As long as the winds blow and rain falls, erosion will continue to take place. How is erosion useful to man and when does it become a serious problem?
Erosion works with weathering. Erosion works hand in hand with the process of weathering in causing rocks to be broken up and changed into soil. It is the agents of erosion that carry away this newly formed soil and expose fresh rock surfaces to the agents of weathering. Thus new rock surfaces are exposed to the air, to rapid changes in temperature, to the pounding rain and driving wind, to dissolved chemicals in ground water, and to the other agents that help in making more soil. This transported soil often ends up in the fertile river valleys and plains where we find our most productive farmlands. In this process of transporting new soil and minerals from where they have been made to where they can be used, erosion is useful to man.
Winds cause dust bowls and sand dunes. Winds erosion in semi-arid regions may remove millions of tons of fine topsoil from fertile fields. In the Dust bowl area of the Great Plains such dust storms during the long fry spells known as droughts have caused tremendous losses and many farms have had to be abandoned. In other areas wind-blown sand forms dunes which may bury fertile farms, forests, and sometimes even towns. It is obvious that erosion by the action of winds is most effective where the soil is bare and unprotected by natural vegetation. Even more effective than winds as an agent of erosion is water.
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