Water erosion is a natural process that occurs whenever water transports soil, rock, sediment, or any dissolved material from one place to another. Since erosion occurs whenever the flow of water is greater than the strength of the sediment’s ability to resist it, loose and sandy sediments are more susceptible to erosion than clay or rock. Rainfall and any accompanying surface runoff results in four main types of soil erosion: splash erosion, sheet erosion, rill erosion, and gully erosion. Imagine a drop of water falling into a pan of sand, creating a small crater as it displaces the sand from the point of impact. This displaced sand is a result of splash erosion. As water continues to fall on the pan of sand, water infiltrates the sand until it becomes saturated. If you tilt the pan, creating a slope, some of the sand from the top layer will be carried by the water. This is sheet erosion. As the water continues to rain down on the pan of sand, small channels might form. These are known as rills. As the flow of water becomes stronger, some of these rills might become deeper and more defined channels. As water carves deeper channels into the sand, these deep channels are known as gullies.
Another type of erosion is wave erosion. As waves of water from a large body of water or ocean collide with the surrounding landscape, sediment is carried away by the continuous rushes of water. The degree of erosion depends on the type of material, the strength of the waves, and the amount of time that has passed. Over thousands of years, ocean waves can carve into the land and form cliffs.
Glaciers, basically large chunks of ice, also contribute to erosion. As water freezes, especially at higher and colder altitudes, rocks and soil can be carried away by the slow-moving ice (or fast moving ice in the case of an avalanche). This process is known as abrasion or scouring. As ice penetrates surrounding rock and bedrock, pieces may break off and be carried away in a process known as plucking. Glacial ice may also freeze and adhere to the underlying bedrock, breaking it off and carrying it with it. This is known as ice thrusting.
While erosion is the process of moving sediment, soil, and rocks; deposition is the process of adding those materials to a landform. As the kinetic energy of the eroding water lessens, earth materials are left behind. It is through this process that some landforms are created.