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Report on Aira (Japan) — February 1977


Natural Science Event Bulletin, vol. 2, no. 2 (February 1977)
Managing Editor: David Squires.

Aira (Japan) Summit explosions continue; lapilli-fall breaks car windows

Please cite this report as:

Global Volcanism Program, 1977. Report on Aira (Japan) (Squires, D., ed.). Natural Science Event Bulletin, 2:2. Smithsonian Institution. https://doi.org/10.5479/si.GVP.NSEB197702-282080



31.593°N, 130.657°E; summit elev. 1117 m

All times are local (unless otherwise noted)

6 December, 2149: A moderately strong detonation, air shock, [incandescent column] and volcanic [lightning] were reported. Incandescent tephra fell on the middle flank.

11 December, 0345: Considerable fall of tephra, including [scoria] (4 cm maximum diameter) and non-scoriaceous lapilli (2 cm maximum diameter) E of the summit. Two cm of ash fell 3 km SE of the summit.

13 December, 0106: Lapilli (4.5 cm maximum diameter) broke car windows 3.5 km E of the summit.

[On 6 December] a swarm of about 500 volcanic earthquakes occurred during a 3-hour period. . . .

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.