HR: 17:15h
AN: V14A-06    [Abstracts]
TI: Spreading and Degassing of Lava Flows
AU: * Michaut, C
EM: chloe.michaut@yale.edu
AF: Yale University, 210, Whitney Avenue P.O. Box 208-109, New Haven, CT 06520-8109, United States
AU: Bercovici, D
EM: david.bercovici@yale.edu
AF: Yale University, 210, Whitney Avenue P.O. Box 208-109, New Haven, CT 06520-8109, United States
AB: Lava flows are complex types of viscous gravity currents. They are comprised of a mixture of several components : lava, gas and crystals, which influence the spreading of the flow. The physical properties of the flow, density and viscosity, depend on gas and crystal contents. Relative motions between phases due to density difference and compaction of the matrix also introduce strong complexity relatively to the single-phase gravity current theory. Using the 2-phase theory of Bercovici et al (2001), we have developed the general equations for the spreading of a two-phase mixture composed of matrix (lava) and fluid (gas). A loss of gas is considered through the upper boundary of the current. We compare the spreading of a 2-phase mixture, composed of lava and gas, to the spreading of a single-phase lava flow. We consider both constant volume and constant volume rate lava flows. As the current spreads, its surface increases and degassing becomes easier, which, in turn, increases the density and the viscosity of the flow. When the loss of fluid becomes significant, the evolutions of the peak thickness and radius diverge significantly from the single-phase evolution. It returns to it when degassing is complete. We derive the characteristic time for complete degassing of lava flows as a function of gas and lava physical properties. We also find a characteristic thickness for degassing to become significant and a characteristic radius for complete degassing. The self-similar shape of a two-phase viscous gravity current does not differ significantly from the shape of a single-phase flow.
DE: 8414 Eruption mechanisms and flow emplacement
DE: 8429 Lava rheology and morphology
DE: 8430 Volcanic gases
DE: 8439 Physics and chemistry of magma bodies
SC: Volcanology, Geochemistry, Petrology [V]
MN: 2007 Fall Meeting