Physical Land Scapes Flashcards
How are waves formed
When wind blows over the sea and friction causes surface of water to ripple
What is the fetch
Maximum distance wind can blow across the sea to create a wave
Longer the fetch more powerful the wave
Define swash
Water running up the beach
Define backwash
Water that flows back towards beach
What are constructive waves
Low wave height
Long wave length
Spill wave
Powerful swash so deposit large amounts of sand / pebbles
Weak backwash
Gain beach sediment
What are destructive waves
High wave height
Short wave length
Plunge wave break
Weak swash
Strong backwash
Loss of sediment
What is weathering
Weakening or decay of rocks mostly caused by weather such as rainfall and changes in temp
What are the 4 types of mass movement
Rock fall, mud flow, landslide, rotational slip
Define rock fall
Fragments of rock breakaway from cliff face often due to freeze thaw weathering
Define mud flow
Saturated soil and weak rock flows down slope
Define landslide
Blocks of rock slide down hill
Define rotational slip
Slump of saturated soil and weak rock along a curved surface
What is mechanical weathering
Disintegration of rocks. Piles of rock called scree can be found at foot of cliff
What is chemical weathering
Cause by chemical changes like rainwater which is slightly acidic very slowly dissolves certain rock and minerals
What is biological weathering
Due to flora (plants) and fauna (animals)
Plant roots grown in cracks in rock
Animals burrow into weak rocks
What is freeze thaw weathering
Water collects in cracks or holes in rock
At night water freezes and expands and makes cracks in rock bigger
When temperature rises and ice melts water seeps deposed into rocks
This repeats and eventually fragments of rock may break off
What does prevailing wind do
Makes the direction of waves on an oblique angle where swash pushes sediment up beach and backwash takes it back out to sea.
Because of gravity
This zig zag movement carries sediment up the beach
How are headlands and bays formed
There are alternating bands of more and less resistant rock on the coast
Softer clay is eroded more easily by oncoming waves than hard rock by hydraulic action and abrasion
Resulting in soft rock moving inland and retreating to make a c shape bay and hard rock sticking out creating head land
How does a headland change over time
Waves attack cliff causing faults and cracks because of hydraulic action creating caves
Then cave widens because of abrasion and hydraulic action and solution from waves
Cave then wears away all the way through headland creating a natural arch
Weathering then erodes top of cliff so roof collapses creating tall rock stack
Stack continues to erode until its a stump
How are wave cut platforms formed
Waves break against a cliff
Erosion at high tide land will wear away cliff to form wave cut notch
Over long period wave cut notch will get bigger due to abrasion and hydraulic power undercutting cliff / headland until it collapses and recedes
As this repeats a gently sloping platform called wave cut platform is produced
How are spits formed
Prevailing wind pushes contructive waves up beach at same angle as swash
So sediment is pushed up and dragged back down the beach in long shore drift
This continues leading to mass transportation of sediment until mainland ends where sediment then builds up causing extension of mainland.
Salt marsh can form behind if estuary is present
How are sand dunes formed
Embryo dunes form around obstacle
Develop and become stabilised by vegetation - marram grass adapated to wind and roots get water
In time rotting vegetation adds organic matter to sand making it fertile
Wind can form depressions in sand called slacks where ponds form
How is a bar formed
Swash and backwash bring sediment up the beach due to long shore drift
Bay is then formed as spit grew across the mouth of the bay joining up two headlands via and sand bar
Advantages and disadvantages of sea walls
Ad- stop sea from flooding land, reduces erosive force of waves
Disadvantage- looks obstructive and unnatural, expensive , maintenance costs
Advantages and disadvantages of groynes
Rock and timber structures trapping sediment moved by long shore drift
Ad- creates wider beach as stops long short drift
Disadvantage- interrupting LSD can lead to erosion elsewhere
Advantages and disadvantages of rock armour
Piles of boulders at foot of cliff to trap wave energy
Ad- cheap , easy to maintain
Disadvantage- expensive to transport
Advantages and disadvantages of gaboon’s
Rock filled wire cages reduces force of waves
Ad- cheap to produce, improve cliff drainage
Disadvantage- cages rust within 5 yrs
Advantages and disadvantages of beach nourishment
Sand dredged on beach to create wider beach
Ad- cheap and easy to maintain, blends in
Disadvantage- needs constant maintenance as sand still removed by waves
Advantages and disadvantages of dune regeneration
Marram grass planted to stabilise dunes
Ad- maintain natural environment , good for wildlife
Disadvantage- time consuming to plant marram grass, can be damaged by storms
Advantages and disadvantages of dune fencing
Fences constructed on sea ward side of existing dunes
Ad- little impact of natural systems
Disadvantage- can be unsightly , regular maintenance
Advantages and disadvantages of managed retreat
Sea to over flood over low lying land
Ad- more space for wave energy to be absorbed
Disadvantage- excessive flooding poses risks, not all areas can be used
What are reasons for management at lime Regis
Town built on unstable cliffs
Coasting erodes rapidly due to powerful waves
Properties destroyed
Sea walls broken
What was phase 1 at Lyme Regis
New sea wall
£1.4 million project to stabilise cliffs using large nails to hold rocks together
What was phase 4 at Lyme Regis
£20 million
New 390 metre sea wall
Nailing piling and drainage to provide cliff stabilisation for 480 homes
Positive outcomes at Lyme Regis
New beaches increased visitor numbers
New defences stood up to storms
Negative outcomes at Lyme Regis
New defences spoilt natural coastline landscapes
Increased visitors led to conflict with locals who thing traffic and litter increaed
