Mojave Desert - Essay Example

Although every desert has distinct vegetation, most have the same basic geological structures. This is true of the Mojave and its southwestern counterparts - the Great Basin, the Sonoran Desert and the Chihuahuan Desert. Extreme variation in temperatures and an average rainfall of less than six inches are characteristic of the Mojave desert. Alluvial fans, playas, hoodoos, and sand dunes are common features. Alluvial fans are found at the base of narrow canyons at the bottom of the mountain ranges.

They are fan-shaped formations of sediment left by prior water movement when the canyons were streams or rivers that emptied into the desert. Playas are the dry lake beds left after standing water has evaporated. They have a very high salt content, and are sometimes referred to as salt plains. Hoodoos are oddly shaped columns whose shape is due to differential erosion. They create striking additions to a sometimes monotonous landscape. Sand dunes are large piles of loose sand that has been carried and shaped by the wind (Rundel, 1996) The Kelso dunes, located where the Mojave River meets Soda Lake, are some of the most spectacular.

These dunes are thought to be as much as 20,000 years old (Alonso, 1994). Although slight, the Mojave Desert does have some water movement in the form of the Mojave River, which flows from the San Bernardino Mountains. It is intermittent,but some water is able to flow into the desert. This activity within a desert is defined as allogenic drainage and refers to water systems that originate outside the desert and disappear within it (Rundel, 1996). When the Mojave receives moisture it is usually in the form of rainfall - between 2.23 and 6.5 inches - mostly during the winter months (Norris, 1976).

This accounts for up to 44% of rainfall in the Mojave annually (Orme, 2000). Infrequent summer storms are another source. These occur when influxes of warm air from the Gulf of Mexico or