Fig. 6

Cascade of precursors leading up to the 22 December 2018 sector collapse event. a Precursors include flank motion (white arrow), eruptions (represented as eruption cloud), and increasing eruptive deposits (red shaded areas) as assessed by satellite data (thermal, InSAR). A décollement (black line beneath the island) dips SW, but faulting had not yet breached the surface. Approximately 2 mins before the collapse, a seismic event was recorded (shown by seismic trace symbol). b The landslide collapse along a failure plane (black curved line beneath island) showed a 1–2-min-long low-frequency signal (seismic waveform). Infrasound instruments (speaker symbol) measured the collapse before the tsunami waves arrived. The collapse decapitated the island (gray shaded area). The tsunami (blue wave) caused damage and loss along the coast. c Postcollapse volcanic explosions occurred coincident with increased degassing (gray plume) caused by unloading (arrow symbol); the old topography is indicated (black dashed line). New eruptive deposits increased the island area (red shaded areas). Finally, rapid erosion deeply carved incisions into the fresh eruption deposits