Halemaʻumaʻu (Hawaiian: [hɐlɛˈmɐʔuˈmɐʔu]) anglicized as “Halemaumau” is a pit crater within the much larger Kīlauea Caldera at the summit of Kīlauea volcano on island of Hawaiʻi. The roughly circular crater was 770 m × 900 m (2,530 ft × 2,950 ft) before collapses that roughly doubled the size of the crater after May 3, 2018. Following the collapses of 2018, the bottom of Halemaʻumaʻu was roughly 600 m (2,000 ft) below the caldera floor. Halemaʻumaʻu is home to Pele, goddess of fire and volcanoes, according to the traditions of Hawaiian religion. Halemaʻumaʻu means "house of the ʻāmaʻu fern". Halemaʻumaʻu contained an active lava lake for much of the time before 1924, and was the site of several eruptions during the 20th century. The crater again contained an active lava lake between 2008 and 2018, with the level of the lava usually fluctuating between 20 and 150 meters below Halemaʻumaʻu's crater floor, though at times the lava lake rose high enough to spill onto crater floor. The lava lake drained away in May 2018 as new volcanic vents opened in lower Puna. 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. The collapse events ceased abruptly on August 2, 2018. A small water pond appeared in Halemaʻumaʻu in the summer of 2019. The pond deepened and enlarged into a small lake after it was first observed, measuring 167 feet (51 m) deep on December 20, 2020. An eruption in December 2020 completely boiled away the water lake. This and several subsequent eruptions have partially refilled the crater with lava. The most recent eruption at Halemaʻumaʻu began on December 23, 2024, with episodes of fountaining continuing as of 2026.
Geological history – 1823 to 2008
1823 to 1894: Caldera lava lake and formation of 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:
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 (3.2 km) in length, from north-east to south-west, nearly a mile in width, and apparently 800 feet (240 m) 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.
From the time Ellis made his observations in 1823 (and likely some time before that as well) through 1840, a lava lake was present within a broad region of Kīlauea Caldera. Between 1840 and 1894, the size of the lava lake gradually got smaller, becoming localized near the present site of Halemaʻumaʻu. In 1866, Mark Twain, an American humorist, satirist, lecturer, and writer hiked to the Caldera floor. 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. After the disappearance of lava, Halemaʻumaʻu was left behind as a circular pit crater 360 metres (1,180 ft) wide. Sporadic eruptions took place within Halemaʻumaʻu over the following decade, while continued collapse events deepened Halemaʻumaʻu to 300 metres (980 ft) by March 1899.
1906 to 1924: Reemergence of lava lake and explosive eruption
By the end of 1906, the lava lake was again present nearly all of the time. At the time geologist Thomas Jaggar opened the Hawaiian Volcano Observatory in 1912, Halemaʻumaʻu was nearly full with active lava. 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. Beginning during the night of May 9–10, 1924, a period of explosive eruptions took place at Halemaʻumaʻu. The explosions emitted large explosive columns of ash and other debris up to 9 kilometres (5.6 mi) high that precipitated on surrounding communities. 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. The explosive blasts also ejected rocks out of Halemaʻumaʻu, some as large as 14 tons. One person was killed during an explosion on May 18 after being crushed by falling debris. The explosions continued for two and a half weeks, finally ceasing on May 27. Halemaʻumaʻu more than doubled in size during the eruption. The crater's diameter grew to approximately 1,000 metres (3,300 ft), while the crater's depth increased to about 285 metres (935 ft).
1924 to 1982: Short-lived eruptions partially fill Halemaʻumaʻu After the 1924 events, seven eruptions occurred within Halemaʻumaʻu between 1924 and 1934, partly refilling the crater. Following the 1934 eruption, Halemaʻumaʻu was relatively quiet until 1952, when a six-month long eruption took place. Subsequent eruptions in the 1950s, 1960s, and 1970s partially refilled the crater. A 1982 eruption covered a small portion of the northeastern crater floor.
2008 to 2018 eruptive activity
Beginning of the eruption
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