something big...and old...and beautiful.

Do you know what I'm talking about?

I'm talking about a mountain!

We love climbing mountains, hiking through the mountains, and even just looking at them.

That's an interesting question, Squeaks! How do mountains form?

Well, let's start with what are mountains made of.

Mountains are made of the same stuff that we're all standing on right now, the hard, rocky

layer of the Earth's surface, called the crust.

Sounds kind of tasty! And that makes it easy to remember: The crust is the crispy, crunchy,

rocky part of Earth.

The dirt, the rocks, and all of the land on the planet are parts of the crust. And it

covers the whole Earth, even the land that's underwater.

So Earth's crust is kind of like bread crust: it covers everything in the same way that bread

crust covers the whole loaf!

But unlike bread crust, the Earth's crust isn't all in one piece. It's broken up

into pieces, called plates.

Plates that cover Earth like

a giant jigsaw puzzle.

These plates are huge, and heavy, but they don't just sit there. In fact, they're

always moving!

They move very slowly, just a tiny bit at a time, about a few centimeters a year.

But over long periods of time, all of that moving around can add up to some big changes!

Sometimes, two of the plates in the Earth's crust will move toward each other, and when

they do, they start to press against one another.

But they have nowhere to go! So they'll just push and push against each other until….they

start to crumple!

Then, the rocks that make up the plates are pushed up and over each other. The more they

push together, the more the land rises, and after a while -- voila! -- you have a mountain!

And since the plates are so huge, when they push up against each other, they don't just

make one mountain, they can make a whole mountain RANGE!

Mountain ranges like the Alps in Europe, the Andes in South America, and Appalachians in

the United States were all made this way, by two plates of the Earth's crust slowly

crashing into each other!

But because the plates move so slowly, it takes a really, really long time for this

to happen. I'm talking millions and millions of years!

And you know what's even cooler?

Some mountains are still growing!

Mount Everest, the highest mountain on Earth, grows about four millimeters every year.

And you know why? It's because the two plates that make up the land in that part of the

world are still slowly smashing into each other.

That means that the mountain is just a teeny bit taller this year than it was last year!

That's pretty amazing!

So the plates of Earth's crust are always in motion, which means that a long, long time

ago, the mountains we see today weren't there at all!

And the Earth will look different in the future, too! But it will take a really, really long time.

So the next time you're walking around on a beautiful mountain, you'll know where

it came from!

Chances are, it was made when pieces of the Earth's crust crashed into each other, and

maybe they're still crashing!

All this talk about mountains has made me ready to get out there and explore! So, Squeaks and I are

gonna hit the trails!

But remember, if you have a question about anything you'd like to learn more about,

just let us know by getting help from a grown up, and leaving a comment below. Or send us

an email to kids@thescishow.com. And we'll see you next time!