Coastal landscapes Flashcards
A system
A set of interrelated objects comprising components and processes that are connected together to form a working unit.
Coastal landscapes
They store and transfer energy (kinetic, potential and thermal ) on time scales.
Open system ~ energy and matter can be
transferred from neighbouring systems as an input and transferred to neighbouring systems as an output.
Has 4 components:
- inputs
- stores
- flows
- outputs
input examples
- kinetic energy from wind and waves
- thermal energy from the heat of the sun
- potential energy from the position of material on slopes
- weathering and mass movement from cliffs
- material from marine deposition
A process
Consists of stores and flows.
store e.g ~beach sediment accumulation
flows e.g ~ movement of sediment along a beach by longshore drift.
output examples
- marine erosion
- wind erosion
- evaporation
Equilibrium & dynamic equilibrium
Equilibrium ~ the inputs and outputs of a system are equal.
If this is disturbed , the system produces its own response to this to self regulate. This is known as dynamic equilibrium and is an example of negative feedback.
sediment cells
A stretch of coastline within which the movement of sediment , sand and shingle is largely self contained.
A closed system ~ however not completely due to variations in wind direction and tidal currents , causing sediment to be transferred.
Boundaries ~ determined by the topography and shape of the coastline.
The only inputs into the cell come from the erosion of the land or sea bed.
- There are also many sub -cells of a smaller scale existing within the major cells.
5 physical factors influencing coastal landscape
- wind
-waves
-tides
-geology
-currents - these vary in terms of their spatial (from place to place) and their temporal (over time)
-they can be interrelated and influence each other.
wind
- wave action is the source of energy for coastal erosion and sediment transport.
- Generated by the frictional drag of winds moving across the ocean surface.
- The higher the wind speed , the larger the fetch, the larger the waves and the more energy they possess.
ONSHORE WINDS ~ drive waves towards the coast.
OBLIQUE WINDS ~ cause waves to move obliquely, generating longshore drift.
Fetch ~ the distance over which wind travels over open water
oblique
Neither parallel nor at right angles to a specified or implied line ; slanting.
longshore drift
A geological process that moves sediment along a coastline in a zig zag pattern.
Generated by waves approaching obliquely due to wind blowing at an oblique angle.
wave development and breaking
- a wave enters shallow water
- friction with the sea bed increases
- the wave slows down as it drags along the bottom
- the wavelength decreases, and successive waves begin to bunch up.
- the wave increases in height
- eventually , the wave plunges and breaks onto shoreline.
wave components
Crest ~ the highest part of a wave.
Wave height ~ vertical distance between the crest and the trough.
Wavelength ~ horizontal distance between two adjacent troughs or crests.
Trough ~ lowest part of a wave.
wave frequency
&
wave period
wave frequency ~ the number of wave crests passing a point each second.
wave period ~ the time required for the wave crest at one point to reach the second point.
Formula to determine the amount of energy in a wave in deep water
P=H2T
P ~ power (Kw per metre of wave front)
H ~ height (metres)
T ~ time interval (between wave crests in seconds)
constructive wave
- low wave height
- long wavelength, therefore a low frequency.
- strong swash and a weak backwash
- This is because the backwash returns to the sea before the next wave , meaning the next swash is uninterrupted and retains its energy.
- leads to the build up of beach material to form depositional landforms
- waves spread a long way up the gently sloping beach
destructive wave
- steep wave front
- short wavelength , therefore a high frequency.
- weak swash and a strong backwash
- leads to the removal of beach material to form erosional landforms
- wave does not travel far up the steep beach as energy is directed downwards.
swash
- the movement of water up a beach
- movement is driven by the transfer of energy that occurs when the wave breaks
- the speed of the swash decreases as it travels further up the beach due to friction and the uphill gradient of the beach.
back wash
- the movement of water down a beach
- movement is driven by gravity and always occurs perpendicular to the coastline.
Beach gradient and wave type
These have and important and complex relationship.
HIGH ENERGY WAVES ~ remove material from the top of the beach to the offshore zone, reducing the beach gradient.
LOW ENERGY WAVES ~ build up the beach face , steepening the profile.
This is due to :
- wave steepness
- angle of waves
- sediment particle size
Tides
The periodic rise and fall of the sea surface , produced by the gravitational pull of the moon and sun.
- The moon pulls water towards it
- This creates a high tide
- There is a compensating bulge on the opposite side of the earth.
-At locations between the two bulges there is a low tide.
-As the moon orbits the earth the high tide follows it.
When do the highest and lowest tidal ranges occur
HIGHEST TIDES ~
- occur when the moon , Earth and sun are aligned and so the gravitational pull is the strongest.
- This causes spring tides with a high tidal range
LOWEST TIDES ~
- When the moon and sun are at right angles to each other the gravitational pull is weak.
-Causes neap tide with a low tidal range
Tidal range
The vertical difference in height between high tide and low tide.
Influences:
- where wave action occurs
- weathering processes
- impact of processes between tides ( e.g scouring)
Enclosed sea ~ tidal ranges are low so wave action is restricted to a narrow area of land.
Funnelled coast ~ tidal range can be as high as 14 metres.
Geology
Refers to the lithology and structure of the coast line.
