Report on Suwanosejima (Japan) — 3 May-9 May 2023
Smithsonian Institution / US Geological Survey
Weekly Volcanic Activity Report, 3 May-9 May 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, 3 May-9 May 2023. 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 that the eruption at Suwanosejima's Ontake Crater continued during 1-8 May, and crater incandescence was reported nightly. No explosions were recorded during 1-5 May, but eruptive activity produced periodic ash plumes that rose as high as 1.6 km above the crater rim and ejected blocks 300 m from the crater. Explosions at 0701, 1200, 2001, and 2330 on 8 May generated ash plumes that rose as high as 1 km and drifted SE and SW. Explosions also occurred at 1358 and 1648, though no associated emissions were reported. The Alert Level remained at 3 (on a 5-level scale) and residents were warned to stay 2 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 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.