coasts

Question 1

describe the different types of erosional processes

Answer 1

• hydraulic action is when a wave advances on a coastline air can become trapped and compressed either in joints and faults in the rock. the high pressure causes the cracks to be forced apart and fracture so pieces of rock break off.
• solution/corrosion is when weak acids in seawater dissolve alkaline rock such as limestone
• attrition is when wave action cause rocks and pebbles to hit against each other, wearing each other down so that they become more rounded and smaller
• abrasion is when sediment is dragged up and down the coastline, eroding and smoothing rocky surfaces
• wave quarrying is when breaking waves hit the coastline exerting pressure which scoops out loose unconsolidated material

Question 2

describe longshore drift

Answer 2

• waves hit the coastline at an angle determined by the direction of the prevailing wind
• the waves push sediment up the beach at this angle as the swash
• due to gravity, the waves carry this sediment back down the beach at backwash perpendicular to the coast
• over a period of time, sediment is transported in a zigzag fashion along the coast

Question 3

what are sediment cells?

Answer 3

• sections of coastlines where the movement of sediment is contained within a closed system which are often bordered by two headlands
• the inputs within the sediment cell come from erosion of the sea bed or land such as cliff erosion
• there is little or no movement of sediment between the cells
• human activity can disrupt the natural system’s equilbirium

Question 4

what factors affect coastal erosion?

Answer 4

• the rate and type of erosion is related to the type of wave reaching the coast. destructive waves are the largest and most powerful with a strong backwash which removes sediment
• the more resistant the rock such as hard rocks like granite the slower it erodes whereas softer rocks like clays and shales erode more quickly
• if there is a beach present on the coastline the beaches will absorb wave energy and reduce the impact of the waves on the cliff. therfore if coastla mangement strategies like groynes are implimented this can trap sediment and prevent sediment from accumualting at other regions along the coast thus increasing the erosion rates there.
• subaerial processes such as the processes of weathering and mass movement will weaken cliffs and create piles of debris which can lead to increased abrasion and corrasion
• increase in erosion rates if there are greater geological structures like faults, joints and cracks which create weaknesses that can be exploited by erosive processes as well as increasing the rock face surface area which further increases rates of erosion

Question 5

outline the devleopment of barrier beaches

Answer 5

• a barrier beach is usually formed as an extension of a spit
• longhsore drift transports sediment along a coastline until there is a change in the shape of the coastline causing deposition of material which forms a spit, typically in a bay
• as the spit extends a barrier beach forms which can be colonised by vegetation which stabilises the sand and traps further sediment

Question 6

describe the formation of caves, arches, stacks and stumps

Answer 6

• along a discordant coastline ther are bands of hard and soft rock which are perpendicular to the coasltine.this allows for the formation of erosional landforms like headlands and bays
• faults in the headland are exposed to erosional process such as hydraulic action and abrasion leading to the crack widening and a small cave forming
• occasionally, wave action and weathering causes joints in the cave rood to erode forming a blow hole
• the cave will expand due to marine and subaerial erosion causing it to erode through the other side of the headland to create an arch
• the arch widens until it is unable to support itself so the roof of the arch becomes unstable and collapses forming a stack which is detached from the mainland
• sub-aerial and marine erosion can attack the stack causing it to form a stump

Question 7

describe the formation of a wave-cut platform

Answer 7

• when waves erode a cliff, the erosion is concentrated between high tide line the cliff begins to undercut, leading to the formation of wave-cut notch
• as the wave-cut notch deepens due to marine erosion like hydraulic action and sub aerial weathering, the cliff face becomes unstable and falls due to gravity in mass movement
• this leads to the retreat of the cliff face and leaving a wave-cut platform

Question 8

describe the formation of headlands and bays.

