Report on Ioto (Japan) — 25 April-1 May 2012
Smithsonian Institution / US Geological Survey
Weekly Volcanic Activity Report, 25 April-1 May 2012
Managing Editor: Sally Sennert.
Please cite this report as:
Global Volcanism Program, 2012. Report on Ioto (Japan) (Sennert, S, ed.). Weekly Volcanic Activity Report, 25 April-1 May 2012. Smithsonian Institution and US Geological Survey.
24.751°N, 141.289°E; summit elev. 169 m
All times are local (unless otherwise noted)
According to a JMA report on 2 May, an eruption at Ioto (Iwo-jima) caused water discoloration to the NE. A new fumarole was also confirmed.
Geological Summary. Ioto in the central Volcano Islands portion of the Izu-Bonin-Mariana arc lies within a 9-km-wide submarine caldera. Ioto, Iwojima, and Iojima are among many transliterations of the name. 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.