(Intro)

Have you ever tried to dig a really deep hole? So deep that you thought you'd go all the way down to the center of the Earth, and come out the other side? That would be amazing, but it's also impossible. Sorry. But, what's really under ground is even cooler than what you might imagine. Let's find out what's going on inside our planet.

The Earth is made up of layers, kind of like cake or, better yet, an egg. You can think of Earth's top layer as being like the shell of an egg. This layer is called the crust, and it's what you're standing on right now. The crust covers all of Earth's surface. It includes huge, soaring mountains, the rocks and dirt under our feet, and even the land underneath the ocean. Just like the shell of an egg, the crust is the thinnest layer. It's thicker in some places than others, but generally it's between eight and forty kilometers thick, way deeper than you can ever hope to dig.

Now, have you ever cracked open an egg? The crust is kind of like that, too. It's brittle and breakable. That's because the crust is solid. It can't slosh around like water or ooze like pudding. So, sometimes when the crust moves, like in an earthquake, the crust breaks.

Now, if we keep digging down, we'll eventually hit the next layer called the mantle. What makes the mantle different from the crust? Well, first of all, it's a lot hotter, and I don't mean a sunny day at the beach kind of hot. I'm talking so hot that, even though this layer is made of rocks and minerals, those rocks actually melt, and since the mantle is made up of melted rock, this layer can move around and flow, like hot tar, bendy and slow. Sticking with our egg example, you can think of the mantle as being like the egg white. It's the thickest layer, just like an egg white takes up the most space in an egg, and it's kind of squishy like and egg white, too.

So, the rocky crust floats on top of the soft, moving mantle, and, beneath the mantle, things get even hotter. This next layer down is between 4,000 and 6,000 degrees Celsius. That's just about as hot as the surface of the Sun. This layer, called the outer core, is so hot that it's totally liquid, even though it's made of rock. 

And at the very center of the Earth, there's the inner core where, again, it's super hot, but even though it's really, really hot all the way down there, the inner core is actually solid. It doesn't move or flow like the outer core. Why? Because, at the center of the Earth, the whole weight of the planet is pressing down on it from all sides. All of this weight pushes and pushes until the very hot liquid rock has to be solid again.You can think of the outer and inner core layers as the yolk of the egg, since they're in the middle.

So, let's review our tour of the inside of the Earth. We have the brittle, rocky crust on top, the soft, bendy mantle next, the liquid outer core, and, finally, the solid, super hot inner core. If you could dig down to the center of the Earth, you'd have to get through all four of these layers, but, based on what you've learned today, do you think you could dig all the way through the Earth? If you still think you can, let me tell you about the deepest hole ever made.

The very deepest that people have ever gotten is in a mine in Russia. The hole that was dug there is 12 kilometers deep, and it took about 20 years of work to create. But the engineers digging the hole had to stop, because it just got too hot down there and their tools stopped working. And the funniest thing, at 12 kilometers deep, they weren't even close to the bottom of the Earth's crust. So, I hate to break it to you, but we won't be able to dig all the way through the planet.

But, hey! Keep digging anyway, because there's a lot more to explore under our feet. Thanks for joining us on SciShow Kids! Do you have a question about the Earth or dinosaurs or anything else, or did you just dig up something really cool in your yard? Get help from a grownup and let us know in the comments below or send us an email at kids@theSciShow.com, and we'll see you next time.