Leaving Certificate Physical Geography
Q:
2013 Q2(B)
Explain with the aid of a labelled diagram(s) the formation of one
Irish landform of erosion you have studied. (30 marks)
One feature of glacial erosion is a corrie. It is a hollow high up in the mountains that
was eroded by a large glacier during the Ice Age in Ireland.
The processes freeze-thaw action, plucking, abrasion and rotational slip all
combined to form a corrie or cirque. An example of an Irish corrie is "The Devil's
Punchbowl" in county Kerry.
Freeze-thaw action is a mechanical weathering process. Water fills little cracks in
the mountain rock and freezes. When water expands, the pressure is too much for
the rock and so it weakens and crumbles away. Gravity causes this on the upslope
side of the mountain and forms a crevasse.
Plucking is when the glacier sucks and plucks up rocks and boulders from the
ground as it passes over them. This process deepens the hollow, forming rock
basins over time. These basins have three steep sides and are more common in
north-facing slopes. This is because the sun melts snow quicker on south-facing
sides.
Abrasion is the process whereby the glacier uses the rocks and boulders that it
plucked up to abrade or scratch the land. These rocks that are stuck to the glacier
leave permanent marks on the land.
Rotational slip is the process where the ice in the hollow is so heavy that gravity
makes it slide in a curved motion. This movement makes a deep hollow or corrie in
the mountain side. Nivation is the term used to describe the combining of the
processes to erode a corrie in the mountain. Sometimes a small lake forms in the
corrie called a tarn.
Labelled diagram: