igneous complex, Montana: Geol. 

Soc. America Mem. 80, 230 p. 

Macdonald, G. A., 1944, The 1840 eruption and crystal differentiation in the Kilauean magma column: Am. Jour. Sci., 

v.242,no.4,p. 177-189. 

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Moore, J. G., and Richter, D. H., 1962, Lava tree molds of 

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Scoon: Am. Jour. Sci., v. 255, no. 4, p. 241-253. 

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May 9-19, 1962, Japan, p. 42-43. 

Richter, D. H., and Eaton, J. P., 1960, The 1959-60 eruption 

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U.S. GOVERNMENT PRINTING OFFICE, 1966 0-207-460