Erosion is the wearing away of the land surface by running water, wind, ice, or other geologic agents, including such processes as gravitational creep.

The term geologic erosion refers to the normal, natural erosion caused by geological processes acting over long periods of time, undisturbed by humans. Accelerated erosion is a more rapid erosion process influenced by human, or sometimes animal, activities. Accelerated erosion in North America has only been recorded for the past few centuries, and in research studies, postsettlement erosion rates were found to be eight to 350 times higher than presettlement erosion rates.

Soil erosion has been both accelerated and controlled by humans since recorded history. In Asia, the Pacific, Africa, and South America, complex terracing and other erosion control systems on arable land go back thousands of years. Soil erosion and the resultant decreased food supply have been linked to the decline of historic, particularly...