Glacial Erosional Landforms - Corrie

Aim: To be able to understand glacial erosional landforms

Glaciers create unique landforms in upland areas, just look at some of Scotland’s most beautiful scenes in the clip below near Loch Lomond. Take particular note of the before and after glaciations landscapes.

 Video describing the effects of glaciers on the Loch Lomond area. (Source:The video)

Figure 1: Image illustrating Loch Lomond (Source:Reference)

One example of a glacial landform is a Corrie.

Figure 2: Diagram illustrating the formaton of a Corrie (Source:Reference)

 A corrie is an amphitheatre shaped rock hollow and has a steep back wall with a deepened basin. It is often associated with having a small lake known as a tarn. For example the one seen in the photograph below at Low Water Coniston Old Man in Cumbria. 

Figure 3: Image illustratung a tarn in a corrie in Cumbria (Source: Reference)

Corries in the UK are normally found on north or north east facing slopes due to their isolation allowing more accumulation of snow. If there is more than one corrie lying back to back or alongside each other, a process of enlargement normally occurs. This leaves a narrow, steep sided ridge between too hollows. This is called an Arête (See example below). Examples of Arêtes can be found on Helvellyn in the Lake District – see if you can find out more information about it and provide a case study!

 Figure 4: An example of the formation of an Arete. (Source: Reference)

 

 

When two or more corries develop on a mountain, the central mass will still stand and be known as a pyramidal peak. It normally has a sharp appearance die to frost shattering and an example of one of these is Matterhorn in the Alps (See photo below).

Figure 5: Image illustrating the Matterhorn in the Alps (Source: Reference )

The formation of Corries:

• The original process is named nivation, this acts upon a shallow and Periglacial hollow and enlarges it into an embryo corrie. This can take a low amount of glacial time – so a very very very very long time within an ice age).
• As the hollow grows, more snow is added and the weight causes it to compress and forms firn and eventually ice.
• As time goes on the process of plucking will erode away at the back wall to create a steeper drop and the rotational movement of the ice, in addition to the debris created by plucking erodes away the floor of the hollow.
• This overall will deepen the corrie. As this deepends, the ice at the edge (which is thinner) does not produce the same amount of down cutting and so therefore a rock lip will develop at the boundary. Some of these will have their height increased by morainic deposits formed when the snout of the glacier was in that position.
• Once all of the ice has melted, the corrie fills with meltwater and rainwater to form a small lake, formerly known as a tarn.

CASE STUDY: The perfect corrie to investigate is Helvellyn in the Lake District. Why not try to find out as much information as you can about this corrie to be discussed as a class next time to form a solid case study from all resources.