Hawaiian Volcano Update: Kīlauea Summit Eruption’s Episode 31 & Inclined Fountain - August 28, 2025

Episode 31 of Kīlauea’s ongoing summit eruption began in full force around 2pm last Friday, August 22nd, enduring for over 12 hours. Although fountains did not exceed 325 feet or 100 meters in height, this was largely because lava was shot out of the north vent in a near-horizontal arc for over 1000 feet or 300 meters, or it would likely have exceeded 500 feet or 150 meters had it erupted straight up. Roughly 8.4 million cubic meters of lava were erupted that covered more than 75% of Halemaʻumaʻu crater floor, the third largest volume of any episode over the full 8 months of current activity. This means that despite an emerging pattern of longer pauses between episodes, the average filling rate of the crater has not slowed.

For the second straight episode, new vents opened during the vigorous phase of fountaining, this time in an area between and above the north and south vents. At the “intermediate vents”, lava emerged from cracks in the cinder and spatter cone around a recently glowing area around 7:23 pm, about 3 hours after the south vent activated with 30-foot or 10-meter high fountains feeding a smaller trickle of lava. The intermediate vents grew to 100 feet or 30 meters in height by evening, also feeding a lava flow that joined the larger mass engulfing the crater floor.

Despite a lower and inclined fountain, gas emissions once again shot upwards through the atmosphere as well as downwind, mostly impacting the nearby and closed areas of Hawaiʻi Volcanoes National Park but also adding to the wider atmospheric load. As with every summit eruption in the last 5 years, vog and tephra remain the most common hazards for island residents, and the usual precautions and preparations apply, especially for those with respiratory sensitivities – more information at https://vog.ivhhn.org/. All eruptive activity has been confined to Kīlauea’s summit caldera within Hawaiʻi Volcanoes National Park, with no increased lava threat to people. There continue to be no significant changes on either of Kīlauea’s rift zones.

Maunaloa continues to inflate its established post-eruption pattern, with localized adjustments increasingly evident on monitoring instruments in recent weeks, perhaps coincident with pressure changes at Kīlauea. As usual, we summarize the monitoring signals, imagery, and reports available courtesy of the USGS Hawaiian Volcano Observatory, annotating the presentation on screen as we go and discussing live viewer questions. 

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