JMA reported ongoing eruptive activity at Minamidake Crater (Aira Caldera’s Sakurajima volcano) during 13-20 May with nighttime crater incandescence. An explosion at 1442 on 15 May generated an ash plume that rose 2 km above the crater rim and drifted SE and ejected blocks as far as 1.1 km from the crater. Sulfur dioxide emissions were elevated, averaging 700 tons per day on 17 May. Explosions at 1928 on 18 May and 0121 on 20 May produced ash plumes that rose 1.2 and 2.3 km, respectively, above the crater rim and drifted W. The explosions ejected blocks 0.5-1.1 km from the crater. An eruptive event at 1442 on 20 May generated an ash plume that rose 1.2 km and drifted S. The Alert Level remained at 3 (on a 5-level scale), and the public was warned to stay 1 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.

Source: Japan Meteorological Agency (JMA)