Geography AQA A

Mechanical Weathering- The breakdown of rock without changing it's chemical composition.

For Example, Freeze Thaw

• Happens when temperature alternates above and below 0 degrees
• Water gets into rock cracks
• When the water freezesit expands- puts pressure on the rock
• When the water thaws it contracts- takes pressure off rock
• This process repeating widen the cracks and causes the rock to break

Chemical Weathering-  The break down of rock by changing it's chemical composition.

For Example, Carbination Weathering

• Rainwater has carbon dioxide dissolved in it, a weak carbonic acid
• Carbonic acid reacts with rock that contains calcium carbonate, so the rocks are dissolved by the rainwater

Waves wear away the coast using four processes of Erosion.

Hydraulic Action-  Waves crash against rock and compresses the air in the cracks. This puts          pressure on the rock. Repeated Compression widens the cracks and bits of rock break off.

Abrasion-  Eroded particlesin the water scrape and rub against rock, removing samll pieces.

Attrition-  Eroded particles in the water smash into each other and break into smaller pieces. They become more rounded.

Solution-  Weak carbonic acid in sea water dissoolves rock like chalk and limestone

Traction-  Large particles like boulders are pushed along the sea bed by the force of the water.

Suspension-  Small particles like silt and clay are carried along in the water.

Saltation-  Pebble sized particles are bounced along the sea bed by the force of the water

Solution-  Soluble material dissolve in the water and are carried along.

Material is transported along coasts by a process called Lonshore Drift:

1) Waves follow the direction of the prevailing (most common) wind.

2) The usually hit the coast at an oblique angle (not a right angle).

3) The swash carries material up the beach, in the same direction as the waves.

4) The backwash then carries material down the beach at right angles, back towards the sea.

5) Over time, material zigzags along the coast.

Beach -  Beaches form in sheltered environments such as bays. When the swash is stronger than the backwash, deposition occurs. Beaches occur when shingles and sand is deposited.

Spit-  Spits form at sahrp bends in the coastlines, for exapmle a river mouth. Longshore drift transports sand and shingle past the bend and deposits in the sea. Strong winds and waves can curve the end of the spit. The sheltered area behind the spit is protected from waves so alot of material accumilates her and plants can grow there. Over time, the sheltered area can become a mud flat or a salt marsh.

 Bar-  Where a spit extends over a bay but there is water behind it. They join one headland to another. It can form over a bay and not a river mouth because the river current would be too strong.

Tombolo- A Spit which develops and joins the headland and an island together.

Location- Eastern side of the UK, south of Scarborough, facing the North Sea

Causes

• Easily eroded rock type, boulder clay
• Frequently attack by destructive waves - driven by strong winds blowing across the North Sea.
• Wave erode the base of the cliffs - hydraulic action and abrasion 
• costal defences called groynes were built at Mappleton in 1991 has accerlerated erosion as parts of beaches are narrow which means they erode quicker

Effects and Impacts

• Homes near the cliffs are at risk of collapsing into the sea
• Property prices aling the coast have fallen sharply - at risk from erosion of cliff
• Accessibility to some settlement has been effected- roads near cliff tops are at risk of erosion
• Businesses are at risk, so people will lose their jobs. E.g.  carvan sites
• Gas terminal at Easington is at risk, accounts for 25% of UK's gas supply
• Large amounts of farm land is being lost each year

Forms of coastal protection could be:

• Building wave-resistant structures along the cliff-base; the main type is sea walls
• Trapping moving beach material by using groynes 

Problems with this:

• Coastal protection is very expensive 
• Cost/Benefit anaylses mean that only the valuable, populated sections of the coast recieve full protection. while remote unpopulated farmland may be left to the 'do nothing ' option.

Shoreline Management Plan (SMP)-  An integrated coastal management plan for a stretch of coastline in England and Wales.

Factors that need to be considered when devising a SMP:

• Not all parts of the coast need protecting
• Cost and maintainence 
• Rate of erosion
• What problems are going to be caused for other parts of the coast
• Amount of tourism
• Value of land- What it is used for
• Aestetically pleasing
• How effective it is
• Population of the area

Hold the Line: Maintain the existing coast by building defences

Advance the Line: Build new defences outwards into the sea

Managed Realignment: Allow the land to flood and construct a new line of defence inland- salt marshes that act as habitats. Flooding is controlled.

No Intervention: Allow Natural processes to shape the coastline

When you abandon existing coastal defnces and allow it to flood to create salt marshes which act as habitat. This flooding is controlled.

Pros:

• Create New habitats for animals
• Low maintainence
• Natural coastal enviroment
• Cheap
• Reduces impact of waves
• Attraction to wildlife enthusiasts

Cons:

• Loss of farming land- needed in future for growing population
• Wastes money- abandoning sea defences they have spent money on
• Salt water makes land infertile
• Destroys habitats
• Damages farmer income

Salt Marshes: areas of periodically flooded low lying costal wetlands, that often develop in the shelter of spits. They begin as an accumulation of mud and silt, it is deposited in this area as there is no movement. They are often rich in plants, birds and animals as it has a range of vegetation and habitats.

Pioneer Specie- Cord Grass: Cord grass is well suited to be a pioneer specie as it is tolerant of slat water and it has long roots which means it prevent it from being swept away. i improves the salt marsh enviroment as it enables other pant species to grow. as the mud rises it less frequently covered in water. The cordgrass roots tangle to trap sediment to stablalise the mud. the decomposing plant matter improve the fertility of the newly forming soil.

Vegetation Succession: New plant species start to colonise the area and gradually a succession of plants develops. These new pants replace cordgrass.

Eviromental Conditions: They change as vegetation succession proceeds. Land bcomes more fertile from decomposing plants. Rainwater washes out salt. flooding reduces due to rising mud levels

Factors that may affect vegetation succession: People actions may affect it. increase in demands for leisure and tourism means more people visit the marshes. People may trample, park on it an pollution may damage the salt marshes.

Location: A small country, mad up of over 1000 islands in the Indian Ocean.

Why?: It is low lying land, the highest point is 2.4 metres above sea levels. President mohamed Nasheed and his cabinet signed a document calling for global cuts in carbon emmissons. he is worried the entire population will be eniromental refugees.

Solutions: Scientists believe the rising sea levels are due to global warming, therefore we need to try and stop this:

• Reduce the use of fossil fuels
• Recycle more
• Reduce caron emmissions

Causes:

• Global Warming 
• Polar ice sheet and mountain glaciers around the world are melting, leading to more water in the sea
• The water in the sea is getting warmer, so it expands

Effects:

• Coral reefs will die as they're bleached and the water will get deeper
• People will be forced to leave their homes. Toal population is 400,000
• The traditional way of life will be lost
• Rising sea levels may put an end to the tourist industry
• The country will eventually disappear