Answer 8

• along a discordant coastline the rock layers are perpendicular to the coastline
• erosional processes attack the areas of softer, less resistant rock whilst the harder, more resistant rocks aren’t as vulnerable to erosion thus remain protruding from the coastline

Question 9

describe the formation of a spit

Answer 9

• the pervailing wind pushes waves up the beach at an angle as the swash and when the waves retreat back down the beach at a right angle as the backwash they travel perpendicular. this is known as longshore drift which enables the mass transport of sediment
• when the mainland experiences a change in the shape of the land the sediment is deposited and builds up causing an extension of the mainland known as the spit
• if there is a change in the direction of the prevailing wind the spit can form a hook. due to the hook creating a sheltered area then a salt marsh should be created as salt-tolerant vegetation colonises

Question 10

explain the different types of weathering

Answer 10

• freeze thaw weathering is when water enters the cracks and freezes causing the water to expand by 10 percent in volume which exerts pressure on the rock causing cracks to develop which makes its vulnerable to weathering
• crystallisation is when sea water evaporates salt crystals are left behind. these crystals exerts pressure on the rock whcih forces cracks to widen
• carbonation is when carbon dioixde in the air creates weak carbonic acid which reacts with calcium carbonate rocks to create calcium bicarbonate that can easily be dissolved
• oxidation is when rock becomes exposed to air through cracks and fissures their iron will be oidised into a ferric state, which is known as rusting

Question 11

Describe the process of mass movement

Answer 11

• rockfalls occur on sloped cliffs, mostly vertical cliff faces. It leads to the formation of a scree (a build up of rock fragments on the base of a slope)
• landslides occur when heavy rainfall causes water to enter into joint and beddping plains in the cliff face reduces friction and causes a block of intact rock to move down the cliff face rapidly

Question 12

benefits and drawbacks of groynes

Answer 12

groynes trap sediment which is transported by longshore drift to build up the beach on the updrift side of the groyne. larger beaches provide a more effective buffer as it absorbs the waves energy

• groynes involve less investment from local councils as they only cost £400 per meter
• they create larger beaches which attracts tourism as there is more space for activities
• longshore dirft being halted deprives areas downwind of the sediment which increases the erosion there

Question 13

benefits and drawbacks of a sea wall

Answer 13

• concrete structures with recurved faces that reflect the wave energy back out to sea to minimise the erosional processes on the cliff face
• visually unaesthetically pleasing
• they are expensive as they cost £5000 per metre
• they can be used as a promenade which atracts tourism
• they are durable with a lifespan of 75 years

Question 14

benefits and drawbacks of rock armour/rip rap

Answer 14

large rocks and boulders are placed at the base of a cliff in order to deflect wave energy and reduce the erosional impact on the cliff

• plants can establish in the rocks which icnreases biodiversity
• they are relatively cheap as they only cost £1000 to £3000
• the rocks are soruced from elsewhere which disrupts the antural local geology

Question 15

benefits and drawbacks of beach nourishments

Answer 15

involves adding sand and shingle to the beach from elsewhere in order to build up the beach so that it can absorb the wave energy

• creates a wider beach which can attract toursits for more activities
• it is a cheap method originally however requires ongoing investment as sand has to be continuously added

Question 16

benefits and drawbacks of sand dune regneration and stabilisation

Answer 16

this can involve the artificial creation of new sand dunes or the restoration of existing dunes. marram grass is planted so that the roots can stabilise the sand that makes up the dunes. the sand dunes act as a barriers between the sea and land, and absorb the wave energy

• it creates an important environmental habitat
• small planting projects use volunteers so the labour cost is minimal
• there is no gaurantee that they will stay

Question 17

describe the location of the holderness coast

Answer 17

holderness coast is located in East Yorkshire, in the North East of England

Question 18

key facts about the holderness coastline

Answer 18

• the coastline is one of Europe’s fastest eroding coasts with erosion occuring at an annual average rate of of 2 metres per year
• coastline has retreated by almost 400m in the last 2000 years
• the bed rock of the coastline consists of cretaceous chalk however is covered by glacial till which is soft boulder clay which is vulnerable to erosional processes
• strong prevailing winds create longshore drift that moves material southalong the coastline

