The Perito Moreno Glacier is situated in the Los Glaciares National Park in the Santa Cruz province of Argentina. One of only three glaciers in Patagonia that is still growing, it’s a key tourist attraction in the area, not only because of its size, but because it is accessibility.
The glacier's dimensions are huge and awe-inspiring. A massive 5 km (~3 mi) wide, it covers in total 250 km2 (~97 mi2). Its average height is 60 m (~197 ft) and at its deepest, it reaches 700 m (~2,297 ft).
It is one of 48 glaciers fed by the Southern Patagonian Ice Field in the Andes. This ice field alone accounts for the world's third largest freshwater reserve.
It's not completely understood why this glacier continues to move while others nearby are in retreat due to global warming. Although not visible to the naked eye, the effects are easy enough to see every four to five years, when part of the glacier sheers off and collapses into waters below. As the glacier ploughs forward, it cuts off a river than feeds the Lago Argentino. Water pressure builds up behind the dam, slowly wearing down the ice and forming a tunnel, which eventually collapses under its own weight.
Leading from the visitors’ center at the site is a walking route, allowing visitors to view its southern side and east facing edge. There are also ice-trekking tours to see the vast structure at close quarters: these can last anything from one to five hours.