π Coast Flashcards
What is the coast?
Point at which the land meets the sea
What are the 4 types of coastal erosion?
- Hydraulic action
- Abrasion/ corrosion
- Attrition
- Corrosion
What is hydraulic action?
The sheer force of waves, especially when they trap air in cracks and holes in cliffs. When the wave retreats the air in the crack expands causing a minor explosion.
What is corrasion/abrasion?
Results from large waves hurling beach material at the cliffs
What is attrition?
When the wages cause rocks and pebbles on the beach to bump into each other and break down in size and smooth them over
What is corrosion?
Certain types of rock are dissolved by acids in sea, salt water eg. Chalk and limestone
Describe a wave approaching the coast:
Circular orbit in open water
Friction with the sea bed distorts the circular orbital motion
Increasing elliptical orbit so the top of the wave moves faster
Wave begins to break
Water from the previous wave returns as the wave rushes up the beach
What is swash?
The movement of the wave up the beach
What is backwash?
Movement of the wave back down the beach
What are 3 factors that determine the strength and power of a wave?
- Strength of the wind
- The length of time that the wind blows
- Fetch
The longer and bigger these are will result in bigger and more powerful waves.
What is fetch?
The distance of sea the wind has to cross
What are the 2 main types of waves?
- Destructive waves
- Constructive waves
What is the height of a constructive wave like?
Low in proportion to length
What do constructive waves do to the beach?
Build them via deposition
Describe a constructive waveβs swash and backwash:
Carries material up the beach in a strong swash. Material is then dumped as the weak back wash soaks into sand.
What is a constructive waves swash like?
Strong
What is a constructive waves backwash like?
Weak
When are constructive waves more common?
Summer
What do destructive waves do to beaches?
Destroy beaches (erosion)
What is the height of destructive waves like?
High and frequent in proportion to length
Describe a destructive waves swash and back wash:
Waves hit the beach and the strong back wash removes the material from beach (erosion)
Weak swash
What is a destructive waves swash like?
Weak
What is a destructive waves backwash like?
Strong
When are destructive waves most common?
Winter
What is the rate of erosion on coasts affected by? (8)
Wave type
Fetch
Rock type
Weather conditions
Wind speed
Shape of the coastline
Depositional landforms
Human activity
How are cliffs and wave cut platforms made? Process
- The sea attacks the cliff between high and low tide
- A wave cut notch develops in the zone of erosion between high and low tide
- The wave cut notch gets bigger and deeper through erosion, eg. Hydraulic action. There is a large area of unsupported rock above the wave cut notch
- The unsupported rock collapses and thus the cliff retreats. It leaves a wave cut platform and a new wave cut notch starts. The process repeats again
How are headlands and bays created?
They are caused by differential erosion
What is differential erosion?
Resistant rock and less resistant rock is eroded at different rates.
What is a discordant coastline?
Different bands of rock types run perpendicular to the coast
What is a concordant coastline?
Where the rock type is the same
How are headlands and bays formed? Process
- Headlands and bays are caused by discordant coastlines with perpendicular bands of hard and soft rock
- Wave attack, specifically hydraulic action, causes the cliff to retreat
- Differential erosion occurs where less resistant rock is eroded at a faster rate t o create bays. More resistant rock takes longer to erode forming headlands, where the harder rock sticks out
- The size of the bands of soft rock determines ones the size of the bay. During clam periods, deposition occurs in bays to form beaches
How are headlands eroded? Process
Crack, cave, arch, stack, stump
- The four processes of erosion begin to attack cracks and weaknesses in the headland
- Overtime the crack widens and deepens forming a sea cave
- As erosion continues the cave eventually erodes straight through the headland forming an arch
- As the arch gets larger, the rock above becomes unsupported and eventually falls, leaving behind a stack
- The base of the stack gets eroded and will eventually topple over leaving a stump remaining
This process repeats itself with a new cave being formed on the new headland
What is weathering?
The breakdown or erosion of rocks at the Earths surface by the action of rainwater, extremes of temperature and biological activity
What are the 4 types of weathering?
- Biological
- Wind, rain and waves
- Freeze thaw
- Chemical
What is biological weathering?
Roots find their way into cracks and expand the gaps forcing the rock to widen, become weaker and pieces fall off. Anima,s burrowing or walking over the surface of the ground can gradually wear it away or weaken it.
What is wind, rain and wave weathering?
The wind can blow tiny grains of sand against a rock which wears it away. Rain and waves can also wear away rocks over long periods of time.
What is freeze thaw weathering?
Water expands slightly when it freezes into ice. The formation of ice can break rocks. If water gets into a crack in a rock, freezes, expands, and pushes the drain further apart. When ice later melts, start can get further into the crack and the process repeats. This weekends the Rick, making the crack become so big that pieces fall off.
What is chemical weathering?
Chemical reactions breakdown the bonds holding the rocks together causing them to fall apart forming smaller pieces. Examples of this are oxidation, hydrolysis and carbonation