Coast KQ 1&2 Flashcards
What is a spilling wave ?
Steep waves breaking onto gently sloping beaches
What is a plunging wave ?
Moderately steep waves breaking onto steep beaches
what is a surging wave ?
Low angle waves breaking onto steep beaches
What is a swell wave ?
Long wavelength , wave period up to 20 seconds .formed in ocean oceans
What is a storm wave ?
Locally generated
Shorter wavelength , greater height , shorter wave period
What is the equation for the amount of energy in a wave ?
P= h^2 t
What is a system ?
A set of interrelated objects comprising of components and processes that are connected together to form a working unit
What energy types are available to a coastal landscape system ?
Kinetic , potential and thermal
What is an open system ?
Energy and matter can be transferred from neighbouring systems as an input but also as an output
What are some examples of inputs of a coastal landscape ?
Kinetic energy from wind and waves
Thermal energy from heat of sun
Potential energy from the position of material on sloped
Material from marine deposition
What are some examples of outputs of a coastal landscape ?
Marine and wind erosion
Evaporation
What are some examples of processes in a coastal landscape system ?
Longshore drift
When could equilibrium occur in a coastal landscape ?
When the rate at which sediment is bing added to the beach equal the rate at which sediment is being removed from the beach
What is dynamic equilibrium ?
When equilibrium is disturbed , the system undergoes self regulation and changes its form in order to restore equilibrium
What is a sediment cell ?
Reaches of shoreline which encompass th enter tidal and nearshore movement of sediment
Why are sediment cells closed systems ?
No sediment is transferred from one cell to another
How many large sediment cells are there around the coast of England and wales ?
11
How are the boundries of sediment cells determined ?
By the topography and shape of the coastline
Why is it unlikely that sediment cells are completely closed ?
Because of variations in wind direction and the presence of tidal currents
What is a special impact ?
From place to place
What is a temporal impact ?
Over time
What is the source of energy for coastal erosion and sediment transport ?
Wave action
How is wave energy generated ?
By the frictional drag of winds moving across the oceans surface
What are onshore winds ?
Blow from the sea towards the land , very effective at driving waves towards the coast
How does wind affect landforms ?
Helps to create constructive and destructive
Can make small landforms such as sand dunes and blowouts
How do waves link to energy ?
A wave posses potential energy as a result of its position above the wave trough, and kinetic energy caused by the motion of the water within the wave
What is the formula for the amount of energy in a wave in deep water ?
Power = height ^2 X time interval between wave crests
What is the wave period ?
Time interval between wave crests in seconds
What is wave frequency ?
The number of waves per minute
How do waves affect landforms ?
They deposit sediment for spits and beaches
Form wave cut notches
Discordant coastline could form due to increased erosion rates
What is negative feedback ?
When the process seeks to counter the change and maintain equilibrium
What is steady state equilibrium ?
Where variations in energy and the morphological response do nt deviate too far from the long term average
What is meta state equilibrium ?
Where an environment switches between two or more states f equilibrium
What is positive feedback ?
Where a flow/transfer leads to increase or growth
What are the features of constructive waves ?
Low height
Longer wavelength
Low frequency
6-8 per min
Strong swash
Weak backwash
Surging wave break
Deposition
What are th features of destructive waves ?
High height
Shorter wavelength
High frequency
12-14 per min
Weak swash
Strong backwash
Plunging wave break
EROSION
What is a sediment budget ?
The balance of the sediment volume entering and exiting a particular section of the coast
What is a swell wave ?
Long wavelength
Wave period of up to 20 seconds
Formed in open oceans
What is a storm wave ?
Locally generated
Shorter wavelength
Greater height
Shorter wave length
What is a tide ?
The periodic rise and fall of the sea surface and are produced by the gravitational pull of the moon and to a lesser extent the sun.
How do high tides form ?
The moon pulls water towards it ,creating a high tide , and there is a compensatory bulge on the opposite side of the earth
Where will there be a low tide ?
At locations between the two bulges
When will the highest tides occur ?
When the moon , sun and earth are all aligned and so the gravitational pull is at its strongest (this happens twice each lunar month and results in spring tides with a high tidal range )
How are neap tides produced ?
