Deserts cover roughly a third of Earth’s land surface and exist on every continent. Most cluster in two bands near 30° north and south of the equator, but they also form deep in continental interiors, along cold-current coastlines, and at the poles. Understanding the patterns behind their placement makes the full global picture easier to remember than memorizing a list.
Why Deserts Form Where They Do
The single biggest driver of desert placement is atmospheric circulation. Warm, moist air rises near the equator, drops its moisture as tropical rain, then flows outward at high altitude. By the time that air sinks back toward the surface around 30° latitude, it’s dry and compresses as it descends, creating persistent high-pressure zones that suppress rainfall. This loop, called a Hadley cell, explains why so many of the world’s great deserts sit in a belt straddling the tropics.
Other deserts owe their existence to different forces. Mountain ranges block moisture-laden winds, wringing out rain on one side and leaving the other side parched. The Gobi Desert sits in the rain shadow of the Himalayas. The Patagonian steppe is dried out by the Andes. In North America, the Sierra Nevada and Cascade ranges intercept Pacific moisture, starving the Great Basin of Nevada and Utah. Cold ocean currents also play a role: they chill coastal air, stabilizing it so it rarely produces rain, which is why some of the driest places on Earth sit right next to the ocean.
North Africa and the Middle East
The Sahara is the world’s largest hot desert, stretching across most of northern Africa from the Atlantic Ocean in the west to the Red Sea in the east. The Atlas Mountains and Mediterranean Sea form its northern boundary, while the Sahel, a transitional band of semi-arid savanna, marks its southern edge. The Sahara touches at least ten countries, including Morocco, Algeria, Libya, Egypt, Mali, Niger, and Chad. Its landscape varies enormously: sand seas, rocky plateaus like the Ennedi in Chad, volcanic massifs like the Aïr in Niger, and vast gravel plains.
East of the Sahara, aridity continues through the Arabian Peninsula, where the Arabian Desert covers Saudi Arabia, Oman, Yemen, and neighboring states. Within it sits the Rub’ al Khali, or Empty Quarter, one of the largest continuous sand bodies on Earth.
Asia’s Interior Deserts
The Gobi Desert stretches across huge portions of both Mongolia and China, hemmed in by the Altai and Hangayn mountains to the north, the Yin and Qilian mountains to the south, and the Tien Shan to the west. Unlike the Sahara, the Gobi is largely a cold desert. Winter temperatures plunge well below freezing, and much of its surface is bare rock and hard-packed earth rather than sand dunes. The Gobi includes several distinct sub-regions: the Trans-Altai Gobi in the west, the Eastern (Mongolian) Gobi in the center, and the Alxa Plateau in the south, which sits between the Huang He river and the China-Mongolia border.
Farther west, Central Asia holds the Karakum and Kyzylkum deserts across Turkmenistan and Uzbekistan, while the Thar Desert spans the border region between northwestern India and southeastern Pakistan. Each of these deserts formed partly because of sheer distance from any ocean and partly because surrounding mountain systems block incoming moisture.
South America’s Coastal and Rain Shadow Deserts
Chile’s Atacama Desert runs along the Pacific coast, squeezed between the ocean and the Andes. It is the driest place on Earth outside Antarctica’s interior valleys, receiving measurable rainfall only a handful of times per century in its most arid core. The extreme dryness comes from a double mechanism: cold Antarctic-origin ocean currents stabilize coastal air and prevent rain clouds from forming, while the Andes block any moisture approaching from the east. The only regular water source in parts of the Atacama is a dense coastal fog called camanchaca, created when cold marine air meets warmer air above it.
On the opposite side of the Andes, Patagonia is rain-shadowed from prevailing westerly winds. The landscape is arid steppe with poor pasture, sparse water, and scattered salt lakes. Farther north, the Guajira Peninsula in Colombia sits in the rain shadow of the Sierra Nevada de Santa Marta and is nearly arid despite being in the tropics, going seven to eight months each year with almost no rainfall.
North American Deserts
North America has four major desert systems, all in the western half of the continent. The Great Basin Desert covers nearly all of Nevada and parts of Utah, Oregon, and Idaho. It is a cold desert at relatively high elevation, dried out by the Sierra Nevada and Cascade ranges to its west. In California, near the Great Basin’s southern edge, Death Valley holds the record for the highest reliably recorded air temperature on Earth.
The Mojave Desert sits in southeastern California and stretches into southern Nevada and small portions of Utah and Arizona. To its southeast, it merges into the Sonoran Desert, which covers much of southern Arizona, extends into Baja California, and runs along the Gulf of California coast into the Mexican state of Sonora. The Sonoran is famous for its giant saguaro and barrel cacti. East of there, the Chihuahuan Desert extends from southern New Mexico and western Texas deep into the highlands of central Mexico, making it one of the largest deserts in North America.
Australia’s Desert Interior
Australia is the driest inhabited continent, and desert or semi-arid land dominates its interior. The Great Victoria Desert, the country’s largest, features red sand dunes, stony plains, and dry salt lakes, stretching across parts of Western Australia and South Australia. Surrounding it are the Great Sandy Desert to the north, the Gibson Desert, the Tanami, and the Simpson Desert farther east. Together these deserts form a nearly continuous arid zone across the continent’s center and west, leaving only the coastal fringes with reliable rainfall.
Africa Beyond the Sahara
Southern Africa has its own desert belt. The Namib Desert lines the Atlantic coast of Namibia, created by the cold Benguela Current in much the same way the Atacama forms along South America’s Pacific coast. Inland, the Kalahari spans Botswana, parts of Namibia, and South Africa. The Kalahari receives more rain than a true desert in some definitions, but its sandy soils drain so quickly that the surface stays arid, and much of it functions ecologically as desert.
The Polar Deserts
The two largest deserts on Earth are not hot at all. Antarctica, covering 14.2 million square kilometers (5.5 million square miles), qualifies as a desert because its interior receives less precipitation than the Sahara. It is also the coldest desert on the planet. The Arctic, Earth’s other polar desert, spans northern Greenland, Canada’s Arctic Archipelago, and parts of Svalbard and Siberia. Both polar deserts are defined by extremely low precipitation, most of which falls as snow, and by air so cold it holds almost no moisture.
Deserts Are Expanding
Desert boundaries are not fixed. A landmark UN report found that 77.6% of Earth’s land experienced drier conditions in the three decades leading up to 2020 compared to the previous 30-year period. Drylands expanded by about 4.3 million square kilometers during that time, an area nearly a third larger than India, and now cover 40.6% of all land on Earth (excluding Antarctica). Roughly 7.6% of global land, an area larger than Canada, crossed aridity thresholds, shifting from non-dryland to dryland or from less arid to more arid categories.
The regions hit hardest by this drying trend include almost all of Europe (95.9% of its land), parts of the western United States, Brazil, eastern Asia, and central Africa. South Sudan and Tanzania saw the largest percentage of their land transition to drylands, while China experienced the largest total area making that shift. If greenhouse gas emissions continue unchecked, projections show another 3% of the world’s humid areas becoming drylands by century’s end, with expansion forecast across the U.S. Midwest, central Mexico, the entire Mediterranean, large parts of southern Africa, and southern Australia.