Standing some four kilometers high, South America's Andes are some of the grandest peaks in the world. Like other, smaller ranges, they reside on the boundary of two tectonic plates, the subduction of which thrust the earth upward. But how the Andes attained their great size requires additional explanation.
This, according to Simon Lamb of Oxford University and Paul Davies of the University of California at Los Angeles, is where climate comes in. The authors suggest that the cooling of water in the so-called Peru-Chile current system (presumably a consequence of a global cooling phase that began perhaps 40 million years ago, during the Eocene epoch) triggered the drying of the west coast of South America. The resulting reduction in rainfall, they argue, would have greatly reduced the amount of sediment washed into the underwater plate interface, depriving it of lubrication. This, in turn, had the effect of "raising sheer stress to the levels required to push up and support the high Andes." --Kate Wong