Glaciers gcse geography aqa

Uk’s ice age

• Europe's last ice age peaked 20,000 years ago and ended about 11,500 years ago

• At this time, 30% of the world's land was covered in ice

• Temperatures remained below 0°C all year round in northern regions, particularly Scotland, allowing a 1km thick ice sheet to cover most of the country

• Ireland, Wales, northern England, Scotland, and the midlands were covered in perpetual ice 

• Much of the country was uninhabitable for humans

• Today, much of upland Britain is covered in u-shaped valleys along with steep, eroded mountain peaks

• During the ice age, areas covered in ice were weathered and eroded to create a dramatic mountain scenery

• After the ice age, those areas were exposed as deep valleys with sediment deposits

What is a glacier

• Glaciers are large, slow-moving rivers of ice

• Giant glaciers are called ice sheets

• Glacial ice is formed from layer upon layer of falling snow every year

• It takes 20 to 30 years for the layers to compress and form glacial ice

• Glaciers will grow in size if the temperature stays below 0°C

• Glaciers shape our landscape

Glacial weathering

• Glaciers create distinct landforms through weathering, erosion, transportation and deposition

• Freeze-thaw weathering happens when rocks contain cracks and where temperatures regularly dip below the freezing point

• Any water in the cracks will freeze as the temperature drops, which expands as it freezes, exerting pressure on the crack

• Repeated freezing and thawing of water will eventually break the rock apart

Glacial erosion

• After glaciers break down the rock through freeze-thaw action, erosion continues the process by plucking and abrasion

• Plucking:

  • As a glacier moves through a valley, pressure is exerted on the sides and bottom of the valley

  • This generates friction and heat, causing the edges of the glacier to melt a bit

  • This meltwater freezes around rocks and stones under the glacier

  • As the glacier moves forward, it 'plucks' this ice, pulling the rock away 

• Abrasion:

  • Abrasion occurs as bits of rocks, stones and boulders stuck in the ice grind against the rock below the glacier, wearing it way

• It is the weight of the ice in a glacier which forces it to advance downhill, eroding the landscape as moves

• Ice advances in a circular motion called rotational slip, which hollows and deepens the landscape

Glacial movement & transportation

• Glaciers move under gravity very slowly

• Glaciers transport material such as clay, rock, and sand in the body, base and surface of the glacier over long distances

• The front of a glacier is called the 'snout' and acts as a bulldozer, pushing loose rocks and debris downhill by the sheer force of the moving ice

• Rotational slip is the circular motion of the ice in a hollow 

• Due to the weight of the ice, friction at the base of the glacier melts the ice and the glacier will move on a film of meltwater

• Any material carried or moved by the glacier is called glacial till

Glacial deposition

• During the warmer summer months, glaciers begin to melt, and glacial till is deposited on the valley floor or sides of a moving glacier

• Till is unsorted, irregular debris ranging from clay to boulders of any size and shape 

• Meltwater will also flow out of the glacier's snout, forming meltwater rivers

• These rivers carry large amounts of glacial till, which will undergo further erosion through attrition to become outwash 

• This finer till is sorted and when the energy of the river reduces, the outwash is deposited in layers further down the valley on the outwash plain

Erosional landforms

• As a glacier moves, it erodes everything in its way

• Glacial erosion creates different features as it flows downhill:

  • Pyramidal peak 

  • Arête  

  • Corrie/cwm/cirque

  • Tarn

  • Truncated spur

  • Hanging valley

  • Ribbon lake

  • Glacial trough/U-shaped valley

Pyramidal peak 

• As the name suggests, this is a three-sided, pointed mountain peak

• Formed when three or more back-to-back glaciers carve away at the top of a mountain

• Examples include Snowdon in Wales and Buachaille Etive Mòr, Glencoe, Scotland 

Arête  

• Arêtes are knife-edge, steep-sided ridges

• Formed when two glaciers flow back-to-back

• As each glacier erode either side of the ridge, the edges become steeper and the ridge narrower

• This gives the arête its jagged profile

• Examples include Crib Goch in Wales and Striding Edge in Lake District England

Corrie/cwm/cirque

• Corrie, cwms and cirques are all the same feature and are formed in hollows where snow can accumulate, usually on a north-facing slope

• In Wales, corries are called cwms and in France, they are called cirques 

• Formed when the glacial ice moves through gravity, rotational slip, and sheer mass of the ice

