Earth’s surface is affected by many types of erosion. Pounding waves grind rocks and shells into sand. Gravity can cause landslides, which occur when rocks are shaken free by heavy rain or earthquakes. After a heavy rain, when the soil is soaked, mudflows can result. Running water causes the greatest changes to Earth. The flow of rainwater picks up particles of rocks and soil. These particles can cut a valley in the bedrock. The particles picked up by running water are eventually placed far from the original location changing Earth’s surface.