Report on Aira (Japan) — July 1980
Scientific Event Alert Network Bulletin, vol. 5, no. 7 (July 1980)
Managing Editor: David Squires.
Aira (Japan) More frequent explosions
Please cite this report as:
Global Volcanism Program, 1980. Report on Aira (Japan). In: Squires, D (ed.), Scientific Event Alert Network Bulletin, 5:7. Smithsonian Institution. https://doi.org/10.5479/si.GVP.SEAN198007-282080.
31.593°N, 130.657°E; summit elev. 1117 m
All times are local (unless otherwise noted)
After a decline from 69 explosions in May to 12 in June, activity remained at a similar level until late July, when explosions became stronger and more frequent. The last July explosion was also the month's largest. A tephra cloud rose about 3 km, and [blocks fell onto] the lower half of the volcano. Ash fell to the NE, reaching [the city of] Miyakonojo, 40 km away, one hour after the explosion. No damage was reported.
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.