Fig. 3

Snapshots of the volcanic plumes and PDCs from the monitoring camera located 3 km NW of Shindake operated by Japan Meteorological Agency A–F and distribution of PDCs (G, H). A White volcanic plume during Phase 1. B Colored volcanic plumes during Phase 2. C Colored volcanic plumes during Phase 3. D The explosive activity at 18 December 2018 (Phase 4). The front of the PDC can be recognized at the foot of the eruption column. E Volcanic glow observed by high-sensitivity monitoring camera during the night of 18 December 2018, after a PDC occurred (20:55′19″ JST). F Second PDC occurred on 17 January 2019 (Phase 4). G, H Orange colored area indicates distribution of PDCs on 18 December 2018 G and 17 January 2019 (H)