Definition of a Desert

The term ‚”desert” has been used to describe many different regions. However, there is no real definition of a desert. Generally, it can be an area of low precipitation and high evaporation. A region that receives less than 10 inches (250 mm) of annual precipitation is the most-used definition.

Nevertheless, low precipitation is not the only criterion. Areas with precipitation rates higher than 15 inches are defined as deserts if there are high rates of evaporation, usually due to exceptionally low humidity.

Additionally, despite Hollywood renditions, deserts do not have to be hot places. Antarctica is considered a desert, even though it is the coldest place on the planet.

Some deserts can be higher than 4,000 feet above sea level. In fact, areas in the northern parts of New Mexico and Arizona and parts of Colorado and other western states may be over a mile high and yet still be classified as desert regions.

There are four basic desert regions in North America: the Chihuahuan, Sonoran, Great Basin and Mojave. Subtle variations in temperature, humidity and vegetation define the regions.

Sonoran Desert

This desert is subtropical and covers most of the Baja Peninsula and extreme northwestern Mexico (essentially both sides of the Gulf of California), southwestern Arizona and southeastern California. Summer monsoons add moisture to the desert, as do winter rains coming down from the Great Basin Desert several hundred miles to the north.

These rains make it one of the most, if not the most, biologically diverse desert on the planet.

Contrary to popular opinion, the Saguaro cactus, which resembles a man holding his hands in the air, can only be found in the Sonoran Desert and nowhere else.

The greater part of this desert is low in elevation, making it very hot in its southernmost regions.

There are several mountain ranges, which break up the Sonoran.

Chihuahuan Desert

The Chihuahuan Desert is the largest desert in North America, and includes most of northern Mexico, southern and central New Mexico, southeastern Arizona and west Texas.

Most of the Chihuahuan is considered ‚”high desert,” with average elevations between 3,000 and 6,000 feet, although there are some higher areas and some much lower. Annual precipitation is between eight and 12 inches. Most of the precipitation comes during summer monsoons.

Agaves (Century plants) are the most well known plants native to the Chihuahuan Desert.

Mojave Desert

Lodged between the Sonoran and Great Basin Deserts, the Mojave Desert is the smallest of North American Deserts, and some consider it simply a transition between these two larger deserts.

It covers an area of southeastern California, northwestern Arizona and southern Nevada.

The Joshua Tree is the most well known plant in the Mojave. Like the other North America deserts, it receives precipitation from summer monsoons, and from rains coming down from the Pacific Northwest.

The driest of all deserts on the continent, it receives less than six inches of rain, and some areas receive four or less. Dry air also helps increase temperatures.

Death Valley, one of the lowest land areas on the planet, lies within the Mojave.

Great Basin

The Great Basin Desert covers most of Nevada, although it ranges into Utah, Oregon, Idaho and California.

It is the most northern of North American deserts, and is a cold, high desert (with average elevations over 4,000 feet.)

Snow, which is the major part of precipitation in the Great Basin, generally comes in late winter and early spring, brought by great storms moving in from the Pacific Northwest.

Sagebrush, pinion and juniper are the dominate forms of vegetation.

Related articles include:

1. High and Low Deserts
2. What is a Desert?
3. Field Guide to Sagebrush