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Physiography
The Mojave Desert is the southwestern part of the Basin and Range physiographic province, a vast region of steep mountain ranges and alluvium-filled basins that extends from northern Nevada to Mexico and from California's Sierra Nevada and southern coastal areas into central Arizona and Utah. The Mojave Desert is transitional between the lower, hotter Sonoran Desert to the south and the colder high desert of the Great Basin to the north. The Mojave Desert has very large diurnal temperature fluctuations and receives less rainfall than most other desert regions in North America. Winter months are often marked with freezing temperatures, especially at higher elevations. The summers are hot, dry, and windy. The average annual precipitation is less than 12 cm; however, it does have huge variability year in and year out. The greatest amount of precipitation occurs during the winter. However, this area does experience occasional intense thunderstorms in the summertime-these extraordinary instances of flooding cause some of the most dramatic changes within the desert landscape.The Mojave National Preserve contains an eastern section of the vast Mojave Desert ecosystem. It takes up around 1.6 million acres, with most diverse landscapes like steep mountains, canyons, volcanic terrains, alluvial fans, sandy dunes, and arid lake basins. In 1994, the U.S. Congress established the Mojave National Preserve through the action of the California Desert Protection Act.
Elevations in the Preserve range from a high of Clark Mountain (7929 feet; 2417 m) to a low point at Soda Lake (932 feet; 284 m). Other high upland areas include portions of the Granite, Providence, and New York mountains. Ecological habitats vary with the landscape and precipitation: pinyon-pine forests and frost-tolerant species occur above 5,500 feet (1675 m) where average precipitation is as much as 25 cm (some of which falls as snow); Joshua-tree forests occur in the range of 4,000 to 6,000 feet (1220 to 1828 m); mixed desert shrub communities exist in the middle elevation regions and along the mountain range fronts, and; creosote bush and other drought-tolerant species survive in the lower elevation regions where rainfall averages less than 5 cm per year.
Mountains and Basins.
Mountains impede travel across the desert, whether by pioneer wagon or sportscar. Likewise, the mountain ranges delineate the landscape and serve as barriers to the migration of sediments (carried both by water and wind). Adjacent to each range are corresponding valleys that are filled with sediments. The Mojave Desert region is within a great inland (isolated) drainage basin. For almost 10 million years, rivers have continually drained into the ocean. During the past Ice Ages, enormous lakes filled many lower valleys; many of these lake basins overflowed into adjacent valleys, some eventually overflowing into Death Valley. However, like the current interglacial period, the region has dried, uncovering large dry lakebeds exposed to wind erosion. Between the ranges and the lakebeds lie areas of coalescing alluvial fans (the bajadas) or large areas of nearly flat, treeless, weathered bedrock (the pediments) where mountains most likely existed long ago but which have long since been eroded. ---Introduction
Physiography
Weather Data
Geologic History
Changing Climates
Weathering & Erosion
Carbonate Rocks
Granitic Rocks
Volcanic Rocks
Faults
Pediments
Stream Channels
Stream Terraces
The Mojave River
Playas
Sand Dunes
Human Impacts
References
NPS photo
This zoomed-in view is looking southwest along the Interstate 15 corridor from the top of Turquoise Mountain (just east of Baker, CA). The view incompasses portions of Silver and Soda dry lakes (near Baker in the foreground), the Soda Mountains across the middle, and the large, distant Cave Mountain.
NPS photo
A high-altitude, oblique-view aerial photograph of the Mojave National Preserve region taken in September of 1968 with a view to the southwest. Note how the landscape is dominated by bajadas (coalescing alluvial fans) formed from the accumulation of sediments around erosionally dissected-mountain ranges. Ephemeral streams connect to dry lakebeds (playas) in the lowest valley regions.
NPS photo
Cedar Wash cuts through a Joshua tree covered landscape of a broad alluvial apron (a bajada) grading down slope from the Providence Mountains (left) to the main valley drainage, Kelso Wash (to the right). In the distance, Kelso Dunes blanket the valley beneath the distant high peaks of the Granite Mountains (upper left). Note the different color and texture of the broad wash - created by a different vegetation assemblage.
