Why do tectonic plates slide around next to each other?

Why do tectonic plates slide around next to each other?

• A. Gravity from the Moon
• B. Solar heating
• C. The heat of the Earth's interior
• D. Ocean surface drag

Answer: (C)

The movement comes from heat inside the Earth driving convection in the mantle. The mantle is hot enough that its rock can flow slowly, with hot material rising and cooler material sinking. This circulating motion creates flow in the layer beneath the lithosphere, so the rigid plates on top are dragged along as they ride on that partly molten layer. Over this long timescale, the heat from the Earth's interior (from radioactive decay and residual formation heat) powers the whole system, causing the plates to move relative to one another. Other options don’t provide the energy source for this big movement: the Moon’s gravity, solar heating, or drag at the ocean surface are far too weak or not located to drive the solid plates themselves. The internal heat and mantle convection are what genuinely push and pull the plates across the globe.

The movement comes from heat inside the Earth driving convection in the mantle. The mantle is hot enough that its rock can flow slowly, with hot material rising and cooler material sinking. This circulating motion creates flow in the layer beneath the lithosphere, so the rigid plates on top are dragged along as they ride on that partly molten layer. Over this long timescale, the heat from the Earth's interior (from radioactive decay and residual formation heat) powers the whole system, causing the plates to move relative to one another.

Other options don’t provide the energy source for this big movement: the Moon’s gravity, solar heating, or drag at the ocean surface are far too weak or not located to drive the solid plates themselves. The internal heat and mantle convection are what genuinely push and pull the plates across the globe.