Seismic characterization of pre- and post-fountaining phenomena during the 2024-2026 Kīlauea eruption sequence

The ongoing (2024-) eruption sequence at Kīlauea Volcano, Hawai’i, has comprised 40 (as of mid-January, 2026) episodes of high fire fountaining, as well as episodes of dome fountaining, effusive eruption, and gas pistoning (series of cyclical overflows and drain-back of lava). While many episodes of gas pistoning are visually apparent in webcam footage, seismic characterization of gas pistoning and VLP swarms allows for an objective analysis of pistoning frequency, amplitude, and duration, providing greater insight into the gas ascent and escape process and its relationship to fire fountaining episodes. We thus analyze continuous RSAM to quantify the timing, duration, frequency, and amplitude of gas pistoning throughout the 2024-2026 eruption sequence and its relationship to fire fountain heights and durations.

 

Gas pistoning was first observed in March of 2025 as an immediate precursor to fire fountaining, and post-March fire fountains have generally been preceded by gas pistoning. The onset of precursory gas pistoning corresponds to a shift to shorter-lived fire fountains, suggesting that precursory gas pistoning contributes to the duration of fire fountain episodes. However, beginning in late May, gas pistoning became more decoupled from high fountaining, with a marked delay between the end of gas pistoning and the high fountain onset. The fountains that follow a delay after pistoning are among the highest in the eruption sequence, suggesting that a short-term sealing of gas pathways contributes to greater fountain heights. The most recent (November 2025 onwards) episodes of fire fountaining have also been followed by swarms of repeating VLP events or by additional gas-pistoning tremor, suggesting ongoing gas escape following the end of high fire fountaining. Overall, seismic observations indicating increased precursory and post-fountaining degassing suggest increasing degrees of vertical connectivity in Kīlauea’s magma transport system.