Report on Kirishimayama (Japan) — 18 April-24 April 2018
Smithsonian / US Geological Survey Weekly Volcanic Activity Report, 18 April-24 April 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, 18 April-24 April 2018. Smithsonian Institution and US Geological Survey.
31.934°N, 130.862°E; summit elev. 1700 m
All times are local (unless otherwise noted)
An explosive eruption at Iwo-yama (also called Ioyama, NW flank of Karakuni-dake), a stratovolcano of the Kirishimayama volcano group, occurred at 1555 on 19 April prompting JMA to raise the Alert Level to 3 (on a scale of 1-5). This was the first eruption in that area since 1768; frequent and recent activity has occurred from Shinmoedake (Shinmoe peak). Ash plumes rose as high as 500 m above new vents in the SE part of the crater, and a large amount of ejected tephra including boulders were deposited around the crater area. Webcams showed expansion of vents by 2100. A new fumarole was observed at 1630 on 20 April in the vicinity of the highway, on the W side of Iwo-yama. During overflights on 20 and 21 April scientists observed multiple vents with fumarolic emissions, and intermittent ejections of black-gray muddy water. The activity continued through 23 April.
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.