What We Know About Hawaii's Lava Fountains at Kilauea Volcano

The ground beneath Kilauea's summit expanded by roughly half a meter a day before the volcano's recent lava fountains broke out, according to US Geological Survey data described in a recent edition of the journal Science and reported by Ars Technica. That rapid inflation, tracked through a dense network of monitoring stations, let scientists anticipate eruptions that had almost no warning seismic signature.

How rare are fountain eruptions at Kilauea?

Kilauea is the youngest and most active volcano in Hawaii, yet it has produced only three fountaining episodes since 1823, according to the USGS research cited by Ars Technica. That scarcity is part of why the current sequence, which began in 2024, has drawn sustained scientific attention: it offers one of the best-documented records yet of how a fountain-driven eruption builds and releases.

A 2018 eruption at Kilauea partially drained one of the volcano's underground lava reservoirs. Starting in 2019, that reservoir began refilling, and the process did not stay steady. The inflation rate climbed to more than 22 centimeters a year, then doubled to 57 centimeters a year in 2023, with the swelling spreading to a nearby caldera, the USGS data show.

What happened when the fountains actually started?

In 2024, a large series of earthquakes accompanied the opening of a 900-meter-long fissure, and lava fountains reached as high as 160 meters into the sky over a 13-hour span, according to the research. A second eruption followed less than a day after the first one subsided. From there, the activity kept going: as of last month, 52 additional fountain eruptions had occurred, the USGS reported, and the most violent of them sent lava more than 400 meters into the air.

"Seismic, infrasound, geodetic, gas, and visual and thermal cameras" were among the tools researchers used to track the volcano, according to the USGS data cited by Ars Technica.

That instrumentation — 35 separate data-gathering stations positioned across Kilauea — gave scientists a multi-channel view of the volcano's behavior that most eruptions elsewhere do not get.

How did scientists predict when the next fountain would erupt?

Perhaps the most practically useful finding from the sequence was that eruptions became predictable, despite the absence of clear seismic warning signs. Each fountain eruption caused the summit of Kilauea to deflate rapidly, followed by a slower refilling of the Halemaʻumaʻu magma reservoir, the USGS research found. Consecutive eruptions tended to occur once the summit's ground tilt reached similar levels to the tilt that preceded the previous eruption.

The precise tilt threshold associated with eruptions drifted downward over the course of the sequence, the data show, but the gap between the tilt levels of consecutive eruptions stayed relatively small and consistent. That pattern let the USGS issue alerts ahead of eruptions that otherwise gave almost no immediate seismic clue they were coming, according to the agency's findings reported by Ars Technica.

What mechanism is believed to cause lava to fountain instead of flow?

Most hotspot volcanism worldwide is comparatively slow-moving, with lava creeping down slopes at a pace people can walk away from. Fountaining is different, and it is largely confined to a handful of locations — Mount Etna, Hawaii, and Iceland among them — where lava can be expelled hundreds of meters into the air. Researchers still do not have a settled explanation for what powers that difference, according to the Science paper summarized by Ars Technica.

One leading idea under examination is that pressure inside a magma reservoir keeps water mixed with other volcanic material until the magma rises to a shallow enough depth, at which point the water can flash into steam and drive the explosive fountaining. The Kilauea sequence, with its dense instrumentation and repeated, well-documented eruptions, gives researchers a rare opportunity to test that mechanism against real-time inflation, tilt, and eruption data rather than reconstructing events after the fact.

Why does this matter beyond Hawaii?

Fountain-forming volcanoes are not limited to Kilauea, and the forecasting method built around summit tilt — rather than seismic precursors alone — could prove useful at other fountaining sites such as Etna and Iceland's volcanic systems, where similar monitoring networks exist. The USGS's ability to flag eruption windows using ground deformation data, even without a seismic lead-up, is being treated as a template for watching other active calderas, according to the research described by Ars Technica.

For now, the Kilauea sequence remains active, with scientists continuing to log tilt measurements against the pattern established since 2024 to anticipate whatever comes next.