JMA reported that there were less than 10 small events at Showa Crater (at Aira Caldera’s Sakurajima volcano) during 26-27 April, the first eruptions at that crater since 26 July 2016. During 28 April-1 May there were 16 events, of which two were explosive, ejecting tephra up to 800 m from the crater. One of the explosive events, at 1101 on 28 April, generated an ash plume that rose 3.2 km above the crater rim. 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.

Source: Japan Meteorological Agency (JMA)