Kīlauea summit deflation stalls lava-fountaining buildup, scientists push forecast window

The Halemaʻumaʻu summit eruption of Kīlauea remains paused following the end of episode 42 at 11:38 p.m. HST on Feb. 15, and preliminary models from the U.S. Geological Survey’s Hawaiian Volcano Observatory now put the most likely onset of episode 43 between March 6 and March 16, 2026. HVO cautions that short periods of weak summit deflation or no inflation have interrupted the expected inflationary trend and increased uncertainty in the forecast.

Summit deformation shows mixed signals from HVO’s tiltmeters. As of HVO’s morning update reported by Big Island Video News on Feb. 23, the UWD tiltmeter had recorded nearly 13.4 microradians of inflationary recovery since the end of episode 42, with a loss of about 0.6 microradians over the previous 24 hours. HVO’s Feb. 27 daily update reported the UWD tiltmeter had recorded recovery of nearly 17.6 microradians since episode 42, with about 0.2 microradians of net deflation over the past 24 hours. HVO notes that the overall inflationary trend “has been interrupted by periods of no inflation or slight deflation recorded across all four summit tiltmeters that may impact the onset of episode 43 fountaining.”

Visual and seismic monitoring at the summit reinforce the cautious outlook. HVO reported that “little-to-no glow could be seen from the vents last night” and that “this morning, both vents remain quiet and emitting steady gas plumes.” Seismically, HVO recorded low continuous tremor punctuated by more energetic bursts every 5-10 minutes, and there were two earthquakes less than M1.0 located in the summit region in the past 24 hours.

Local reporting and HVO updates have moved the forecast window as the deformation record evolves. Big Island Video News summarized HVO language by saying “Geologists have pushed the forecast window for the onset of episode 43 lava fountaining back to March 6th through March 16th” and added that “another deflationary event took place in the past 24 hours moving the forecast window back by a day.” HVO’s own analysis states that “periods of weak deflation or no inflation have not been common in the early stages of repose between fountaining episodes. These changes in tilt rate are not predictable and create uncertainty in modeling the onset of episode 43 fountaining.”

The apparent discrepancy between the UWD totals reported on Feb. 23 and Feb. 27 reflects different measurement snapshots rather than conflicting science: the 13.4 microradian figure cited by BIVN reflects the earlier Feb. 23 update, while HVO’s Feb. 27 daily update reports the larger 17.6 microradian recovery through Feb. 27. HVO emphasizes that “additional data are needed to more accurately determine the forecast window,” leaving March 6–16 as the working bracket for episode 43 until new tilt, seismic and gas observations clarify whether the summit will rebuild into another lava-fountaining episode.