Coastal landscape Development Flashcards
How is a wave cut platform formed? (4)
1) waves break at foot of cliff from a wave-cut notch
2) Undercutting rock as a result of erosion by waves
3) As undercutting continues, rock above collapses and cliff gradually retreats
4) A sloping rocky platform is left behind, the wave cut platform, covered at high tide
What effect do wave cut platforms have on the rate of erosion?
- They affect the waves ability to erode the cliff because they have further to travel in shallow water
- they break earlier and dissipate their energy, reducing rates of erosion
How does soil creep occur?
Slow form of movement of individual soil particles moving down a hill or slope
How does mudflow occur?
Earth and mud flowing down a slope or hill
How does run off occur?
A type of flow from one store (rockface) to another (beach or sea)
How does landslide/ slump occur?
Where material slides on a curved surface over weak and unsolidated rock
How does rockfall occur/
Sudden form of collpase or breaking away from rocks from a cliff face
Where are 2 examples of wave cut platforms OUTSIDE the UK?
Collaroy Beach, NSW, Australia
Fisherman’s Rock, NZ
Where are 2 examples of cliffs located outside the UK?
Ketbjorg Cliffs, Iceland
Dryholaey, Iceland
Where are 2 examples of caves located outside the UK?
Puntq de Arucas, Spain
Waiahuakua Cave, Hawaii
Where are 2 examples of arches located outside the UK?
Es Pontas Arch, Mallorca, Spain
The azure Window, Malta
Where are 2 examples of stacks located outside the UK?
Stacka in Dryholaey, Iceland
12 apostles stack, Australia
How is a stack formed? (5)
1) Headland is attacked by waves along lines of weakness
2) The erosion exploits weakness, forming a cave
3) If the weakness runs through the headland, 2 caves may from back to back
4) Eventually an arch forms
5) Wave attacks continues at the base of the arch until it collapsed, leaving a stack
How is a stump formed?
When a stack is continually eroded until it collapses
In what conditions do sand dunes form?
When dry material from flat, open beaches is blown inland
In what conditions do mudflats and salt marshes form?
When finer material sticks together in the shallow water of estuaries
When do beach cusps occur?
When the coarser material at the top of the beach absorbs wave swash
Where do bay head beaches build up?
In sheltered, low energy environments of coves. Wave refraction focuses erosion on the surrounding headlands, encouraging deposition in the bay
Where do bays form?
Bays form across estuaries, blocking off rivers
Where do barrier beaches (bars) form?
Bars form where waves recycle offshore material
How do drift-aligned beaches develop?
Where waves approach the coastline at an angle, the swash moves material up the beach in that direction, and the backwash returns at right angles (LSD)
A range of partially detached features are formed
How do swash-aligned beaches develop?
when waves break parallel with the coasts, the movement of water and material is largely up and down the beach
What features arise from swash-aligned beaches? (3)
Bay head beaches
Bay bars
Barrier beaches
What features devlop from drift aligned beaches? (4)
Spits
Recurved spits
Tombolos
Cuspate forelands
What are tombolos?
When a spit extends from the coast to an island
When does deposition occur?
When there is insufficient energy to move sediments further in low-energy environments
How does pebble size change up the beach?
Bigger, heavier pebbles are found further on the beach because more energy is required to transport them. Smaller lighter ones are further up the backshore
What are the features of swash aligned beaches? (3)
- Beaches can be large, especially if facing onto prevailing wind
- Landforms are created by offshore sediment
- Found right at the back of bays due to wave refraction
What are the features of drift aligned becahes?
Pebbles and sand drift all the way along because of the wind direction
Landforms: spits, bars and tombolos
What is a spit?
A long, narrow feature that extends from the mainland at the end of the drift aligned beach when prevailing wind blows at an angle to the coastline
Why does a recurved end occur?
Wave refractrion and a 2nd dominant wind force moves material in a different direction
What are examples of tombolos?
Isle of Purbeck, UK
Angel Road, Shodo Island
In what conditions do tombolos form? (6)
Island close to the mainland
Area of shallow water
Preferential supply of sediment (cliff erosion)
Small, low-energy waves
Sheltered area
Consistent prevailing wind
when are offshore bars formed?
