Coasts edexcel alevel geography

what are the consequences of coastal recession to communities?

economic - loss of property in the form of homes, businesses and farmland. relatively easy to quantify.

social - costs of relocation and loss of livelihood/jobs and impact on health

environmental - loss of coastal ecosystems and habitats

losses because of erosion are localised and coasts are specific to location e.g. farmland (20,000 per hectare) and residential land (500,000 to 2.5 million per hectare). this causes losses in amenity value and economic losses to businesses.

why are economic losses from erosion small?

- erosion happens slowly, small number of properties effected over a long time

- property at risk looses its value before its easily destroyed by erosion because potential buyers recognise the risk

- highly-populated areas tend to be protected by defences

for communities effected by the risk of erosion losses can be significant, what can it cause?

- falling property values

- inability to sell property

- inability to insure against the loss (coastal erosion is not covered)

- loss of major asset and cost of finding a new home

what help is there for people vulnerable to loosing their homes to the sea?

in the UK the 'Coastal Change Pathfinder' project helps:

- cost of property demolition and site restoration

- provides £1000 in relocation expenses e.g. removal vans

- provide £200 in hardship expenses

- help fast-track peoples planning approval to build a new home elsewhere

what is the difference between coastal flooding and coastal erosion risks?

coastal floods and storm surges are one off events, perhaps decades apart whereas erosion is a continuous process. flooding is larger in areal extent and involves greater losses e.g. in some cases can be classified as a natural disaster

what are the social and economic impacts of storm surges in developed and developing countries, 4 examples?

1. Netherlands 1953, cause - mid latitude depression moving south through the North Sea = 5m storm surge. 40,000 buildings damaged and 10,000 destroyed, 1800 deaths.

2.UK 2013 to 2014 winter storms, cause - coastal flooding by depressions and storm surges. £1 billion in damage, 17 deaths

3.USA 2012 Hurricane Sandy, cause - landfall of hurricane in New Jersey and storm surge of 4m. US$70 billion, 750,000 homes gone, 71 deaths

4.Philippines 2013 Typhoon Haiyan, cause - tropical storm = 5m storm surge. US$2 billion, 6,300 deaths.

what are environmental refugees?

communities forced to abandon their Homes because of natural processes. include sudden and slow onset events.

what are the risk factors for small islands from sea level rise?

- Tuvalu's highest point is 4.5m above sea level and most inland in 2m above sea level

- 80% of Seychelles live and work on the coast

- coral reefs are being destroyed by global warming

- limited water supply, and at risk from self-water intrusion

- small, narrow economies are easily disrupted

- high population density and limited space

what is hard engineering and is it good?

traditional management approach is to encase the coast in concrete, stone and steel. the aim is to directly stop physical processes or alter them to protect the coast.

advantage - 'one off' solution that can protect the coast for decades, obvious to locals action is being taken

disadvantage - high costs, maintenance, unattractive, have adverse affects further along the coast

e.g. groynes cost £150 to 200 per meter and sea walls. £1300 to 6000.

(actions by some players can have adverse effects for others)

what is a Rip-Rap?

- large igneous or metamorphic boulders at cliff base

- dissipate wave energy, can be at sea wall base

- reduce wave energy

- sediment deposition between rocks

- may become vegetated

what is a Offshore breakwater?

- large igneous or metamorphic boulders, placed in the offshore

- force waves to break offshore, reducing wave energy and erosive force

- deposition encouraged between breakwater and beach

- interferes with longshore drift

what is a Sea wall?

- concrete, steel reinforcements and piled foundations, can have stepped or bullnose profile

- physical barrier to erosion

- flood barrier

- dissipate wave energy

- destruction of natural cliff face and foreshore environment

- can reduce beach volume

what are revetments?

- stone or timber interlocking concrete sloping structures with are permeable

- absorb wave energy and reduce swash distance encouraging infiltration

- reduce erosion dunes

- reduce wave power

- encourage deposition may become vegetation

what are Groynes?

- vertical stone or wood 'fences' built at 90 degrees to the coast, spaced long the beach

- prevent longshore drift to build the beach by encouraging deposition

- impacts beach deposition and accretion

- prevents longshore drift starving the beach downstream increasing erosion

what is soft engineering?

attempts to work with the natural physical systems and processes to reduce the coastal erosion and flood threat. usually less obvious and intrusive and cheaper in the long term. not suitable for all coasts.

what is beach nourishment?

