Kilauea’s north vent started overflowing again ahead of a 55th eruption episode

The north vent inside Kilauea’s summit crater began overflowing again late on September 22, sending lava several hundred meters across the floor of Halemaumau in a pattern the U.S. Geological Survey’s Hawaiian Volcano Observatory says typically precedes a new fountaining episode. The observatory has kept Kilauea at Watch alert level and Orange aviation color code as of September 23, with the overflows marking the buildup toward what would be the volcano’s 55th eruption episode since the current sequence began in December 2024. No fountaining had started as of the observatory’s latest update, and scientists say the timing remains uncertain.

A vent that has done this before

Precursory overflows from the north vent resumed at 10:10 p.m. HST on September 22 and lasted about 24 minutes, according to the observatory’s notice, with additional overflows recorded at 11:44 p.m. that night and again at 2:46 a.m., 6:10 a.m. and 7:04 a.m. HST on September 23. Each lasted roughly half an hour and sent lava several hundred meters from the vent across the crater floor, the pattern the Hawaiian Volcano Observatory has come to treat as the opening act of an eruptive episode.

“It is presently unclear if this activity will lead to the onset of a lava fountaining episode at this time,” the observatory wrote in its September 23 notice, adding that “this low-level precursory activity can continue for hours to days before the lava fountaining episode begins.” That caveat is why the volcano’s alert level has held at Watch rather than moving to Warning, the tier the observatory reserves for a fountaining episode already underway.

What Watch and Orange actually signal

Watch paired with Orange means, in the U.S. Geological Survey’s own definitions, that a volcano is “exhibiting heightened or escalating unrest with increased potential of eruption, timeframe uncertain” or that an eruption already underway poses only limited hazards, including no or minor ash emissions. Kilauea has sat at that level through most of its current eruptive sequence, stepping up briefly to Warning only during the hours-long fountaining episodes themselves before returning to Watch once each episode ends.

That sequence has repeated 54 times since the eruption began. Episode 54 ran for roughly nine hours on August 25, from 10:30 a.m. to 7:33 p.m. HST, with fountains reaching about 500 feet above the vent and an ash-and-gas plume climbing to roughly 17,000 feet above sea level, according to the observatory’s volcano-updates page. A 55th episode would follow the same script if the current overflows escalate into fountaining, though the observatory has not set a date.

More than 50 episodes since December 2024

Kilauea’s summit has erupted intermittently inside Halemaumau crater since December 23, 2024, a run the National Park Service describes as “more than 50 eruptions since December 2024,” separated by pauses that have run from days to weeks. Individual episodes have often lasted a day or less, a pattern the park service says makes the intervening quiet stretches — like the one preceding this latest overflow — a routine part of the volcano’s current behavior rather than a sign it is winding down.

The observatory’s general Kilauea page places the volcano’s summit at 4,009 feet elevation on Hawaii’s Big Island and notes it has erupted dozens of times since 1952, including a nearly continuous run along its East Rift Zone from 1983 to 2018. The current episodic pattern, confined to the summit caldera rather than the rift zone, began after the 2018 collapse and a period of lava lake activity that started refilling Halemaumau in December 2020.

All of the activity, including the September 22 overflows, has stayed inside the crater and within Hawaii Volcanoes National Park boundaries. The park keeps the eruption site itself closed to visitors but leaves viewpoints open along Crater Rim Drive, warning that volcanic gas, unstable cliff edges and falling tephra remain hazards even from a distance.

Whether the overflow pattern turns into episode 55 in the coming hours or days is, by the observatory’s own account, not yet knowable. The Hawaiian Volcano Observatory said only that the low-level activity could persist before any fountaining begins, leaving the exact timing — as it has for each of the previous 54 episodes — to show up in the data before anyone can call it.

The observatory tracks each overflow with tiltmeters and webcams trained on Halemaumau, instruments that recorded the same buildup pattern ahead of episode 54 in late August. Ground deformation at the summit typically swells for hours before a fountain breaks the surface, giving scientists a rough window rather than a fixed countdown. That monitoring network is also why the observatory can say with confidence that the September 22 overflows originated specifically from the north vent rather than from any of the other vent complexes that have opened periodically along Halemaumau’s walls since December 2024.

Kilauea’s eruptive history gives the observatory a wide range of past episodes to compare against, from single-day fountaining events to the multi-day vent complex that opened September 14 and ran for two days before quieting on its own. Episode 55, if it materializes, would extend a sequence that has already run nearly two years without a break long enough to be called an end to the eruption.

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

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