edexcel geography b-coasts
Terms in this set (61)
when pebbles and rocks are smashed into each other in transport
when water is thrown at the coast,water is pushed inside the cracks
when pebbles are thrown at the coast,eroding other material
product of weathering and erosion
large boulders too heavy to be carried are rolled along the seabed by waves. these are the first to be deposited
smaller,lighter, boulders are bounced along the seabed by waves,causing abrasion of the sea bed
sand grains are carried in the waves. these are the first to be picked up and last deposited due to the low wave energy required
calcium from limestone and chalk rocks are dissolved and carried in the waves. Almost no energy required to transport
caused by the repeated freezing and thawing of water in a crack or hole in the rock. when water freezes,it expands by about 10% causing stresses within the rock. when the ice melts,water seeps deeper into the rock along the deepened crack. after repeated cycles of freezing and thawing,fragments of rock may break off
rainwater is slightly acidic. when rain falls on rocks such as limestone and chalk a weak chemical reaction takes place,causing the rock to weaken and break down
the roots of growing plants can widen cracks in rocks. burrowing animals and nesting birds on cliff faces can also cause the rock to weaken and decay
these happens suddenly when pieces of rock from a weathered cliff fall. this often occurs as the rock at the base of the cliff has been undercut by the action of the waves, leaving the rock above unsupported and causing it to collapse
this is similar to slumping but the movement of material occurs along a flat surface,usually a bedding plane. large amounts of soil and rock move downslope rapidly
this often occurs after long periods of rainfall. the rain seeps through the soil and permeable rocks such as sandstone. at the junction where the permeable rock meets an impermeable rock such as clay,the saturated rock slumps and slips, often in a rotational manner along a curved surface
the prevailing wind is the direction the wind normally blows from. in the UK, the prevailing winds are from the south-west. some parts of the coastline are protected by the land so the prevailing wind comes from a different direction.
-for examples,along the coast of southern england,prevailing winds are from the south-west, whereas along the east coast, they are from the north. During the winters months,low-pressure weather systems over the atlantic oceans create winds in excess of 150 km per hour and cause high-energy destructive waves to form. this results in greater rates of coastal erosion in the winter than the summer
the climate of an area will affect the type of weathering that operates on a slope and will govern the rate of erosion and mass movement. For example,have rain will add volume and weight to the soil,making mechanical and chemical weathering, and therefore slumping,more likely along certain parts of the coastline
the downhill movement of material (rocks,soil,mud) under the influence of gravity
-different types of mass movement depend on: the material involved,amount of water in the material and the nature of the movement
a rapid movement which occurs after periods of heavy rainfall,on steep slopes
-when there is not enough vegetation to hold the soil in place, saturated soil flows over impermeable and moves downslope
a slow movement,occurring on a gentle slope
-when wet,soil particles expand and get heavier. when the soil dries out,it contracts vertically. as a result, the soil slowly moves downslope
> Constructive waves deposit the load carried by waves.
> Sheltered spots (e.g. bays).
> Calm conditions with little wind, so the waves can lose their energy eventually.
> A gentle gradient offshore causing friction.
-coasts in which bands of rock run parallel to the coastline
-characterised by coves and mostly straight coastlines
-same type of rock along its length
coasts in which bands of rock run perpendicular to the coastline
-characterised by headlands and bays due to different rates of erosion
-different types of rock along its length
formation of coves
Lulworth Cove, Dorset
- The entrance to the cove is narrow where the waves have cut through weaknesses (joints/faults) in the resistant limestone.
- Then the cove widens where the softer clays have been more easily eroded.
