Report on Aira (Japan) — June 1991
Bulletin of the Global Volcanism Network, vol. 16, no. 6 (June 1991)
Managing Editor: Lindsay McClelland.
Aira (Japan) Explosions remain frequent; tephra from one explosion damages houses and cars
Please cite this report as:
Global Volcanism Program, 1991. Report on Aira (Japan). In: McClelland, L. (ed.), Bulletin of the Global Volcanism Network, 16:6. Smithsonian Institution. https://doi.org/10.5479/si.GVP.BGVN199106-282080.
31.593°N, 130.657°E; summit elev. 1117 m
All times are local (unless otherwise noted)
Frequent explosive activity . . . continued through mid-July. Explosions . . . occurred 31 times in June . . . and 15 times by 24 July, bringing the year's total to 168. An explosion at 2345 on 29 June ejected blocks and lapilli that damaged house roofs and two car windshields, the second episode of explosion-related damage in 1991. The ash cloud rose to a maximum height of 3,200 m (on 27 June), and a monthly total of 20 g/m2 of ash was deposited 10 km W of the crater (compared to 209 g/m2 in May). Volcanic earthquake swarms, similar to previous months, were recorded on 7, 16, 24, and 28 June.
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.