Report on Aira (Japan) — June 1980
Scientific Event Alert Network Bulletin, vol. 5, no. 6 (June 1980)
Managing Editor: David Squires.
Aira (Japan) Activity declines. Explosions/month tabulated since 1955
Please cite this report as:
Global Volcanism Program, 1980. Report on Aira (Japan). In: Squires, D. (ed.), Scientific Event Alert Network Bulletin, 5:6. Smithsonian Institution. https://doi.org/10.5479/si.GVP.SEAN198006-282080.
31.593°N, 130.657°E; summit elev. 1117 m
All times are local (unless otherwise noted)
The period of unusually frequent explosions at Sakura-jima that began in late March ended on 7 June. In May, 69 explosions were recorded, the third highest monthly total since the eruption began in October 1955. Most of the May and June explosions produced ash clouds that rose 1-2 km above the crater; the highest clouds were 2.5 km on 17 May and 2.7 km on 7 June. A 100 m-high incandescent column was observed at night on 1 May.
Ash emission without an explosion [shock] has also more frequent than usual from late March through early June. Ash often fell on Kagoshima, causing various minor disruptions. Fallen ash derailed a streetcar on 2 May, and electric power for 3,700 homes was cut off on 8 May after wet, sticky ash caused numerous short circuits. During a heavy rainfall on 12 May, a debris flow damaged a concrete bridge at the foot of the volcano. Ash emission declined in mid and late 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, Tokyo.