Report on Aira (Japan) — 18 April-24 April 2018
Smithsonian / US Geological Survey Weekly Volcanic Activity Report, 18 April-24 April 2018
Managing Editor: Sally Kuhn Sennert
Please cite this report as:
Global Volcanism Program, 2018. Report on Aira (Japan). In: Sennert, S K (ed.), Weekly Volcanic Activity Report, 18 April-24 April 2018. Smithsonian Institution and US Geological Survey.
31.593°N, 130.657°E; summit elev. 1117 m
All times are local (unless otherwise noted)
JMA reported that there were eight events and 13 explosions at Minamidake crater (at Aira Caldera’s Sakurajima volcano) during 16-23 April. Tephra was ejected as far as 1.1 km from the crater, and plumes rose as high as 2.5 km above the crater rim. At 0038 on 22 April an explosion produced an ash plume that rose 3.3 km and ejected tephra as far as 1.3 km. Crater incandescence was visible on most nights. The Alert Level remained at 3 (on a 5-level scale).
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.