P1. Section C Flashcards
Give 9 features of constructive waves
- have little energy
- build the beach up
- have strong swash which pushes material up the beach
- lower height
- causes deposition
- created by the wind
- rushed back out to the sea under the force of gravity
- Constructive waves have a longer wavelength than destructive waves which means individual waves are spread quite far apart.
- Constructive waves have a low frequency (about 7-10 waves arrive at the beach each minute).
Give features of destructive waves
- have lots of energy
- have strong backwash because they have plenty of energy left
- Destructive waves cause most of the erosion of coastlines.
- Destructive waves have a stronger backwash than swash, meaning they drag more material away from the coastline than is deposited on the shore. it
- taller height
- created by the wind
- rushed back out to the sea under the force of gravity
- Destructive waves have a high frequency. They have around 10-15 waves per minute.
which type of waves are dominant in winter time?
destructive waves
What are the 4 main processes of erosion?
- hydraulic action
- abrasion
- attrition
- solution
what is hydraulic action?
waves crash against rock and compress the air in the cracks. This puts more pressure on the rock. Repeated compression widens the cracks and causes bits of rock to break off.
what is abrasion?
when eroded particles in the water scrape and rub against rock, removing small pieces
what is attrition?
eroded particles in the water collide, break into smaller pieces becoming more smaller, rounder and smoother
what is solution?
soluble materials (e.g limestone) dissolve in the water and are carried along
What is erosion?
the wearing away and removal of material by a moving force (e.g a wave)
What is weathering?
wearing away of rock in situ (staying still)
What are the 3 types of weathering?
- mechanical
- chemical
- biological
what is mechanical weathering?
the disintegration (breakdown) of rocks without changing its chemical composition
what is chemical weathering?
the disintegration (breakdown) of rocks by changing its chemical composition
what is biological weathering?
weathering due to the actions of flora and fauna.
Explain the process of freeze - thaw (mechanical weathering)
- water enter the cracks of rocks
- when the water freezes it expands, which puts pressure on the rock
- when the water thaws (melts) it contracts, which releases the pressure on the rock
- repeated freezing and thawing widens the cracks and causes the rock to break up
Explain the process of Carbonation (chemical weathering)
- Rainwater has CO2 dissolved in it, which makes it a weak carbonic acid .
- Carbonic acid reacts with rock that contains calcium carbonate
3, so the rocks are dissolved by rainwater
What are the 4 types of transportation?
- Traction
- Saltation
- Suspension
- Solution
what is traction?
large particles like boulders are pushed along the sea bed by the force of the water
what is saltation?
smaller pebbles bounce along the seabed by the force of the water
what is suspension?
small particles e.g clay and sand flow are carried along the water, not touching the seabed
what is solution?
soluble materials (e.g limestone) dissolve in the water and are carried along
what is a headland?
resistant rock that protrudes in to the sea
what is a bay?
less resistant rock that has eroded/ retreated back in to the coast
what is concordant coastline?
are made up of alternating bands of hard and soft rock that are parallel to the coast
what is discordant coastline?
are made up of alternating bands of hard and soft rock at right angles to the coast
n.d Explain the formation of headlands and bays.
n.d Explain how a stump is formed?
What is mass movement?
the downward movement of sliding material under the influence of gravity
- causes coasts to retreat rapidly
when is mass movement most likely to happen?
when the material is full of water which acts as a lubricant and makes the material heavier
what are the 4 types of mass movements?
- rock fall
- landslide
- mud slide
- slumping/ rotational slip
what causes mass movements?
Mass movements are caused by weathering, erosion, and gravity.
Small changes over time can mean that the centre of gravity of a cliff can hang over the sea, instead of over land making the cliff unstable and prone to mass movement.
what is rockfall?
when the cliff (materials) break and crumble down the cliff.
what is slumping?
when material moves down a slope at a curve.
what is mud slide?
when material moves down a slope in a straight line.
what is permeable / impermeable rock
permeable - water can infiltrate into the ground/soil
impermeable - water can’t infiltrate into the ground/soil
How are wave-cut platforms formed?
- Wave-cut notch is caused by erosion at the bottom of cliff, which causes it to become unstable and collapse.
- the collapsed material is wash away and a new wave - cut notch starts to form
- after repeated collapses the cliff retreats, leaving a wave - cut platform
WHERE are spits formed?
at sharp bends in the coastline, e.g at the river mouth
when does a bar form?
when a spit joins 2 headlands together
how are sand dunes formed?
when sand deposited by long shore drift is moved up the beach by wind
what is hard engineering?
using artifical structure to control natural processes such as flooding and erosion
- long term e.g 100 years
what are 4 hard engineering strategies?
