Geography - The Coastal Zone

grace evans
Mind Map by grace evans, updated more than 1 year ago
grace evans
Created by grace evans about 5 years ago
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Mind Map on Geography - The Coastal Zone, created by grace evans on 04/15/2015.

Resource summary

Geography - The Coastal Zone
1 Waves
1.1 How they are made

Annotations:

  • Waves are caused by the wind dragging on the surface of the water. A number of different factors will influence the size and strength of the waves.  The stronger the wind the bigger the waves will be, this is why in storms the waves can be massive. The longer the wind blows over the water in terms of time and distance will also affect the size and strength of the waves.  The distance of the water is called the fetch.
1.2 Types of waves
1.2.1 Destructive

Annotations:

  • These are created in storm conditions by stronger winds blowing for a long timeThey have a tail-breaker which breaks downwards with great force.Their backwash is stronger than their swash.  They have a short wavelength and tall height. They tend to erode the coast and beaches.
1.2.1.1
1.2.2 Constructive

Annotations:

  • These are created in calm weather are less powerful Their swash is stronger than their backwash.  They have a longer wavelength and low height.  They deposit material and create beaches.
1.2.2.1
2 Processes of Erosion
2.1 Marine (sea based)
2.1.1 Hydraulic Action

Annotations:

  • Waves crash against rocks and compress the air in the cracks.  This puts pressure on the rock.  Repeated compression widens the cracks and makes bits of rock break off.
2.1.2 Attrition

Annotations:

  • Waves cause rocks and boulders on the beach to smash into each other and break into small pieces.  Their edges also get rounded off as they rub together.
2.1.3 Solution

Annotations:

  • Weak carbonic acid in the sea water dissolves rocks such as chalk and limestone in the cliffs
2.1.4 Abrasion

Annotations:

  • Eroded particles in the water scrape and rub against rock, removing small pieces.
2.2 Weathering

Annotations:

  • This is the disintegration or decay of rocks in their original place at/or close to the ground surface usually due to the weather, such as rainfall and changes in temperature.
2.2.1 Biological

Annotations:

  • This involves the actions of flora and fauna.  Plant roots are effective at a growing and expanding in cracks in the rocks.  Rabbits can be effective at burrowing into weak rocks.
2.2.2 Chemical

Annotations:

  • Chemical changes occur when weathering takes place. 
2.2.2.1 Carbonation

Annotations:

  • This is the dissolving of rocks containing calcium carbonate eg chalk and limestone 1) rainwater picks up carbon dioxide from the air 2) rainwater becomes a weak carbonic acid 3) acidic rainwater reacts with the calcium carbonate to form calcium bicarbonate which and then dissolves
2.2.2.2 Solution

Annotations:

  • Rainwater, being slightly acidic, can slowly dissolve certain rocks and minerals.  Those minerals or particles unaffected by chemical weathering are usually left behind in form a fine clay deposit.
2.2.3 Mechanical

Annotations:

  • Also known as physical weathering, this involves the disintegration of rocks without any chemical changes taking place.  It often results in power the angular rock fragments called scree.
2.2.3.1 Freeze-thaw

Annotations:

  • 1) water gets into cracks 2) the water freezes in cold conditions or at night 3) as the water freezes it expands, it then thaws in the morning or when it warms up 4) this cycle repeats, widens the crack and weakens the rock 5) the rock breaks off
2.2.3.2 Exfoliation (onion skinning)

Annotations:

  • The top layer of rock is constantly cooling and heating and hot areas, such as deserts, during the day and night. As it heats it expands and contracts as it cools. This cycle can weaken the rock and lead to the outer layer peeling off.
2.3 Mass Movement
2.3.1 Rock fall

Annotations:

  • Fragments of rock and break away from the cliff face due to freeze thaw weathering
2.3.2 Rock Slide

Annotations:

  • Blocks of rock sliding down the cliff face
2.3.3 Mudflow

Annotations:

  • Saturated soil and weak rock flows down a slope.
2.3.4 Rotational slip

Annotations:

