Fig. 2

Snapshots of the PDC from the monitoring camera located 3 km NW of Shindake operated by Japan Meteorological Agency (A–D). Location of the camera is shown in Fig. 1. A 10 s after the onset of the eruption (9:59′49″). Pyroclastic materials ejected as jet and form rising eruption column. B 20 s after the onset of the eruption (9:59′59″). A part of the eruption column is collapsing (a). The front of the PDC can be recognized at the foot of the eruption column (b). C 30 s after the onset of the eruption (10:00′09″). The migrating front of PDC is indicated by arrows (b). D 75 s after the onset of the eruption (10:00′52″). The front of PDC (b) reached the beach of Mukaehama