Coasts Flashcards
What are coastal zones
Dynamic environment a with distributive landscapes formed by the interaction of a range of wind, marine and terrestrial processes
How much of the worlds population live on coastal plains
About 50%, with over 59% living within 150km of the sea
What kind of systems are coastal environments
Open systems
Example of feedback in a coastal system
Increased deposition on a beach but there is no corresponding change in the amount of sediment removed from the beach, then the beach features may change and the equilibrium is upset
What are inputs into an open coastal system
Energy from:
Waves
Tides
Sea currents
Sediment
Geology of the coastline
Sea level change
Transfers in an open coastal landscape
Erosions processes
Wind and water transport
Components in an open coastal system
Erosional landforms and landscapes.
Depositional landforms and landscapes.
Outputs in an open coastal system
Dissipation of wave energy.
Accumulation of sediment above the tidal limit.
Sediment removed beyond local sediment cells.
Example of a negative feedback mechanism in a coastal environment
A beach in dynamic equilibrium.
Sediment is erodes from the beach during a storm.
Sediment is deposited offshore forming an offshore bar.
Waves now forced to break before reaching the beach disposing their energy and reducing further erosion when they reach the beach.
When the storm calms, normal wave conditions rework sediments from the offshore bar back to the beach.
What do some negative feedback mechanism act to do
Stabilise coastal morphology and maintain a dynamic equilibrium
What kind of landscape is a coastal landscape
Geomorphological
What do coastal landscapes consist of
A constantly changing assemblage or erosion and depositional landforms; they are the result of continuous change in the elements of a coastal system
What do the processes operating in coastal systems that continually shape the coastal landforms create
Distinctive landscape features
What does the coastline itself consist of
A series of different zones where specific conditions prevail that depend on factors such as tides, wave action and the depth of the sea
What are the 5 different zones in a coastline
Backshore Foreshore Inshore Offshore Nearshore
Where is the backshore
The area between the high water mark (HWM) and the landward limit of marine activity.
When does changes to the backshore usually take place
Only during storm activity
Where is the foreshore
The area lying between the HWM and the low water mark (LWM).
What is the most important zone for marine processes in times that are not influenced by storm activity
Foreshore
Where is the inshore
The area between the LWM and the point where waves cease to have any influence on the land beneath them
Where is offshore
The area behind the point where waves cease to impact upon the seabed and in which activity is limited to deposition of sediments
Where is the nearshore
The area extending seaward from the HWM to the area where waves begin to break and no longer have an effect on the land beneath them
What 3 zones are included in the nearshore
Swash zone.
Surf zones.
Breaker zone.
What is the swash zone
The area where a turbulent layer of water washes up the beach following the breaking of a wave
What is the surf zone
The area between the point where waves break, forming a foamy, bubbly surface, and where the waves then move up the beach as swash in the swash zone
What is the breakerzone
The area where waves approaching the coastline begin to break, usually where the water depth is 5 to 10m
What does using a systems approach help to explain in a coastal landscape
Variations and changes that occur along a coastline. It also helps us to predict the possible consequences of natural processes or proposed human interventions. This can help us to foresee positive or negative impacts and plan for them
What is the coastline of England and Wales divided into
Eleven sediment cells where each cell can be seen as a system in which there are clear inputs (e.g from rivers), transfers of sediment (e.g longshore drifts), stores (beaches and spits) and transfers to the deep ocean
If changes occur in a a sediment cell what may it lead to
Feedback, either positive or negative
How can cliff erosion in a sediment cell lead to negative feedback
Cliff erosion leads to slumping, the mass of scree at the bottom of the cliff will, until it’s removed by wave action, protect the base of the cliff from further retreat. Here changes within the system reduces the causes of further disruption (dampening down the change)
What is scree
Collapsed cliff material at the base of the cliff
How can a spit create positive feedback
If a spit extends across a river estuary, reducing river velocity due to greater friction, this may lead to further spit growth and so yet further reduction in river velocity
Why are the sediment cells closed systems
Within each cell sediment is largely recycled, maintaining a state of relative balance and are, as such, closed sediment systems
What can coastal systems be seen operating at
Various scales
What will happen to a beach if inputs of sediment exceed outputs
The beach will extend in height, length and/or width
