Far-reaching volcaniclastic density current deposits as evidence of explosive marine eruptions

Underwater sediment density currents triggered by marine volcanic eruptions threaten island communities and infrastructure, while their deposits provide archives of past eruptions. Despite their significance, scarce real-time density current observations and concurrent deposit samples limit our understanding of their behaviour and relationship to varying volcanic mechanisms. Using data acquired following the explosive, VEI 6, shallow-submarine eruption of Hunga Volcano in 2022, we show that syn-eruptive delivery of pyroclastic material into the ocean via low-column collapses and fountaining triggered the multidirectional dispersal of highly-concentrated underwater density currents. Rapid supply of > 6.5 km 3 of dense pyroclastic material onto the steep volcanic flanks over minutes-to-hours generated currents that maintain high density and velocity 10-100s of kilometres from the volcano. We outline diagnostic criteria to differentiate deposits of shallow-submarine generated underwater currents from other volcanic processes - enabling better reconstruction of the records of volcanic activity in marine sediments and enhancing hazard assessments in submerged volcanic settings worldwide.