Report on Aira (Japan) — 16 December-22 December 2020
Smithsonian / US Geological Survey Weekly Volcanic Activity Report,
16 December-22 December 2020
Managing Editor: Sally Kuhn Sennert
Please cite this report as:
Global Volcanism Program, 2020. Report on Aira (Japan). In: Sennert, S K (ed.), Weekly Volcanic Activity Report, 16 December-22 December 2020. 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 nightly incandescence from Minamidake Crater (at Aira Caldera’s Sakurajima volcano) during 14-21 December and that the sulfur dioxide emission rate remained high. Four explosions were recorded during 16-18 December. One of the explosions, at 1959 on 17 December, generated a plume that rose 3 km above the crater rim and ejected bombs 1.3-1.7 km away from the crater. Another explosion, at 0439 on 18 December, produced a plume that rose 1.8 km and ejected bombs 1-1.3 km away from the crater. The Alert Level remained at 3 (on a 5-level scale).
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 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.