Download Glaciation - Lornshill Academy

Lornshill Academy
Geography Department
National Revision
Physical Environments – Glaciation
National 5 Physical Environments
Glaciated Uplands (The Lake District)
Glaciation is the way in which glaciers shape and change the landscape. A glacier is a huge ‘river’
of ice which flows from mountain areas, through valleys, to the lowland areas.
How are glaciers formed?
Glaciers form in areas of permanent snow called snowfields. These occur at high altitudes,
latitudes nearer the poles and often on the colder, north-facing slopes.
 As more snow falls the pressure makes the earlier snowflakes melt.
 More and more snow falls and compacts the layers underneath into glacial ice.
 It can take 30 to 40 years for snow to form dense glacial ice.
 It now moves down slope due the weight of the glacier and gravity.
How do Glaciers change the landscape?
The land is broken down by weathering and worn away by erosion
Freeze Thaw Weathering - Water from melted snow collects in cracks in rocks above
glaciers. At night temperatures drop below freezing and the water changes into ice. Water
expands when frozen and so puts pressure on the sides of the crack. The ice then melts in
the day, releasing the pressure on the sides. This process will happen over and over until it
eventually the rock shatters. Sharp, angular pieces of rock are formed called scree.
Abrasion - This is when pieces of rock carried by the ice score and scrape the rock surface
beneath as the glacier moves. The rock is scratched, polished, smoothed and eventually worn
away by abrasion. The pieces of rock also become smaller through this rubbing action.
Plucking - This is when ice at the bottom of the glacier freezes onto the rock beneath.
When the glacier moves it ‘plucks’ out pieces of rock.
Erosional Features
Formation of a Corrie
They develop as small hollows on the mountainside, which
start to fill with water/snow, which stays all year round due
to cooler/warmer temperatures. The best examples are
found on North facing hillsides as they are shaded from the
sun and being higher up the temperature is cooler. The
hollow shape also protects the snow from the sun.
Over many years the snow is compacted into ice due to
continuous freeze-thawing of the snow and because the
weight of the snow layers eventually squeezes it into ice, the pressure of which helps the
freeze-thaw processing of the snow pack.
The back wall of the hollow is exposed to freeze-thaw weathering, which breaks up the rock
and begins to enlarge/reduce the hollow into a corrie. During the summer the rock from
freeze-thaw is washed under the ice to the back of the hollow.
The build up of ice in the hollow eventually is so great that starts to move it out of the
hollow, a result of its weight overcoming gravity. As it moves it starts to erode the hollow
into a larger feature called a corrie.
The back wall of the corrie is steepened by freeze-thaw weathering and plucking. Freezethaw is when water gets into cracks in the rock and then freezes, as its volume is greater
than water it pushes the crack further apart and repeated over time cause the rock to
break up. The water can be from summer melting or from the great pressure the bottom
layer of ice is put under. Plucking is when water gets into cracks and then freezes, the ice
then sticks the rock and the glacier together so that when it moves it plucks the rock out.
The base of the corrie is scoured out by abrasion, making it deeper. As the ice moves it
drags along rock debris from the land surface. As the glacier moves, it grinds down the land
surface a result of rocks stuck in it scraping the land. As the ice moves it does so in a
rotational way. As it starts to rotate upwards it exerts less erosive pressure and so the
base develops a higher lip of land. When the ice melts a tarn is formed in the hollow from
melt water collecting here.
Arête
 An arête is created when two corries form back to back.
 As they erode towards one another the rock between them is plucked to form a steep
and narrow knife-edged ridge.
 Freeze-thaw action on the exposed surfaces causes them to have jagged and angular
surfaces.
Pyramidal Peak
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A pyramidal peak is created when three or more corries form back to back.
The exposed rock is eroded by plucking and freeze-thaw to form a sharp, jagged and
angular peak in a triangular or pyramidal shape.
U-shaped valley
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A glacier flows down an old V-shaped valley, as the glacier flows;
it erodes the sides and bottom of the valley through plucking and abrasion.
Glaciers have much greater erosive force so bulldoze their way down river valleys,
eroding the interlocking spurs to form cut-off truncated spurs which form the steep
sides of the U-shape valley.
The valley becomes U-shaped, with very steep sides and a flat valley floor
After the ice has melted away completely, rivers again flow through many U-shaped
valleys. These rivers are far too small to have eroded the valley they flow through and
are therefore known as misfit streams.
