Lava fountains exceed 300 m (1 000 feet) as new eruptive episode begins at Kīlauea’s Halemaʻumaʻu crater, Hawaiʻi

Sustained lava fountaining began at Kīlauea’s Halemaʻumaʻu crater at 16:15 HST on May 25, 2025 (02:15 UTC on May 26), marking the start of Episode 23 of the ongoing summit eruption, the U.S. Geological Survey (USGS) Hawaiian Volcano Observatory (HVO) reports.

Initial activity was observed from the north vent, where fountaining intensified rapidly, reaching heights exceeding 300 m (1 000 feet) just 30 minutes into the eruption. The south vent followed with fountains measuring up to 70 m (230 feet) by 17:15 HST.

Lava flows are currently confined to the floor of Halemaʻumaʻu crater and the southwestern part of Kaluapele, the summit caldera.

Inflationary tilt measured at Uēkahuna (UWD) station reached over 12 microradians before the onset of sustained fountaining and then transitioned abruptly to deflation. Seismic tremor began increasing at 16:36 HST at the same time that fountaining increased in height and volume.

“High levels of volcanic gas, primarily water vapor (H₂O), carbon dioxide (CO₂), and sulfur dioxide (SO₂), are the primary hazard of concern, as this hazard can have far-reaching effects downwind,” HVO volcanologists said.

As SO₂ is released from the summit and east rift eruptive vents, it reacts in the atmosphere with oxygen, sunlight, moisture, and other gases and particles and, within hours to days, converts to fine particles, which scatter sunlight, causing the visible haze that is observed downwind of Kīlauea.

Areas far downwind, like the west side of Hawaiʻi Island and other islands in the state, are mostly affected by the fine particles. However, areas closer to the eruptive vents, including the communities ranging from Ocean View to Hilo, can be exposed to both SO₂ gas and fine particles during periods of vog.

Vog exposure may worsen symptoms in individuals with pre-existing health conditions, including asthma, other respiratory diseases, and cardiovascular conditions, as well as in older adults, infants, children, and pregnant women.

Other hazards include Pele’s hair and spatter fallout near the vents and further downwind. Pele’s hair consists of fine strands of volcanic glass generated by fountaining lava. These materials can cause skin and eye irritation and may be transported over long distances depending on wind conditions.

All observed activity remains confined to a closed area within Hawaiʻi Volcanoes National Park. The Kīlauea Volcano Alert Level remains at Watch, and the Aviation Color Code is Orange.

This episode follows a pattern of episodic eruptions at the summit crater, with eruptive activity typically lasting less than one day and separated by several-day pauses.

The previous episodes have shown similar geophysical and gas emission trends.

Live views of the eruption