Geologic Erosion or "natural" erosion, is the action of the wind, water, ice and gravity in wearing away rock to form soil and shape the ground surface. Except for some stream and shore erosion, it is a relatively slow, continuous process that often goes unnoticed. Geologic erosion is reported to account for about 30 percent of all sediment in the United States each year.
Accelerated Erosion is the speeding up of erosion due to human activity. Whenever we destroy the natural vegetation or alter the contour of the ground without providing some sort of surface protection, we greatly increase the rate of erosion. This type of erosion is reported to account for about 70 percent of all sediment generated in this country each year. Accelerated erosion can be minimized through careful planning and by implementing appropriate control measures.
Farming, construction, logging, and mining are the principle causes of accelerated erosion. These activities radically upset the delicate balance that nature has developed between rainfall and runoff.