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May 5, 2022

May 3 marked the 4th anniversary of the start of Kīlauea’s historic 2018 eruption that covered much of lower Puna with lava flows and dropped the crater floor of the summitThis anniversary is an appropriate time to reflect on the dynamic landscape we share and the events of the past 4 years. At the same time, we’re considering what these recent changes might mean for future activity at Kīlauea.

Volcano Watch is a weekly article and activity update written by U.S. Geological Survey Hawaiian Volcano Observatory scientists and affiliates. This week’s article was written by research geologist Drew Downs.

color photographs of volcano summit crater
A) Top left, photo of Halemaʻumaʻu before the 2018 collapse events started with the decade-long active lava lake that formed in 2008. B) Top right, photo after the 2018 collapse events had dropped the crater floor of Halemaʻumaʻu by more than 1,600 ft (500 m) over the course of just 4 months. C) Bottom left, in July 2019 a water lake started to form in the newly deepened Halemaʻumaʻu, and this lake continued to grow over the next year and a half. D) Bottom right, the eruption in December 2020 boiled away the water lake in a single night and continued until May 2021 before another eruption started in September 2021, continuing to the present. All photos are from the U.S. Geological Survey Hawaiian Volcano Observatory.

For some, Kīlauea Volcano seemed set in its ways, as it had been erupting for 35 years (1983–2018) at Puʻuʻōʻō on the middle East Rift Zone. The summit crater of Halemaʻumaʻu joined the action, and from 2008 to 2018 hosted a lava lake that drew people from around the world to enjoy its stunning views.

While seismographs, tiltmeters, and various other geophysical equipment were recording the beginning of changes at Kīlauea in 2018, the first major visible sign of something out of the ordinary occurred on April 30 with the sudden collapse at Puʻuʻōʻō. Just a few days later, on May 3, seismic activity had migrated beneath Leilani Estates and fissures opened. Before May was over, 24 fissures had erupted and lava flows would continue to inundate parts of lower Puna until September.

The summit crater of Halemaʻumaʻu also underwent major change, and its lava lake disappeared during the 2018 eruption. As lava flows in lower Puna drained the summit magma reservoir, Halemaʻumaʻu underwent 62 collapses (some with explosive eruptions). Each incremental collapse was marked by earthquakes that were felt throughout the summit. When the dust settled (and there was a lot of dust), the collapses had lowered the crater floor by more than 500 m (1,600 ft).

The end of the 2018 eruption and caldera collapse events brought a period of quiescence that had been unknown at Kīlauea for over 35 years. It also brought a new and interesting change to the volcano.

For the first time since written records began, a water lake formed within the deepened pit of Halemaʻumaʻu. First noticed in July 2019, the water continued to slowly fill the crater over the next year and a half until it was about 50 m (160 ft) deep.

On the night of December 20, 2020, the water lake boiled away within an hour or two as Halemaʻumaʻu burst into eruption again. Within less than a day the new lava lake was deeper than the water lake had been, and it continued to grow and fill in the crater until May 2021. Yet again, Kīlauea did not stay quiet for long. Halemaʻumaʻu began a new eruption in September 2021; an eruption that continues to this day. These two eruptions have filled Halemaʻumaʻu with over 320 m (1,050 ft) of lava.

Nearly continuous lava lake activity occurred for decades at Kīlauea’s summit in the 19th century. While the summit eruption within Halemaʻumaʻu doesn’t currently show signs of stopping, it can be easy to forget that Kīlauea has the potential to change quickly from one day to the next. Just glancing at the volcanic rocks, ash, and vegetation, or lack thereof, on Kīlauea testifies to inevitable events that can sometimes happen with remarkable speed over the course of months, weeks, or even days.

An important question on the minds of USGS Hawaiian Volcano Observatory (HVO) staff is what these recent changes portend for Kīlauea’s future? The appearance of the water lake at the summit in 2019 renewed attention on Kīlauea’s explosive potential. Native Hawaiians recorded Kīlauea’s major explosive events in their oral traditions and the possibility of explosive eruptions had everyone’s attention during this time. The dramatic switch to summit lava lake activity within Halemaʻumaʻu, has alleviated much of that concern.

Are we returning to a period of prolonged summit activity similar to the 1800s? Or will future activity be more similar to that in the three decades prior to the start of the Puʻuʻōʻō eruption? This period was marked by numerous small and short-lived periodic eruptions that alternated between Kīlauea’s summit and rift zones. 

It is not possible to know what exactly lies in store for Kīlauea’s future, though history and modern monitoring tools provide clues. While this volcanic environment can be dangerous, devastating, and tragic to behold, it is also inspiring, breathtaking, and commanding. With every change, we learn something new and hope to continue to increase our understanding of Kīlauea.


Volcano Activity Updates


Kīlauea volcano is erupting. Its USGS Volcano Alert level is at WATCH ( Kīlauea updates are issued daily.    

Over the past week, lava has continued to erupt from the western vent within Halemaʻumaʻu crater. All lava is confined within Halemaʻumaʻu crater in Hawai‘i Volcanoes National Park. Sulfur dioxide emission rates remain elevated and were last measured at approximately 2,600 tonnes per day (t/d) on May 4. Seismicity is elevated but stable, with few earthquakes and ongoing volcanic tremor. Summit tiltmeters show one minor inflation and deflation trend over the past week. For more information on the current eruption of Kīlauea, see

Mauna Loa is not erupting and remains at Volcano Alert Level ADVISORY. This alert level does not mean that an eruption is imminent or that progression to an eruption from the current level of unrest is certain. Mauna Loa updates are issued weekly.     

This past week, about 62 small-magnitude earthquakes were recorded below the summit and upper elevation flanks of Mauna Loa—the majority of these occurred at shallow depths less than 15 kilometers (9 miles) below sea level. Global Positioning System (GPS) measurements show low rates of ground deformation over the past week. Gas concentrations and fumarole temperatures at both the summit and at Sulphur Cone on the Southwest Rift Zone have remained stable over the past week. Webcams show no changes to the landscape. For more information on current monitoring of Mauna Loa, see:  

Two earthquakes were reported felt in the Hawaiian Islands during the past week: a M3.1 earthquake 9 km (5 mi) E of Pāhala at 31 km (19 mi) depth on May 3 at 5:41 a.m. HST and a M3.0 earthquake 10 km (6 mi) N of Volcano at 20 km (12 mi) depth on April 30 at 11:07 a.m. HST.

HVO continues to closely monitor Kīlauea’s ongoing eruption and Mauna Loa for any signs of increased activity.    

Please visit HVO’s website for past Volcano Watch articles, Kīlauea and Mauna Loa updates, volcano photos, maps, recent earthquake info, and more. Email questions to    

Volcano Watch is a weekly article and activity update written by U.S. Geological Survey Hawaiian Volcano Observatory scientists and affiliates.


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