• Ice freezes on the back wall of the hollow and as the ice moves, it plucks the rock out, which steepens the back wall

• Freeze-thaw, plucking and abrasion further erodes the hollow into a rounded, steep-sided 'armchair' shape with a lip at the bottom end

• Examples include Helvellyn Corrie in the Lake District and Cwm Idwal in Snowdonia

Tarn

• Tarn lake or corrie loch is a mountain pool or lake in a corrie after the glacier has melted 

• Because of the corrie lip at the bottom end, the meltwater is held in place and a circular body of water is formed

• Examples include Red Tarn, Helvellyn in the Lake District and Cadair Idris in Snowdonia

Truncated spur

• Truncated spurs are past interlocking spur edges of past river action that have been cut off, forming cliff-like edges on the valley side

• Found between hanging valleys, they are an inverted 'V' shape 

• Formed when past ridges/spurs are cut off by the lower valley glacier as it moves past

• An example is Nant Ffrancon Valley in Snowdonia

Hanging valley

• These are small tributary glaciers found 'hanging' above the main valley floor

• When melting occurs, there are waterfalls onto the valley floor

• An example is Cwm Dyli in Snowdonia

Ribbon lake

• As a glacier flows, it travels over hard and softer rock

• Softer rock is less resistant to erosion, so a glacier will carve a deeper trough over this type of rock

• When the glacier has melted, water collects in these deeper areas

• This creates a long, thin lake called a ribbon lake

• The areas of harder rock left behind are called rock steps

  Examples include Lake Windermere in the Lake District and Llyn Ogwen in Snowdonia

Glacial trough/U-shaped valley

• Glacial troughs are steep-sided valleys with a flat floor 

• They start as V-shaped river valleys but due to the size and weight of the glacial ice, it changes to a U-shape as the glacier erodes the sides and bottom, making the valley deeper and wider

• Examples are found all over the UK, but Nant Ffrancon and Nant Gwynant in Snowdonia are good examples

Moraines

• Unsorted glacial till that is deposited in mounds are called moraines

• There are four types of moraines:

  • Terminal: Material deposited at the snout of the glacier

  • Lateral: Material is deposited along both sides of the glacier

  • Medial: Ridge of deposited material in the middle where two glaciers meet and continue to flow downhill together

  • Ground: Material dragged under the base of the glacier and deposited over a wide area on the valley floor

Drumlins

• Drumlins are elongated, egg-shaped hills and made of glacial till

• They form beneath the glacier when the glacier meets an obstruction and material is deposited as a ground moraine 

• The moraine is then shaped by the moving ice, which follows the direction of the flow of ice

• The largest ones can be over 1 km in length, 0.5km wide and 50m high

• Multiple drumlins are known as swarms or baskets of eggs

• As the material is deposited, it builds up to have a round, blunt and steep front (stoss) end 

• The flow of ice over the top of the drumlin drags the material along and down, creating the lee slope

• The lee is gently sloped, elongated and with a tapered tail 

• Examples include The Drumlin Field below Cam Fell in the Yorkshire Dales and Conway Valley, North Wales

Erratics

• Erratics are random rocks of different sizes and types from the area they are found

• There is no pattern to their deposition, and they look completely out of place on the landscape

• Glaciers pick up large rocks and carry them hundreds, sometimes thousands, of kilometres from where they originate

• Erratics are carried deep in the ice and do not erode the same as rocks at the edges of the glacier

• An example is the Great Stone of Fourstones (Big Stone)' on the moors of Tatham Fells, England

Case study – Lake District, England Background

• Lake District, Cumbria Northwest Over 20,000 years ago, ice covered England, creating numerous glaciated landforms and England's tallest peak, Scafell Pike (978m)

• Helvellyn is 950 metres above sea level and made predominantly of 450-million-year-old igneous rock 

Erosional landforms

• The back wall of Striding Edge forms Red Tarn corrie with Red Tarn Lake at its base

  • Red Tarn is on the eastern side of Helvellyn with a steep back wall, created through freeze-thaw weathering and plucking

•  Ribbon lakes in glacial troughs can be found throughout the Lake District

  • Ullswater lies east of Helvellyn 

  • Coniston Water and the largest lake in the area, Windermere, are south of Helvellyn

  • Derwent, Thirlmere, Crummock and Ennerdale west of Helvellyn 

Depositional landforms

• Fields in Borrowdale use the terminal moraines as boundaries between farm fields

