Long ago, people used to think the Earth was flat. They believed if they sailed a boat far out into the ocean, the boat would fall off the Earth! Now people know that this is not true. We know the Earth is not flat. It is shaped like a ball. The Earth only looks flat to us because it is so large. We can only see a small part of the Earth's surface when we are standing on it. Have you ever wondered what the Earth is like underneath the surface?
Have you ever seen a peach that has been cut in half? If we could see inside the Earth, it would look very much like a peach. The Earth has four layers. The outer layer of the Earth is called the crust. The crust of the Earth is like the skin of a peach. The skin on the peach is very thin. It is only a small part of the peach. The crust of the Earth is also very thin. It is only a small part of the Earth. The crust is the Earth's thinnest layer.
The crust is made up of rocks and soil. The land you walk on and the land on the bottom of the ocean make up the Earth's crust. The crust under land is thicker. The crust under the ocean is thinner. The crust is made up of many large pieces called plates. When two plates push toward each other, mountains can form on the Earth's crust.