Introduction
Perito Moreno Glacier is a 250 km² river of ice flowing from the Southern Patagonian Ice Field into Lago Argentino. It is one of 48 glaciers fed by this ice field, the third largest reserve of freshwater in the world after Antarctica and Greenland.
Unlike the vast majority of glaciers worldwide, Perito Moreno is in a state of equilibrium, neither retreating nor significantly advancing over recent decades. Its spectacular calving events, where enormous chunks of ice crash into the lake, draw hundreds of thousands of visitors to Los Glaciares National Park each year.
Geography & Dimensions
- Length: 30 km
- Width at Terminus: 5 km
- Ice Depth: Up to 170 m above water, 700 m total
- Elevation Range: 185 m (terminus) to 2,950 m (accumulation zone)
- Location: Santa Cruz Province, Argentina (50.5°S)
Perito Moreno stretches 30 kilometers from its source high in the Andes to its terminus at the Brazo Rico arm of Lago Argentino. The ice face towers roughly 70 meters above the waterline, though the glacier extends another 100 meters or more below the surface.
The glacier sits within Los Glaciares National Park, a UNESCO World Heritage Site since 1981. Its terminus periodically advances far enough to dam the Brazo Rico arm, causing water levels to rise dramatically until the ice bridge ruptures in explosive calving events.
Formation & Movement
- Ice Speed: ~2 m per day at center
- Snow Accumulation Zone: Above 1,500 m elevation
- Age of Deepest Ice: Estimated 700+ years
- Annual Snowfall: Accumulation zone receives ~8,000 mm water equivalent
Perito Moreno forms from compacted snowfall in the high Andes. Snowfall in the accumulation zone is compressed into firn and eventually dense glacial ice under its own weight, a process that takes decades.
The glacier flows downhill under gravity at approximately two meters per day in its central section. Friction against the valley walls slows the edges, creating the crevasses and seracs that give the ice surface its dramatic, jagged appearance. This relatively fast flow rate is key to why the glacier maintains its size despite calving losses.
Climate Impact & Stability
- Status: In approximate equilibrium (stable)
- Ice Field Source: Southern Patagonian Ice Field (13,000 km²)
- Temperature Sensitivity: Fed by heavy Pacific precipitation (~5,000-8,000 mm/yr)
- Last Major Rupture Event: March 2016
While most of the world's glaciers are in retreat, Perito Moreno has maintained a roughly stable terminus position since measurements began in the early 20th century. Scientists attribute this to the enormous snowfall the Southern Patagonian Ice Field receives from Pacific weather systems, which compensates for melting at the lower terminus.
Climate change still poses a long-term threat. Warming temperatures are raising the snow line and increasing summer melt rates. The Southern Patagonian Ice Field as a whole has been losing mass, and several neighboring glaciers like Upsala and Viedma are retreating rapidly, making Perito Moreno's stability an exception rather than the rule.
Surrounding Ecology
- Biome: Subantarctic Magellanic forest
- Key Tree Species: Lenga beech (Nothofagus pumilio), Guindo (N. betuloides)
- Wildlife: Andean condor, huemul deer, puma, Magellanic woodpecker
- Lake: Lago Argentino (1,466 km²)
The forests surrounding Perito Moreno are dominated by southern beech species adapted to cold, wet conditions. Lenga beech turns brilliant orange and red in autumn, creating a vivid contrast against the blue-white ice.
Lago Argentino, the largest lake in Argentina, receives meltwater from several glaciers. Its milky turquoise color comes from glacial flour, finely ground rock suspended in the water. The lake and surrounding forests support diverse birdlife including Andean condors, austral parakeets, and the striking Magellanic woodpecker.
Exploration & Tourism
- Annual Visitors: ~700,000
- Access: El Calafate airport, 80 km away
- Viewing: Walkways, boat tours, ice trekking
- UNESCO Status: World Heritage Site since 1981
Perito Moreno is the most accessible major glacier in Patagonia. An extensive network of walkways along the opposite shore provides panoramic views of the ice face, and visitors frequently witness calving events where house-sized blocks of ice thunder into the lake.
Ice trekking tours allow visitors to walk on the glacier itself with crampons, exploring crevasses and moulins (vertical shafts carved by meltwater). The town of El Calafate serves as the gateway, with regular flights from Buenos Aires. The glacier's rupture events, which occur irregularly every few years, are major spectacles that attract global media attention.
Key Facts
- Perito Moreno is one of the few glaciers on Earth that is not retreating.
- The glacier advances about 2 meters per day but loses a similar amount to calving.
- Its ice face rises roughly 70 meters above the waterline of Lago Argentino.
- The Southern Patagonian Ice Field feeding it is the third largest freshwater reserve on Earth.
- Rupture events occur when the glacier dams the Brazo Rico arm and the ice bridge collapses.
Fun Facts
- The thunderous crack of a calving event at Perito Moreno can be heard several kilometers away.
- The glacier is named after Francisco Moreno, an Argentine explorer who studied Patagonia in the 19th century and helped settle the border dispute with Chile.
- Some ice at the bottom of the glacier fell as snow over 700 years ago.
- During a rupture event in 1966, the lake level behind the ice dam rose by over 30 meters before the bridge collapsed.
Final Thoughts
Perito Moreno Glacier stands as a remarkable exception in a world of retreating ice. Its stability, dramatic calving events, and stunning Patagonian setting make it one of the most important and accessible glaciers on the planet, a living laboratory for understanding glacial dynamics in a changing climate.
