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Definition
A U-shaped valley is carved out of a V-shaped stream
valley by the movement of a glacier.
A glacier widens, straightens and deepens an
originally sinuous valley.…read more

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Eg. Nant Ffrancon Valley, Snowdonia
Dimensions
·Length: 4km
·Depth: 350m
·Width: 0.5km
Location
·High Relief
Shape
·Steep sides
·Deep, flat
floor…read more

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Formation
Glacial troughs form as a result of the erosive action by a
glacier travelling down a V-shaped valley. The main
processes involved are abrasion and plucking.
Abrasion
The scraping, scouring and grinding action of material
being carried by glaciers.
Plucking
Occurs when the glacier freezes around a rock on a valley
side or bottom, and subsequent movement of the ice causes
the rock to be pulled away with it.
The glacier uses englacial and subglacial debris to carry
out these processes. The main source of this debris derives
from freeze-thaw weathering. These processes allow the
sides and base of the V-shaped valley to become eroded.…read more

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Uneven Valley Floor
The long profile of a glacial trough is frequently irregular.
This is caused by differential erosion which, in turn is
caused by the extending and compressing flow taking place, the
confluence of two glaciers and the weakening of rocks. The
rock is weakened by chemical and freeze-thaw weathering.
Freeze-thaw weathering occurs when water enters a crack and
freezes, when the water freezes it expands up to 9%, this
expansion causes the rock to weaken, and sometimes crack,
making it more likely to be eroded.…read more

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Change in Shape
Glacial troughs often change in shape. This is
mainly due to material being deposited as moraine
or scree.
Scree is a pile of sediment that collect at the
foot of a mountain range. The fragments are often
angular.…read more

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