I grew up camping in the Mojave Desert, in undeveloped BLM areas popular with off-roaders, rock-hounds, prospectors, and others who wanted wide open spaces. So naturally I want to tell people about the stomping grounds of my youth.

The Mojave Desert, tucked between the Great Basin to the north and the Sonoran Desert to the south, occupies nearly 48,000 square miles mostly in southeastern California, spilling over into Nevada, Arizona, and even Utah. Within its boundaries lie Death Valley National Park, Joshua Tree National Park, Lake Mead National Recreation Area, and Mojave National Preserve. The ecology of each of these areas is different enough that they deserve their own description. Today I’ll focus on the Mojave National Preserve, which is sort of centered between the others.

What is a Desert?

A desert typically receives less than 10 inches of precipitation per year. And that evaporation and transpiration (water loss by plants) exceeds precipitation. Not all deserts are hot and dry; there are cold deserts in Alaska and the Himalayas, and polar deserts in the Arctic and Antarctic. Mojave’s average of five inches of precipitation comes as rain and even snow. Most of the precipitation in the western portion comes from winter storms. The central portion of the desert has warmer temperatures and more wind than the western and eastern parts.  

Basin and Range

The Mojave Desert has basin and range topography, with long mountain ranges separated by a broad V-shaped valley pointing west. The mountain ranges are formed by the San Andreas fault zone to the southwest, and the Garlock fault zone to the north. 

Temperature extremes cause erosion of the mountains, forming alluvium. Great fans of alluvium tumble or are carried by water down the mountainside and from canyons, and collect in the basins as layer upon layer slowly cause the floor of the basin to creep higher up the mountains. 

Since basins have no outlets, when rainfall collects and evaporates, it leaves behind deposits of salts and minerals. Not much will grow on these deposits, but they are good for mining of salt, borax, and sometimes silver and gold! These large flat, dried out lake beds are known as playas. 

In the northeast portion of the Mojave Natural Preserve is the Zzyzx Desert Studies Center, managed by the California State University system.  This slice of my own personal heaven is on the edge of Soda Dry Lake and deserves its own post, and that will come soon. Stay tuned!

Sand Dunes

When the erosion of the mountains continues enough, sand is formed. The sand may have, upon formation, come to rest a the bottom of lakes, which then dry up over thousands of years. Where there is a lot of sand and steady winds, sand dunes pile up against a mountainside. Most of the Sand Dunes in the Mojave Desert are in or near Death Valley. Kelso Dunes are fun to play on, because they “sing” or “boom” with a rumble as the sand is disturbed, as by people sliding slowly down the dune. This is a popular activity in the Mojave National Preserve!

Volcanos

The Mojave National Preserve contains several examples of volcanic activity, with Lavic Lake and Coso volcanic fields and Pisgah Crater, Amboy Crater National Natural Landmark (say that once, let alone 10 times fast!), and Cima Dome among the cone-shaped mountains of volcanic ash and fragments. These cinder cone volcanos exploded hot and fast, between 80,000 and 6,000 years ago. Craters in the center of the cones are where the plug of lava exploded out. The black lava rock is called basalt. 

Within the volcanic fields are lava tubes where lava continued to flow under the faster-cooling surface. 

Evidence of older volcanic activity, with eruptions starting around 18.5 million years ago and continuing for several million years, are seen at Hole in the Wall. The rock from these volcanos is lighter in color than the black basalt, and called rhyolite. It is made up of similar minerals as granite. Surface weathering has formed a “swiss-cheese” look to the rock. 

There is Water in the Desert

Afton Canyon Natural Area is one of few places where the Mojave River flows above ground and is ideal for bird and wildlife viewing. Outside the Mojave National Preserve, this Natural Area is managed by Bureau of Land Management. 

Mitchell Caverns at Providence Mountains State Recreation Area: limestone cave formations, tiny bats, and pseudoscorpions (harmless tiny arachnids that look like scorpions but without that nasty stinger). Note to self: Write a post about limestone cavern formation!

Vegetation Adaptation

A lot of people think the desert is nothing but barren and lifeless wasteland of sand. But in Mojave Desert there are many plants and animals that have adapted to the harsh environment. In fact, some really specialized trees and shrubs can be found in the desert, along with a beautiful variety of flowers.

Flowers and other annual desert plants (the ones that just live for one year, or season) have seeds that germinate after heavy seasonal rains, and quickly flower and produce thousands of seeds in the spring before the heat comes back. If there isn’t enough water, the seeds can remain in the soil until the following year. Since each year is different, different varieties of plants may be seen year to year. 

The cactus plants are extremely drought-resistant. They can store water in their stems. Some are “accordian-shaped” so they can expand when there is plenty of water to store. The spines provide shade, and the waxy skin prevents moisture loss. Their green stem provides the chlorophyll for photosynthesis. Those spines also help pieces of the cactus move around by sticking to passing animals, and falling off to take root in a new location. Watch out, or you could be that animal - and those spines can hurt!

Joshua Trees aren’t found anywhere on earth except the Mojave Desert. Along with other yucca, Joshua Trees cannot reproduce without the pollination of the yucca moth, which has evolved to distribute yucca pollen. The female moth lays eggs in the flower, and larvae feed on yucca seeds. 

Bushy plants like creosote, mesquite, and ocotillo have very small, waxy leaves and stems. Their roots reach deep to dry underground water. They typically go dormant in the dry season to conserve energy until water is available.

Animals Adapt, Too

Reptiles, snakes, and the little kangaroo rat are specially adapted for the hot, dry environment. Long legs on beetles and lizards keep their bodies farther from the ground. Pale coloring reflects sunlight. Many animals are nocturnal and spend the hot days hiding in burrows. Desert tortoises are among the many birds and reptiles that retain water so well that their waste is nearly solid. A desert tortoise can store a quart of water in its bladder. A jackrabbit uses those giant ears of his to cool off. The circulation of blood through the large surface area cools the blood when the rabbit is in a location cooler than his body temperature, such as in a burrow. Birds of prey such as the red-tailed hawk hunt those small animals. 

Some people are surprised to learn of larger animals such as mule deer, pronghorn antelope, bighorn sheep, and mountain lions also known as cougars) are also desert-dwellers. Introduced in the 1500 from Spain, wild burros also roam the desert landscape.