Where does the heat that drives plate movement originate?

• A. Heat from the Sun warms the surface to move plates.
• B. Tidal forces from Moon cause plate motion.
• C. Ocean currents drive plate movement.
• D. Heat from the outer core heats the lower mantle, driving plate movement.

Answer: (D)

Mantle convection driven by internal Earth heat powers plate movement. The outer core is extremely hot, and heat flowing into the lower mantle creates convection currents in the mantle: hot rock rises, cool rock sinks, and these slow, large-scale motions push and pull the overlying lithospheric plates. This internal energy comes from radioactive decay and residual heat from Earth's formation, not from the Sun or surface processes. The Sun heats the surface, and tides or ocean currents affect near-surface phenomena, but they don’t drive the deep mantle flows that move tectonic plates.