- artificial replenishment of the beach sediment to replace what is lost by erosion. it largess the beach to increase wave dissipation and its amenity value

- £2 million per km, ongoing costs are also high and sediment must not be sourced from the same sediment cell

what is cliff regrading and drainage?

- cliff slope angle is reduced to increase stability. revegetated to reduce surface erosion

- in-cliff drainage reduces pore-water pressure and mass movement risk

- £1 million per 100m, disruptive during construction

what is dune stabilisation?

- fences are used to reduce wind speed across the dunes

- dunes are replanted with marram and Lyme grass to stabilise surface, reducing erosion by wind and water

- fencing costs £200 to 2000 per meter

- replanting costs £1000 per 100m

cost effective in the long term

what is sustainable coastal management?

managing the wider coastal zone in terms of people and their economic livelihood, social and cultural wellbeing, safety from coastal hazards and minimising the effects on the environment and ecology.

what are the aspects of sustainable coastal management?

- managing natural resources to ensure long term productivity

- managing flood and erosion risk where possible or relocating

- monitoring coastal change and adapting to unexpected trends

- educating communities to understand why/how to change and adapt

- creating alternative livelihoods

what might sustainable coastal management lead to conflict (disagreement)?

- coastal resources may have to be used less so income may be lost

- relocation where engineering is not feasible

- some erosion/flooding will always occur, engineering cannot protect against it completely

- future trends may be uncertain e.g. sea level rise

what is the ICZM?

Integrated Coastal Zone Management - they are a coastal management planning over the long term. they involve all stakeholders and work with natural processes using 'adaptive managment'. they use a holistic approach and date from Rio Earth summit in 1992.

what are the ICZM keys characteristics

1. entire coastal zone is managed (ecosystems, resources and human activity in the zone)

2. recognises the importance of the coastal zone to peoples livelihoods

3. management of the coast must be sustainable

how does the ICZM manage coasts holistically?

they work with the concepts of literal cells

- in England and Wales there are 11 sediment cells

- each cell managed as a whole or a sub-unit

- SMP is used

- SMPs often extend across council boundaries so the councils must work together

what are the four policies for coastal management introduced by DEFRA?

1. no active intervention: coast allowed to erode landward / flood

2. hold the line: build or maintain coastal defences so shoreline position remains the same

3. managed realignment: damages the coastal erosion so it is allowed in certain areas, allows it to move more naturally

4. advance the line: build more defences on the seaward side, usually involves land reclamation

what are the factors involved to help make a decision on which policy for coastal management to use?

- economic value of assets protected

- technical feasibility of engineering solutions

- cultural and ecological value of the land

- pressure from communities

- social value of communities that have existed for century's

SMPs plans for the future have three time periods: up to 2025, 2025 - 2055 and 2055 onwards. policies are applied for a certain time period then may be changed.

cost benefit analysis for Hppinsburgh

hold the line for 600m stretch of coastline: seawall £1.8m, rip-rap £0.8-3.6m, groynes £0.1-1.5 million

costs of erosion: £160,000 to Manor caravan park to assist relocation, affected residents could get £2000 each in relocation, grade 1 St Marys church and 2-listed Manor House could be lost.

benefits of protection:

by 2105 20 - 35 houses costing £4 to 7 million would be saved from erosion, 45 hectare of farm at £945,000 would be saved.

costs £6million in sea defences, higher than the compensation costs payable to local residents supporting decision to not defend village.

what is the environmental impact assessment?

identifies: the short term impacts of construction on coast, long term impacts of building new sea defences or changing policies.

EAI is wide ranging and assess:

- impacts on water movement and sediment flow, which can effect marine processes

- impacts on water quality

- changes to flora and fauna

- wider environmental impacts e.g. air quality and noise pollution

what are winners and losers in coastal managent?

winners: people who gain from a decision. economically, environmentally or socially

losers: people likely to loose property, business or forced to move, or sea coast concreted over.

this is inevitable because:

coastal managers produce plans for entire SMP areas so some are protected and others not.

local councils and government (DEFRA) have limited resources

example where all steak holders agree on a course of action

Blackwater Estuary in Essex - area of tidal salt marsh and low-lying farmland prone to flooding and coastal erosion. was protected by flood embankments and revetments.

in 2000 Essex Wildlife trust purchased Abbotts Hall Farm which was threatened by flooding / erosion. they implemented a 4000hectare managed realignment scheme by creating 5 breaches in the sea wall in 2002. allowed new salt marshes to form inland.

why is erosion rapid in the developing world?

