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Geography Revision…read more

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Ice on the Land
How does Ice Shape the Land?
Glaciers modify and enlarge features that existed before the Ice Age.
The effects are greatest in upland areas where glaciers have been
present for the longest time and where the ice was deeper.
This means rocks being broken down by weather in glaciated
highlands. Freeze-thaw is most important :
· Water fills in a crack in a rock
· The water freezes and the crack is made wider
· The rock breaks into several pieces…read more

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This means rocks being worn away by moving ice. The ice erodes in 2
· Abrasion­ Rocks and rock particles embedded in the bottom of the
glacier wears away the rocks over which the glacier passes. These
sharped edged pieces of rock are used as tools. Smaller rocks have
a sandpaper effect. While sharp edges of the large rocks make deep
grooves called striations.
· Plucking­ This is the tearing away of blocks of rock from the
bedrock as the glacier moves. These rocks had been frozen in the
Valley glaciers are more effective at erosion that ice:
· In the valley, the ice touches both the floor and the sides.
· Valley glaciers flow more quickly , because of the steeper gradients
and more melt water is present to lubricate the flow.
· There is a plentiful supply of rock fragments, so these glaciers are
well supplied with tools for abrasion.…read more

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Landforms of glacial erosion
Ice is an increasingly powerful agent of erosion and it can for spectacular
landforms in mountainous areas.
Corries and Tarns
Corries, also known as cwms or cirques, are often the starting point of a
glacier. Corries are large. Circular rock hollows on the upper slopes of
glaciated valleys characterised by having a steep backwall and a
raised lip ate the front. A corrie may contain a lake called a tarn.…read more

Slide 5

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1) Snow collects on a mountainside and is compressed into ice in a
2) Freeze-thaw weathering affects the back hollow and makes it
3) Blocks of rock are pulled away from the backwall by plucking
4) The glacier uses the loose rocks to scrape out the bottom of the
backwall because of the rational slip movements
5) This results in a deep hollow, with a steep backwall and a rock lip at
the front, where less erosion occurs and some material may be
6) After the ice melts a tarn lake may form.…read more

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Arêtes e.g. Grib Goch, Snowdonia, North Wales
· The sharp, knife-edged ridge at the top of a mountain between two
· In any questions about the formation of an arête, write down the 7
stages in the formation of a corries and then add the following
· As the backwall of the corries are cut back by weathering and
plucking, the ridge between them becomes sharper and narrower
· This ridge is kept sharp by freeze-thaw on the mountain peaks…read more

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