COASTS- 4 markers

explain the processes leading to the development of waves

- the wind blows over the ocean

- this creates friction, leading to a circular orbit

- as the wave approaches the coastline, the friction of the sea bed creates an elliptical orbit, pushing the crest of the wave upwards

- eventually a critical point is reach when the crest breaks

constructive waves= deeper beach profile= less friction so crest isn't pushed up as far

destructive waves= shallow profile= more friction so the wave is pushed up further

explain the development and importance of wave refraction

due to the varying geomorphology of beach profiles, waves refract towards the headland

- waves initially enter the coastline parallel, yet as they hit sediment they begin to drag and refract towards the headland

- erosion becomes concentrated at the headland, and deposition at the coastline

- the waves pile into the headland= slight local rise in sea level causing longshore currents moving eroded material to the beach

explain the development of currents

- longshore currents: a flow of water runs parallel to the shoreline in areas where waves approach at an angle. they move water and sediment along the shoreline

- rip currents: wind pushes surface water onto the beach, causing the sea to rise. this results in the quick movement of water back at the path of least resistance- causing the rip to flow

- 'upwelling': the wind blows warmer water off the surface, causing an uplift of cooler water rising to replace the water that evaporated

explain the development of tides

- gravitational pull of water towards the moon. = periodic rise and fall of sea level

- 2x a month - sun and moon are aligned (full moon)= spring tide = largest bulge

- 2x a month - sun and moon are at 90°= neap tide

explain the development of tidal surges

- meteorological conditions lead to strong winds which leads to a local rise in water (higher than spring tide)

explain the difference between a high and low energy coastline

Low- when deposition exceeds erosion. Low energy, constructive waves.

Typical landforms include beaches, spits, bars

High- erosion > deposition

Strong steady prevailing winds creating high energy destructive waves

Typical landforms; headlands, cliffs, wave cut platforms

explain the concept of a sediment cell

- a closed system usually bounded by headlands or a change in longshore drift (1).

-Within a sediment cell, there is erosion, transport and deposition of sediment within a long term cycle (1).

-The only inputs into the sediment come from erosion from the sea bed or land (1).

-There is little or no movement of sediment between cells (1).

-Human activity such as beach management can interrupt the natural system creating imbalance within the cell leaving some areas at risk of erosion (1)

explain the concept of a sediment budget

The balance between sediment added and removed from the coastal system

Budgets can be: positive (sediment surplus) or negative (sediment deficit)

Coastal erosion can control the sediment budget of the coastal system - more erosion = more deficit

Can be used to identify sources of sediment that deliver sediment to the system - stored in sinks

explain the processes of marine erosion

The breakdown of rocks along a coastline- due to marine factors (waves/ tides/ LSD)

Caused by :

-hydraulic action- sheer force of the wave exerting force on the rock, causing pressure to build up, weakening the rock's surface

-abrasion, material picked up by the sea that wears away at rock faces

-attrition, the rocks in the sea are slowly ground down into smaller, rounder pieces

-wave quarrying, breaking of a wave trapps air on the cliff face, compressing it causing pressure to build up - as it pulls back = pressure is released - weakening the rock face

-solution- form of weathering, yet it contributes to coastal erosion. Solutes dissolved in water chemically breakdown rock

outline the factors that affect coastal erosion

-wave steepness/ breaking point

- fetch

- sea depth

-coastal configuration (headlands will attract wave energy)

- human activity - sea defences can impact the sediment budget of a cell

-geology

explain how geology has an impact on erosion

- Concordant / discordant coastlines - impact differential erosion

- The direction of rock strata (dip)also has an influence on the rate of erosion

Outline the process of sub-aerial weathering in the development of coastal landscapes

Sub-aerial processes refer to the processes of weathering and mass movement. Weathering is the breaking down of rock in situ.

Two types: Chemical weathering & Mechanical weathering→ freeze-thaw & biological

These processes operate on the cliff surface and weaken it, providing material for coastal erosion.

Biological weathering: vegetation can protect the cliff face, but it's roots can grow in cracks and widen them

Freeze-thaw: Exposed rock faces can be broken up by ice, or heat and cold. For example, repeated freezing and thawing of water in rock cracks weakens the rock. This is physical weathering.

