Report on Suwanosejima (Japan) — 18 October-24 October 2023
Smithsonian Institution / US Geological Survey
Weekly Volcanic Activity Report, 18 October-24 October 2023
Managing Editor: Sally Sennert.
Please cite this report as:
Global Volcanism Program, 2023. Report on Suwanosejima (Japan) (Sennert, S, ed.). Weekly Volcanic Activity Report, 18 October-24 October 2023. Smithsonian Institution and US Geological Survey.
Suwanosejima
Japan
29.638°N, 129.714°E; summit elev. 796 m
All times are local (unless otherwise noted)
JMA reported that the eruption at Suwanosejima's Ontake Crater continued during 16-23 October and crater incandescence was visible nightly. Eruptive events generated plumes that rose as high as 1.6 km above the crater rim and drifted S and SE and ejected large blocks as far as 400 m from the vent. Ash fell in Toshima village (3.5 km SSW). Explosions recorded at 0454 and 0517 on 16 October produced ash plumes that rose 500-600 m above the crater rim and drifted SE. During an overflight on 17 October scientists observed no notable changes in the crater and surrounding areas. The Alert Level remained at 2 (on a 5-level scale) and the public was warned to stay at least 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.