Report on Myojinsho (Japan) — 21 March-27 March 2018
Smithsonian / US Geological Survey Weekly Volcanic Activity Report,
21 March-27 March 2018
Managing Editor: Sally Kuhn Sennert
Please cite this report as:
Global Volcanism Program, 2018. Report on Myojinsho (Japan). In: Sennert, S K (ed.), Weekly Volcanic Activity Report, 21 March-27 March 2018. Smithsonian Institution and US Geological Survey.
31.888°N, 139.918°E; summit elev. 11 m
All times are local (unless otherwise noted)
JMA issued a warning on 24 March for the waters surrounding Myojinsho after reports from the Japan Coast Guard indicated discolored water from a possible eruptive event.
Geological Summary. Beyonesu Rocks represent part of the barely exposed rim of the largely submarine Myojinsho caldera. Formation of the 8-9 km wide caldera was followed by construction of a large (2.6 km3) lava dome and/or lava flow complex on the caldera floor, originally located at a depth of 1000-1100 m. Most historical eruptions, recorded since the late-19th century, have occurred from the large post-caldera Myojinsho lava dome on the NE rim of the caldera. Deposits from submarine pyroclastic flows associated with growth of the dacitic lava dome mantle the conical dome and extend into the NE part of the caldera and down its outer slopes. An explosive submarine eruption from Myojinsho in 1952 destroyed a Japanese research vessel, killing all 31 on board. Submarine eruptions have also been observed from other points on the caldera rim and outside of the caldera. The Beyonesu Rocks were named after the French warship the Bayonnaise, which was surveying volcanic islands south of Tokyo Bay in 1850.