Halemaumau | Images of Old Hawaiʻi

April 8, 2025 by Peter T Young Leave a Comment

Six Active Volcanoes in Hawai‘i

The Hawaiian Islands are at the southeast end of a chain of volcanoes that began to form more than 70 million years ago. Each island is made of one or more volcanoes, which first erupted on the floor of the Pacific Ocean and emerged above sea level only after countless eruptions.

Hawaiʻi sits over a ‘hot spot,’ the Hawaiian hot spot.

It’s one hot spot, but lots of volcanoes have formed over it. The Islands are above a moving sea floor of the North Pacific Ocean (the Pacific Ocean is mostly floored by a single tectonic plate known as the “Pacific Plate.”)

The Pacific Plate is moving over the layer in the Earth known as the Asthenosphere. This movement takes it to the northwest. As the plate moves over a fixed spot deeper in the Earth where magma (molten lava) forms, a new volcano can punch through this plate and create an island.

As the plate moves away, the volcano stops erupting and a new one is formed in its place. With time, the volcanoes keep drifting westward and getting older relative to the one active volcano that is over the hot spot.

As they age, the crust that they sit on cools and subsides. This, combined with erosion of the islands, once active volcanism stops, leads to a shrinking of the islands with age and their eventual submergence below the ocean surface.

Each island is made up of at least one primary volcano, although many islands are composites of more than one. The Big Island, for instance, is constructed of 5 major volcanoes: Kilauea, Mauna Loa, Mauna Kea, Hualālai and Kohala (the island is still growing, but is basically about 400,000-years old.)

About 40-million years ago, the Pacific Plate changed direction from north to northwest – so the Emperor Seamounts run more north-south, the Hawaiian Ridge north-westerly.

Midway Island is 27.7-million years old; Meiji Seamount the northern part of the Emperor Seamount (near the end of the Aleutian chain) is about 80-million years old.

All of these are still youngsters, when you look at the perspective, say, of the dinosaurs. The Islands weren’t even a glimmer in anyone’s eyes when dinosaurs walked the Earth; sixty-five million years ago the last of the non-avian dinosaurs went extinct, after living on Earth for about 165-million years. (USGS)

If all of Earth time from the very beginning of the dinosaurs to today were compressed into 365 days (1 calendar year), the dinosaurs appeared January 1 and became extinct the third week of September.

Using this same time scale, the Earth would have formed approximately 18.5-years earlier. By comparison, people have been on earth only since December 31 (New Year’s eve.) (USGS)

While we typically think of and/or hear news reports of eruptions on Kilauea and Maunaloa, presently, the US Geological Survey (USGS) Hawaiian Volcano Observatory (HVO) monitors the six currently active volcanoes in Hawai‘i.

The Island of Hawai‘i, with four active volcanoes, is liveliest. Between 1912 and 2012, there were nearly 50 Kīlauea eruptions, 12 Mauna Loa eruptions, and one Hualālai intrusion of magma.

Kīlauea, the youngest and most active volcano on the Island of Hawai‘i, erupted almost continuously from 1983 to 2018 at Pu‘u‘ō‘ō and other vents along the volcano’s East Rift Zone. Since then, there have been periodic eruptions in and nearby Halema‘uma‘u crater at the volcano’s summit.

In 2018, Kīlauea experienced the largest lower East Rift Zone eruption and summit collapse in at least 200 years. Several summit eruptions since December 2020 have generated lava lakes that have been slowly filling in the collapsed area, including Halema‘uma‘u crater. About 90 percent of the volcano is covered with lava flows less than 1,100 years in age.

Mauna Loa, the largest volcano on Earth, has erupted 34 times since 1843. An eruption 1984 lasted 22 days and produced lava flows which reached to within about 4.5 miles of Hilo, the largest population center on the Island of Hawai‘i.

The most recent eruption in 2022 lasted two weeks and erupted lava flows that came to within 1.7 miles of the Daniel K Inouye Highway (Saddle Road). Lava flows less than 4,000 years old cover about 90 percent of the volcano.

Hualālai, the third most active volcano on the Island of Hawai‘i, has erupted three times in the past 1,000 years and eight times in the past 1,500 years.

The most recent eruption in 1801 generated a lava flow that reached the ocean and now underlies the Kona International Airport. Lava flows less than 5,000 years old cover about 80 percent of the volcano.

