Hawaiian Volcano Update: Reviewing 1 Year of Kīlauea Summit Episodic Fountains - December 18, 2025
12 days have passed since episode 38 of Kīlauea’s ongoing, but currently paused, summit eruption. USGS-HVO models based on monitoring signals suggest episode 39 is most likely to arrive between December 22 and 27, although gas emissions are already elevated more than twice their typical inter-episode rate (3,400 vs 1,200-1,500 tonnes of SO2 per day). Combined with sometimes dominant Kona winds, gas emissions ahead of and during episode 39, plus tephra fallout including Pele’s hair and reticulite, remain the largest volcanic hazard to people and property this holiday season. 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.
Almost one year of summit eruption, from December 23, 2024 to December 11, 2025, has produced 52.7 billion gallons or 199.7 million cubic meters of lava, filling the crater area of 1.5 square miles or 3.9 square kilometers by an average of 223 feet or 68 meters. That is more lava than during the past 5 summit eruptions from 2020 to 2023 combined, telling of the high effusion rate, averaging 8.5 cubic yards or 6.5 cubic meters every second of the past almost-a-year. In a given instant, fountains ejected up to 1,300 cubic yards or 1,000 cubic meters of lava per second. 13 lava fountains reached at least 1,000 feet or 300 meters high, with the record of 1,500 feet or 450 meters high during episode 35 in mid-October, and of 0.4 miles or 0.65 kilometers laterally to the crater rim during episode 38 in early December. A laser rangefinder and 5 USGS-HVO webcams have been damaged or destroyed by falling lava: F1, KW, B2, V3 & S2. As a special wrap-up this week before our holiday break, we review eruption footage from all webcams through the 38 episodes thus far.
Maunaloa over the past year largely continued its long-term post-eruption filling pattern, with the caldera slowly stretching and rising, accompanied by earthquakes. A recent spike in seismicity was coincident with a contraction and sagging of the summit, suggesting episodic flank adjustments may become more common. Such variations have been common in the past, and don’t affect the long-term prognosis of the volcano slowly continuing to recharge its magma, eventually leading to future activity. Already the quakes have returned to background levels according to the USGS-HVO monthly update. 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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