Mojave Desert
The Mojave Desert is a desert in the rain shadow of the southern Sierra Nevada mountains and Transverse Ranges in the Southwestern United States. Named after the indigenous Mohave people, it is located primarily in southeastern California and southwestern Nevada, with small portions extending into Arizona and Utah.
The Mojave Desert, together with the Sonoran, Chihuahuan, and Great Basin deserts, form a larger North American desert. Of these, the Mojave is the smallest and driest. It displays typical basin and range topography, generally having a pattern of a series of parallel mountain ranges and valleys. It is also the site of Death Valley, which is the lowest elevation in North America. The Mojave Desert is often colloquially called the "high desert", as most of it lies between. It supports a diversity of flora and fauna.
The desert supports a number of human activities, including recreation, ranching, and military training. The Mojave Desert also contains various silver, tungsten, iron and gold deposits.
The spelling Mojave originates from the Spanish language, while the spelling Mohave comes from modern English. Both are used today, although the Mojave Tribal Nation officially uses the spelling Mojave, which is a shortened form of Hamakhaave, an endonym in their native language, meaning "beside the water".
Geography
The Mojave Desert is a desert bordered to the west by the Sierra Nevada mountain range and the California montane chaparral and woodlands, and to the south and east by the Sonoran Desert. The boundaries to the east of the Mojave Desert are less distinctive than the other boundaries because there is no presence of an indicator species, such as the Joshua tree, which is endemic to the Mojave Desert. The Mojave Desert is distinguished from the Sonoran Desert and other deserts adjacent to it by its warm temperate climate, as well as flora and fauna such as ironwood, blue Palo Verde, chuparosa, spiny menodora, desert senna, California dalea, California fan palm and goldenhead. Along with these other factors, these plants differentiate the Mojave from the nearby Sonoran Desert.The Mojave Desert is bordered by the San Andreas Fault to the southwest and the Garlock fault to the north. The mountains elevated along the length of the San Andreas fault provide a clear border between the Mojave Desert and the coastal regions to the west. The Garlock Fault separates the Mojave Desert from the Sierra Nevada and Tehachapi mountains, which provide a natural border to the Mojave Desert. There are also abundant alluvial fans, called bajadas, that form around the mountains within the Mojave Desert and extend down toward the low-altitude basins. These basins contain dried lake beds called playas, where water generally collects and evaporates, leaving large volumes of salt. These playas include Rogers Dry Lake and China Lake. Dry lakes are a noted feature of the Mojave landscape. The Mojave Desert is also home to the Devils Playground, about of dunes and salt flats going in a northwest-southeasterly direction. The Devil's Playground is a part of the Mojave National Preserve and is between the town of Baker, California and the Providence Mountains. The Cronese Mountains are within the Devil's Playground.
There are very few surface rivers in the Mojave Desert, but two major rivers generally flow underground. One is the intermittent Mojave River, which begins in the San Bernardino mountains and disappears underground in the Mojave Desert. The other is the Amargosa River, which flows partly underground through the Mojave Desert along a southward path. The Manix, Mojave, and the Little Mojave lakes are large but shallow. Soda Lake is the principal saline basin of the Mojave Desert. Natural springs are typically rare throughout the Mojave Desert, but there are two notable springs, Ash Meadows and Oasis Valley. Ash Meadows is formed from several other springs, which draw from deep underground. Oasis Valley draws from the nearby Amargosa River.
Climate
Extremes in temperatures throughout the seasons characterize the climate of the Mojave Desert. Freezing temperatures and strong winds are not uncommon in the winter, as well as precipitation such as rain and snow in the mountains. In contrast, temperatures above are not uncommon during the summer months. It receives annual average precipitation of, although regions at high altitudes such as the portion of the Mojave Desert in the San Gabriel mountains may receive more rain. Most precipitation in the Mojave comes from Pacific cyclonic storms as they migrate eastwards from November to April. Such storms generally bring rain and snow only in the mountainous regions, increasing aridity on the leeward slopes.During the late summer months, there is also the possibility of strong thunderstorms, which bring heavy showers or cloudbursts. These storms can result in flash flooding.