If we consider a single beach within its larger sediment cell, what can we observe
That if the beach experiences a positive sediment budget then somewhere else in the wider cell must be experiencing a sediment loss for the overall balance to be the same
By tracking the changes in the movement of sediment, what can we get a better understanding of
The connections within the system
While generally sediment cells are seen as closed systems, what is the reality
There is a slight loss of sediment to outputs beyond the system
Example of sediment being an output from a sediment cell
If wave enemy is very high or currents very strong, then sediment may be transferred to neighbouring cells, be ‘lost’ to deeper sea areas off-shore or be transferred to stores beyond the active coastal zone, such as upper beaches, coastal dunes and mudflats
What is a sediment sink
When sediment is permanently lost to the system, the destinations are known as sediment sinks
What do the conditions in each zone on a beach depend on
Factors such as tides, wave action and the depth of the sea
What are the 11 sediment cells
St Abb's head - Flamborough head Flamborough head - the wash The wash - river Thames River Thames - Selsey ball Selsey ball - Portland bill Portland bill - lands end Lands end - river Severn River Severn - st David's head St David's head - bardsey sound Bardsey sound - great orme Great orme - solway firth
What are many coastal features created by
The action of wind, waves, tides and sea currents
What is erosion
The wearing away of the earths surface by the action of ice, wind and water
What is weathering
The breakdown or decay of rock at or near the the earths surface in situ. Rock fragments will remain until they are removed by erosion processes. Weathering can be mechanical, biological or chemical
What is mass movement
The movement of material downhill by gravity and often assisted by rainfall
At the coast what is the main form of energy
Waves
What 3 things produce waves
Tectonic activity
Underwater landslides
Wind
What is wind
The movement of air from one place to another. Air moves from areas of high atmospheric pressure to areas of low atmospheric pressure. This movement is known as wind
What does the greater the pressure gradient between two places mean
The stronger the wind
What does prevailing wind mean
The most usual
In the UK, what is the prevailing wind direction
From the south-west
Before reaching our coasts, what have the prevailing winds blown over
The broad expanse of the Atlantic Ocean - this means it has blown over 3000 miles of open
What is the fetch
The distance which the wind blows over before reaching the coast
What are the 3 factors affecting wave energy
Fetch
Strength
And duration of wind
What leads to the formation of waves
As wind blows over the surface of the sea frictional drag leads to a transfer of energy and the formation of waves
How is wind an agent of erosion
As it can pick up and remove sediment (e.g sand) from the coast and then use it to erode other features
What is the most common type of wind erosion
Abrasion
Why is wind an important agent of moving sediment along the coast or further inland and beyond the shoreline
Becsuse it can pick up and move material
Once waves have been created by the wind, what do they become
The main agent that shapes the coastline
What can waves breaking at the coast do depending on their characteristics
Build up beaches or remove material
Why do waves break
Waves start out at sea and have a circular orbit.
As waves approach the shore friction slows the base of the wave.
This causes the orbit to become elliptical.
Until the top of the wave breaks over.
What are the characteristics of waves
Wave height - this is the height of the difference between a wave crest and the neighbouring trough
Wave length or amplitude - this is the distance between successive crests
Wave frequency or wave period - this is the time for one wave to travel the distance of one wave length, or the time between one fresh and the following fresh passing a fixed point
What is backwash
The action of water receding back down a beach towards the sea
What is swash
The rush of water up the beach after a wave breaks
What does the sea bed act as for waves
A source of friction as it is rough
What are constructive waves
Waves with a low wave height, but with a long wave length and low frequency of around 6-8/min. Their swash tends to be more powerful than their backwash and as a consequence beach material is built up.
What are destructive waves
Waves with a high wave height with a steep form and high frequency (10-14/min). Their swash is generally weaker than their backwash, so more sediment is removed than is added
How do constructive waves add to beach deposition
Their swash pushes more material from offshore up the beach than the backwash removed
Where is most of the energy in constructive waves used
In forward movement up the beach rather than flowing back down the beach and much water is lost percolation
As backwash is reduced in constructive waves, what happens to the following swash
It is less impeded in its movement up the beach
What are constructive waves associated with
A gentle beach profile, although over time they will build up the beach and make is steeper.
