Hawaiian Volcano Update: Kīlauea Summit Eruption’s Episode 33; Pohoiki Bay Dredge Update - September 25, 2025
Following precursory activity starting on Wednesday, September 17, episode 33 of Kīlauea’s ongoing summit eruption began overnight early on Friday, September 19 and lasted about 9 hours, ending at 12:08 pm. Lava fountaining from the north vent reached heights estimated up to 800 feet or 240 meters, as the fountain was only slightly inclined from vertical at 60 degrees, much less than the 30 to 45 degrees of episodes 31 and 32. These tallest fountains since July’s episode 28 peaked above the caldera and produced lava flows that covered about two-thirds of Halemaʻumaʻu crater floor. The south vent was only intermittently active with low outbursts that ended by 6 am. A slightly lesser volume of 6.3 million cubic meters were erupted overall, the result of a similarly high discharge rate to other recent episodes but over a lesser amount of time.
Gas emissions from episode 33 once again reached above Mauna Loa’s crater rim near 14,000 feet elevation, with lower atmosphere emissions blowing with the trade winds to the southwest into the closed areas of Hawaiʻi Volcanoes National Park and the Kaʻū Desert. Passive degassing of the vents in the days since produces less, but still considerable, amounts of vog which this week are blowing with variable winds into nearby communities. As with every summit eruption in the last 5 years, vog and tephra are currently the most common hazards for island residents and visitors. 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. A magnitude 3.6 earthquake on the south flank today serves as a reminder that other parts of the volcano continue to move and will eventually change the dynamics of the current episodic eruption. For now, Kīlauea’s landmark summit eruption is expected to continue after another pause, with monitoring signals and models projecting September 28 to October 1 as the likely window for episode 34.
Maunaloa continues to inflate its established post-eruption pattern, with localized adjustments 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. We also provide an update on the dredging of Pohoiki bay of the sediment generated in the 2018 eruption which up until this week fully blocked the culturally and economically significant boat ramp from the ocean.
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