Report on Aira (Japan) — January 1997
Bulletin of the Global Volcanism Network, vol. 22, no. 1 (January 1997)
Managing Editor: Richard Wunderman.
Aira (Japan) Four explosive eruptions from Minami-dake in December and January
Please cite this report as:
Global Volcanism Program, 1997. Report on Aira (Japan). In: Wunderman, R. (ed.), Bulletin of the Global Volcanism Network, 22:1. Smithsonian Institution. https://doi.org/10.5479/si.GVP.BGVN199701-282080.
31.593°N, 130.657°E; summit elev. 1117 m
All times are local (unless otherwise noted)
During December and January, Minami-dake crater had six eruptions (four explosive). At a seismic station 2.3 km NW of Minami-dake crater, 342 earthquakes and 14 tremors were recorded in December, and 257 earthquakes and 18 tremors were recorded in January. The highest plume in December rose to a height of 2,700 m. The monthly ashfall measured at the Kagoshima Local Meteorological Observatory (KMO), 10 km W from the crater, was 14 g/m2.
On 14 December, bombs and lapilli were ejected and deposited on the flanks. A small quantity of ashfall was observed at Aburatsu and Miyako-no-jo. During the eruption, 14 lightning strikes occurred during a 10-second interval. January's only eruption produced <1 g/m2 of ashfall at KMO.
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: Volcanological Division, Japan Meteorological Agency (JMA), 1-3-4 Ote-machi, Chiyoda-ku, Tokyo 100, Japan.