Hawaiian Volcano Observatory

The 1924 explosions of Kilauea

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Sunday, May 18 started out normally on the volcano--at least if you accepted as normal the frequent earthquakes, powerful steam-driven explosions, and severe deformation of the volcano. Observers were on hand just in case something big should happen. Lucky them! That morning the volcano exploded with much more energy than it had for some time. Ten-ton rocks blasted from the crater and thudded to the ground, irritating ash blew far downwind, and the eruption turned, sadly, lethal.

Mount St. Helens? No, though the date and day of the week are the same. But the year was 1924, not 1980, and the place was Kilauea, a volcano falsely, though frequently, accused of having a milquetoast temperament. The largest in a two-week series of steam-driven (phreatic) explosions took place on that fateful Sunday. This is the story of that tumultuous time, almost forgotten today except by those who were there to experience the power of the volcano.

Explosions begin: May 11-12
Things get serious: May 13
More explosions: May 14-15
Popular accounts begin as explosions continue: May 16
Evacuations start on the day before the big one: May 17
The tragedy: Sunday, May 18
Later in the day: May 18
Winding down: May 19-21
Period of photographers and visiting scientists: May 21-26
End of the eruption: May 27-28
Jaggar's absence
What you can see today


The explosive period had an eventful prelude--the draining of a long-lived lava lake in Halemaumau in February followed by a severe earthquake swarm in lower Puna, 50 km down the east rift zone from Halemaumau. The seismic activity began building in early April, reaching its peak on April 23 with ground cracking, faulting, coastal subsidence, and hundreds of felt earthquakes. 

Ruy Finch, the assistant volcanologist and seismologist at HVO (then managed by the Weather Bureau of the Department of Agriculture), spent a great deal of time in lower Puna in April, since he was in charge of the observatory in the absence of Thomas Jaggar. Even the national park superintendent, Thomas Boles, became involved in the crisis. Everyone thought there wrould be an eruption.  

Then the crisis died back with no eruption, to the relief of Finch and the others, and things seemed to stand a chance of getting back to normal. A previous Volcano Watch article traces these unusual events in more detail. The bottom line is that HVO scientists then (and now) believe that the lava draining from Halemaumau in February moved down the rift zone and spread apart the Kapoho area to make room for itself, resulting in earthquakes, ground cracking, faulting, and coastal subsidence.

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Offset at Kula fault in lower Puna, April 23, 1924
April 23, 1924. The Kula fault is actively cutting road just south of village of Koa`e, in lower Puna along Kilauea's east rift zone. Road is downdropped to left. Photo by O.H. Emerson.
Distortion of railroad track in lower Puna, April 23, 1924
April 23, 1924. Kula fault, is opening a gap into which railroad track is dropping and becoming suspended. New ground breakage on left. Photo by K. Maehara (Hilo photographer).
Coastal subsidence at Kapele lagoon, lower Puna
June 19, 1924. Kapele lagoon, with drowned palm trees, formed by subsidence at east end of Kula fault block in April 1924. The trees dropped about 3.5 m. Photo by R.H. Finch.

Halemaumau Crater was 115 m deep following the draining of the lake. The crater was unaffected by the lower Puna crisis, but its floor began to collapse on April 29, as soon as Puna stopped shaking. Large clouds rising from rock falls in the crater mixed with fume to make viewing conditions dreadful. The falling rocks built piles of talus on the sinking floor. The crater deepened to more than 150 m on May 1 and nearly 210 m on May 7. The pace of sinking even increased during the next three days, judging from the huge dust clouds.

On May 9, Oliver Emerson, Research Fellow of the Hawaiian Volcano Research Association, wrote in HVO's journal, "Considerable increase in the rate of subsidence, with continuous rattle of avalanches. During the morning the bottom could be seen, but after noon pit was so full of smoke that nothing could be seen... During the morning considerable aa paste was visible where avalanches tore away large surfaces of the cliff faces. The heat was very noticeable."

Then, in the entry for May 10, Emerson wrote "Volume of dust clouds rising from pit tremendously increased; an impressive sight from Observatory [located at the site of the modern Volcano House Hotel] at 6:30 a.m... Went down to pit [Halemaumau]. Nothing visible because of constant rising of dust. Continuous roar of avalanches. No collapse of walls."

Emerson's notes convey a sense of excitement but no premonition that the events could go ballistic. But ballistic they did--that night.

Regional map
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Glenwood-Kilauea map
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(Left) Map showing most of the place names mentioned in the text. The Kula fault is just south of Koa`e, and Kapele lagoon is at the coast east of Koa`e. Roads and railroads are shown as they were in 1924.

(Right) Detailed map of Kilauea summit area, showing features mentioned in text at their 1924 locations. Also shown are the locations of five large rocks thrown out during the explosions, and the outer limit--very approximate--that rocks of more than 10 cm in diameter were thrown. The Volcano House is now located where HVO was in 1924. HVO is now at Uwekahuna.

Explosions begin: May 11-12

No one saw or apparently heard the first explosion. Just before 0800 on May 11, Fred Watzgen, a national park employee, visited the pit and reported that small rocks were being thrown out of the pit "with the velocity with which a man would thrown stones." He heard no explosions.

Meanwhile, Emerson noted that at "about 9 [the weather] became clear, showing volume of smoke rising from pit increased further...Cloud rose to height of 7,500 feet [2.3 km] more or less above pit, and whole sky to south of pit deep purple, almost black. During morning thunder of avalanches plainly audible on bluff in front of Military Camp."

