Sahara

The Sahara is a very big desert in Africa.

It is hot and dry. In some places there are hills of sand called dunes. In other places there are rocks, gravel and tall mountains.

The Sahara stretches across almost all of northern Africa, from the Atlantic Ocean in the west to the Red Sea in the east. To the north are the Atlas Mountains and the Mediterranean Sea, and to the south is the Sahel, a strip of semiarid land between the desert and the savannas. The name Sahara comes from the Arabic word for desert.

Britannica calls it the largest hot desert in the world. It is about 4,800 kilometers wide and covers about 8.6 million square kilometers, although its size changes as the desert grows and shrinks over time. Its highest point is Mount Koussi in Chad, 3,415 meters high, and its lowest is Egypt's Qattara Depression, 133 meters below sea level.

Britannica describes the Sahara as the largest hot desert in the world, about 4,800 km (3,000 miles) from east to west and 800 to 1,200 miles from north to south, with an area of some 8,600,000 km² that varies as the desert expands and contracts. It is bordered by the Atlantic, the Atlas Mountains and Mediterranean, the Red Sea and the semiarid Sahel. The name derives from Arabic ṣaḥrāʾ, desert; in Arabic it is Al-Ṣaḥrāʾ al-Kubrā, the Great Desert. Britannica names parts of Morocco, Algeria, Tunisia, Libya, Egypt, Mauritania, Mali, Niger, Chad and Sudan, and describes the territory of Western Sahara, whose political status it calls unresolved, as part of the Sahara.

Its landscapes include seasonally flooded basins (chotts and dayas), large oasis depressions, gravel-covered plains (serirs or regs), rock-strewn plateaus (hammadas), abrupt mountains, and sand sheets, dunes and sand seas (ergs). The highest point is the 3,415 m summit of Mount Koussi in Chad's Tibesti Mountains, and the lowest, 133 m below sea level, lies in Egypt's Qattara Depression.

Some plants and animals live in the Sahara.

The fennec fox has giant ears. Camels can walk far across the sand. After rain, little plants grow and flower very fast.

Life is sparse in the Sahara, but it is there. Grasses, shrubs and trees grow in the mountains, in oases and along wadis, dry riverbeds that sometimes flow after rain. Some small plants can sprout within three days of a good rain and make seeds within 10 to 15 days, living almost their whole life in the two or three weeks after a heavy rain.

The fennec fox lives throughout the Sahara. It is the smallest member of the dog family, with the biggest ears for its size, which help it lose heat and hear prey under the sand. Its furry paws grip the sand and protect it from the heat. People have long herded camels, goats and sheep across the desert, and in oases they grow date palms and barley.

Britannica describes Saharan vegetation as generally sparse, concentrated in the highlands, oasis depressions and wadis, with salt-tolerant halophytes in saline basins. Many herbaceous plants are ephemerals that may germinate within three days of adequate rainfall and set seed within 10 to 15 days; relict olive, cypress and mastic trees survive in the massifs, alongside acacias, doum and date palms, oleander and grasses such as Aristida and Panicum. Animals such as the desert snail survive by estivation, a dormancy during extreme stress.

The Smithsonian's National Zoo notes that fennec foxes live throughout the Sahara and east to Sinai and Arabia; they have the largest ears relative to body size of any canid, used to shed heat and locate prey under the sand, heavily furred paws, and can go long periods without drinking. People have lived in the Sahara since before recorded history, as nomadic pastoralists herding goats, sheep or camels, oasis farmers growing date palms and barley, and traders on caravan routes.

The desert can be very hot, and storms can bring sudden floods.

In one big desert park, visitors always go with a guide. Old rock paintings there are looked after with care. Look at them, but do not touch!

The Sahara can be dangerous for people who are not prepared: very hot days, sudden floods after storms, and winds full of dust. For centuries, people crossed it on caravan routes from oasis to oasis.

In Tassili n'Ajjer, a cultural park and World Heritage Site in Algeria, tourism is strictly controlled, and groups of visitors are always accompanied by an official guide. UNESCO warns that the ancient rock art there can be damaged by the weather and by visitors. So look at the paintings, but never touch them.

The Sahara's hazards are real but well understood: highs near 50 °C in the south, flash floods from summer storms, and dust-laden winds such as the harmattan, khamsin and haboob (Britannica).

At Tassili n'Ajjer, a 72,000 km² plateau in southeastern Algeria inscribed in 1982, UNESCO describes the rock art as vulnerable both to climatic deterioration and to damage caused by visitors. Tourism, which brings income and jobs to local people, is strictly controlled, and groups of visitors are always accompanied by an official guide. On the desert's southern edge, the Great Green Wall initiative, conceived in 2005 and developed with the African Union, plans a 15 km wide belt of drought-resistant native trees across the continent to slow desertification.