JMA reported that eruptive activity at Suwanosejima's Ontake Crater continued during 2-9 September and crater incandescence was observed nightly in webcam images. The seismic network recorded 12 explosions and numerous eruptive events. Occasional rumbling and ashfall were reported at the Suwanosejima Branch Office in Toshima village (3.5 km SSW) on unspecified dates. The explosions were recorded at 2027 on 2 September, at 1103 and 2304 on 4 September, at 0425, 1602, and 1736 on 5 September, at 0541, 1938, and 2036 on 6 September, at 2121 on 7 September, at 2144 on 8 September, and at 1728 on 9 September. The explosions generated ash plumes that rose 0.4-1.7 km above the crater rim and drifted NW, W, and SW; details about the last two explosions were unknown. Large blocks were sometimes ejected as far as 600 m from the vent. As many as 11 daily eruptive events were also recorded and produced ash plumes that rose as high as 1.6 km above the crater rim and drifted NW, W, and SW. 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)