Report on Kirishimayama (Japan) — 21 March-27 March 2018
Smithsonian / US Geological Survey Weekly Volcanic Activity Report, 21 March-27 March 2018
Managing Editor: Sally Kuhn Sennert
Please cite this report as:
Global Volcanism Program, 2018. Report on Kirishimayama (Japan). In: Sennert, S K (ed.), Weekly Volcanic Activity Report, 21 March-27 March 2018. Smithsonian Institution and US Geological Survey.
31.934°N, 130.862°E; summit elev. 1700 m
All times are local (unless otherwise noted)
JMA reported that the eruption at Shinmoedake (Shinmoe peak), a stratovolcano of the Kirishimayama volcano group, continued during 19-27 March. Lava effusion possibly stopped on 9 March, though the lava flow on the NW flank continued to advance. A high number of volcanic earthquakes continued to be recorded, in addition to many low-frequency earthquakes with shallow hypocenters. Short-duration volcanic tremor was occasionally recorded. During a field survey on 22 March scientists measured 600 tons/day of sulfur dioxide gas, and noted that the crack on the W flank had grown slightly larger. On 25 March an explosion at 0735 was followed by an ash plume that rose 3.2 km above the crater rim and ejected material as far as 800 m. An event at 0845 generated an ash plume that rose 2.1 km above the crater rim, and a very small pyroclastic flow that traveled 800 m W. Sulfur dioxide emissions were 300 tons/day on 24 March. The Alert Level remained at 3 (on a scale of 1-5).
Geologic Background. Kirishimayama is a large group of more than 20 Quaternary volcanoes located north of Kagoshima Bay. The late-Pleistocene to Holocene dominantly andesitic group consists of stratovolcanoes, pyroclastic cones, maars, and underlying shield volcanoes located over an area of 20 x 30 km. The larger stratovolcanoes are scattered throughout the field, with the centrally located Karakunidake being the highest. Onamiike and Miike, the two largest maars, are located SW of Karakunidake and at its far eastern end, respectively. Holocene eruptions have been concentrated along an E-W line of vents from Miike to Ohachi, and at Shinmoedake to the NE. Frequent small-to-moderate explosive eruptions have been recorded since the 8th century.