Coasts Flashcards
What are the 2 landforms of coastal erosion?
Cliffs and wave cut platforms
Cliff profile features
What are the 3 factors affecting the development of cliffs and wave cut platforms?
Rock type
Wave energy
Coastal morphology
Explain how wave cut platforms form.
When destructive waves break at the foot of a cliff their energy is concentrated onto a small area of the rock face between high water mark and LWM.
Erosion undercuts the cliff forming a wave cut notch.
The overhanging cliff is subject to weathering and eventually collapses.
After successive collapses the cliff line will begin to retreat, forming a gently sloping wave cut platform at the base of the cliff.
Which type of erosion is the most significant in forming wave cut notches?
Abrasion
What angle are wave cut platforms at?
Less than 5 degrees
Why do wave cut platforms not grow bigger than 500m?
As the platform grows the waves break further out to sea and their energy is dissipated before reaching the cliffs - forming a negative feedback loop
How can wave-cut platforms become rough and jagged?
If the platform remains in the tidal zone it will be continually exposed to cycles of marine and sub-aerial processes, exploiting weaknesses in the rock surface.
What features may form on wave cut platforms that remain in the tidal zone?
Rock pools and fissures
Give an example of a wave cut platform in the UK.
Flamborough Head, North Yorkshire
How long can wave-cut platforms take to form?
100s - 1000s of years
What landforms form on coastlines of emergence?
Raised beaches
Wave cut platforms
What are marine features that are left above the high tide level called?
Relict features
Why may raised beaches appear as grassy terraces?
Once above the high tide line they are subject to vegetation succession
What landforms form on coastlines of submergence?
Rias and fjords
Dalmatian coasts
What are rias?
Coastal inlets
How do rias form?
Sea level rises relative to the land, flooding river valleys
How do fjords form?
Glaciers erode to create steep-sided U-shaped valleys.
Sea level rises relative to the land, flooding the glacial valleys.
Why are fjords often shallower at the mouth than further inland?
Glaciers can overdeepen their valley
How do Dalmatian coasts form?
Sea level rises relative to the land.
River systems which once ran parallel to the coast are flooded
What are Dalmatian coasts?
A series of long islands that were once hills along valley sides.
What is the key difference between Dalmatian coasts and rias?
The angle to the coastline at which they run
What are the 2 different types of sea level change?
Isostatic
Eustatic
What is isostatic sea level change?
Changes in sea level as a result of the changing level of the land.
What is eustatic sea level change?
Changes in sea level as a result of the changing level of water in the oceans.
On what scale does isostatic sea level change occur?
Local/regional
On what scale does eustatic sea level change occur?
Global
How quickly are sea levels currently rising?
3.2mm per year
What is the main reason for current sea level rise?
Thermal expansion
What are the 3 causes of isostatic change?
Tectonic activity
Glaciation
Post-glacial readjustment
What are the 2 factors affecting the development of mudflats and saltmarshes?
Energy of coastlines
Tidal range
What type of energy coastline do estuarine landforms form on?
Low energy coastlines
What kind of succession is the formation of saltmarshes?
Halosere
How do mudlfats form?
Saltwater flowing into an estuary at high tide brings large amounts of fine sediments.
This meets the slow river which is carrying fine silts and clays.
Flocculation occurs when the two flows meet, resulting in large clay particles sinking to the bed.
At low tide this mud is exposed in the intertidal area with water flowing in channels between the mudflats.
How do mudflats develop into saltmarshes?
Low lying vegetation begins to grow on the mudflats.
This slows currents leading to further deposition.
Pioneer species colonise the area.
Gradual colonisation by other plants forms a dense mat of vegetation up to 15cm high.
Vegetation growth slows currents further, leading to more mud and silt accumulation.
The mudflats are submerged for an increasingly shorter period of time so become a saltmarsh.
Give an example of a pioneer species on mudflats.
Spartina
What is flocculation?
Where fine particles settle out of suspension
Why are sand beaches gently sloped?
Sand grains are small and easily compacted so little water percolates through. The majority of water moving up the beach therefore also returns through backwash which smooths and flattens the beach.
Why does shingle tend to be at the top of the beach?
It takes high energy storm waves to deposit the larger material.
What are the 2 classifications of beaches?
Swash-aligned
Drift-aligned
Sand dunes
Embryo -> Yellow -> Grey -> Woodland
MARRAM GRASS