Question 19

what coastal management strategies have been implimented along the holderness coastline

Answer 19

• at Mappleton there have been rock groynes erected which halt the process of littoral drift in order to maintain wide beaches however the groynes have starved the coastline downdrift of material leaving them vulnerable to erosional processes
• a sea wall has been constructed at Withernsea, costing £5000 per metre and is protected further by rock armour. the rock armour was introduced to disspiate the waves energy to reduce the impact on the sea wall

Question 20

positive feeback loops along holdnerness coastline

Answer 20

• construction of groynes along the coastline has increased erosion rate down drift of the groyned due to them halting the process of littoral drift which starves the beaches of material
• global warming due to rising atmopsheric carbon levels creates a rising eustatic sea level which puts the shoreline of Spurn Head at risk of flooding

Question 21

negative feedback loops along the holderness coastline

Answer 21

-cliff erosion occurs at Flamborough head which leads to unconsolidated material undergoing slumping. this reduces the cliff retreat as the slumped material acts as a natural barrier to marine erosion

Question 22

describe the location of the sundarbans

Answer 22

Sundarbans are located in Southern Asia, in the country of Bangladesh. It is part of the largest mangorve forest in the world, protected as a natural park. the topogrpahy of the land is low lying and flat

Question 23

opportunities in the sundarbans

Answer 23

-flat, fertile land of deltas is beneficial for growing crops

Question 24

risks in the sundarbans

Answer 24

• the Sundarbans has experienced sea level rise as a result of Eustatic change with a 3 to 8 mm sea level rise annually
• this has caused the submergence of land mass which has rendered up to 6000 families homeless which has promoted the flight of human capital to the mainland
• inundation of water can cause the salination of soils which effects agricutlure in the region as crops are unable to grown

Question 25

adaption in the sundarbans

Answer 25

-involves adjusting behaviour to fit the environment.

• Salt-resistant varieties of rice are being grown which helps residents to cope with flooding. However, relying on a smaller range of crops will reduce biodiversity and increase vulnerability to disease.
• Projects are underway to increase tourism, providing jobs and income e.g. lodges have been built. However, if not managed sustainable, it can create environmental damage.
• People can adapt to sea level rise through building houses on stilts, but roads and infrastructure cannot be protected as easily.
• Sustainable development can be underway as non-intensive farming practices and promoting eco-tourism will help ensure the fragile environment remains relatively undamaged.

Question 26

mitigation in the sundarbans

Answer 26

• mitigation involes reducing the severity of hazards.
• 3,500km of embankments were built to prevent flooding. However, the embankments are gradually being eroded, and around 800km are being vulnerable to breaches during storms.
• Coastal management projects aim to protect existing mangrove forests and replant areas that have been removed, to protect against flooding and erosion. But it is difficult to prevent illegal forest clearance. It is unclear if mangrove forests will withstand sea level rise.
• The government and NGOs have provided funding for cyclone shelters and early warning systems, however many people may not have transport available to evacuate quickly.

Question 27

outline the cocnept of eustatic sea level change

Answer 27

• eustatic sea level change is a global change in sea levels due to the rise or fall of the level of the sea
• in glacial periods, more water falls as ice and snow and accumulation causes it to become compacted into glaciers or ice sheets meaning water is cycled into the cryosphere. this causes sea levels to fall.
• in integlacial periods, ablation of glcaiers and ice sheets occurs meaning water is cycled into the sea causing a rise in sea levels.

Question 28

outline characteristics of constructive waves

Answer 28

• long wave length
• they have a stronger swash and weaker backwash
• they have a longer wave period

Question 29

outline the role of wind in affecting coastal energy

Answer 29

• wind generates friction on the surface of the water which forms waves
• stronger winds with a larger fetch will generate more powerful waves
• the prevailing wind directs the angle at which the waves hit the shore in longshore drift