1.1.9: Variations in coasts over time Flashcards
Fast timescale: changes in seconds
2 examples
High- energy storm activity
Rapid mass movement
Seasonal changes
example
Changes in beach profile
Changes over millennia
example
Sea-level change
Rapid mass movement
Sudden rockfalls, landslides and slumps create changes in cliff-face profiles and retreating cliffs, with the loss of land and possibly buildings.
High energy storm events
Causes an increase in wave energy, resulting in wave erosion and transportation
What can high energy storm events / tsunamis causes
3
- removal of large amounts of beach sediment, changing the profile or removing it altogether
- destruction or breaching of sand dunes
- coastal flooding
Seasonal changes influencing a beach profile
UK Summer
5
fewer storms less frequent high wind speeds lower- energy waves wave predominantly constructive sediment moved onshore, building up the beach
Berm
A beach terrace formed by low energy waves.
Seasonal changes influencing a beach profile
UK Winter
5
More storms High winds more frequent Higher- energy waves Destructive waves more frequent Sediment moved offshore, lowering the beach profile
Sea level change
2 types
Eustatic
Isostatic
Eustatic change
A global change in the volume of water in oceans
Isostatic change
A localised change in the relative sea level.
Causes of eustatic change
3
- during a glaciation period more water is frozen = resulting in a fall in sea level
- global warming of the climate increases the melting of continental ice sheets = causes rise in sea level
- warming of oceans causes the volume of water to expand = creating a rise in sea level
Causes of isosatic change
2
The upward or downward movement of land masses
What causes the upward movement of land masses
Melting ice removes the weight and the land slowly rises = relative fall in sea level (isostatic recovery)
What causes the downward movement of land masses
During the glacial period the weight of the ice causes the land to sink into the crust making sea level appear relatively higher
Impacts of rising sea levels on landforms
3
flood lower-lying parts of the coast
deltas, spits and beaches disappear under water or due to increases rates of erosion
river floodplains and valleys flood to form rias and fjords
Ria
A flooded river valley which becomes a broad river estuary
Fjords
If the flooded valley is a glaciated U-shaped valley a fjord is formed
Features of fjords
Very deep, flat bottomed and steep sided, u-shaped
Threshold
Shallower entrance of a fjord
Skerry
A small, rocky island is created when the sea level rise doesn’t cover the threshold
Raised beaches
Beaches are no longer affected by waves and are left stranded above the new sea level
Relict cliffs
The former cliff lines and landforms left stranded above the new sea level
