Halemaʻumaʻu

1823 to 1894: Caldera lava lake and formation of Halemaumau 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: 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: 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 wide. 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 high that precipitated on surrounding communities. In the community of Glenwood, 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. The crater's diameter grew to approximately , while the crater's depth increased to about . ==2008 to 2018 eruptive activity==

Beginning of the eruption Halemaʻumaʻu was quiet for 25 years after the 1982 eruption, with eruptive activity at Kīlauea being focused on the volcano's east rift zone beginning in 1983. However, Hawaiian Volcano Observatory scientists observed a gradual increase in activity beginning in late 2007, including an increase in sulfur dioxide emissions and an increase in seismic tremor. By March 2008, these parameters were several times higher than normal. 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 and damaged the Crater Overlook. Pieces as large as were found on Crater Rim Drive while blocks hit the crater overlook area. This was the first explosive eruption of Halemaʻumaʻu since 1924, and the first lava eruption from the crater since 1982. The new crater formed in the explosion was informally named "Overlook Crater" by Hawaiian Volcano Observatory staff. On April 16, 2008, a third significant explosive event occurred at Halemaʻumaʻu, spreading ash and debris throughout the area. Subsequently, a second evacuation of the park and surrounding areas was ordered on April 23, 2008. Activity continued through the next few months, with Halemaʻumaʻu continuing to emit a plume of ash and gases. A fourth explosive event occurred on August 1, 2008, and a fifth on August 27, 2008. September 2008: Lava lake becomes visible A Hawaii Volcano Observatory news release and images dated September 5, 2008, confirmed the first recorded images of a lava lake 130 feet below the lip of the Overlook Crater. The HVO had alluded to the presence of lava within the vent, including the sporadic ejecting of lava materials from the vent due to explosive episodes, but this gave officials the first opportunity to visually confirm that active lava was present. The report also noted that the lava could not be seen from observation points around the crater. For three years from 2015 to 2018 the lava lake level remained close to the rim, with a further minor overflow event in October 2016 and a significant one in April 2018 that covered a majority of the crater floor in new lava. April to July 2018: Drainage of lava lake and the collapse of the summit caldera On April 30, the Puʻu ʻŌʻō crater on Kīlauea's east rift zone collapsed. 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 since April 30. By May 10, the lava lake was no longer visible. 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. Several small explosive events occurred between May 16 and May 26, ejecting ash and small blocks within a few hundred meters of the vent. The summit collapse events ceased abruptly on August 2, 2018, two days before the eruptive activity on Kīlauea's east rift zone decreased significantly. ==2019–20 water lake==

In late July 2019, helicopter pilots reported seeing a green pond of water at the bottom of the much-deepened Halema'uma'u crater. Geologists from the Hawaiian Volcano Observatory confirmed the presence of water during a helicopter fly-over on August 1, 2019. Further observation in August showed the pond was rising, with a water temperature of about . Hawaiian Volcano Observatory scientists believe that the lake formed because the 2018 collapse events caused the floor of Halemaʻumaʻu to collapse below the level of the local water table. The scientists suspect that the water table likely collapsed along with the rest of the crater but began to recover elevation after the collapse. Because the bottom of Halemaʻumaʻu was believed to be roughly lower than level of the area water table after the collapse, water was able to inundate the crater floor as it rose. The lake marked the first time in recorded history that liquid water appeared in Halemaʻumaʻu crater in the form of a crater lake, 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. As of July 2020, the dimensions of the water lake were approximately , covering an area of about six acres and containing over of water. The lake was over deep, and had risen an average of each week since the lake was first seen in July 2019. The lake continued to deepen through December 2020 and measured deep, before the onset of an eruption that began on December 20. ==2020–21 eruption ==

On December 20, 2020, at 9:30 pm local time, an eruption broke out within Halemaʻumaʻu. The US Geological Survey's Hawaiian Volcano Observatory reported that three vents were feeding lava into the bottom of Halemaʻumaʻu Crater, boiling off the water lake that had been growing since summer 2019 and replacing it with a lava lake. The observatory reported that the eruption created a plume that reached 30,000 feet in elevation. 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. 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. As of 7:30 a.m. on December 25, 2020, the lava lake had filled in of the crater and the level of the lake was continuing to rise. , the western-most vent remained active and the lava lake had increased to a depth of about , though the eastern portion of the lava lake had stagnated. On May 26, 2021, the Hawaiian Volcano Observatory announced in a daily update that Kīlauea was no longer erupting. Lava supply to the lava lake appeared to have ceased between May 11 and May 13, and the lava lake had completely crusted over by May 20. The last surface activity in Halemaʻumaʻu was observed on May 23. At the time eruptive activity ceased, the lava lake was deep and had a volume of approximately . ==2021–22 eruption==

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. An eruption began at 3:20 p.m. local time when several fissures opened within Halemaʻumaʻu crater in Kīlauea's summit caldera. During the initial stages of the eruption, lava erupted in fountains more than tall, though the height of the fountains declined as the level of lava in the crater rose, partially drowned the erupting vents. The eruption continued until December 9, 2022, when lava supply to the active lava lake ceased and the lake surface crusted over. On December 13, 2022, the Hawaiian Volcano Observatory determined that the eruption had ended. Over the course of the eruption, of lava had been effused, and the floor of Halemaʻumaʻu had risen , since the beginning of the eruption on September 29, 2021. ==2023 eruptions==

On January 5, 2023, the Hawaiian Volcano Observatory reported that Kīlauea began erupting within Halema‘uma‘u at approximately 4:34 p.m. HST. Fountain of up to high were reported. New lava flows inundated much of the crater floor and by 7:30 p.m. about depth of new lava had been added to the crater floor. The eruption ended 61 days later on March 7, 2023. Three months after the end of the previous eruption, another eruption began on June 7, 2023. On September 10, 2023, a new eruption began at approximately 3:15 HST. This eruption was contained within Halemaʻumaʻu crater and on the down dropped block to the east in Kīlauea's summit caldera. The eruption lasted one week, ending September 16. ==2024-26 eruptions==

On December 23, 2024, an eruption began within Halemaumau. 43 episodic eruptions, including lava fountains over 540 meters (1770 feet) high, have occurred . == Gallery ==

File:White-tailed Tropicbird is flying directly over the Halema`uma`u vent.jpg|White-tailed tropicbird flying directly over the Halemaʻumaʻu vent, 2008 File:Rainbow and sulfur dioxide emissions from the Halema`uma`u vent.jpg|A sulfur dioxide plume after an explosive 2008 eruption. File:Halema'uma'u Crater in Kilauea volcano, Hawaii..jpg|Halemaʻumaʻu, 2012 File:Halema’uma’u Crater Hawaii Volcanoes National Park VP8.webm|Time lapse video of Halemaʻumaʻu, 2014 File:Halemaʻumaʻu lava lake USGS multimediaFile-1585.webm|Time lapse video of the lava lake in Halemaʻumaʻu, 2016 File:2017-Halemaumau-lava-lake.jpg|Halemaʻumaʻu, 2017 File:2017-Halemaumau-Vtorov.ogv|Time lapse video of Halemaʻumaʻu, 2017 Kīlauea volcano - Halemaʻumaʻu crater eruption in 2023 (C0608).webm|The lava lake in Halemaʻumaʻu, 2023 ==References==