Steady state, secondary convection beneath lithospheric plates with temperature- and pressure-dependent viscosity.

Presents a thermomechanical model for upper mantle convection such that the thickness and structure of the lithosphere are determined self-consistently by the heat transported by convection. In this study of the interaction between the lithosphere and upper mantle, strongly temperature- and pressure-dependent rheologies for both Newtonian and non-Newtonian creep mechanisms are employed. Evaluating the geophysically relevant observables, such as topography, free air gravity anomalies, surface heat flow, and stress fields in the lithosphere, we find that the lateral variations of these quantities predicted by a non-Newtonian rheology are much smaller than those derived frm a linear rheology. These results suggest that surface variations of geophysical observables are more compatible with a non-Newtonian rheology in the upper mantle. -from Authors