HR: 15:25h
AN: T13F-08    [Abstracts]
TI: Plate Tectonics is Enhanced by Continents
AU: * Grigne, C
EM: grigne@erdw.ethz.ch
AF: ETH Zurich - Institut fur Geophysik, ETH Hoenggerberg - HPP, Zurich, 8093 Switzerland
AU: Tackley, P J
EM: ptackley@ethz.ch
AF: ETH Zurich - Institut fur Geophysik, ETH Hoenggerberg - HPP, Zurich, 8093 Switzerland
AB: Plate tectonics can be obtained self-consistently in numerical models of mantle convection by using a strongly temperature-dependent viscosity, which stiffens the cold upper thermal boundary layer into a rigid lid, combined with plastic behavior above a given yield stress, which allows the lid to break into plates (e.g. Moresi and Solomatov, 1998; Tackley 2000). The plate-like regime obtained in such models can however be unstable and episodic, including periods where the yield stress is not attained anywhere in the model resulting in a global cold rigid lid. To investigate the effect of rigid continents on self-consistent plate tectonics, we introduced continents into the models by imposing one or two rigid finitely conductive lids partially covering the surface of the mantle. These heterogenous boundary conditions are found to enhance the plate-like behavior in the following ways: (i) models starting with a conductive profile of temperature in the mantle develop plate tectonics at least five times faster with continents than without. (ii) The presence of continents stabilizes plate-tectonics: once started, the plate-like regime with continents never switches back to a rigid lid regime. (iii) The convergence zones obtained in models without continents are almost vertical, unlike one-sided bending plates in subduction zones in the Earth. With continents added on top of the models, subduction zones appear to be more Earth-like, and trench roll-back is commonly observed.
DE: 8120 Dynamics of lithosphere and mantle: general (1213)
DE: 8150 Plate boundary: general (3040)
DE: 8155 Plate motions: general (3040)
DE: 8162 Rheology: mantle (8033)
DE: 8170 Subduction zone processes (1031, 3060, 3613, 8413)
SC: Tectonophysics [T]
MN: Fall Meeting 2005