HR: 16:00h
AN: U34A-01 INVITED    [Abstracts]
TI: Models of Plate Motion, Mantle Flow, Mantle Plumes and Reference Frames
AU: * O'Connell, R J
EM: oconnell@geophysics.harvard.edu
AF: Dept. Earth & Planetetary Sciences, Harvard University, 20 Oxford St., Cambridge, MA 02138, United States
AU: Becker, T W
EM: twb@usc.edu
AF: Department of Earth Sciences, University of Southern California, Los Angeles, CA 90089- 0740, United States
AU: Steinberger, B M
EM: bernhard.steinberger@ngu.no
AF: Center for Geodynamics, Geological Survey of Norway, Trondheim, 7491, Norway
AB: Models of mantle flow have been developed over the last several years that allow a unified treatment of plate motions and mantle flow. The models use the history of plate motions and density anomalies inferred fron seismic tomography as inputs and require specification of the viscosity structure. The models are adequate for investigating the last 100 My or so of Earth history; extension to earlier times is limited by the inherent indeterminancy of the energy equation, as well as by uncertainties in plate configurations and motions in the past. Mantle plumes imbedded in such models indicate the motion of hotspots and allow the testing of hotspot based reference frames. The models allow dynamical ( e.g. no net rotation) and kinematic ( e.g. hot spot) reference frames to be related. Such models have quantified the expected motions of hot spots, placed constraints of mantle rheology and density anomalies, and reconciled some apparent hot spot motions. They also allow testing the relationship between hotspot/plume locations and seismic anomalies in the deep mantle. Mantle flow is the result of 1) the return flow from subduction to ridges, 2) flow driven by viscous drag from plate motions, and 3) flow driven by internal density anomalies. The relative nagnitudes of these vary spatially, and each depends on viscosity structure. (1) may be largely accomodated in a sufficiently low viscosity upper mantle; (2) will be attenuated with depth by an increase with viscosity with depth; (3) depends on the rheological structure and magnitude and locations of density anomalies. These lead to uncertainties in the models; comparisons with hotspot motion, plume locations, slab trajectories and seismic tomography further refine our knowledge of mantle properties and structure.
DE: 8120 Dynamics of lithosphere and mantle: general (1213)
DE: 8121 Dynamics: convection currents, and mantle plumes
DE: 8137 Hotspots, large igneous provinces, and flood basalt volcanism
DE: 8158 Plate motions: present and recent (3040)
SC: Union [U]
MN: 2007 Fall Meeting