HR: 08:15h
AN: U11B-02 INVITED    [Abstracts]
TI: Layers in the mantle - dynamics and structure
AU: * van Keken, P E
EM: keken@umich.edu
AF: University of Michigan, Geological Sciences 1100 North University Avenue 2534 CC Little Building, Ann Arbor, MI 48105, United States
AB: The answer to the question whether the Earth's mantle is dominated by whole or layered convection depends in large part on the interpretation of the signals that the observational sciences provide. Seismology provides a snapshot of the current structure with clear evidence for structural layering in the mantle. Geochemistry provides a long term integrated look into the composition of the Earth with strong suggestions for both significant mixing and long term sequestration of isotopic heterogeneity. Forward modeling of mantle convection can be used to test under which dynamical conditions we can recreate the present day structure and long term integrated views that seismology and geochemistry provide. In addition, basic physical observations such as heat flow, plate velocities, geoid and topography, provide alternative constraints on the structure of mantle convection. It appears that strict mantle layering at 660 km depth can be ruled out based on dynamical considerations alone, but the question remains how strong the mass fluxes are from the upper mantle into the lower mantle. I will use existing and new geodynamical models of mantle convection to estimate the extent to which layering can be generate by physical processes, such as compositional variations, phase changes and pressure- dependent rheology, that still provide reasonable predictions for surface velocities and heatflow. I will show that from a strictly dynamical point of view the preferred form of mantle convection remains a moderated form of whole mantle convection, in which the lower mantle moves more sluggishly than the upper mantle. This type of model can also explain many, but not all, of the seismological and geochemical observations.
DE: 0545 Modeling (4255)
DE: 8121 Dynamics: convection currents, and mantle plumes
DE: 8124 Earth's interior: composition and state (1212, 7207, 7208, 8105)
DE: 8162 Rheology: mantle (8033)
SC: Union [U]
MN: 2007 Fall Meeting