-At the back of the cove is a band of more resistant chalk, so erosion is slower here.
formation of headlands and bays
-headlands and bays are formed when the sea erodes a discordant coast with alternating bands of hard and soft rock
-the bands of soft rock erode quicker than those of harder, more resistant rock
-this leaves a section of land jutting out into the sea called a headland. the areas where the soft rock has rapidly eroded, next to the headland, are called bays
-when formed, bays are sheltered by headlands, so are eroded less
-when formed, headlands are more vulnerable to erosion as wave energy is concentrated there
wave cut notches
formed at the base of a cliff when the sea attacks a line of weakness in rock, opening up a crack or joint
wave cut platforms
formed when a wave cut notch causes a cliff to collapse. wave cut platforms are left behind as the cliff has retreated in land
formed when a wave forces its way into cracks in the cliff face. hydraulic action occurs until the cracks become a cave
formed when a cave breaks through the other side of a headland, forming an arch
formed when an unstable arch collapses under its own weight, leaving a headland on one side and an arch on the other
formed when a stack is attacked (hydraulic action). this weakens the stack until it collapses and forms a stump
impacts of UK climate on coastal erosion
- The UK winter climate frequently sees temperatures dipping below 0ºC at night and rising above 0ºC in the daytime, leading to freeze-thaw weathering.
-Prevailing winds are from the south-west, bringing warm, moist air from the Atlantic, leading to frequent rainfall. This leads to weathering and mass movement on the coast.
- Storm frequency is high in the UK, bringing heavy rainfall, leading to mass movement. Storms also increase wind power, leading to an increase in the eroding power of destructive waves.
the break down of rocks in-situ
-affects slopes by causing rocks or fragments of rocks to move downslope
types of transport
conditions for deposition
-constructive waves deposit the load carried by waves
-sheltered spots (e.g. bays)
-calm conditions with little wind,so the waves can lose their energy eventually
-a gentle gradient offshore causing friction
-Longshore drift involves transporting eroded material along the coast and depositing it when waves lose their energy.
1. Waves approach the coast at an angle due to the prevailing wind.
2. Swash moves sediment up the beach at the same angle.
3. Backwash carries sediment back down the beach at 90º to the coastline due to the force of gravity.
4. This repeats until the waves lose their energy, at which point the sediment is deposited.
-Destructive waves have more energy so can transport material for a longer amount of time.
formation of beaches
-beaches are accumulations of sand and shingle,formed by deposition,and shaped by erosion,transpiration and deposition
-beaches can be straight or curved.
-curved beaches are formed by waves refracting as they enter a bay
formation of spits
spits are a depositional landscape formed by longshore drift, an example is Spurn Head on the Holderness coast
1-Longshore drift deposits sediment along the coast.
2- Spits are formed when the sediment is deposited in shallow, calm water when there is a change in direction of the coastline.
3-As the spit grows outwards, a change in wind direction results in the spit forming a curved end (hooks or recurved laterals)
4- A salt marsh may form in the sheltered, low energy zone behind
formation of tombolos
formed when a spit continues to grow until it reaches an island, forming a link with the mainland
formation of bars
Formed when a spit grows the whole way across a bay, cutting off the water to form a lagoon behind the bar.
Direct and Indirect Impacts
-Direct impacts occur through direct interaction of an activity with an environment (e.g. agriculture).
- Indirect impacts are not directly linked to an activity, but are caused as a result of direct impacts (e.g. tourism).
human impacts on coasts
> Coastal Management
> Raises interest in protecting coastal landscapes.
> Potential for economic development.
> The weight of buildings increases cliff vulnerability to mass movements.
> Changes in drainage increase saturation, leading to flooding and mass movement.
> Brings wealth and jobs to an area, boosting the local economy.
> Can cause air, soil, water, and noise pollution.
> Can destroy natural habitats for birds, animals, and sea life.
> Wildlife habitats may be created and preserved.
> Increased soil erosion.
> Increased sedimentation.
> Helps reduce risk of coastal flooding.
> Some salt marshes, sand dunes, sand bars, and spits are preserved and protected.
> Can increase erosion further along the coastline (e.g. Holderness Coast).
> Increased revenue benefits local people and economy.
> Increased desire to protect and preserve landscape as tourism continues.
> Increased pollution - littering, noise, traffic fumes (air pollution).
> Increased development of hotels and campsites impacts natural processes - increasing coastal erosion, transportation, deposition, and mass movement.
