Report on Kikai (Japan) — 25 July-31 July 2001
Smithsonian / US Geological Survey Weekly Volcanic Activity Report, 25 July-31 July 2001
Managing Editor: Gari Mayberry
Please cite this report as:
Global Volcanism Program, 2001. Report on Kikai (Japan). In: Mayberry, G (ed.), Weekly Volcanic Activity Report, 25 July-31 July 2001. Smithsonian Institution and US Geological Survey.
30.793°N, 130.305°E; summit elev. 704 m
All times are local (unless otherwise noted)
Continuous volcanic tremor was recorded at Satsuma-Iwo-jima during 20 to at least 23 July. A seismometer about 700 m SW of Iwo-dake crater recorded 50-100 earthquakes daily, in comparison to 30-90 earthquakes recorded daily during December 2000 and March 2001. Small amounts of volcanic tremor were also occasionally recorded. The Iwo-jima Branch of the Mishima Village Office reported that ash fell during 19-21 July. Faint ashfall and small volcanic tremor had occurred since December 2000.
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.