Lornshill Academy. Geography Department Higher Revision Physical Environments - Lithosphere

Transcription

1 Lornshill Academy Geography Department Higher Revision Physical Environments - Lithosphere

2 Physical Environments Lithosphere Formation of erosion and depositional features in coastal landscapes Processes of Erosion Hydraulic Action - the force of waves hitting a cliff (or sea wall) compresses water and air into cracks and joints. This increase in pressure may lead to cracks widening and pieces of rock breaking off. Abrasion- Rock fragments may be picked up by waves and thrown against the rock face of cliffs by subsequent waves. Sometimes the softer strata are abraded more than the harder ones, giving a striped appearance. Abrasion is most effective at the base of cliffs. Attrition- Rock fragments are worn down into smaller and more rounded pieces. Currents and tidal movements cause the fragments to be swirled around and to grind against each other. This type of erosion produces pebble beaches. Corrosion (chemical solution)- Salts and acids in sea water can react with rocks, slowly dissolving them away. Erosional Features Formation of a Stack Erosion by Abrasion is when material carried by the waves scrape against the headland wearing it away. Hydraulic action when waves force air under high pressure into cracks in the coastline. Attrition is when beach material is knocked together reducing its size, this can further add abrasion. A discordant coastline is when there are altering layers of hard and soft rock in contact with the sea; this allows the soft rock to be eroded faster forming a headland. Headlands cause waves to refract around them eroding the headlands from the side. Lines of weakness or faults in the headland can be eroded to form small caves. Blowholes can be formed when air trapped in the cave explodes upwards further eroding a line of weakness. Further erosion can take place to allow the cave to be eroded right through to the other side of the headland forming an arch. A stack is formed when the roof of the arch is no longer able to support itself and collapses. 2 P a g e

3 Formation of a wave cut platform In places where high land reaches the sea, cliffs form. The cliffs are attacked by waves that are constantly crashing against them and eroding them by hydraulic action, corrasion and solution. The waves mostly attack the base of the cliff, to form a wave-cut notch. As the waves continue to pound away at the foot of the cliff, the wave-cut notch becomes wider and deeper. This causes the rock above to crack and weaken. In time, pieces of rock fall off and then the whole cliff above it collapses into the sea. This causes the cliff to retreat further inland. The whole process then starts again. As the cliffs erode back a gently sloping rock surface is left in front of them, called a wave-cut platform 3 P a g e

4 Formation of Headland and Bay Headlands and bays form along coasts that are made of alternative bands of hard (resistant) and soft (less resistant) rocks. The waves erode the softer rocks (clay) more quickly to form bays and the harder rocks (chalk) are eroded more slowly and left jutting into the sea to form headlands. Overtime the bays will become more sheltered and sandy beaches will form. Longshore drift As can be seen in the diagram below, a pebble or sand particle moves from point A to B, carried by the swash up the beach, the angle determined by the wave and wind direction. It is then pulled down the beach from B to C, carried by gravity and the wave's backwash. This process is repeated over and over again and the particle moves along the shoreline - this is called longshore drift. When large numbers of sand particles or pebbles are moved along a coastline in this way, a depositional feature called a spit may form. 4 P a g e

5 How do Sand Spits form? Longshore drift moves large amounts of material along the beach until there is a change in the direction of the coastline. When the coastline veers inland, the sand keeps on moving in the original direction, even though there is not a coastline to follow. The sea has to be relatively shallow and sheltered, allowing the accumulation of sand usually beyond a headland. Sometimes a curve develops in the sand if the on- shore wind changes direction. A salt marsh often develops in the curve, where it is especially sheltered. Spits can become permanent if the prevailing wind picks up sand and blows it inland forming sand dunes. They can be consolidated by vegetation. (Link to Biosphere Unit.) How Do Bars, lagoons and tombolos form? A bar is where a spit grows right across a bay, cutting off the bay from the sea. It usually does this due to the absence of any large river that might wash it away. It can cut off a body of water called a lagoon to the landward side. A lagoon is a body of brackish water- part salty, and part fresh. It often supports specialised plants and animals, and is protected as a nature reserve. If a bar links up with an off-shore island, it creates a tombolo. Sandbar These are deposits of sand, which block the entrance to a bay. They develop as a result of long shore drift (L.D.). This is when a swash hits a beach at an angle; as it goes up the beach it carries sediment with it. It returns down the beach with the sediment, as the backwash due to gravity. This process repeats and so moves sediment along the beach. If there is a bay, the sediment is pushed across by the L.D. to form a beach, which starts to extend across the bay, eventually reaching the other side; forming a barrier across the bay or a bar. The sediment on the bar gets smaller and rounder as it moved, Due to attrition eroding the stones as they bang into each other. Behind the bar water is trapped giving a lagoon, There is much deposition as no flow; giving mud flats. The bar may be broken during stormy weather as waves wash their way through it. 5 P a g e

