Seawater-magma interactions sustained the high column during the 2021 phreatomagmatic eruption of Fukutoku-Oka-no-Ba

Abstract

Abstract Phreatomagmatic eruptions are among the most hazardous types of volcanic eruptions on Earth. Here, we show how rapidly ascended magma interacted with seawater in a shallow sea environment based on a high-resolution timeseries record of a sizeable phreatomagmatic eruption that occurred at the Fukutoku-Oka-no-Ba volcano, Ogasawara, on 13 August 2021. The eruption started on the seafloor at a depth of <70 m and breached the sea surface to produce a 16 km-high, water-rich sustained eruption column. The magma volume, ~0.1 km 3 , including the tuff cone and the pumice raft, is consistent with SO 2 emissions estimated from satellite observations and geochemistry. Most eruption and deposit observations can be explained by the effective near-vent accumulation of pyroclasts emitted during jet-seawater interactions fed by magma discharging at a rate of 3–6 × 10 5 kg/s. Our results contribute to understanding the dynamics and hazards of shallow submarine volcanism.