• Swarms of drumlins can be seen west of Helvellyn at Langdale in the central fells

• The Bowder Stone, an erratic estimated to be 2,000 tons, approximately 9 m high and 15m in diameter, can be found at Borrowdale, west of Helvellyn

Economic uses of glaciated areas

• Upland glaciated areas are challenging environments for economic activity

• Any activity needs to deal with low temperatures, heavy rainfall, steep slopes, and thin, infertile soils 

• The most common economic uses are:

  • Forestry

  • Farming

  • Tourism 

  • Quarrying

  • Water supply and energy

• Forestry

  • Evergreen (coniferous) forests are planted in upland areas, as they can deal with this environment

  • New forests can help lessen soil erosion and counter the impact of deforestation elsewhere

  • Trees are felled for timber and provide job opportunities which boost the local economy

• Farming

  • Due to the steep slopes and poor soils, sheep farming is the most common activity in upland areas

  • Certain breeds of cattle can be grazed on the lower valley floor 

  • Crop growing is limited but grass can be grown for hay or silage to feed the animals

• Tourism

  • The dramatic landscapes make glaciated areas attractive to visitors

  • There are a variety of activities for people to do: Skiing, hiking, climbing, mountain biking, etc.

  • Boosts the local economy and provides a variety of jobs (directly and indirectly)

• Quarrying

  • Glacial erosion has exposed valuable sources of stone and minerals in upland areas

  •  Minerals such as lead, copper, graphite, and coal

  • Slate provides building and roofing material for homes and granite can be used as pavement blocks and kitchen countertops

• Water supply and energy

  • The steep slopes and narrow valleys provide a natural environment for generating hydroelectric power (HEP)

  • Glacial water can be collected and stored in a dam

  • Dams can store drinking water, which can be piped elsewhere for use

  • Naturally occurring ribbon lakes can be used instead of building a reservoir 

Conflict between development & conservation

• Conflicts of interest develop when activities interfere with each other

• Conservationists want to keep the environmental value of the landscape, but development provides employment, roads, and facilities (locally and for visitors)

• Conflict arises between the need for conservation and development

• Forestry

  • Felling trees remove habitats for animals and plants and make access difficult for visitors

  • Coniferous forests do not support biodiversity and limits species numbers, making them less attractive to visitors

  • Coniferous forests are relatively quick to grow and can be harvested more often

• Farming

  • Vegetation protects the landscape from erosion and provides habitats for wildlife

  • Farming harms the environment when clearing trees and vegetation to provide grazing

  • Too many animals lead to overgrazing, which causes soil erosion, which may squeeze out wildlife and pollute water sources

  • Many hill farmers are finding it less economically viable to continue this way of life and are selling land for housing and holiday homes

• Tourism 

  • Some visitors think they can walk anywhere in a National Park 

  • Some walkers do not have control over their dogs, and farmers have found their sheep chased, lambs killed, and gates left open for animals to wander onto the road

  • Visitors tend to focus on a few villages, filling up car-parks, parking on grass verges and blocking entrances to driveways and causing congestion which annoys local residents who cannot get around easily

  • Roads through some areas are narrow, steep and winding, making them unsuitable for coaches and large volumes of traffic 

  • Footpaths become eroded and scarred by wear and tear, making them difficult to walk on

  • Footpath erosion can lead to habitat loss and damage to the historical, archaeological and natural history of the area

• Quarrying

  • Blasting for sandstone, granite and slate releases large amounts of dust, which is a problem for asthma sufferers and pollutes water supplies

  • Noise pollution from blasting disturbs wildlife, tourists and local people

  • Heavy transport lorries cause congestion on narrow roads and increase the likelihood of accidents

  • Heavy lorries cause costly repairs to roads to be made

  • Destroys habitats and disturbs local wildlife

  • Leaves an ugly scar on the land when abandoned 

  • Tourists may find a quarry an eyesore, which could discourage them from visiting 

  • This will have an economic and social impact on the local economy

• Water supply and energy

  • Flooding valleys destroy land and habitats

  • Falling water will generate electricity through hydroelectric power, which is sustainable, plus it does not produce greenhouse gases

  • However, others consider that the natural environment should be preserved, not used for generating electricity

  • Villages have been flooded to build reservoirs, and the water then piped out to large cities

  • This causes conflict during droughts when local people cannot access water