Answer:
Step-by-step explanation:
The force of density, more specifically the force due to density differences is what drives tectonic plates. Density difference throughout the mantle is due to variations in its temperature. Warm areas expand, become less dense and rise while cold areas sink.
For example, continental plates are thick and light but its material erodes. When it becomes sea-floor sediment, its density increases and is then subducted with the oceanic plate.