As the Pleistocene ended and the Campo de Hielo Sur receded, it left behind the two huge glacial troughs that are now Lago Argentino and, to the north, the roughly parallel Lago Viedma. While these lakes lie only about 250 meters above sea level, the Andean summits along the border rise to 3,375 meters on Cerro Fitz Roy and nearly as high on pinnacles such as 3,102-meter Cerro Torre, which match Chile’s Torres del Paine for sheer majesty.
Most of these bodies of water lie beyond park boundaries, but the eastern Andean slopes still contain their remnants, some of the world’s most impressive and accessible glaciers. Thirteen major glaciers flow toward the Argentine side, including the benchmark Glaciar Perito Moreno. Ice covers 30 percent of the park’s surface.
Despite its accumulated snow and ice, the Argentine side is drier than the Chilean, receiving only about 400 millimeters of precipitation on the eastern steppe, rising to about 900 millimeters at its forested western elevations. The warmest month is February, with an average maximum temperature of 22°C and a minimum of 9°C; the coolest is August, when the maximum averages only 5°C and the minimum is -1°C. As elsewhere in Patagonia, it gets ferocious winds, strongest in spring and summer.
Flora and Fauna
Where rainfall is insufficient to support anything other than coirón bunch grasses and thorny shrubs such as the calafate (Berberis buxifolia) that gave the nearby town its name, the guanaco grazes the Patagonian steppe. Foxes and Patagonian skunks are also conspicuous, the flightless rhea or ñandú scampers across the open country, the bandurria (buff-necked ibis, with its conspicuous curved beak) stalks invertebrates, and flocks of upland geese browse the swampy lakeshores. The Andean condor soars above the plains and even the highest peaks, occasionally landing to feast on carrion.
In the forests, the predominant tree species are the southern beeches lenga and the coigüe, also known here as guindo. The puma still prowls the forest, while the huemul and perhaps the pudu survive near Lago Viedma. Squawking flocks of austral parakeets flit among the trees, while the Patagonian woodpecker pounds on their trunks. Perching calmly, awaiting nightfall, the austral pygmy owl is a common late-afternoon sight.
Along the lakeshores and riverbanks, aquatic birds such as coots and ducks are abundant. The most picturesque is the Patagonian torrent duck, which dives for prey in the rushing creeks.
Excerpted from the Fourth Edition of Moon Patagonia.