Periodically the glacier advances over the kidney-shaped "Lago Argentino" ("Argentine Lake") forming a natural dam which separates the lake into two halves 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 other half. The pressure produced by the height of the dammed water finally breaks through the ice barrier underwater, leaving intact an ice bridge from the glacier to the peninsula. After some more time, the bridge is squeezed and breaks in a spectacular rupture event. This dam–ice-bridge–rupture cycle is not regular and it recurs naturally at any frequency between once a year to less than once a decade.
The last rupture occurred in March 2, 2012, and previously in 2008, 2006, 2004, 1988, 1986, 1980, 1977, 1975, 1972, 1970, 1966, 1963, 1960, 1956, 1953, 1952, 1947, 1940, 1934 and 1917. It ruptures, on average, about every four to five years.
As of February 2012, before the March 2 rupture, the glacier dammed the Brazo Rico. The water level there had risen 5.6 meters.
The Perito Moreno glacier, located 78 kilometres (48 mi) from El Calafate, was named after the explorer Francisco Moreno, a pioneer who studied the region in the 19th century and played a major role in defending the territory of Argentina in the conflict surrounding the international border dispute with Chile.
Read more about this topic: Perito Moreno Glacier
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