Coasts Flashcards
How do waves form
Waves r formed when the wind blows over the surface of the sea , the friction causes it to create ripples , the top of the ripples gain more speed than the bottom until it crashes down . Previous water rushes in to make the wave bigger
Constructive waves
Constructive waves CREATE beaches
Created in calm water
Long low waves
Break at shore
Deposit material to build up beach (swash is greater than backwash)
Destructive waves
Destructive waves DESTROY beaches
Created in storm conditions
Short wavelength
Steep and high
High frequency
Erode coast ~ backwash more powerful than their swash so material is moved away
Erosion
The process of eroding or being eroeded away by water wind or other natural cause (gradual destruction)
Transportation
The movement of material across earths surface by wind water ice or gravity
Deposition
The laying down of sediment by wind flowing water , the sea or ice
Soft engineering methods
Dune regeneration:
Artificial creation or regeneration of sand dunes
Takes 7 years
Done by hand
Beach nourishment:
Sand added to beach to replace eroded sand
Replaced regularly
Little environmental impact
How do rock armour work
Large boulders with gaps to loose energy of waves so beach isn’t eroded
Small or weak rocks won’t work
Cheap and relatively weak
How do sea walls work
Concrete walk built to protect the coast from coastal erosion .
Stops waves from hitting coastline
Nice for tourists to walk on
Expensive
Why are coasts uneven
Praviling wind hits the coastline eroding it away creating a bay the 2 headlands stick out with the coastline further back making it uneven
3 types of erosion erode coasts
Abrasion
Attrition
Hydraulic action
What is hydraulic power.
Waves crash against rock & compress air in the cracks
This puts pressure on rocks
Repeated compression in cracks makes cracks bigger
Causes bits of rock to break off
What is abrasion
Particles in water (from erosion) scrape & rub against the rock
Removes small pieces
What is Attrition
Eroded particles in water collide & break into smaller pieces
Become more rounded
Process that Makes pebbles smooth
What is solution
Process by which sea water dissolves some rocks
In UK chalk & limestone
2 Processes shaping the coastline
Chemical
Mechanical
What is mechanical weathering
Breakdown of rock without changing its chemical compostiton
Freeze thaw weathering
When temp flipuctuates above & below 0 degrees
Water enters cracks in rock eg granite
Water freezes so it expands as ice
Ice thaws so it contracts - releasing the pressure on the rock
Repeated freezing/ thawing widens the cracks causes rock to break up
Mechanical weathering - Salt weathering
Salt weathering
Salt enters crack, water evaporates leaving salt crystals that grow & expand
Chemical weathering give examples
changing the chemical composition of rock
Carbonation
Hydrolysis
Oxidation
Carbonation
Occurs in wet & warm conditions
Rainwater has carbon dioxide i it
Makes it weaker carbonic acid
Carbonic acid reacts with rock that has calcium carbonate in it
Eg limestone
dissolves the rocks
Hydrolysis
Water reacts with minerals in the rock causing composition of rock to change & become more unstable
Rock breaks down
Oxidation
Oxygen reacts with minerals such as calcium & magnesium to from iron oxide
Iron oxide is red/brown
Causes decomposition of rock
Mass movement
Shifting of rocks eg cliff
Causes by gravity pulling down on slope
Causes rapid retreat of coastline
More likely if material is full of water - acts as lubricant, makes material heavier
Creates a SCARP in slope - see diagrams in book must be able to sketch
SLIDES
sLUMPS
ROCkFALL
How is eroded material Transported along the coast?
Longshore drift
What’s longshore drift?
Waves follow direction of prevailing wind
Usually hit coast at oblique angle
Swash carries material UP beach
Backwash carries material DOWN the beach at right angles
Overtime material zig zags along coast
Be able to draw diagram of longshore drift
What is SWASH?
What is BACKWASH.
4 process of transportation
Depends on how powerful the movement of water is & size of particles
-traction
-saltation
-suspension
-saltation
-solution
Traction
Large particles -boulders are pushed along as bed by force of water
Saltation
Pebble size particles
