Theme 2 - 2.3 - Coasts Flashcards
Define abrasion (or corrasion).
Rocks been thrown into the cliffs by waves and breaking off bits of the cliff.
Define hydraulic action.
This is when sea water and air get trapped in cracks. The increasing pressure of the water and air cause the rocks to crack.
Define solution (or corrosion).
The removal of chemical ions, which causes rock to dissolve.
Define attrition.
When rocks in the sea hit against each other, wearing themselves down.
Define fringing reef.
A reef that grow outwards around an island.
Define barrier reef.
A reef that is separated from the coast by a deep channel.
Define atoll.
A circular reef enclosing a shallow lagoon.
Define weathering.
The breakdown of rocks in situ (in place).
Define erosion.
The breakdown and removal of rock, involving the movement of the material by water, ice or wind.
What are the three main categories of weathering?
- Chemical
- Biological
- Physical/Mechanical
Define chemical weathering.
The break down of rocks caused by a change in their chemical make-up.
Define biological weathering.
Biological weathering is when flora and fauna break down the rock - E.g. growing roots systems or burrowing animals
(Biological weathering is sometimes included within physical weathering)
Define physical weathering.
The break down of rock caused by physical processes with no change in the rock’s chemical make up.
Name some marine processes which occur in coastal zones.
- Wave action from constructive and destructive waves
- Wind action
- Mass movement and weathering
- River and ice actions
What are marine processes?
Processes operating at a coastline that are connected with the sea, such as waves, tides and long shore drift.
What are the features of destructive waves?
- Short wavelength
- High height (>1m)
- High frequency (10-12/min)
- Backwash is stronger than swash
What are the features of constructive waves?
- Long wavelength
- Low height (<1m)
- Low frequency (6-8/min)
- Swash is stronger than backwash
What are the 4 processes of transportation?
- Traction - Dragging particles along sea floor
- Saltation - Smaller particles are bounced along
- Suspension - Fine particles are held up
- Solution - Sediment is dissolved
What are some reasons why deposition happens?
- Decrease in wave energy or velocity
- Large supply of material
- Irregular, indented coastline
How are waves formed?
Friction from the atmosphere (wind) causes a circular orbit in the water, which creates waves.
What causes waves to break?
The friction at the bottom of the waves slows the bottom down, meaning the top travels faster and causes the wave to eventually break.
What factors affect the size of waves?
- Fetch size
- Wind speed
- Wind duration
Which waves have more energy, constructive or destructive?
Destructive
What is the swash?
The pushing of a wave up the beach.
What is the backwash?
The pulling of a wave back down the beach.
What does constructive mean?
When a wave deposits more sediment than it takes away, helping to build a beach up.
What does destructive mean?
When a wave deposits less sediment than it takes away, destroying a beach.
What are plunging breakers?
Breaking waves whose crest curls over and collapses suddenly.
What are surging breakers?
Breaking waves whose crest remains relatively unbroken as waves slide up and down the beach.
What is wave refraction?
When waves approach an area of irregular coastline, the shallowness of the water near some features increases friction and causes the waves to bend so that they’re perpendicular to the coastline. This usually concentrates energy on the flanks of headland and disperses the waves in bays.
What does incomplete refraction result in?
Long shore drift
What is longshore drift?
The process by which sediment is moved along a coastline.
Describe longshore drift.
- Waves approach the beach at an angle due to the prevailing wind
- The swash deposits material at that angle
- The backwash drags material back to the sea at right angles to the beach (due to gravity)
- The process repeats and sediment moves down the coastline
When do headlands and bays form?
When rocks are of different strengths.
How do headlands and bays form?
- Sections of soft rock are eroded quickly, whereas hard rock does not erode so easily
- This creates headlands of hard rock, between which there are bays of soft rock
How do cliffs, wave-cut notches and wave-cut platforms form?
- Maximum erosion of a cliff occurs at the foot of the cliff
- This creates a wave-cut notch
- Eventually, the rock overhanging this collapses
- This leaves a steep side, which is called a cliff
- The process repeats and this leaves a wave-cut platform beneath the wave level
What is a wave-cut notch?
An indentation in at the bottom of a cliff caused by erosion.
What is a wave-cut platform?
A long section of rock under the water surface left behind by a cliff which has been eroded.
Describe the formation of caves, arches and stacks.
- A weakness, such as a fault line, in some headland can be eroded to form a cave
- Eventually, the cave erodes the entire wave through the headland, creating an arch
- When this is widened enough the arch can collapse to leave a stack
- Finally, this stack collapses to leave behind a stump
Describe the formation of a spit and salt marsh.
