What is the driving force for the movement of lithospheric plates?

The driving force for the movement of lithosphere plates is convection currents. These currents are found in the inner core of the earth and take the heat from the core to the lithosphere. Tectonic plates are able to move because of the relative density of oceanic lithosphere and the relative weakness of the asthenosphere. Dissipation of heat from the mantle is acknowledged to be the original source of energy driving plate tectonics. The current view, although it is still a matter of some debate, is that excess density of the oceanic lithosphere sinking in subduction zones is the most powerful source of plate motion.