Coasts Flashcards
What causes waves?
Waves are caused by the action of the wind dragging over the surface of the water.
Fill in the blanks:
Waves are caused by the action of the_________ dragging over the surface of the water. The distance of water the wind blows over is called the___________. The______________ the wind has been blowing , the more ___________it has so the waves will be ___________ and more destructive so are likely to __________ the coastline. Waves with lots of energy are called_______________ waves and waves with little energy are______________waves. Constructive waves tend to ________________ material on the coast because they have little energy.
Larger Energy Longer Erode Destructive Deposit Wind Fetch Destructive Constructive
Waves are caused by the action of the WIND dragging over the surface of the water. The distance of water the wind blows over is called the FETCH. The LONGER the wind has been blowing, the more ENERGY it has so the waves will be LARGER and more destructive so are likely to ERODE the coastline. Waves with lots of energy are called DESTRUCTIVE waves and waves with little energy are CONSTRUCTIVE waves. Constructive waves tend to DEPOSIT material on the coast because they have little energy.
What effects the size of a wave, and its energy?
FETCH & LENGTH OF TIME THE WIND HAS BEEN BLOWING
The distance of water the wind blows over is called the fetch. The longer the wind has been blowing, the more energy it has so the waves will be larger and more destructive so are likely to erode the coastline. Waves with lots of energy are called destructive waves and waves with little energy are constructive waves. Constructive waves tend to deposit material on the coast because they have little energy.
What happens when waves approach a coastline?
Waves slow down due to friction with sea bed and start to stack up and increase in height
Base of wave is slowed so top is moving faster causing the wave to break.
Constructive wave
Low energy
Found in sheltered bays and spits
Creates sandy gently sloping beaches
Long wavelength, low frequency
Shallow Beach
Strong swash, weak backwash
Eliptical orbit
Destructive Wave
High energy
Found in exposed areas
More common in winter
Erodes coastlines and creates steep beaches
Short wavelength, high frequency, high wave height
Weak swash, strong backwash
Steep Beach
Circular orbit
What are the three processes that shape the coastline?
Erosion
Transportation
Deposition
Erosion
The wearing away of rocks and their removal. There are three types of coastal erosion – abrasion, hydraulic action and attrition. The more energy the waves have the greater the erosion.
Transportation
The movement of material carried by waves. It is moved in the water by traction, saltation, suspension and solution but along the coast by longshore drift.
Deposition
The laying down of material. Deposited material is called sediment.
Hydraulic action
Waves force water into cracks in the rock, this pressure breaks up the rock
Attrition
Chunks of rock get knocked together and worn into smaller pieces.
Abrasion
The waves throw sand, pebbles and large stones against the rock. They wear it away like sand paper.
What makes waves break?
Waves slow down due to friction with sea bed and start to stack up and increase in height
Base of wave is slowed so top is moving faster causing the wave to break.
2 types of waves
Constructive & destructive
How does the wave type affect the coastline?
Constructive - build beaches - flat, wide beaches
Destructive - erode - steeper beaches
Which wave has a strong backwash?
Destructive
What 3 processes does the sea do?
Erosion transportation and deposition
Name the 4 types of erosion
Hydraulic action, abrasion. Attrition and solution
This is the sheer power of the waves as they smash against the cliff. Air becomes trapped in the cracks in the rock and causes the rock to break apart.
Hydraulic action
This is when sediment in the water grinds along the cliffs, much like sandpaper. Over time the rock becomes smooth.
Abrasion
This is when rocks that the sea is carrying knock against each other. They break apart to become smaller and more rounded.
Attrition
This is when sea water dissolves certain types of rocks. In the UK, chalk and limestone cliffs are prone to this type of erosion
Solution
Where small pieces of shingle or large sand grains are bounced along the sea bed.
Saltation
Where pebbles and larger material are rolled along the sea bed.
Traction
4 types of transportation
Traction
Saltation
Suspension
Solution
Draw diagram of longshore drift
Your diagram must include the following labels:
Land
Sea
Direction of SWASH
Direction of BACKWASH
Prevailing wind
Wave crests
Direction of longshore drift
Erosion
The breaking down of rock and the removal of the rock
In deposition, what weight material is dropped off first?
Heaviest - requires the most amount of energy to be transported
The lighter the material the lower the velocity needed to transport it
Weathering
Breaking down of rock
Mass movement
The downward movement of rock or soil due to gravity. Caused by the weathering of rock and heavy rainfall.
Chemical weathering
The breakdown of rocks by changing the chemical composition E.g. carbonation - rainwater is a weak carbonic acid it dissolves rocks that contain calcium carbonate
Mechanical weathering
The breakdown of rocks without changing their chemical composition. E.g. freeze thaw weathering (frost shattering)
Chemical weathering e.g
E.g. carbonation - rainwater is a weak carbonic acid it dissolves rocks that contain calcium carbonate
Mechanical weathering e.g.
E.g. freeze thaw weathering (frost shattering)
Describe freeze-thaw
Water ends in a rock
Water freezes at night and expands by 9%, causing cracks and weaknesses
Process repeated, weathering rock until rock breaks apart
Sliding
The downhill movement of a large amount of rock, soil and mud.
Occurs on steep cliffs weakened by weathering.
Heavy rain infiltrates the soil and rock causing it to become heavier.
The heavier, saturated (full of water) mass falls in a straight line along a distinct slide plane.
E.g. Jurassic Coast, Dorset
Sliding e.g.
E.g. Jurassic Coast, Doset
Sliding diagram
https://docs.google.com/presentation/d/1_OABC7_1rWeip6GOIMR4gRloRa88EefTGOaatf4UcNo/edit#slide=id.p22
Slumping e.g.
