Flashcards in Coastal Landscape Development Deck (22)
How do wave cut platforms form?
- waves breaking at foot of cliff produce wave cut notch (abrasion)
- as it is undercut, rock above collapses
- causes cliff to retreat
- sloping rock platform is left where cliff used to be, covered at high tide
How is a headland erodes to form a stack? E.g. The foreland at the Dorset Coast.
- erosion exploits weakness in rock, continues to grow forming cave
- if the weakness goes through headland then it will form an arch.
- sub aerial weathering like freeze thaw attack roof of arch until collapse, leaving stack
- attacked at the base by weathering and forms a stump, covered at high tide
What is a spit?
A long narrow feature that extends form the mainland at the end of a drift aligned beach
How do spits form?
- Longshore Drift moves material along the coast but when the coastline changes direction finer material transported out to sea.
- it builds up to form a permanent feature
- can not meet mainland due to river current in estuary and water depth
- wave refraction and second dominant wind direction result in a curved end
- low energy waves behind spit creat saltmarsh
How do tomobolos form?
- offshore island blocks the current of water, sediment can build up, also due to the low energy waves
- the spit that has developed outwards joins the island
- small tidal range so doesn’t get destroyed
How do bars form?
- When the waves approach a sloping coast, friction between the waves and seabed cause the waves to break far from coast
- material is built up parallel to coast to form ridges of sand called offshore bars.
- water could get cut off to form lagoon
What are sand dunes?
Accumulations of sand blown into mounds by the wind.
How do sand dunes form?
- sand accumulated on the beach due to Longshore Drift
- at low tide, sand dries out allowing the wind to move the sand up the beach
- large intertidal zone for sand to be dry
- sand transported by saltation
- Debris on beach traps sand
- grass grows which stabilises the sand
What is isostatic sea level change?
When the land changes causing sea level to rise or fall.
- local change
- over a long time
What is eustatic change?
When the sea levels change causing water levels to rise or fall.
- quicker, but not fast
- human induced
- result of ice melting and thermal expansion
What are raised beaches?
Result of the land rising due to isostatic recovery, former wave cut platforms and beaches raised above sea level e.g. Isle Of Arran
How are fjords formed?
Formed when deep glacial troughs are flooded by rise in sea levels. They are long, steep sided and have a u-shaped cross section.
How do relict cliffs form?
When the land is lifted or sea level falls, it exposes new land like wave cut platforms, so there is a new cliff line. The old cliff line behind the beach is the relict cliff.
How do Dalmation coasts form? e.g. Dalmation coast in Croatia
They are submerging coastlines that form in a landscape of rides and valleys running parallel to the coast. When sea levels rise, the valley floods, but tops of ridges are exposed, forming series of offshore islands parallel to the coast.
How do marine platforms form? e.g. Manu river, Peru
This is quite flat, horizontal or gently inclined surfer of marine origin which has been lifted above sea level.
How do rias form? e.g. Kingsbridge Estuary, Devon
Associated with rising sea levels, form when valleys in a dissected upland area are flooded.
What are the causes of sea level change?
Subsistence - coastal areas sinking, making sea levels higher
Water volume - changes due to thermal expansion or addition of water from land stores e.g. ice melt
What are the inputs of a coastal system?
Things that enter the system from outside sources/systems.
- sub aerial processes
What are the outputs of a coastal system?
Material/energy moving out of the system.
- landforms e.g. wave cut platforms
- shape and position of the coast
What are the flows and transfers of a coastal system?
Processes of movement within the system.
- Longshore Drift
What are the stores/components of a coastal system?
Parts of a system not necessarily in motion.
- spit, beaches etc.
- sand dunes