HR: 11:30h
AN: GP22A-05 INVITED     [Abstracts]
TI: Upwelling Plumes, Superswells and True Polar Wander
AU: * GREFF-LEFFTZ, M
EM: greff @ipgp.jussieu.fr
AF: Institut de Physique du Globe de Paris, 4 place Jussieu, Paris, 75252 France
AB: The geological evolution of the Earth's rotational axis is most likely controlled by internal mass redistribution within the mantle. Paleomagnetic observations suggest that it is episodic in nature, with periods of quasi-standstill alternating with periods of faster wander. Here, we investigate two models for the influence of mantle plumes which vary at different spatial wavelengths on the time variations of the rotational axis (True Polar Wander). In the first model, we represent an upwelling plume as a sphere whose radius varies as a function of the flux of material in the conduit, and which traverses the mantle at the Stokes velocity. Such a plume produces very little wander of the rotational axis. We then study the effects of two superswells which mimic the ones observed with seismic tomography, and conclude that a doming regime within the mantle involves significant polar wander. Some of the features of this TPW which are directly linked to the periodicity of doming are reminiscent of observed phases of slow and fast true polar wander, with similar peak velocities.
DE: 1239 Rotational variations
DE: 1525 Paleomagnetism applied to tectonics (regional, global)
DE: 3040 Plate tectonics (8150, 8155, 8157, 8158)
DE: 5450 Orbital and rotational dynamics
DE: 8121 Dynamics, convection currents and mantle plumes
SC: Geomagnetism and Paleomagnetism [GP]
MN: 2005 Joint Assembly