Deposition And Waves 🌊 Weathering And Landslide Flashcards
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Constructive waves 🌊
Weak backwash
Strong swash
Builds up beach
Destructive waves
Short wave length but high frequency 10-14
Weak swash
Strong back wash
Remove sediments of the beach
Why are constructive waves, constructive waves
They have low wave frequency but high wave length
These waves build up the beach because it uses all of its energy in the swash and moving materials up the beach
energy is from storms hundreds of miles away
Why are destructive waves destructive waves
Sufficient power to erode beach
Weak swash as little material is left
Features of a destructive wave beach
Caves arches stacks stumps will be created
removal of the sand and land
Longshore drift
but if they approach at an angle measurements will be moved along the beach as a ‘zigzag ‘pattern is it called longshore drift
What is longshore drift responsible for
longshore drift was responsible for a number of important coastal landforms including beach spits
Movement on a Beach depends on what
The movement of sediment on a beach depends on the direction the waves approach the coast
where the waves approach ‘head on ‘ sediments is simply moved up and down the beach
Transport on to the beach
Load is transport in the by waves
the larger the load the greater the velocity is needed to transport it
How is the load carried
the lightest load is carried in suspension or saltation
a heavy load is moved out of the Beach by traction
What
Is deposition
Deposition results in more sediments staying on the beach than is taken away by the backwash
What causes deposition
Low energy sheltered bays constructive ways are the main reason
large sources of sediments updrift e.g. rapidly eroding Headland where engineered structures like groynes trap sediment on the updrift side
Where does Coastal deposition take place
This takes place in areas where the flow of water slows down
Where does coastal deposition take place
Waves lose energy in sheltered bays and where water is protected by spit or bars hear sediments can no longer be carried or moved and is therefore deposited
What is weathering
Weathering is the breaking down of rocks it is caused by day-to-day changes in the atmosphere extremes of temperature and rainfall
What is cliff collapse
It’s caused by weathering this weakens or decays rocks in the original place or close to the ground surface
Types of cliff collapses
Mechanical chemical biological
Mechanical cliff collapse
Disintegration of Rocks when this happens piles of rock fragments scree can be found at the foot of cliff
Chemical weathering
Rainwater which is acidic this dissolve types of rocks e.g. limestone
Biological weathering
E g plants and animals plant roots grow in cracks in the rocks animals such as rabbits Burrow into weak rock e.g. sand
Freeze t h a w
Water enters holea night water freezes it expands then it thaws and create cracks
Salt weathering
Sea water has salt water evaporates and leaves salt crystals crystals grow and expand
this causes pressure and cracks
Chemical weathering .2
Remember the acidic water touches something alkaline e.g. limestone
Mass movement
Downward movement or sliding of material under the influence of gravity
Mud slide
Mud slide are usually wet rapid and tend to occur where slopes are steep over 10 degrees
Where do mudslide take place
they usually happened where vegetation cover is little so it cannot hold the soil in place they happen after a period of heavy rain at the base of mudslide the soil spreads out to make a lobe
Slumping
Slump has a concave slip plane so material is rotated backwards into the cliff face as it slips
An example of slumping
Barton on Sea Hampshire the cliff is slumping at up to 30 cm per day
Mudslide case study example
Monmouth beach lyme Regis Dorset
Rock slide
A rockslide is where a large amount of rock slides down a cliff
this happened along fairly straight slip plane where rocks fall as a block which maintains contact with the cliff the leading edge of the slide collect as pile of rocks on the beach or in the sea
Where does landslides happened in
The cliffs in the Jurassic Coast near Durdle Door in Dorset has suffered from large landslide in recent years
Why do landslidesHappened
Slides it happened on steep Cliff all weaken by weathering
Heavy rain infiltrate the soil and circulate down into the rock
the now heavier mass Falls away along at the slip plane which is a line of weakness such as faults or bedding clean a slide happens quickly It Starts by tearing away vegetation on the top edge of the cliff
once the slide has begun the descent is aided by lubrication from the wet rocks below