Coastal Flooding and Climate Change
- Climate change is increasing the risk of coastal flooding in the UK.
-As atmospheric temperature rises, storm frequency and strength increases. This can increase the height and power of waves reaching the coast.
- An increase in heavy rainfall and wind also increases weathering and mass movement.
-As sea temperatures rise, water expands, so sea levels rise. The melting of ice also causes sea levels to rise. Rising sea levels put low-lying coastal land at risk of flooding.
Impacts of Coastal Flooding on Environment
> Erosion increases, so beaches may disappear.
> Erosion increases, adding to coastal retreat and the risk of cliff collapse.
> Depositional features such as spits and bars may be submerged or destroyed.
> Natural ecosystems (e.g. the Essex marshes) and habitats may be destroyed.
Impacts of Coastal Flooding on People
> Flooding associated with storm surges leads to injury and death.
> Psychological and social impacts of losing homes, livelihoods, loved ones.
> Settlements need to be moved or defended, both of which are expensive.
> Coastal tourism may diminish in some areas if beaches or other landscapes are lost.
> Flooding of roads and damage to railways makes travel more difficult. People may not be able to get to work, potentially losing income.
> Loss of agricultural land affects food production and the economy.
What is it?
> Concrete walls that are placed at the foot of a cliff to prevent erosion. They are curved to reflect wave energy back into the sea.
> Protects cliffs and buildings from erosion.
> Prevents coastal flooding.
> Reflected waves are still powerful and can break down and erode the sea wall over time. This means the sea wall must be replaced.
> Can restrict beach access.
What is it?
> Large boulders placed at the foot of a cliff. They break the waves and absorb their energy.
> Cheaper than a sea wall and easy to maintain.
> Can be used for fishing.
> Allows build up of beaches
> They look different to the local geology, as the rock has been imported from other areas.
> The rocks are expensive to transport.
What is it?
> When rocks are held in mesh cages and placed in areas affected by erosion.
> Cheap - approximately £100 per metre.
> Absorb wave energy.
> Not very strong.
> Look unnatural.
What is it?
> Wooden or rock structures built out at right angles into the sea.
> Builds a beach - which encourages tourism.
> They trap sediment being carried by longshore drift.
> By trapping sediment it starves beaches further down the coastline, increasing rates of erosion elsewhere (Holderness Coast).
> They look unattractive.
A natural approach to defences, allowing processes to work and the land to change in a more environmentally sustainable way.
Tend to be cheaper, long-term, sustainable.
What is it?
> Sand is pumped onto an existing beach to build it up.
> Blends in with the existing beach.
> Larger beaches appeal to tourists.
> Sand reduces wave energy.
> Needs to be constantly replaced.
> The sand has to be brought in from elsewhere.
What is it?
> Managed retreat is the controlled flooding of low-lying coastal areas. If an area is at high risk of erosion, managed retreat could be an option. It usually occurs where the land is of low value, for example farm land.
> This is a cheap option compared to paying for sea defences.
> Creates a salt marsh which can provide habitats for wildlife and a natural defence against erosion and flooding.
> Salt marshes are diverse ecosystems supporting many species.
> Land is lost as it is reclaimed by the sea.
> Landowners need to be compensated for the loss of buildings and farmland.
> There are conflicting views about what land should be allowed to flood.
What is ICZM?
Integrated Coastal Zone Management.
It is a coastal management process that uses an integrated approach, regarding all aspects of the coastal zone, including geographical and political boundaries, in an attempt to achieve sustainability.
ICZM - Do Nothing Approach
Dealing with the effects of flooding and erosion as they come or just ignoring them. This is generally what happens in areas where there's no people, and so nothing of value (to the government) to protect.
> Cheaper than taking action.
> Homes and land can be lost.
ICZM - Hold the Line
Where existing coastal defences are maintained but no new defences are set up.
ICZM - Advance the Line
New defences are built further out in the sea in an attempt to reduce the stress on current defences and extend the coastline slightly.
ICZM - Retreat the Line
Move people out of danger zones and let erosion/destruction take place.
> Unpopular with local residents.