Mauna Kea, the highest volcano on the Island of Hawai‘i, erupted most recently between about 6,000 and 4,500 years ago from at least seven separate summit-area vents, producing lava flows and cinder cones. Glaciers covered parts of the volcano’s summit area during the recent ice ages, the only Hawaiian volcano known to have been glaciated.

Kama‘ehuakanaloa (formerly Lō‘ihi Seamount), the only known active Hawaiian submarine volcano, erupted most recently in 1996 during an earthquake swarm of more than 4,000 events that were recorded by the HVO seismic network. The volcano’s summit is about 3,179 ft below sea level, located 22 miles southeast of the Island of Hawai‘i.

Haleakalā, the only active volcano on the Island of Maui, erupted most recently between about 600 and 400 years ago. In the past 1,000 years, at least 10 eruptions produced lava flows and tephra cones from the rift zone that crosses the volcano from southwest to east and through Haleakalā Crater. (All here is from the US Geological Survey (USGS.))

May 17, 2023 by Peter T Young Leave a Comment

Truman Taylor

Explosive eruptions do not generally come to mind when people think of Hawai‘i’s volcanoes. Their eruptions are typically characterized by the relatively quiet outflow of very fluid lava and by sometimes spectacular lava fountains.

Hawai‘i’s volcanoes have therefore become the textbook example of nonexplosive volcanism, and the term “Hawaiian type” is used to refer to such eruptions. Eruptions at Kilauea can often be observed safely at close range. (USGS)

The late 1780s were years of great strife on the Island of Hawai’i. Kamehameha, who later became the first king of the Hawaiian Islands, was at war with his rival Keōua. After one of several indecisive battles, probably in 1790, the balance was suddenly tipped in favor of Kamehameha when a natural disaster struck.

As a large group of Keōua’s warriors traveling with their families passed the crater of Kilauea Volcano, there was a sudden explosive eruption of searingly hot ash and gas. At least 80 and perhaps hundreds of people were killed in the deadliest historical eruption to occur in what is now the United States. (USGS)

During 18 days in May 1924, hundreds of steam explosions from Kilauea hurled mud, debris, and hot rocks weighing as much as 8 tons as far as two-thirds of a mile from the center of Halema‘uma‘u the current crater within the larger volcanic depression (caldera) at Kilauea’s summit.

Columns of volcanic ash and dust rose more than 2 miles into the air, at times turning day into night at the town of Pahala, nearly 20 miles downwind.

Only one person was killed during this eruption, a photographer who ventured too close and was struck by falling rocks and hot mud. (USGS)

The largest explosive event in 1924, on May 18, ejected blocks toward the southeast, including the eight-ton block, and killed Truman Taylor. (Pacific Parks)

Taylor Stearns notes in his autobiography, “[WO] Clark told me how he had brought Taylor, a clerk about twenty-seven years old from Pahala [he worked on the C. Brewer plantation], up to the volcano. Miss Bradfield, the local nurse, and her companion [Miss Peck] had been with them.”

“Taylor had borrowed Clark’s camera and tripod to take a close-up shot. [When the explosion began, Ted] Dranga and the two nurses ran to the Essex car nearby, which they had left running so as to make escape easy [those were the days of hand cranks].”

“When they reached the car the [others] wanted to start right away but Miss Bradfield said she didn’t want to leave with Taylor out there. She made them wait a minute, and then as the stones began to fall around them she decided it would be better to leave Taylor than for all to be killed.”

Per, “Ruy Finch, in the HVO journal: 10:36 a.m. With L.A. Thurston and W.O. Clark of Pahala. Large puffs of steam; rumbling, earthquake. Went to sand spit above Algae [an area of algae growing on the south-facing cliff, then known as the Italian cliff, that forms the south side of what is now known as Sand Spit] and sat down on a boulder which had been ejected at 12:30 p.m.”

“May 17. Numerous quakes and rumbling. Sent T. Dranga Jr., to get Thurston who was with Carlsmiths. A wave of increased air pressure that decidedly hurt my head, was felt at 11:09 a.m. Jumped and exclaimed, ‘Here comes a terrible one.’”

“The air pressure was felt several seconds before rocks appeared and two or three seconds before the explosion cloud cleared the rim. Started to take picture but saw rocks of great dimensions high in the air headed toward our locality.”

