Report on Asosan (Japan) — November 1994

Bulletin of the Global Volcanism Network, vol. 19, no. 11 (November 1994)
Managing Editor: Richard Wunderman.

Asosan (Japan) Minor phreatic activity from crater lake

Please cite this report as:

Global Volcanism Program, 1994. Report on Asosan (Japan). In: Wunderman, R (ed.), Bulletin of the Global Volcanism Network, 19:11. Smithsonian Institution. http://dx.doi.org/10.5479/si.GVP.BGVN199411-282110.

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Asosan

Japan

32.884°N, 131.104°E; summit elev. 1592 m

All times are local (unless otherwise noted)


During November, no eruptive activity took place at Crater 1. Water and gas ejection from a pool of water on the crater floor was observed on 5 days in November (specifically, 2, 3, 6, 27 and 28 November). Tremor amplitude registered at a seismic station 800 m W of the crater was not greater than 0.5 µm, but in December the amplitude began to rise.

Geologic Background. The 24-km-wide Asosan caldera was formed during four major explosive eruptions from 300,000 to 90,000 years ago. These produced voluminous pyroclastic flows that covered much of Kyushu. The last of these, the Aso-4 eruption, produced more than 600 cu km of airfall tephra and pyroclastic-flow deposits. A group of 17 central cones was constructed in the middle of the caldera, one of which, Nakadake, is one of Japan's most active volcanoes. It was the location of Japan's first documented historical eruption in 553 AD. The Nakadake complex has remained active throughout the Holocene. Several other cones have been active during the Holocene, including the Kometsuka scoria cone as recently as about 210 CE. Historical eruptions have largely consisted of basaltic to basaltic-andesite ash emission with periodic strombolian and phreatomagmatic activity. The summit crater of Nakadake is accessible by toll road and cable car, and is one of Kyushu's most popular tourist destinations.

Information Contacts: JMA.