Walking in the shadow of a great volcano

On a ledge just inside the lip of Chile's Quizapu volcanic crater, Philipp Ruprecht was furiously digging a trench. Here at an elevation of 10,000 feet, a 1,000-foot plunge loomed just yards away, and wind was whipping dust off his shovel. But the volcanologist was excited. Ruprecht had just found this spot, topped with undisturbed wedding-cake layers of fine, black material that the crater had vomited from the deep earth