Finch and a fellow geologist, W.O. Clark, then working for C. Brewer but formerly of the USGS, were drawn to Halemaumau by the previous day's avalanching. At about 11 a.m., they noted that "During night of May 10-11 there was a small explosion that blew out rock fragments, weighing 400 lbs [180 kg] 200 ft [60 m] from rim. One 100 lb [45 kg] fragment found 750 feet [230 m] from rim, and another block weighing 20 lb [9 kg] was found 900 feet [270 m] back. The main deposit of rocks was on N and NE sides, though a few were found all around, with hardly any at WNW. The majority of rocks, judging from their position and bounce mark, came down nearly vertically, though some showed horizontal component."

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Dust cloud from Halemaumau, May 11, 1924
South side of Halemaumau at 1100 on May 11, 1924. W.O. Clark watches dust cloud rising from avalanche in background, making day into night. A few rocks on the ground fell in past 24 hours. Photo by R.H. Finch.
Ruy Finch, seismologist at HVO
Ruy Finch, in charge of HVO during the explosive eruption, examining a crack related to the 1919 eruption that formed Mauna Iki. Photographer unknown.

Next morning's Honolulu Advertiser, quoting Finch, reported "Halemaumau in explosion; hurls rocks 800 feet." The rather laconic report paled alongside a story about Pennsylvania Gov. Gifford Pinchot "assailing" and "attacking" two public figures for speaking out against prohibition.

May 12 was quiet, with no explosions. Emerson and Finch walked around Halemaumau wearing gas masks, and Finch wore goggles--just in case. But the air was relatively clear, and it looked as if the worst was over.

Things get serious: May 13

Several moderate explosions occurred on the morning of May 13. In late morning, the redoubtable Emerson again hiked around Halemaumau, wearing a gas mask on the leeside. He found many rocks that had been newly ejected from the pit as far as 200 yards (200 m). Most of the ejecta were small, but some blocks reached more than 200 pounds (90 kg). He actually heard a number of small explosions or avalanches in the crater but apparently didn't blink.

Explosion column from Halemaumau, May 13, 1924.
Explosion column at 0935 on May 13, 1924. Photo by Oliver Emerson, taken from near Kilauea Military Camp.
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Finch was also on the caldera floor near Halemaumau that morning. Later he saw one explosion from the observatory at 1430 and observed the south rim of the crater to fall in at 1435.

Floor of caldera near southeast rim of Halemaumau at 1100 on May 13, 1924. Comparison with photo taken on May 11 shows more ejecta on the surface. Photo by R.H. Finch, who unfortunately did not identify the people.
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People walking through explosion debris, May 13, 1924.

Finch moved to Uwekahuna (HVO's current location) and saw a frightening explosion at 1600. "Messrs. Boles [park superintendent], Belknap [Hilo Tribune Herald], Cody [Inter-Island Steamship Company] and others were at Halemaumau at the beginning of this explosion."

The front page headline of the May 14 Advertiser picks up the story from there.

More explosions: May 14-15

Finch stayed at Uwekahuna all night, observing conditions in Halemaumau. He felt at least three earthquakes but saw or heard no explosions until 0525 on May 14, when he reported a "small explosion, patter of rocks very perceptible though nearly all appeared to fall back into the pit. Considerable steam rising from N side of pit." Surprisingly, this was the first steam observed during the explosions.

At 0902, Finch reported a "Heavy explosion. Dense cloud for over an hour thereafter. Ascensional rate of dust cloud at 9:25 a.m. 25 ft [7.5 m] per second." He and Emerson then drove to near Halemaumau and investigated rocks thrown out during the large explosion the afternoon before, finding one 140-kg rock that had landed 300 m from the rim and bounced 50 m before stopping. Several more explosions took place as the day wore on.

Each explosion since May 10-11 had ejected ballistic rocks that were largely confined to one sector around Halemaumau. Each explosion was aimed in a slightly different direction, so that, by now, nearly all sectors of the caldera floor were covered by ejecta.

Explosions and earthquakes continued during the night of May 14-15. Shortly after 1100 on the 15th, Finch reported that an explosion "sent great quantities of hot rocks to the SE." The rock falls were heard at Volcano House. Emerson visited the area of fall 10-20 minutes later. "Rocks just thrown out hot and sizzled strongly in rain. While we were at pit, small explosion cloud rose in SW part of pit, following small explosion." The persistent curiosity of Finch and, especially, Emerson in visiting the site of the explosions is noteworthy.

Finch was at Uwekahuna that evening and, from 1815 to after 1835, heard a very loud continuous roar from Halemaumau, "louder than any roar previously heard." Even at HVO, a very loud roar was heard at 2025-2030. A notable explosion took place at 2225, the continuous lour roar ended, and intermittent roar lasted until about 0315 on May 16.

Popular accounts begin as explosions continue: May 16

Explosions, rock avalanches, and earthquakes continued throughout May 16. Emerson was at Uwekahuna and, between 1107 and 1112, reported "series of gas discharges threw rocks, at first a few big ones, then a rattle of small ones sounding like machine gun. Black cloud rose to great height. Earthquake during discharge." Finch and Emerson visited Halemaumau in mid-afternoon and found two cracks across the road about 2000 feet (600 m) from the rim of Halemaumau. Finch was engulfed in a mud rain as he left the pit.