Why do constructive waves rarely reach the foot of the cliff
Because the wave energy is absorbed by the beach
Why do destructive waves mean beach material is easier to remove
As they crash down they loosen beach material
Why is the swash of destructive waves short lived
As energy has gone into a more vertical impact
What is the net effect of destructive waves
The removal of beach material along the shoreline
What does the strength of the backwash of destructive waves do
Takes material down the beach and impedes the next swash
What are most beaches subject to an alternating cycle of
Constructive and destructive waves e.g constructive waves build up a beech resulting in a steeper beach profile which encourages destructive waves
What landform is associated with constructive waves
Berms
What landform is associated with destructive waves
Storm berms
Example of negative feedback because of waves
Constructive waves operate to build up a beach, eventually the beach profile steepens which can encourage destructive waves (plunging rather than surging) which then remove material from the beach and deposit it offshore. This, in turn, can result in the beach profile becoming less steep again, encouraging constructive rather than destructive waves to form. All things being equal, this will continue until a state of dynamic equilibrium is reached
What happens when waves approach a coastline that is indented
They are refracted and become increasingly parallel to the coastline.
Around headlands, why do waves have greater energy to erode
Waves tend to break and have higher frequency, wave height and steepness, which gives them greater energy
How does wave refraction occur on a headland
waves approaching the headland meet shallower water first, while the part of the wave approaching the bay is still in deeper water. Friction with the sea floor slows the headland approaching waves and causes their frequency to increase.
In bays what leads to a constructive impact of waves
The waves spread out and become less frequent which leads to a reduction in wave energy
What is the overall effect of wave refraction
Wave energy becomes concentrated on the headland. It accounts for the presence of erosive features of headlands and deposition features in bays
In theory, how would continued erosion of the headland and deposition in the bay’s result in a state of equilibrium
The shape of the coastline would remain static due to a balance between the potential erodibility of the rocks and the effects of wave refraction (in reality though conditions rarely remain stable enough for long enough for this to happen)
What is a current
Refers to the permanent or seasonal movement of surface water in the seas and oceans.
What are the three types of currents
Longshore currents (sometimes known as littoral currents)
Rip currents
Upwelling
Why do longshore currents occur
Because most waves approach the coastline at an angle. The result is a flow of water (current) running parallel to the shoreline. This moves water and transports sediment parallel to the shoreline
What are rip currents
Strong localised underwater currents that occur on some beaches and move water away from the shoreline.
How do rip currents form
They develop when a series of plunging waves cause a temporary build up of water at the top of the beach. Met with resistance from the breaking waves, water returning down the beach (the backwash) is forced just below the surface following troughs in the beach profile. The fast-flowing offshore surge of water can be hazardous to swimmers
What is upwelling
The movement of cold water from deep in the ocean towards the surface
How does upwelling occur
The dense cold water replaces warmer surface water and creates nutrient rich cold ocean currents. These currents form part of the pattern of global ocean circulation currents
What is wave refraction
When waves approach a coastline that is not regular shape, they are refracted and become increasingly parallel to the coastline. The overall effect is that wave energy becomes concentrated on the headlands, causing greater erosion. The low-energy waves spill into the bay, resulting in beach deposition
What is longshore or littoral drift
When waves approach the short at an angle and swash and backwash then transport material along the coast in the direction of the prevailing wind and waves
What are tides
What’s in the water levels of seas and oceans caused by the gravitational pill (another source of energy) of the moon and, to a less extent, the sun
What creates a high tide
The moon pulls water towards it, creating a high tide, and there is a compensatory bulge on the other side of the earth. In areas of the world between these two bulge the tide is at its lowest
What are the 3 classifications of tidal range
Macrotidal - more than 4m
Mesotidal - 2-4m
Microtidal - less than 2m
What tides does the UK coastline experience each day
2 high tides and 2 low tides
What is the tidal range
The relative difference in height between low and high tides
What do tidal ranges determine
The upper and lower limits of erosion and deposition and the amount of time each day that the littoral zone is exposed to weathering
What is the tidal range affected by
The relative position of the sun and the moon
How are Spring tides formed
Twice in a lunar moon when the moon, sun and earth are in a straight line so the tide raising force is strongest
How are neap tides formed
Twice a month, the moon and sun are positioned at 90* to each other in relation to the earth. This alignment gives the lowest monthly tidal range
What do tidal ranges generate
Relatively prideful tidal currents which are an important source of energy
What are tidal currents important in
As they are particularly strong in estuaries and narrow channels, the currents are important in the transfer of sediment within the costal system or beyond (as an output)
When do tidal or storm surges occur
When meteorological conditions give rise to strong winds combine with high tides to produce much higher water levels than normal.
