Chile's Atacama Desert—the world's highest and driest—is packed with what's been called "white gold": nitrate deposits that have been historically important. The nitrates found there were key to World War I bombs and battling iodine deficiency, LiveScience reports. But until now, just how the material got there has been something of a mystery. "From a geological perspective," Chilean researcher Martin Reich tells the website, the deposits "shouldn't be there."
Previously, the best guess was that the Atacama nitrates arrived through evaporation, carried by sea spray or rain when the region was wetter. But Reich and his team have a different explanation, based on a chemical analysis of the nitrates. They argue that some 20 million years ago, precipitation in the Andes Mountains leached the minerals from rocks into the soil. Groundwater then drove them into what's now the desert. Eventually, the region became drier and the mountains grew taller. That should have shifted the groundwater westward—but the mountains of the Chilean Coast Ranges blocked such movement; instead, the groundwater rose and evaporated. What remained was the "white gold," LiveScience explains.