- Longshore drift moves sediment along a coastline
- When the coastline suddenly changes direction and the water is shallow and shelter, sediment can be deposited and builds up
- This eventually results in a spit
- A hooked end may form due to a change in wind direction
- In the shelters area behind the spit, a salt marsh can form
Where is wave energy concentrated?
On headland - due to refraction.
What is a bay-head beach?
A beach that forms at the head (inner most part) of the bay. It does not extent to the headland, because erosion is too strong.
Describe the formation of a bay-head beach.
- As waves travel through a bay, they lose energy
- By the time they reach the far side of the bay, they do not have enough energy to carry their load
- This load is deposited and a beach forms
- Other factors, such as cliff erosion may help to provide sediment for the beach
What is a tombolo?
A ridge of sand (like a spit) joining the mainland to an island.
What is a bar?
A ridge of sand (like a spit) which joins two parts of headland, cutting off a bay.
Give an example of a spit.
Spurn Head - Holderness Coast
Describe the formation of a bar.
- A spit grows across a bay, until it joins another headland
- Behind the bar, a lagoon is created -> Water is trapped
- Eventually, this lagoon can become a salt marsh due to the unmoving water
Describe the formation of a tombolo.
• A spit grows out from some headland until it reaches an island.
What factors encourage the formation of a salt marsh?
- Calm weather
- Good sediment supply
- No human interference
- Steady sea level
- Correct climate
- Specific wave type
- Constant tidal regime
Give an example of a bar.
Slapton Sands - Devon
Give an example of a tombolo.
Chesil Beach -> Joins South Dorset to Isle of Portland
Give an example of a beach.
Dawkins Warren - Devon
Give an example of some cliffs.
Seven Sister - East Sussex Coast
Give an example of a bay.
Selwicks Bay - Flamborough
Give an example of a stack.
Old Harry Rocks - Dorset
Can be used for cave, arch, etc.
Give an example of a wave-cut platform.
Southerndown - Wales
What things are needed for the development of sand dunes?
- Plentiful supply of sand
- Strong winds
- An obstacle to trap sand
What are embryo dunes?
Starting form of sand dunes. They form in the sheltered area behind the berm and strand line.
What are foredunes?
Dunes formed when small embryo dunes join together.
What are yellow dunes?
When sea couch and marram grass begin to grow on the foredunes, they become more stable and grow. A humus later begins to develop, but the dune is still yellow for now.
What are grey dunes?
As a humus layer develops on yellow dunes, it turns them grey.
What are mature dunes?
As the humus layer develops, the dune can sustain more plants, flowers and even trees.
What are dune slacks?
As the dunes develop in size, water can collect between dunes. Marsh can grow there.
What are blowouts?
Depressions or holes in a dune caused by the wind.
What is humus?
A layer of decaying plant and animal matter that adds nutrients to the ground.
What is the berm?
A ridge that forms at the top of the beach.
Describe the order of dune formation.
- Embryo dune
- Fore dunes
- Yellow dune
- Grey dune
- Mature dune
What is the intertidal zone?
The area of land between high and low tide.
What is the strand line?
The material that is deposited by the sea at the furthest point of the high tide.
How are sand dunes formed (simple explanation)?
- Wind picks up sand and sediment
- An obstacle, such as grass, causes the sand to be deposited
- The sand builds up and forms a dune
- Growth of marram grass further traps sand
Give an example of some sand dunes.
Ynyslas Dunes, Dyfed
What are corals?
Mostly colonial organisms, made up of hundreds of individual organisms called polyps.
How do polyps form an exoskeleton?
They absorb calcium salts from the seawater and combine them with carbon dioxide to build a skeleton of calcium carbonate.
What conditions are needed for coral to grow?
- Water over 20*C
- Salt water
- Clear water
- Shallow, coastal water
- Good supply of water and plankton
- Sunlight
What are the three types of coral reef?
- Fringing reef
- Barrier reef
- Atolls
How do coral feed?
Polyps have a partnership with zooxanthellae (a type of algae):
• Zooxanthellae photosynthesise to produce sugar -> This is transferred to the polyps
• Polyps provide CO2 and protection for the algae
• Corals also catch zooplankton
• At night, polyps come out from exoskeletons and capture food floating by
Where do fringing reefs form?
Near coasts of islands and continents. They are separated from the land by a shallow lagoon.
Where do atolls form?
