Pumice Drifting from Ioto Volcano in the Izu–Bonin Arc to the Nansei Islands, Japan

Abstract

Pumice is a pyroclastic material of low density and is occasionally buoyant in water. When it erupts from submarine volcanoes, it can drift long distances and wash ashore at remote beaches. Pumice from the eruption of Fukutoku-Oka-no-Ba volcano in the Izu–Bonin arc in October 2021 drifted for about 2 months over a distance of > 1300 km onto the Nansei Islands of Japan, disrupting shipping, fishing, and coastal ecosystems. In March 2024, large amounts of dark brown to black pumice washed ashore on these islands, and subsequently in the Kanto area of Japan. Their geochemical and petrographic characteristics were examined, and Ioto volcano, which is one of the most active volcanoes in Japan, was identified as a possible source based on these characteristics. Small amounts of similar pumice clasts drifting ashore in the Nansei Islands during 2022–2023 were also identified as originating from Ioto volcano. Since July 2022, volcanic activity involving magma eruption has occurred off the southeast coast of Ioto, where pumice rafts generated by the eruptions have been observed. Drift simulations indicate that pumice ejected from Ioto could reach the Nansei Islands, where it is widely distributed. The observation of pumice drifting along the coast of these islands thus provides information on the dispersal of pumice to other parts of Japan, with sources effectively identified through their chemical composition. The results contribute to our understanding of the eruption histories of submarine volcanoes in the Izu–Bonin arc.