  • Happens most often on the coast eg Holbeck Hall Slump of saturated soil and weak rock along a curved surface
3 Transportation
3.1 Saltation

Annotations:

  • Smaller pebbles bounce along the seabed as they are lifted
3.2 Solution

Annotations:

  • Materials and minerals are dissolved in the water
3.3 Traction

Annotations:

  • Larger pebbles or rocks roll along the sea bed
3.4 Suspension

Annotations:

  • Tiny rocks will stay suspended in the water
3.5 Long shore Drift (LSD)

Annotations:

  • 1) The swash acts in the same direction as the prevailing wind 2) The backwash is at 90 degrees to share due to gravity 3) The process then repeats
4 Deposition

Annotations:

  • Deposition is when material being carried by the sea water dropped on the coast. Coasts are built up when the amount of deposition is greater than the amount of erosion. The amount of material that's deposited on an area of coast is increased when: -There's lot of erosion elsewhere on the coast , so there's lots of material available. -There's a lot of transportation of material into the area. Low energy waves (i.e slow waves) carry material to the coast but they're not strong enough to take a lot of material away - this means there's lots of deposition and very little erosion.
5 Coastal Features
5.1 Erosion
5.1.1 Headlands and Bays

Annotations:

  • A headland is a narrow piece of land that projects from a coastline into the sea as it is made from resistant/hard rock. They are made as when waves hit the shore the erode away the softer rock more quickly than the harder rock leaving bays and headlands
5.1.1.1
5.1.2 Caves, Arches, Stacks and Stumps
5.1.2.1
5.1.3 Wave cut platforms and Cliff Retreat

Annotations:

  • 1) Waves cause most erosion at the foot of a cliff. 2) A wave-cut notch forms, which is enlarged as erosion continues. 3) The rock above the notch becomes unstable and eventually collapses 4) The collapses material is washed away and a new wave cut notch starts to form. 5) Repeated collapsing results in the cliff retreating. A wave-cut platform is the platform that's left behind as the cliff retreats.
5.1.3.1
5.2 Deposition
5.2.1 Beaches

Annotations:

  • Beaches are found on coasts between the high water mark (the highest point on the land the sea level gets to) and the low water mark (the lowest point on the land the sea level gets to) They're formed by constructive waves which deposit material like sand and shingle. Sand and shingle beaches have different characteristics: -Sand beaches are flat and wide - sand particles are small and the weak backwash can move them back down the beach, creating long, gentle slope. - Shingle beaches are steep and narrow - shingle particles are large and the weak backwash can't move them back down the beach. The shingle particles build up and create  steep slide.  
5.2.2 Spits and bars

Annotations:

  • Spits are beaches that stick out to sea - they're joined to the coast at one end. If a spit stretches out and connects two headlands then it is called a bar. If the spit joins an island to the mainland then it is called a tombola.
  • Spit:1) Spits form at sharp bends in the coastline, eg at a river mouth.2) Longshore drift transports sand and shingle past the bend and deposits in the sea.3) Strong winds and waves can curve the end of the spit (forming a recurved end)4) The sheltered area behind the spit it protected from waves - lots  of material accumulates in this area, which means plants can grow there.5) Over time, the sheltered area can become a mud flat or a salt marsh. Bars: 1) A bar is formed when a spit joins two headlands together 2)The bar cuts off the bay between the headlands from the sea 3)This means a lagoon can form behind the bar
6 Effects of rapid coastal erosion
6.1 Impacts on Environment
6.2 Impacts on Humans
6.3 Locations
7 Coastal management strategies
7.1 Soft Engineering
7.1.1 Beach Nourihment

Annotations:

  • Adding sand and shingle to the beach to enlarge it. Locally obtained sediment blends naturally with the exiting beach. Sand is brought to shore using a barge Cost: £3,000 per metre
  • Advantages -Cheap and easy to maintain -Blends with the existing beach -Beaches encourage tourists Disadvantages - Maintenance is constant
7.1.2 Marsh Creation/ Managed retreat

Annotations:

