Report on Aira (Japan) — 8 March-14 March 2023
Smithsonian / US Geological Survey Weekly Volcanic Activity Report,
8 March-14 March 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, 8 March-14 March 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 and Showa Crater (at Aira Caldera’s Sakurajima volcano) during 6-13 March. Incandescence at Minamidake was visible nightly. Five eruptive events at Minamidake were recorded and explosions occurred on 8 and 11 March. Ash plumes rose as high as 1.7 km above the crater rim, and during 10-13 March large blocks were ejected as far as 500 m from the vent. Seven eruptive events occurred at Showa during 6-10 March, producing ash plumes that rose as high as 2.7 km above the crater rim and ejecting large blocks 800 m from the crater. The Alert Level remained at 3 (on a 5-level scale), and residents were warned to stay 2 km away from both craters.
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.