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Report on Aira (Japan) — November 1976


Natural Science Event Bulletin, vol. 1, no. 14 (November 1976)
Managing Editor: David Squires.

Aira (Japan) Frequent small explosions and earthquakes; some heavy ashfall

Please cite this report as:

Global Volcanism Program, 1976. Report on Aira (Japan) (Squires, D., ed.). Natural Science Event Bulletin, 1:14. Smithsonian Institution. https://doi.org/10.5479/si.GVP.NSEB197611-282080



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

All times are local (unless otherwise noted)

Most of the explosions 10 September-28 October were small. [Ash cloud] emission was also observed, reaching a maximum of 3000 m [above the crater]. Volcanic earthquakes were frequent. The explosion at 1142 on 10 September deposited a large quantity of ash and lapilli at Kagoshima City. The 23 September explosion at 2015 was accompanied by a large detonation, an air shock, [an incandescent column], thunder, and rumbling. A large amount of ash and lapilli were deposited on the S flank, 3 km from the crater. Activity on 2 October began at 1238 and lasted about 3 hours, causing a heavy ashfall W of the vent. A large detonation and air shock were observed at 0028 on 6 October. This explosion caused a cinder fall on the middle flank.

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.