In this topic, you will learn about how rocks change.

All rocks are eventually broken up. One process that helps to break up rocks is weathering. Weathering is the process that causes rocks on Earth's surface to crumble, crack, and break. Things such as chemicals, water, temperature changes, plant roots, ice, and wind can cause the weathering of rocks. Weathering is usually a very slow process. Water causes the weathering of rocks on beaches and riverbeds. When water gets into the spaces in and around rocks and freezes, rocks are broken open. Plant roots can do this, too.

Chemicals can also change rocks. Chemicals are all around you. They are in the air and water. When rocks are exposed to chemicals, the minerals in the rocks soften. Then the rocks change shape.

Weathered materials don't stay put. They are moved around by erosion. Erosion occurs when weathered materials are carried away. Erosion, like weathering, is usually a slow process. Ice, water, gravity, and wind all help to move weathered materials around. Rivers and streams carry weathered materials over great distances. Gravity can pull weathered materials down hills and mountains. Wind can pick up and move large amounts of soil and sand. Glaciers cause erosion, too. A glacier is a large mass of ice in motion. If a glacier is up high, it will move to lower land. If it is on flat land, it will spread. As glaciers move over the land they pick up weathered materials.