6 Rural land-use conflicts and their management related to coastal landscapes (Dorset Case Study) Social and Economic Opportunities The Dorset Coast is a huge tourist trap but remember people live and work there. There are many different ways that money is made: Industry Offshore, sand and gravel is taken from the seabed providing employment. Wytch Farm Oilfield is located at the South bank of Poole Harbour. It is the biggest offshore oilfield in West Europe. It produces 65,000 barrels of crude oil a day, 10 million cubic feet of natural gas and 500 tonnes of liquefied petroleum gas. There are three large ports with substantial international trade and five smaller harbours which cater for local fishing and recreational craft. Fishing Fishing provides employment for the local people. It also supports a wide range of service industries which maintain vessels and equipment, providing further jobs. The fishing grounds sustain 600 boats. Tourism The scenery attracts many people who come for recreation or to sightsee. The sightseers are attracted by the distinctive, white chalk cliffs, headlands with their caves/arches/stacks (Old Harry), wide sweeping bays (Lulworth Cove) and long, sandy beaches (Shell Bay). There are lots of opportunities for water sports such as swimming, waterskiing and yachting. Others enjoy long walks along the cliff tops and beaches. Important wildlife refuges are found just behind the coast in the sand dunes (Studland), lagoons and marshes (The Fleet) which encourages visitors. Rare heathland plants and rare British Wildlife such as lizards and snakes can be found. These encourage large numbers of visitors who spend their money in the local area which creates jobs, opportunities for hotels, restaurants and shops. Benefits Tourists Bring They inject money into the local economy by spending money in local shops, hotels etc. They provide jobs (38,000) for the locals and people from further away. Locals are able to set up their own business, become wealthier and in turn spend more money in the local community. This is called the multiplier effect. If there are a lot of tourists, to keep them coming back the council provide better services are such as more public transport, toilets, shopping centres and sports facilities. 6 P a g e

7 Environmental Conflicts Even though tourists bring many benefits they also cause a variety of conflicts. Conflicts occur between the following groups: Tourists Vs Residents The tourists cause a lot of congestion on the roads. The larger settlements of Bournemouth, Poole and Swanage all suffer from congestion. The congestion is caused as 82% of tourists travel by car, they tend to visit at the same time (Bank Holidays and weekends) and often drive slowly to admire views. In addition, they take up most parking spaces, park where they should not and increase local air pollution. The village of Corfe Castle also suffers badly. It is a major tourist attraction and is on the only main road to Swanage. A lot of tourists and 500 heavy lorries pass through every day. The congestion is also caused by narrow streets, street parking and lack of proper car parks. Tourists Vs Tourists Many tourists are attracted to Poole Harbour. Mid summer, there can be 4000 boats in the harbour at any one time (yachts, fishing boats, jet-skiers, water-skiers etc). Around the harbour are sunbathers, birdwatchers, sightseers and walkers. This is a recipe for conflict. The noisy pursuits, eg. power boats upset the people wanting peace and quiet, eg. the fishermen and birdwatchers. Increasingly powerboats are being used in winter, which is when thousands of birds migrate here. Tourists Vs Conservationists Tourist activities in Poole Harbour are polluting the water (oil and litter). Powerboats are scaring migrating birds in winter. At Studland tourists are causing erosion of the sand dunes. Here, the dunes are between the car parks and the beach. People walk through the dunes, trampling on fragile plants (which bind the sand together) until they die. With less vegetation the sand dunes themselves become eroded and wildlife disappears as the habitat changes. Horses also add to the trampling as there is a riding centre nearby. 7 P a g e

8 Measures taken to resolve conflict Organisations such as public/official bodies (County Councils) and voluntary bodies (The National Trust) take steps to sort out problems between the land users. The County Councils (Public Body) To ease traffic congestion in Bournemouth, Poole and Swanage the following solutions have been tried: One way systems. Encouraging other types of transport (by providing bus and cycle lanes). Phasing traffic lights. Restricting the hours of road works. To ease traffic congestion in the Village of Corfe Castle, Dorset County Council have devised several solutions: A railway line has been opened with steam trains running from Swanage to Norden, just north of Corfe Castle. People can now visit these places without driving into or through the Village. An extra car park has been developed in the village. This should reduce the street parking, which should allow traffic to go faster. More cycle ways and summer bus routes have been developed, but a proposed by-pass has been rejected. To try and solve tourist conflicts in Poole Harbour, Poole Council have introduced: Zoning of Poole Harbour (different activities are zoned in different areas so they do not upset one another). Maximum speed limits have been imposed in some parts, which prevents power boating and waterskiing taking place. The National Trust (Voluntary) They have tried to ease conflicts with conservationists by; Lobbying to get certain areas a protected status. RSPB sites have been set up to protect wildlife and SSSI sites to protect vegetation. Educating visitors by taking them on guided tours and providing information on boards and leaflets. Restricting access to sensitive areas. Providing wardens to look after the area. 8 P a g e

9 Effectiveness of Resolutions Without doubt current resolutions are making a difference. However; It is impossible to ensure that everyone adheres to advice, rules, restrictions etc (zoning, parking on yellow lines). It is costly to manage. You are never going to please everyone. Some measures may not be feasible everywhere. In some parts of the Dorset Coast tourism may change the culture. This is difficult if not impossible to prevent Formation of erosion and depositional features in glaciated landscapes Processes of 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. 9 P a g e

