Report on Aira (Japan) — January 1978
Scientific Event Alert Network Bulletin, vol. 3, no. 1 (January 1978)
Managing Editor: David Squires.
Aira (Japan) Strong explosive activity in December and January
Please cite this report as:
Global Volcanism Program, 1978. Report on Aira (Japan). In: Squires, D. (ed.), Scientific Event Alert Network Bulletin, 3:1. Smithsonian Institution. https://doi.org/10.5479/si.GVP.SEAN197801-282080.
31.593°N, 130.657°E; summit elev. 1117 m
All times are local (unless otherwise noted)
Tephra from explosions at 1220 on 8 December, 1834 on 20 December, 0621 and 1507 on 22 December, and on 27 January, caused [grass] fires. A 300-m column of incandescent ejecta was observed at 0534 on l December, and reflected glow was seen between 0322 and 0325 on 10 December. The air shock from an explosion at 2140 on 8 December broke three [windowpanes] in a nearby village. Ash clouds rose 2,000 m above the crater on 6, 8, and 22 December.
Geologic Background. 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.