Earth and Moon

Glacial erosion

Glacial erosion

Glaciers are erosive agents of great importance that, in the past, modeled a good part of the landscapes that we now know in medium and high latitudes across the planet.

The huge masses of ice moving slowly due to gravity carry out a task of relentless wear on the lands where they slide, which can be easily observed in those regions where the glaciers have disappeared. Ice is capable of cutting or plucking huge rocks that other erosive agents could not.

Parts of a glacier

As a glacier descends through a valley or advances through a wide area, in the case of large ice tracts, the terrain is modeled. Move the rocks it finds in its path and the ice breaks and drags the underlying ones. The rocks immersed in the bottom of the glacier act as abrasive particles, by sanding and polishing the bedstone on which it travels.

At the head of the valley of a glacier, the walls are eroded with a semicircular shape called the glacier circus. The progressive and simultaneous erosion of these walls on different sides of a mountain can give rise to what is known as a horn (horn) or pyramidal peak. The valleys through which a glacier has passed are U-shaped instead of the V-shaped, typical of the erosion of river valleys.

Frequently, the glacier valley is excavated so deeply that the mouths or mouths of the tributary valleys are at a higher level with respect to the bottom of the glacier channel, causing the so-called hanging valleys. The fjords are glacial valleys partially flooded by the sea.


A form of erosion different from glaciers, but also caused by the accumulation of water in the solid state, are the avalanches. An avalanche is the detachment of large masses of ice and snow that descends from the summits to the valleys. In its wake, an avalanche drags the vegetation, leaving a trail of bare land where erosion can more easily act.

The avalanches occur when a lot of snow accumulates in an area of ​​high slope, especially when it is deposited on another layer of different consistency that can serve as a sliding surface, remaining in an unstable balance.

The avalanche of the avalanche can have diverse origin. It can occur spontaneously when the weight of a layer itself exceeds the frictional force that kept it at rest. Also avalanches occur in the time of thawing, by decreasing the fixing force. Even for skiers or vibrations of any kind.

A small mass of snow starts the descent. By supporting your weight on another makes it also detach. Thus, as it descends, new masses are incorporated until it can acquire a large volume. It is, therefore, one of the few forms of erosion that act violently, in a short time.

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