Superintendent Boles reported to the Honolulu Advertiser, in a story published the next morning, that "Kilauea was in eruption at 9 o'clock tonight, red hot lava being sprayed for 1,000 feet [300 m] is all directions. Immense ash clouds were rising four miles [7 km] and cinders were falling. A thunder and lightning storm broke." The report was correct in all respects except about the lava and cinders. All of the ejecta during the entire 1924 explosion series was preexisting rock, not liquid lava. The abundance of red-hot rocks littering the caldera floor was often so great that viewers likened it to a lava flow.

The event reported by Boles was probably no larger than many others that preceded it. The HVO journal makes no special account of it. But now the press was on hand to report and advertise the activity in lay terms, not the sober, understated words of the scientists. For example, Lorrin Thurston, publisher of the Advertiser, described the activity on the evening of May 16 in an article that appeared on May 18:

Despite the exaggeration (no gravel reached anywhere close to the Volcano House), the newspaper accounts brought the explosions to life for the general public. Now the entire territory was aware of Pele's restlessness.

Evacuations start on the day before the big one: May 17

Margaret Finch, Ruy's wife, drew the night watch at HVO on May 16-17, reporting many roars, pisolite (accretionary lapilli) mud rains, and bolts of lightning. The indomitable duo, Ruy Finch and Emerson, walked around Halemaumau the next morning and "saw a relatively flat floor with small irregularities...Rim at SE, E and NE had gone back 200 feet [60 m]." By now Finch estimated that the depth of the pit was more than 1,700 feet (520 m). The cracks across the road had widened, and new cracks concentric to the pit cut the road.

Margaret was back on duty at HVO at noon on May 17 and reported a large explosion, roaring, very heavy black cloud, frequent lightning in the cloud, and the sounds of rocks falling heavily. Emerson, Ruy Finch, Lorrin Thurston, and Ted Dranga (Hilo resident) visited the pit after the large explosion. Near the end of the road at the pit, the area had been covered with hot dust that singed grass, was several feet thick near the rim, and was still warm.

Thurston reported today's events in the same article mentioned above:

The sobering nature of the events comes out in a Mutual Wireless article dated May 17 and published in the Advertiser on May 18:

Ted Dranga and Ruy Finch were the night observers for May 17-18. Each reported several explosions, roars, hisses, thuds, lightning--all the special effects of a horror movie, except that they were as real as can be.

The tragedy: Sunday, May 18

The crisis of May 18 is best told first in the Finches' terse, tense words, then in Thurston's more popular account.

Ruy Finch, in the HVO journal:

Running away from explosion, May 18, 1924
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Two men running away from Halemaumau as the big explosion gets going. The two are not identified. Perhaps the photograph was the very one that Finch wrote he" started to take." The photo is blurred because of camera motion. Can you blame the photographer? Photo used courtesy of Bishop Museum.
8-10-ton block thrown out on May 18, 1924
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Block (R3 on map) weighing 8-10 tons about 1 km southeast of center of Halemaumau (600 m from today's rim), thrown out during explosion of 1115 May 18, 1924, when Finch and others were nearby. The block formed an impact crater in the aviation strip. View looks away from Halemaumau, in direction block was falling. L-R, Oliver Emerson, Tai Sing Loo (in crater holding camera), John Stokes. Photo by H.T. Stearns, 0930 May 22, 1924.
Modern view of the 8-10-ton block
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Same block (R3) as above, taken on May 17, 2001. Note the partial filling of the crater, the changed background as the September 1982 lava flow encroached on the site, and the more abundant small rocks, piled there when the landing strip was cleared after the explosion or during World War II. Oliver has morphed to Christina, Tai to Ruth, and John to Jenda.

Margaret Finch was sitting on the ground near Keanakako`i and observed the following:

Thurston wrote "A review of conditions at the volcano of Kilauea" that appeared in the Advertiser on May 24. Excerpts from it pertaining to May 18 follow:

Explosion of ca. 1115 on May 18, 1924, viewed from top of Uwekahuna Bluff, today's site of HVO. This was the explosion that killed Truman Taylor. Photo by K. Maehara.

Explosion column of 1115 May 18, 1924
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Eruption column of the 1115 explosion of May 18, 1924. Photo taken by K. Maehara from Uwekahuna Bluff and used with permission of Bishop Museum.

Explosion column of 1115 May 18, 1924
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Fortuitously, 24-four-year-old Harold Stearns, later to become one of Hawai`i's preeminent geologists, arrived in Hilo on May 21. He had been sent to Hawai`i from Washington, DC, arriving in Honolulu on May 17, to aid hydrologic studies in the Pahala area by W.O. Clark, one of those who retrieved Taylor. Stearns was anxious to see Kilauea and in his field notes writes that "as soon as the baggage was unloaded [in Hilo] we hit out for Kilauea. My first view of Kilauea was simply a cloud of dust rising with the steam into the low-lying clouds." Things got better quickly.

In Stearns' autobiography, "Memoirs of a geologist: from Poverty Peak to Piggery Gulch" (published by the Hawaii Institute of Geophysics in 1983), he relates the following details about the May 18 tragedy:

24 year old Harold Stearns
Harold Stearns with "my first wild kid," which was eaten for supper. Photo taken on June 19, 1924, likely by W.C. Clark, in Ka`u Desert near Pu`u Kapukapu.
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Stearns later found the rock that had killed Taylor and in his field notes estimated that it weighed about 18 kg. Taylor's boot was there with a severed foot still in it. The rock cannot be recognized today, despite extensive searching, but must be near the northeast end of the parking lot for Halemaumau; it was likely bulldozed during construction of the lot.

