Deep-sea eruptions boosted by induced fuel-coolant explosions

The majority of Earth's volcanic eruptions occur beneath the sea, but the limited number of direct observations and samples limits our understanding of these unseen events. Subaerial eruptions lend some insight, but direct extrapolation from the subaerial to the deep sea is precluded by the great differences in pressure, thermal conditions, density and rheology, and the interplay among them. Here we present laboratory fragmentation experiments that mimic deep-sea explosive eruptions and compare our laboratory observations with those from the kilometre-deep submarine eruption of Havre Volcano, Kermadec Arc, New Zealand, in 2012. We find that the Havre eruption involved explosive fragmentation of magma by a pressure-insensitive interaction between cool water and hot magma, termed an induced fuel-coolant interaction. The laboratory experiments show that this water-magma interaction is initiated by the formation of cracks in cooling magma into which the water coolant can infiltrate, driving explosive fragmentation. Explosive submarine eruptions have previously been considered unlikely because stabilization of a vapour film at the magma-water contact was thought to be a key requirement but is suppressed at depths exceeding 100 m. However, here we demonstrate that these induced fuel-coolant interactions between magma and water can occur in a range of wet environments regardless of pressure, from the subaerial to the deep sea, and may operate on different planets, as well as apply to materials other than magma and water.