ABSTRACT
Rockies to the Lower Colorado river. This great area, usually known as the 'Southwest', resembles the Great Basin in many of its physical and climatic features, but the high plateaux are often more extensive and flank wider river basins. Although the highest peaks rise above eleven thousand feet, most of the country to the west is,lower-lying than the Great Basin. In the north the high plateau, which has an average elevation of over six thousand feet, has been dissected into flat-topped eminences or mesas and cliff-faced canyons. The Grand Canyon, although unique in scale and grandeur, has many minor counterparts. But to the south-west the country slopes down to the low-lying Gila basin and to the Colorado delta. Winters are less cold in this lower and more southern region, but except at high altitudes the rainfall is even lower than in the Great Basin.
