Kilauea has spilled 29 overflows in two days and forecasters expect fountains within hours

Kīlauea’s summit eruption has entered its precursory stage again, with the north vent inside Halemaʻumaʻu spilling lava intermittently since the afternoon of September 7. By the following morning, the U.S. Geological Survey’s Hawaiian Volcano Observatory had logged 29 separate overflows and raised its alert level, and scientists say the pattern points toward a new episode of sustained lava fountaining arriving imminently. The exact timing remains uncertain, but the volcano’s own ground deformation and gas signals are the clearest indication yet that episode 55 of the ongoing eruption is close.

Twenty-nine overflows and a narrowing forecast window

According to the Hawaiian Volcano Observatory’s daily update issued the morning of September 9, the first sluggish overflow from the north vent began around 12:45 p.m. HST on September 7, prompting HVO to raise the volcano alert level to WATCH and the aviation colour code to ORANGE. By the time of that update, 29 overflows had occurred, ranging from 15 minutes to roughly two hours long and separated by pauses of 15 minutes to eight hours. HVO’s scientists said a forecast window of September 9 to 10 was likely for the fountaining episode itself to begin, though they cautioned the onset could slip by several days if the summit’s ground swelling stalls or reverses.

Inside Halemaʻumaʻu’s north vent

The overflows have grown steadily more vigorous, fed by a dome fountain that HVO measured at 15 to 30 feet (5 to 10 metres) tall. Two lava flows have built up from the activity, one extending about half a mile (one kilometre) southwest of the north vent and the other reaching just under half a mile northeast of it. The south and west vents in Halemaʻumaʻu have not overflowed, though observers noted occasional glow and flame visible from those openings overnight. Tremor has continued across the summit with recurring bursts of gas-piston activity roughly every five minutes, and two small earthquakes were recorded beneath the summit region in the 24 hours before the update.

What the ground beneath the summit is doing

Kīlauea’s summit has been reinflating unevenly since its last fountaining episode ended on August 25. Around 3 p.m. HST on September 7, a tiltmeter at the UWD station recorded a peak of about 13.2 microradians of inflation, higher than the level the ground had reached when episode 54 began. That peak was followed by roughly a microradian of deflation as the precursory overflows started, then a slower, irregular inflation of about half a microradian. As of the September 9 update, UWD sat at approximately 12.3 of the 12.7 microradians the ground had lost during episode 54’s fountaining, a level HVO said was largely unchanged from the day before. Sulfur dioxide emissions, which typically run between 1,000 and 5,000 tonnes a day during pauses between episodes, were being carried southwest of the caldera on weak trade winds, with HVO warning that stronger winds could push ash and Pele’s hair in that direction once fountaining resumes.

Episode 54 set the bar for what could come next

The previous episode offers a guide to what the next round of fountaining might look like. Episode 54 ran for about nine hours on August 25, from roughly 10:30 a.m. to 7:33 p.m. HST, with the north vent’s fountains reaching a maximum height of approximately 500 feet (150 metres) between 12:15 and 1 p.m. Neither the south vent nor a newer west vent, formed from a former collapse pit, fountained during that episode. The eruptive plume climbed to roughly 17,000 feet (5,200 metres) above sea level, and while most tephra fall stayed within the closed section of Hawaiʻi Volcanoes National Park, HVO also received a report of trace Pele’s hair reaching the Kaʻū district. Kīlauea has been erupting episodically from the north and south vents since December 23, 2024, a timeline HVO tracks alongside a running map of the eruption, with individual fountaining episodes generally lasting under 12 hours and separated by pauses of two weeks or more.

Hurricane Lowell complicated the view from HVO’s cameras

The precursory activity has unfolded against an unusual backdrop: Hurricane Lowell’s close pass west of the main Hawaiian Islands earlier in the week left HVO’s summit webcams obscured by heavy rain, cloud and steam for several days, only clearing on the morning of September 9. The observatory said its monitoring network had mostly recovered from power and storm-related outages tied to the hurricane, though it noted that several summit instrument stations remained offline while technicians worked to restore connections. In the absence of clear webcam views into the vents during some overflows, HVO relied on changes in the tremor signal to estimate how long individual overflows lasted.

Why the public still can’t get close

Halemaʻumaʻu’s caldera rim has been closed to visitors since late 2007, and HVO’s hazard notes make clear why that closure has outlasted years of intermittent eruption: the crater rim near the active vents is prone to cracking, slumping and small landslides that can expose molten material beneath the surface, on top of the volcanic gas, tephra and hot lava hazards produced by the eruption itself. The observatory said it remains in contact with Hawaiʻi Volcanoes National Park and the Hawaiʻi County Civil Defense Agency as episode 55 approaches, and that any significant change in activity between its daily updates would be posted as a separate notice rather than held for the next scheduled report.

This article was produced with the assistance of AI and reviewed by Morning Overview editors prior to publication.

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