- upstream dams disrupt sediment cell

- rapid unplanned coastal urbanisation leads to piecemeal defences and no overall plan

- destruction of mangroves expose soft sediment to rapid erosion

in many cases the main losers are the poorest, as farmers and residents usually lack a formal title so cannot claim compensation.

Eustatic changes

- a rise or fall in water level caused by a change in the volume of water level, it is a global change in all the connected oceans and seas.

1. Eustatic fall in sea level: in glacial periods, ice sheets form at high altitudes on land and water evaporated from the sea is locked up on land as ice = global fall in sea level. - produces an emergent coast

2. Eustatic rise in sea level: end of glacial period, ice sheets melt returning water to the sea = sea level rise globally. thermal expansion leads to sea level rise. - produces a submergent coast

Isostatic changes

- local rise or fall in the land level.

1. Isostatic fall in sea level: in a build up of land-based ice sheets the weight causes the earths crust to sag. when the ice melts the land surface slowly rebounds upward over 1000s of years. this post glacial adjustment slowly lifts the land out of the sea. - produces a emergent coast

2. Isostatic rise in sea level: deposition of sediment at coasts (accretion) can cause land to sink, especially at river deltas where the weight of sediment deposition leads to slow crustal sag and delta subsidence - produces a submergent coast.

what has happened to the UK since the last ice age (12,000 yrs ago)

continuing sea level change:

- Scotland is in post-glacial adjustment by 1.5mm per year

- England and Wales are subsiding by 1 mm a year

- UK is pivoting, south sinking and north rising

- causes of global warming (eustatic) enhances sea level rising in the south but reduces it in the north.

what where the isostatic and eustatic changes in/after the last ice age?

- last ice age was called Devensian glacial period

Emergent coasts

global sea level fall off 120m as ice sheets grew

after this a fast sea level rise over the next 1000years as ice melted

slower post-glacial isostatic adjustment up to 300m in both North America and North Europe

how is an emergent coast line produced?

a eustatic or isostatic fall in sea level exposes the former sea bed as the sea level drops producing an emergent coast.

landforms of an emergent coast

- raised beaches

- fossil stump

- fossil cliff

e.g. Ayrshire and Fife in Scotland (raised beach)

how do submergent coast lines form?

on coasts that did not experience glacial ice cover, isostatic and eustatic rises in sea level cause areas of land to flood, drowning the coast line to produce a submergent coast. found along the south coast of England and the east coast of America.

What is a Ria? (submergent coast)

a ria is a drowned river valley in an unglaciated area, caused by sea level rise flooding up the river valley. this makes the river much wider than expected based on the river flowing in it. this is the most common submerged coast landform. (sea level rise pushes sea inwards, drowning valleys that where eroded by rivers a millennia ago. e.g. Kingsbridge Estuary, Salcombe, Devon)

- economically important, they are sheltered ports, miles inland

what is a Fjord? (submergent coast)

submerging coast landforms found on the coasts of Norway and Canada, they are drowned valleys but different to rias because:

- the drowned valley is a U shaped glacially eroded valley

- Fjord is deeper than the adjacent sea e.g. more than 1000m deeper

- at the seaward end of fjord there is a submerged 'lip'. this represents the former end of the glacier the filled the valley.

- in most places where there are fjords post glacial isostatic adjustment is slowly raising the land out of the sea, this is shallowing the fjords by a few millimetres a year.

what is a barrier island? (submergent coast)

offshore sediment bars, sand dunes may cover it, found 500m and 30km offshore and can be 10s of km long. e.g. East coast USA.

- may have formed as lines of coastal sand dunes attached to the shore

- sea level rise then flooded the land behind the dunes (lagoon forms) but the dunes are not eroded so become island

- the dune system slowly moves landward as sea levels continue to rise

- they protect the true coast line by causing waves to break further offshore (In USA they act as a barrier to hurricanes on the Gulf of Mexico)

how are Dalmatian coasts effected by post-glacial sea level rise? (submergent coast)

consists of limestone atnticlines and synclines forming parallel hilly islands (anticlines) and elongated bays (synclines). post-glacial sea level rise submerged this area, leaving elongated bays in once low-lying valleys.

sea level change data, past and present

the rate of sea level change today is 3 to 3.5mm per year.

