(0:00) (Intro)

(0:10) Remember when we were putting together the puzzle that is our planet, using the four spheres as giant pieces? Well we got pretty far last time, but we're not done yet. Oh, no.

(0:20) That's because in addition to the geosphere and the biosphere, which we talked about last time, there are two more spheres that we need to complete our planetary puzzle. Those are the hydrosphere and the atmosphere. So without further ado, let's dive in! See what I did there?
(0:37) I said that because the first sphere we're going to talk about is the hydrosphere. 'Hydro' comes from the Greek word for 'water', and all of the water on Earth is in the hydrosphere. This means that every single drop of salt water in the ocean, but also all the fresh water in lakes and rivers, is in this sphere. And it includes all of the water trapped in glaciers as ice, and the water held deep underground.

(0:59) Now, there's also water in the air around us, too, which we can sometimes see in the form of rain and snow. Those things come from clouds which happen to be way up in the atmosphere, our last but certainly not least sphere. This sphere contains all of the gases on the planet, which is fitting since 'atmos' comes from the Greek word for 'air'. Although we can't really see the atmosphere or grab onto it, it reaches everywhere and covers the entire planet like a giant snuggly blanket.
But our atmosphere blanket isn't all the same. It's split up into many different layers. The troposphere is the lowest layer; it contains 80% of the air on the planet. It's also where all of our weather takes place. Above the troposphere is the stratosphere; there's no weather up there and much less air but there's still important gases in it that help absorb harmful rays from the sun. The mesosphere is the coldest layer of the atmosphere, and sits on top of the stratosphere. There's almost no breathable air up there; and even less in the thermosphere above it, where you might bump into some satellites flying around the planet. The last layer of the atmosphere is the exosphere; that's the highest you can go and still be on Earth. Once you leave the exosphere you're officially in space, baby!

(2:18) Now, these two spheres can be kind of difficult to tell apart. So let's investigate. At the beach!
(Investigation graphic)
The beach is the perfect place to closer look at what pieces of our environment make up the hydrosphere and which are parts of the atmosphere.
The beach is, of course, right next to the ocean, and since the ocean holds most of the water on our planet it's the biggest part of the hydrosphere. The rivers that flow into the ocean are also a big part, and so is the rain that's just starting to fall on our beach. Well, that's a bummer. But check this out: while the rain is part of the hydrosphere, the clouds it came from are actually part of the atmosphere. And the wind that pushes the waves around is part of the atmosphere, too. Even though we can't see it, the atmosphere is all around us in the form of the air that we breathe.

(3:06) (Conclusion graphic)

Our planet couldn't be the amazing place we know it to be without the four spheres! And it can be a tough puzzle to put together, but the result is pretty amazing, I think you'll agree.