Date of this Version
For most Americans, "The Great Plains" evokes images of grasslands, dust storms, prairie fires, Indians on horseback, cowboys and wheat lands, and perhaps flat valleys crossed by braided rivers carrying a heavy load of sand and gravel, extremes of weather, and a climate typified by an alternation of droughts and wetter periods. Geologists picture such general images, too, but they also see radical changes in the landscape over periods expressed in millions rather than hundreds of years. Geologically speaking, human activities on the Great Plains are too recent to have much of a place in the broad geologic history of the region, but they have certainly influenced both the use and the appearance of the region today and hence the terms in which we understand it. Fire was one of the first human technologies to affect the Plains, and it favored the development of some types of vegetation, particularly grasses, over others, such as woody plants. Farming and ranching have had vast impacts on the vegetative cover, on the soils, and on wildlife distribution. And dams, built across rivers to control flooding, to produce hydroelectric power, or to divert water for irrigation or other uses, have produced major changes in the behavior of the rivers.