10 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 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. 10 P a g e

11 U-shaped valley 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 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 Deposition Terminal Moraine These are deposits of Glacial Till which are angular in shape as there has been no water present to cause attrition, so rocks have not been banging into each other rounding of sharp edges. As there is no water present the sediment has not been sorted and so different shaped stones are all jumbled up together. From the diagram you can see how the deposition is arc shaped across the snout of the glacier and marks the furthest boundary of the glacier. Deposits originate from debris on 11 P a g e

12 valley floors and eroded materials, which are pushed along a U shaped valley floor by an advancing glacier. The ice at the glaciers snout supports the moraine, but when it melts the support is removed and the moraine collapses. A series of these can be left on the land if the glacier goes through several advancements and retreats, reflecting changes in temperature. These are called recessional moraines and can be seen in the diagram above. Water can be trapped behind the terminal moraine when the ice melts, this is an ice dammed loch, which can be replenished by rainwater. Eskers These are Fluvio Glacial deposits meaning they have been deposited with the aid of water as well as ice. With water present stones are moved and bang into each other, this means sharp edges are knocked off and become rounded, a process called attrition. Eskers are long narrow winding ridges, which are the remnants of a river bed which once flowed inside a glacier. Sediment is deposited in the river as usual and are dropped by the glacier as ice melts and collapses due to warmer temperatures. They are found on the same areas where Ground Moraine is found. This is because they develop in the glacier and not beyond it, so can t be found on Outwash Plains which develop beyond the glacier. Deposits are laid down in layers, with smaller deposits forming bands on the river bed when there is less meltwater, due to colder temperatures. When it is warmer there is more meltwater and so the river carries larger rocks depositing them in bands when the flow slows. Stones in the river bed can also be deposited in groups laterally, with the smallest stones been deposited furthest along the river and larger stones further upstream. The larger stones are dropped further upstream as the river only has energy to carry them a short distance, whereas the water has the energy to carry lighter stones further down the river. These 2 ways of organising sediment are collectively called sorting. Blockages occur in the tunnel that the river is in, these are often caused by deposition of sediment due to cooler temperature and less meltwater. When the ice melts dropping the esker on the floor, this build up in the esker appears as a smallish hill in the ridge of the esker called a beaded esker. 12 P a g e

13 Rural land-use conflicts and their management in glaciated landscape (Lake District case study) Social and economic opportunities Agriculture The environment is better suited to hill sheep farming than arable farming due to steep slopes, thin, poor soils and poor weather. On the valley floor and lower slopes some farmers keep beef and dairy cattle and grow grass for making hay and silage. 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 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. Coniferous trees are ideal as they are suited to cold climate and thin, poor soils. More than tonnes of timber are produced every year. Water Storage 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. Haweswater, Thirlmere, Ullswater and Windermere Lakes are used as reservoirs. Industry and Mineral Exploitation 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. 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 The Lake District attracts many tourists as it has spectacular scenery which lends itself to a wide range of activities. 13 P a g e

14 There are 16 major lakes, together with high peaks and valleys. Tourists like the pretty villages and maize of drystone walls. There are lots of opportunities for recreation; water sports, climbing, hill walking, mountain biking and canoeing. 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. Benefits tourist bring to the Lake District Tourists have brought a lot of benefits to the Lake District such as; Money is injected into the local economy. If there are a lot of tourists, to keep them coming back the council provide better services such as more public transport, toilets and sports facilities. Over 20,000 people are employed in tourism. People work in hotels, shops, visitor centres, outdoor centres, restaurants, pubs, camp/caravan sites and cafes. Farmers can supplement their earnings from tourists by renting out their land for camping and caravanning. They can also sell some of their produce like eggs, cheese, milk and lamb. Locals can sell their homes for high prices to people who want to buy a holiday home. Local people can set up their own business like a bed and breakfast, shop or café. Greater prosperity and more employment may help to cut down on rural depopulation. Environmental Conflicts Even though tourists bring many benefits they also cause a variety of conflicts. Tourist Vs Residents Traffic Congestion 14 P a g e

15 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 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 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. 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 Not all tourists obey the country code. Tourists leave field gates open allowing animals to stray onto roads and be killed or cause accidents They drop litter which not only looks unsightly but may be eaten by farm animals, harming them and costing the farmers money They let their dogs off their leads allowing them to chase animals. Also can cause miscarriages during lambing season. Children may play on dangerous farm machinery causing damage and expense to the farmer. Footpath Erosion 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. 15 P a g e

16 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 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 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 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; 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). 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; 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. 16 P a g e

17 There is zoning of tourist activities (swimming areas ect). Speed limits They have tried to ease soaring property prices by; 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; 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; They buy land and buildings and manage them. In this way they can ensure that at least this land is protected. 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. Effectiveness of Resolutions Without doubt current resolutions are making a difference. However; It is impossible to ensure that everyone adheres to advice, rules, restrictions etc (zoning, parking on yellow lines). It is costly to manage. You are never going to please everyone. Some measures may not be feasible everywhere. In some parts of the Lake District tourism may change the culture. This is difficult if not impossible to prevent. 17 P a g e