A group of nuns on a day-trip bustled by on the path to the lower balcony overlooking the Perito Moreno Glacier, a spiky and lively outflow of the South Patagonian Ice Sheet in southwestern Argentina. Passing the energetic sisters going the opposite way was a chattering, uniformed group of school kids, who went unnoticed by some hand-holding teenagers and camera-toting tourist types at the rail.
Just across a narrow band of grey-green milky water was the object of their attention – the immense blue-white noisily-crackling face of the glacier, stretching back in brilliant jumbled glory for a mile or more before merging into the great ice sheet itself just visible on the horizon beyond. Considering that this is the world’s fourth largest icefield, it was a hopping place where ‘regular people’ in significant numbers interacted up-close-and-personal with one of the largest masses of ice on the planet. “The People’s Ice Sheet.”
Our first clue to the personality of this glacier came on the ‘Safari Nautico’ cruise on Lago Argentino up to the towering face of the ice (far too elegant to be called a ‘snout’).
Within 100 yards of the glacier front, over the idle of the engine, we could begin to hear the glacier muttering to itself, a snap-crackle-pop like one would hear twisting an ice cube tray. The constant multi-directional stresses on the ice from its headlong rush to the lake had led to the formation of spire-like, blue-white seracs, leaning at random angles toward and away from one another, as if uncomfortable relatives at a family dinner. And regularly, with a surprising BANG, sheets and slabs and chunks of the face would suddenly break free and slide into the water. As a dramatic accompaniment, a froth of spray shot upwards, the chunk tumbling and whirling as it floated in its new medium, and a wave pushing out from its point of contact frosted with hundreds of tiny shards and larger fragments of white. A shiny turquoise blue puzzle piece remained on the glacier’s face where the slab had been.
Perito Moreno is one of only a few glaciers in the world that is actually growing, at a rate of nearly 7 feet per day, as ice is added from the heavy precipitation at the Andes crest and flows downward to calve off in the lake. As the ice flows down from the ice sheet, the part closest to the bedrock molds itself to the shape of the rock below due to the extreme pressure from above, while the top 150 feet of ice yaws, splits and cracks is it flows over the bedrock features. The result is a mad jumble of elongated crevasses, tubular chutes and tall spires. Now these loomed more than 240 feet above us, stretching all the way across the 3 mile face of the glacier and back a mile to its connection with the ice sheet.
The Heilo Sur is the bigger of two remnant parts of the Patagonian Ice Sheet, which covered all of southern Chile as recently as 14,600 years ago. In the present day, this massive ice plateau draped over the southern Andes crest stretches about 220 miles long and 30 miles wide. Amazingly for an icecap, it encompasses a normally temperate latitude and elevation range, from latitude 48 (Paris or Vancouver BC) to 51° (Brussels or Berlin), and an average elevation of only around 4500 feet. Perhaps the presence of this huge slab of ice at this otherwise moderate latitude and elevation should not come as a big surprise, since annual precipitation in the high Andes of south Patagonia is extreme, an estimated annual average of 320 inches on the icefield plateau. Due to its proximity to Antartica and the very cold current flowing north on both sides of this narrow section of the South American continent, the temperatures on the ice sheet can regularly drop below zero even in mid-summer. Ice thickness data for this region is ridiculously difficult to find, but one measurement at the upper margin of one of the major glaciers puts it at about 2000 feet thick.
The South Patagonian ice sheet feeds 47 large glaciers, of which 13 flow to the Atlantic and 34 to the Pacific. The South Patagonia glaciers and ice sheet, and particularly Perito Moreno, remain enigmatic to glaciologists because of rapid retreats and advances in glaciers even within a few miles of each other. Perito Moreno in particular does a furious back and forth mambo, at least from a glacial perspective. One of the most exciting manifestations of this glacial dance is a phenomenon known as The Rupture.
When Perito Moreno advances as it often does, it forms a natural dam when it pushes across the arm of Lago Argentina onto the peninsula of land on the opposite side. With no escape route, the water-level on one side of the lake can rise by as much as 100 feet higher than the level of the main lake. The enormous pressure of the water wears away at the ice, creating a tunnel which sheds and sloughs until the remaining arch crashes down, and the water rushes through to re-establish its equilibrium in a spectacular event called a Rupture. Ruptures have been recorded about every 4-5 years since 1917. The most recent rupture event occurred in March 2, 2012, notably about two weeks after my first visit when I stood transfixed by the ice on display from the balcony on a sunny afternoon in mid February.
My spouse and our long-term friends Rex and Lynne had just flown the previous day through Buenos Aires into the brand new (2000) El Calafate airport, built by the Argentine tourist ministry as part of an integrated Federal Plan for Sustainable Tourism, and to attract foreign investment dollars toward the country’s tourist infrastructure. The town had clearly grown very recently into a booming gateway, serving not only the glacier tours, but also the main routes to FitzRoy to the north and Torres del Paine to the south.
Today, Glaciar Perito Moreno and the Parque Nacionale de Los Glaciares in which it resides  (a UNESCO world heritage site since 1981) are among the major tourist destinations in Patagonia, and truly a responsible-tourism success story. The “Safari Nautico” boat trip to the face of the glacier was only one of the amenities on offer. Across from the boat dock, on the opposite shore of the lake just next to the one smooth spot on the toe of the glacier, ice-trekking tours took adventurous and well-heeled parties a brief distance out on the ice, bedecked with crampons and ropes. Then, a bit further down the serpentine road into the park, was the center of the tourist complex: a visitor’s center and very impressive system of walkways and balconies constructed “for the ages” from metal grating and kid-proof metal-and-wood railings. These sturdy paths wound literally miles through the Lenga forest to several viewpoints high and low on the hill immediately across from the glacier’s face.
The crowds of Argentines piling off of buses, moving around the Visitor’s Center and bustling along the walkways illustrated the ability of this park to enable “regular people” in large numbers to interact with a huge and actively changing glacier front, the face of a continental ice cap, in ways that would not be possible elsewhere in the world. The Argentines are clearly very proud of their natural wonders and pristine parks – and this pride showed in the fact that, in the hours we walked the circuit and public areas, there was not a gum wrapper, paper cup or plastic bag – in fact not a single piece of litter – anywhere. Signs instructed tourists to pack out their trash, and amazingly, they did!
So there I was on the balcony, reluctant to move lest I miss another spectacular display at the glacier. Momentarily attention was distracted by first four, then five, then six condors circling overhead. Then CRACK!! BOOM!! SPLASH!! The crowd rushed to the rail in search of the location, and there it was, a frosty plume, a blue outline on the wall, a slowly rolling new infant iceberg, shards rolling outward from the center of the action. Though I was in the midst of that large group, the overwhelming impression was of a personal connection and a sense of awe and privilege to be this close to such a huge and totally unique natural wonder. Thank you Argentina, thank you Heilo Sur…this gift I will not forget!
 Behind only the Antartic and Greenland ice caps and the St Elias-Chugach icefield in Alaska.
 The Parque Nacionale de Los Glaciares encompasses the area between Lago Argentino, the largest lake in Argentina, in the south, and Lago Viedma in the north. The northern half includes Viedma Lake, the Viedma Glacier and area surrounding Monte FitzRoy and Cerro Torre. The southern part includes Lake Argentino and its glaciers: Perito Moreno, Upsala and Spegazzini.