(Crash Course Kids Intro Plays)

This is Earth. Home to +7 billion people, 7 continents and all kinds of amazing plants and animals, this is what Earth has looked like for a long time and will probably continue to look like for a long time. Right? 

Yes and no, sure. This is what Earth looks like from space. But even though it looks pretty much the same from whenever we view it from afar, once you zoom in on it, you can see that it's always changing. On a small scale, things like moving water shape the Earth's landforms - the natural features of the Earth's surface. On a bigger scale, the gradual shifting of the Earth's crust is slowly moving even bigger things, like the oceans and the continent. 

So one day, our planet will look different, maybe a lot different from how it looks now. So, how exactly does water shape the Earth's landforms? Or to bring it back to the hydrosphere we've been talking about, how does the hydrosphere affect the geosphere? 

To understand that, we need to discuss weathering. I'm not talking about the weather, like if it happens to be sunny or cold or foggy outside your window right now. I'm talking about weathering, the process that takes place as rocks, and other parts of the geosphere, are broken down into smaller pieces. Weathering can be caused by water, air, chemicals, plants, or even animals, including us.

There are 2 types of weathering that you need to know about - mechanical weathering and chemical weathering. Mechanical weathering is the process of breaking big rocks into little ones. Frost, ice, the roots of plants, running water or heat from the sun can all cause mechanical weathering. Chemical weathering involves changes that some substances can cause in the surface of the rock that make it change shape or color. Things like Carbon Dioxide, Oxygen, and acids can all cause chemical weathering. 

When rocks have been weathered, all broken down, and are later moved by natural forces, like wind, water, or ice, that's called erosion. Weathering and erosion sound pretty similar, right? Well, yeah, but not exactly. Think of weathering as the hammer that breaks down the rocks and erosion is the process that carries those rock fragments away. Or I'll put it in a way that we're all familiar with - weathering helps make a mess and erosion helps clean it up. 

Let's take a trip to the beach to see what part the hydrosphere plays in weathering and erosion. This is a picture taken from space of the coastline of Massachusetts in the Northeastern United States. It's part of a landform called Cape Cod and the picture shows what the beaches and islands looked like in 1984. Now look at this photo from 2014. What's the difference? There are actually more islands in 2014 than there were before. Back in 1984, that long strip of land was North Beach. Now, that strip of land has been chopped up into separate islands. The top part is North Beach, the middle area broke off into North Beach Island, and the bottom part is now called South Beach. 

So, how did that happen? Well, moving water is a major cause of erosion and there's a lot of moving water in the Atlantic Ocean. The intense energy of ocean waves crashing on shore cause the pieces of the rocky, sandy, coastline to break into smaller pieces or to weather over time. Then, natural forces like major storms and rising sea levels move, or erode, these smaller pieces. Day to day, you might not notice any dramatic changes, but over the course of 30 years, well as these pictures show, coastlines can change a lot.

So, what can we take away from this? Well, we saw that water can weather and erode Earth's landforms, and that's just one example. There are so many others like floods weathering valleys or glaciers eroding mountains. Let me break it down for you this way (see what I did there ;) ). The hydrosphere shapes and sometimes moves the geosphere. One last joke before I sign off, what did the geosphere say to the hydrosphere? You crack me up. 

(Crash Course Outro Plays)