Aerial view of Lake Viedma and Viedma Glacier, Santa Cruz Province. Southern Patagonian Ice Field, Los Glaciares National Park. Patagonia, Argentina 2011 © Nora de Angelli / www.noraphotos.com
Parque Nacional Los Glaciares (Spanish: The Glaciers) is a national park in the Santa Cruz Province, in Argentine Patagonia. It comprises an area of 4459 km². In 1981 it was declared a World Heritage Site by UNESCO.
The national park, created in 1937, is the second largest in Argentina. Its name refers to the giant ice cap in the Andes range that feeds 47 large glaciers, of which only 13 flow towards the Atlantic Ocean. The ice cap is the largest outside of Antarctica and Greenland. In other parts of the world, glaciers start at a height of at least 2,500 meters above mean sea level, but due to the size of the ice cap, these glaciers begin at only 1,500m, sliding down to 200m AMSL, eroding the surface of the mountains that support them.
Los Glaciares, of which 30% is covered by ice, can be divided in two parts, each corresponding with one of the two elongated big lakes partially contained by the Park. Lake Argentino, 1,466 km² and the largest in Argentina, is in the south, while Lake Viedma, 1,100 km², is in the north. Both lakes feed the Santa Cruz River that flows down to Puerto Santa Cruz on the Atlantic. Between the two halves is a non-touristic zone without lakes called Zona Centro.
The northern half consists of part of Viedma Lake, the Viedma Glacier and a few minor glaciers, and a number of mountains very popular among fans of climbing and trekking, including Mount Fitz Roy and Cerro Torre.
The southern part has, as well as a number of smaller ones, the major glaciers which flow into Lake Argentino: Perito Moreno Glacier, Upsala Glacier, and Spegazzini Glacier. Typical excursion boats travel between icebergs to visit Bahía Onelli, and the otherwise inaccessible Spegazzini and Upsala. The Perito Moreno is reachable by land.
Viedma Glacier is a large glacier that is part of the huge Southern Patagonian Ice Field, located at the southern end of mainland South America. Viedma Glacier is a valley glacier and its moraine-rich terminus flows into the western end of Lake Viedma, which is fed primarily by its melting ice. Viedma Glacier is located in Los Glaciares National Park, in the Patagonia region of Argentina, which was declared a World Heritage Site in 1981. The Southern Patagonian Ice Field is 13,000 square kilometres (5,000 sq mi); Viedma Glacier is one of the Ice Field's 48 outlet glaciers that have more than 20 square kilometres (7.7 sq mi) of ice field area each.
Viedma Glacier's glacier terminus is about 2 kilometres (1.2 mi) wide at the point it enters Lake Viedma. Chunks of ice fall off the terminus and float off into the lake, eventually melting. Glacial moraines are glacial debris of soil and rock that collect in front of, and along the sides of, the glacier as it flows across the land.
The dark parallel lines inside the white central mass of the Viedma Glacier show where the debris-filled moraines have become entwined within the center of the new glacial ice mass as it forms. At right angles to the glacial moraines in the middle, crevasses, large, canyon-sized cracks, are apparent in the grey-brown ice that can be seen along the sides of the glacier. These cracks are formed from the stress arising between ice along the valley walls (that is slower moving as the friction is greater) and the relatively fast moving ice at the glacier's center. On the southwestern side of the glacier terminus, calving of ice is visible. The glacier terminus ends in a cliff.