EFFECTS OF COMPLEX VENT GEOMETRY ON VOLCANIC JET DECOMPRESSION

Sustained explosive volcanic eruptions consist of high-pressured magma decompressing through a conduit, ultimately expanding into the atmosphere. Close to the surface, conduits can flare rapidly, forming volcanic vents. Here we present numerical simulations of explosive volcanic eruptions through fixed and evolving vent geometries. Depending on vent shape alone, the expansion of the same high-pressure magma can result in subsonic jets at atmospheric pressure or supersonic jets with pressures that are greater than, less than, or equal to atmospheric pressure. These different vent exit conditions then control the fluid dynamics of the eruption including the structure and velocity of the eruption column, the formation of pyroclastic flows, and the distribution of lithic fragments.