Report on Aira (Japan) — May 1981
Scientific Event Alert Network Bulletin, vol. 6, no. 5 (May 1981)
Managing Editor: Lindsay McClelland.
Aira (Japan) Explosions; ash ejection: B-type earthquakes
Please cite this report as:
Global Volcanism Program, 1981. Report on Aira (Japan) (McClelland, L., ed.). Scientific Event Alert Network Bulletin, 6:5. Smithsonian Institution. https://doi.org/10.5479/si.GVP.SEAN198105-282080
31.593°N, 130.657°E; summit elev. 1117 m
All times are local (unless otherwise noted)
After only two explosions from the summit crater of Minami-dake had occurred in April, none were recorded in May until the 18th. As of 28 May, four explosions had occurred. The largest produced a 1.2-km-high ash cloud on the 24th. Although explosive activity was limited in April and May, there was continued ash ejection during which explosions were not registered at the JMA's Kagoshima Observatory. Bursts of B-type earthquakes were recorded on 3, 5, 18, and 19 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 Aira caldera, along with several post-caldera cones. The construction of Sakurajima began about 13,000 years ago on the southern rim of Aira caldera and built an island that was finally joined to the Osumi Peninsula during the major explosive and effusive eruption of 1914. Activity at the Kitadake summit cone ended about 4850 years ago, after which eruptions took place at Minamidake. Frequent historical eruptions, recorded since the 8th century, have deposited ash on Kagoshima, one of Kyushu's largest cities, located across Kagoshima Bay only 8 km from the summit. The largest historical eruption took place during 1471-76.
Information Contacts: JMA, Tokyo.