Coast Flashcards
Abrasion
When pebbles are picked by the waves and thrown against the cliff this create a sand paper effect
Hydraulic action
Force of the wave hit the rock, the air is trapped by the wave in the crock and cracks it further due to the hydraulic pressure
Attrition
When rocks that the river is carrying knock against each other they break apart to become smaller and more rounded
Solution/corrosion
Where the rock is put into the solution by weak acid
Characteristics of destructive waves
High wave height
Beach gradient steep
Plunge forward
Smash is weak
Rotation of water causes strong backwash
Erodes beaches
Constructive wave characteristics
Low wave height
Beach gradient is gentle
Spill forward gently
Creates a strong swath
Water drains through beach material
Backwash is weak
Build up beaches
Key factor that affect the coast
Geology- hard rock types are less likely to erode
Fetch of the wave and the strength of the wind. Powerful winds and a long fetch create the most damaging erosive waves
The angle of the slope- steep slopes erode more violently and frequently
Weather conditions- freezing temperatures and heavy rain increases weathering and rate of erosion
Amount of vegetation- presence of vegetation helps stabilise slope but also increase occurrence of the biological weathering
The amount of human interference- if there are no man-made structure(eg sea wall) to protect the coast then the coast is more vulnerable to attack.
Explain how longshore drift
- Prevailing winds pushes the wave at an angle eh oh then picks up sediment they come in at an angle because of the wind direction.
- Smash moves up the beach at the angle
- the wave that called backwash pulls the sediment back down straight to the beach,
- the process then gradually moving sediment along the beach in a zigzag motion and is called longshore drift
Coastal deposition
It where the material that is being transported is dropped by a constructive wave, this happens when waves have less energy, when smash is stronger than backwash
Wave cut platform
Wave cut platform is formed by the sea attacking the cliff face though different type of erosion
Abrasion is where the cliff are worn down from destructive waves and throwing of the material in the wave
Hydraulic action occur when the when enter the cracks within the cliff at the high tide mark compressing the air within resulting in expansion of the crack as the wave retreats
This then has the effect of creating a notch which slowly become larger and larger forming a small cave
As erosion continues to occur the weight of the cliff eventually can’t support itself and collapse as a result with the material being deposited and then carried out the the sea through repetition of these processes, a wave cut platform is formed
Formation of cave
Crack in the rock erode through abrasion
Cave occur when the wave force their way into the crack in the cliff face.The water contain sand and other materials grind away at the rock until the cracks become a cave . This is called hydraulic action and abrasion are the main Erosion
Formation of arch
If the cave is formed in a headland. It may eventually break through to the other side forming an arch
Formation of stack
The arch will continue to be eroded(attrition) and will gradually become bigger until it can no longer support the top of the arch. When the arch collapse , it leaves the head land on one side and a stack( a tall column rock) on the other
Formation of stump
The stack will be attacked at the base in the same way that a wave-cut notch is formed. This weakens the structure and it will eventually collapse to form a stump
Discordant coastline
Have bays and headlands as there are alternating hard and soft rock
Concord at coastline
Have less bay and lead lands as there are made up of the same type of rock
Formation Bay and headlands
Headland and bays are formed at the discordant coastline.
The bands of soft rock are less resistant to erosion, such as sand and clay
Therefore, they erode more quickly than the hard rock which is more resistant such as limestone
Waves are able to erode the soft rock more rapidly and form bays. Bay form beaches and are covered by layers of loosely consolidated sand ,slit and clay.
Bays are made of rock that are easily eroded
Erosion by waves at the base of these cliffs cause slumping and the cliff sediment collapse on on the beach. Storm can lead to an increase erosion
Once bays are formed they become protected by the headland and so are less eroded
The hard rock is left jutting out into the sea and forms headland
Once formed the headland is then left more vulnerable to erosion and the wave energy is concentrated here
Formation of split
Prevailing winds come at an angle
The smash come at an angle and the backwash goes vertically straight out to the sea
This creates a zig zag movement known as longshore drift
The split develops where there is a change in direction of the coastline hook by the wave in the other direction
Formation of sand dunes
The sand is blown by the wind
Obstacles/plant causes the wind to slow and deposit sand
—> this increases size of the obstacle I.e the dune grows
Beaches
The smash carries the deposit to the collapsed rock of attrition and longshore drift carries further deposit
The coast material is deposited at the upper limit reached by the swath and the back wash leaves the smallest material last
Factors for coral reef
Coral reef are found in or near the tropics
- TEMPERATURE- mean annual temperature has to be over 18 optimum 24
- DEPTH- can only grown in the water less than 25 metres deep
- LIGHT- shallow water allows light for tiny photosynthesising algae providing coral food
- SALINITY- can only live in sea water with not too high salt
- CLEANLINESS- water needs low pollution as they are sensitive
- WAVE ACTION- prefer high energy, ensuring freshly oxygenated water
—> helps clean out trapped sediment brings plankton but maybe destroyed of too exposed - EXPOSURE TO AIR- coral die if they are exposed for too long to arise they can only survive and grow at low tide level
Explain why many people live on or close to the coast even though it may be hazardous
Employment of tourism
Leisure activities like fishing
Fresh air
Can’t afford to move
Friends and family
Risk perception
Explain why living on or close to a coast can be hazardous
Loss of garden
Damages to road
Rising sea level
Tsunami
Coastal erosion
Tropical storms
Properties collapse
Slumping
Often occurs in sedimentary rocks trigger by extreme weather
Rocks can fall suddenly to the beach leads to bite shaped chunks are removed from the top of the cliff
There will be a fan shape at the foot of the cliff
Caused by
- winter storm erode the foot of the cliff
- weathering weakens the strength of the cliff
- loosely compacted rocks is permeable, water being absorbed during heavy rain extra weight been given slumping might occur
Explain why living on or close to a coast can be hazardous
Coastal erosion Properties to collapse Damage roads Coastal flooding Tsunami Tropical storms Rocks fall Loss of garden
