Effects of Vent Asymmetry on Explosive Eruptions

Current computer models of volcanic eruptions are typically based on symmetric vent and conduit geometries. However, in natural settings, these features are rarely perfectly symmetric. For example, the May 18, 1980 eruption of Mount St Helens (MSH) took place through a highly asymmetrical crater due to the preceding landslide and subsequent vent erosion. In supersonic, high pressure eruptions, such as what may have occurred at MSH, vent and crater asymmetry can strongly affect the directionality of the gas-thrust region. These effects on eruption direction may have implications for the formation of lateral blasts and pyroclastic density currents (PDCs). Here, we present preliminary results from numerical simulations using CartaBlanca, a Java based simulation tool for non-linear physics as developed at Los Alamos National Laboratory. Using 2D time-dependent simulations of explosive volcanic eruptions, we study the effects of vent asymmetry on a variety of eruptive conditions. Preliminary results suggest that asymmetric vent shape may provide an additional mechanism for the formation of lateral blasts and PDCs.