erosional glacial landforms formation

information on the formation of several landforms formed by glaciers

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Erosional glacial landforms formation
Cirques
Deep bowl depressions enclosed on 3 sides by steep rock walls called
arêtes.
Source of valley glaciers
Contains a raised lip of moraine on the outlet side.
Form on north and northeast facing sides where snow and ice can accumulate
due to little amounts of insolation.
A periglacial hollow is the original site of snow accumulation- this is
increased by freeze thaw weathering at the edge of the snow patch.
The cirque then erodes by rotational flow which causes erosion by abrasion
(due to bed load from freeze thaw weathering) and plucking (ice sticking to
rocks at the sides and then being pulled of when the glacier moves away).
The weight of the ice melts the base lubricating it and allowing it to
move-increasing erosion.
During interglacial periods the ice melts leaving an armchair like hollow and
a small lake called a tarn which is held back by the cirque lip.
When 2 cirques lie back to back, headwall recession (when the headwall
above the glacier retreats by frost weathering) creates a narrow ridge
called an arête.
If 3 or more arêtes develop the central column is called a pyramidal peak.
Pyramidal peak
These are the central column surrounded by cirques.
They form when more than 3 cirques lie back to back creating several
arêtes, which all meet in the same place.
These ridges are created by headwall recession, when frost weathering
erodes the rock face forming arêtes that can then go on to form pyramidal
peaks.
U shaped valleys
Have steep sides but a flat base.
When a glacier makes its way down a v shaped valley, processes of erosion
like abrasion (due to bed load from freeze thaw weathering) erodes the
base and sides and plucking erodes the sides (when ice sticks to rock and
pulls it away when the glacier moves) carving out a u shaped valley.
Interlocking spurs of a river valley will be erodes by the glacier creating
truncated spurs, causing the high steep sided valley.

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Ribbon lakes
Formed when basal erosion gets deep into the bedrock and reaches the
water table. During interglacial periods the depression will fill with water
to create ribbon lakes.
Hanging valleys
These are left after the edge of valleys created by tributary rivers are
eroded at the end, to form valleys joining high up the steep side of the u
shaped valley.
Waterfalls occur here due to the erosion of their river valley.…read more

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