Physical Land Scapes Flashcards
(36 cards)
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
