ABSTRACT

An earthquake swarm occurred at Sofu Seamount near Izu-Torishima in the Izu-Ogasawara (Bonin) Arc, Japan, on 8 October 2023, followed by the arrival of unexpectedly-large tsunamis over a wide area of the Pacific coast of southwest Japan. On 20 October, aerial observation identified floating pumice rafts extending for ~80 km in the area near the seamount, and subsequently the pumice clasts that may have constituted the raft were sampled and found to comprise white-colored rhyolitic pumice containing dark-colored patches. Subsequently, in the summer and autumn of 2024, white pumice, which can be clearly distinguished from the pre-existing gray and black pumice from recent eruptions of oceanic volcanoes, was stranded on the coasts of the Nansei and Ogasawara Islands. This study presented petrographic and geochemical characteristics of the white drift pumice to investigate the dispersal of the small-scale pumice rafting.