“Ran to cliff and slid down a wash. A rock, judging from its air appearance to have weighed over 300 lbs [135 kg] cleared the cliff and landed on 1921 lava. Left Thurston, Clark and ladies of Carlsmith party on cliff.”

“O Emerson in the afternoon reported a 10-ton rock on airplane landing-field [on Sand Spit], found while searching for possible killed or wounded soldiers. Two men were seen on rim of pit a short time before 11:09 a.m. explosion.”

“TA Dranga Sr. came across crater floor but said that Mr. Truman Taylor of Pahala, who was with him on the way up to crater, had left him 10 minutes before the explosion”

“Went back to find missing man with Clark, Dranga Jr. and Dranga Sr. Taylor was discovered with legs crushed by fallen bowlders about 125 feet from old parking place.”

“Dranga Sr. started to get car seat, to use as stretcher, when another explosion came. Dranga Jr. and I carried Taylor to road where he was put into car.” (USGS)

“Truman A Taylor, bookkeeper at Pahala, died at 11:30 o’clock last night [May 18, 1924] at Hilo Hospital from hemorrhage and shock. One leg had been amputated at the ankle after it had been crushed by a shower of rocks from the volcano.”

“Taylor was found shortly before noon yesterday by an unidentified man who heard screams. He was covered by burning ash, and both legs were crushed.”

“First aid was given by Capt PK McKenzie, surgeon at Kilauea Military Camp and the injured man was rushed in Army ambulance, accompanied by Miss Molly Thomas, Hilo nurse, to Hilo Hospital.”

“Taylor was from Chicago, and had been in Pahala about two months, after a stay of three weeks in Honolulu. He wore a tag bearing the legend, ‘USA 3422044.’” (SB, May 19, 1924)

April 11, 2023 by Peter T Young Leave a Comment

Whose Footprints Are These?

Geologic evidence suggests that the modern caldera of Kīlauea formed shortly before 1500 AD. Repeated small collapses may have affected parts of the caldera floor, possibly as late as 1790. For over 300-400 years, the caldera was below the water table.

Kilauea can be an explosive volcano; several phreatic eruptions have occurred in the past 1,200 years. (Phreatic eruptions, also called phreatic explosions, occur when magma heats ground or surface water.)

The extreme temperature of the magma (from 932 to 2,138 °F) causes near-instantaneous evaporation to steam, resulting in an explosion of steam, water, ash and rock – the 1980 eruption of Mount St. Helens was a phreatic eruption.

The 1924 eruption at Halemaʻumaʻu documents and illustrates the explosive nature of Kilauea. However, 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 AD 1500 and 1790, are far worse than those associated with the 1924 series. (USGS)

There were explosions in 1790, the most lethal known eruption of any volcano in the present United States. The 1790 explosions, however, simply culminated (or at least occurred near the end of) a 300-year period of frequent explosions, some quite powerful. (USGS)

Keonehelelei is the name given by Hawaiians to the explosive eruption of Kilauea in 1790. It is probably so named “the falling sands” because the eruption involved an explosion of hot gas, ash and sand that rained down across the Kaʻu Desert. The character of the eruption was likely distinct enough to warrant a special name. (Moniz-Nakamura)

At the time, Kaʻū Chief Keōuakūʻahuʻula (Keōua) was the only remaining rival of Kamehameha the Great for control of the Island of Hawaiʻi; Keōua ruled half of Hāmākua and all of Puna and Kaʻū Districts. They were passing through the Kilauea area at the time of the eruption. The 1790 explosion led to the death of one-third of the warrior party of Keōua. (Moniz-Nakamura)

Camped in Hilo, Keōua learned of an invasion of his home district of Kaʻū by warriors of Kamehameha. To reach Kaʻū from Hilo, Keōua had a choice of two routes one was the usually traveled coastal route, at sea level, but it was longer, hot, shadeless and without potable water for long distances. (NPS)

The other route was shorter, but passed over the summit and through the lee of Kilauea volcano, an area sacred to, and the home of, the Hawaiian volcano goddess Pele. Keōua chose the volcano route, perhaps because it was shorter and quicker, with water available frequently. (NPS)

In 1919, Ruy Finch, a geologist at the Hawaiian Volcano Observatory discovered human footprints fossilized in the Kaʻū desert ash. Soon, this area of the desert became known as “Footprints.”

