Tourists watch a tunnel open in the Perito Moreno glacier in a process of an unexpected rupture during the southern hemisphere's winter months, near the city of El Calafate in the Patagonian province of Santa Cruz, southern Argentina, July 6, 208. The Perito Moreno glacier, part of the Los Glaciares National Park, a World Heritage site, measures 250 square kilometers (97 square miles), and is one of the few glaciers which advances instead of retreating. [Agencies]