Mojave Desert
The Mojave Desert is the smallest of the four major North American deserts but the hottest. It covers parts of California, Nevada, Utah and Arizona in the southwestern United States. The Mojave is famous for its iconic Joshua trees, for containing Death Valley (the hottest place on Earth), and for the bright lights of Las Vegas, which grew up at the desert's eastern edge.
- Areaapprox. 124,000 km²Around half the size of the UK
- CountryUnited StatesMostly in California, also Nevada, Utah, Arizona
- Hottest temperature56.7 °CDeath Valley, 1913 (world record)
- Elevation range-86 m to 3,633 mFrom below sea level to high mountains
- Iconic plantJoshua treeA giant member of the yucca family
- Big cityLas VegasOn the eastern edge of the desert
Mojave compared to other American deserts
The Mojave is the smallest of the four major North American deserts, but it is famous as the hottest and as the home of Death Valley.
What is the Mojave?
The Mojave Desert sits in the rain shadow of California's Sierra Nevada and Transverse Ranges. Moist air from the Pacific rises and drops its rain on the western side of these mountains, leaving the Mojave dry on the eastern side. The desert is a high-elevation desert (mostly above 600 metres) with bare mountain ridges separated by dry valleys. Several of those valleys, including Death Valley, have no outlet and fill with shallow temporary lakes after rare storms before drying out again.
The Joshua tree
The Joshua tree is the most famous plant of the Mojave. It is not really a tree at all but a giant member of the yucca family. Joshua trees can grow to 15 metres tall and live for 150 years. They are restricted almost entirely to the Mojave and a few neighbouring areas. The name comes from Mormon settlers in the 1800s who thought the spreading branches reminded them of the biblical prophet Joshua holding his arms up in prayer.
The famous Joshua Tree National Park, on the southern edge of the Mojave, was set aside to protect them. Climate change is now threatening Joshua trees in much of their range; warmer temperatures are killing young trees before they can establish.
Death Valley
Death Valley is the lowest, hottest and driest part of the Mojave. The valley floor at Badwater Basin lies 86 metres below sea level, the lowest point in North America. Summer afternoons regularly exceed 49 °C. The valley got its name in 1849 when a group of pioneers crossed it on their way to the California gold rush and almost all of them died. The survivors looked back from the western edge and said "goodbye, Death Valley". The name stuck.
Las Vegas and human use
The bright lights of Las Vegas stand at the eastern edge of the Mojave Desert. The city grew up around a small spring (the original "Las Vegas" or "meadows" the Spanish named it for) and exploded after the building of the Hoover Dam on the Colorado River in the 1930s gave it cheap water and power. Today Las Vegas is one of the fastest-growing cities in the United States. The Mojave is also home to several major military bases (its empty landscape is useful for testing weapons and flying jets) and large solar power farms.
Deeper dive: rain shadows, the Colorado River and the future of desert cities
The Mojave is a classic rain shadow desert. The Sierra Nevada and Transverse Ranges to the west force moist air from the Pacific to rise, cool, and drop its moisture as rain or snow on the western side. By the time the air descends on the eastern side, it has lost most of its water and warms up as it sinks, becoming hot dry desert air. The same process creates other deserts including the Gobi (in the rain shadow of the Himalayas) and the Atacama (rain shadow of the Andes). The Mojave is unusual because of the combination of high elevation, low latitude and extreme topography that produces such intense summer heat.
The Colorado River is the lifeline of the Mojave region. It rises in the Rocky Mountains, flows through the Grand Canyon, and then crosses the southern Mojave on its way to the Sea of Cortez (Gulf of California) in Mexico. The Hoover Dam on the Colorado, built in the 1930s, created Lake Mead and provides water and electricity for over 25 million people across the southwestern US and northern Mexico. The river is over-allocated: more water is promised to users (farms, cities, factories) than the river actually carries in a normal year. With prolonged droughts driven by climate change, Lake Mead's water level has dropped dramatically in recent decades, threatening the entire water supply of the desert southwest.
Las Vegas is the canary in the climate-change coal mine for the American Southwest. The city has roughly tripled in population since 1990, putting enormous pressure on its limited water supply. Las Vegas has responded with some of the most aggressive water-conservation programmes in the world: paying homeowners to remove grass lawns, banning ornamental water features at hotels, and recycling almost all indoor wastewater for outdoor use. Despite tripling its population, the city now uses less water than it did in 2002. Whether these measures are enough to sustain the city as the climate continues to warm is one of the great open questions of southwestern North American planning.
The country is the United States. For the hottest spot in the desert, see Death Valley.