Coasts Flashcards
How are waves created?
The wind blows over the sea and makes ripples
These ripples become deeper and form swells
As the sea gets shallower when it approaches land, the bottom of the swell slows down due to friction
The top continues as the same speed
The top crests to form a wave
What is fetch?
The distance the wave has travelled
What is the name of the strongest wind?
The prevailing wind
What is the movement of water up a beach / onto land?
Swash
What is backwash?
The retreat / movement of water back down a beach
What are the two types of wave?
Constructive and destructive
What are the characteristics of a constructive wave?
Shorter fetch, calmer wave, depositional, weak backwash
7 WAVES PER MINUTE
What are the characteristics of destructive wave?
Longer fetch, turbulent, taller, destructive wave, strong backwash, erosional, high energy
14 WAVES PER MINUTE
What are the different types of mass - movement?
Rockfall
Landslide
Mudflow
Rotational slip
What is rockfall?
Freeze-thaw weathering loosens rock, making it more susceptible to gravity
Water enters cracks and expands as it freezes causing the rock to break and fall away
What is a landslide?
Landslides are triggered by periods of heavy rain that saturate the permeable soft rock
This means the top layer of rock is heavier and it slides down the cliff face
What is mudflow?
Mud flow only occurs on steep slopes when periods of heavy rain causes permeable soil to absorb the water and slip over the more impermeable soil beneath it to cause a mudflow
It is very fast and dangerous
What is rotational slip?
Rotational slip is where a landslide rotates as it flows
This leaves behind a deeper indentation and a curved surface, it is also more dangerous and destructive
What types of sub-aerial weathering affect the coastline?
Biological weathering Chemical weathering Salt crystallisation Pressure Release Freeze - thaw Mechanical weathering
How is a beach formed?
Swash and backwash move sediment around
Longshore drift means sediment is carried in at an angle due to the prevailing wind
The sea deposits the sediment when longshore drift is stopped by a head land and a beach is formed
Cliffs nearby provide a source of sediment
Beaches are formed when swash is stronger than backwash
How does a fault become a cave?
Corrosion and hydraulic action widen the weak fault and it becomes a cave
How is an arch formed?
As the protruding headland is eroded from both sides, the thin wall behind the cave falls through.
How is a stack formed?
Weathering weakens the cliff above an arch and the arch grows bigger
Over time, the weight is too much and the arch falls through to leave a stack
How are wave cut notches and wave-cut platforms formed?
The wave erodes the cliff face between the high tide water mark and the low tide water mark
Abrasion and hydraulic action
This cave formed is a wave cut notch
As the cliff above it is unsupported, eventually gravity causes it to fall
The cliff retreats and a notch is formed again etc
The land marking where the cliff used to be is the wave cut plat form
Where is cord grass found?
In the mudflats and low marsh
It is a pioneer plant
What is vegetation succession?
When mudflats turn into marsh uplands over hundreds of years
Explain vegetation succession
In an area with a high rate of deposition for example a spit, mud is deposited
Pioneer plants that are salt tolerant begin to grow
Gradually more mud builds up and breaks the surface of the sea
More wildlife like wold spiders live in the area
As the plants die, they decompose as layers of soil
More plant species are able to grow from the nutrients in the dead plants
The area eventually becomes a marsh upland, a habitat like a meadow
How is erosion managed in mappleton?
Shoreline managament plan in 1991 costing 2mil
Rock Groynes - reduce 4m of cliff erosion per year
Cliff face regarded to make it more stable
How is erosion managed in Withernsea
Hard engineering : sea walls
Straight wall/ recurved wall -expensive
Rock armour
Dissipates wave energy / very expensive
What is longshore drift?
Waves approach the beach at an angle and retreat at 90 degrees. This causes the movement of sediment along the beaches
How are headland and bays formed?
Soft rock is eroded by the sea whereas the headlands of hard rock are not. This leaves bays and headlands
How are spits formed?
Long shore drift transports the sediment down the coast in the direction of the prevailing wind
A change of shape in the land caused by an estuary, such as a protruding headland, stops longshore drift and it deposits sediment away from the coast
The estuary and secondary wind shapes this inwards and a sheltered area saturated with salt forms inside the spit.
How are bars formed?
