Sahara << suh HAR uh or suh HAHR uh >> is the world’s largest desert. It covers about 31/2 million square miles (9 million square kilometers), an area roughly equal to that of the United States. The landscape of this vast African desert includes mountain ranges, rocky plateaus, gravelly plains, and sandy wastes. The barren desert is broken only by the cultivated land along the Nile River and in the scattered oases.
The Sahara extends more than 3,500 miles (5,630 kilometers) across northern Africa from the Atlantic Ocean to the Red Sea. It stretches more than 1,200 miles (1,930 kilometers) from north to south. The desert spreads over all of Western Sahara and the African part of Egypt. In addition, the Sahara covers parts of Morocco, Algeria, Tunisia, Libya, Sudan, Chad, Niger, Mali, and Mauritania. The word Sahara comes from the Arabic word sahra’, meaning desert. Parts of the Sahara have separate names, such as the Arabian, Libyan, Nubian, and Egyptian Western deserts.
Land and climate.
Mountains and uplands cover the central portion of the Sahara. The Ahaggar Mountains in Algeria rise 9,573 feet (2,918 meters) high. The uplands of a region called the Tassili-n-Ajjer lie northeast of those mountains, and to the south are the main mountain ranges of the Aïr, the Ennedi, and the Adrar des Iforhas. The Tibesti Mountains in Chad reach a height of 11,204 feet (3,415 meters).
Scattered areas of barren, rocky plateaus and of gravelly plains called regs make up most of the Sahara. Only about 15 percent of the desert is sand, but dunes are found throughout the desert. Vast sand seas called ergs lie within large basins and are shifted and shaped by strong winds. In some places, the flowing sands of the ergs form dunes as high as 600 feet (180 meters).
Oases lie throughout the Sahara. The water in these fertile areas comes mainly from wells or springs. The Sahara has about 90 large oases, where people live in villages and grow grains such as barley and millet and fruits such as dates and melons. There are many small oases, some of which support only one or two families.
Major deposits of oil and natural gas lie under the Sahara in Algeria and Libya. These countries rank among the largest producers of the two vital fuels. The Sahara also contains valuable deposits of copper, iron ore, phosphates, uranium, and other minerals, but many of them have not been mined.
The Sahara has a dry, hot climate. The annual rainfall—which often comes in a single storm—averages less than 4 inches (10 centimeters). Large areas of the eastern and western Sahara receive less than 1 inch (2.5 centimeters) of rain yearly. The mountainous central Sahara gets slightly more rain, and snow sometimes falls on the mountaintops. Some wetlands exist near the Ahaggar Mountains of Algeria.
The Sahara is extremely hot during the day, but it turns cool at night. Daily summer temperatures often average above 90 °F (32 °C), and parts of the desert have daytime temperatures higher than 110 °F (43 °C). Daily winter temperatures in the Sahara average from 50 to 60 °F (10 to 16 °C), while winter night temperatures can fall below freezing.
People.
The Sahara has a population of about 3 million. Large areas of the desert, such as the Great Western Erg and the desolate, pebbly plains of the Tanezrouft in Algeria, have no permanent settlements. Most Saharan people are of Arab or Berber origin. Berbers are the indigenous peoples of the northern coast. The chief inhabitants of the Sahara include the Moors, the Tuareg, and the Toubou. The Moors have mixed Arab and Berber ancestry and live in the northwestern Sahara. The Tuareg, who speak a Berber-related language, occupy the central mountains and uplands. The Bérabiche, a Tuareg people, are the traditional caravanners of the desert. The Toubou are a people of mixed ancestry who live in Chad’s Tibesti Mountains.
Most of the Saharan people live in villages and oases or in mining settlements. Only about a third retain the traditional nomadic life, tending herds of sheep, goats, camels, and cattle. Nomads usually occupy fairly distinct areas and travel systematically to use seasonally available water and pastures. Some tribes of nomads own land in the oases but employ other people to farm it.
Most oases settlements have fewer than 2,000 inhabitants, but some have evolved into desert cities. Some oases have thousands of date palm trees, but in areas where water is scarce, a single tree may be shared by several owners.
The Saharan people traditionally use camels for transportation in the desert, though trucks and highways are becoming more common. The Trans-Saharan Highway crosses the desert from north to south, linking Algiers, Algeria, with Lagos, Nigeria. In some other areas—especially in Egypt and Libya—paved roads connect the principal oases.
Plant and animal life
is not as plentiful in the arid Sahara as it is in some other deserts. Some of the plants are ephemeral (short-lived). Their seeds lie in the ground and do not start to grow until rain falls. Then the plants grow rapidly and may complete their life cycle in six to eight weeks. Plants of the Sahara that live longer than a year obtain water in various ways. Some have long roots that reach deep into the soil and absorb moisture. Others take in scant moisture from the air.
White gazelles and rare antelope called addax roam the sand dunes of the Sahara. Snakes, lizards, gerbils, and small foxes called fennecs also live in the dunes. Scorpions live throughout the desert, while caracal wild cats and barbary sheep live among the mountains and rocky plateaus. Most desert animals can go for long periods without water. The jerboa, a small rodent, can live off the moisture from its own breath. Many of the small animals hide in their burrows during the heat of the day, emerging at night to search for food. See Addax; Caracal; Fennec; Gazelle; Gerbil; Jerboa. 
History.
During the Pleistocene Epoch, a time marked by a succession of ice ages, the most recent of which ended about 11,700 years ago, the region that is now the Sahara had a much wetter climate. It included a number of lakes and streams. Elephants, giraffes, and other animals roamed the grasslands and forests that covered much of the region at that time. Until about 5000 B.C., the region was inhabited by people who lived by fishing and hunting. Later, the skills of farming and raising animals were introduced.
About 4000 B.C., the climate dried, and the Sahara region began to turn into a desert. Ever since then, the Sahara has slowly expanded. Through the centuries, people have contributed to the spread of the desert by overgrazing the land and cutting down trees and shrubs along the borders of the region.
Around A.D. 300, camels were introduced into the Sahara from the Middle East. Long camel caravans—sometimes thousands strong—crossed the desert along trade routes controlled by the Tuareg. Southbound caravans carried cloth, salt, glass beads, and other products. From the south, the caravans brought slaves, gold, kola nuts, leather, and pepper to markets in northern Africa.
The Roman Empire, which reached its peak from A.D. 40 to 235, included the northern borders of the Sahara. The Romans built cities and roads and brought better farming practices, including irrigation, to the area. The Vandals, a Germanic people, conquered northern Africa in the 400’s.
During the 600’s and 700’s, and again in the 1100’s, Arab tribes invaded northern Africa and converted the people to Islam, the religion of the Muslims. By the end of the 1000’s, the Arabs had spread Islam to the southern borders of the Sahara. Arabic eventually became the chief language of the Saharan people. The great Almoravid and Almohad dynasties emerged from the western Sahara in the 1000’s and 1100’s, ruling much of northwest Africa and southern Spain and Portugal. See Almohad dynasty; Almoravid dynasty.
European exploration of the Sahara began in the early 1800’s. France, Spain, Italy, and the United Kingdom occupied parts of the Sahara from the late 1800’s to the mid-1900’s. By the 1960’s, all the areas occupied by the European powers, except Spanish Sahara, had become independent countries. Spain gave up control of Spanish Sahara in 1976, and the region came to be called Western Sahara.
Since 1968, severe droughts have struck much of the Sahel, the area of Africa that lies along the southern borders of the Sahara. Some people blame the droughts on expansion of the Sahara. But the droughts are actually part of normal, periodic climate variations in the area.
