Halemaʻumaʻu

Halemaʻumaʻu (six syllables: HAH-leh-MAH-oo-MAH-oo) 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 April, 2025.