Erosion

The energy for erosion comes from five sources: gravity, the Sun, Earth's rotation, chemical reactions, and organic activity. These forces work together to break down and carry away the surficial materials of Earth.

Gravity exerts a force on all matter, Earth materials included. Gravity, acting alone, moves sediment down slopes. Gravity also causes water and ice to flow down slopes, transporting earth materials with them. Gravity and solar energy work together to create waves and some types of ocean currents. Earth's rotation, together with gravity, also creates tidal currents. All types of water movement in the ocean (waves and currents) erode and transport sediment.

Solar energy, along with gravity, produces weather in the form of rain, snow, wind, temperature changes, etc. These weather elements act on surface materials, working to decompose and disintegrate them. In addition, chemical reactions act to decompose earth materials. They break down and dissolve any compounds that are not stable at surface temperature and pressure. Organic activity, by both plants and animals, can also displace or disintegrate sediment. An example of this is the growth of a tree root moving or fracturing a rock.