Atacama Desert

The Atacama Desert in northern Chile is the driest non-polar desert in the world. Some weather stations in the Atacama have never recorded measurable rain in over 100 years. The Atacama sits between two mountain ranges, in a perfect "rain shadow" where moisture from neither the Pacific Ocean nor the Atlantic Ocean can reach. The desert is also one of the best places on Earth for looking at the stars.

  • Areaapprox. 105,000 km²About the size of Iceland
  • CountryChileA long strip along the Pacific coast
  • RainfallAlmost zeroSome areas have never recorded rain
  • Driest place everYungay (Chile)No rain measured in 400 years
  • Highest pointLlullaillaco6,739 m, an Andean volcano
  • Famous forAstronomyDriest, clearest skies on Earth

Where the Atacama fits in

Area (million km²)
Sahara9.2
Gobi1.3
Mojave0.16
Atacama0.105

The Atacama is small by area but extraordinary in its dryness. It is by far the driest non-polar desert on Earth.

Why is the Atacama so dry?

The Atacama is dry because of a perfect combination of geography.

  • The Andes mountains to the east block moist air from the Amazon basin from reaching the desert.
  • The Chilean Coast Range mountains to the west block moist air from the Pacific from reaching far inland.
  • The cold Humboldt Current along the Chilean coast cools the air over the Pacific, so it cannot hold much moisture in the first place.

The result is a desert so dry that some parts have never had measurable rain in the entire period of European observation.

The driest place on Earth

The driest place in the Atacama is a region called Yungay. Scientists studying soils in Yungay have found no measurable rainfall in the years since records began. Geological evidence suggests that parts of the Atacama have been hyper-arid (almost no rain) for at least 3 million years, and possibly for 15 million. The dry conditions are so extreme that NASA uses the Atacama as a test site for instruments designed to look for life on Mars, because Atacama soil is the closest analogue to Martian soil on Earth.

Fact Despite the dryness, the Atacama has its own famous spectacle called the "desierto florido" or "desert in bloom". Every 5 to 10 years, a slightly wetter winter triggers millions of dormant wildflower seeds to germinate, covering the desert in a carpet of pink, white, yellow and purple flowers. The next bloom is unpredictable.

People of the Atacama

The Atacama has been inhabited for thousands of years. The Chinchorro people made the oldest known mummies in the world here, around 7,000 years ago (older than any Egyptian mummy). The Atacameños, the indigenous people of the area, still live in small oasis towns. Modern cities in the Atacama include Antofagasta and Calama, which exist mainly because of the desert's vast mineral wealth.

Astronomy in the Atacama

The combination of high altitude, low humidity, almost no rain and few cities (so very little light pollution) makes the Atacama one of the best places on Earth for astronomy. Several of the world's largest observatories sit in the desert, including the European Southern Observatory facilities and the ALMA array (a giant network of 66 radio telescopes at 5,000 metres altitude). The future Extremely Large Telescope, which will be the largest optical telescope ever built when finished, is also under construction in the Atacama.

Did you know? The Atacama is one of the world's biggest sources of copper. Chile is the largest copper-producing country on Earth, and the Atacama's Chuquicamata mine is the largest open-pit copper mine in the world (an enormous hole approx. 4 km long and over 1 km deep).
Deeper dive: the Mars analogue, the lithium triangle and the Chinchorro mummies

The Atacama is the most thoroughly studied Mars analogue on Earth. NASA and the European Space Agency send teams to the desert regularly to test instruments and techniques planned for Mars missions. The Atacama's soils are similar to those of Mars in several ways: very low organic content, high concentrations of perchlorate salts, extreme dryness, and high UV radiation due to the thin air and lack of clouds. The Atacama Rover Astrobiology Drilling Studies (ARADS) used a Mars-style drilling rover to look for microbial life under the desert surface; researchers found a thin layer of salt-tolerant microbes living a few centimetres down, the kind of life that might be found on Mars if any exists at all.

The Atacama is part of what is sometimes called the "lithium triangle", an area covering northern Chile, southern Bolivia and northwestern Argentina that contains over half of the world's known lithium reserves. Lithium is essential for the rechargeable batteries that power electric cars, smartphones and laptops. Demand for lithium is rising as the world shifts to electric vehicles, and Chile is one of the world's biggest producers. Lithium is extracted from underground brines by pumping them into large surface evaporation pools where the water evaporates over many months. This process uses huge amounts of water (in an already desperately dry region) and is controversial for its environmental impact.

The Chinchorro mummies are the oldest known mummies in the world. The Chinchorro people lived along the coastal Atacama from approx. 7,000 to 1,500 BC. They mummified their dead through a complex process that involved removing the internal organs, replacing them with grass or ash, and reassembling the body around a wooden frame. The dry desert air preserved many mummies perfectly. The earliest Chinchorro mummies are around 7,000 years old, around 2,000 years older than the earliest Egyptian mummies. Chinchorro mummified ALL their dead, including babies, not just rulers (unlike the Egyptians). The mummies were designated a UNESCO World Heritage Site in 2021.

The country is Chile. The mountain range that helps create this desert is the Andes.

Geography

The Atacama Desert runs for about 1,600 km along the Pacific coast of South America, primarily in northern Chile. It covers approximately 128,000 km² and sits at high altitude (average 2,400 m above sea level), trapped between the Pacific Ocean coastal range and the Andes mountains. The landscape includes salt flats (salares), volcanoes, geysers, pink flamingo lakes and vast arid plains.

Climate

The Atacama is the driest non-polar desert on Earth. The Atacama plateau averages less than 1 mm of rainfall per year, and some weather stations have never recorded any rain at all. Despite being coastal, it is kept dry by the cold Humboldt Current which prevents moisture from rising off the Pacific. Temperatures are mild due to the altitude and coastal influence, typically 0–25°C.

Wildlife and plants

Despite its extreme aridity, the Atacama supports vicuñas, guanacos, flamingos (three species nest in its salt lakes), Andean foxes, viscachas (rabbit-like rodents), and dozens of lizard species. The coastal fogs support a unique community of cacti and bromeliad plants called the loma ecosystem. The hyperarid core is nearly lifeless, but microbes live in salt crystals and rocks.

History

The Atacama has been inhabited for over 10,000 years. The Atacameño people built elaborate irrigation systems, traded across the Andes and were eventually absorbed into the Inca Empire. The desert became critical during the nitrate mining boom of the 19th century — the "white gold" of sodium nitrate fertiliser made fortunes and triggered wars. The War of the Pacific (1879–1884) was fought partly for control of Atacama nitrate fields.