Glaciated Landscapes: Glacial Erosional Landform Formations Flashcards
How does a corrie start forming?
Nivation on a small hollow, where the glacier mass budget is positive and snow is accumulating year on year
How does a corrie continue forming?
Snow buildup becomes glacial ice, which then has a rotational movement due to its weight, which enlarges the hollow. This causes plucking on the back wall, and freeze thaw occurs in the basin
How does material get under the glacial ice during corrie formation?
Frost shattering occurs above the glacier, which then falls into the Bergschrund crevasse, a crevasse formed between the ice and back wall when the ice slides forwards. This material then abrades the base of the corrie
How does a corrie finish forming?
When the hollow becomes too deep, the ice is unable to erode as quickly, which leaves a higher lip of the corrie
How does a corrie lip form if the glacial ice melts before the lip forms?
Moraine is deposited by the melting ice when it moves out of the corrie or melts
How is a tarn (corrie lake) formed?
When the Corrie becomes full of water due to meltwater or rainfall
How are arêtes formed?
When two corries become increasingly steepened and retreat into eachother
How is a pyramidal peak formed?
When three of more corries retreat and steepen into eachother, the resulting peak becomes steeper
How is a trough/u-shaped valley formed?
When glaciers flow down existing river valleys due to gravity, which deepens, widens, and straightens the valley
Why are troughs typically more parabolic than u-shaped?
As weathering causes mass movement of rock, which accumulates as scree slopes which reduces the angle of the slopes
How are rock steps formed?
When valley floor material alternates between a stronger rock and a weaker rock, the weaker rock is eroded more, forming steps in the long profile of the valley
How are rock basins formed?
When valley floor material alternates between a stronger rock and a weaker rock, the weaker rock is eroded more, forming a basin between the stronger rock bands
How are striations formed?
When subglacial debris abrades a rock face, leaving small scratches and grooves
How are Roche moutonnées formed?
Mounds of resistant rock on the valley floor causes the glacier to slide over, helped by localised pressure melting due to the compaction of the ice
Why is the up-valley side of a Roche moutonnée smooth?
As localised pressure melting due to increased compaction and pressure smoothes the rock, and is streamlined by abrasion
