United States

Land

The two great sets of elements that mold the physical environment of the United States are, first, the geologic, which determines the main patterns of landforms, drainage, and mineral resources and influences soils to a lesser degree, and, second, the atmospheric, which dictates not only climate and weather but also in large part the distribution of soils, plants, and animals. Although these elements are not entirely independent of one another, each produces on a map patterns that are so profoundly different that essentially they remain two separate geographies. (Since this article covers only the conterminous United States, see also the articles Alaska and Hawaii.)

The Colorado River in Marble Canyon at the northeastern end of Grand Canyon National Park, northwestern Arizona.© Gary Ladd