Example of a place tidal or storm surges occur and why
in the North Sea when intense low pressure weather systems (depressions) have the effect of rising sea levels. The sea level can rise by about 1 centimetre for every 1 millibar drop in pressure. Strong winds drive waves ahead of the storm, pushing the sea water towards the coastline. This has the effect of piling water up against the coast. The shape of the North Sea means that as sore S move south water is funnelled into a narrowing channel.
What intensifies the effect of storm surges
Spring tides
What is a high energy coast
A coastline where strong, steady prevailing winds create high energy waves and the rate of erosion is greater than the rate of deposition
What is a low energy coast
A coastline where wave energy is low and the rate of deposition often exceeds runs rate of erosion of sediment
What is a sediment cell
A distinct area of coastline seperated from other areas by well-defined boundaries, such as headlands and stretches of deep water
Characteristics of high energy coastlines
Consistently strong waves.
Strong, steady prevailing winds with long fetch to create high energy waves.
Rate of erosion is greater than rate of deposition.
Net transfer of material from coastline to sea.
Erosion landforms like headlands and bays found here.
In the UK where are high-energy coastlines found
Along stretches of the Atlantic-facing coat, such as Cornwall or North-west Scotland
Characteristics of low energy coastline
Waves are less powerful.
Rate of deposition is greater than the rate of erosion.
Wave energy is low.
Typical landforms include beaches and spits.
More likely to be in a state of equilibrium.
In the UK where are low-energy coastlines found
Lincolnshire
Why are low energy coastlines likely to be in a state of stable equilibrium
Because they have key inputs, transfers and outputs in balance
Globally, where does most sediment come from
Rivers, streams and coastal erosion, although there are local variations
What are 6sources of sediment
Rivers Cliff erosion Longshore drift Wind Offshore Storm surges
How are rivers a source of sediment
Sediment is transported in rivers and is deposited in river mouths and estuaries where it is then reworked by waves, tides and currents. Most coastal sediment originates from rivers
When is cliff erosion particularly an important source of sediment
This can be particularly important along stretches of coastline where rocks are soft.
Example of cliff erosion being an important source of sediment
One example in the Holderness Coast where glacial fill forms unstable cliffs of Boulder clay.
How is longshore drift a source of sediment
Sediment is transported from one stretch of coastline (as an output) to another stretch of coastline (an an input)
How is wind a source of sediment
In glacial or arid regions, wind blow sand can be deposited in coastal regions. Sand dunes can act as both a sink and source of sediment (sand)
How is offshore a source of sediment
Sediment from offshore csn be transferred into the coastal (littoral) zone by waves, tides and currents.
How did the Chesil Beach in Dorset form
Sea levels rose at the end of the last glacial period, resulting in a considerable amount of coarse sediment being bulldozed onto the south coast of England.
What can sediment cells be divided into
Smaller sub-cells such as the cell 2 on the east coast of England, which stretches from Flamborough Head to the Wash has a sub-cell within it that stretches from Flamborough Head to the mouth of the Humber Estuary
What is a sediment budget
The balance between sediment being added to and removed from a sediment cell costal system
What leads to a positive budget or a surplus of sediment and causes the shoreline to build towards the sea
If more material is added to the sediment cell than is removed then there is a net accretion of material
What results in a negstive budget or deficit of sediment and causes the shoreline to retreat land wards
If more material is removed from the cell than is added
In principle, what does the sediment budget seek to achieve
A state of dynamic equilibrium where erosion and deposition are balanced
What can upset the balance of a sediment budget in dynamic equilibrium
Events such as an increase in river sediment as a result of a food. This, in turn, leads to deposition in the river estuary. A severe storm might also upset the balance by eroding a beach and transferring sediment outside the system
What does calculating the sediment budget for a cell require
The identification of all sediment sources and sinks and an estimation of the amount of sediment added and removed each year. Calculating the budget is extremely difficult and relies on the use of complex models and estimations
What are processes
The ‘how’ and ‘why’ of change in a system. They are the mechanisms that operate on the inputs and results in particular outputs.