Chemical weathering: Salt crystals can penetrate the exposed rock face. Where there are rocks containing iron oxidation can occur, causing it to 'rust'.

OR

Mass movement: Rocks such as clay become saturated with water. The rock is weakened and mudflows occur. Rock falls are a very sudden type of mass movement. The sea can use these boulders to erode the cliff further.

outline the processes of marine deposition

Marine - when waves are low energy - or rapid erosion provides an abundance of sediment.

- when waves pause at swash before backwash

-when water percolates beach material as backwash takes it back.

- when sand and shingle accumulate faster then they are removed

outline the processes of aeolian deposition

Air moves due to differential pressure - warmer land and cooler sea with a large tidal range = lots of sediment picked up by wind

- surface creep: wind rolls sand grains along the ground

- saltation: wind is strong enough to lift the grains- shapes depositional landforms (dunes)

outline processes of physical weathering

- freeze thaw: latitudes with fluctuating temperatures (above and below freezing). Water enters cracks in rocks, when below 0 degrees, freezes, expands (by almost 10%) - puts pressure on the rock causing the crack to widen, and eventually breaking them off

- Pressure release: erosion, mass movement remove overlying material the rocks beneath experience a pressure release , causes cracks and joints to develop = susceptible to other types of erosion

outline the processes of biological weathering

Through the action of vegetation and organisms

- pillock (shellfish) their shells drill into rocks, causing pitted holes - weakening the rocks

- some organisms (algae) secrete chemicals that promote solution

- seaweed attaches to rocks on the bottom of the sea, swaying of the seaweed caused them to be prised off the base of the sea.

outline the processes of chemical weathering

When the rocks are exposed to air and moisture that causes the chemical breakdown of rocks

- oxidation; oxygen dissolves in water reacts with minerals (especially iron rich rocks)

- Hydration; addition of water to minerals in rocks, causes the rock to expand= pressure - breaks rock causing it to be more susceptible for further erosion

- carbonation; dissolved CO2 → weak carbonic acid → reacts with calcium carbonate in limestone and chalk → calcium bicarbonates (more effective in low temp areas as it increases the amount of dissolved co2)

outline the processes involved in mass movement

Nature on mass movement is impacted by many factors; level of sediment cohesion, steepness of the slope, grain size of sediment, temperature and saturation.

- landslides; soft rock/ unconsolidated rock becomes lubricated after heavy rainfall

- rock fall; rocks that are undercut by the sea collapse under gravity

Mudflows; fine soil and heavy rainfall- causes material to flow downhill

- rotational slip/ slumping; soft material overlies harder material - excessive lubrication- causes plane to slide

- soil creep; slow continuous movement of soil particles downslope

outline the factors that influence the formation of landforms

Geology, lithology, angle of the rock strata, nature of the waves, strength/ direction of PW, wave refraction

outline the formation of wave-cut platforms

High energy, steep waves break at the foot of a cliff - erosion concentrated at the base of the cliff, undercuts the cliff forming a wave cut notch. Continual erosion (abrasion and wave quarrying)- increases overhang and stress on the cliff above - collapses due to lack of support. The cliff line retreats- causing a gentle sloping, smooth wave cut platform- exposed at low tide.

outline the formation of headlands and bays

Discordant coastline- where bands of less resistant and resistant rock are perpendicular to the coastline. Erosion dominates in the less resistant areas - forming bays, resistant rock protrudes out to sea (differential erosion)- headland receives the highest wave energy = more vulnerable to erosion due to wave refraction- energy concentrates at the headland. Low energy environment causes deposition at the bays - protecting the coastline. Causes waves to break further out - limiting erosion = negative feedback

Outline the formation of geos / caves / blowholes / arches / stacks / stumps

Cracks, joints and bedding planes are eroded by hydraulic action and abrasion, widening the crack causing a steep sided inlet - geos, or the rocks are undercut causing a cave to form.

If erosion continues upwards, a blowhole is created. Otherwise the erosion extends backwards, breaking through the other side of the headland - forming an arch. Wave cut platform develops, the arch collapses due to lack of support and gravity- aided by subaerial processes - forming a stack, which will eventually collapse into a stump.

explain the formation of a Spit / tombolo / barrier beach / offshore bar

Dependent on the sediment input and wave energy to move it.