- sea level was stable between 1800 and 1870 (but little accurate data from then)

- rose slowly from 1870 to 1940, accelerated after

- 1980, sea level rise faster still

- between 1870 and today sea level measurements have become better as tide gauges and satellite measurement are more precise

future predictions from the IPCC (intergovernmental panel on climate change, part of the UN)

in 2007 they thought it would be 20 to 50 cm increase

in 2013 -28 to 98 cm sea level increase by 2100

- some say 200cm by 2100

why are sea level rises difficult to predict?

there are many uncertain factors involved:

- thermal expansion (volume of water increases with global temp. rise) depends on how high global temperatures go

- melting of mountain glaciers in the Alps, Himalayas will increase ocean water volume

- melting of major ice sheets (Greenland, Antartica) could increase global sea level (significant uncertainty of when and by how much)

- local sea level changes from tectonic activity can be instant e.g. earthquakes from Turakirae in New Zealand force have raise land by 7m 5 times in the past 7000 years.

what are the features of an eroding coast line?

- long wave fetch, destructive waves

- soft geology

- cliffs with structural weaknesses

- cliffs vulnerable to mass movement and weathering and marine erosion

- strong longshore drift to leave cliff base exposed

how do human actions influence coastal retreat?

usually involve interfering with the coastal sediment cell e.g. major dams on rivers trap sediment starving the coast of a sediment source.

- Aswan Dam in 1964 reduced sediment volume from 130 million tonnes to 15 million tonnes per year. so erosion rates went from 20 meters to 200 meters per year as the delta was starved of sediment.

- Akosombo Dam Ghana 1965 reduced sediment flow in river Volta from 70 million cubic meters a year to less than 7 million effecting longshore drift and coastal erosion causing erosion of 6 to 8 m a year, and the loss of coastal road Togo.

what does dredging do?

river and sea beds dredged of sand or gravel for use construction e.g. concert. this. removes sediment source, increasing erosion down the coast. e.g. Hall sands Devon.

variations in rates of erosioN, Holderness coast in East Yorkshire

erosion varies in time and spatially.

has an average annual erosion of 1.25m but this varies spatially 0 to 6 m a year, this is not just geology as the whole coast is made of unconsolidated boulder clay.

variations occur because:

- coastal defences in Hornsea, Mappleton and Withernsea stop erosion

- Groynes and breakwaters interrupt longshore drift starving sediment for the south

- erosion rate increases north to south due to sediment starvation

- variations in cliff height and areas of boulder clay are more vulnerable to erosion

- some cliffs more susceptible to mass movement

why does erosion at Holderness vary over time?

- in winter 2-6m of erosion is common as storms and spring tides coincide to increase erosion

- constructive waves dominate in summer

- northeasterly storms cause most erosion due to fetch of 1500m from north Norwegian coast.

Shape of the beach can change to promote erosion. Ords are deep beach hollows parallel to the cliff which concentrate erosion as they allow waves to directly attack the cliff with little energy dissipation. they migrate downdrift by 500m per year so the location of most erosion changes over time.

locations with Ords erode 4 times faster.

what increases coastal flooding risk?

low-lying coastal land is densely populate because:

- popular with tourists , access to beach

- deltas and estuaries are ideal locations for trade between upriver places and coastal areas

- deltas and coastal plains are fertile, for farming

major river deltas (barely above sea level) in Asia

- Huang He- Hai (16 million, Tianjin)

- Yangtze (24 million, Shanghai)

- Chao Phraya (15 million Bangkok)

what increases coastal flooding risk in the river delta locations?

- ground water extraction causes subsidence and accelerates sinking

- river straightening (navigation) causes faster river flow so sediment is deposited further offshore

- destruction of mangroves for wood exposes coast to erosion

- storm surges flood delta more frequently

- delta subsidence is caused by weight of sediment deposition, this is balanced by new deposition on the delta surface

- sea level rise increases flood and erosion risk

- sediment trapped by dams upstream reduces deposition on delta surface

how does coastal topography influence storm surges?

in the North Sea and Bay of Bengal the coastline narrows into a funnel shape. this funnels storm surges into an increasingly narrow space, causes sever flooding. e.g. North Sea storm surge in December 2013 caused by a depression called Xavier and winds of 80mph caused a 6m storm surge. 15 deaths.

