Atacama Desert

The Atacama lies in northern Chile along South America's Pacific margin, with its northern reaches approaching the Peruvian border. Its precise boundaries vary by definition; the desert is commonly described as roughly 1,000–1,100 kilometres long. Coastal ranges, an interior depression, salt pans, gravel plains, alluvial fans and volcanic terrain toward the Andes make up a varied landscape. Elevation also changes sharply, from the coast to high Andean plateaus, so conditions differ substantially across the region.

The desert's dryness is not explained by a single cause. The Andes block much of the moisture arriving from the east, creating a rain shadow, while persistent high-pressure conditions over the South Pacific suppress rainfall. Along the coast, cold water associated with the Peru (Humboldt) Current helps form a stable layer of cool air beneath warmer air; this favors fog and low clouds but usually limits rain. The result is an exceptionally dry environment, not a place where precipitation is impossible: rare weather systems can bring rain or snow, especially at higher elevations. NASA documented a substantial high-altitude snowfall in 2025, illustrating the region's occasional climatic extremes.

Life is concentrated in places where water is briefly or locally available, including river oases, highland wetlands and coastal slopes that intercept marine fog. Along the wider arid Pacific belt of Peru and Chile, fog-fed vegetation forms patchy habitats known in Peru as lomas and in Chile as oasis de niebla. These are seasonal and unevenly distributed, rather than continuous green zones. A peer-reviewed study using two decades of satellite observations mapped more than 17,000 square kilometres of verdant and ephemeral fog-oasis vegetation across the two countries; the researchers emphasize that the total is cumulative across the study period. This helps explain why an apparently barren desert can also contain distinctive, highly localized plant communities.

The Atacama's mineral resources have shaped settlement and regional history. In the nineteenth and early twentieth centuries, saltpeter (sodium nitrate) mining supported a large industry in the Pampa; the nitrate was used as fertilizer and linked the desert to agricultural markets abroad. The UNESCO-listed Humberstone and Santa Laura works preserve part of this history: their company towns brought workers from Chile, Peru and Bolivia together and developed a distinctive Pampino culture. Copper mining remains important in northern Chile. Farming is more limited and depends on scarce water, including supplies in river valleys and oases.

The region's high, dry atmosphere makes it valuable for observing the sky. On the Chajnantor plateau, at about 5,000 metres above sea level, the Atacama Large Millimeter/submillimeter Array (ALMA) studies millimetre and submillimetre radiation that is partly absorbed by atmospheric water vapour at lower or wetter sites. Operated through an international partnership, ALMA consists of 66 antennas that can be spread across distances of up to 16 kilometres. Astronomical facilities are one example of how the desert's unusual climate and elevation serve purposes beyond mining and settlement.