HR: 11:00h
AN: GP22A-03    [Abstracts]
TI: A consistent model of large-scale mantle flow, hotspot motion, true polar wander and plate motions
AU: Steinberger, B
EM: bernhard.steinberger@ngu.no
AF: NGU, Center for Geodynamics, Leiv Eirikssons vei 39, Trondheim, 7491 Norway
AU: * O'Connell, R
EM: oconnell@geophysics.harvard.edu
AF: Harvard University, Department of Earth and Planetary Sciences, 20 Oxford Street, Cambridge, MA 02138 United States
AB: Mantle plumes are expected to be affected by large-scale flow in the Earth's mantle related to plate motions, subducted slabs, and possibly large-scale upwellings. Motion of plume conduits will depend on both large-scale flow and buoyant rising speed of the conduit through the mantle. Our model of large-scale flow is based on mantle density anomalies inferred from seismic tomography and mineral physics, and a viscosity structure that is also consistent with mineral physics. Flow and density field are also in accord with the geoid and global heat flux. Using the same viscosity model and new experimental constraints we compute depth-dependent plume radius and buoyant rising speed. We expect thermal plume radii of about 100 km in the upper mantle, increasing to about 300 km in the lower part of the mantle, in agreement with recent results from tomography. This yields somewhat larger conduit rising speeds than previously assumed, and predicted hotspot surface motion is often similar to the horizontal flow component in the lower part of the mantle. Our flow model also considers advection of density anomalies, hence changes of the geoid with time and true polar wander can be computed. Thus we are also able to consistently compute hotspot paleolatitudes - an important observational constraint on hotspot motion. Combination of hotspot motion and plate motion allows computation of hotspot tracks; if there are alternative plate motion models we are able to determine which one yields the best fit. Our results are of particular importance for the relative motion between Pacific and African plates between 47 and 83 Ma.
DE: 1213 Earth's interior--dynamics (8115, 8120)
DE: 1239 Rotational variations
DE: 8121 Dynamics, convection currents and mantle plumes
DE: 8157 Plate motions--past (3040)
SC: Geomagnetism and Paleomagnetism [GP]
MN: 2005 Joint Assembly