Driving mechanisms for plate tectonics

Abstract

It is generally accepted that some form of thermal convection drives plate tectonics. The driving force can act within the plate or can be transmitted to the plate from below. forces acting within the plate arc: I) the negative buoyancy and elevated phase boundary in the descending plate and 2) gravitational sliding of the plate off the ocean ridge. Both of these forces can be calculated with reasonable accuracy. Forces transmitted to the plate by shear stresses acting on its base are much more difficult to evaluate. The form of the convective flow in the mantle is not known and estimates of viscosity may be in error by orders of magnitude. It is only possible to speculate whether such forces contribute significantly to driving plate tectonics.