Storm surges

causes most coastal flooding in the short term, they are a short term rise in sea level cause by low air pressure.

they are caused by:

- a depression in the mid-altitudes e.g. UK

- a tropical cyclone in areas N and S of the equator

a 1 millibar fall in air pressure causes a 1 cm sea level rise because the fall in art pressure reduces the weight of air pressing down on the sea surface, allowing it to rise. then:

- strong winds push waves onshore, wave height increase effective sea height even more

- spring tides occur at the same time making sea level even higher

what is the link between global warming and coastal flood risk?

a report from he IPCC Fifth's assessment in 2014 said:

1.high confidence:

sea level - will rise between 28 to 98cm by 2100 (55cm)

Delta flooding - areas at risk from delta flooding may increase by 50%

2.medium confidence:

Tropical cyclones - frequency may remain but severity will increase

Storm surges - linked to depression are likely to be more common

3.low confidence:

Wind and Waves - some evidence of increcreased wind and larger waves

Coastal erosion - increase because of combined change to weather systems and sea level.

How do waves form?

- friction between wind and water, is a transfer of energy

- the force of wind on water surface creates ripples

- when sustained the ripples become waves

IN OPEN SEA:

- a wave is energy moving through water

- the water moves up and down

- there's some orbital water particle motion within the wave (no forward motion)

what does wave size depend on?

- wind strength

- duration the wind blows for

- water depth

- Fetch (uninterrupted distance over water which a wind blows allowing the wave to grow in size)

How do waves break?

As the water depth shallows towards a coast line:

- at a depth of half the wave length the internal orbital motion of water in the wave touches the sea bed

- friction between wave and sea bed slows the wave down

- approaching the shore wavelength decreases and height increases (bunch together)

- wave crest moves forward faster than wave trough

- eventually outruns trough and wave topples forward (breaks)

describe a constructive wave

- low wave height, below 1m

- long wavelength 100m

- strong swash, weak backwash

- pushes sediment up the beach depositing it as a ridge (berm)

- backwash drains into beach sediment

describe a destructive wave

- wave height over 1m

- short wavelength 20m

- strong backwash erodes beach carrying sediment offshore, creating offshore ridge or berm

what timescales change the type of waves?

- a day, storm passes and destructive waves become constructive when winds drops

- between summer and winter

- changes to climate

how do beach landscapes change?

- storm beaches; high at the back from high energy deposition of coarse sediment

- berm ridges, shingle, from summer swell wave deposition

- low channels and runnels between berms

- offshore ridges/bars from destructive wave erosion and deposition offshore

what are the 4 Marine erosion processes?

1. hydraulic action - air trapped in cracks is compressed by the force of waves crashing against the cliff face, this pressure forces cracks open, and the process continues. dislodges blocks of rock from the cliff face.

2. abrasion - sediment in breaking wave is thrown against cliff, acts like a tool chiseling and wearing down the face

3. attrition - sediment within waves collide making it smaller and rounded

4. corrosion (solution) - carbonate rocks (limestones) are vulnerable to solution by rainwater, spray from sea and seawater

how does the erosional coastal landform - cave, arch, stack, stump - form?

- the base of cliff is eroded by hydraulic action and abrasion creating a wave-cut notch

- notch becomes a cave, then arch

- overhanging rock becomes unstable and collapses as a rock fall leaving a stack

- repeated cycle of notch cutting and elapsed cliff cause cliffs to recede inland

- the former cliff position becomes a wave-cut platform

stack is eroded into a stump

what are the 4 ways sediment is transported?

1. traction - sediments rolls by ocean currents e.g. pebbles

2. saltation - sediment bounces by force of water to wind e.g. sand sized particles

3. suspension - sediment is carried in water e.g. silt particles

4. solution - dissolved material is carried in water as solution e.g. chemical compounds in solution

what is longshore drift?

process of sediment transport along the coast where waves approach the coast at an angle, the swash and backwash zig zag up and down the beach, although predominantly in the direction of the prevailing wind.

- transport also occurs from waves that approach the beach at 90 degrees.

what two ways does deposition occur?

1. gravity settling - when the wave runs out of energy and can't move the sediment, heaviest sediment deposited first (pebbles, sand, silt)

2. flocculation - small particles (clay) remain suspended in water, these clump together through chemical attraction becoming large enough to sink

vegetation is key in depositional landforms e.g. plant succession.

what is a spit?

