Coasts Flashcards
How are waves created?
The wind blows over the sea and makes ripples
These ripples become deeper and form swells
As the sea gets shallower when it approaches land, the bottom of the swell slows down due to friction
The top continues as the same speed
The top crests to form a wave
What is fetch?
The distance the wave has travelled
What is the name of the strongest wind?
The prevailing wind
What is the movement of water up a beach / onto land?
Swash
What is backwash?
The retreat / movement of water back down a beach
What are the two types of wave?
Constructive and destructive
What are the characteristics of a constructive wave?
Shorter fetch, calmer wave, depositional, weak backwash
7 WAVES PER MINUTE
What are the characteristics of destructive wave?
Longer fetch, turbulent, taller, destructive wave, strong backwash, erosional, high energy
14 WAVES PER MINUTE
What are the different types of mass - movement?
Rockfall
Landslide
Mudflow
Rotational slip
What is rockfall?
Freeze-thaw weathering loosens rock, making it more susceptible to gravity
Water enters cracks and expands as it freezes causing the rock to break and fall away
What is a landslide?
Landslides are triggered by periods of heavy rain that saturate the permeable soft rock
This means the top layer of rock is heavier and it slides down the cliff face
What is mudflow?
Mud flow only occurs on steep slopes when periods of heavy rain causes permeable soil to absorb the water and slip over the more impermeable soil beneath it to cause a mudflow
It is very fast and dangerous
What is rotational slip?
Rotational slip is where a landslide rotates as it flows
This leaves behind a deeper indentation and a curved surface, it is also more dangerous and destructive
What types of sub-aerial weathering affect the coastline?
Biological weathering Chemical weathering Salt crystallisation Pressure Release Freeze - thaw Mechanical weathering
How is a beach formed?
Swash and backwash move sediment around
Longshore drift means sediment is carried in at an angle due to the prevailing wind
The sea deposits the sediment when longshore drift is stopped by a head land and a beach is formed
Cliffs nearby provide a source of sediment
Beaches are formed when swash is stronger than backwash
How does a fault become a cave?
Corrosion and hydraulic action widen the weak fault and it becomes a cave
How is an arch formed?
As the protruding headland is eroded from both sides, the thin wall behind the cave falls through.
How is a stack formed?
Weathering weakens the cliff above an arch and the arch grows bigger
Over time, the weight is too much and the arch falls through to leave a stack
How are wave cut notches and wave-cut platforms formed?
The wave erodes the cliff face between the high tide water mark and the low tide water mark
Abrasion and hydraulic action
This cave formed is a wave cut notch
As the cliff above it is unsupported, eventually gravity causes it to fall
The cliff retreats and a notch is formed again etc
The land marking where the cliff used to be is the wave cut plat form
Where is cord grass found?
In the mudflats and low marsh
It is a pioneer plant
What is vegetation succession?
When mudflats turn into marsh uplands over hundreds of years