(i) When did the last ice age end? (ii) What is a glacier? (iii) Name two processes of glacial erosion. (iv) How can we tell what direction glaciers travelled? (v) Explain two factors that might cause ice ages to occur.
/ I understand some of the reasons why ice ages may occur. / I can explain the two processes of glacial erosion.
Landforms of glacial erosion Learning Intentions
In this section, you will learn: zz how landforms of glacial erosion are created zz how to identify landforms of glacial erosion.
Cirque Arête
Pyramidal peak U-shaped valley Truncated spur
Ribbon lake
Paternoster lakes Hanging valley Fjord
Landforms created by glacial erosion are mostly found in upland areas. There are many examples of these in the Irish landscape.
Cirques
A cirque is a basin-shaped hollow in a mountain. It looks like an armchair. It has three steep sides and often contains a lake. A cirque was the birthplace of a glacier.
Formation: • A cirque is formed when snow accumulates (builds up) in a hollow high up on a mountain. The snow is compressed to form ice.
• The ice plucks rocks from the sides of the mountain as it begins to move. These rocks make the hollow deeper through the process of abrasion.
• The ice eventually overflows from the hollow and gravity causes the ice to move downhill.
• The ice that is left behind melts and forms a lake in the hollow. This lake is called a tarn.
: Figure 11.4 A cirque with a tarn at Coumshingaun in Co. Waterford
Examples of cirques: There are many examples of cirques in Ireland. Many can be identified by the word coom or coum in their name, for example Coumshingaun in the Comeragh Mountains in Co. Waterford. Another famous cirque which contains a lake is the Devil’s Punchbowl near Killarney in Co. Kerry.
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DID YOU KNOW? Cirques are also known as corries, cooms and coums.
