The Perito Moreno Glacier is a glacier located in the Los Glaciares National Park in southwest Santa Cruz, Argentina. It is one of the most important tourist attractions in the Argentine Patagonia.
The 250 km2 (97 sq mi) ice formation, and 30 km (19 mi) in length, is one of 48 glaciers fed by the Southern Patagonian Ice Field located in the Andes system. This icefield is the world's third largest reserve of fresh water.
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.
Pressures from the weight of the ice slowly pushes the glacier over the southern arm of Lago Argentino damming the section and separating it from the rest of the lake. With no outlet, the water-level on the side of the lake can rise by as much as 30 meters above the level of the main body of Lake Argentino. Periodically, the pressure produced by the height of the dammed water breaks through the ice barrier causing a spectacular rupture, sending a massive outpouring of water from the Brazo Rico section to the main body of Lake Argentino. As the water exits Brazo Rico, the scored shoreline is exposed, showing evidence of the height of the water build-up. This dam–ice-bridge–rupture cycle recurs naturally between once a year to less than once a decade. The last rupture occurred on January 19th 2013. It ruptures, on average, about every four to five years.