Kīlauea summit swelling helps researchers forecast lava fountain windows

Kīlauea’s swelling summit can help researchers forecast windows for lava fountain eruptions in Hawaiʻi, according to a study reported on October 8. An analysis of the volcano’s recurring fountains found that the ground rose between episodes and subsided quickly during them. The pattern gives scientists another way to anticipate activity that can affect roads, park facilities and nearby communities, though it cannot pinpoint when a fountain will begin.

The researchers examined the first 39 episodes of a sequence that began at Kīlauea’s summit on December 23, 2024. By September 2026, the eruption had produced 54 distinct fountain episodes, the most recorded during a single Kīlauea eruption. The study, by A. F. Flinders and colleagues, was published in Science. The counts describe the sequence through September; they do not establish its eventual duration.

How summit swelling helps forecast Kīlauea’s fountains

Between fountains, the summit gradually swelled; during fountaining, it deflated rapidly. The researchers interpret that movement as consistent with pressure rising and falling in a shallow magma reservoir. They also found that fountains repeatedly began near recognizable ground-tilt thresholds. Those thresholds changed gradually as the eruption progressed, so they offer a guide to likely time windows rather than a fixed trigger point or an exact start time.

That signal mattered because most episodes were preceded by little increase in earthquake activity, according to Phys.org’s account of the research. The team combined measurements of ground movement with seismic, low-frequency sound, gas, satellite and camera observations. It also examined erupted rock and volcanic glass. Taken together, those records let the researchers compare what happened beneath and around the vents before, during and after repeated bursts.

What the observations suggest about volcanic gas

The findings also bear on competing explanations for how the fountains work. One proposes that water-rich gas bubbles released from rising magma help accelerate lava near the surface. Another involves carbon-dioxide-rich foam accumulating in a magma reservoir and then collapsing. The measurements offer clues, but the researchers have not established a complete mechanism for the repeated fountains.

From episode 14 onward, magma commonly rose and drained back repeatedly before sustained fountaining, Phys.org reported. The researchers associated this behavior with shallow gas accumulation and release. Science News also reported relatively little carbon dioxide among the observed gas signals. The team regarded the evidence as more consistent with the shallow gas explanation, while emphasizing that further observations are needed to settle the question.

The erupted material changed in a different way: its chemistry shifted over months, indicating periodic arrivals of hotter magma, according to Phys.org. The researchers did not find clear chemical changes within individual fountain episodes. That distinction matters because a longer-term change in the magma supply does not by itself explain the timing of each separate burst.

Why forecast windows matter around the summit

Some fountains in the sequence have reached roughly 480 metres, according to Phys.org. Windblown volcanic fragments have affected roads, park infrastructure and communities as far as about 70 kilometres from the fountains. A forecast window can help communicate the possibility of another episode to people who may be affected, even while the exact onset remains uncertain.

The eruption is in Hawaiʻi Volcanoes National Park, where the Hawaiian Volcano Observatory has livestreamed the activity. The study authors said the webcams were used especially heavily by Hawaiʻi residents, particularly those on the island of Hawaiʻi. One camera about 630 metres from a vent was buried beneath about 10 metres of spatter during episode 38 on December 6, 2025, after a shallow collapse sent a fountain toward it.

The researchers say the eruption’s outcome remains unknown. Continued monitoring may clarify how magma and gas recharge the system, how pressure changes, and how pathways within the volcano affect the fountains. For now, the reported advance is a way to identify periods when another fountain is more likely, with the precise timing and underlying gas mechanism still unresolved.