What process drives the movement of the Earth's plates?

• A. Mantle convection
• B. Spreading ridge
• C. Subduction
• D. Gravity

Answer: (A)

Mantle convection is the engine behind plate motion. Heat from Earth's interior makes the mantle rock rise where it’s hot and sink where it’s cool, creating slow, circular currents in the semi-fluid layer beneath the lithosphere. These convection currents push and pull on the overlying tectonic plates, causing them to move at their boundaries—ridges where new crust forms and subduction zones where crust sinks back into the mantle. Surface features like spreading ridges arise from these upwellings, but they’re a consequence, not the driving force. Gravity does influence how slabs sink and how material moves, but the overall driver of plate movement is the mantle’s convective circulation.