Report on Unzendake (Japan) — May 1996
Bulletin of the Global Volcanism Network, vol. 21, no. 5 (May 1996)
Managing Editor: Richard Wunderman.
Unzendake (Japan) Partial dome collapse triggers a pyroclastic flow
Please cite this report as:
Global Volcanism Program, 1996. Report on Unzendake (Japan) (Wunderman, R., ed.). Bulletin of the Global Volcanism Network, 21:5. Smithsonian Institution. https://doi.org/10.5479/si.GVP.BGVN199605-282100.
32.761°N, 130.299°E; summit elev. 1483 m
All times are local (unless otherwise noted)
On 1 May a pyroclastic flow was triggered by the partial collapse of an unstable lava dome. Dome collapse causing pyroclastic flows was a common occurrence during the 1990-1995 eruption. Pyroclastic flows began again in February, and tremor was recorded in March. The large Unzen volcanic complex covers much of the Shimabara Peninsula E of Nagasaki. Mayu-yama lava dome was the source of a devastating 1792 avalanche and tsunami.
Geologic Background. The massive Unzendake volcanic complex comprises much of the Shimabara Peninsula east of the city of Nagasaki. An E-W graben, 30-40 km long, extends across the peninsula. Three large stratovolcanoes with complex structures, Kinugasa on the north, Fugen-dake at the east-center, and Kusenbu on the south, form topographic highs on the broad peninsula. Fugendake and Mayuyama volcanoes in the east-central portion of the andesitic-to-dacitic volcanic complex have been active during the Holocene. The Mayuyama lava dome complex, located along the eastern coast west of Shimabara City, formed about 4000 years ago and was the source of a devastating 1792 CE debris avalanche and tsunami. Historical eruptive activity has been restricted to the summit and flanks of Fugendake. The latest activity during 1990-95 formed a lava dome at the summit, accompanied by pyroclastic flows that caused fatalities and damaged populated areas near Shimabara City.
Information Contacts: Japan Meteorological Agency (JMA), Volcanological Division, Seismological and Volcanological Department, 1-3-4 Ote-machi, Chiyoda-ku, Tokyo 100, Japan.