Myojinsho (Japan)

Status Unknown Eruption 1970 11m
Submarine (Subduction zone / Oceanic crust (< 15 km))

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.

Steam pours from the blocky summit of a lava dome formed at Myojin-sho during a submarine eruption at the Bayonnaise Rocks volcano in 1952. This September 22 photo was taken six days after the dome began to breach the sea surface. Later that day the eruption became highly explosive, and the dome was destroyed. Three cycles of dome growth and destruction occurred until October 1953. Myojin-sho is located on the eastern rim of a 7-9 km wide submarine caldera.

Photo courtesy of Helen Foster, 1952 (U.S. Geological Survey).

Last updated 2019-08-04 00:28:03