- Sea wall
- Groynes
- Rock armour
- Gabions
what is a sea wall? what does it do?
a wall made out of hard material like concrete
- has a curved face to reflect the waves back into the sea
What are 2 advantages of sea wall?
- prevents erosion of the coast
- can act as a barrier to prevent flooding
what are 3 disadvantages of sea wall?
- looks unnatural - visual pollution
- expensive - £5000- £10,000 per metre
- high maintenance - creates a strong backwash that erodes under the wall
what are groynes? what does it do?
timber or rock structure built out to sea from the coast at right angles
- they trap sediment transported by long- shore drift and enlarge the beach
what are 3 advantages of groynes
- cheaper - £150,000 every 200m
- create wider beaches - which slows the waves –> gives protection from flooding and erosion
- attracts more tourists - provides useful structures for people interested in fishing
what are 2 disadvantages of groynes?
- visual pollution - unnatural, unattractive
- they make beaches narrower —> narrow beaches don’t protect the coast very well —> causing greater erosion
What is rock armour/ rip - rap ? what does it do?
boulders of rock that are piled up along the coast
- they force the waves to break, absorbing their energy
what are 3 advantages of rock armour?
- relatively cheap - £200,000 per 100 metres
- easy to maintain
- absorbs wave energy, reducing erosion
what are 2 disadvantages of rock armour?
- boulders can be moved around by strong waves so need to be replaced
- transportation of the rocks are expensive
what are gabions? what do they do?
a wall of wire cages filled with rocks usually built at the foot of cliffs
- absorb wave energy, reducing erosion
what are 3 advantages of gabions?
- absorb wave energy, reducing erosion
- cheap - £50,000 per 100 metres
- eventually become vegetated and merge into the landscape
what are 2 disadvantages of gabions?
- visual pollution
- wire cages corrode/rust over time (5-10 years)
what is soft engineering?
methods that work with natural processes to protect the coast
- are environmentally friendly
what are 3 soft engineering methods?
- beach nourishment
- dune regeneration
- dune fencing
what is beach nourishment? what does it do?
distribution of sand or shingle that’s added to the (upper part of the) beach
- the beach can absorb the wave energy and decrease it’s erosive power
what are 3 advantages of beach nourishment?
- blends in with existing beach so doesn’t cause visual pollution
- relatively cheap? - £500,000 per 100m
- creates a wider beach - attracts tourists
what are 3 disadvantages of beach nourishment?
- repeated maintenance is required
- expensive? - £500,000 per 100m
- taking material from the sea bed can kill organisms like sponges and corals
what is dune regeneration? what does it do?
when marram grass is planted to stabilise the dunes
- creates a barrier between land and sea and absorbs wave energy, preventing flooding and erosion
what are 2 advantages of dune regeneration?
- maintains a natural coastal environment –> popular with wildlife and people
- stabilisation is relatively cheap
what 4 are disadvantages of dune regeneration?
- protection is limited to a small area
- people don’t respond well to not being allowed near the marram grass
- can be damaged by storms
- time consuming to plant marram grass
what is dune fencing?
fences constructed on a sandy beach along the seaward face of existing dunes to encourage new dune formation.
- These new dunes help protect the existing ones
what are 2 advantages of dune fencing?
- minimal impacts on natural systems
- can control public access to protect other ecosystems
what are disadvantages of dune fencing?
- regular maintenance needed after storm
- visual pollution - especially if fences are broken
What is managed retreat?
removing coastal protection and allowing the sea to flood an area
What are 4 advantages of managed retreat?
- maintenance cost are very low (cheap)
- earth banks develop –> this build of sediment can absorb wave energy and decrease it’s erosive power
- salt marsh and vegetation develop providing natural protection from storms
- beaches can be naturally replenished due to erosion of the coast
what are 6 disadvantages of managed retreat?
- a certain amount of land will inevitably be lost while beaches are being built up
- settlements, farmlands and other property are destroyed
- schemes are extremely unpredictable
- very few of the managed retreat sites are being monitored consistently and effectively
- little evidence available on which to base future managed retreat projects
- it is not a socially acceptable plan and may invoke the need for compensation to land owners
What is the difference between lateral and vertical erosion?
Lateral erosion makes the river valley wider
Vertical erosion makes the river valley deeper
In which section of a river does vertical erosion dominate?
Upper course