The Mojave Desert has not historically supported a fire regime because of low fuel loads and connectivity. However, in the last few decades, invasive annual plants such as some within the genera Bromus, Schismus and Brassica have facilitated fires by serving as a fuel bed. This has significantly altered many areas of the desert. At higher elevations, fire regimes are regular but infrequent.
Cities and regions
While the Mojave Desert is generally sparsely populated, it has increasingly become urbanized in recent years. The metropolitan areas include Las Vegas, the largest urban area in the Mojave and the largest urban area in Nevada with a population of about 2.3 million. St. George, Utah, is the northeasternmost metropolitan area in the Mojave, with a population of around 180,000 in 2020, and is located at the convergence of the Mojave, Great Basin, and Colorado Plateau. The Los Angeles exurban area of Lancaster-Palmdale has more than 400,000 residents, and the Victorville area to its east has around 550,000 residents. Smaller cities or micropolitan areas in the Mojave Desert include Helendale, Lake Havasu City, Kingman, Laughlin, Bullhead City, Pahrump, and Twentynine Palms. All have experienced rapid population growth since 1990. The California portion of the desert also contains Edwards Air Force Base and Naval Air Weapons Station China Lake, noted for experimental aviation and weapons projects.The Mojave Desert has several ghost towns. The most significant are the silver and copper-mining town of Calico, California, and the old railroad depot of Kelso, California. Some of the other ghost towns are more modern, created when U.S. Route 66 was abandoned in favor of the construction of Interstates. CA SR 14, Interstate 15, Interstate 40, CA SR 58, CA SR 138, US Route 95, and US Route 395 are the main highways that traverse the Mojave Desert.
Geology
The exposed geology of the Death Valley presents a diverse and complex set of at least 23 formations of sedimentary units, two major gaps in the geologic record called unconformities, and at least one distinct set of related formations geologists call a group. The oldest rocks in the area that now includes Death Valley National Park are extensively metamorphosed by intense heat and pressure and are at least 1700 million years old. These rocks were intruded by a mass of granite 1400 Ma and later uplifted and exposed to nearly 500 million years of erosion.The rock that forms the Mojave Desert was created under shallow water in the Precambrian, forming thick sequences of conglomerate, mudstone, and carbonate rock topped by stromatolites, and possibly glacial deposits from the hypothesized Snowball Earth event. Rifting thinned huge roughly linear parts of the supercontinent Rodinia enough to allow sea water to invade and divide its landmass into component continents separated by narrow straits. A passive margin developed on the edges of these new seas in the Death Valley region. Carbonate banks formed on this part of the two margins only to be subsided as the continental crust thinned until it broke, giving birth to a new ocean basin. An accretion wedge of clastic sediment then started to accumulate at the base of the submerged precipice, entombing the region's first known fossils of complex life.
During the Paleozoic era, the area that is now the Mojave was again likely submerged under a greater sea. The passive margin switched to active margin in the early-to-mid Mesozoic when the Farallon Plate under the Pacific Ocean started to dive below the North American Plate, initiating a subduction zone; volcanoes and uplifting mountains were produced as a result. Erosion over many millions of years formed a relatively featureless plain.
Stretching of the crust under western North America started around 16 Ma and is thought to be caused by upwelling from the subducted spreading-zone of the Farallon Plate. This process continues into the present and is thought to be responsible for producing the Basin and Range province. By 2 to 3 million years ago this province had spread to the Death Valley area, ripping it apart and giving birth to Death Valley, Panamint Valley and surrounding ranges. These valleys partially filled with sediment and, during colder periods during the current ice age, with lakes. Lake Manly was the largest of these lakes; it filled Death Valley during each glacial period from 240,000 years ago to 10,000 years ago. By 10,500 years ago these lakes were increasingly cut off from glacial melt from the Sierra Nevada, starving them of water and concentrating salts and minerals. The desert environment seen today developed after these lakes dried up.
The Mojave Desert is a source of various minerals and metallic materials. Due to the climate, there is an accumulation of weathered bedrock and fine sand and silt, forming colluvium. Deposits of gold, tungsten, and silver were heavily exploited prior to the Second World War. Deposits of copper, tin, lead-zinc, manganese, iron, and various radioactive substances are known to exist but have not been commercially mined.