Thermal convection with non-Newtonian plates

The coupling between plate motions and mantle convection is investigated using a fully dynamic numerical model consisting of a thin non-Newtonian layer which is dynamically coupled to a thick Newtonian viscous layer. The non-Newtonian layer has a simple power-law rheology characterized by power-law index n and stiffness constant pp. A systematic investigation of steady, single cell configurations demonstrates that under certain conditions (n > 7 being one of them) the nonNewtonian layer behaves like a mobile tectonic plate. Time-dependent calculations with multicellular configurations show the ability of the plate-mantle coupling model to adjust the number of plates and their sizes in accordance with the flow in the Newtonian layer. These calculations show that the geometry and number of plates do not necessarily resemble the planform of convection below.