A sand or shingle beach ridge extending beyond a turn in the coast line, more than 30 degrees. at the turn longshore drift current looses energy = deposition.

the length depends on the presence of a secondary current causing erosion e.g. flow of a river

what is a Bayhead beach?

Waves break at 90 degrees to the shoreline and move sediment into a bay, forms a beach. Wave refraction occurs at the headland, leaving the bay and area of deposition.

what is a Tombolo?

A bar that links a coastline to an offshore island, as a result of wave refraction around an offshore island creating a calm area of deposition between the island and coast. may be similar to a spit where opposing longshore currents occur.

what is a Barrier beach?

A sand beach connecting two areas of land, with a lagoon behind. form when a spit extends across a bay, closing it off.

what is a Hooked spit?

A spit whose end is curved landward, into a bay. seaward end naturally curves landward to shallow water, the hook becomes more pronounced by secondary waves from another direction to the prevailing wind.

what is a cuspate foreland?

Triangle features extending out from a shoreline. May result from the growth of spits from opposing longshore drift directions, but their formation is not known.

what three components make up a sediment cell?

1. source - sediment generated e.g. cliffs or offshore bars

2. transfer zone - where sediment moves by longshore drift and offshore currents e.g. beaches, dunes

3. sinks - dominant location of deposition e.g. spits

- system operates in a dynamic state of equilibrium

what is an example of the negative feedback system in a sediment cell?

it helps maintain the balance by:

1. in an erosion event large amounts of cliff collapse. the rock debris at the base will slow erosion by protecting the cliffs base from wave attack.

2. erosion of sand dunes could cause excessive deposition offshore, offshore bar forms that reduces wave energy helping dunes recover.

(subaerial processes) what are the three types of weathering?

1. mechanical - breaks rocks by the exertion of physical force

2. chemical - chemical reaction and generation of new chemical compounds

3. biological - action of plants, bacteria or animals. it offer speeds up other weathering.

- weathering does not involve any movement

what is the influence of mechanical weathering on lithology?

1. Freeze-thaw: water expands by 9% when frozen, exerts force within cracks. repetition cracks and loosens rocks - especially high on cliffs away from salt spray

2. Salt crystallisation: growth of salt crystals in cracks and pores, exerts breaking force (less than freeze thaw) - pours and fractured rocks e.g. sandstone

what is the influence of chemical weathering on lithology?

1. carbonation: slow dissolution of limestone due to rainfall (carbonic acid pH 5.6) producing calcium bicarbonate in solution. - limestone and other carbonate rocks

2. Hydrolysis: breakdown of minerals to form new clay minerals due to the effect of water and and dissolved carbon dioxide. - igneous and metamorphic rocks with feldspar / silicate mineral

3. Oxidation: addition of oxygen to minerals producing iron oxides and increasing volume, contributes to mechanical breakdown. - sandstones, siltstones and shales containing iron compounds

What is the influence of Biological weathering on lithology?

1. Plant roots: trees and plant roots grow in cracks facing rocks apart. - on vegetated cliffs, can contain roclfalls

2. rock boring: clams and molluscs bore into rocks. - sedimentary rocks, carbonate rocks in the inter-tidal zone

what is the mass movement process Rockfall?

- rapid form

- blocks of rocks become dislodged by mechanical weathering or hydraulic action

- undercutting cliffs (wave cut notches) leads to large rockfalls and talus scree slopes at their base.

(2013 large rack fall in St Oswald's bay, Dorset in the cretaceous chalk cliffs, happened overnight, 100m off cliff gone)

what is the mass movement process Rock topple?

- influenced by geological structure

- rock strata has a steep seaward dip

- undercutting by erosion causes instability

- blocks will topple seaward

what is the mass movement rotational slumping?

- on a curved failure surface

- in a rotational slide, huge masses of material can slowly rotate downslope over days or years

- water heavily effects it

- leaves a back-scar and terraced cliff profile

what is the mass movement Rock flow?

- weak, unconsolidated sands and weak rocks

- materials become saturated and lose their cohesion, flow downslope

- heavy rainfall and high waves and tides contribute to saturation

What is the mass movement Translational side?

- a very low angle seaward dip in strata will prevent falls

- it will encourage rock / translational slides

- material slides down the dip slope towards the sea

what causes a rotational slide?

1. the bedding plane between the impermeable clay and permeable sands dips seaward, promoting mass movement.

