HR: 08:45h
AN: V21E-04    [Abstracts]
TI: Computational models of overpressured volcanic plumes: Implications for ash dispersion
AU: * Ogden, D E
EM: dogden@es.ucsc.edu
AF: Earth and Planetary Sciences Dept., University of California Santa Cruz, 1156 High Street, Santa Cruz, CA 95064, United States
AU: Glatzmaier, G A
EM: glatz@es.ucsc.edu
AF: Earth and Planetary Sciences Dept., University of California Santa Cruz, 1156 High Street, Santa Cruz, CA 95064, United States
AU: Wohletz, K H
EM: wohletz@lanl.gov
AF: Earth and Environmental Sciences, Geophysics Group, Los Alamos National Laboratory, Los Alamos, NM 87545, United States
AU: Brodsky, E E
EM: brodsky@es.ucsc.edu
AF: Earth and Planetary Sciences Dept., University of California Santa Cruz, 1156 High Street, Santa Cruz, CA 95064, United States
AB: Although impractical for real-time hazards analysis, high-resolution computational fluid dynamics models provide detailed information about ash dispersion and often demonstrate flow behaviors that are not predicted by faster, parameterized plume models. Here, using computational models, we show that two eruptions with the same mass and heat flows at the vent have drastically different plume dynamics depending on whether the vent pressure is greater than or equal to atmospheric pressure. In the simulations shown here, an increase in vent pressure leads to a much higher gas-thrust region and the formation of a transitional column, which oscillates regularly between buoyant rise and collapse. In most treatments of plumes, however, vent pressure is assumed to be atmospheric or to have no effect on the flow dynamics of the greater column. The simulations shown here and others demonstrate that vent pressure is an important controlling parameter of plume dynamics that may have far reaching effects on ash dispersal.
DE: 0500 COMPUTATIONAL GEOPHYSICS (3200, 3252, 7833)
DE: 0545 Modeling (4255)
DE: 8428 Explosive volcanism
DE: 8488 Volcanic hazards and risks
SC: Volcanology, Geochemistry, Petrology [V]
MN: 2007 Fall Meeting