What two sets of geomorphological processes are coastlines affected by
Marine processes
Sub-aerial processes
What are marine processes
These operate upon the coastlines that are connected with the sea, such as waves, tides and ,offshore drift
What are sub-aerial processes
These include processes that slowly break down the coastline, weaken the underlying rocks and allow sudden movement or erosion to happen more easily. Material is broken down in situ, remaining in or near its original position. These processes may affect the shape of the coastline, and include weathering, mass movement and run-off
What do all processes do to create a wide range of uniquely coastal landscapes
Interact
How much energy can waves generate as they break against the foot of a cliff
25-30 tonnes m^-2
In 2014, what happened in Dawlish
A particularly powerful storm hit Dawlish and destroyed part of the sea wall and a section of rail track cutting the rail connection between Devon and Cornwall for months. This storm altered the Devon coastline as large a,punts of sediment were swept away from beaches and sand dunes at Dawlish Warren (spit) were severely eroded.
How does coastal erosion play a key role in the coastal system
By removing debris from the foot of cliffs and provides an important input into coastal sediment cells
In reality, what do the processes of marine erosion do
Work together to erode a stretch of coastline
What are the 5 types of marine erosion
Hydraulic action Wave quarrying Abrasion Attrition Solution
What is wave quarrying
When waves break against a rock face with joints facing the wave, air inside the joints is highly compressed, creating enormous pressure within the fissure. As the water pulls back, there is an explosive effect of the air under pressure being released. The overall effect of this over time is to weaken the cliff face and storms may then remove large chunks of it.
What is wave quarrying sometimes known as
Cavitation
What is hydraulic action
The impact on rocks of the sheer force of water itself (without debris). This can exert enormous pressure upon a rock surface, weakening it and dislodging pieces.
What is abrasion
The material that the sea picks up also wears away rock rocks. As waves advance, they pick up sand and pebbles from the seabed. When they break at the foot of the cliff, the transported material is hurled at the base of the cliff - chipping away at the rock.
What is solution
Some calcium-based rocks such as chalk and limestone, is readily soluble and dissolved minerals can then be removed in solution. This process is very similar to a type of weathering called carbonation.
What is attrition
Whilst attrition doesnt directly alter the shape of the coastline it does result in a wearing away of rock participles. Angular rock fragments are smoothed and reduced in size forming pebbles, shingle and sand. This occurs due to friction as particles are rolled over each other by the action of waves and currents.
What are the 7 factors that affect the rate of coastal erosion along any stretch of coastline
Waves Fetch Sea depth Shape of the coastline Beach presence Human activity Geology
How do waves affect the rate of coastal erosion
Steeper high-energy waves have a greater erosive power than low energy waves. The point at which the wave breaks is important too. Waves that break at the foot of a cliff release more energy than those that break off-shore.
How does fetch affect the rate of coastal erosion
A wave that has built up over s greater distance will have generated more energy
How does sea depth affect the rate of coastal erosion
A steeply-shelving sea bed will create higher and steeper waves
How does the shape of the coastline affect the rate of coastal erosion
Headlands attract wave energy through refraction
How does the beach profile affect the rate of coastal erosion
Beaches absorb wave energy and provide some protection against erosion. Steep, narrow beaches are effective at dissipating energy from flatter waves. Flatter, wider beaches spread out incoming wave energy and are better at dissipating high waves. Shingle beaches absorb the impact of steel waves as well due to energy being dissipated through friction
How does human activity affect the rate of coastal erosion
Beach material (sand and shingle) is removed from some coastlines leading to an increase in erosion. In other areas coastal protection may reduce the rate of erosion C
How does geology affect the rate of coastal erosion
Perhaps the most important factor in determining the nature of the erosion all processes. It includes lithology, structure and dip
What is lithology
The physical strength and chemistry of rocks
What is structure of a coastline
The variation and arrangement of rocks along a coastline
How does lithology affect the rate of coastal erosion
Some rocks, like granite are very resistant to erosion whist others, such as clay are very vulnerable. Some rocks, like limestone, are well-jointed and cracked, which means that the sea can penetrate along lines or weakness, making them more vulnerable to erosion
Example of lithology determining erosion
Granite at lands end has been eroded by 10cm while Boulder clay at the Holderness Coast has been eroded by 120cm in the last century
How does structure affect the rate of coastal erosion
Along some coastlines rocks lie parallel to the coast (concordant coastline) whereas in some areas rocks lie perpendicular (discordant)
What is dip
Where cliffs have horizontal strata/bedding planes they may dip or slope
How does dip affect the rate of coastal erosion
When rocks dip inland steeper cliffs may form. Where rocks dip towards the coasts, cliffs tend to produce more gently sloping features
What are concordant coastlines sometimes called
Pacific e.g Dorset
What are discordant coastlines sometimes called
Atlantic
How do coves form
Along a concordant coastline, a resistant rock like limestone can protect the coastline from erosion, only allowing the sea to break through in a few places. Where the sea does break through it can more readily excavate the clay behind to form a cove e.g Lulworth Cove
Which coastline has examples of both concordant and discordant coastlines
The southern coast
What can wave and tidal energy that is not used for erosion of lost through friction be used for
Transportation
What does transportation represent
A significant transfer/flow of material is controlled and determined by the power of the waves
What does transportation of material by seawater depend on
The size and weight of the material and the energy of the transporting flow
What are the 4 types of transportation
Traction
Saltation
Suspension
Solution
What is traction
Large stones and boulders are rolled along the sea bed and beach by moving sea water. They are too heavy to be picked up and carried and will only move if energy level are high enough
What is saltation
Small stones bounce along the seabed and beach. This process is also associated with high energy conditions. As the particles land they may dislodge others.
