The transition from the hot
Sonoran Desert to the cooler and higher
Great Basin is called the Mojave Desert. This
arid region of southeastern
California and portions of
Nevada,
Arizona and
Utah, occupies more than 25,000 square miles. On the
northwestern boundary it extends from the
Sierra Nevada range to the
Colorado Plateau in the east; it abuts the
San Gabriel-
San Bernadino Mountains in the
southwest.
Average annual precipitation: less than 5 inches, almost
all of which arrives in winter. The Mojave has a mountain-and-basin topography with sparse vegetation. Sand and gravel basins drain to central salt flats from which borax, potash and salt are extracted. Silver, tungsten, gold and iron deposits are also worked.
The Mojave Desert hosts about 200 endemic plant species found in neither of the adjacent
deserts. Cacti are usually restricted to the coarse soils of bajadas. Mojave Yucca and, at higher elevations Desert Spanish Bayonet, a narrow-leafed yucca, are prominent. Creosote Bush, Shadscale, Big Sagebrush, Bladder-sage, bursages and Blackbush are common shrubs of the Mojave
Desert. Occasional Catclaws grow along arroyos. Unlike the Sonoran Desert, trees are few, both in numbers and diversity, with the exception is the Joshua tree, occuring only at higher elevations in this desert and only in this desert.
How to tell if when you're in the Mojave if you're an ignorant city person like myself:
If you're in the area bordered on the south by Interstate 10 in California, on the west by California's U.S. Route 395, on the North by U.S. Route 50 in Nevada, and on the east by Interstate 15, you're in the Mojave.
Source: http://www.desertusa.com