Another physical process is called erosion. Erosion in all of its forms reshapes landforms and coastal regions, as well as riverbeds and riverbanks. Erosion occurs when weathered material is moved by the action of wind, water, ice, or even gravity. For erosion to take place, a transporting agent (such as water) must be present.

Erosion involves material moving from one location to another resulting in the lowering of some locations and increasing in elevation in others. For example, water might carry topsoil from a hill into a river and gradually cause the river to become narrower. Glaciers, waves, stream flow, or blowing winds cause erosion by grinding rock into smaller pieces.

Activity

Analyze the following examples of erosion and try to determine the causes of the each one:

Video segment. Assistance may be required. Watch the following video that shows coastal erosion in a 4-week time lapse at Drew Point, Alaska.

Source: Drew Point, Alaska Time-Lapse Photograph of Coastal Erosion, USGS, YouTube

Photo of the bank of the Missouri River. The bank is made of rock and is erosion is evident. There are pieces of rock that are broken; there are ridges that indicated that water has reached various levels. Above the bank there is a tiny image of grass and trees.

Source: Bank Erosion, U.S. Geological Survey

This is a photo of an active bank erosion on the right bank of the Missouri River, located southwest of Brockton, Montana.

Image of a cliff from the St. Elias mountain range in Alaska. There is snow above and below the cliff and a water fall made of the ice water coming from the top of the mountain falls down the side of the cliff to the mountains below. The cliff has evidence of erosion: the rock is various shades and the textures.

Source: Rapid Erosion, Shad O 'Neel, U.S. Geological Survey

This is a photo of the St. Elias Mountain Range in Icy Bay, Alaska. This area is known for having some of the fastest erosion rates on Earth.