A bar is formed where a spit crosses two headlands and sections off a bay forming a lagoon
How are tombolos formed?
A tombolo is formed as a spit grows larger and intercepts with an offshore island
By how much is sea level expected to rise by 2100?
- 18 - 0.38 (opimistic)
0. 26 - 0.59 (pessimistic)
Why are sea levels rising?
- Global warming heats sea and it expands as the particles are further apart (thermal expansion)
- Ice sheets are melting
- Post glacial rebound will cause sea levels to rise in the south due to melting glaciers in the north
What are the effects of rising sea level on Tuvalu, Polynesia?
- 5m rise in king tide
- Loss of fishing industry
- Loss of permeable land
- People relocated to New Zealand
- Loss of culture and language
What’s the highest point above sea in Tuvalu?
4.5m
Where is Tuvalu located?
Polynesian Island
Pacific ocean
Midway between Australia and Hawaii
What are the environmental impacts of high sea level rise on Tuvalu?
- Salt water intrusion from salt water floods ruins land
- Flooding and storm surges will erode soils
- Bleached coral reefs due to warm sunlight
What are the social impacts of high sea levels on Tuvalu?
- 4000 Tuvaluans lving in New Zealand
- Families ripped apart
- Cultures and traditions dying out
- Health problems caused by damp infrastructure such as typhoid and diorhea
What are the economic impacts of rising sea levels on Tuvalu?
- Bleaching of coral reef
- Salt water intrusion eg Pulakka
Impacting fishing industry
Down turn in GDP since 2002
What are the political impacts of rising sea levels in Tuvalu?
- Government has to plan for 10,000 remaining residents
- Government campaigns to raise awareness
- Tuvalu relies on aid from New Zealand
What is the average rate of erosion per year?
2m
What is the geology of the Holderness coast?
- Soft boulder sheets left from retreat of glaciers 12000 years ago
- Erratics
- Chalk
Soft and so easily eroded
What weathering is attacking the Holderness Coast?
- Soft cliffs become saturated with rain water and triggers MUDFLOW
- Cold temperatures cause water to freeze and expand causing LANDSLIDES
How is the sea causing the Holderness coast to retreat?
- Destructive waves from north east attack cliff base
- Hydraulic action and abrasion cause wave cut notches and platforms
What are the negatives of rock groynes (Terminal groyne syndrome)?
Rock groynes halt the process of longshore drift
This means sediment is not carried accross or deposited to protect the cliffs further along the coastline
These cliffs are exposed to erosion
What are the impacts of cliff collapse along the Holderness Coast?
- 4km land lost since Roman times
- Easington gas station at risk
- Fall in property pricing (values as low as £1)
- Compensation
- Fall in habitats and tourism
How do sea walls protect against erosion (high engineering)?
- Sea walls deflect force of water
- Energy is absorbed by the sandy beach rather than the land
What is rock armour (hard engineering)?
Boulders placed in front of sea front / sea wall to absorb wave energy
What is Marsh creation (soft engineering)?
Marsh flooding is the controlled and purposeful flooding of areas in order to create marshes that buffer and absorb water and flood energy
What is managed retreat (soft engineering)?
Managed retreat is when areas are left to flood naturally
Homes and farmland are submerged and relocated
Why is Lyme Regis vulnerable to cliff collapse and erosion?
- Strong southern winds bring large waves
- Geology of porous soil and limestone on top of impermeable Black Ven Marl causes mudflow and landslides when it rains
What types of Hard engineering has Lyme Regis implimented?
- Strong sea wall
- Rock armour
- Extended The Cobb with rock armour
- 2 Stone Groynes
- Drainage improvements to reduce saturated ground
- Metal piling secures limestone to marl to reduce risk of mudflow
What types of soft engineering has lyme regis implimented?
- Beach nourishment
- Landslide early warning system
What are the costs of Lyme Regis’ anti cliff collapse schemes?
- cost £21 million
- Disruption to environmentally sensitive area
- Eye sore
- Changes to cliff habitat
- Terminal groyne syndrome
What are the benefits of Lyme Regis’ anti Cliff collapse schemes?
- Safeguards 140 homes
- Secures tourist industry woth £994 million
- Landslide early warning system
- Secures beach
- More beachside amneties
