Report on Kikai (Japan) — 14 March-20 March 2018
Smithsonian / US Geological Survey Weekly Volcanic Activity Report, 14 March-20 March 2018
Managing Editor: Sally Kuhn Sennert
Please cite this report as:
Global Volcanism Program, 2018. Report on Kikai (Japan). In: Sennert, S K (ed.), Weekly Volcanic Activity Report, 14 March-20 March 2018. Smithsonian Institution and US Geological Survey.
30.793°N, 130.305°E; summit elev. 704 m
All times are local (unless otherwise noted)
JMA reported that one small-amplitude, short-duration volcanic tremor was detected on 16 March at Satsuma Iwo-jima, a subaerial part of Kikai’s NW caldera rim. The number of volcanic earthquakes increased on 19 March, prompting JMA to raise the Alert Level to 2 (on a 5-level scale), and then decreased the next day. The report noted increased thermal activity since February, with occasional visual observations of incandescence.
Geologic Background. Kikai is a mostly submerged, 19-km-wide caldera near the northern end of the Ryukyu Islands south of Kyushu. Kikai was the source of one of the world's largest Holocene eruptions about 6300 years ago. Rhyolitic pyroclastic flows traveled across the sea for a total distance of 100 km to southern Kyushu, and ashfall reached the northern Japanese island of Hokkaido. The eruption devastated southern and central Kyushu, which remained uninhabited for several centuries. Post-caldera eruptions formed Iodake lava dome and Inamuradake scoria cone, as well as submarine lava domes. Historical eruptions have occurred in the 20th century at or near Satsuma-Iojima (also known as Tokara-Iojima), a small 3 x 6 km island forming part of the NW caldera rim. Showa-Iojima lava dome (also known as Iojima-Shinto), a small island 2 km east of Tokara-Iojima, was formed during submarine eruptions in 1934 and 1935. Mild-to-moderate explosive eruptions have occurred during the past few decades from Iodake, a rhyolitic lava dome at the eastern end of Tokara-Iojima.