Twice a month , the moon and sun are a tight angles to each other and the gravitational pull is therefore at its weakness
This produces neap tides and low tidal range
What does tidal range influence ?
Where wave action occurs
Weathering process that happen on land exposed between tides
Potential scouring effect of waves along coasts with a high tidal range
How is the formation of sand dunes connected to tides ?
The larger the tidal range the more time the sand has to dry so when it is dry it can be blown up the beach to from sand dunes
How do tides affect landforms ?
Low tidal range = narrower beach which is prone to more erosion
What do tidal currents do ?
Move sediment to and from a beach and are much more consistent than rip currents
what is a neap tide ?
Lower than normal tides
Occur when the sun and moon are at right angles to the earth so the gravitational pull from both has a reduced impact
When do neap tides occur ?
Follows 7 days after a spring tide
What is a spring tide ?
Occurs when there’s a new or full moon
Happens twice per month
The tides on average are slightly larger than usual
How are rip currents caused ?
Either by tidal motion or by waves breaking at right angles to the shore
What is a rip current ?
Strong and relatively narrow currents of water that flow seaward against breaking waves
they are temporary
Some last for hours , some last for months
How are ocean currents generated ?
By the earths rotation and by convection
They are set in motion by the movement of winds across the waters surface
What do warm ocean currents do ?
Transfer heat energy from low latitudes towards the poles
What do cold ocean currents do ?
Move cold water from the polar regions towards the equator
They are driven. By offshore winds so have less effect on coastal landscapes
What coastal landforms do rip currents make ?
Remove sediment from the beach
Create sand bars , cusps and inshore gutters
How do warm ocean currents affect the landscape ?
They increase the rate of sub Ariel processes
Warmer the air , the faster the chemical and biological weathering
What does lithology mean ?
The physical and chemical composition of rocks
What does the structure of the rock mean ?
Properties of individual rock types such as jointing , bedding and faulting
What coastal processes are affected by geology ?
Lots of bedding planes and joints encourages weathering , erosion and mass movement
lithology affect erosion and weathering rates
How does geology affect coastal landforms ?
Affects cliff shape and gradient due to angle of strata
Resistant rock - arches , stacks , stumps
Less resistant rock - beaches , gentle slopes and cliffs
What are some stores in a coastal system ?
Dunes
Beaches
Sandbank
What are some inputs of the coastal system?
Cliff erosion
River sediment
Longshore drift
Wave deposition
What are the outputs of the coastal system ?
Aeolian erosion to inland
Longshore drift
Wave erosion
What is freeze thaw weathering ?
Water enters cracks/joints in rock, and freezes causing a 10% expansion.
This exerts pressure on the rock
Repeated freezing and thawing(to allow more water to enter ), eventually causes rocks to break
What is pressure release ? (also called dilation)
When overlying rocks are removed (due to weathering and erosion), the pressure is released , allowing rocks to expand and fracture parallel to the surface
What is thermal expansion ? (insulation weathering, or onion skin weathering )
Outer layers of rocks expand and contract when heated and cooled.repeated cycles of heating and cooling can cause the outer layers to crack and flake off
What is salt crystallisation ?
Saline water enters pore spaces or cracks in rocks
Water evaporates causing the salt to precipitate out forming crystals.
The growth of the crystals over time creates stresses within the rocks, leading to break up
Particularly effective with sodium sulphate and sodium carbonate around 26-28 degrees .
What are the 4 types of physical weathering ?
Freeze thaw
Pressure release
Thermal expansion
Salt crystallisation
What are the 5 types of chemical weathering ?
Oxidation
Carbonation
Solution
Hydrolysis
Hydration
What is oxidation ?
Some minerals in rocks (iron), react with oxygen , either in air or water
Causes rocks to crumble easily
What is carbonation ?
Weak carbonic acid is formed when rain reacts with CO2 in atmosphere
Th acid reacts with calcium carbonate in limestone and chalk creating calcium bicarbonate , which is soluble in water and therefore easily removed
What is solution (chemical weathering )?
Some minerals (gypsum), are soluble in water , so are relatively easily dissolved and removed by seawater
What is hydrolysis ?
Thi is the reaction between water and a group of rock minerals called silicates (e.g. feldspar found in granite reacts with water to form kaolin
What is hydration ?
