Record lava fountains reach 460 m (1 500 feet) during episode 35 of Kīlauea summit eruption, Hawai‘i
Episode 35 of the ongoing Halemaʻumaʻu eruption at Kīlauea volcano began at 20:05 HST on October 17, 2025 (06:05 UTC on October 18), producing simultaneous fountains from the north and south vents that reached record heights of approximately 460 m (1 500 feet). The eruption cloud rose above 6 000 m (20 000 feet) while lava flows remained contained within the crater.
Lava fountaining at Kilauea volcano, Hawaii at 22:33 HST on October 17, 2025. Credit: USGS/HVO
The Hawaiian Volcano Observatory (HVO) reported that episode 35 of the ongoing Halemaʻumaʻu eruption began at approximately 20:05 HST on October 17 (06:05 UTC on October 18).
Precursory overflow and drainback activity that started at 19:28 HST rapidly evolved into vigorous fountaining from the north vent, followed minutes later by a second vent to the south. Within two hours, both vents were producing simultaneous fountains exceeding 300 m (1 000 feet), reaching peak heights of about 460 m (1 500 feet).
This marked the highest observed height since the eruption began in December 2024.
At 21:10 HST, the eruption cloud above the dual fountains rose over 5 000 m (16 000 feet) above ground level, extending to approximately 6 000 m (20 000 feet) in total elevation. By 21:30 HST, the south vent had reached 400 m (1 300 feet) while the north vent produced fountains of about 330 m (1 100 feet). The final USGS message of the night, issued at 22:11 HST, confirmed record fountaining for the current eruption cycle.
According to HVO’s daily update on October 17, the volcano remains at Alert Level WATCH and Aviation Color Code ORANGE.
Continuous tremor and summit inflation preceding the event indicated that magma was present at shallow levels beneath both vents. In the 24 hours prior to the eruption, the Uwekahuna (UWD) tiltmeter recorded 23 microradians of inflation, similar to the pressurization that preceded episode 34 on October 1, which produced fountains up to 400 m (1 300 feet).
During episode 34, HVO estimated an erupted volume of approximately 9 million m³ (2.5 billion gallons) and maximum effusion rates near 380 m³/s (500 yd³/s). Episode 35 is expected to produce comparable or greater volumes, although measurements are still in progress.
As in previous cycles, lava flows remain confined to the floor of Halemaʻumaʻu crater, within the summit caldera (Kaluapele), and do not pose a threat to nearby communities.
The ongoing eruption sequence, active since December 23, 2024, is characterized by short-lived but intense episodes of fountaining separated by pauses lasting several days to a week. Each episode is accompanied by rapid deflation of the summit region followed by steady reinflation as the magma chamber repressurizes.
HVO scientists note that this pattern closely resembles the episodic fountaining behavior of the 1983–86 Puʻuʻōʻō eruption on Kīlauea’s East Rift Zone.
Average sulfur dioxide (SO2) emissions during pauses are about 1 200–1 500 tonnes per day, with short-term bursts during active fountaining. Elevated gas output contributes to the formation of vog (volcanic smog) that can drift downwind across the island. Strands of volcanic glass known as Pele’s hair have been observed across the summit region and can be transported more than 15 km (10 miles) from the vent depending on wind conditions.
Authorities warn that Pele’s hair and other fine tephra fragments may cause skin or eye irritation and contaminate water catchment systems. Hawai‘i Volcanoes National Park remains open with restricted access to areas near the summit due to crater wall instability, ground cracking, and the potential for rockfalls triggered by seismic activity.
As of early October 18 (UTC), HVO reports continued strong tremor and high radiant output from both vents visible on summit webcams and livestreams. Monitoring instruments indicate ongoing magma supply to the shallow reservoir beneath Halemaʻumaʻu. Additional episodic activity is likely as summit inflation continues.
References:
1 Kilauea volcano update – USGS/HVO – October 17, 2025
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