Oct 16, 2025: South Vent Pistoning at Kilauea Volcano

USGS REPORT Oct 16: Precursory low-level activity for episode 35 of the ongoing Halemaʻumaʻu eruption increased this morning, October 16, 2025, with a series of lava overflows and drainbacks occurring from the south vent.

Seven lava overflow-drainback events occurred between 7:47 AM and 1:00 PM HST. A table of event times and durations is provided below. Each overflow produced short, channelized lava flows that flowed onto the crater floor. Each overflow event ended with lava suddenly draining back into the south vent. The drainbacks were immediately preceded by a short burst of spattering or small fountaining in the vent.

Additional overflow-drainback events are expected in the coming hours and days, possibly with increased frequency and/or duration. Similar events occurred during the days leading up to the onset of previous episodes. Approximately 100 overflow-drainback events were observed prior to episode 34 fountaining. Precursory activity prior to previous fountaining episodes has lasted from a few hours to a few days and has included eruptive vent spattering, small dome fountains, lava overflows, and lava drainbacks. Current activity therefore suggests that episode 35 fountaining is likely to begin within the next few days.

Forecast models based on the rate of summit inflation indicate that episode 35 lava fountaining is likely to begin between October 17 and 22, 2025, with the most likely dates being between October 18 and 20. The onset of episode 35 lava fountaining may occur sooner if rates of inflation and precursory activity increase.

Summary of south vent lava overflow/drainback events recorded between 7:47 a.m. and 1:00 p.m. HST, October 16:

Overflow Start time Overflow End time Duration (hr:mm)
10/16/25 7:35 AM 10/16/25 7:47 AM 0:12
10/16/25 8:50 AM 10/16/25 9:03 AM 0:13
10/16/25 9:29 AM 10/16/25 9:34 AM 0:05
10/16/25 10:47 AM 10/16/25 10:51 AM 0:04
10/16/25 11:12 AM 10/16/25 11:26 AM 0:14
10/16/25 11:54 AM 10/16/25 12:28 PM 0:34
10/16/25 12:41 AM 10/16/25 12:54 PM 0:13

As reported in this morning's Kīlauea Daily Update, nearly continuous strong glow was visible from both the north and south vents last night, indicating that magma within the conduits is close to the surface. Intermittent spattering in the north vent became visible just after dark last night. Infrequent spattering also occurred from the south vent after 10:00 p.m. HST. Seismic tremor changed from continuous to irregular gas pistoning last night. Kīlauea's summit region continued to inflate over the past 24 hours. The UWD tiltmeter shows continued inflationary tilt and has recovered more than 22 microradians since episode 34 ended. Inflation rates increased on October 15 to approximately 2 microradians per day.

At the start of previous episodes, precursory activity has rapidly escalated into sustained high fountaining over minutes to tens of minutes. During previous episodes, fountains reached heights of more than 1,000 feet (300 meters) and the eruptive plume reached heights of up to 20,000 feet (6,000 meters) above ground level soon after sustained high fountaining began.


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VolcanoDiscovery.com - Research


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Sound is not live and is recorded from a previous eruption.
Source: USGS