Desert Southwest Regions: Sonoran, Mojave, Chihuahuan, Great Basin

The North American Desert Southwest comprises four distinct deserts, each with unique ecology and geography:

1. Sonoran Desert

Area: ~260,000 km² (100,000 mi²). Location: Southern AZ, SE CA, NW Mexico. Icon: Saguaro cactus (up to 15 m / 50 ft). Climate: Bimodal rain (winter fronts + summer monsoon); hottest US desert.

2. Mojave Desert

Area: ~65,000 km² (25,000 mi²). Location: SE CA, S NV, SW UT, NW AZ. Icon: Joshua tree (Yucca brevifolia). Climate: Driest NA desert; winter rain, rare summer storms. Death Valley (lowest, hottest) is here.

3. Chihuahuan Desert

Area: ~450,000 km² (175,000 mi²)—largest in NA. Location: S NM, W TX, N Mexico. Icon: Creosote bush, lechuguilla agave. Climate: Summer monsoon dominant; higher elevation (600–1,500 m) = cooler winters.

4. Great Basin Desert

Area: ~520,000 km² (200,000 mi²). Location: NV, W UT, S ID, SE OR. Icon: Sagebrush steppe, bristlecone pines. Climate: Cold desert—high elevation, winter snow, rain shadow of Sierra Nevada.

These deserts overlap transition zones (ecotones) and are separated by mountain "sky islands" that harbor relict forests. Together they define the Southwest's arid heart.