(Intro)

Hi guys. Squeaks and I are getting ready to go one a hike, and today we're going to explore 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.

*squeaks* That's an interesting question, Squeaks. How do mountains form? Well, let's start with what mountains are made of. Mountains are made of the same stuff 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 under water. 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 Earth's crust will move towards each other. And when they do, they start to press against one another, but they have nowhere to go. So, they will 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, viola! 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 the 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, do 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 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 going to hit the trails. But remember, if you have a question about anything you'd like to know more about, just let us know by getting help from a grownup, and leaving a comment below or send us an email at kids@thescishow.com and we'll see you next time.