The Japan Meteorological Agency (JMA) reported that eruptive activity at Suwanosejima's Ontake Crater continued during 20-27 January. Incandescence was observed nightly in webcam images. Discrete eruption events were recorded at 1217 and 1407 on 22 January and at 0754 on 23 January. Eruptions produced ash plumes that reached 1.2-1.5 km above the crater rim, and ash drifted to the N and SW. One explosive event, detected by infrasound monitoring equipment at 1527 on 25 January, produced ash emissions that reached 800 m above the crater rim and drifted SW. Ballistic projectiles were ejected as far as 300 m from the center of the crater. Tremor accompanied the eruption events and ashfall was reported by the Suwanosejima Branch of the Toshima Village Office (3.5 km SSW). The Alert Level remained at 2 (the second level on a five-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)