Offshore bars are formed when material is built up parallel to the coast
When are barrier beaches formed?
If a bar reaches a headland and the body of water behind is cut off
What are examples of barrier beaches?
Slapton Sands, Devon, UK
Cies Island Bar, Spain
What’s are barrier islands?
Islands formed parallel to the coastline but not touching it, a lagoon may form behind
What are some examples of barrier islands?
Scoot Head Island, Norfolk, UK
Padre Island, Texas
How are sand dunes formed? (6)
1) Sand accumulated on beach from LSD
2) At low tide, sand dries out, allowing prevailing wind to move it up beach
3) Large intertidal range for sand to dry
4) Sand transported by saltation
5) Debris on beach traps it
6) Grasses grow and stabilize dunes
What is a strand line?
Where debris traps the sand to begin forming a dune
What is fluid threshold velocity?
The amount if energy the wind must have to move the sand on a beach
What are the stages of dune formation? (6)
Every Fat Yeti Gets Donuts More
Embryo dune
Fore dune
Yellow dune
Grey/fixed dune
Dune slack
Mature dune/heath
What are the features of an embryo dune? (3)
- Sand continually moving - needs obstruction to break force of wind
- High pH wind speed
- Lots of salt spray, >1m tall, exposed
What are the features of fore dunes? (4)
- Drought resistant plants colonies e.g Lyme grass, Matran grass
- As they grow, more sand is trapped, building height
- Pioneer species
- Height increases to 5m - 20% of sand exposed
What are the features of yellow dunes? (3)
Greater diversity of plants, humus exposed, alkaline pH, more shelter and less spray
Marran grass dominates, moss, heather etc
5-10m high, 80% sand vegetated
What are the features of grey dunes?
Stable, 100% marram grass and small shrubs
What are the features of dune slacks? (3)
Found between mature dunes
Where the water table reaches the surface
Plants adapt to damp and shelter, cotton grass, rushes etc
What are the features of climax vegetation? (2)
May have pine/birch in acidic conditions or beech in alkaline
Increased depth of soil and distance from the sea reduces salt
What type of features are salt marshes and mudflats?
Esturine
What are mudflats?
Created by deposition of fine silts and clays in sheltered low energy coastal environments such as estuaries
What are salt marshes?
an area of coastal grassland that is regularly flooded by seawater.
What are factors affecting salt marsh development? (8)
When Rain Sometimes Happens Some Cats Will Toboggan
Weather
River regime
Sediment supply
Human action
Sea level
Climate
Wave type
Tidal regime
How does weather impact salt marsh development?
Storms can erode the marsh
How does river regime impact salt marsh development?
Changes in currents and volume can effect erosion
How does sediment supply impact salt marsh development?
Supply chnages can enhance or diminish the available silt
How does human action impact salt marsh development?
Commercial, industrial and recreational activity can damage marsh
How does sea level impact salt marsh development?
Tides can upset equilibrium and destroy marshes
How does climate impact salt marsh development?
Affects species type, growth rates and sea levels
How does wave type impact salt marsh development?
Changes in direction, nature and size can affect salt marsh stability
How does tidal regime impact salt marsh development?
Changes in tidal currenrs can increase erosion and alter species
What is key to salt marsh development?
A low energy environment
What are the required features for mudflat formation? (5)
Supply of sediment, coastal or fluvial
Low energy, sheltered area
In an area where the deposition will occur
Where salt and freshwater meet
Where there are no strong tides or currents to wash sediment away
What is a pioneer species?
Hardy plants tolerate to flooding which first colonise an area
What is flocculation?
Tiny particles of mud sticking together to enable them to sink
What are halophytes?
Plants tolerant to the salt and frequent flooding caused by tides
What is the process of succession in a salt marsh?
- As tidal currents are slowed, material is deposited
- Eel grass may begin to grow, slow tides more
- Mudflats begin to develop and halophytes colonize
- Glasswort develops close vegetation over mud
- Plants trap more sediment and leaves and stalks help to build up
-Mud rises, creek system forms
-Eventually rises above sea level and new species grow - Upper levels of marsh are rarely flooded and salt marsh succession is complete
How could sea level rise threaten salt marshes and mudflats?
