Erosion

The average rate of erosion at the surface of Earth is about 1 in (2.5 cm) per thousand years. However, the rate of erosion varies tremendously from place to place. Soil erosion in some areas exceeds one inch per year—one hundred times its rate of formation. This range in rates is dependent on several different controlling factors. These factors include the type and amount of plant cover and animal activity, the climate, the nature of surface materials, the slope angle, and human land use. However, many of these factors routinely help increase erosion in some ways, while decreasing it in others. In addition, a complex interplay between the different factors may exist. For example, a particular combination of surficial materials and plant cover may accelerate erosion in one climate, while decreasing it in another. The individual controls can be difficult to recognize and their effects difficult to discern as well.