They form like fringing reefs, except afterwards the island in the centre sinks. A lagoon is left behind.
Where do barrier reefs form?
Further from the sea that atolls or fringing reefs. They are separated from land by a deep lagoon.
What are some threats to coral reefs?
- Destructive fishing -> Can physically break the reef apart
- Overfishing -> Can disrupt ecosystem
- Climate change -> Change in water temperature can cause coral to suffer
- Pollution -> Toxins can poison reefs or nitrogen can cause algae build up
- Coral mining
Why are coral reefs important?
- Fishing -> Corals are nurseries and habitats for many fish
- Coastal protection -> Coral reef reduce wave power and act as natural defences
- Tourism -> Brings in money
- Medicine -> Coral reef species are used in many medicines
What are mangrove swamps?
Salt-tolerant forests of trees and shrubs that grow in the tidal estuaries and coastal zones of topical areas.
How can coral reefs be managed?
- Encouraging eco-tourism
- Controlling fishing
- Improving water quality
- Education
- Introducing “Marine Protected Areas”
What conditions do mangroves need to grow?
- Low-oxygen soil
- Slow-moving water
- Warm water
- Salt water
Where is the world’s largest mangrove forest?
Sundarbans - Bangladesh
What is the value of mangrove swamps?
ECOLOGICAL + ENVIRONMENTAL • Habitat for wildlife species • Improve water quality HUMAN • Prevents coastal erosion + tsunami protection • Tourism • Fishing • Timber
What are some threats to mangrove swamps?
- Timber over-harvesting
- Clearing -> To make room for other things
- River changes e.g. Dams -> Change water amount/quality
- Destruction of coral reefs -> These provide a barrier before waves hit the mangroves
- Pollution -> Toxins kill animals + Oil can smother roots and plants
- Climate change -> Sea-level change affects mangroves
How can mangroves be managed?
- Education
- Growing mangroves in protected areas
- Reducing pollution
- Establishing farms to grow new mangroves + replanting damaged mangroves
What opportunities do coastal areas provide?
- Trade and commerce
- Tourism and recreation
- Fishing
- Energy developments (e.g. offshore wind farms)
What are the hazards of coastal areas?
- Erosion -> Loss of property
- Rising sea levels -> Loss of land + property
- Tropical storms and storm surges
- Tsunami events
What are hurricanes?
Intense tropical storms that bring heavy rainfall, strong winds and high waves, and cause other hazards such as flooding and mudslides.
What are the features of hurricanes?
- Develop as low-pressure systems over tropical oceans
- Have a calm central area, know as the eye, around which winds spiral rapidly
- Have a diameter of up to 800km
What are the conditions needed for a tropical storm to form?
- Minimum depth of 60m of water
- Large expanse of water e.g. Atlantic Ocean
- Warm water temperatures of over 27*C
- Latitude between 5 and 20 North or South of the equator
What happens to a hurricane once it passes over land?
It is starved of moisture and begins to lose strength.
Why is the impact of hurricanes smaller in HICs?
- Better access to satellite equipment
- Stricter regulations on buildings and better design
- More advanced emergency services
- More widespread insurance cover
- More training and evacuation drills
Where do most tsunamis happen?
Pacific Basin
Name a long-term risk of climate change.
Rising sea levels
Name a country at risk of rising sea levels.
Bangladesh
In coastal management, what is hard engineering?
The building of a physical structure, usually out of wood or concrete to protect the coast. It is usually expensive and ugly.
In coastal management, what is soft engineering?
Working with nature rather than physical structures. It is cheaper and more aesthetic, but it is weak.
What are the general advantages and disadvantages of hard engineering?
ADV. • Strong and effective DIS. • Expensive • Ugly • Can have unwanted side-effects
What are the general advantages and disadvantages of soft engineering?
ADV. • Cheaper • Aesthetic DIS. • Weak and ineffective
What are the three main ways of coastal management?
- Soft engineering
- Hard engineering
- Managed retreat
What is managed retreat?
Allowing nature to take its course. It is cheap and natural, but there is a risk of loss of property.
What are some examples of hard engineering?
- Cliff base management
- Sea walls
- Revetments
- Gabions
- Groynes
- Rock armour
- Offshore breakwaters
- Rock strongpoints
- Cliff face strategies
- Cliff drainage
- Cliff regrading
What are some examples of soft engineering?
- Offshore reefs
- Beach nourishment
- Managed retreat
- ‘Do nothing’
Remember to revise different forms of coastal management
Table in revision guide - Pg 45
