HR: 09:48h
AN: U11B-09    [Abstracts]
TI: Layered Convection in Earth's Mantle: Results from New Control Volume Based Analyses
AU: * Peltier, W R
EM: peltier@atmosp.physics.utoronto.ca
AF: Department of Physics, University of Toronto, 60 St George Street, Toronto, ON M5S 1A7, Canada
AU: Shahnas, H
EM: shahnas@atmosp.physics.utoronto.ca
AF: Department of Physics, University of Toronto, 60 St George Street, Toronto, ON M5S 1A7, Canada
AB: The issue of the extent to which the mantle convective circulation may be layered by the influence of phase transitions and/or by the variation of physical properties remains unresolved. That the endothermic transition at 660 km depth coupled with an increase in viscosity across this horizon provides a significant impediment to radial mass flux is clear on the basis of recent seismic tomographic images from several geographic regions. In these regions, high resolution reconstructions of Benioff zone body-wave heterogeneity demonstrate that the downgoing slab appears to be "trapped" in the transition zone rather than continuing to descend through it.We will describe a series of new simulations of the convective mixing process based upon the application of a highly accurate control volume-based methodology. The model includes the influences of three major phase transformations (Olivine-Spinel, Spinel-Perovskite+Magnesiowustite, and Perovskite-post Perovskite) as well as accurate pressure and temperature dependences of thermal conductivity, coefficient of thermal expansion and viscosity. In this model the flow is characterized by significant layering, with radial mass flux strongly inhibited across the base of the transition zone. The "avalanche effect" previously identified by Solheim and Peltier (JGR 99, 1994) and Butler and Peltier (JGR 107, 2002) is found to be especially pronounced. Our models are consistent with the Urey ratio, global heat flow and CMB temperature constraints.
DE: 3924 High-pressure behavior
DE: 4255 Numerical modeling (0545, 0560)
DE: 6982 Tomography and imaging (7270, 8180)
DE: 8124 Earth's interior: composition and state (1212, 7207, 7208, 8105)
DE: 8180 Tomography (6982, 7270)
SC: Union [U]
MN: 2007 Fall Meeting