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Report on Aira (Japan) — May 1990


Aira

Bulletin of the Global Volcanism Network, vol. 15, no. 5 (May 1990)
Managing Editor: Lindsay McClelland.

Aira (Japan) Explosions and ash emissions, structural damage

Please cite this report as:

Global Volcanism Program, 1990. Report on Aira (Japan) (McClelland, L., ed.). Bulletin of the Global Volcanism Network, 15:5. Smithsonian Institution. https://doi.org/10.5479/si.GVP.BGVN199005-282080



Aira

Japan

31.5772°N, 130.6589°E; summit elev. 1117 m

All times are local (unless otherwise noted)


Explosions have been frequent since October 1989 . . . after 1 year of weaker activity. There were five recorded explosions in March, 12 in April, and 19 in May for a total of 64 in 1990. Ash clouds rose 1-3 km during larger explosions. An air shock from one explosion broke 21 windowpanes on the island and in the city of Kagoshima . . . . This was the first damage from explosions since January 1989. Monthly ash accumulations at the observatory were 457 g/m2 in March, 291 g/m2 in April, and 447 g/m2 in May.

Geological Summary. The Aira caldera in the northern half of Kagoshima Bay contains the post-caldera Sakurajima volcano, one of Japan's most active. Eruption of the voluminous Ito pyroclastic flow accompanied formation of the 17 x 23 km caldera about 22,000 years ago. The smaller Wakamiko caldera was formed during the early Holocene in the NE corner of the caldera, along with several post-caldera cones. The construction of Sakurajima began about 13,000 years ago on the southern rim and built an island that was joined to the Osumi Peninsula during the major explosive and effusive eruption of 1914. Activity at the Kitadake summit cone ended about 4,850 years ago, after which eruptions took place at Minamidake. Frequent eruptions since the 8th century have deposited ash on the city of Kagoshima, located across Kagoshima Bay only 8 km from the summit. The largest recorded eruption took place during 1471-76.

Information Contacts: JMA.