Ribbon Lake
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Forms on the floor of a u-shaped valley
Where there is an area of after rock the ice erodes more deeply
This creates a natural basin which fills with water
Terminal moraine deposited by the glacier can act as a natural dam
Glacial Map Work
When looking at any question linked
to an OS map, it is important for you
to try to visualise the landscape,
almost turning the flat map into a 3D
landscape (as shown to the left) if
you can do this, it will be a lot easier
to spot where all the features are.
When looking at the contour lines, pay
close attention to how close they are
together, the closer the steeper the
land! Also, look for the height of the
contours somewhere along the
contour line to work if the slope is
rising or falling.
Spotting Glaciated Features
Corrie: Look out for horseshoe shaped
contour lines on the map (to remind
yourself, look at the back of your thumb!)
They might have a corrie lake or tarn in
them (but not always) and may be named as
a ‘corrie’ or ‘cwm’.
Arête: Contour lines will be closely packed
together either side of the arête, as the
sides of arêtes are steep. The top surfaces
of arêtes are often rocky; therefore, you
may also find that the symbol to show loose
bare rocks may follow the top surface of the
arête.
Pyramidal Peak: Pyramidal peaks have a
sharp summit and steep slopes on at least
three sides. A pyramidal peak may form
where three or more corries erode back so
far that they produce arêtes with a
pyramidal peak in between. They can often
be seen as triangular on the map with a
point summit.
U-Shaped Valleys: U-shaped valleys have
steep sides and a wide, flat floor. They are
usually straight and deep. The valley sides
will have closely packed contour lines, to
show the steep valley sides, the valley floor
in contrast will have very few contours, as
it is wide and flat.
Misfit Stream/Ribbon Lake: A ribbon lake is a
large, narrow lake occupying a u-shaped valley. It
forms in a hollow when a glacier has more deeply
eroded less resistant rock or it may fill up a valley
behind a wall of moraine across the valley. Misfit
streams meander through the flat, wide U-shaped
floor. They did not erode the valley, as they
formed in the valley after Glaciation has carved out
the U-shaped valley.
Hanging Valley/Truncated Spur: A hanging
valley is a smaller side valley left 'hanging'
above the main u-shaped valley, the contour
lines will look like a normal u-shaped valley,
but the contours will suddenly stop and will
be cut by the steep sides of the main valley.
Truncated spurs often have almost right
angled contours lines, by the hanging valleys.
(Lake District case study)
Land Uses
Agriculture
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The environment is better suited to hill sheep farming than arable farming due to
steep slopes, thin, poor soils and poor weather.
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On the valley floor and lower slopes some farmers keep beef and dairy cattle and grow
grass for making hay and silage.
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To make extra money farmers rent out fields for caravan/camping sites and turn their
farmhouse into a B&B or offer hunting and fishing.
Forestry
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Land in the lowlands is too valuable to be used for forestry. In the Lake District large
plantations of coniferous trees are common because the land is poor and difficult to
build on. Forestry is as profitable and worthwhile as any other activity.
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Coniferous trees are ideal as they are suited to cold climate and thin, poor soils.
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More than 75000 tonnes of timber are produced every year.
Water Storage
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There are not very many job opportunities in the Lake District but it supplies drinking
water to Manchester 150km away, as it is cheaper than constructing a reservoir
nearby and there is plenty of water.
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Haweswater, Thirlmere, Ullswater and Windermere Lakes are used as reservoirs.
Industry and Mineral Exploitation
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Very few factories and offices are attracted to the Lake District as they cannot be
close to their market, roads are narrow and slow, few people live there and there is a
shortage of flat land for building.
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Extractive industry is important. Slate, granite and limestone quarries provide
employment. The slate is used on the roofs of buildings all over the world. Granite is
used for making roads and limestone for making steel.
Tourism
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The Lake District attracts many tourists as it has spectacular scenery which lends
itself to a wide range of activities.
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There are 16 major lakes, together with high peaks and valleys.
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Tourists like the pretty villages and maize of drystone walls.
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There are lots of opportunities for recreation; water sports, climbing, hill walking,
mountain biking and canoeing.
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Due to the tourists, new visitor attractions (‘Beatrix Potter Exhibition’ in Bowness)
have been set up, hotels, restaurants and shops appeared/improved. This has provided
employment and made locals wealthier. Some locals have managed to set up their own
businesses. Services (buses) and facilities (toilets) have improved. Property prices
have increased.
