Report on Aira (Japan) — December 1981
Scientific Event Alert Network Bulletin, vol. 6, no. 12 (December 1981)
Managing Editor: Lindsay McClelland.
Aira (Japan) Notable explosions of 1981 tabulated
Please cite this report as:
Global Volcanism Program, 1981. Report on Aira (Japan) (McClelland, L., ed.). Scientific Event Alert Network Bulletin, 6:12. Smithsonian Institution.
31.593°N, 130.657°E; summit elev. 1117 m
All times are local (unless otherwise noted)
The rate of explosive activity at the summit crater of Minami-dake dropped slightly in December; 27 explosions had been recorded by the 25th. Incandescent columns 200 m high were observed for 7 seconds at 1836 on 9 December and for 5 seconds at 0622 on 22 December. Ash clouds higher than 2 km were observed on 3, 4, and 9 December.
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.