Report on Aira (Japan) — 27 July-2 August 2016
Smithsonian Institution / US Geological Survey
Weekly Volcanic Activity Report, 27 July-2 August 2016
Managing Editor: Sally Sennert.
Please cite this report as:
Global Volcanism Program, 2016. Report on Aira (Japan) (Sennert, S, ed.). Weekly Volcanic Activity Report, 27 July-2 August 2016. 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 that on 26 July an explosive eruption at Showa Crater (at Aira Caldera’s Sakurajima volcano) ejected tephra 800 m away from the crater and generated an ash plume that rose 5 km above the crater rim. Significant amounts of ash fell in the W and SW parts of the island and in multiple areas of Kagoshima (10-12 km W). 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.