Certain minerals react wth water creating new minerals of a larger volume
Other minerals , e.g. clay , expand when wet and contract when dry
Causing many rocks , e.g. shale to flake at their surface
What are the two types of biological weathering ?
Tree roots
Organic acids
What is tree root biological weathering ?
Tree roots grow into cracks in the rocks and exert outward pressure
Works in a similar way to freeze thaw
When trees fall , the roots can also exert leverage on the rock bringing them to the surface
This exposes them to further weathering
So rocks break apart
What is organic acids biological weathering ?
They are produced during decomposition of plant and animal litter
They case soil water to become more acidic and react with some minerals in a process called chelation
What does blue-green algae do to rocks ?(weathering )
Produces a shiny film of iron and manganese oxides on rocks
What do molluscs do on shore platforms ? (weathering )
May secrete acids which produce small surface hollows in the rock
What type of cliffs does rockfall occur on ?
cliffs of 40 degrees or more
If the cliff face is bare
What happens in rockfall ?
Rocks become detached from slope by physical weathering
Then fall off the foot of the cliff under gravity
What happens after rockfall occurs ?
Wave processes usually remove the material
Or
May accumulate as a relatively straight , lower angled scree slope
What is hydraulic action ?
When waves break against the cliff face
Air and water gets trapped in cracks and become compressed
As wave recedes the pressure is released , air and water suddenly expand and the crack is widened
What is the average pressure exerted by breaking Atlantic waves ?
11,000kg per m cubed
What is pounding ?
When mass of a breaking wave exerts a pressure on the rock causing it to weaken
How does hydraulic action affect the coastline ?
Happens in hard rock on a headland
Can form wave cut notches
How does abrasion affect the coastline ?
Form caves , arches , stacks and stumps
Hard rock on headland
Destructive waves
Requires high energy waves
How does attrition affect the coastline ?
Creates more sand and adds to the sediment budget
What is suspension ?
Small particles of sand , silt and clay can be carried by currents
This is why some sea water is muddy or brown
Larger particles can be carries in this way during storms
When does deposition occur?
Where rate of sediment accumulation exceeds the rate of removal
When wave slows down immediately after breaking
At the top of the swash - for a brief moment the water stops moving
During the backwash - when water percolates into beach material
In low energy environments
What is settling velocity ?
Velocity at which sediment particles are deposited
Give an example of a rockfall ?
White cliffs of Dover
March 2012
Area size of a football pitch fell
Rubble fell 300ft downwards
Give an example of a landslide ?
Lyme Regis
6th may 2008
Occurred after a long wet period during winter nad early spring
Mudslide
Give an example of slumping ?
Evans cliff , charmouth , uk
14th January 2006
17 people trapped
200,000 tonnes of mud toppled down
Where do rockfalls occur ?
On cliffs of 40 degrees or more
Especially if cliff face is bare
What is rockfall ?
Rapid free fall of rock from a steep cliff face
Rock fragments fall because of gravity and freeze thaw weathering
Where doo landslides occur ?
On cliffs previously weakened by weathering
What is landslide ?
Downhill movement of large amounts of rock,soil and mud
Heavy rain infiltrates soil and percolated down into rock
Has a straight slip plane
What type of slip plane does slumping have ?
Curved
Where does slumping occur ?
Common at clay cliffs , dry weather makes the clay crack allowing water to get into it
What is slumping ?
Material is rotated backwards into cliff face as it slips large pieces of rock are pulled downwards
How does a cove form ?
1)alternate bands of resistant and less resistant rock are laid paralelé to coastline
2)tectonic pressures cause fault in limestone
3)destructive waves attack fault , eventually limestone eroded through
4)less resistant sands and clays are rapidly eroded to form a cove
5)cove entrance narrows
Why do waves “bend”?
When they touch the seabed , friction causes the wave at the headland to slow down ,
What is an orthogonal ?
Imaginary lines which show the direction of the waves
They are at right angles to the wave crest
What effect do converging orthogonal have on the headlands ?
They bring concentrated erosion o the headlands
What happens to the orthogonal in the bay ?
They are less concentrated
The waves are spread out with less energy - deposition
S sediment builds up
What happens to horizontally bedded strata ?
Undercutting by wave action leads to rockfall
The cliff retreats inland
Parallel to the coast
What happens to seaward dipping strata ?
