The Salar de Gorbea, some 13,000 feet above sea level, in the Atacama Desert of northern Chile, is like another planet. Active volcanoes dominate the muted, but colorful, vegetation-free landscape. In a few places, groundwater collects in salty, acidic pools. It evaporates in the sun, leaving behind gypsum crystals as big as your feet that protrude from the ground like daggers.

But they don’t stay put. Somehow they are scattered all over the place. And about three miles away it’s even weirder: It looks as if someone intentionally swept them into 15-foot-high piles, with some crystals merged together like giant gobs of rock candy.