Coasts - Coastal landscape development Flashcards
How is a wave cut platform formed?
- Waves breaking at foot of cliff form wave cut notch
- Undercutting is result of erosion by waves
- As undercutting continues, rock above collapses and cliff gradually retreats
- 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 wave’s 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
What type of process is soil creep?
Creep/flow
What type of process is mudflow?
Flow
What type of process is run off?
Flow
What type of process is landslide/slump?
Slide
What type of process is rockfall?
Fall
How does soil creep occur?
Slow form of movement of individual soil particles moving down a hill or slope, slow
How does mudflow occur?
Earth and mud flowing down a slope or hill, fast
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 unconsolidated rock (loosely - particles not held together)
How does rockfall occur?
Sudden form of collapse or breaking away of rocks from a cliff face
Where are two examples of wave cut platforms outside the UK?
- Collaroy Beach, New South Wales, Australia
- Fisherman’s Rock, NZ
Where are two examples of cliffs located outside the UK?
- Ketubjorg Cliffs, Iceland
- Dryholaey, Iceland
Where are two examples of caves located outside the UK?
- Punta de Arucas, Spain
- Waiahuakua Cave, Hawaii
Where are two examples of arches located outside the UK?
- Es Pontas Arch, Mallorca, Spain
- The Azure Window, Malta
Where are two examples of stacks located outside the U.K.?
- Stacks in Dryholaey, Iceland
- Twelve Apostles Stacks, Victoria, Australia
Where are two examples of stumps located outside the UK?
- Faro, off the coast of Sweden
- Bay of Naples, Italy
How is a stack formed?
- Headland is attacked by waves along lines of weakness
- The erosion exploits a weakness, forming a cave
- If the weakness runs through the headland, two caves may form back to back
- Eventually an arch is formed
- Wave attack continues at the base of the arch until it collapses, leaving a stack
How is a stump formed?
When a stack is continually eroded until it collapses
In what conditions do slash aligned beaches form?
When waves break parallel to the coast
In what conditions do drift aligned beached form?
When longshore drift moves material down the coast, producing a range of partially detached features
In what conditions do sand dunes form?
When dry material from flat, open beaches is blown inland
In what conditions do mudflats and slat marshes form?
When finer material stacks together in the shallow water of estuaries
When do beach cusps occur?
Where 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 eadands, encouraging deposition in the bay
Where do bay bars form?
Across estuaries, blocking off rivers - where there is a gap
Where do barrier beaches form?
Where waves recycle offshore material - where there is a gap in the coastline
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 - LONGSHORE DRIFT
How do swash aligned beaches develop?
When waves break parallel with the coast, the movement of water an material is largely up and down the beach.
What features arise from swash aligned beaches?
Bay head beaches
Bay bars
Barrier beaches
What features develop from drift aligned beaches?
- Spits
- Recurved spits (curved end)
- Tombolos
What are tombolos?
When spits extend from the coasts to an island
When does deposition occur?
When there is insufficient energy to move sediments further in low energy environments
Where do runnels form?
Close to low water marks, separating pools of standing water at low tide
Where do ripples form?
Small marks that appear where the slope of the beach increases and where the tide moves over the beach
How does pebble size change up the beach?
Bigger, heavier pebbles are found further up the beach because more energy is required to transport them. Smaller lighter ones are further up to the backshore.
What are the features of swash aligned beaches?
- Beaches can be large, especially if facing into 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 beaches?
- Pebbles and sand drift along because of wind direction
- Landforms created by material moved along beach by LSD
What is a spit?
A long, narrow feature that extends from the mainland at the end of a drift aligned beach
Why does a recurved end occur on a spit?
Wave refraction and a second dominant wind force material to move in a different direction
What are examples of tombolos?
- Isle of Purbeck, UK
- Angel Road, Shodo Island
In what conditions do tombolos form?
- Island close to mainland
- Area of shallow water
- Preferential supply of sediment (cliff erosion)
- Small, low energy waves
- Sheltered area
- Consistent prevailing wind
What is a wave-cut platform?
A gently sloping (less than 5 degrees), relatively smooth, marine platform caused by abrasion at the base of the cliff.
What is a bar?
When a spit develops across a bay where there is no strong flow of water from the landward side, and sediment travels to reach across to the other side of the bay, creating a lagoon behind the bar.
What is eustatic change?
A global change in sea level resulting from an actual fall or rise in the level of the sea itself.
What is isostatic change?
Local changes in sea level resulting from the land rising or falling relative to the sea.
What is a fjord?
- Submergent landform
- Former glacial valley drowned by rising sea levels.
What are raised beaches?
- Emergent landform
- Areas of former wave-cut platforms and their beaches which are at a level higher than the present sea level.
What is a ria?
- Submergent landform
- Former river valley drowned by rising sea levels.
What are dalmation coasts?
- Submergent landform
- A series of longitudinal river valleys next to the coast that have been flooded by rising sea level leaving parallel ranges of watershed ridges as islands.
What are emergent landforms?
Appear towards the end of an ice age and occur when isostatic rebound takes place faster than eustatic rise in sea level. = land height rising faster than sea.
What are submergent landforms?
When eustatic rise in sea level happens faster than the isostatic rebound after an ice age. Water starts to flood the land + landforms on land.
What are marine platforms/terraces?
-Emergent landform
-Wave-cut platform that now exists as an extensive flat area in front of a relict cliff above the wave action.
Form as a result of isostatic recovery.
What are relict/fossil cliffs?
- Emergent landform
- An old cliff above the current sea level displaying features like caves, arches + stacks.
- Caused by isostatic rebound.
What are saltmarshes?
A saltmarsh is an area of coastal grassland that is regularly flooded by seawater.
What are mudflats?
Mudflats are created by the deposition of fine silts and clays in sheltered low energy environments like estuaries.
What is the difference between saltmarshes and mudflats?
Saltmarshes have more vegetation and mudflats are more common.
What are pioneer species?
Species that first colonize new, barren habitats created by disturbance, they are hardy e.g. marram grass and lyme grass.
What are halophytes?
A salt tolerant plant that grows in soil or waters of high salinity, coming into contact with salt water through their roots or salt spray e.g. swamps + marshes. Tolerant to periodic soaking of the sea.
What is flocculation?
Deposition due to particles clumping together.
-As sediment is dropped its charged particles like clay + polymers clump together to form flocs - deposition as they are attracted to each other. .
What is succession?
A vegetation sequence developed over time, it is the changing phases of dominant plant species.
What is the process of succession (saltmarshes)?
- Deposition of clay/silt
- Grasses begin to grow (e.g. eel grass which slows current further), leading to more deposition
- Gradually marsh gets higher
- Plants die and nutrients added via decomposition
- More plants and new plants grow as the conditions improve due to more nutrients
- Sea aster and sea lavender start to grow as they can’t tolerate submergence due to them being less adapted (like halophytes)
- Eventually a ‘terrestrial ecosystem’ forms with tress, etc, and creates land.