Undercutting by wave action removes basal support
Rock layers loosened by weathering slide into the sea along the bedding planes
What happens to landward dipping strata ?
Rocks loosened by weathering and wave action are difficult to dislodge
The slope profile is gradually lowered by mass movement and weathering
What is a spit ?
Long , narrow beaches of sand which are attached to land at one end and extend across the bay
What 3 pre conditions are required in the formation of a spit ?
Shallow water
Supply of sediment
Bend in coastline
What happens when the coast changes direction ?(spits)
Sediment keeps being deposited in the direction of the prevailing wind
Why does a spit hook ?
Prevailing wind or wave refraction changes direction
Or secondary wind direction can cause this too
What makes a spit permanent ?
Vegetation could grow and the roots fix sediment in place
Give 4 facts about spurn point ?
On the Huber estuary
Has a road running down it
Less than 10m wide in some places
Why are spits considered to being balance to a coastal system ?
Deposition which balances out erosion
Creates new land
How are headlands and bay in dynamic equilibrium ?
Erosion on headlands is counterbalanced by deposition in the bays
What is a geo ?
Narrow, steep side clefts within cliffs
What processes are included in the formation of a geo ?
Abrasion
Weathering
Biological weathering
What is an example of a geo ?
Huntsman leap
How is a geo formed ?
What is a blowhole ?
When pressure is in the rock so it explodes out the top
What are the processes involved in the formation of a blowhole ?
Pneumatic action
Hydraulic action
What is an example of a blowhole?
Blowhole in trevone , Cornwall
How does a blowhole form ?
May form via hydraulic action and pneumatic action of the waves crashing into the “ceiling” of the cave
Eroding upwards to the point where the land above collapses and falls through
How do high energy destructive waves affect beach profile ?
Strong backwash drags sediment down beach
Beach gets a flatter gradient
This means shallower water , more friction and less wave energy
How do low energy constructive waves affect beach profile ?
Strong swash adds more sediment onto beach
So beach gets steeper gradient
So deeper water , less friction and more wave energy
What is a salt marsh ?
Areas of periodically flooded low-lying coastal wetland that are found in sheltered areas behind spits
What are slat marshes a coastal habitat for ?
Plants , birds and animals
What is a mudflat ?
Flat , low lying areas of mud
What factors influence the rate of development of a salt marsh ?
Rates of deposition v rates of erosion
What is a floc ?
A mass of clay particles formed in a fluid by aggregation of suspended particles
What is flocculation ?
Causes the aggregation of minute clay particles into larger masses which are too heavy to remain suspended in the water
Why os flocculation important ?
It encourages deposition because the flocs are too heavy
What benefits do salt tolerant plants create within the salt marsh environment ?
They encourage deposition because they slow down the flow of water
Help to trap sediment
What are some slat tolerant plants found at salt marshes ?
Eelgrass
Cordgrass
What happens to species diversity as you move inland of the slat marsh ?
It increases as conditions are less harsh (salt content decreases )
What are creeks ?
Small streams that drain the marsh at low tide allowing water to drain back into the sea
What are saltpans ?
Flat area of ground covered with salt deposited by the evaporation of saline water
What conditions are required for salt marshes to form ?
No wind or waves
Good supply of sediment
Low lying flat coast
Clay in suspension , which leads to flocculation
Which of the 5 physical factors are important in salt marshes ?
Tidal currents - sweep sediment in
Tidal range - important as marsh form etween these
How do salt marshes form ?
What are beaches ?
Sloping areas of deposition between high and low water marks
Where does beach material come from ?
Cliff erosion - 5%
Offshore(combed from seabed, during periods of rising sea levels)- 5%
Rivers - 90%
What type of gradient beaches does sand and shingle cause ?
Sand - gentle
Shingle - steep
Why do sand beaches have a gentle gradient ? (Usually less than 5 degrees)
Small particle size so it becomes compact when wet , allowing little percolation during backwash
Little energy is lost to friction , and little volume lost to percolation , material is carried back down beach rather than being left at top
What is a ridge ?
Raised area of sediment running parallel to the shore
What is a runnel ?
Low trough (or dip)either side of a ridge .parallel to the shore
What is a breached ridge ?