Barefoot walkers left thousands of footprints in wet volcanic ash within a few miles southwest of Kīlauea’s summit.

Many historians and Hawaiians believe the footprints were made by Keōua and his warriors. Keōua was known to be in the area at the time, and previous thought suggested this part of the desert did not have pre-contact use, so it was narrowed down to them.

Scientists later investigated – one approach was to look deeper at the evidence.

Forensic studies indicate that the length of a human foot is about 15% of an individual’s height. A man’s foot may be slightly more that 15%, a woman’s slightly less, but it is possible to estimate the height to a couple of inches. (USGS)

They measured 405-footprints to determine how tall the walkers were. The average calculated height is only 4-feet 11-inches, and few footprints were made by people 5-feet 9-inches or more tall. Early Europeans described Hawaiian warriors as tall; one missionary estimated an average height of 5-feet 10-inches. Many now believe that most of the footprints were made by women and children, not by men, much less warriors. (USGS)

Meanwhile, Keōua’s party was camped on the upwind side of Kīlauea’s summit – perhaps on Steaming Flat – waiting for Pele’s anger to subside. They saw the sky clear after the ash eruption and began walking southwestward between today’s Volcano Observatory and Nāmakanipaio. (USGS)

Suddenly, the most powerful part of the eruption began, developing a high column and sending surges at hurricane velocities across the path of the doomed group. Later, survivors and rescuers made no footprints in the once wet ash, which had dried. (USGS)

Then, archaeologists looked for other evidence to help identify who the footprints may have belonged to. Contrary to general thought that the area was not used by the Hawaiians, archaeological investigations discovered structures, trails and historic artifacts in the area. (Moniz-Nakamura)

Most of the features were along the edge of the Keʻāmoku lava flow. Several of the trails converge south of the flow, suggesting a major transportation network. The structures are likely temporary, used as people were traversing through the desert on their way to/from Kaʻū and Hilo. (Moniz-Nakamura)

The sheer number of temporary shelters along the Keʻāmoku flow, as well as the trail systems and quarry sites, strongly suggest that this area was frequently used by Hawaiians travelling to and through the area – before and after the 1790 eruption. (Moniz-Nakamura)

If the footprints aren’t Keōua’s warriors, then how did one-third of his warriors die?

Several suggestions have been made: suffocation due to ash; lava, stones, ash and other volcanic material; or strong winds produced by the eruption, asphyxiation and burning killed them. (Moniz-Nakamura)

A more recent suggestion is that a “hot base surge, composed primarily of superheated steam … (traveling at) hurricane velocity” was the cause of death. The wind velocity prevented the people from running away; they probably huddled together, then “hot gases seared their lungs.” (Moniz-Nakamura)

Some now suggest that, if these observations and ideas are correct, the footprints were made in 1790, but not by members of Keōua’s group. (USGS)

A reconstruction of events suggests that wet ash, containing small pellets, fell early in the eruption, blown southwestward into areas where family groups, mainly women and children, were chipping glass from old pāhoehoe. They probably sought shelter while the ash was falling. Once the air cleared, they slogged across the muddy ash, leaving footprints in the 1-inch thick deposit. (USGS)

On August 1, 1916, President Woodrow Wilson signed the country’s 13th national park into existence – Hawaiʻi National Park. At first, the park consisted of only the summits of Kilauea and Mauna Loa on Hawaiʻi and Haleakalā on Maui.

Eventually, Kilauea Caldera was added to the park, followed by the forests of Mauna Loa, the Kaʻū Desert, the rain forest of Olaʻa and the Kalapana archaeological area of the Puna/Kaʻū Historic District.

In 1961, Hawaiʻi National Park’s units were separated and re-designated as Haleakalā National Park and Hawaii Volcanoes National Park.) (Lots of good information here is from USGS, NPS and Jade Moniz-Nakamura.)

November 28, 2017 by Peter T Young Leave a Comment

Halemaʻumaʻu

“Astonishment and awe for some moments rendered us mute, and like statues, we stood fixed to the spot, with our eyes riveted on the abyss below. Immediately before us yawned an immense gulf, in the form of a crescent, about two miles in length, from north-east to south-west, nearly a mile in width, and apparently eight-hundred feet deep.”

