Report on Aira (Japan) — 24 July-30 July 2019
Smithsonian Institution / US Geological Survey
Weekly Volcanic Activity Report, 24 July-30 July 2019
Managing Editor: Sally Sennert.
Please cite this report as:
Global Volcanism Program, 2019. Report on Aira (Japan) (Sennert, S, ed.). Weekly Volcanic Activity Report, 24 July-30 July 2019. Smithsonian Institution and US Geological Survey.
31.5772°N, 130.6589°E; summit elev. 1117 m
All times are local (unless otherwise noted)
JMA reported that on 22 July an explosion at Minamidake crater (at Aira Caldera’s Sakurajima volcano) generated an ash plume that rose to 1.5 km above the crater rim. At 1725 and 1754 on 28 July ash plumes rose 3.5-3.8 km above the crater rim and causing ashfall in areas N of the crater including Kirishima (20 km NE), Shimizu Town, and parts of the Kumamoto Prefecture. 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 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.