Read an Excerpt
ALL ABOUT GEOLOGY
If you want to collect rocks, it helps to know a little about geology. Geology is the study of the Earth and what it’s made of. Geology also explores the Earth’s history and how it has changed since it formed long ago.
A scientist who works in geology is called a geologist. A geologist studies rocks and minerals and everything else about the Earth beneath our feet.
Rocks and minerals are very important to understand because they make up the Earth and because we use them every day. We use rocks to build houses and walls, and we use minerals to make many things, like coins, computers, and glass. But we can also use rocks and minerals to learn amazing things, like the age of the Earth and what kinds of animals lived long ago.
Rocks and minerals are also fun to collect! By picking up rocks and writing down where you found them, you can learn a lot about geology. And you can build your collection every time you visit a new place. But you're not allowed to collect just anywhere! Check out page 126 to make sure it's OK to collect where you are. And when in doubt, ask first!
Our Earth
The Earth is always changing. The mountains, oceans, and rocks seem like they will be here forever. But they will be gone someday, and something new will be in their place. These changes happen because of the Earth’s geology.
The Earth is made up of layers. The outside of the Earth, where all the plants, animals, and people live, is called the crust. The crust is like a thin, hard shell of rock on the surface of the planet. It has all the mountains, plains, oceans, and deserts that we see, but the crust is affected by the layers beneath it.
Deeper inside the Earth, there is another layer called the mantle. It is very hot and made up of melted rock. It’s so far down that we can’t dig there. The melted rock in the mantle is called magma. The mantle’s heat is like a big oven, and all of that heat causes the crust above it to move around. Sometimes the magma pushes its way up through the crust—we call that a volcano!
Deeper down, there are even hotter layers, and some of those layers are melted and others are solid. At the very center of the Earth is a hot, solid core made of metal.
When we study geology, we look at what the Earth is made of and how the inside of the Earth moves and changes. Geology also involves how the weather can change the Earth’s surface long-term. Over a long time, wind, rain, and ice can wear down rocks, and even whole mountains can be worn away!
Inside the Earth
The Crust: The ground, mountains, and the ocean are all part of the thin outer crust.
Upper Mantle: Located just underneath the crust, the upper mantle is hot and soft because it is made up of melted rock.
Lower Mantle : The lower mantle is made of rocks that won’t melt because they’re buried too deep, even though it is very hot.
Outer and Inner Core: The outer core is so hot that everything there melts and swirls around the inner core, which is made up of solid metal!
