Erosion can be harmful because erosion can wash away fertile lands and create an instable ground that no longer supports roads and buildings. There are however a few benefits, if a river washes fertile lands away, the deposits could create fertile lands further downstream while the ground that has been exposed to the erosion is not necessarily infertile. The erosion of rocks, which causes it to crumble and turn to sand and clay, also creates fertile deposits by either wind or water on which plants can thrive.