According to JMA, fieldwork at Aira Caldera’s Sakurajima volcano revealed that the sulfur dioxide flux rose from 300 tons on 28 April to 1,700 tons on 8 May; the last time sulfur dioxide flux was above 1,000 tons was 23 June 2015. At 1312 on 12 May an explosion at Showa Crater generated a plume that rose 700 m above the crater rim, into a weather cloud. Four events were detected during 13-15 May; one of the events, an explosion at Showa Crater on 14 May, produced a plume that rose 2.3 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)