Perito Moreno Glacier Collapse

The blue ice of Perito Moreno Glacier in the southern Andes Mountains, near Santa Cruz, Argentina, drives thousands of tourists every year. It's but one of nearly 50 glaciers fed by the Southern Patagonia Ice Field. Although glacier recession has been noteworthy in southern Patagonia during the past three decades, Perito Moreno has actually been growing.

Periodically the glacier advances over the L-shaped lake Lago Argentino forming a natural dam which separates the two halves of the lake when it reaches the opposite shore. With no escape route, the water-level on the Brazo Rico side of the lake can rise by up to 30 meters above the level of the main lake. The enormous pressure produced by the height of the dammed water finally breaks the ice barrier holding it back, in a spectacular rupture event. This rupture cycle is not regular and it recurs naturally at any frequency between once a year to less than once a decade.

This year around 2,500 tourist were fortunate to witness the event. The crowds cheered as the 97-square-mile glacier splintered and ice crashed down. The glacier first ruptured in 1917, taking with it an ancient forest of beech trees. The last rupture occurred two days ago in March 2, 2012, and previously in 2008. Altogether 21 ruptures has been recorded since 1917.

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