Sahara Desert

The Sahara is the biggest hot desert on Earth. It covers most of northern Africa and is roughly the size of the United States or China. The Sahara is famous for its endless sand seas and towering dunes, but most of the desert is actually rocky plain or gravel, not sand. About 4 million people still live in the Sahara today, mostly in scattered oases and the few rivers that cross it.

  • Area9.2 million km²About the size of the USA
  • Countries10Across northern Africa
  • Hottest temperatureapprox. 58 °CIn the shade, in summer
  • Coldest temperature-6 °CPossible on winter nights
  • Average rainfallUnder 25 mm/yearSome areas go years with none at all
  • Biggest duneAround 300 m tallSome sand seas have dunes the size of buildings

How big is the Sahara compared to other deserts?

Area (million km²)
Antarc.14.0
Arctic13.9
Sahara9.2
Gobi1.3
Kalahari0.9

The Sahara is the biggest hot desert on Earth. It is bigger than the Gobi, Kalahari and Arabian deserts combined. Only the Antarctic and Arctic (which are cold deserts) are bigger.

What is the Sahara?

The Sahara stretches across northern Africa from the Atlantic Ocean in the west to the Red Sea in the east, and from the Mediterranean coast in the north to the dry grasslands of the Sahel in the south. The word "Sahara" actually comes from the Arabic word for "desert", so "Sahara Desert" technically means "desert desert".

The Sahara covers all or part of ten countries: Algeria, Chad, Egypt, Libya, Mali, Mauritania, Morocco, Niger, Sudan, Tunisia and the disputed territory of Western Sahara.

Sand seas, rocky plains and mountains

People often picture the Sahara as endless sand dunes, but only approx. 25% of the desert is actually sandy. The sandy areas, called ergs or sand seas, can stretch for hundreds of kilometres with dunes up to 300 metres tall. Most of the rest of the Sahara is rocky plain (called reg or hamada) or smaller mountain ranges. There are several substantial mountain groups inside the Sahara, including the Ahaggar Mountains in southern Algeria and the Tibesti Mountains in northern Chad, which reach over 3,400 metres.

Fact The Sahara was not always a desert. As recently as 6,000 years ago, much of the Sahara was a green savanna with lakes, rivers, hippos and crocodiles. Cave paintings deep in the desert show ancient people hunting big game in landscapes that look nothing like today. The desert returned as the Earth's climate slowly shifted.

People of the Sahara

About 4 million people live in the Sahara, mostly in scattered oases (places with springs or wells) and along the few rivers that cross the desert. The largest river is the Nile in the east. Famous Saharan peoples include the Tuareg (camel-riding traders sometimes called the "blue people" because of the deep blue veils the men wear), the Berbers, the Bedouin Arabs and the Toubou. For over 1,000 years, traders crossed the Sahara on camel caravans carrying salt from the desert and gold from West Africa.

Wildlife of the Sahara

Despite the harsh conditions, the Sahara is home to many specialised animals. Fennec foxes are tiny desert foxes with huge ears that help shed heat. Sand cats are small wild cats whose paws are covered in fur to insulate them from hot sand. Dromedary camels (called "ships of the desert") can drink 100 litres of water in 10 minutes and store the energy as fat in their humps. There are also gazelles, addax (a kind of antelope), monitor lizards, scorpions, and the deadly horned viper.

Did you know? Sand from the Sahara regularly gets blown all the way across the Atlantic Ocean. Saharan dust falls on the Amazon rainforest of South America, where it actually fertilises the soil. Without occasional Saharan dust deliveries, the Amazon would be less productive.
Deeper dive: the Green Sahara, desertification and the Sahel

The Sahara has cycled between green and dry several times over the past 8 million years, driven mainly by slow changes in the Earth's orbit and tilt. The most recent green period, the so-called African Humid Period or "Green Sahara", lasted from around 11,000 to 5,000 years ago. During that time, monsoon rains penetrated deep into what is now desert, supporting lakes (Lake Mega-Chad in central Africa was one of the biggest lakes on Earth), rivers, and abundant grassland. Rock art deep in the desert at Tassili n'Ajjer in Algeria shows people herding cattle, hunting elephant and even swimming, in landscapes that have been dry for thousands of years.

The Sahara is currently growing in some places. Desertification (the process where productive land turns to desert) is happening along the southern edge of the Sahara, where the desert grades into a region called the Sahel. The Sahel is a band of dry grassland stretching across Africa from Senegal to Sudan. Climate change, overgrazing, deforestation and unsustainable farming are all pushing the desert edge southward. Whole villages have been buried by advancing dunes. The Sahel has been struck by repeated devastating famines linked to drought.

The most ambitious response is the Great Green Wall initiative, started by African Union countries in 2007. The plan was to plant an 8,000 km long band of trees, grassland and other green features across the southern edge of the Sahara to stop desertification. Progress has been mixed: tree-planting in the most arid areas has failed because the rainfall is just too low, but more sophisticated approaches using local water-harvesting techniques and traditional farming methods have produced striking successes in some regions. Niger has restored over 5 million hectares of degraded land through farmer-led techniques.

The biggest country in the Sahara is Algeria. Just to the north sit the Atlas Mountains.

Geography

The Sahara covers approximately 9.2 million square kilometres across North Africa — roughly the size of the United States. Despite its reputation as an endless sea of sand, only about 25% is actually sandy (erg). The rest is rocky plateau (hamada), gravel plains (reg), dry valleys (wadis), salt flats and even mountains — the Ahaggar range in Algeria reaches 2,908 metres. The Nile, flowing through the eastern Sahara, is the only permanent river crossing the desert.

Climate

The Sahara is extremely hot and dry. Summer temperatures regularly exceed 50°C at the surface, with the world's highest reliably recorded air temperature of 58°C measured in Libya in 1922 (though disputed). Nights can be surprisingly cold — temperatures drop below 0°C in winter in higher areas. Annual rainfall averages just 25 mm across most of the desert, and some areas receive no rainfall for years at a time.

Wildlife and plants

Despite its harshness, the Sahara supports around 70 mammal species, 90 bird species and 100 reptile species. The fennec fox — the world's smallest fox — survives the heat with enormous ears that radiate body heat. The dromedary camel can go days without water. The Saharan silver ant is the world's fastest ant and forages in midday heat that kills almost everything else. The addax antelope can survive without drinking water, extracting moisture from plants.

History

The Sahara was not always a desert. Between about 11,000 and 5,000 years ago, the "African Humid Period" saw the Sahara covered in grasslands, lakes and rivers — the Saharan inhabitants left rock art depicting hippos, crocodiles and cattle across what is now barren rock. Ancient trade routes crossed the Sahara for millennia, with camel caravans carrying gold, salt and slaves between West Africa and Mediterranean civilisations.