Report on Aira (Japan) — October 1981
Scientific Event Alert Network Bulletin, vol. 6, no. 10 (October 1981)
Managing Editor: Lindsay McClelland.
Aira (Japan) Frequent explosions, two incandescent columns
Please cite this report as:
Global Volcanism Program, 1981. Report on Aira (Japan) (McClelland, L., ed.). Scientific Event Alert Network Bulletin, 6:10. Smithsonian Institution.
31.593°N, 130.657°E; summit elev. 1117 m
All times are local (unless otherwise noted)
Frequent explosions continued through October, when 35 were recorded. Two 100-m-high incandescent columns were recorded for 3 seconds at 0444 on 2 October. Ash clouds higher than 2 km above the summit were observed on 3, 17 and 31 October.
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.