Fig. 7: Downslope seismic reflection SPARKER profiles collected post-collapse in August 2019.

Profiles SKC-03 (A), SKC-02 (B) and SKC-01 (C) show the emplacement of a large landslide mass on the seafloor and its incision into the seafloor. Also shown is the presence of a secondary debris flow projecting into the basin from the toe of the landslide, which has been subsequently buried by excessive post-collapse sedimentation of eruptive materials. Also shown is the projected two-way travel-time-converted level of the 1990 seafloor (based on Deplus et al.¹¹ bathymetry) to demark the sedimentation in the basin since that time. The green horizon represents the seafloor; pale blue represents the top of the landslide blocks; dark blue represents the base of the landslide blocks; pale and dark brown represents the top and base of the buried debris flows, respectively; pale and dark grey represents the top and base of older buried debris flows; and red represents potential faults. Insets represent magnified images of the toe of the landslide and debris flow and are represented in Supplementary Fig. 11.