Pyroclastic density currents

Abstract High-speed, gravity-driven flows of hot particles and gas are a common and highly destructive product of explosive volcanism. They range widely in nature from expanded, turbulent suspension currents formed by lateral blasts or by the fountaining of vertical eruption columns, to highly concentrated granular avalanches formed by lava dome col-lapse or as dense underflows beneath suspension currents. The deposits from these flows, here called pyroclastic density currents, range in volume from much less than 1 km 3 to thousands of cubic kilometres, and may extend over 100 km from their source. This chapter reviews the eruption, transport and deposition of pyroclastic density currents from both geological and physical perspectives, focussing on some recent advances.