Report on Asosan (Japan) — July 1977
Natural Science Event Bulletin, vol. 2, no. 7 (July 1977)
Managing Editor: David Squires.
Asosan (Japan) Gas and tephra emissions; several people injured
Please cite this report as:
Global Volcanism Program, 1977. Report on Asosan (Japan). In: Squires, D. (ed.), Natural Science Event Bulletin, 2:7. Smithsonian Institution. https://doi.org/10.5479/si.GVP.NSEB197707-282110.
32.884°N, 131.104°E; summit elev. 1592 m
All times are local (unless otherwise noted)
Emission of gas and tephra from the [Crater 1] of Naka-dake continued through June. Much ash and sand, and occasional fist- to hand-size cinders were ejected. Activity declined in early July, but an explosion on 20 July at 1321 sent a column of ash . . . about [1,500] m above the crater and [ejecta lightly] injured [three] persons nearby.
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 km3 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 CE. 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; T. Tiba, Nationl Science Museum; UPI.