Chile’s Atacama Desert, the driest nonpolar desert on Earth, stretches across a roughly 600-mile (1,000 kilometers) tract of land wedged between the coastal Cordillera de la Costa mountain range and the Andes Mountains. The Atacama is the oldest desert on Earth and has experienced semiarid conditions for roughly the past 150 million years.
Scientists estimate that the desert’s inner core has been hyperarid for roughly 15 million years, thanks to a combination of unique geologic and atmospheric conditions in the area. This perfectly parched inner-desert region spans roughly 50,000 square miles (130,000 square km).
The Atacama is tucked in the shadow of the snow-capped Andes Mountains, which block rainfall from the east. To the west, the upwelling of cold water from deep in the Pacific Ocean promotes atmospheric conditions that hamper the evaporation of seawater and prevent the formation of clouds and rain.
The temperatures in the Atacama are comparatively mild throughout the year. The average temperature in the desert is about 63 degrees F (18 degrees C).
The outskirts of the Atacama are home to communities of organisms that have adapted to thrive in harsh conditions. The desert’s hyperarid core, however, is largely devoid of plant and animal life, save for a few strains of microbial life.
On average, the driest part of the Atacama receives less than a millimeter of rain each year. In rare cases, torrents of rain do fall, and life responds.