Global database on surface phenomena and hazards of explosive submarine eruptions with application to hazards of the Kolumbo Volcanic Field

Abstract Submarine volcanic eruptions can produce diverse surface phenomena and hazards that differ from those of eruptions on land, such as phreatomagmatic explosions, tsunamis, and pumice rafts. Understanding the causes and processes of these surface phenomena and hazards posed especially by explosive submarine eruptions is essential for disaster prevention and mitigation for volcanoes near or below sea level. I constructed a global database of all known submarine eruptions and extracted their general characteristics. The detailed surface phenomena and processes of noteworthy explosive submarine eruptions in recent years are also summarized. Such data and analyses are useful to elucidate key phenomena and processes during submarine eruptions and to evaluate the types and effects of hazards. I focus on the relationship between water depth and the occurrence of hazardous surface phenomena, including explosivity, subaerial pyroclastic density currents (PDCs), and tsunamis. The number of explosive phenomena on the sea surface and tsunamis produced decreases dramatically where the vent is at depths ≥ 400 m, and eruption detection methods are almost entirely limited to seismoacoustic signals, pumice rafts, discolored water, and direct observation by on-site expeditions. However, because of the difficulty of detecting deep-sea eruptions without surficial manifestations, they are almost certainly under-reported in the database. Eruptions accompanied by PDCs over the sea surface represent less than 11% of the total, although eruptions in shallow water are more likely to be accompanied by PDCs. The database analysis improves our knowledge of hazardous phenomena caused by submarine eruptions, and also contributes to constraining phenomena during past historical eruptions, such as the 1650 CE eruption of Kolumbo Central Volcano, southern Aegean, and assessing future hazards at Kolumbo and other submarine volcanoes.