Rock that killed Truman Taylor on May 18, 1924
Stearns' camera case rests against the block that killed Truman Taylor during the 1115 explosion on May 18, 1924. On the back of the photo, Stearns wrote "under it I found portions of flesh and burned shoes." Photo by H.T. Stearns, July 27, 1924.
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Miss A. Antoinette Peck, one of the nurses caught in the explosion, wrote a memorial poem to Taylor on May 19 that was published in the Hilo Tribune Herald on May 20, the day of Taylor's funeral.

In Memory of Truman C. Taylor

      A godlike man,
      So young and strong,
      Who surely never
      Did a wrong.
      So why did he
      Brave Pele's wrath
      And walk across
      Her awful path?
      Perhaps she lured him
      As of old
      The sirens did
      So I've been told.
      She doubtless beckoned,
      He obeyed

And in her arms
A moment swayed.
She drew him close
In wild embrace,
Then with one blow
His life effaced.
But blame him not.
In every life
Are tempting moments
When we're rife
With turbulent passions.
Daring souls
Who stake their all
On tragic goals.

I stood beside him
As he prayed
For god's kind mercy.
And he gave
His thanks to all
Who by him stayed.
He never breathed
A mournful sigh,
He did not ask
The reason why
That he was doomed
So soon to die.
He only smiled
And said "goodbye."

Later in the day: May 18

Just after the mid-day explosions, Ruy Finch wrote:

Remarkably, Oliver Emerson went to Halemaumau that afternoon! Here's his journal account:

The two missing privates were the subject of considerable concern and search efforts in dangerous conditions. It was not until May 20 that it was discovered that the two had used the chaos of the time to go AWOL.

Another very large explosion began at about 1914. Ruy Finch observed glowing rocks landing on the lower ledge of Uwekahuna Bluff. (Later, Harold Stearns found a 27-kg block on this lower ledge, 1.5 km from the center of Halemaumau and 60 m above the caldera floor.) Some rocks were thrown 900 m above the pit. Most of the rocks went northward. After dying back, another explosion commenced at about 1922. In Finch's words: "Ground around pit illuminated by hot rocks. Ground at SE very heavily bombarded. Large rock to E about 4000 ft [1.2 km]...One rock toward Military Camp about 5,000 [1.5 km] from rim."

Meanwhile, people were leaving the Volcano House for safer ground. As Thurston reported in his summary published on May 24:

Margaret and Ruy Finch maintained vigilance through the night, noting numerous explosions or avalanches, earthquakes, thunder and lightning, and a nearly constant roar.

Winding down: May 19-21

Halemaumau was characterized by the Advertiser, in a story dated May 19, as being in "a sulky mood" following the "several violent upheavals" on Sunday, May 18. The article went on to say that:

The same Advertiser article stated that:

The former owner of Hirano Store in Glenwood, whose father owned the store in 1924, recently told us that the eaves of the store collapsed because of wet ash. Glenwood is about 16 km up the trade winds from Halemaumau.

Observers were on heightened alert during this time, but the explosive activity was slowly winding down. A number of small explosions, and several of moderate size, took place, but nothing to rival the two on May 18.

Period of photographers and visiting scientists: May 21-26

One thing notably lacking so far was good photographic coverage. K. Maehara from Hilo had taken many excellent images but apparently was not around all the time to document fully the chain of events. This was to change with the arrival of Harold Stearns in Hilo on the morning of May 21 and the return of Tai Sing Loo on perhaps the same day. Stearns was a geologist, not a professional photographer, but he nonetheless took several images of lasting value. Loo, official photographer of the naval station at Pearl Harbor, was a professional and took most of the photographs now seen publicly.

It is a pity that neither arrived sooner. Stearns was in Honolulu on his way from the mainland to Hilo, but prior engagements apparently kept him from sailing earlier. We don't know why Loo did not come earlier.

Stearns' first two photos, taken on May 21, show us what conditions looked like between explosions and during a rock avalanche.

Skip past Halemaumau explosions
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Conditions at Halemaumau between explosions, May 21, 1924
"Normal" conditions at Halemaumau between explosions. View from road 1.5 km southeast of crater. Photo by H.T. Stearns at 1415, May 21, 1924.
Dust cloud from rock fall in Halemaumau, May 21, 1924.
Cloud of red dust raised by rock fall into Halemaumau 1.5 minutes later. Photo by H.T. Stearns at 1416:30, May 21, 1924. 

He and Loo then took a series of photographs showing the rise of an explosion column starting at about 0810 on May 22. The first image is credited to Loo in Stearns' photo album. There is some question about whether Loo or Stearns should be credited with the others. Loo definitely took the last annotated image.

