Report on Aira (Japan) — March 1977
Natural Science Event Bulletin, vol. 2, no. 3 (March 1977)
Managing Editor: David Squires.
Aira (Japan) Explosive activity continues
Please cite this report as:
Global Volcanism Program, 1977. Report on Aira (Japan). In: Squires, D (ed.), Natural Science Event Bulletin, 2:3. Smithsonian Institution. https://doi.org/10.5479/si.GVP.NSEB197703-282080.
31.593°N, 130.657°E; summit elev. 1117 m
All times are local (unless otherwise noted)
The explosion at 1632 on 31 January (figure 2) deposited a considerable quantity of lapilli [S of the crater]. At 1005 the next day, a strong air shock broke [65 windowpanes at a school in Tarumizu City, about 10 km SE of the crater]. After the l February explosions, [ash] emission from the crater ceased until 6 March [but white vapor emission continued from 2 February until the 6 March explosions]. The number of volcanic earthquakes decreased in February and March.
|Figure 2. Summary table of explosions from Minami-dake crater at Sakura-jima, 1977. Data courtesy of JMA.|
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.