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Report on Aira (Japan) — November 1981


Scientific Event Alert Network Bulletin, vol. 6, no. 11 (November 1981)
Managing Editor: Lindsay McClelland.

Aira (Japan) More frequent explosions; tephra breaks windshields

Please cite this report as:

Global Volcanism Program, 1981. Report on Aira (Japan) (McClelland, L., ed.). Scientific Event Alert Network Bulletin, 6:11. Smithsonian Institution. https://doi.org/10.5479/si.GVP.SEAN198111-282080



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

All times are local (unless otherwise noted)

Eruptive activity intensified in November. Explosions became more frequent and stronger; 50 were recorded. The explosion rate had been about 35/month August-September, but fewer than 4/month April-July. An explosion at 1528 on 16 November ejected incandescent tephra that caused [grass fires] on the SW flank. The [eruption] column rose 3 km, the greatest height this year. Lapilli from an explosion at 1322 on 21 November broke windshields on a few cars passing 3 km S of the summit crater of Minami-dake. Incandescent columns were observed on several occasions: 100 m high for 5 seconds on 7 and 22 November, and for 3 seconds on 14 and 29 November; 200 m high for 3 seconds on 30 November.

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, Tokyo.