4:30 PM - 4:45 PM
[SVC36-11] Newly drifted pumice in 2024: stranding of white pumice identified on the sea near Torishima
Keywords:EPMA analysis, drift pumice, pumice rafting, volcanic glass, volcanic eruption
Pumice ejected by the 2021 Fukutoku-Oka-no-Ba (FOB) eruption and the ongoing eruptions of Ioto since 2022 first stranded on the Nansei Islands via the Kuroshio Countercurrent, then dispersed along the coasts of the Japanese Islands via the Kuroshio Current (Yoshida et al., 2022; Ishimura and Hiramine, 2025; Hiramine et al., in revision). The 2021 FOB pumice stranding was widely recognized due to massive mass of drift pumice. In contrast, drift pumice from the Ioto eruptions since 2022 was not identified by local residents due to its small stranding mass. Drift pumice recognition on beach depends on depositional volume of drift pumice. Drift pumice provides rare insight into eruption processes and magma characteristics. However, studies focus on large-scale pumice drifting, while smaller-scale detection remains unclear. This study reports drift pumice collected near Izu-Torishima (October 2023) and its distribution across the Japanese Islands.
An earthquake swarm struck Torishima on October 2, 2023. On October 9, an unexpectedly large tsunamis, disproportionate to the earthquake, were observed. The tsunami reached the Izu–Ogasawara Islands and the Japanese Pacific coast (e.g., Japan Meteorological Agency (JMA), 2023; Sandanbata et al., 2024). Japan Coast Guard aerial surveys confirmed a possible pumice raft. The R/V Keifu Maru later collected white drift pumice on the sea near Izu-Torishima (JMA, 2023). These drift pumice clasts later washed ashore on the coasts of Ogasawara Islands and Okinawa Island (Yoshida et al., 2025 EarthArXiv, https://doi.org/10.31223/X5BD92). Given the discovery of similar white drift pumice across the Japanese Islands, we analyzed the volcanic glass composition using EPMA.
The analyzed drift pumice samples include one sample from Ishigaki Island collected in October 2024, one from Amami-Oshima collected in October 2024, two from Kikai Island collected in October 2024, one from Kochi collected in September 2024, one from Tokushima collected in September 2024, one from Jogashima in Miura peninsula collected in November 2024, and one from Toyama collected in October 2024. Additionally, we conducted the same analysis on one sample from Chichijima collected in July 2024 and two samples from Hahajima collected in July 2024, which were reported by Yoshida et al. (2025).
The collected drift pumice samples were analyzed for the major element chemical composition of volcanic glass using an electron probe microanalyzer (EPMA, JEOL JXA-8200) available at the Marine Core Research Institute, Kochi University. For comparison, we used a white drift pumice sample (Tr102702) collected by the JMA, whose chemical characteristics had already been reported by AIST (2023).
The EPMA analyses indicate that all drift pumice samples analyzed in this study have a chemical composition identical to that of Tr102702. Therefore, these drift pumice clasts are considered to be the same as the white drift pumice collected on the sea near Izu-Torishima. Although the sampling dates of the analyzed drift pumice do not necessarily correspond to their actual stranding dates, our findings confirm that drift pumice could reach across various locations in the Japanese Islands until one year after its initial detection at sea near Izu-Torishima. This drifting period is consistent with the case of the 2021 FOB eruption (Ishimura and Hiramine, 2024). Furthermore, our study suggests that drift pumice can serve as an indicator of volcanic eruptions, even for small-scale eruptions that are difficult to detect via satellite images. This finding is significant for reconstructing unrecognized activity of submarine volcanoes, and thus helpful for improving hazardous pumice drift predictions.
An earthquake swarm struck Torishima on October 2, 2023. On October 9, an unexpectedly large tsunamis, disproportionate to the earthquake, were observed. The tsunami reached the Izu–Ogasawara Islands and the Japanese Pacific coast (e.g., Japan Meteorological Agency (JMA), 2023; Sandanbata et al., 2024). Japan Coast Guard aerial surveys confirmed a possible pumice raft. The R/V Keifu Maru later collected white drift pumice on the sea near Izu-Torishima (JMA, 2023). These drift pumice clasts later washed ashore on the coasts of Ogasawara Islands and Okinawa Island (Yoshida et al., 2025 EarthArXiv, https://doi.org/10.31223/X5BD92). Given the discovery of similar white drift pumice across the Japanese Islands, we analyzed the volcanic glass composition using EPMA.
The analyzed drift pumice samples include one sample from Ishigaki Island collected in October 2024, one from Amami-Oshima collected in October 2024, two from Kikai Island collected in October 2024, one from Kochi collected in September 2024, one from Tokushima collected in September 2024, one from Jogashima in Miura peninsula collected in November 2024, and one from Toyama collected in October 2024. Additionally, we conducted the same analysis on one sample from Chichijima collected in July 2024 and two samples from Hahajima collected in July 2024, which were reported by Yoshida et al. (2025).
The collected drift pumice samples were analyzed for the major element chemical composition of volcanic glass using an electron probe microanalyzer (EPMA, JEOL JXA-8200) available at the Marine Core Research Institute, Kochi University. For comparison, we used a white drift pumice sample (Tr102702) collected by the JMA, whose chemical characteristics had already been reported by AIST (2023).
The EPMA analyses indicate that all drift pumice samples analyzed in this study have a chemical composition identical to that of Tr102702. Therefore, these drift pumice clasts are considered to be the same as the white drift pumice collected on the sea near Izu-Torishima. Although the sampling dates of the analyzed drift pumice do not necessarily correspond to their actual stranding dates, our findings confirm that drift pumice could reach across various locations in the Japanese Islands until one year after its initial detection at sea near Izu-Torishima. This drifting period is consistent with the case of the 2021 FOB eruption (Ishimura and Hiramine, 2024). Furthermore, our study suggests that drift pumice can serve as an indicator of volcanic eruptions, even for small-scale eruptions that are difficult to detect via satellite images. This finding is significant for reconstructing unrecognized activity of submarine volcanoes, and thus helpful for improving hazardous pumice drift predictions.