One-half minute after start of explosion, May 22, 1924
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0810:30. One-half minute after start of explosion from Halemaumau on May 22, 1924. Photo by Tai Sing Loo from Hawaiian Volcano Observatory, 3.5 km northeast of crater. All subsequent photos are taken from about the same place. 
1 minute after start of explosion, May 22, 1924
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0811. Column is now 975 m wide at base, 1,000 m high, and rising at a rate of about 17 meters per second. The dimensions and rise rate in this and subsequent photos were calculated by Stearns, scaled to the known width of Halemaumau. Note dust kicked up by rocks showering down on caldera floor.  
2 minutes after start of explosion, May 22, 1924
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0812. Eruption column is now 1,650 m high and rising at rate of about 11 m per second. Rocks continue to pound the caldera floor.
4 minutes after start of explosion, May 22, 1924
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0814. Column has reached a height of 2,450 m, and its rate of rise has slowed to about 5 m per second.
6 minutes after start of explosion, May 22, 1924
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0816. The column is now 3 km high and still rising about 5 m per second.
8 minutes after start of explosion, May 22, 1924
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0818.  Stearns calculated that the column is now 3.5 km high and rising about 4 m per second. In foreground are John Stokes (Bishop Museum) on left and Harold Palmer (University of Hawai`i) on right.
10 minutes after start of explosion, May 22, 1924
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0820. The cloud is now over 3.7 km high. Stearns observed three lightning bolts in the column at about this time.
20 minutes after start of explosion, May 22, 1924
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0830. Column rising from Halemaumau near end of the explosion. Taken from outside Volcano House by Tai Sing Loo.

Loo apparently used a wide-angle lens to capture the mushroom shape of an explosion column and downwind cloud at 1500 on May 23. The photo, taken from near the Volcano House or HVO, shows ash being blown southwestward by trade winds.

Mushroom-shaped eruption column from Halemaumau. Photo by Tai Sing Loo at 1500 on May 23, 1924 from near Volcano house or HVO.
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Mushroom-shaped explosion column, May 23, 1924

Loo took another stunning photo of an eruption column on May 24, probably also from near the Volcano House. The photo was supposedly taken at 0913. This seems unlikely, however, for another sequence of photos, labeled on the negatives and so probably taken by a professional photographer, begins at 0913 and looks quite different from Loo's shot. That sequence shows the development of a moderate column in about 5 minutes.

Explosion column on May 24, 1924.
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Photo of eruption column coming out of Halemaumau on May 24, 1924 by Tai Sing Loo, from Volcano House or HVO.
Explosion column from Halemaumau, 0913 May 24, 1924
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0913, May 24, 1924. Explosion from Halemaumau, seen from HVO or Volcano House. This and subsequent four photos were apparently taken from the same place by the same photographer. Each photo is labeled with "11TH PHOTO SEC. A-" followed by photo number, KILAUEA VOLCANO, time, and date. One photo, not reproduced here, shows a man in possible military uniform. The photos could have been taken by someone from the nearby military camp.
30 seconds later: explosion column from Halemaumau, 0913 May 24, 1924
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0913:30, only 30 seconds after the previous photo. Note the growth of the column on right, indicating a separate explosion. A small surge may be moving left from the crater.
1 minute later: explosion column from Halemaumau, 0913 May 24, 1924
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0914. Now the younger explosion column has almost completely merged with the first.
3 minutes later: explosion column from Halemaumau, 0913 May 24, 1924
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0916. One column rises above Halemaumau. Note dust from falling rocks, best seen in large image.
5 minutes later: explosion column from Halemaumau, 0913 May 24, 1924
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0918. Final shot in the sequence.

The activity at Halemaumau may have been wearing down, but tensions were still high. The May 24 explosion caught the attention of all, and the Advertiser's front-page story dated that day reported:

It seems that human nature can be depended upon.

Other earth scientists were appearing on the scene--another sign of the constancy of human nature. In those days, of course, there were no airplanes carrying passengers to Hawai`i from the mainland, so most of the visitors were already in Hawai`i at the time the explosions began. (In the 21st century, the group would be international.)

On May 22, a group of nine walked to the aviation field: W.O. Clark (C. Brewer, formerly of USGS); Oliver Emerson (HVO); Prof. Herbert E. Gregory (Yale University and director of the Bishop Museum); Prof. Paul Kirkpatrick (Univ. Hawai`i); Tai Sing Loo (Pearl Harbor); Prof. Harold Palmer (Univ. Hawai`i); Harold Stearns (USGS); and John Stokes (Bishop Museum). The geologists examined the deposits from the explosions and, arriving within 30 minutes after one explosion, posed in jaunty fashion for Tai Sing Loo. 

The scientists found that the aviation field was strewn with scattered blocks, and they examined a rock thought to have been hurled out only 1 hour earlier.

Scientists along road with Halwmaumau in background, May 22, 1924
Dust cloud in Halemaumau forms backdrop for group photo 30 minutes after explosion on May 22, 1924. Note rocks and impact pits. Group stands on road, with front of automobile just visible in lower left. L-R, Stokes, Stearns, Emerson, Palmer, Clark, Gregory, Kirkpatrick. Photo by Tai Sing Loo.
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Geologists on aviation field strewn with scattered blocks, May 22, 1924
Block-littered aviation field on what is now known as Sand Spit. The field was built on ash and blocks erupted in 1790 and earlier. Blocks were cleared to make a landing strip, which was used by tour planes taking visitors to the volcano in the early 1920s. Then the 1924 explosions peppered the strip with rocks (some shown here), which had to be removed after the turmoil had subsided. Later, during World War II, the strip was bulldozed to keep enemy planes from landing, only to be reopened after the war ended. The strip was available for emergency landings until recently, when rocks have reappeared as wind has winnowed out the finer ash. Photo by H.T. Stearns on May 22, 1924. L-R, Gregory, Kirkpatrick, Clark.
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Geologists examine rock tossed out about 1 hour earlier, May 22, 1924

