The Japan Meteorological Agency (JMA) reported ongoing eruptive activity at Minamidake Crater (Aira Caldera’s Sakurajima volcano). No eruptive events were recorded during 5-15 May, though inflation continued to be detected in deformation data, notably starting at 2000 on 12 May. Sulfur dioxide emissions were slightly low, averaging 300 tons per day (t/d); the last measurement was 900 t/d on 2 May. Continuous eruptive activity, including seven explosions, began at around 1045 on 15 May and ended at around 0400 on 16 May, producing ash plumes that rose as high has 3 km above the summit and drifted in multiple directions. Large blocks were ejected as far as 1.2 km from the vent. Field observations confirmed notable ashfall on the E part of the island on 15 May and the N side of the island on 16 May. Deformation data showed a period of deflation after explosions on 15 May, then inflation resumed. Eruptive activity occurred intermittently during 16 May through at least 1500 on 19 May; 86 eruptive events and 44 explosions were detected, generating ash plumes that generally rose as high as 2.9 km above the crater and ejecting blocks as far as 900 m from the crater rim. An ash plume from an explosion at 1854 on 18 May rose 3.2 km above the crater rim and rifted SE, and large blocks were ejected as far as 1.2 km from the crater rim. The Alert Level remained at 3 (on a 5-level scale), and the public was warned to be cautious within 2 km of both the Minimadake and Showa 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)