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Alpine glaciers

Alpine glaciers begin high up in the mountains in bowl-shaped hollows called cirques. As the glacier grows, the ice slowly flows out of the cirque and into a valley. Several cirque glaciers can join together to form a single valley glacier. When valley glaciers flow out of the mountains, they spread out and join to form a piedmont glacier.

Valley glaciers with nunataks (mountains that poke out of the ice) near Narsarssuaq, southern Greenland. © Richard Burt

The ice in contact with the valley walls contains a lot of rock and sediment Larry which makes the ice dark grey or brown. When several cirque glaciers merge into a single valley or piedmont glacier the ice has a striped appearance.

Stripes of sediment in glacial ice.  The sediment shows where the edges of the individual glaciers used to be. © Abigail Burt

Zones of an alpine glacier:

Diagram of an alpine glacier
Click to view larger and see the legend.

  1. Truncated spur
  2. Arêtes
  3. Horn
  4. Hanging valley
  5. Glacier

Alpine glaciers pluck and grind up rocks creating distinctive U-shaped valleys and sharp mountain peaks and ridges.

Cwm Rhiwarth. U-shaped valley looking south-east from Craig Wen towards Llangynog.


A cirque is a bowl-shaped hollow found high up on the side of a mountain.

A cirque (bowl-shaped hollow) left behind after a cirque glacier melted.  Near Holar, northern Iceland. © Abigail Burt

An arête is a sharp ridge of rock Larry that is left between two adjacent glaciers.

Arêtes (sharp ridges of rock) between U-shaped valleys.  Eyjafjordur, north of Akureyri, Iceland. © Abigail Burt

Truncated (cut off) ridges and hanging valleys form when small valley glaciers merge with a single large valley glacier.

Valley glaciers erode V-shaped stream valleys into much more rounded or U-shaped valleys.

A U-shaped hanging valley in Wales. © Abigail Burt

Sometimes a small lake called a tarn will form at the bottom of the cirque. There are three tarns in a small area of Cumbria, UK, on the geological map Manuel below, they are the black shapes.

Static map.

Image: Loch Brandy, Angus


Horns are steep mountain peaks that form when a mountain has been surrounded by cirque glaciers, such as the Matterhorn in Switzerland.

A horn surrounded by cirque and valley glaciers.  Paradise Bay, Antarctic Peninsula, Antarctica. © Richard Burt

Glaciated valleys that are flooded with sea-water William are called fjords. Some fjords are over 1 km deep.

Looking back to Gudvangen village from Nærøyfjord (narrow fjord), Norway. © Richard Burt

 

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