Let's Go Rock Collecting

Let's Go Rock Collecting

People collect all kinds of things. They collect coins, stamps, baseball cards, shells, toys, bottles, pictures, and cats. Some people collect things that are very old-the older the better.

The oldest things you can collect are rocks. Most of them are millions and millions of years old. Most kinds of rocks are easy to find. But some, like diamonds and emeralds, are rare. That's why they are valuable.

Rocks cover the whole earth. No matter where you live, you live on rock. There is rock under city streets and country farms. And there is rock under every ocean, lake, and river.

The Romans built roads out of rocks. The roads are still used today. Thing made with rocks last and last.

The rocks that make up the surface of the earth are called the earth's crust. Most of the crust is made of igneous rock. Igneous means made by heat. Inside the earth it is very hot--hot enough to melt rock. The melted rock is called magma. Sometimes the magma pushes through cracks in the crust. When magma comes to the surface, it is called lava. The lava cools and becomes very hard. It becomes igneous rock. Most of the earth's igneous rock comes from volcanoes on the seafloor.