basin and range
The extension or stretching of the Earth’s crust normally results in downfaulted valleys, or grabens, and upfaulted mountains, or horsts. North America’s huge geological province of north-south–oriented mountains and valleys created in this way is known as basin and range country (roughly 400,000 square miles) and runs between northern Mexico and southeastern Oregon, and the Sierra Nevada of California and the Wasatch Mountains of Utah. It includes parts of all the major North American deserts—the Great Basin, Mojave, Sonoran, and Chihuahuan. Death Valley, on the Nevada-California border, reaches a maximum of 282 feet below sea level, while the Panamint Mountains just to the west rise to some 11,000 feet in elevation. At the foot of such snowy ranges as the Ruby Mountains in Nevada and Steens Mountain in Oregon, peat-bog marshes form despite the aridity of the basins, providing havens for migrating waterfowl. Runoff from Steens Mountain ﬂows through glacial valleys to the Malheur National Wildlife Refuge and drains into a series of alkaline playas where the waters evaporate.