JMA reported that the eruption at Suwanosejima's Ontake Crater continued during 16-22 January and crater incandescence was observed nightly. The Alert Level was lowered to 2 at 1100 on 19 January because the probability of material being ejected more than 1 km laterally had decreased. There were seven explosions detected from 1759 on 19 January to 1222 on 22 January. Details about the plumes were reported for two of them and unknown for the remaining ones; on 21 January an explosion at 1632 produced an ash plume that rose 1 km above the crater rim and drifted SE and an explosion at 2215 produced an ash plume that rose 600 m above the crater rim before merging into weather clouds. The public was warned to stay 1 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)