Erosion occurs as a result of wind and water moving across earth and picking up part or all of dirt or rocks. By definition, erosion only requires earth to be moved, but in most cases, rocks or land are also worn down or broken into pieces.
Erosion can be classified as either natural erosion or human-caused erosion. If the erosion is caused as a result of construction, agriculture or a variety of other human activities, it is not considered natural erosion. Erosion is not usually a good thing for the health of land since it can strip away topsoil that contains a significant number of nutrients needed to grow plants and sustain other life.