Differentiate  between sheet erosion and gully erosion.

Sheet Erosion: When water flows as a sheet down a slope and as a result, the top part of the land is washed away, such an erosion is called sheet erosion.

Gully Erosion: When the running water cuts through the clayey soils and makes deep channels as gullies, then such an erosion is called gully erosion. The Chambal ravines are the result of such gully erosion.