Geography: Glaciation

Glaciation

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  • Created on: 20-04-11 10:06

Processes of glacial erosion, freeze thaw weatheri

Plucking - As the sides of the glacier pushes against the edge of the rock it melts - water goes into cracks in rocks and refreezes - as glacier continues to move pulls rock away

Abrasion - Rock that has been removed by plucking and freeze thaw weathering  carried by glacier - as move down valley erode valley sides and bottom causing more rock to be broken off

Freeze thaw weathering is when ice melts and goes into cracks in rock - then expands up to 9% when freezes at night - process repeats as more water can come in and then freezes again - repeated cycle causes rock to break off - used by glacier to help in erosion or deposited as morraine

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Landforms of glaciated erosion - corries and ribbo

Corries – arm chair shaped hollows, steep rocky back wall, often up to 200m high in UK higher in the Alps. Snow accumulates compacted into ice. After time it moves due to gravity, as it moves it carves out a corrie usually in an area that already had a small depression. Ice erodes by plucking and forms a steep back wall. Hollow is formed by abrasion. After glaciation could be filled by water making tarn. Less pressure at front so erosion is slower. Rock lip forms works as a dam after glaciation.

Freeze thaw weathering occurs at the top of the wall and adds rocks to the ice. Then used in abrasion.  

Ribbon lakes – narrow lakes can be left in valley after glaciation. Formed when glacier meets a band of softer rock can erode more quickly. Groove left in valley bottom after glaciation filled with water e.g. Wastwater.

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Aretes/pyramidal peaks U-shaped valleys truncated

Arêtes and pyramidal peaks – two corries form next to each other, land in between sharp ridge, and if on at least 3 sides of a mountain pyramidal peak.

U-shaped valleys and truncated spurs – U shaped valley formed by valley glacier. Completely fill a valley in upland area, more power to erode than a river. It erodes rock in its path simply removes harder outcrops of rock. Interlocking spurs are cut back to produce truncated spurs.

Hanging valley – main valley glacier very powerful due to amount of ice being moved and pressure it exerts on the sides and bottom of the valley. Other valleys which contained tributary streams smaller not as much ice. Do not cut down as much as main valley. Streams that flow in them now end in waterfall to the main valley.

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Processes of deposition -

Processes - ablation and lodgement – glacial material deposited directly by a glacier can be classified as either lodgement of ablation till.

Lodgement till is where material beneath the glacier has become lodged in the bed e.g. glacier so full of debris it spreads on the valley floor and increase in ice thickness can also increase friction.

Ablation till material deposited as ice melts away solar radiation causes melting on edge of glacier changing seasons.

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Landforms created by glacial deposition

Landforms - Moraines – material deposited by glacier 4 types ground –carried in glacier deposited on valley floor lateral – forms on edge of glacier freeze thaw weathering falls on ice surface medial two lateral moraines join together terminal – end of the glacier.

Drumlins – moraine material deposited by ice sheets in lowland areas elongated features kilometre or more in length 500m width 50m high. One end quite steep other tapers away to ground level. Stoss end steeper end. Ice collected too much sediment couldn’t transport it material deposited

Erratics – large boulders been transported by glaciers.

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Use of glaciated landscapes - water

Glaciers provide water for drinking and irrigating crops:

People in Peru/Bolivia rely on water from melting glaciers in dry spells – global warming means more melt but may retreat causing loss of water altogether.

India, Afghanistan, Pakistan – rely for drinking and irrigation in dry season, monsoon not reliable or plentiful enough for whole year.

Switzerland’s Rhone Valley channelled melt water from glaciers to fields for irrigation, Rhine and Rhone rivers start as melt water

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HEP, Leisure/tourism, Agriculture and communicatio

Glaciers can generate water used for hydroelectric power:

Countries such as Norway and France channelling glacial water through hydroelectric turbines. Norway 99% of energy produced by HEP.

Glaciated areas are used for leisure and tourism:

European Alps for e.g. glaciers attract tourists used by ice climbers and hikers and sightseeing. Landscapers used for walkers climber mountain biking. In Snowdonia 5000 people employed in tourism £180 million made

Agriculture - Hill sheep farming in high areas. Lowland glacial deposits very good for agriculture temperatures better and fertile soil.

Communication routes e.g. roads follow valley floors.

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Avalanches - causes

Storm in Atlantic causing extra snow 4m

High winds for 3 weeks of up to 100km/h move the snow accumulating it in one place

Melt crust mean that more snow accumulated than normal before it gave way

Not sufficient protection as was not thought necessary in the Wasser-Leiter area

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Effects

People - 31 people died 26 of which were tourists with 11 severely injured 30,000 people evacuated

Economical - Roads did not open until 27th Feb

Cancelled tourist bookings and closed ski resorts Paznaun valley lost £5 million a day

Property - 4 local houses completely destroyed and 12 buildings severely damaged

40 buildings buried

100 cars destroyed

£7.5 million damage property

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