Geology And Geophysics
Atacama Desert Chile

Why the Atacama Desert of Chile is so Dry



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Atacama Desert Chile
Gabriele Porrometo's image for:
"Why the Atacama Desert of Chile is so Dry"
Caption: Atacama Desert Chile
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The Atacama Desert is one of the driest places in the world, second only to The Dry Valleys of Antarctica. It is located in the northern part of Chile and occupies small territories in Argentina, Peru and Bolivia. It is around 621 miles in length and 93 miles at its widest. Its area is 54,000 square miles (the size of New York). The tropic of Capricorn passes through this desolate region. It is a high (many elevations are over 8,000 feet) and cold desert. The average temperatures range from 0° to 25° Celsius (32° to 75° F).

Rains and fogs are extremely rare; in fact, this desert has an average rate of less than 1 mm of rain a year. There are some weather stations in the place; however, it has never rained since their construction. The only means that give water are small and occasional mists.

It isn’t easy to survive in this place, but there is life! Despite the barren and arid landscapes, there are seals and sea lions on the coast, the South American Gray Fox, the Vicuñas (an animal similar to Llamas), the Viscacha (a rodent), vultures and lizards. However, bacteria and fungi don’t exist in these territories. Nevertheless, there are zones near isolated mountains or coastal slopes where fogs are very usual and develop small plant communities; these places are called “Lomas” (small hills). Their vegetation is typically made of cacti, Chilean mesquite, Tamarugo, Tara, Long-spine Acacias, a few lichens and others.

The insects are very few due to the climate, but a considerable community of poisonous spiders successfully developed. Some parks were created to protect this delicate wildlife: Pan de Azúcar National Park, La Chimba National Reserve and Pampa del Tamarugal National Reserve.

There are little villages near oases and mining towns, as well; most of their inhabitants have never seen a rain. Even if this region is very harsh, it has many resources: copper, sodium chloride, sodium nitrate and iodine salts.

However, why is this region so dry? The answers are multiple. First, Atacama lies on the wrong side of the Andes with regard to the prevailing winds. Therefore, when they carry moist air , they are forced to rise to pass the Andes and the moisture condenses, then turns to rain that falls on the other side of the Andes and not on the Atacama Desert. This means that it lies in a rain-shadow.  

Another reason is the Pacific Anticyclone winds that flow in this area. They blow dry air, which warms up air and makes its moisture evaporate into water vapor that doesn’t bring rain. Finally, the third and last answer lies in the Humboldt Current, an ocean current that carries cold water. This stream passes northward along the western coast of South America and cools the air above it. When air turns cold, it dries out any water left in it.

This amazing combination of the Andes, the rain-shadow, the dry winds and the Humboldt Current, makes the Atacama Desert particularly dry.

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More about this author: Gabriele Porrometo

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ARTICLE SOURCES AND CITATIONS
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