“The bottom was covered with lava, and the south-west and northern parts of it were one vast flood of burning matter, in a state of terrific ebullition, rolling to and fro its ‘fiery surge’ and flaming billows.” (Ellis, 1823)

In 1823, Reverend William Ellis visited Kīlauea caldera on his journey around the island of Hawaiʻi. He was the first foreigner to be shown the home of Pele.

By the time Ellis arrived, more than 300-years after the summit collapses of the late 1400s, the caldera had begun to refill. He measured the chasm from the highest rim to its depths; it was over 1,000-feet deep, with a series of terraces that stepped down to a vast inner crater that occupied nearly half the caldera’s floor. (NPS)

“Sometimes I have seen what is called Halemaʻumaʻu, or South Lake, enlarged to a circuit of three miles, and raging as if filled with infernal demons”. (Halemaʻumaʻu is lit., fern house.)

“On another occasion I found the great South Lake filled to the brim, and pouring out in two deep and broad canals at nearly opposite points of the lake.”

“The lava followed these crescent fissures of fifty or more feet deep and wide until they came within half a mile of meeting under the northern wall of the crater, thus nearly enclosing an area of about two miles in length and a mile and a half in breadth.”
(Coan)

According to Hawaiian oral tradition, the Kīlauea caldera formed during an epic battle between Pele, the Hawaiian volcano deity, and her younger sister, Hiʻiakaikapoliopele (Hiʻiaka.)

Pele had sent Hiʻiaka to fetch her lover, Lohiʻau, from Kauai. Upon returning, Hiʻiaka discovered that Kawahine‘aihonua (Pele, the woman who eats the land) had broken her promise and set fire to Hiʻiaka’s beloved ‘ʻōhiʻa forests.

To avenge this transgression, Hiʻiaka made love to Lohiʻau at the summit of the volcano, in full view of her sister. Pele lashed out in anger and buried Lohiʻau beneath a flood of lava.

Driven by remorse, Hiʻiaka dug furiously to recover the body. Rocks flew as she dug the great pit. Their brother stopped Hiʻiaka from digging deeper, for doing so would surely have let in water and put out the fires of Pele. Thus the great caldera of Kīlauea was formed. (NPS)

Within the heart of Kīlauea, a great reservoir swells with magma prior to an eruption. In the late 1400s, however, large volumes of magma erupted or moved elsewhere in the volcano, emptying the magma reservoir.

Its internal support withdrawn, the top of the mountain collapsed, accompanied by explosive eruptions. Great blocks of the old summit slumped inward. The gaping depression that formed was ringed with stepped terraces descending to its floor. (NPS)

The summit caldera (‘crater’) of Kilauea is 2-1/2 miles long and 2 miles wide and its floor has an area of approximately 2,600-acres. Near its southwestern edge the caldera floor is indented by the depression Halemaʻumaʻu, the ‘Fire Pit,’ a collapsed crater about 3,200-feet wide. (NPS)

Geologic evidence suggests that the modern caldera of Kīlauea formed shortly before 1500 AD. Repeated small collapses may have affected parts of the caldera floor, possibly as late as 1790. For over 300-400 years, the caldera was below the water table.

Kīlauea is an explosive volcano; several phreatic eruptions have occurred in the past 1,200 years. (Phreatic eruptions, also called phreatic explosions, occur when magma heats ground or surface water.)

There were explosions in 1790, the most lethal known eruption of any volcano in the present US. The 1790 explosions, however, simply culminated (or at least occurred near the end of) a 300-year period of frequent explosions, some quite powerful. (USGS)

Keonehelelei is the name given by Hawaiians to the explosive eruption of Kilauea in 1790. It is probably so named “the falling sands” because the eruption involved an explosion of hot gas, ash and sand that rained down across the Kaʻū Desert. The character of the eruption was likely distinct enough to warrant a special name. (Moniz-Nakamura)

The 1790 explosion led to the death of one-third of the warrior party of Kaʻū Chief Keōuakūʻahuʻula (Keōua.) At the time Keōua was the only remaining rival of Kamehameha the Great for control of the Island of Hawaiʻi; Keōua ruled half of Hāmākua and all of Puna and Kaʻū Districts. They were passing through the Kīlauea area at the time of the eruption. (Moniz-Nakamura)

