ROUGH CUT (NO REPORTER NARRATION)<br/> <br />STORY: Huge ice chunks broke off the Perito Moreno glacier in Argentina's Patagonia on Friday, putting on a spectacular show in the glacier's cyclical pattern.<br/> <br />The glacier, a massive tongue of ice in the Rio Gallegos province that covers 97 square miles, advances yearly into a lake, known as Lago Argentino.<br/> <br />As Perito Moreno moves forward, it cuts off a river feeding the lake. Water builds up pressure and slowly undermines the ice, forming a tunnel until ice comes tumbling down.<br/> <br />The phenomenon repeats itself at irregular intervals, with the last major ice falls occurring in 2008.
