Physiographic Boundaries Within The United States PDF Download

Purchase of this book includes free trial access to www.million-books.com where you can read more than a million books for free. This is an OCR edition with typos. Excerpt from book: PHYSIOGRAPHIC REGIONS OF THE UNITED STATES. By J. W. Powell. Of a country so large as the United States no adequate physiographic description can be given within the limits of a monograph of this size. The purpose here is to define the great slopes, and then a greater number of physiographic regions, which are again divided into districts, and to indicate some of their more important characteristics. Three of the regions have been selected for a somewhat more elaborate description, ?one of plains, one of plateaus, and one of mountains, ? thus illustrating briefly all three types. These regions are the Atlantic Plains, the Colorado Plateaus, and the Pacific Mountains, taking the eastern, a midland, and the -western region. It will be noticed that an old custom of describing great physiographic regions in units of basins has not been followed. Against that plan there are insuperable objections. Where there are large rivers, there are large basins, and such are again subdivided into ever smaller and smaller basins; and where there are oceans and gulfs, there are many small disconnected basins; so that the basin unit divides the country into very unequal parts, and fails to exhibit the association of great features that are intimately connected in physiographic history. Gradually, as the new science of physiography has grown, physiographic regions have come to be recognized; and an attempt is here made, by map and verbal description, to define the principal regions of the United States, exclusive of Alaska. The regions here delineated are held to be natural divisions, because in every case the several parts are involved in a common history by which the present physiographic features have (Copyright, 1895, by American Book Company.) 65 been developed. They have been ..