HR: 0800h
AN: T11C-0724    [Abstracts]
TI: Plate Motions and the Viscosity Structure of the Mantle
AU: * Stein, C
EM: stein@earth.uni-muenster.de
AF: Institute of Geophysics, Westfaelische Wilhelms Universitaet Muenster, Corrensstr. 24, Muenster, 48149, Germany
AU: Hansen, U
EM: hansen@earth.uni-muenster.de
AF: Institute of Geophysics, Westfaelische Wilhelms Universitaet Muenster, Corrensstr. 24, Muenster, 48149, Germany
AB: The viscosity structure of the Earth's mantle is likely to play an important role with respect to the motion of the lithospheric plates. A zone of low viscosity in the upper mantle has been proposed to facilitate plate motion. Another typical feature of the viscosity profile in the mantle is a significant viscosity increase at greater depth. We have employed a three-dimensional mantle convection model to explore the relation between the appearance of plate motion and the viscosity structure of the mantle beneath. With this model we further elucidate the mechanisms relevant for the formation of a low or high viscosity zone. The model allows for a complex rheology of the fluid (strong temperature, pressure and stress dependence of the viscosity) and can so account for the self- consistent formation of plates at the surface of the convecting mantle. As a general result we observe that a delicate balance between temperature, stress and pressure dependence of the viscosity is required to obtain stable plate motion and that within this balance the viscosity shows a local minimum at shallow depth (low viscosity zone) and a local maximum at greater depth.
DE: 8120 Dynamics of lithosphere and mantle: general (1213)
DE: 8121 Dynamics: convection currents, and mantle plumes
DE: 8147 Planetary interiors (5430, 5724, 6024)
DE: 8149 Planetary tectonics (5475)
DE: 8160 Rheology: general (1236, 8032)
SC: Tectonophysics [T]
MN: 2007 Fall Meeting