The Colorado Desert
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Long-nosed Leopard Lizard
The Colorado Desert is actually a sub-desert, part of the 120,000 square-mile Sonoran Desert. The Sonoran Desert covers SW Arizona, SE California, Baja, and W Sonora, Mexico. It is divided into numerous smaller parts, including the Colorado, which is the region west of the Colorado River in southern California. Some other Sonoran Deserts are the Arizona Desert, which includes Saguaro Cactus as one of its plant communities; the Anza-Borrego; and the Yuma.

Climate and Geology:
The Colorado/Sonoran Desert is the hottest U.S. desert overall. It receives most of its rainfall in the form of fall monsoons and flash flooding is common during these storms. It also receives Pacific winter storm precipitation in some areas. It is rarely, but occasionally, subject to freezing.
Topographically, it is part of the basin-and-range area, as are the Mojave and Great Basin Deserts. The ranges consist of uplifted volcanic material with large erosional plains surrounding them, merging to form bajadas. The Colorado has a few true basins (low-lying areas with no outlet for water) but in many places drainage patterns exist which eventually lead the rainfall to the Gulf of California.
Fan Palm Oasis
Plants and Animals:

The Colorado has more true trees than the other U.S deserts, excepting the pinyon-juniper stands of the Colorado Plateau. Cottonwood, Ironwood, Mesquite, Desert Willows, and Palo Verdes grow along dry washes in the arroyos and along intermittant streambeds. Understory includes creosote bush, bursage, saltbush, acacia, and a variety of cholla cactus.
Sand Verbena and Dune Primrose
Animal species include the threatened Desert Tortoise, javelinas in some places, coyotes, bobcats, raptors, and a variety of lizards and snakes.
Juniper and Phacelia campanularia on Pinto gneiss outcrop