Report on Suwanosejima (Japan) — 25 November-1 December 2020
Smithsonian / US Geological Survey Weekly Volcanic Activity Report,
25 November-1 December 2020
Managing Editor: Sally Kuhn Sennert
Please cite this report as:
Global Volcanism Program, 2020. Report on Suwanosejima (Japan). In: Sennert, S K (ed.), Weekly Volcanic Activity Report, 25 November-1 December 2020. Smithsonian Institution and US Geological Survey.
29.638°N, 129.714°E; summit elev. 796 m
All times are local (unless otherwise noted)
JMA reported nighttime incandescence and intermittent eruptive activity at Suwanosejima’s Ontake Crater during 20-27 November. A total of 34 explosions were recorded, ejecting bombs up to 700 m away from the crater and producing gray-and-white plumes that rose 1.4 km above the crater rim. The Tokyo VAAC noted that ash plumes drifted S and SE. Ashfall was reported in Toshima village (4 km SSW). Crater incandescence was visible from the morning of 20 November through 22 November. The Alert Level remained at 2 (on a 5-level scale).
Geological Summary. The 8-km-long island of Suwanosejima in the northern Ryukyu Islands consists of an andesitic stratovolcano with two historically active summit craters. The summit is truncated by a large breached crater extending to the sea on the east 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 blanketed 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 the open Sakuchi caldera, which extends 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.