Estimates of the number of fatalities range from “about 80 warriors” (William Ellis) to about “400 people” or “800 warriors” (Stephen Desha) to “5,405 countrymen” (David Douglas, quoting an eyewitness, a Priest of Pele, in 1834.) The lower numbers are probably most realistic. The dead were warriors and family members of Keōua’s army bound for Kaʻū. (NPS)

The next subsidence of the caldera floor occurred in 1868, when large earthquakes shook the southern part of Hawaii and simultaneous eruptions occurred from Mauna Loa and Kilauea. An area about 6,200-ft wide on the central caldera floor sagged about 330-ft, and a deeper conical pit about 900 m wide and about 3,000-ft developed at its southwest end at Halemaʻumaʻu. (USGS)

The pit again filled, and by 1874 a lava shield at Halemaʻumaʻu had once again grown to about the elevation of the southern caldera rim. Minor subsidences in and around Halemaʻumaʻu occurred again in 1879, 1886, 1891, and 1894.

The subsidence of 1894 was followed by 13-years of dormancy and very subdued, episodic activity within the pit of Halemaʻumaʻu. (USGS)

Lava returned to Halemaʻumaʻu shortly after the 1924 explosions ceased, but instead of being sustained the activity was now episodic. A series of seven brief eruptions in the next 10-years reduced the depth of Halemaʻumaʻu from 390 to 150 m, and then no eruptions occurred for 18 years, from 1934 to 1952.

Sustained eruption from June to November of 1952 filled Halemaʻumaʻu with another 120 m of lava. A brief eruption in May-June 1954 added 6 m of lava in Halemaʻumaʻu and a thin lava flow on the caldera floor to the east (Macdonald, 1955) (USGS)

The eruption of Kīlauea volcano continues at two locations. In the park, the vent within Halemaʻumaʻu Crater is easily viewed from the overlook at the Jaggar Museum. The second location is the Pu’u ‘Ō’ō vent located 10 miles east of the summit, on the remote east rift zone of Kīlauea. This area is not accessible to the public.

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Overlook at Jaggar Museum-Shiinoki

Kilauea’s summit caldera-Dzurisin-1980

Kilauea Aerial

‘Kilauea_Volcano’,_oil_on_canvas_painting_by_William_Pinkney_Toler,_c._1860s

Kilauea_Summit-Halemaumau-Klemetti

Kapiolani_Defying_Pele-(HerbKane)

Halemaumau-1930

Eruption column from Halemaumau. Photo by Tai Sing Loo at 1500 on May 23, 1924 from near Volcano house or HVO-(USGS)

0820. cloud is now over 3.7 km high-three lightning bolts observed in the column-(USGS)-1924

January 3, 2016 by Peter T Young 1 Comment

Collapse to Caldera

The Hawaiian Islands are volcanic in origin. Each island is made up of at least one primary volcano, although many islands are composites of more than one. The Big Island, for instance, is constructed of 5 major volcanoes: Kilauea, Mauna Loa, Mauna Kea, Hualālai and Kohala. Mauna Loa is the largest active volcano on Earth.

Kilauea is presently one of the most productive volcanoes on Earth (in terms of how much lava it erupts each year). The primary volcanoes on each of the islands are known as a shield volcanoes, which are gently sloping mountains produced from a large number of generally very fluid lava flows. (SOEST)

To the casual observer, Kilauea appears to be part of the larger volcano Mauna Loa, but geological data indicates that it is a separate volcano with its own vent and conduit system. (livescience) When Kilauea began to form is not known, but various estimates are 300,000-600,000-years ago. (USGS)

Kilauea is a broad shield volcano built against the southeastern slope of Mauna Loa. The summit presently has a caldera that is roughly 2.5-miles by 2-miles wide, and walls nearly 400-feet. Another feature, known as Halemaʻumaʻu crater, lies within the main caldera (on the southwestern side.)

For the past century, Halemaʻumaʻu has been the principal site of activity at Kilauea’s summit. There has also been frequent activity along the Southeast rift zone (such as the presently active Puʻu ʻOʻo eruption, which started in 1983.)

