JMA reported 22 events at Showa Crater (at Aira Caldera’s Sakurajima volcano) during 22-29 May, seven of which were explosive. The explosions ejected material as high as 800 m above the crater rim, and as far away as 500 m. Ash plumes rose as high as 3.3 km on 23 May and 3.4 km on 29 May. Crater incandescence was detected on 25 May. A very small event occurred at Minamidake summit crater on 26 May. 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.

Source: Japan Meteorological Agency (JMA)