The Sahara isn’t actually the world’s largest desert. Antarctica and the Arctic are both bigger, and both count as deserts too, just cold ones. The Sahara is the largest hot desert, by a wide margin, and this article covers what that scale actually looks like on the ground.
Timeline
- c. 11,000 to 5,000 years ago: the African Humid Period. The Sahara region is savanna, dotted with lakes and rivers.
- c. 4200 BCE onward: a weakening monsoon, driven by a slow shift in Earth’s axial tilt, dries the region into desert.
- Today: the Sahara covers about 9.2 million square kilometres, across 11 countries in North Africa.
- 1920 to present: research finds the desert’s boundary has expanded by roughly 10% overall.
- 2007 onward: African nations run the Great Green Wall initiative, aiming to restore land along the Sahara’s southern edge.
Scale and Climate Need to Know
- The Sahara covers roughly 9.2 million square kilometres, spanning 11 countries across North Africa, including Algeria, Libya, Egypt, Mali, and Mauritania.
- It is the world’s largest hot desert, but not the largest desert overall. Antarctica and the Arctic are both larger, cold deserts by the same climatic definition.
- The most credible recent temperature record is 51.3°C, measured at Ouargla, Algeria, in 2018. An older, widely repeated figure of 58°C from 1922 was formally invalidated by the World Meteorological Organization in 2012.
- Desert nights can run 13 to 20 degrees cooler than the day. With almost no moisture or cloud cover, heat radiates away fast once the sun sets.
Rock and Gravel, Not Just Sand Need to Know
- Sand dunes, called ergs, cover only around a quarter of the Sahara. The rest is rocky plateau, called hamada, and gravel plains, called reg.
- The Sahara’s highest point is Emi Koussi, 3,447 metres, an inactive volcano in Chad’s Tibesti Mountains.
- The Ahaggar Mountains, in southern Algeria, hold their own high point, Mount Tahat, at around 2,900 metres.
- Famous ergs include Erg Chebbi and Erg Chigaga in Morocco, and the Grand Erg Oriental and Grand Erg Occidental in Algeria.
- Life persists at scattered oases, including Siwa, Dakhla, and Kharga in Egypt, fed by underground water reaching the surface.
The Green Sahara Good to Know
- Roughly 11,000 to 5,000 years ago, during the African Humid Period, the Sahara region looked nothing like it does today.
- It was savanna, with permanent lakes and rivers. Lake Mega-Chad, at its largest, covered around 350,000 square kilometres.
- Rock art at Tassili n’Ajjer, Algeria, a UNESCO World Heritage site, shows the proof directly. Around 15,000 paintings and engravings depict grazing antelope, giraffes, hippos, and crocodiles.
- The shift back to desert was driven mainly by a slow, roughly 41,000-year cycle in Earth’s axial tilt, which weakened seasonal monsoon rains over the region.
Test Yourself
A Desert on the Move Great to Know
- A 2018 University of Maryland study analysed 93 years of rainfall data. It found the Sahara’s boundary expanded by roughly 10% overall, and closer to 16% in summer.
- The researchers attributed about two-thirds of that expansion to natural, decades-long climate cycles, with the rest linked to human-driven climate change.
- The Great Green Wall, an African Union initiative launched in 2007, aims to restore land along the Sahara’s southern edge, across 11 Sahelian countries. Progress has been real but slow, with only a small share of its 2030 targets met so far.
- Long before any of this, the Sahara shaped African history directly. Camel caravans carried gold and salt across it for centuries, and cities like Timbuktu grew rich as trade hubs along these routes.
Leave a Reply