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Portrait of The Sahara

Geography · Physical geography

The Sahara

North Africa — spanning eleven countries from the Atlantic to the Red Sea

The largest hot desert on Earth, roughly 9.2 million square kilometres of erg, reg and hamada stretching across North Africa from the Atlantic to the Red Sea. It is not, however, the largest desert: deserts are defined by dryness rather than heat, so the polar ice sheets of Antarctica and the Arctic are both bigger. Rock art on its central plateaux records a time, a few thousand years ago, when the same ground was green.

How to spot them

  • ▸The world's largest hot desert — but only the third largest desert of any kind
  • ▸Quiz clue: 'erg', 'hamada', 'Tibesti', 'Ahaggar', 'Bodélé Depression', 'Tassili n'Ajjer'
  • ▸Its northern edge meets the Atlas Mountains; its southern fringe is the semi-arid Sahel
  • ▸Its name is simply the Arabic plural for 'deserts', which makes the usual English phrase a tautology

Key facts

The largest hot desert on Earth, covering about 9.2 million square kilometres

Comparable in area to China or to the United States

Its highest point is Emi Koussi, a volcano in the Tibesti Mountains of Chad

3,415 m; the Ahaggar (Hoggar) massif in Algeria is the other great highland block

Rock paintings at Tassili n'Ajjer show cattle, giraffes and swimmers where there is now only sand

Evidence of the African Humid Period, roughly 11,000–5,000 years ago, when monsoon rains reached far north

Phosphorus-rich dust blown from its Bodélé Depression fertilises the Amazon rainforest

Millions of tonnes a year cross the Atlantic, tracked by NASA's CALIPSO satellite

A 1922 reading of 58 °C on its Libyan edge held the world heat record until it was rescinded in 2012

The WMO threw out the El Azizia figure; the record passed to Death Valley's 56.7 °C of 1913

Only about a fifth of it is sand sea; most is stony plain and bare rock pavement

Erg is the sand sea, reg the gravel plain, hamada the rock desert

Quick-fire facts

  • •It covers roughly 9.2 million km², about a third of the African continent
  • •Antarctica and the Arctic are both larger deserts, because a desert is defined by precipitation, not temperature
  • •Its highest point is Emi Koussi (3,415 m) in the Tibesti Mountains of Chad
  • •The Nile crosses it from south to north; Lake Chad sits on its southern margin and has shrunk drastically since the 1960s
  • •The Sahel — from the Arabic for 'shore' or 'coast' — is the transitional belt along its southern edge
  • •Tassili n'Ajjer in Algeria, inscribed by UNESCO in 1982, holds one of the world's great collections of prehistoric rock art
  • •Common misconception: it is not the world's largest desert, and it is not mostly sand dunes
  • •Its name comes from the Arabic ṣaḥrāʾ, 'desert'; 'the Sahara Desert' therefore says 'desert' twice

Drill it — 8 cards

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Sources