What primarily moves the tectonic plates?

• A. Slab pull
• B. Ridge push
• C. Convection in the mantle
• D. Isostatic rebound

Answer: (C)

Mantle convection drives plate motion. Heat from Earth's interior causes mantle rocks to rise where they are hot and sink where they are cooler, creating slow, circulating currents in the mantle. The lithosphere sits atop the weaker asthenosphere and is carried along by these convection flows. This global circulation sets the surface plates in motion, so their movement is best explained by convection in the mantle.

Slab pull and ridge push are important components of how plates interact. Slab pull is the gravity-driven force from a cold, subducting plate pulling the rest of the plate downward, and ridge push is the gravitational sliding away from elevated mid-ocean ridges. Both are consequences of the mantle convection pattern and surface topography, not the primary cause on their own. Isostatic rebound is vertical adjustment in response to loading or unloading, not the horizontal movement of tectonic plates.