In order to talk about the Earth's moving plates, we needed to talk about why the Earth's plates are moving. Convection currents in the Earth's mantle are what drive plate motions. Convection currents are driven by the simple facts that hot things (such as gases and liquids) rise while cool things fall.

Convection currents in action! At left, two animal cookies represent two of the Earth's tectonic plates. At right, the two plates have moved apart, much like what happens at a divergent margin. The chocolate pudding represents the Earth's mantle. The heat source beneath the pot created convection cells in the chocolate pudding. Think of the cookie on the left as South America, and the cookie on the right as Africa. Over time they have moved apart. You'll see this again.

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