A presentation about Corries by James Baugh.

2.  At first snow collects in a natural hollow on a
mountain (at a high altitude/above the firn
line).
 Over time this snow is compressed by the pile
up of more snow on top of it. This extra weight
forces air partials out, and thus more
denser, compacted, recrystallised ‘firn’ snow is
created (this snow eventually turns into
ice, which will form part of the glacier.

3.  Although the ice is trapped inside a hollow, the
gravitational potential energy created by it, forces erosion
to occur.
 This erosion (at first) comes in the form of ‘plucking’
(where dense ice picks at the wall behind it). This
wall, known later as the headwall/backwall, forms the
main basis of the corrie.
 Plucking induces abrasion (process where rock gained
from plucking erodes away at bedrock) to occur also.
These collectively widen and increase the volume of the
cirque. These two processes are often given ‘zones’ (i.e.
The ‘zone of plucking/abrasion).
 Weathering, further down the corrie (away from the
plucking ice) happens as well. This is freeze-thaw
weathering – where water seeps into porous rock
formations and sets as ice; this expansion of ice, forces the
rock to break.

4. A bergschrund is normally formed when the
natural rotation of the glacier causes the
The circular erosion
inactive /stationary ice (ice not moving as fast
patterns of the forming
as ice nearer the tip of the glacier) to break
glacier can cause a
from the ‘bulk’.
bergschrund to appear.
A
burgschrund
can reach up
to 100 meters
in depth.

5.  Over quantities of time, the corrie becomes arm chair-shaped.
The cirque (which is actually French for ‘Arena’) normally
gains three obvious sides as well.
 One is the noticeable Backwall and the other two (in this
analogy – the ‘arms’) are steep cliffs. Nonetheless these can
become knife-edged ridges known as arêtes (if two corries
erode towards it)
 However there is a fourth; this is called the rock lip. The rock
lip (easier to see when the glacier has retreated/melted) is
formed when debris/moraine collects at the basin of the
hollow. The glacier flows through here when it is finally
forced out with the aid of gravity.
 Lastly a pyramidal peak can be created if three or more
corries erode towards one another (this occurs when
backwalls are forced to meet, by erosion).

6.  When the ice within a corrie melts a lake, called a tarn lake is often left behind. This
is seasonal and freezes in deep winter. Finally the reason why it is able to form is
because of the rock lip (which was created by moraine and collected debris at the
bottom of the cirque).

7. I showed you this image earlier, now name the parts!
You have 1 minute!
1
2 3
4
7 5
6

8. 1. Steep back wall.
2. Burgschrund.
3. Moraine.
4. Rotation of glacial erosion.
5. Corrie/Cirque lip or Rock lip.
6. Abrasion of bedrock.
7. Plucking of the backwall/ headwall(as ice
forms around rock fragments).
Thank you.