Logo link to homepage

Report on Aira (Japan) — July 1995


Bulletin of the Global Volcanism Network, vol. 20, no. 7 (July 1995)
Managing Editor: Richard Wunderman.

Aira (Japan) Only one explosive eruption during July

Please cite this report as:

Global Volcanism Program, 1995. Report on Aira (Japan) (Wunderman, R., ed.). Bulletin of the Global Volcanism Network, 20:7. Smithsonian Institution. https://doi.org/10.5479/si.GVP.BGVN199507-282080



31.5772°N, 130.6589°E; summit elev. 1117 m

All times are local (unless otherwise noted)

Volcanism at Sakura-jima continued at a moderate rate through June, and dwindled in July. Throughout June there were 18 eruptions, 10 which were explosive. The highest ash plume of June reached 2,500 m elevation (2 June). The monthly ashfall accumulation at Kagoshima Meteorological Observatory, 10 km W of Minami-dake crater, was 11 g/m2. Throughout June, 550 earthquakes and 349 tremors were recorded at Station B, 2.3 km NE of Minami-dake crater.

During July, Sakura-jima generated only one explosive eruption. The 18 July ash plume rose 2,100 m above the crater rim. The monthly ash fall accumulated at Kagoshima Observatory measured 5g/m2. An earthquake swarm consisting of ~170 events occurred during 1600-2100 on 31 July. The totals for the numbers of monthly earthquakes and tremors at Station B were 655 and 533, respectively.

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 caldera, along with several post-caldera cones. The construction of Sakurajima began about 13,000 years ago on the southern rim and built an island that was joined to the Osumi Peninsula during the major explosive and effusive eruption of 1914. Activity at the Kitadake summit cone ended about 4,850 years ago, after which eruptions took place at Minamidake. Frequent eruptions since the 8th century have deposited ash on the city of Kagoshima, located across Kagoshima Bay only 8 km from the summit. The largest recorded eruption took place during 1471-76.

Information Contacts: Volcanological Division, Seismological and Volcanological Department, Japan Meteorological Agency (JMA), 1-3-4 Ote-machi, Chiyoda-ku, Tokyo 100, Japan.