As sea levels rise, storms will increase in frequency, leading to more frequent flooding so succession becomes impossible.
The low energy environemnt will alse be disrupted
Why are salt marshes and mud flats much rarer than other depositional landforms?
Because the conditions they require are so specific
What is isostatic sea level change?
Local changes in sea level resulting from the land rising or falling relative to the sea
What is eustatic sea level change?
global sea level change
What are the 2 major factors causing eustatic change?
Thermal expansion
Ice melt
How have sea levels changed in the last 10,000 years?
They have generally risen, with some times of fluctuation due to warming and cooling of the oceans
How can tectonics alter sea level?
As they change the volune of the oceane, making them larger or smaller and affecting the water capacity they can hold
How would glaciation affect isostatic and eustatic change?
- Global temperatures cool, ice accumulated in land to form glaciers and ice sheets
- Accumulation of ice reduces water available to fill oceans, eustatic fall
- Relative fall in sea level partly moderated by ice forcing land mass down by isostatic change
- When climate warms, ice melts and eustatic rise
- Rising seas flood some coastlines and create submergent features
- Once ice is fully melted, isostatic rebound occurs
- Prolonged rebound allows emergent features
What are the differences between isostatic and eustatic change? (5)
-Eustatic is global, isostatic local
-Eustatic is actual, isostatic is relative
-Eustatic is change to sea, isostatic is changes to land
-Eustatic is much quicker
-Eustatic can be human induced, isostatic cannot
How are raised beaches formed?
As land rises in isostatic change, former wave cut platforms and beaches raise above current sea level
Where is an example of a raised beach?
The Isle if Arran, Scotland
How are fjords formed?
When deep glacial troughs are flooded by a rise in sea level
What are the features of fjords?
Long and steep sided with a U shape valley cross section and hanging valleys. Much deeper inland than at coast
Where is an example of a fjord?
Milford Sound, NZ
How are relict/ fossils cliffs formed? (3)
Coasts undergo isostatic change and land rises.
Sea can no longer reach the cliff face, so erosion stops.
Leaves relict cliff set way back from the coast and now beach formed in front
Where is an example of a relict cliff?
Isle of Arran, Scotland
How are rias formed?
when valleys in upland areas are flooded due to eustatic rise
Where are rias often found?
Lower parts of rivers and tributaries with were drowned, such as in South Wedt England where sea levels rose after the last ice age
Where is an example of a ria?
Kingsbridge, Devon
How are marine platforms/terraces formed?
Wave cut platforms lifted out if the wave activity zone by isostatic change as sea levels fall relative to the land
Where is an example of marine terrace?
Isle of Arran, Scotland
How are Dalmatian coasts formed?
When a landscape of ridges and valleys running parallel to the coast is flooded. As sea levels rise, tops of ridges remain exposed while valleys are submerged, leaving a series of offshore islands
Where is an example of a Dalmatian coast?
The Dalmation Coast, Croatia
Which landforms are submerged? (3)
Fjords
Rias
Dalmation Coasts
Which landforms are emergent? (3)
Raised beaches
Relict cliffs
Marine platforms
What is water volume change?
Due to thermal expansion or addititon of extra water frim land stores (ice melt)
What is subsistence?
Coastal areas sink often due to excess groundwater abstraction.
Has the effect of making sea level relatively higher.
What takes in most of the heat from global warming?
The oceans, at 90%
How could underground water resources be affected by sea level rise?
The zone where seawater mixes with fresh water in rivers is dynamic and a rise in sea levels can cause it to move upstream
What are some of the effects of climate change on the coasts? (4)
Villages can be lost to flooding
Groundwater can become salt contaminated
High-value agricultural land lost
Higher rates of erosion with sea level rise
What are the features of dune heath/mature dunes?
Found 100m from shore
If undisturbed can support shrubs and trees such as ash and birch
Fast growing conifers may be planted