  • Low lying costal areas are left to flood. These salt marches are then effective barriers for the sea
  • Advantages -Cheap compared to repairing damages -Creates wildlife habitats Disadvantages -Land is lost -Farmers or landowners need to be compensated.
7.1.3 Dune regeneration

Annotations:

  • Sand dunes are created or restored by either nourishment or by planting vegetation, eg marram grass, to stabilise the dune. This acts as a barrier/ buffer zone between the land and sea. The area is often fenced off to keep people off the dunes. Cost: £20 per metre
  • Advantages -Very cheap -maintains the natural environment -popular with people and wildlife Disadvantages -Time consuming -People can still damage them despite the fences -Can be damaged by storms
7.2 Hard Engineering
7.2.1 Rock Armour

Annotations:

  • Piles of large boulders dumped at the foot of a cliff The rocks force waves to break thus absorbing the energy and protecting the cliff. Cost: Approx £1,000 - £4,000 per metre
  • Advantages -Reasonably cheap and easy to maintain -Can provide interest to the coast often used for fishing Disadvantages -Rocks are usually from other parts of the coast or abroad which is therefore expensive to transport -They therefore wont fit with the local geology -They can be very obtrusive
7.2.2 Groynes

Annotations:

  • Wood or rock structures built out to sea from the coast They trap sediment moved by LSD, therefore enlarging the beach to make a buffer zone. Cost: £10,000 each (200m intervals)
  • Advantages -Results in a a bigger beach which can encourage tourists. -Useful for fishing -Not too expensive Disadvantages -By stopping LSD, beaches down drift can be lessened so they just move the problem to somewhere else -They look unnatural and unattractive
7.2.3 Sea Wall

Annotations:

  • - Concrete or rock barrier to the sea, placed at the foot of a cliff or at the top of a beach. -Has a curved face to reflect the waves back into the sea, usually 3-5m high. -Cost: un to £6 million per km
  • Advantages -Effective at stopping the sea -Often has a walk way or promenade for people to walk along. Disadvantages -Can be obtrusive and unnatural to look at -Very expensive and has high maintenance costs
8 Coastal ecosystems
9 Rising sea-levels
9.1 Reasons

Annotations:

  • Global sea levels are rising at a rate of about 2mm per year which has amounted to almost 20cm in the past century. Its predicted to rise by another 18 to 59 cm by 2100. The cause of rising sea level is global warming - the rapid rise in global temperature over the last 100 years. Global Warming has 2 effects that cause sea level rise: 1) Melting ice - the melting ice on the land (eg the Antarctic ice sheet) cause water that's stored as ice to return to the oceans. This increases the volume of water in the oceans and causes sea levels to rise. 2) Heating oceans - increased global temperature causes the oceans to get warmer an expand (thermal expansion). This increases the volume of water, causing sea level to rise 
9.2 Impacts
9.2.1 Environmental

Annotations:

  • 1) Ecosystems affected - seawater has a high salt content. Increased salt levels can damage or kill organisms in an ecosystem. 2) Vegetation killed by water - the force of floodwater also uproots trees and plants. Standing floodwater also drowns some trees and plants. 3) Increase erosion - a large volume of fast-moving water can erode lots of material, damaging the environment.
9.2.2 Political

Annotations:

  • 1) The government has to make policies to reduce the impacts of future flooding. They can do things like building more or better flood defences, or they can manage the use of areas that might flooded eg by stopping people living there
9.2.3 Social

Annotations:

  • 1) Deaths - coastal floods have killed thousands of people in the past 2) Water supplies affected - floodwater can pollute drinking water with salt or sewage. 3) Loss of housing - many people are made homeless because of the floods 4) Loss of jobs - coastal industries may be shut down because of damage to equipment and building by floods eg fishing boats can be destroyed.
9.2.4 Economics

Annotations:

  • 1) Loss of tourism - many costal areas are popular tourist destinations. Flooding can cause tourist attractions to close and put people off visiting. 2)Damage repair - repairing flood damage can be extremely expensive. 3) Loss of agricultural land - seawater has a high salt content. Salt reduces soil fertility, so crop production can be affected for years after a flood.
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