Perito Moreno Glacier

By Dr. Crit Minster

Once every few years, the water pressure in the Brazo Rico sector of Lake Argentino becomes too intense for the Perito Moreno Glacier to contain. The forward edge of the glacier builds up over time, connecting the ageless mountain rock to the massive South Patagonian Icefield, severing the Brazo Rico from the rest of the lake. The trapped water can rise 30 meters (about 90 feet) over the course of several years before the ice gives way in an awesome display of nature’s might, bursting in a spectacular thunderclap of massive chunks of ice, roaring water, rocks and debris. If you’re lucky enough to witness this awe-inspiring natural wonder, you’ll never forget it.

The Perito Moreno Glacier is located in Los Glaciares National Park in the southwestern part of Santa Cruz province, Argentina. When it snows high in the Patagonian Andes, the snow and ice does not melt. Rather, it accumulates, forming the massive South Patagonian Icefield, a glacier system that straddles Argentina and Chile. The enormous pressure of tons of snow and ice compresses the existing ice and gives it a distinctive bluish tint. At such great pressures, the frozen water actually flows, inching out of the Andes and into the valleys where it melts, forming lakes and rivers. The Perito Moreno Glacier is one of 48 such outlets for the South Patagonian Icefield.

This hulking hunk of ice is named for Dr. Francisco Pascasio “Perito” Moreno, an Argentine explorer who traveled through much of his nation’s rugged wilderness in the late 19th century. In 1903, he donated some land to the Argentine government that would later form the nucleus of Nahuel Huapi National Park. Naming the majestic glacier after him was a fitting tribute to the man who spent a lifetime exploring Argentina’s interior and preserving it for future generations.

Visitors who are not fortunate enough to see the great wall of ice give way need not fret: the glacier is advancing into Lake Argentino at an approximate speed of two meters (six feet) per day. Believe it or not, however, this massive ice bed never really progresses forward; huge slabs of ice break off at more or less the same rate as the glacier creeps into the lake. Every few minutes great chunks of ice, some weighing as much as several tons, crack off the glacial face and tumble into the lake with a roar. These massive frozen blocks bob around in the lake as icebergs for a while, slowly melting.

There are observation platforms to watch this process, and many visitors take tour boats into the lake. The boats keep a respectful distance—you never know when a mini iceberg is going to break off—but the views are spectacular. Like watching rain on a lake or a brightly burning bonfire, witnessing the glacier groan, creak and crumble into the lake is very hypnotic. Perito himself would be pleased to see the looks of awe and fascination on the faces of those lucky enough to experience the natural wonder that bears his name.