Daniel Ruiz-Carrascal stands on a mound of jagged rocks that seem out of place in the otherwise smooth and grassy landscape. “The glacier was here in the mid-1500s,” he explains. The white peak of Nevado Santa Isabel looms a mile ahead and about 1,300 feet taller than our own dizzyingly high elevation. It’s hard to picture that white stretching all the way down to this rocky hill, burying the entire valley in ice.