Part of a ridge has been eroded away or broken through
What is a berm ?
Ridge at the back of a beach created from deposition
Found at the mean high tide mark
What is a storm ridge/beach ?
Ridge of larger cobbles and pebbles behind the berm that have been throw there by the storm waves
What is a cusp ?
Small semi circular depressions at the back of the beach formed by waves reaching the same point at the same time
why do shingle beaches have a steeper gradient ?
Saw ash is stronger than backwash so there is a net movement of shingle on shore
Shingle may make up the upper part of the beach where rapid percolation due to larger air spaces means that title backwash occurs and so materia is left at the top of beach
Why do you need a sheltered bay for a beach to form ?
Because the waves are calmer and constructive so they will deposit more material
Why do yo need constrictive waves to form a beach ?
They have a stronger swash than backwash so they deposit more sediment on the beach
How does waves affect the formation f a beach ?
Constructive waves = deposit material
How does wind affect the formation of a beach ?
Blows dry sand up the beach to form sand dunes
Why are beaches in equilibrium ?
Deposition and erosion are in balance with each other
What is a tómbolo ?
Beaches that connect the mainland to an offshore island
Often formed from spits that have continued until they Jin an island
Give an example of a tombolo ?
30km long shingle beach at Chelsie near Weymouth
What ae the three theories of how tombolos are formed ?
Wave reaction
Longshore drift
Seal level change
How does longshore drift form a tombolo ?
Carries material along the beach in a zig zag pattern
Swash comes in at a diagonal angle and backwash brings sediment back straight into sea
How does wave refraction form tombolos ?
Waves bend round island and sediment builds up
(ADD 111_
How does sea level change form a tombolo ?
In the past there were lower sea levels and low energy waves that have deposited material creating offshore bars
Constructive waves pushed this material back toward the shore building up a ridge that attaché to the mainland to the island
What is an offshore bar ?
Submerged or partly exposed ridges of sand that os built by waves parallel to the beach
What is an onshore bar ?
They can develop if a spit continues to grow across a cove or bay until it joins land at the other side
What forms behind a onshore bar ?
A lagoon or brackish water on the landward side
What will happen to this lagoon over time ?
Will gradually be infilled by deposition
What is an example of an onshore bar ?
100m wide bar , slapton snads , Devon
How could have slapton snads be formed ?
By post glacial sea rise
Onshore movement of sediment especially flint
What is a delta ?
Large areas of sediment found at the mouth of many rivers
How do deltas form ?
When rivers an tidal currents deposit sediment at a faster rate than waves and tides can remove it
What are the 4 requirements for a delta to form ?
Tidal ranges are low
Low energy environment
Rivers entering the sea are carrying large sediment loads
B-road continental shelf margin exists at the river mouth to provide a platform for sediment accumulation
What are the three parts of a delta ?
Upper delta plain
Lower delta plain
Submerged delta plain
What is the uppe delta plain?
Furtherst inland
Beyond the reach of tides
Composed entirely of river deposits
What is the lower delta plain ?
In the inter tidal zone
Regularly submerged
Composed of both river and marine deposits
What is the submerged delta plain ?
Lies below mean low water mark
Composed mainly of marine sediments
Represents the sea ward growth of the delta
How are deltas crisscrossed ?
By a branching network of distributaries
What is a distributary ?
Small branching stream channels that flow away from a main stream or river
What are the three types of delta ?
Cúlpate
Árcate
Birds foot
What is a cuspate delta ?
Pointed extension to the coastline occurs when sediment accumulates but this is shaped by regular , gentle currents from opposite directions
What is an arcuate delta ?
Sufficient sediment supply available for the delta to grow seawards , but wave action is strong nough to smooth and trim its leading edge
What is a birds foot delta ?
Distributaries build out from the coast in a branching pattern , with river sediment supply exceeding rates of removal by waves and currents
How do deltas and distributes form spits ?
Sediment that is deposited by distributaries at the river mouth forms promontories which are a source sediment for longshore drift
What is the case study for the low energy coastline ?
Nile delta , Egypt
Where do the summer prevailing winds come from in the Nile delta ?
From north west
How much of the time and what is the surface velovcity of prevailing wind ?
60% of the time with a surface velocity of up to 13.5 cm/s in summer
How does longshore drift affect the Nile delta ?
