Effect of a moving lithospheric plate on convection in the earth's mantle
Thesis/Dissertation
·
OSTI ID:5375135
The coupling between a rigidly-moving lithospheric plate and a convecting mantle is investigated using a simple two-dimensional numerical model. The model incorporates a fluid layer heated from below or heated internally and acted upon by a horizontally-moving upper boundary, simulating the effect of a moving plate. For both heating from below and internal heating, the moving boundary strongly controls the horizontal length scale of convection cells when the boundary velocity is greater than the free convective velocities. When the entire upper boundary moves, in a box of aspect ratio 4 (width/depth), a transition in flow structure occurs from several equidimensional convection cells under a slowly-moving boundary to a single long convection cell under a rapidly-moving boundary. For heating from below, this flow transition occurs approximately when PeRa/sup -2/3/ = 0.04. The Peclet number, Pe, measures the (prescribed) velocity of the upper boundary, and the Rayleigh number, Ra, measures the heating of the fluid layer. A model that has half of the upper boundary moving and the other half stationary simulates flow beneath a plate convergence zone. The results of this simple model suggests an inverse correlation between the dip of Benioff seismic zones and the parameter PeRa/sup -2/3/. This study indicates that mantle convection and lithospheric plate motions are strongly coupled. The rigidly-moving plates strongly control the flow structure in the mantle. Single cells are likely under the faster driving forces on the plates.
- Research Organization:
- Rochester Univ., NY (USA)
- OSTI ID:
- 5375135
- Country of Publication:
- United States
- Language:
- English
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