Kilauea summit showing strong gas pistoning and overflows ahead of next eruptive episode, Hawaii

The Hawaiian Volcano Observatory (HVO) reports that summit inflation at Kiluea volcano is continuing, with the Uēkahuna tiltmeter recording approximately 21.3 microradians of inflationary tilt since episode 32 ended. G

Glow in both north and south vents has been visible overnight, and gas pistoning cycles have caused multiple small overflows from the north vent. Intermittent glow at the south vent indicates similar activity there.

At 09:23 UTC on September 18 (23:23 HST on September 17), dome fountains 3–6 m (10–20 feet) high were observed as the north vent began vigorously overflowing. Earlier in the evening, large piston events sent spatter up to 4.5–9 m (15–30 feet) onto the outside of the north cone. HVO considers these as part of the precursory activity marking the transition toward episode 33.

Average sulfur dioxide (SO₂) emissions during inter-episode pauses remain elevated at 1 200–1 500 t/d, though short-term fluctuations are closely tied to gas pistoning cycles. Volcanic gas emissions continue to create vog (volcanic smog) that can be transported downwind, with potential health impacts in nearby communities.

Strands of volcanic glass, known as Pele’s hair, have been reported throughout the summit area and surrounding communities. Pele’s hair can be carried well over 15 km (10 miles) from eruptive vents and may be remobilized by wind after deposition.

It’s important to remember that contact with these sharp glass fibers can cause skin and eye irritation and contaminate catchment water supplies.

Other volcanic fragments, including pumice, scoria, and reticulite, may fall on the ground within 1–3 km (1–2 miles) of the vents. Highway 11 west of Hawai‘i Volcanoes National Park has at times been affected by fallout, depending on wind and eruption conditions.

Additional hazards include caldera wall instability, ground cracking, and rockfalls around Halemaʻumaʻu crater, hazards that have kept the summit area closed to the public since 2007.

Seismicity and ground deformation remain very low in the East Rift Zone and Southwest Rift Zone, with no significant earthquake activity outside the summit in the past 24 hours. Sulfur dioxide emissions from these zones remain below detection limits.

Tiltmeter data and the observed vigor of gas pistoning indicate that episode 33 lava fountaining remains likely to begin between today and 20 if current inflation trends persist. Each episodic event of this eruption has been accompanied by summit deflation, followed by rapid reinflation during pauses as the magma chamber recharges.

The ongoing eruption, which began on December 23, 2024, has been characterized by episodic lava fountains not seen at Kīlauea since the early phase of the Puʻuʻōʻō eruption between 1983 and 1986. Each fountaining episode has lasted from hours to more than a week, with pauses typically around one week long.

References:

¹ Hawaiian Volcano Observatory Daily Update – USGS/HVO – September 17, 2025

² Kīlauea Volcano Messages – USGS/HVO – September 17/18, 2025.

Teo Blašković

I'm a dedicated researcher, journalist, and editor at The Watchers. With over 20 years of experience in the media industry, I specialize in hard science news, focusing on extreme weather, seismic and volcanic activity, space weather, and astronomy, including near-Earth objects and planetary defense strategies. You can reach me at teo /at/ watchers.news.

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