Report on Aira (Japan) — 18 January-24 January 2023
Smithsonian / US Geological Survey Weekly Volcanic Activity Report,
18 January-24 January 2023
Managing Editor: Sally Kuhn Sennert
Please cite this report as:
Global Volcanism Program, 2023. Report on Aira (Japan). In: Sennert, S K (ed.), Weekly Volcanic Activity Report, 18 January-24 January 2023. 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 ongoing eruptive activity at Minamidake Crater (at Aira Caldera’s Sakurajima volcano) during 14-23 January. Crater incandescence was visible nightly. An explosion at 1215 on 18 January produced an ash plume that rose 1.4 km above the crater rim and ejected blocks as far as 1.1 km. Sulfur dioxide emissions were high at 1,400 tons per day. An explosion at 0659 on 19 January generated an ash plume that rose 1.3 km and ejected blocks 600-900 m and an explosion at 0307 on 21 January generated an ash plume that rose 1.6 km and ejected blocks as far as 1.1 km. Occasional very small eruptive events were recorded during 21-22 January. The Alert Level remained at 3 (on a 5-level scale), and residents were warned to stay 2 km away from the crater.
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.