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14.4.6. Glacier modeling

Glacier modeling

glacier is a thick mass of ice that is produced by accumulation, compaction and recrystallization of snow, which is transformed into ice, and shows evidence of flow in the past or today.

Depending on where they are located, there are two types of glaciers:

  • Cap glaciers. In areas with a polar climate, such as Greenland and Antarctica, where the ice covers the entire relief.
  • Alpine glaciers. In high mountains in less cold areas, where the snow does not melt in summer (perpetual snow).

In glacial circuses snow accumulates and becomes ice. The ice flows into the lower areas where it melts (ablation zone). Due to their solid state, the slowly descending glacial tongues of ice have great erosion and transport power, capable of dragging rocks tens of meters long, and leaving valleys in the shape of a "U". In addition, several glacial cirques generate the pyramidal peaks or horn.

Valle glaciar con forma de U

Ordesa National Park (Huesca)

The glacial tongue, drags the ice along with till (sediments) until they accumulate in the moraines . The Lateral deposits are formed by accumulation till both sides of glacial tongue. Two lateral moraines, of two contiguous tongues, can join forming a central moraine. The sediments that accumulate at the end of the tongue constitute the frontal moraine. The bottom moraine is formed by the till that remains on the surface on which the tongue moves.

It is also characteristic to find lakes at the bottom of the cirques or next to the frontal moraine. In Aragon, lakes of glacial origin are called ibones.

In periglacial areas, where the temperature is above and below 0 ºC, gelling is the main weathering process, causing scree.

Answer in your notebook

14.12.- What geological process predominates in a glacial cirque? And in a moraine?