Halemaʻumaʻu

The subsidence of the lava lake was accompanied by a period of explosions, earthquakes, large clouds of ash and toxic gas, and finally a gradual collapse of the summit caldera around Halemaʻumaʻu.

William Ellis, a British missionary and amateur ethnographer and geologist, published the first English description of Kīlauea Caldera as it appeared in 1823.

Ellis observed a large lake of molten lava:[6] 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.

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.

[8] He wrote the following account of the lake of molten lava which he found there: It was like gazing at the sun at noon-day, except that the glare was not quite so white.

At unequal distances all around the shores of the lake were nearly white-hot chimneys or hollow drums of lava, four or five feet high, and up through them were bursting gorgeous sprays of lava-gouts and gem spangles, some white, some red and some golden--a ceaseless bombardment, and one that fascinated the eye with its unapproachable splendor.

The more distant jets, sparkling up through an intervening gossamer veil of vapor, seemed miles away; and the further the curving ranks of fiery fountains receded, the more fairy-like and beautiful they appeared.

Following an earthquake swarm in December 1894, the lava lake fully drained away from Kīlauea's summit, ending the decades-long period of nearly continuous activity.

At the time geologist Thomas Jaggar opened the Hawaiian Volcano Observatory in 1912, Halemaʻumaʻu was nearly full with active lava.

[7] In February 1924, Halemaʻumaʻu's lava lake drained away, again leaving behind a pit crater 150 metres (490 ft) deep.

Beginning on April 29, of that year, the crater floor began to collapse, eventually deepening to more than 210 metres (690 ft) deep by May 7, 1924.

In the community of Glenwood, 16 kilometres (9.9 mi) from Halemaʻumaʻu, gutters on the roof of a store collapsed due to the weight of muddy ash.

[13] At 02:58 am HST on March 19, 2008, HVO personnel recorded seismic events, and sunrise revealed a 20–30 meter (65–100 foot) diameter hole blown in the side where the vent once was; the explosion scattered debris and spatter across 0.30 square kilometers (74 acres) and damaged the Crater Overlook.

Several days later, lava began to emerge from fissures on the lower east rift zone in Leilani Estates.

On May 1, concurrent with the shift of activity on Kīlauea's east rift zone, the summit lava lake within Halemaʻumaʻu's Overlook Crater began to drop; the US Geological Survey's status update on the evening of May 6 reported that Halemaʻumaʻu's Overlook Crater lava lake had dropped by 722 feet (220 m) since April 30.

[3] Geologists believed that the draining of the lava lake was driven by a steady withdrawal of magma from Kīlauea's summit to feed the eruption on the volcano's lower east rift zone.

[3] Beginning near the end of May, the floor of Kīlauea Caldera around Halemaʻumaʻu began to subside in a series of 62 separate collapse events.

[29] The summit collapse events ceased abruptly on August 2, 2018, two days before the eruptive activity on Kīlauea's east rift zone decreased significantly.

[3] In late July 2019, helicopter pilots reported seeing a green pond of water at the bottom of the much-deepened Halema'uma'u crater.

[33] The lake marked the first time in recorded history that liquid water appeared in Halemaʻumaʻu crater in the form of a crater lake,[34] though the US Geological Survey noted that at least one other small pond, thought to mark a body of perched water trapped by dikes, was present in the caldera just north of Halemaʻumaʻu prior to the caldera's collapse in 2018.

The eruption had been preceded by earthquake swarms centered under Kīlauea Caldera on November 30, 2020, and December 2, 2020, the second of which was interpreted as a small intrusion of magma.

[39] County emergency officials reported that the eruption had stabilized by the following morning and that two of the three vents remained active and continued to fill the floor of Halemaʻumaʻu with lava.

[44] The Hawaiian Volcano Observatory began to record increased earthquake activity and changes in ground deformation patterns at Kīlauea's summit at about noon local time on September 29, 2021.

[45] An eruption began at 3:20 p.m. local time when several fissures opened within Halemaʻumaʻu crater in Kīlauea's summit caldera.

[48][49] On January 5, 2023, the Hawaiian Volcano Observatory reported that Kīlauea began erupting within Halema‘uma‘u at approximately 4:34 p.m.