Report on Aira (Japan) — December 1979
Scientific Event Alert Network Bulletin, vol. 4, no. 12 (December 1979)
Managing Editor: David Squires.
Aira (Japan) Frequent explosions continue; tephra cracks another airplane windshield
Please cite this report as:
Global Volcanism Program, 1979. Report on Aira (Japan) (Squires, D., ed.). Scientific Event Alert Network Bulletin, 4:12. Smithsonian Institution.
31.593°N, 130.657°E; summit elev. 1117 m
All times are local (unless otherwise noted)
Frequent explosions and ejections of dense ash clouds continued through December. Between 28 November and 28 December, 36 explosions were recorded at the JMA's Kagoshima Observatory. The 110-day explosion-free period of 1 May-18 August dropped the number of recorded explosions in 1979 to , from 231 in 1978 and 223 in 1977. However, the monthly totals for October-December 1979 are higher than the 1977-78 averages.
The windshield of a domestic YS-11 airliner was cracked by tephra at 1.5 km altitude at 1749 on 24 December, 9 minutes after an explosion from Sakura-jima. The plane landed safely at Kagoshima airport 7 minutes later.
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.