On the southwestern Argentine side, there are more than 300 glaciers, some of them in the Parque Nacional Los Glaciares, Glacier National Park, extends for 217 miles (350 km) along the Andes. Los Glaciares (map, #2) is a UNESCO World Heritage site, and includes ice fields covering about 40% of the surface, two lakes and 47 major glaciers. Thirteen glaciers reach toward the Atlantic, while the glaciers Perito Moreno, Mayo, Spegazzini, Upsala, Agassiz, Onelli, Ameghino feed the lakes in the park. Among them is Lago Argentina, the largest lake in Argentina, and already 15,000 years old. Lago Viedma, and Lago Argentina flow into the río Santa Cruz which runs east into the Atlantic. Glaciar Upsala is the largest glacier in South America. It is 37 miles (60 km) long and 6 miles (10km) long. You can reach it only by boat, playing dodge'em with the icebergs, or ice islands, floating in in Lago Argentina.
The park also includes mountains, rivers, lakes and forests and reaches into the arid Patagonian steppes to the east. Among the steep, jagged granite mountain peaks Cerro Fitz Roy, also known as Chaltén at 11236 ft (3405m) and Cerro Torre at 10236 ft (3102 m). Flora and fauna include stands of beech trees, shrubs, mosses, orchids, red firebush, and guanacos, large Patagonian hares, hawks, red foxes, Magellan geese, black-necked swans, flamingos, woodpeckers, skunks, pumas, condors and the near-extinct huemel deer. The huemel is now protected as a national monument.
Within Los Glaciares park, the Parque Nacional Perito Moreno is its own entity, and a must on every visitor's list. Perito Moreno has the distinction of being the only glacier in the world to be still growing. Like the other glaciers in the region, Moreno is formed because falling snow accumulates faster than it melts. Over time, the snow compresses and gravity and the ice buildup behind the glacier force it down the mountain. The distinctive blue color comes from oxygen trapped in the snow, and the dirt and mud come from the ground and rocks the glacier gathers as it noses its way downward.
These two views of the Perito Moreno Glacier offer an inkling of the size and wonder of it. The glacier winds for 50 mi (80 km) through the cordillera until it comes to an end in Lago Argentina in a blue-ice wall 2 miles (3km) wide and 165 ft (50 m) high called the snout.
The glacier faces the Peninsula Magallanes (map, #3) across a narrow channel of water, and as it moves across the channel building an ice dam, the waters build up in an inlet called Brazo Rico until the pressure is too much. The wall collapses. This happened last in 1986 when the collapse of the dam was caught on video. (Copies of the video are available locally.) No one is sure when it will happen again, but visitors wait expectanctly.
Perito Moreno is named for Francisco Pascasio Moreno, whose nickname was Perito. More formally known as Dr. Francisco P. Moreno, Honoris Causa, (1852-1919), he was the first Argentine to travel the area and his Reminiscencias Del Perito Moreno were later compiled by his son. Moreno gave the Argentine nation the land that became Nahuel Napi National Park. Many places in southwestern Argentina are named for him. It was he who named Cerro Fitzroy after the captain of HMS Beagle.