While at nearby Mauna Loa eruptions tend to occur in pairs (i.e., a summit eruption followed by one on the flank), Kilauea’s pattern of summit versus flank activity appear to be more random. However, evidence of numerous flank eruptions occurring after a summit eruption can be found. (SOEST)

Sometimes, volcano summits form calderas. When an erupting volcano empties a shallow-level magma chamber, the edifice of the volcano may collapse into the voided reservoir, thus forming a steep, bowl-shaped depression called a caldera (Spanish for kettle or cauldron.)

The summit regions of many active shield volcanoes are marked by calderas. Hawaiian examples include the Mokuaweoweo caldera on Mauna Loa and the Kilauea caldera on Kilauea. (sdsu-edu)

So, when and how was the Kīlauea Caldera formed?

The modern caldera at Kilauea collapsed in about 1470-1500 AD, as recognized by geologic field work and C-14 radiocarbon dating. Two lines of geologic evidence indicate it was very deep soon after it formed, as is also suggested by Hawaiian oral tradition.

Scientists suggest at least a couple possibilities exist for the collapse. One is that the magma reservoir emptied rapidly without erupting; the other possibility is that magma withdrawal was prolonged, not rapid, in response to slow eruption of the ʻAilāʻau lava flow (the largest in Hawaiʻi in more than 1000 years.)

The flow erupted on the east side of Kilauea’s summit during a ca. 60-yr period ending in about 1470. It has typical tube-fed formation, consistent with slow eruption. The eruption just predates the caldera – its shield is cut by the outermost caldera fault – and in fact could have ended when the caldera formed. (Swanson)

Geologic evidence indicates that the caldera appeared in about AD 1500, give or take several decades. It developed at the end of, or soon after, a 60-year-long eruption from the ʻAilāʻau shield just east of Kilauea Iki, flooding much of Puna with lava flows. The caldera formed at the start of, or shortly before, a series of explosions that radiocarbon ages date to about AD 1500. (USGS)

However, most geologic models assume very rapid removal of material to form a caldera. The argument is that a large void cannot support itself underground, so an empty volume of a few cubic miles could not exist for long. If so, a huge volume of magma must have almost instantaneously left the reservoir under Kilauea’s summit, leaving a void into which the summit fell.

Both geologic and cultural evidence should exist for such a major volcanic event. Indeed, the events are likely chronicled in the Pele-Hiʻiaka chants. But neither cultural nor geologic evidence tells us where the rocks disappeared when the top of the volcano sunk to form the caldera.

How much material was removed? The volume is uncertain but very large. If the entire caldera formed at one time, scientists estimate a volume of 1.4 cubic miles, equivalent to 780-million loads for a 10-cubic-yard dump truck. That estimate is based on the caldera’s dimensions when first surveyed in the 1820s and on guesses as to how much deeper it might have been. (USGS)

Historical eruptions at Kilauea volcano have occurred from both the summit caldera and from vents along the East Rift Zone. The historical record began with a very explosive eruption in 1790.

After this, the volcano was almost continuously active, mostly showing gentle effusion from a lava lake at the summit until 1924, when it again erupted explosively. The period 1924 to 1955 saw mostly short-duration summit eruptions.

From 1955 to the present Kilauea has seen mostly East Rift Zone activity interspersed with small summit eruptions. Two notable rift eruptions were Mauna Ulu (1969-1974) and Puʻu ʻOʻo (1983-present). Kilauea’s Eruption rate diminished steadily over the first half of the historic period but has been increasing again since 1924. (SOEST)

Since the Puʻu ʻOʻo eruption started on January 3, 1983, the southern part of the caldera has been sinking 2.5-4 inches/year. (USGS)

Currently there are 3 Hawaiian volcanoes that we can be classified as active: Kilauea, actively erupting since 1983; Mauna Loa, which last erupted in 1984 and is building for a new eruption in the next few years; and Loihi, which erupted in 1996.

All three of these active Hawaiian volcanoes share the Hawaiian hot spot, but retain unique volcanic histories and compositions.

The most likely dormant volcanoes are: Hualālai, which last erupted in 1801; Haleakalā, which last erupted in about 1790; and Mauna Kea, which last erupted about 4,000-years ago. (SOEST)

Due to the ongoing eruption, portions of the Hawaiʻi Volcanoes National Park are periodically closed, due the hazardous and unsafe conditions; check conditions and area closures before venturing.

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