The exceptionally arid climate of the area is inhospitable to humans, but creates an excellent location for millimeter, submillimeter, and mid-infrared astronomy.

Llano de Chajnantor is home to the largest and most expensive astronomical telescope project in the world, the Atacama Large Millimeter Array (ALMA).

The Llano de Chajnantor site itself is bounded by volcanic peaks of the Purico Complex, which have been active in the Holocene but have not erupted in historic times.

The thin atmosphere makes work difficult for humans, so much of the activity for ALMA will be conducted at a base camp in the Salar de Atacama basin at approximately 2,900 m (9,500 ft) in elevation.

[4] The dry climate of Llano de Chajnantor is due to three factors: the rain shadows created by the Andes and the Chilean Coastal Range, the inversion created by the Humboldt Current off the coast of Chile, and dry air descending between the Hadley cell and the Ferrel cell, which forms the South Pacific High.