2. cracks develop on top off the cliff in dry weather when soil and sediment dries out. these become routes for rainwater into the permeable sand.

3. heavy rain saturates permeable sands, loading cliff material.

4. water percolates through the permeable sand but is forced to move along the sand/clay boundary as the clay is impermeable. this contributes to high pore water pressure in the sand and creates internal pressure within the cliff.

5. Toe erosion by marine processes undercuts cliff below

6. curved failure surfaces develop in the sand, and the whole cliff begins to rotate about a pivot point.

produces backscar and terraces.

what is the littoral zone?

is a dynamic area of high risk consisting of the coast, back shore, foreshore, nearshore and offshore. risks include coastal flooding and coastal erosion.

what are the two classifications for coast types

1. rocky (clipped). these coastlines vary in height from a few meters to hundreds of meters

2. coastal plains (no cliff). the land slopes to the sea across deposited sediment.

how do you classify a coast by it's formation processes?

1. primary coasts, dominated by land based processes such as deposition from rivers or new coastal landforms from lava flows

2. secondary coasts, dominated by marine erosion of deposition processes

how do you classify a coast by relative sea level change?

1. emergent coasts, the coast rises relative to sea level, e.g. as a result of tectonic uplift

2. submergent coast, flooded by the sea because of sea level rise or subsiding land

how do you classify a coast by tidal range?

tidal range varies along coasts:

- microtidal (0-2 m range)

- mesotidal (2-4 m range)

- macrotidal (more than 4 m range)

how do you classify a coast by wave energy?

1. low energy, sheltered coast with limited fetch and low wind speed and small waves

2. high energy, exposed coasts facing prevailing winds with long wave fetches resulting in powerful waves

Rocky coasts

two main cliff profile types:

1. Marine erosion dominated: wave action dominates and the cliffs tend to be steep, unvegetated with little rock debris at the base.

2. Subaerial processes (weathering and mass movement) dominated: not eroded at the base by waves, shallower, curved slope and lower relief, surface runoff erosion and mass movement are responsible for the cliff shape.

coastal plains

situated just above sea level they are poorly drained because of the flat landscape, create estuary wetlands and marshes. They are low energy environments.

when do coastal plains form?

- sea level falls, exposing the sea bed.

- coastal accretion (deposition of sediment at a coast that expands the area of land) so coastlines gradually move seaward.

- sediment moved from offshore to the coast by ocean currents.

what are the three elements to geological structure?

1. Strata - layers of rock in a cliff

2. Deformation - tilting and folding by tectonic activity

3. Faulting - major fractures that have moved rocks from their original position

what two coasts does geological structure provide?

1. concordant (pacific) coast - when rock strata runs parallel to the coast

2. discordant (Atlantic) coast - when different rock strata intersect the coast at an angle, creating a variation in rock type at the coast

how do headlands and bays form at discordant coastlines?

e.g. West Cork coast in Ireland

- rock strata meets the coast at 90 degrees in parallel bands of Old red sandstone, purple mudstone, limestone, sandstones and mudstones.

- weak rocks have been eroded, creating elongated, narrow bays e.g. Bantry Bay (Limestone)

- more resistant rock gets eroded slower creating headlands

- especially resistant areas remain as detached islands e.g. Clear Island (Old Red Sandstone)

these headlands change over time as headlands are eroded more than bays.

Wave refraction at headlands and bays

- in deep water wave crests are parallel

- water shallows towards the coast, waves slow and increase in height

- at bays: wave crests curve to fill the bay and decrease in height

- the straight wave crests refract (curve), concentrating on headlands

- this is wave refraction as it concentrates powerful waves on headlands to increase erosion there and decrease erosion at bays as the waves decrease in power and size there.

what is an example of a concordant coast?

Lulworth cove

- the hard Portland limestone and Purbeck Beds protect the softer Wealden and Gault beds

- marine erosion breaks through the resistant beds, rapidly eroding a wide cove behind

- resistant chalk at the back of the cove prevents further erosion

What is an example of a concordant coast?

Dalmatian coast

The Dalmatian coast in the Adriatic Sea:

- limestone geology. the limestone has been folded by tectonic activity into a series of anticlines and synclines (geological folds caused by tectonic compression. anticlines form crest and synclines form troughs). This underlying structure formed by erosion from river, has been drowned by sea level rise to create long narrow islands arranged in lines offshore which trend parallel to the modern coastline.