Report on Aira (Japan) — 6 December-12 December 2023
Smithsonian Institution / US Geological Survey
Weekly Volcanic Activity Report, 6 December-12 December 2023
Managing Editor: Sally Sennert.
Please cite this report as:
Global Volcanism Program, 2023. Report on Aira (Japan) (Sennert, S, ed.). Weekly Volcanic Activity Report, 6 December-12 December 2023. Smithsonian Institution and US Geological Survey.
Aira
Japan
31.5772°N, 130.6589°E; summit elev. 1117 m
All times are local (unless otherwise noted)
JMA reported ongoing activity at Minamidake Crater (Aira Caldera’s Sakurajima volcano) during 4-11 December, with incandescence at the crater observed nightly. Small eruptive events were recorded during 4-8 December. Sulfur dioxide emissions were high, averaging 2,900 tons per day on 8 December. Explosions at 1028 and 1533 on 10 December produced ash plumes that rose 1.5-1.8 km above the crater rim and drifted N. An eruptive event at 1748 on that same day produced an ash plume that rose 1.2 km and drifted N. The Alert Level remained at 3 (on a 5-level scale), and the public was 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 caldera, along with several post-caldera cones. The construction of Sakurajima began about 13,000 years ago on the southern rim and built an island that was joined to the Osumi Peninsula during the major explosive and effusive eruption of 1914. Activity at the Kitadake summit cone ended about 4,850 years ago, after which eruptions took place at Minamidake. Frequent eruptions since the 8th century have deposited ash on the city of Kagoshima, located across Kagoshima Bay only 8 km from the summit. The largest recorded eruption took place during 1471-76.