Group examining rock, broken into two pieces by impact, and resulting crater formed 1 hour earlier, about 1.5 km from center of Halemaumau on the aviation field. L-R, Kirkpatrick, Palmer, Gregory, Stokes. Photo by H.T. Stearns, 0900, May 22, 1924.
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Stearns was interested in how much ash was falling in distant areas downwind of Halemaumau. On May 25, he was in Wood Valley, 30 km from the pit, and encountered a dense cloud of dust generated by an explosion about 30 minutes earlier. Sharp sand, 1 mm in diameter, showered down, stinging hands and faces. It fell so rapidly that it slid down wrinkles in clothing in continuous streams. A building 45 m away could not be seen.

W.O. Clark swept up and weighed ash in a 50 square meter area in Pahala (30 km from Halemaumau) and found that 400 pounds per acre (449 kg per hectare) fell every 24 hours. Stearns estimated that the total fall in the Pahala area during the explosions must have been 2-3 tons per acre (4.9-7.4 tons per hectare).

W.C. Clark with ash on sidewalk in Pahala, May 22, 1924
Accumulation of ash on sidewalk in past 24 hours at Pahala, 30 km down the trade-wind direction from Halemaumau. W.O. Clark in photo, taken by H.T. Stearns at 0700 on May 22, 1924.
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Nearer Halemaumau, the tephra (ash and coarser debris) were much thicker, probably at least as much as 60 cm. And it coated everything, giving a strangely gray, subdued appearance to the irregular surfaces of lava flows in the caldera.

Ash and cracks at east rim of Halemaumau, June 1, 1924
Thomas Jaggar standing amid ash and blocks of the May 1924 eruption, looking east-northeast toward Kilauea Iki. Note the fresh cracks that opened as Halemaumau was widening during its collapse accompanying the explosions. Photo by Tai Sing Loo on June 1, 1924.
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Ash and blocks 600 m southeast of Halemaumau
Ash and blocks about 600 m southeast of Halemaumau, in distance. Holes in foreground formed with falling rocks broke through the surface of a pahoehoe flow. Pile of rocks in upper center marks terminus of road, near where Truman Taylor was killed. Photo by K. Maehara, date unknown.
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A story in the Advertiser on May 22 commented that "Vegetation at the hotel is reviving, due to rain which has washed away the thick coating of dust. The [dirt] roads in the national park are now semi-paved, as the rain, falling on the volcanic dust, forms a sort of cement."

End of the eruption: May 27-28

Finally the series of explosions wore down, the last two, very weak, taking place in the morning of May 27. As the activity declined, there was renewed interest in whether any lava might be returning to Halemaumau or whether glowing spots could be seen within it. The air had cleared a little in the pit, and so before dawn on May 27 Ruy Finch, an observer named Vern Hinkley, and--as Finch was careful to note--Jaggar's collie, Teddy, drove as far as the boulders on the road would permit and peered into the pit at 0405. No glow. They were probably surprised and a little disappointed, but their notes reflect no emotion.

They found that the crack across the road, which had first opened on the 16th, had widened since the last dust deposit. Steam from the crack was close to the boiling point. This is probably the same crack that steams today at the southeast corner of the parking lot. A preliminary survey on May 27 showed that Halemaumau was now 1,035 m long and 915 m wide.

On May 28, Oliver Emerson and Chester Wentworth (Bishop Museum) made a circuit of the pit. The southern part of the caldera floor was covered with much mud, small gravel, and a few boulders, increasing in number and size northward on both sides of the pit. On the northern side, the ground was covered with small stones, weighing from 2 to 11 kg, with scattered large boulders. The hummocky pahoehoe below the explosion deposit gave the appearance of thick heaps of debris, but the deposit really formed a layer only 30-36 cm thick.

Chester Wentworth, later to become a well known sedimentary geologist but at the time working at the Bishop Museum after being fired from Washington University "because of his unsocial behavior with women" (quote from Stearn's autobiography). Photo taken in 1923.
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C.K. Wentworth in 1923.

The final topographic map of Halemaumau, constructed on July 10, showed that the crater was about 1,065 m long (northeast-southwest), 915 m wide (northwest-southeast), and about 417 m deep. The floor was coated with explosion debris, so the actual depth of the crater was considerably more. The crater deepened more than 295 m during the explosions and their immediate precursors, and it about doubled in width and length. The volume of ejecta was less than 0.5 percent of the volume lost by the collapse of the pit. Jaggar estimated that the rock walls lost about 202 million cubic meters and that only 793 thousand cubic meters of rock were blasted out. Where the extra material went is a continuing source of debate--submarine lava flow, intrusion into the summit or east rift zone, filling of voids.

Detailed surveys showed unprecedented ground deformation throughout Kilauea's summit. Leveling surveys showed that the caldera floor east of Halemaumau dropped nearly 4 m, HVO and Volcano House went down 1 m, and benchmarks as far as 7 km from the summit subsided almost 1 m. The ground around the summit moved inward 1-1.5 m. The details are fuzzy owing to the instrumental deficiencies of the time, but the displacements are nonetheless huge and easily recognizable.

