What are the driving forces for plate movement?
What will be an ideal response?
F1: Mantle drag or friction between the convecting asthenosphere and the overlying rigid lithosphere
F2: The gravitational "push" generated by the high topography of a mid-ocean ridge on the rest of the oceanic plate
F3: The increasing density of the oceanic lithosphere as it cools, which pulls the opposite end of the plate into a subduction zone
F4: The elastic resistance of the oceanic plate to being bent into a subduction zone
F5: The tendency for the overriding plate to be drawn toward a subduction zone as the subducting slab bends (which otherwise would move the trench away from the overriding plate)
F6: Friction between the subducting slab and the overlying lithosphere
F7: A tendency for the oceanic plate to sink as it cools and becomes denser
The overall motion of a given plate is the result of the balance of all these forces.
Analysis of plate motions today argues for a predominant role played by the push of the ridges and the pull of the subduction zone, but in the past, mantle drag may have played a more important role in the rifting apart of supercontinents.
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