A Captivating Look at the “Big Four” North American Deserts

Ah, the desert: the “land of little rain”, the house of haboob and flash flood, the thirsty wilderness, the barren void wandered by nomads, exiles, spiritual seekers, bandits, prospectors, and UFO hunters—plus sidewinders, scorpions, tarantulas, and vultures, of course.

Taken collectively, the deserts of North America are still overshadowed sizewise by the Sahara—at 3.6 million square miles, the greatest (non-polar) desert in the world—as well as the Arabian, the Australian Outback, and several others. But in beauty, wilderness, and ecological uniqueness they hold their own with any desertscape on Earth.

We’re going to take a dusty, sandy, squinty-eyed look at the “Big Four” of North American deserts: the Great Basin, Mojave, Sonoran, and Chihuahuan, which together cover some 500,000 square miles—from the lonesome sagebrush backlands of Oregon and Nevada, down to the cactus groves of central Mexico.

There are various ecological and climatological definitions of “desert,” a rough-and-ready one being somewhere that gets 10 inches or less of annual precipitation. A more precise one calls a desert a place where evapotranspiration (evaporation plus the water given off by plants) exceeds precipitation.

The reasons for North America’s deserts mainly has to do with rain shadow-casting mountains, distances from moisture sources, and the permanent high-pressure zones of the subtropics.

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