What drives the movement of Earth's tectonic plates?

• A. Gravitational pull from the moon
• B. Rotation of the Earth
• C. Erosion of the crust by wind
• D. Convection currents in the mantle

Answer: (D)

Convection currents in the mantle drive the movement of Earth's tectonic plates. Heat from the planet’s interior causes mantle rock to rise when it’s hot and sink when it cools, creating slow, circular flows in the partially molten layer beneath the crust. The lithosphere sits on top of this flow and is carried along by it, so as the mantle convection cells move, the plates ride on top of them. This system explains why new crust forms at mid-ocean ridges and why old crust sinks back into the mantle at subduction zones.

Other options don’t provide the mechanism for broad plate movement. The Moon’s gravity mainly causes tides and doesn’t push entire plates across the surface. The Earth’s rotation affects surface motion in some ways but doesn’t power the long-term drift of tectonic plates. Erosion by wind reshapes the surface but doesn’t move the thick, rigid plates that make up the lithosphere.