What is suspension
Very small particles of sand and silt are carried along by the moving water, within the flow. Suspension is most likely when flow is turbulent. Large amounts of suspended load, especially near estuaries, can cause a murky appearance of the sea
What is solution
Dissolved materials are transported within the mass of moving water. This form of transportation plays an important role in the carbon cycle, transferring and depositing carbon in the oceans.
Describe the process of longshore drift
Swash transports material up the beach whilst backwash removes it back down the beach.
When the wind direction is oblique to the shore, swash rushes up the beach in the same direction as the wind, and so carries material up the beach at an angle.
The backwash then pulls material down the beach at right angles to the shore (due to the force of gravity).
The net effect of this is a zigzag movement of sediment up and down the beach.
What is longshore drift response for
Transferring vast amounts of sediment along the coastline and eventually out to sea.
What happens if the process of longshore drift is interrupted by coastal managment
It can lead to distortions of natural patterns
How do offshore currents, including rip currents, move material out to sea
At right angles to the shore. The material they transport is usually deposited some distance from the shore to form sand banks
When does deposition take place
When the velocity of the water or wind falls below a critical value for a particular size of particle and can no longer be transported. It occurs once the energy flow that is moving material declines
What are the four reasons deposition occurs
Currents may weaken or prevailing winds may lighten in strength altering the energy source.
Where opposing currents meet, turbulence may occur, resulting in deposition below the surface. Can happen at end of spit.
As waves move over the seabed or shore land features, friction occurs which results in deposition of heavy particles.
Where rivers or land slips add additional sediment to the sea deposition may occur, as energy is insufficient to transport the additional load.
What are areas of deposition like beaches, spits, mudflats, sand dunes and offshore bars classed as
Sediment stores or ‘sinks’
What do aeolian processes relate to
Wind
What does wind play an important role in shaping
The coastline
How does aeolian deposition occur
During the day, wind fends to be on-shore, as the sea is usually colder than land. When there is a large tidal range, large amounts of sand may be exposed at low tide. This provides a supply of sediment that can be picked up and transported by the wind. Sand is most likely to be carried by the wind and is usually transported close to the ground and over relatively short distances.
What are sub-aerial processes
Land-based and include weathering and mass movement
What are the links to the carbon cycle and water cycle during the process of weathering
Freeze-thaw weathering and carbonation
Why are weathering processes common at the coast
Due to the presence of air and water, cycles of wetting and drying and exposed rock surfaces.
What are the three main categories of weathering
Mechanical/physical
Biological
Chemical
What does mechanical/physical weathering involve
The break up of rocks without any chemical changes taking place
What are two examples of mechanical weathering
Freeze-thaw (frost shattering)
Wetting and drying
Where is freeze-thaw weathering common
In latitudes where temperatures fluctuate above and below freezing and there is a ready supply of water
How does freeze-thaw weathering occur
Water enters cracks in the rocks and freezes when the temperature drops below 0*C.
As it freezes, water expands by almost 10%, meaning ice occupies more space and so exerts pressure on the surrounding rock.
With repeated freezing and thawing, fragments of rock break away and collect at the base of the cliff as scree.
What is scree used by the sea to do
Aid erosion processes such as abrasion