E.g. Barton on sea,
Hampshire
Slumping
Rainwater soaks into the rock.
It becomes too heavy and starts to slide down on the cliff on a curved slip plane.
Loose material collects at bottom.
E.g. Barton on sea,
Hampshire
Slumping diagram
https://docs.google.com/presentation/d/1_OABC7_1rWeip6GOIMR4gRloRa88EefTGOaatf4UcNo/edit#slide=id.p22
Rock falls
Bare, well-jointed rocks (lines of weakness in rocks) are prone to mechanical weathering which results in falling rocks losing contact with the cliff face.
At the bottom of the cliff they fan out to form scree slopes.
E.g. A 300m section of the Jurassic Coast fell between Seatown and Eype Beach in April 2021
Rock falls e.g.
E.g. A 300m section of the Jurassic Coast fell between Seatown and Eype Beach in April 2021
Outline the characteristics of a destructive wave. (4 marks)
Must have two logical links
Backwash greater than swash (1) therefore beaches eroded (1)
High energy waves (1) due to greater fetch (1) so over higher than 1m (1)
Short wave length (1) so has a high frequency 10-14 per minute
Concordant
Rock types run parallel to the coast
Discordant
Rock types run perpendicular to the coast
Characteristic of a headland
Near vertical cliff face
High energy area affected by destructive waves
Hard rock jutting out into sea
Caves arches stacks and stumps can form
Characteristic of a bay
Crescent-shaped indentation in the coastline between two headlands
Soft rock e.g. sand or clay
Low-energy constructive waves
Characteristics of a wave cut platform
Gently sloping platform
Smoothed in place by abrasion
Deep cracks in places
Pitted appearance with small rock pools showing at low tide
Covered at high tide
Describe how a headland is eroded
As the wave approaches the coast it takes on the shape of the coastline.
Waves converge on the headland, concentrating more energy on the headland, increasing the rate of erosion.
Embryo dune
A newly formed sand dune closest to the sea
Embryo dune
A newly formed sand dune closest to the sea
Marram grass
A plant found in sand dunes that has long binding roots
Saltation
How sand is bounced along by the wind
Crest
The top of the sand dune
Water table
The upper horizontal limit of the wet sand
Dune slack
Where there is a trough or low point in a line of dunes
Leeward slope
The slope that faces away from the wind
Windward slope
The slope that faces the wind
Describe how sand dunes are formed
- Sand dunes are formed when sand is moved up the beach by the wind by saltation.
- Obstacles (driftwood) cause wind speeds to decrease so sand is deposited.
- This then builds up over time forming hummocks.
- The sand is then colonised by plants and grasses - this stabilises the sand and encourages more sand to accumulate there. Forming small dunes called embryo dunes
- Over time the oldest dunes migrate inland as newer embryo dunes are formed.
- These mature dunes can reach heights of up to 10 m
Why don’t bays erode much
Waves diverge in the bays so waves lose their energy and so deposit material. This forms a beach
CCASS
Large crack:
hydraulic action, or salt weathering
cave:
hydraulic action and abrasion
The cave becomes larger
waves converge
the headland is eroded.
caves may join:
arch
arch collapses
Stack
stack undercut & eroded
Stump
Physical reasons why management is needed on Holderness coast
(4)
NARROW BEACHES -so don’t stop the waves hitting the base of the cliffs at high tide
STRONG WAVES because Fetch of waves about 500-800km across the north sea.
SOFT ROCK - Boulder clay so less resistant to erosion
CLIMATE CHANGE is increasing the number of storms so more strong waves that erode the cliffs
Average erosion rate Holderness coast
It is one of the fastest eroding coastlines in Europe. Average erosion rate is 1.2m per year.
Human reasons management is needed
(4)
Tourist economy - creates jobs and wealth for the area
Large populations at Bridlington, Hornsea (8000), Withernsea and Mappleton
To protect the main road B1242 that connects these towns
Gas supply - ¼ of UK’s gas comes here
Management strategies on Holderness coast and where
(7 places)
Bridlington:
4.7km Sea wall
Hornsea:
Concrete sea wall, rock armour and wooden groynes
Mappleton:
2 Rock groynes
Aldbrough & Ringbrough:
Do nothing
Withernsea:
Rock armour and sea wall
Easington:
Rock armour
Spurn Head (nature reserve):
Managed retreat
Facts about conflict about coastal management on Holderness coast because of groynes
(2)
Erosion faster below Mappleton bc no LSD
(Great Cowden’s farm: 80,000m^2 farmland lost/year)
Less LSD
potential loss of important habitats at Spurn Head Nature Reserve
How much has been spent defending Easington gas terminal
£4.5m
What defends Easington gas terminal
rock armour
What is the rock type on the Holderness coast ?
Boulder clay
How large is the fetch on the Holderness coast ?
500-800km
What is the population of Hornsea?
8000
What is the name of the main road on Holderness coast near Hornsea
B1242
What percentage of the UK’s gas supplies come into Easington
25%
Climate change’s effect on erosion on Holderness coast
Increased erosion bc more storms so more desructive waves
How many houses in Mappleton
~50
1991 how much was spent on 2 rock groynes and a rock revetment to protect Mappleton
£2 million
1980 erosion rate in Mappleton
2m/year
August 2015
What happened in Mappleton
large crack appeared in the top of the cliff to the south of the defences
Since 1991, what has happened to the erosion rate of Mappleton
Increaced significantly
Beach south of Mappelton?
Little beach
