The Sahara, at a glance
The world’s largest hot desert, but mostly rock and gravel, not sand
~9.2 million km²
The Sahara’s area, spanning 11 North African countries.
~25%
Share of the Sahara actually covered by sand dunes (ergs).
11,000-5,000 ya
When the African Humid Period made the Sahara a green savanna.
~10%
How much the Sahara’s boundary has expanded since 1920.
How Big Is the Sahara, and What Is It Actually Made Of?
Why isn’t the Sahara the world’s largest desert, and what covers most of it?
- 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.
- 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.
- Life persists at scattered oases, including Siwa, Dakhla, and Kharga in Egypt, fed by underground water reaching the surface.
Q1. True or False: The Sahara is the largest desert on Earth, of any kind.
Q2. True or False: Sand dunes (ergs) cover only around a quarter of the Sahara.
When Was the Sahara Green, and What Changed It?
What does rock art at Tassili n’Ajjer prove about the Sahara’s past?
- 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.
- Long before any of this ended, 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.
Q3. True or False: Rock art at Tassili n’Ajjer, Algeria, depicts animals like hippos and crocodiles that no longer live there.
Q4. True or False: The Sahara’s shift from savanna back to desert was a sudden event, not a gradual cycle.
Think it through, before reading on. If the Sahara was green savanna just 5,000 years ago, and the shift back to desert followed a slow, predictable 41,000-year tilt cycle, what does that suggest about today’s “desertification” debate?
Show the explanation
It suggests the Sahara has always been a moving target, cycling between green and dry over tens of thousands of years, independent of people. That’s exactly why today’s Sahara expansion debate, covered next, has to separate the natural cycle’s share from the human-driven share, rather than treating all expansion as a new problem.
Remember the trap. The Sahel is the belt immediately south of the Sahara, not another name for the Sahara’s core or its northern Mediterranean fringe. It is a zone of ongoing desertification, distinct from the desert itself.
Is the Sahara Still Growing Today?
How much has the Sahara expanded, and what is being done about it?
- 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.
Q5. True or False: A 2018 University of Maryland study attributed about two-thirds of the Sahara’s recent boundary expansion to natural climate cycles, not human activity.
Q6. True or False: The Great Green Wall initiative has already met all of its 2030 restoration targets.
Quick Q&A
Is the Sahara the largest desert in the world?
No. It is the largest hot desert, but Antarctica and the Arctic are both larger, cold deserts by the same definition.
What covers most of the Sahara’s surface?
Rocky plateau (hamada) and gravel plains (reg); sand dunes (ergs) cover only around a quarter.
What was the Sahara like during the African Humid Period?
Green savanna with permanent lakes, including Lake Mega-Chad, roughly 11,000 to 5,000 years ago.
Is the Sahara’s expansion today mostly natural or human-caused?
A 2018 study attributed about two-thirds of its recent boundary expansion to natural climate cycles, and the rest to human-driven change.
- NDA-NA (II) 2016, Q57 — The Sahel is the semi-arid strip along the southern edge of the Sahara, not the desert’s core or its northern Mediterranean fringe, a zone of ongoing desertification, not another name for the Sahara itself. View this question on the full NDA-NA (II) 2016 paper →
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