You've seen a map of the world: seven continents and one global ocean, divided into five regional segments.

But the Earth didn't always look like this.

Why are continents so big?

Scientists think that around 200 million years ago, there actually used to be an even bigger continent.

In fact, the whole Earth had just one supercontinent.

It was called Pangaea.

Well, back then, there were no humans around to call it anything.

But we call it Pangaea now.

Pangea means all the Earth.

If you look closely at that map, you can kind of see how these big continents might have fit together, like a puzzle, to form one gigantic landmass.

So how did they break apart?

Here's where we introduce the theory of plate tectonics, which goes like this: The Earth's crust is made up of about 20 massive slabs of rock.

We call those tectonic plates.

And because the Earth's core is unbelievably hot, it heats up the magma underneath those plates.

As the magma heats and cools, the plates slowly move around.

Which is how we ended up with a map of the world that looks like this.

But the thing is, tectonic plates are still moving.

Sometimes they move towards each other, which causes earthquakes.

Sometimes they move away from each other, which causes earthquakes.

And sometimes the plates slide past each other, which also causes earthquakes.

But the fact that the plates are still moving today also means that the map of the world is always changing, just too slowly for us to notice in real time.

Since our Earth is a sphere, continents can't drift apart forever without running back into each other.

But don't worry, they only move a few centimeters a year.

So you've got, oh, about 250 million years before that happens.

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