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Report on Ioto (Japan) — 1 November-7 November 2023


Smithsonian Institution / US Geological Survey
Weekly Volcanic Activity Report, 1 November-7 November 2023
Managing Editor: Sally Sennert.

Please cite this report as:

Global Volcanism Program, 2023. Report on Ioto (Japan) (Sennert, S, ed.). Weekly Volcanic Activity Report, 1 November-7 November 2023. Smithsonian Institution and US Geological Survey.

Weekly Report (1 November-7 November 2023)



24.751°N, 141.289°E; summit elev. 169 m

All times are local (unless otherwise noted)

The eruption at Ioto (Iwo-jima), at a vent located about 1 km off the SE coast of Okinahama, continued during 1-3 November. A 2 November Sentinel satellite images showed a thermal anomaly at the SE end of the island which was elongated to the NNW-SSE. A white plume drifted about 400 m WSW. During an overflight on 3 November observers photographed the island and noted that a 169-m-high cone had formed at the SSE end according to news sources. Explosions occurred about every one minute that ejected dark material and incandescent material about 800 m above the vent. Floating, brown-colored pumice was present in the water around the island.

Geological Summary. Ioto, in the Volcano Islands of Japan, lies within a 9-km-wide submarine caldera. The volcano is also known as Ogasawara-Iojima to distinguish it from several other "Sulfur Island" volcanoes in Japan. The triangular, low-elevation, 8-km-long island narrows toward its SW tip and has produced trachyandesitic and trachytic rocks that are more alkalic than those of other volcanoes in this arc. The island has undergone uplift for at least the past 700 years, accompanying resurgent doming of the caldera; a shoreline landed upon by Captain Cook's surveying crew in 1779 is now 40 m above sea level. The Motoyama plateau on the NE half of the island consists of submarine tuffs overlain by coral deposits and forms the island's high point. Many fumaroles are oriented along a NE-SW zone cutting through Motoyama. Numerous recorded phreatic eruptions, many from vents on the W and NW sides of the island, have accompanied the uplift.

Sources: Asahi, Asahi, Sentinel Hub