Moves sediment from the Rosetta distribritutary brought from the Nile along the delta eastwards
What creates many beaches west of Abu air head with crescentic bars ?
Perpendicular wave due to wind approaching the coast directly before the delta , resulting in no longshore drift but a strong rip currentwhich creates the beaches
Where does the winter prevailing wind come from and what percentage of the year ?
NE and 8%
When was Aswan dam built ?
1964
What did the Aswan dam distrust ?
The equilibrium of the delta system - erosion v accretion
What has the Aswan dam resulted in ?
Reduction in the amount of deposition from 120 millions t/yr to trace amounts
Leading to accelerated erosion rates of up to 148m/yr
How much is the meditteranean sea rising per year ?
1.2mm/yr which increases energy levels
Where do spits form on the Nile delta ?
East of Abu qir they grow parallel to the delta and extend across the nearshore enclosing sections of the coastline to form lagoons
How do lagoons form into slat marshes ?
They fill up with alluvial deposits
Due to the facts that lagoons are sheltered areas and low energy environment
What type of delta is the Nile delta ?
Arcuate
Where do distributaries start at the Nile Ella ?
At Cairo , 160km inland
What are the two main distributaries in the Nile delta ?
Rosetta and Damietta
Would would happen to the delta pre Aswan dam ?
It would flood every year to deposit silt , the depth of this alluvium is greater than 9m inn the delta
How long is the river Nile ?
6650km (largest in world)
What is the discharge of the river Nile ?
Low discharge
What is the sediment load of the river Nile ?
4.26t/ha/yr
Where does water in the river Nile originate from ?
From the Ethiopian summer monsoon rains
What will happen to the Nile delta if there is a 50cm increase in sea level
4 million people affected
1,800km squared of land submerged
What will happen to the Nile delta if there is a sea level rise of 1.5m ?
8 million people afffected
5,700 Kim squared of land submerged
How much will the sea level rise by 2100 (Nile delta )?
A 60 to 100cm rise
Name 3 landforms found east of Abu qir headland ?
Bars , spits , lagoons
What is the case study of a high energy coastline in the uk ?
Saltburn to flamborough head
Where do waves come fro and what is the fetch at subcell 1 d?
North and north east
Fetch over 1500km
At Whitby bay what are the wave heights like ? sub cell 1d
Can exceed 4m
Where is wave energy concentrated at subcell 1d ?
On exposed north facing parts like saltburn
Varied energy due to wave refraction creates varied erosion rates
What direction does longshore drift move sediment (saltburn - flamborough head )?
From north to south
What type of rocks are the north York moors made up of ?
Up to 400 m above sea level
Made up og sandstone , shale formed in Jurassic period but also some Carboniferous rock
Give some example of Carboniferous rocks on the north York moors ?
Coal measures
Millstone grit
Mountain limestone
What is the geology like at flamborough head ?
Large chalk headland and cliffs topped with till (glacial deposits )
What are the erosion rates of shale (weak) and clay ? (Flamborough head )
0.6 m per year
What is th erosion rates of sandstone (resistant ) and limestone ? (Sub cell 1 d)
Less than 0.1m per yr
What sediment cell is salt burn to flamborough head ?
Sediment cell 1 , sub cell 1d
What are the sources of sediment along slatburn to flamborough head ?
Cliff erosion
River elk (mouth at Whitby)
Nearshore deposits laid dow during ice age and being driven onshore as sea levels rise
Where does sediment mainly occur along subcell 1d ?
Filey brigg
How do tides affect the coastline at sub cell 1d ?
Weak and low tides result in deposition
Waves can attack a larger section of the cliffs
Give some examples of coastal landforms at subcell 1d ?
Over 50 geos facing the dominant wave direction
Blowholes north of selwicks bay
Green stacks pinnacle - stack
Why does the coastline of sub cell 1d have so few beaches ?
Deposits of sediment accumulate slowly acrosss coastline due to low input of sediment from rivers and slow erosion of rocks
Due to high energy waves from North Sea , sediment removed b4 it has chance to establish a developed beach
Give an example of a shore platform on sub cell 1d ?
Robin hoods bay
Wha is the height of chalk cliffs at flamborough head ?
20-30 m
