JMA reported that eruptive activity at Suwanosejima's Ontake Crater continued during 5-12 August. Crater incandescence was observed nightly in webcam images. Eruptive events were recorded at 2109 on 6 August, at 0056, 0124, 0236, 0313, 0349, 0657, and 0955 on 7 August, and at 0207, 1156, 1225, and 1440 on 8 August. Ash plumes rose 1-1.4 km above the crater rim and drifted mainly SW, S, and SE. Explosions were recorded at 1457, 1625, and 1717 on 10 August, though emissions were not visually observed. Explosions at 2103 on 10 August, at 1011 and 1213 on 11 August, and at 0054 and 0207 on 12 August generated ash plumes that rose 200-600 m above the crater rim and drifted SE; sometimes the plumes rose into weather clouds. The Alert Level remained at 2 (on a 5-level scale) and the public was warned to stay at least 1.5 km away from the crater.

Geological Summary. The 8-km-long island of Suwanosejima in the northern Ryukyu Islands consists of an andesitic stratovolcano with two active summit craters. The summit is truncated by a large breached crater extending to the sea on the E flank that was formed by edifice collapse. One of Japan's most frequently active volcanoes, it was in a state of intermittent Strombolian activity from Otake, the NE summit crater, between 1949 and 1996, after which periods of inactivity lengthened. The largest recorded eruption took place in 1813-14, when thick scoria deposits covered residential areas, and the SW crater produced two lava flows that reached the western coast. At the end of the eruption the summit of Otake collapsed, forming a large debris avalanche and creating an open collapse scarp extending to the eastern coast. The island remained uninhabited for about 70 years after the 1813-1814 eruption. Lava flows reached the eastern coast of the island in 1884. Only about 50 people live on the island.

Source: Japan Meteorological Agency (JMA)