Jaggar's absence

Conspicuously missing from the scientific group was the founder and head of HVO, Thomas Jaggar. He was in New York giving a series of lectures and writing articles. He returned to Kilauea as soon as he could but did not arrive until May 28, the day after the explosions had ended. He was not pleased with the way the observations by his staff had been handled, though it seems difficult now for them to have been improved significantly. In an unpublished letter written in 1947 to Superintendent Frank Oberhansley of Hawaii National Park, Jaggar stated that "...1924 was my responsibility, and my absence was a pity, the most fatal disappointment of my life."

A measure of how highly Jaggar was respected is a boxed front-page article in the May 26 Advertiser:

In the end, Jaggar took his first flight ever, by navy seaplane from Pearl Harbor. Engine problems forced the plane down twice off the Moloka`i reef in rough weather. The second landing was considered forced even by the aviators, but to Jaggar, "the word landing seemed to me inapplicable." The plane drifted for 5 hours before being met by a boat and towed to Kaunakakai. From there, Jaggar was taken by a navy tug overnight to Hilo, arriving seasick at 1400 on May 28. As he put it, "instead of five hours, the journey took thirty and quite failed to make me air-minded."

What you can see today

Ash deposits are notoriously fleeting, and such is the case for much of the 1924 ash. The deposits cannot be recognized in most places more than 1 km from Halemaumau, and even within that distance they are poorly preserved. The trail to the Halemaumau viewing platform crosses thin beds of ash, hardened by acid fume and millions of footsteps. Fairly thick deposits are preserved between the trail and the crater rim.

Bedded 1924 ash in trail to Halemaumau overlook, May 2001
Bedded ash in the trail to the Halemaumau overlook, as seen in May 2001.
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Even casual observation will note thousands of loose rocks lying on the pahoehoe. They have been badly disturbed near the parking lot, the trail, and in many other places where the rocks have been used to line trails, build shelters, and the like. But the overall impression is obvious--rocks everywhere.

Ejecta blocks from 1924 explosions near Halemaumau, May 2001
Blocks ejected in 1924, about 150 m from present southeast rim of Halemaumau. This scene is typical of areas near the crater that have not been disturbed by human activities. All of the rocks were blown out in 1924.
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What is most impressive, however, is the size of the largest blocks that were hurled from the crater onto the caldera floor. The largest was estimated at 14 tons; it was just barely able to get over the northeast rim of the crater. Though it was an attraction for some time, it eventually fell into the crater and disappeared.

Skip past 14 ton rock
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14 ton rock with Boles and Farrington
This 14-ton block (R1 on map) was thrown out while red-hot during one of the explosions in May 1924. Park superintendent Thomas Boles is on left and Territorial Governor W.R. Farrington. Photograph, National Park Service, date sometime before 1929.
14 ton block with sign
The 14-ton block (R1) was an attraction to visitors and was awarded a sign announcing "14 TONS. THROWN OUT DURING ERUPTION MAY 1924." It perched near the northeast rim of Halemaumau for some time before falling into the crater. Photo by Prof. H. Ries in 1930.

Another 14-tonner (R2 on map), 2.4 by 1.8 by 1.5 m across, was thrown 120 m west-southwest from Halemaumau at some time late in the series of explosions. It was first seen on May 28, when Emerson and Wentworth found evidence that it had landed about 75 m nearer the pit and had rolled to its resting place. Judging from its descriptions, this block was rather isolated from other large ones. As the crater widened during the explosions, the rock came ever nearer falling in, and it eventually did, apparently without ever becoming a visitor attraction.

Other blocks can be found today. The large one (R3), weighing 8-10 tons, that impacted the aviation field on May 18, during the explosion that killed Taylor, is easily recognizable. It was a signed visitor attraction for some time. The impact pit the block made is slowly filling in, however, and the area around the block was disturbed by bulldozing during World War II when the air strip was made unusable by enemy aircraft. A lava flow erupted in September 1982 threatened the block but came up a bit short.

Skip past 10-ten block,1930 airfield
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8-10-ton block on aviation field, May 22, 1924
Block (R3) weighing 8-10 tons about 1 km southeast of center of Halemaumau (600 m from today's rim), thrown out during explosion of 1115 May 18, 1924, when Finch and others were nearby. The block formed an impact crater in the aviation strip. View looks away from Halemaumau, in direction block was falling. L-R, Oliver Emerson, Tai Sing Loo (in crater holding camera), John Stokes. Photo by H.T. Stearns, 0930 May 22, 1924

8-10-ton block on aviation field; photo in 1930
The 8-10-ton block was a visitor attraction, particularly to those using the aviation field during the late 1920s and 1930s. This photo was taken in 1930 by either Prof. H. Ries or Prof. A.S. Eakle. The park sign says "8 TONS. HURLED OVER ONE MILE HIGH DURING ERUPTION MAY 1924."

8-10-ton block in 2001
Same block as that to left, taken on May 17, 2001. Note the partial filling of the crater, the changed background as the September 1982 lava flow encroached on the site, and the more abundant small rocks, piled there when the landing strip was cleared after the explosion or during World War II.

Three other huge blocks can be found today that were ejected in 1924 but at unknown times. One (R4 on map) is alongside Crater Rim Drive 300 m southeast of the Halemaumau parking lot. This block is the site of frequent offerings to Pele left by today's worshipers. It is shown in a photograph taken by Carl Carlsmith on May 18, just before the biggest explosion. The photo was published by the Advertiser in its May 26 edition.

