JMA reported ongoing activity at both Minamidake Crater and Showa Crater (Aira Caldera’s Sakurajima volcano) during 8-15 May. Crater incandescence was observed nightly at Minamidake Crater. On 8 May sulfur dioxide emissions were extremely high at 3,900 tons per day. At 1315 on 9 May an explosion at Minamidake generated an ash plume that rose 1.2 km above the crater rim and drifted SW, and ejected blocks 1.1 km from the vent. Eruptive events at 1527, 1724, and 1817 on 11 May produced ash plumes that rose as high as 1.3 km and drifted NW and W. At Showa Crater eruptive events recorded at 1009, 1303, and 1401 on 8 May, at 0550, 0726, 2204, and 2321 on 11 May, at 1831 on 12 May, and at 0859 on 14 May produced ash plumes that rose as high as 1.7 km above the crater rim and drifted in multiple directions. Sulfur dioxide emissions were somewhat high on 12 May, averaging 1,800 tons per day. The Alert Level remained at 3 (on a 5-level scale), and residents were warned to stay 2 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)