Mojave Desert: California, Arizona

T he Mojave Desert is a jagged, angular land of staggering extremes. It contains the lowest, hottest place in North America, a great underground river, places of bizarre beauty, a terrible earthquake fault, dead lakes, low basins, and strange and resourceful plants and animals. It occupies some 51,000 square miles (81,000 square km) and extends from the east slopes of the Sierra Nevada to the Colorado plateau before merging with the Great Basin Desert to the north and the Sonoran Desert to the south and southeast.

The two most common causes of desert combine in the Mojave to create an especially harsh and austere environment.

First, it lies along the line of latitude that spawns deserts all around the globe, due to the atmospheric circulation patterns that cause warm moist air to rise at the equator, drop its moisture in tropical rains, flow toward the poles until it cools, and downdrafts to the surface, largely stripped of moisture. Such a pattern causes deserts all around the world in both the Northern Hemisphere and the Southern Hemisphere.

Second, the Mojave lies behind walls of mountains, which force moisture-laden air from the ocean to rise, cool, condense, and lose moisture before sweeping back down the landward side of those mountain chains, further drying out the already sun-blasted landscape of the Mojave. To the east of the Mojave, the Sierra Nevadas rise to create a chain of peaks towering to some 14,000 feet (4,667 m). The Sierra Nevadas were created when the collision of two massive crustal plates caused a series of massive islands to smash into the edge of the North American crustal plate, causing the gigantic landmasses to buckle and fold. Prior to that geologic event, the western edge of North America consisted of a series of low, flat coastal plains. The ocean periodically swallowed up these great plains during warm periods when sea levels rose. This turned the low plains into a land of shallow seas, gigantic lakes, and rolling grasslands during glacial periods, when the growth of the polar ice caps locked up so much water that sea levels dropped worldwide.