Erosion is usually a slow and gradual process that takes thousands or even millions of years. But man's activities such a farming, mining, and urban development can speed up the erosion process. Erosion begins with the weathering, or breaking down, of rocks and soil. Chemical processes like carbonation or acid rain, and physical processes like freezing and the pull of gravity can cause weathering to occur. Once rocks and soil are broken down, wind and water can erode the landscape and carry the loose rocks and soil away.
Water runoff is the major cause of erosion.
Runoff is water that flows over the earth's surface. It picks up and carries weathered rocks and soils to other places. It also creates many features on the earth's surface. Rivers cause erosion by transporting weathered rock and soil downstream. The Grand Canyon is one spectacular feature that was created by river erosion.