Introduction to glaciers
There are about 275,000 glaciers on the planet, but few people get the chance to see one up close. If you have never seen one, you have probably heard of them as one of the thermometers of global warming. In El Chaltén you will have them in sight on almost every hike.
Survivors of the last ice age
Glaciers are very sensitive to changes in climate. In recent decades many have disappeared, and almost all have lost volume as temperatures rose at every latitude over the last century.
Their ecological value is less well known: glaciers and the great ice sheets hold about 70% of the planet’s fresh water (during the last ice age, some 20,000 years ago, it was around 85 to 90%). In a world where drinking water is increasingly scarce, they are an essential reserve for the future.
Glaciers and the great ice sheets hold about 70% of the planet’s fresh water.
Today’s glaciers are a legacy of the ice ages, cold periods lasting thousands of years in which ice covers a much larger part of the planet. Between them come warmer periods, like the present one, when the ice retreats. The last ice age reached its greatest extent some 20,000 years ago, an instant in geological terms: at that time ice covered about a quarter of the land. The glaciers of Patagonia are, to a large extent, its survivors.
How a glacier forms
A glacier begins to form where snow lasts all year round because it is too cold for it to melt. In these areas, called accumulation zones, each winter’s snow is added to the last and is compressed under its own weight.
Under pressure, the snow crystals lose the air between them and merge into larger, denser grains. Light, white snow thus turns into firn, an intermediate stage between snow and ice that is denser and more opaque.
As compression squeezes out the last air bubbles, the firn turns into glacial ice, with its characteristic blue color. The color comes from the very dense ice absorbing the red tones of light and letting mostly blue through: the less air it holds, the deeper the blue. The whole process can take decades or centuries.
Rivers of ice
At first sight glaciers look motionless, but they are always moving. From the heights where they form, they flow downhill under gravity, like rivers of ice following the slope of the land. Lower down, in the ablation zone, the ice melts or breaks away.
If a glacier receives more snow than it loses, it advances; if it loses more than it receives, it retreats. Many end in lakes, lagoons or the sea, where their front breaks off into blocks of ice: icebergs.
Sculptors of the landscape
If liquid water can shape coastlines and deltas, imagine the power of water in solid form. Like giant bulldozers, glaciers were, together with volcanoes and the movement of continental plates, the main forces that shaped the landscape of Southern Patagonia.
As they retreated they left U-shaped valleys, lakes that filled the basins they had carved out (such as Viedma and Argentino), fjords, and moraines: ridges of rock and sediment they pushed or carried along. Laguna Torre, for example, is held back by a moraine. Although much smaller than during the great ice ages, glaciers are still at work.
Glaciers near El Chaltén
El Chaltén lies in the northern sector of Los Glaciares National Park, on the edge of the Southern Patagonian Ice Field. These are some of the glaciers you can see:
- Grande Glacier, which flows into Laguna Torre, at the foot of Cerro Torre.
- Los Tres Glacier, hanging above Laguna de los Tres, at the foot of Fitz Roy.
- Piedras Blancas Glacier, with its viewpoint on the way to Laguna de los Tres.
- Huemul Glacier, on the shore of Lago del Desierto.
- Viedma Glacier, one of the largest in Argentina, visited by boat across Lake Viedma.
When you see them, remember you are looking at ice that fell as snow centuries ago, and that is still on the move.
Frequently asked questions
Updated: November 3, 2026
On day hikes you can see Grande Glacier from Laguna Torre, Los Tres Glacier from Laguna de los Tres, Piedras Blancas Glacier from its viewpoint and Huemul Glacier at Lago del Desierto. Viedma Glacier, one of the largest in Argentina, is visited on a boat trip across Lake Viedma.
Because it is very dense ice with almost no air bubbles. As light passes through it, the red wavelengths are absorbed and mostly blue reaches our eyes. The denser and older the ice, the deeper its blue.
Yes. Although they look still, they move all the time under their own weight, following the slope of the land like rivers of ice. When they reach a lake, their front breaks off into blocks of ice: icebergs.
Glaciers and the great ice sheets hold about 70% of the planet’s fresh water. During the last ice age, some 20,000 years ago, that share was around 85 to 90%.
Learn more
- Boat trip to Viedma Glacier
Excursion from El Chaltén - Piedras Blancas Glacier
Self-guided hike to the viewpoint - Huemul Glacier
Hike at Lago del Desierto - The National Park
Los Glaciares, a World Heritage Site
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From the Southern Ice Field to the Atlantic Ocean: the journey of El Chaltén’s water and how to protect it on the trails. - Birdwatching
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