THERMAL AND MECHANICAL INTERACTION OF CONTINENTS WITH THE MANTLE

Abstract

Thermomechanical interaction between the mantle and continents strongly affects mantle convection patterns. We present a numerical study of this interaction. Numerical models of mantle convection with free-floating rigid continents must include boundary conditions at mantle-continent interfaces. We state these conditions using solutions at successive time steps $\Delta t$. First, with fixed positions of continents, thermal convection is calculated for the whole region excluding the continents; then the instantaneous velocity $V$ of their displacement can be obtained. At the next time step mantle convection is calculated with the new positions of continents now shifted by the distance $V\Delta t$. No-slip conditions at the mantle-continent interface cannot be used, because $V$ equals zero in that case. We suggest boundary conditions at mantle-continent interfaces where velocities of the continents are accepted to be equal to the mean velocities of the mantle flow at their lower boundaries. These conditions proved to be satisfactory and significantly simplified the solution procedure. We compare two models differing in boundary conditions for the stream function at the mantle-continent interfaces. We obtained regions of excessively high heat flow between subduction zones and moving continents for both models. These models are appropriate for explaining the process of marginal basin formation.

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Computational Seismology, Vol. 3.