Bill Nye explains plate tectonics and the origination of its theory. The areas in which the tectonics spread apart is where volcanoes form. Conversely, the areas in which the tectonics come together is where mountains form.
Scrat places a nut on the ground, causing the Earth to split in half. He travels down the layers of the Earth and chases the nut on the Earth's core. This clip comically shows how the different continents and many of Earth's iconic structures formed.