Formation:

- material carried by LSD- influenced by the direction of the prevailing wind (SW- material transported east)

- if coastline changes to a north south orientation - sand builds up in the sheltered lee of the headland - material projects easeward.

- storms build material above the high water mark

- finer material carried further eastward into the estuary- and becomes deposited extending the spit into the estuary

- end of the spit curves round due to wave refraction

- can't grow all the way to the mainland as the material is carried away by the deeper, faster section of the river

As they mature, sand is blown onto the landward side forming sand dunes

Area behind a spit is low energy and sheltered, where silt and clay are deposited, and become colonised forming salt marshes.

outline the conditions needed for sand dune formation

- Dynamic landform that require a plentiful input of sand

- strong onshore winds due to the differential atmospheric pressure between the land and sea

- a large tidal range

- an obstacle to trap the sand

- vegetation to encourage further growth of the dune

Outline the conditions needed for mudflat formation

- estuaries, towards the landward side of a spit

- low energy environment, where he river flows slowly

- composition of both salt and freshwater

Saltwater brings fine sediment, river brings silt and clay → particles meet and flocculate forming heavier particles that sink to the bottom of the bed

- intertidal area: low - mud is exposed, covered at high tide when flocculation occurs

what are mudflats susceptible to?

- changes in sea level

- wave action

- changes in river discharge (too little - not enough silt/ clay, too high = erosion - no flocculation)

- changes in tidal flows

outline the succession of a mudflat to a salt marsh

Succession develops a halosere environment - tolerant to salty conditions

Low lying vegetation (eelgrass) grows on the mudflats, slows currents causing more deposition - yet uneven.

- pioneer species colonies that are salt tolerant (halophytes) - glasswork, sea-blite. They develop a root system - secures up to 2m of material= trapps ,over mud.

Pioneers develop close vegetation= allows other species to colonise (marsh grass, sea lavender) → forms dense vegetation = trapps more mud

Dead organic matter accumulates further growing the saltmarsh

As they rise - complex creek systems form and marsh becomes higher - above high tide and mature species - oak can now colonise the area.

Outline the different types of sea level change

Eustatic change - global change in sea level due to the actual rise or fall of the sea level itself

Isostatic change - local changes in sea level due to the land rising or falling relative to the sea

Tectonic change - rise or fall in sea level due to tectonic processes

outline the formation of an estuary

an estuary is where the river meets the sea

- formed by tides and surges

- tidal river so when the sea retreats, the volume of water in the estuary is reduced

- when there is less water, the river deposits silt to form mudflats

- this interaction of salt and fresh water also encourages flocculation to occur.

outline the processes which lead to the development of barrier beaches

- a barrier beach is formed as an extension to a spit

- longshore drift moves sediment along the coastline until there is a change in the coastline.

- the spit develops across the whole bay forming a barrier beach

- colonisation by vegetation can stabilise the barrier beach and trap further sediment. these species are able able to withstand these conditions

depending on the climate, the landwards side may be colonised by mangroves in the still lagoon which adds further stability

outline the formation of mangrove forests

- tropical trees that grow along coastlines and help maintain the health of coastal environments

- sand is washed out of the delta and deposited on banks

- strong monsoon winds then blow them into larger ranges of sand dunes

- with the protection of the dune, finer silts washed into the bay are deposited, where wave action then adds and shapes further deposits of sand to form new islands

vegetation establishes itself, colonising the area. If natural succession can process, the Mangrove forests develop

explain the development of salt marsh environments

- salt marshes tend to develop in sheltered estuarine areas behind spits

- as the spit develops, the area behind it becomes sheltered

- silt is deposited by the river which gradually builds up to form an intertidal mud flat

- the mudflat continues to build and rise above sea level with the addition of further silt

- vegetation which is highly adapted to the saline environment colonises the mud which itself traps further sediment

THE SALT MARSH ENVIRONMENT IS COLONISED BY HALOPHYTIC VEGETATION

outline the features of a Dalmatian coastline

- topography of the land which runs parallel/ concordant to the coastline

- they are named after the Croatian Adriatic Dalmatian coastline

- they were formed by changes to the volume of water in oceans, where fold hills and hence valleys lie parallel to one another

- when these valleys are flooded, the tops remain above sea level, and appear as a series of long, thin islands running parallel to the coastline