Have you ever looked at a map and seen that the coasts of South America and Africa would fit together almost perfectly if you could slide them next to each other? Well, South America and Africa aren't the only continents that would fit together. The shapes of all seven continents would fit like a puzzle. Geologists, people who study the Earth, are just beginning to understand how the continents we made.

Around 220 million years ago, there were no continents, only one huge place called "Pangaea," which means "all lands" in Greek. Scientists think that Pangaea split into two parts - a northern part and a southern part - about 200 million years ago, and that those halves eventually split again and drifted to where our continents are now.

But what kind of force is strong enough to move entire continents thousands of miles across the ocean?

Scientists think it has to do with the "theory of plate tectonics." This theory says that the continents and oceans are floating on a hardened crust that lies over a thick layer of hot iron- and magnesium-bearing rock called the mantle. This mantle is hot liquid. The Earth's crust, which is the part that we all live on, is hard. It gets cracked in places and turns into pieces of crust floating on the hot liquid mantle. Their movement around the world is how Pangaea was split apart and how its pieces got to their current locations!

The United States is just one chunk of crust that split off from the original chunk called "Pangaea" and was pushed around the Earth's surface until it became the shape that we all see today. Where will it end up? Some people say that part of the state of California is moving up towards Alaska. Some people think the East Coast is going to fall into the ocean. Guess we'll just have to wait another 200 million years to find out.