Another (R5) is just north of the west end of the old air strip. Both of these two blocks weigh 8-10 tons apiece. Each is imbedded into older ejecta thrown out in explosions in 1790 and earlier. Probably each made a crater, which later has been filled in by construction and natural processes.

Skip past 8-10-ton block

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8-10-ton block near Crater Rim Drive in 2001
Ejecta block (R4), weighing 8-10 tons, along Crater Rim Drive 300 m southeast of Halemaumau parking lot. This rock was thrown out sometime before May 18, 1924.

8-10-ton block at northwest end of landing strip, 2001
Large block (R5), 8-10 tons, near northwest end of old landing strip on Sand Spit, 220 m due south of the Halemaumau parking lot. Black day pack gives scale.

Yet another very large block (not shown on the map or in a photo) lies only 70 m east of the Halemaumau parking lot. This monster is 2.7 m by 2.3 m by 1.7 m and weighs 10-13 tons. All of the exceptionally large blocks are rather isolated from other large ones. That was noted at the time and remains a curiosity today.

All three huge blocks were noted on a sketch map by Jaggar (made on June 7) as having been thrown out in 1924, so they are not blocks from the 1790 eruption.

Impact pits were often made when blocks hit the ground. Some of the pits still survive, including many small ones at the west end of the Sand Spit directly south of Halemaumau. Here pre-existing ash served as a good medium in which to form and preserve impact pits. Where old tephra is absent, rocks crashed through the upper crust of pahoehoe flows. Good examples of such pits can be seen south of the Halemaumau parking lot or along the trail beyond the viewing platform.

Impact pit made in mushy ash in 1924
Impact pit made by block falling almost straight down into muddy ash, squishing up the mud evenly around the depression. Some nearby pits formed by rocks falling obliquely, so that the rim is larger on the side of the pit away from Halemaumau. Photo taken on April 1, 2001 near west end of Sand Spit. Black day pack gives scale.
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Broken pahoehoe crust with ejected block inside
Example of impact pit made as falling rock broke through the surface crust of the 1919 pahoehoe flow, just south of Halemaumau parking lot. The culprit rock still nestles in the pit. Parking lot and Crater Rim Drive in background. Photo taken April 1, 2001. Black day pack gives scale.
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By using contemporary writings and photographs, this presentation has tried to illustrate some of the impacts that an explosive eruption of Kilauea can have on the neighboring area, both physically and psychologically. And, the 1924 explosions were small by geologic standards and by the standards of some past Kilauea explosions. The hazards of larger explosions, such as those that took place multiple times between about A.D. 1500 and 1790 and, in even larger fashion, between about A.D. 600 and 1000, are far worse than those associated with the 1924 series.

An obvious but often overlooked factor is that the risk has risen greatly over time as more people crowd nearer to Kilauea's caldera and as the infrastructure becomes ever more involved and expensive. The 1924 series of explosions would today raise havoc to many national park, KMC, and USGS facilities because of the dusty air, mud rains, and severe lightning storms. Nearby residents of the Golf Course, Volcano, and neighboring developments would have fouled water-catchment systems at the very least. The mud rain that fell on the railroad near Maku`u shows that the problem of dirty drinking water could extend for tens of kilometers away.

The 1924 explosions were probably just on the verge of being large enough to generate hot pyroclastic surges--among the most devastating of all volcanic phenomena. The 1790 explosion that killed so many people probably was lethal mainly because of its surges.

Kilauea is an explosive volcano. That is a fact that is all too often overlooked. Long-range planning should take this fact into account. With proper warning, and with proper heeding of that warning, no one should be killed. But there will certainly be severe impacts to buildings, communication, transportation, and the overall infrastructure when the next large explosions take place. That is an unavoidable consequence of living, working, and playing on one of the most active volcanoes on Earth.


Photographs used in this presentation are taken from the HVO archive, the Harold T. Stearns collection at the University of Hawai`i at Hilo, a collection at the USGS office in Honolulu, American Journal of Science, and the Monthly Bulletin of the Hawaiian Volcano Observatory. Two photos are used with the permission of the Bishop Museum. Prints were used for scanning whenever possible, but no prints for the photos in the HVO Monthly Bulletin and American Journal of Science could be found, so that the half-tones from the published papers had to be used. No large-scale images were made of the poor-quality half-tones.

Text is quoted from the HVO journal chronology kept at the time of the eruptions and published by Jaggar (Origin and Development of Craters, Geological Society of America Memoir 21), unpublished field notes of Stearns (held at the USGS office in Honolulu), the Honolulu Advertiser, the Hilo Tribune Herald, and Stearns' autobiography ("Memoirs of a geologist: from Poverty Peak to Piggery Gulch," published by the Hawai`i Institute of Geophysics, Honolulu). The unpublished letter from Jaggar to Oberhansley is in the HVO files. Jaggar's trip from Pearl Harbor to Hilo is described in his book, "My experiments with volcanoes," published by the Hawaiian Volcano Research Association.

Particular thanks to Twyla Thomas (USGS, Honolulu) for her efforts in finding Stearns' original field notes and photos, Patricia Okamura (Univ. Hawai`i Hilo) for making available the photographs in the Harold T. Stearns collection, Jane Takahashi for maneuvering through the HVO collections, and Kent Warshauer for his careful collection of articles from the Honolulu Advertiser. skip past bottom navigational bar

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Updated: 23 July, 2001 (pnf)