Tourists wait to see the rupture of the leading edge of the Perito Moreno glacier near the city of El Calafate in the Patagonian province of Santa Cruz, southern Argentina, March 2. 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. The phenomenon repeats itself at irregular intervals, with the last major ice falls occurring in 2008. The glacier collapsed on March 4, 2012, after several large chunks broke off.

The Perito Moreno Glacier in Los Glaciares National Park, in southern Argentina, completed its break in the middle of a storm when the darkness and rain conspired to frighten hundreds of tourists waiting anxiously for the show on March 4. The breakdown process, which began on Feb. 29, was caused by the pressure of water above the ice dam, which began to crack to form an arch-shaped hole that ended up weakening and finally collapsing. The natural phenomenon happens infrequently -- from once a year to less then once a decade.

The Perito Moreno glacier is seen after the rupture of a massive ice wall near the city of El Calafate in the Patagonian province of Santa Cruz, southern Argentina, March 4, 2012. The glacier, a massive tongue of ice in the Santa Cruz province that covers 250 square kilometres (97 square miles), advances yearly into a lake, known as Lago Argentino.

Protesters block a road in Puerto Aysen, Chilean Patagonia, on March 1. Residents of the Aysen region last week launched a protest demanding a subsidy for fuel and wood, vital in the southern Chile's winter with its very low temperatures.

Protesters block a road in Puerto Aysen, Chilean Patagonia, on March 1. Residents of the Aysen region last week launched a protest demanding a subsidy for fuel and wood, vital in the southern Chile's winter with its very low temperatures.

A woman protects her son as demonstrators take Ibanez bridge in Aysen, Chile, on March 1. Aysen social leaders hold meetings with Chilean Government in order to find a solution for people in that Chilean zone, asking for a better quality of life.

Protesters march during blockage in Puerto Aysen, Chilean Patagonia, on March 1. Residents of the Aysen region last week launched a protest demanding a subsidy for fuel and wood, vital in the southern Chile's winter with its very low temperatures.

In this photo taken May 4, 2011, Rozendo Sanchez, left, saddles his horse next to Nelson Gallardo, in Los Nadis, Aysen region, in Chile's northern Patagonia. Their families are two of the at least three dozen living where the multinational consortium, HidroAysen has proposed to build five hydroelectric megadams in this remote Patagonian region. If the proposal is accepted, one of the dams will flood most of Los Nadis, requiring the relocation of its residents. In the next few days, the region's Commision for Environmental Evaluation will meet to determine whether or not HidroAysen has met the environmental standards required by Chilean law for the project to proceed.

In this photo taken May 4, 2011, Elisabeth Schindele, left, a German married to Chilean Rozendo Sanchez, collects plants with her daughter Lorena Sanchez Schindele in the home she shares with her husband and two children in Los Nadis, Aysen region, in Chile's northern Patagonia. The family is one of the at least three dozen living where the multinational consortium, HidroAysen has proposed to build five hydroelectric megadams in this remote Patagonian region.

This photo taken Jan. 20, 2008 show a view of the confluence of the Baker and Chacabuco rivers on the outskirst of Cochrane, Aysen region, in Chile's northern Patagonia.

Conservationists protest against the project to build several hydroelectric power stations in the Chilean Patagonia, in Coihaique, Aisen, Chile on May 9, 2011. A USD 3.2 billion hydroelectric project billed as key to satisfying Chile's growing energy needs faces a major hurdle Monday as an environmental panel decides whether or not to give it the green light.