Environmental Conflicts
Even though tourists bring many benefits they also cause a variety of conflicts:
Tourist Vs Residents
Traffic Congestion
o The tourists cause a lot of traffic congestion on the roads due to a lot of slow moving
cars, buses and caravans. Traffic congestion is at its worst in ‘honey pots’ such as
Bowness and Keswick. This frustrates the local people who are trying to get to places
quickly. The traffic can delay emergency vehicles such as ambulances and fire engines.
Tourists take up most parking spaces, park where they should not and increase local
air pollution.
Few Grocery Shops
o A lot of popular ‘honey pot’ villages such as Grasmere have been taken over by tourist
shops selling outdoor equipment, antiques and gifts. Out of 24 shops only 1 sells
essentials such as bread and milk at expensive prices. This annoys the local people as
they are forced to travel many miles to a supermarket if they want a variety of goods
at a cheaper price.
Raising houses prices and ‘Ghost Towns’
o Some locals cannot afford to move home. Affluent tourists are paying over the odds
to buy a holiday home, out pricing the locals. Some locals are beginning to move out of
the Lake District. 1 in 6 homes are now holiday homes.
o Some villages are becoming ‘ghost villages’ as most of the houses are owned by tourists
who do not live there all of the time. Due to this village shops and schools are closing.
Tourist Vs Farmers
Damage to farms
o Not all tourists obey the country code. Tourists leave field gates open allowing
animals to stray onto roads and be killed or cause accidents
o They drop litter which not only looks unsightly but may be eaten by farm animals,
harming them and costing the farmers money
o They let their dogs off their leads allowing them to chase animals. Also can cause
miscarriages during lambing season.
o Children may play on dangerous farm machinery causing damage and expense to the
farmer.
Footpath Erosion
o Tourist cause footpath erosion. This happens when a lot of people walk up a hill in the
same direction. Overtime the vegetation gets trampled on and killed leaving a path of
bare soil.
o During heavy rain the path will become very muddy and some of it will be washed away.
To avoid the mud people walk on the grass next to it eventually killing it, making the
path bigger. Large paths are an eye-sore and can be seen many miles away.
Tourist Vs Tourists
Recreational Activities
o Honey pots in the Lake District also include Lakes such as Windermere. They offer
many opportunities for recreation and leisure. Some people want to use their motor
boats, water ski while others want to sunbath, bird watch, fish or enjoy the views
around the lake. This creates conflicts. The noisy activities, e.g.. Motor boats upset
the people wanting peace and quiet e.g. the fishermen and birdwatchers.
Tourists Vs Conservationists
Damage to the landscape
o Conservationists are concerned about the look if tourist developments such as visitor
centres as they do not blend in with the landscape and spoil the view.
Measures taken to resolve the conflict (Solutions)
Organisations such as public/official bodies (The National Park Authority) and voluntary
bodies (The National Trust) take steps to sort out problems between the land users.
National Park Authority
They have tried to ease traffic congestion by:
o Bringing in one-way systems (Ambleside). Pedestrianising some streets (Keswick).
Painting double yellow lines to prevent street parking (Grasmere). Providing large car
parks on edge of villages (Grasmere).
o Separating local and tourist traffic. Taking pressure off ‘honeypots’ by advertising
and signposting other attractions in different areas. Encouraging the use of minibuses
and bicycles.
They have tried to ease conflicts between tourists by;
o They are attempting to educate tourists at information centres about enjoying
themselves without causing conflict. Park Rangers are employed to prevent, spot and
sort out problems.
o There is zoning of tourist activities (swimming areas ect).
o Speed limits
They have tried to ease soaring property prices by;
o To reduce soaring property prices and locals being forced out by tourists, the
Authority can insist that new houses are sold/rented cheaply to locals (Rosthwaite and
Bowness).
They have tried to ease conflicts with conservationists by;
o They vet plans for new tourist developments. Plans that may cause conflict are
rejected. They insist that new buildings, visitor centres, car parks are screened by
deciduous trees and that local stone is used in construction.
The National Trust
To ease conflicts the tourists cause to conservationists and farmers;
o They buy land and buildings and manage them. In this way they can ensure that at
least this land is protected.
o They reduce footpath erosion caused by hill walkers by laying blocks of hard wearing
stone ‘stonepitching’ to provide a good walking surface, fence off worse affected
areas to allow them to recover and dig drainage channels to stop water running down
footpaths.