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Edexcel coastal landscapes summary notes
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Edexcel coastal landscapes summary notes
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The littoral zone is an area of shoreline where land is subject to wave action. It is divided into the offshore, nearshore,foreshore and backshore and includes a variety of coastal types and is a dynamic process. Waves, currents and tides
determine much of the dynamics in the zone. Waves and currents bring sediment from the sea. Constructive
and .destructive waves occur on the foreshore and nearshore causing differing degrees of deposition and erosion which
form different coastal types. Rocky coastline subject to destructive waves have high relief and usually have resistant
geology. Sandy coastlines form due to constructive waves which have low relief and have less resistant geology. Estuarine
coastlines may form due to high levels of deposition and in low energy environments. The tidal range also determines
where this wave action takes place. Offshore currents and LSD may move sediment along the coast. Weathering and mass
movement occur on the backshore. The littoral zone can also be affected by human activities like dredging riverbeds to
make them deeper for shipping, offshore dredging for sand and gravel for construction or the building of defences which
decrease erosional forces and flooding.
Littoral cells are made of sources, transfers and sinks. There are 11 sediment cells in England and Wales. Theoretically,
these cells are regarded as closed systems due to large barriers and little transfer between them, however, under certain
conditions, transfers between main littoral cells may take place. The sediment budget should be balanced as erosion in
one source known as the source is balanced by deposition in another known as a sink. The sediment budget can be useful
in assessing coastal changes and the effects of coastal management schemes. The sediment cells are a dynamic processes
and negative feedback and positive feedback loops can occur. Negative feedback loops maintain the balance whilst
positive feedback changes the balance until a new equilibrium is reached. Transfers like LSD, waves, tides, currents and
winds act in littoral cells. LSD transports erosion of cliffs to the backshore. Waves transport sediment from onshore
currents to foreshore deposition landforms. Tides brings river sediment to form nearshore depositional landforms and
currents bring aeolian sediment from land to form offshore sediment deposition. Winds carry sediment from subaerial
processes.
Valentines classification suggests advancing coastlines are due to deposition and emergence, whilst retreating coastlines
are due to submerging and eroding coastlines
Coastal morphology is largely determined by geology and wave action
Geological structure refers to the level of geological resistance which is determined by the degree of consolidation and the
number of bedding planes, joints, folding and faults. This is influenced through tectonic activity which can cause complex
folding patterns like Stair Hole in Lulworth. Pressure and cooling create joints and faults in the rock which create points of
weakness. The dip of the rock layer which is the tilt from the horizontal is very important as a downward dip makes rock
more susceptible to mass movement, but landward dip exposes it to weathering and erosion which may cause an irregular
profile. These profiles may cause protrusions and indentations which are weak points that can be eroded.
Folding is very important and the direction of this causes either discordant or concordant coastlines. Discordant coastlines
form where the folding is at right angles to the coast creating headlands of more resistant rock and bays or inlets where
there is fewer resistant rocks. Once this occurs, wave action is influenced. Bays are semi-circular and wave energy
dissipates meaning waves lose energy and deposit a bay head beach. Then waves refract on the headlands and
concentrates their energy on them, increasing the rate of erosion. An example of this is in South West Ireland
Concordant coastlines may form when rock folding is parallel to the coast. The more resistant rocks form elongated
islands while the less resistant rocks form long inlets or coves. Example is the eastern coast of the Adriatic Sea.
Wave action refers to the size, shape, fetch, direction of prevailing winds and depth of near and offshore areas. Short
fetches and small sized waves form low energy environments. Here, a haff coastline may form where there is the
deposition of muds and sands. Large lagoons are found behind the deposits parallel to the shore. Like the Baltic Sea
coastline in Poland where a large lagoon has formed behind the Vistula spit.
, Coastal recession is determined by bedrock lithology and factors which affect differential erosion
Bedrock lithology are rocks making up the base of the Permeability of rock is the number of cracks, joints and
land. 3 types: igneous rock, metamorphic rock and bedding planes which affects the amount of water which
sedimentary rock. Igneous rock is cooled magma and are can pass through. Rocks with a high degree of spaces
more resistant to erosion and weathering than the other allow more water to pass through increasing erosion.
2 which were instead formed underneath oceans. Rocks like granite are impermeable meaning they have
Igneous rock can be granite or basalt and have very slow very slow rates of erosion.
erosion of 0.1cm/ year. Metamorphic rocks like marble
are formed from igneous and sedimentary rock Greater presence of water may encourage weathering
subjected to intense heat and pressure. They also have and mass movement. Unconsolidated rock like porous
slow erosion. However, sedimentary rock like limestone rock may cause slipping and slumping as water
erodes 2.5cm/ year and are very porous and loosely percolates through the upper layer, creating instability
consolidated. Solubility of rock will determine its vulnerability to
chemical weathering like carbonation and hydrolysis.
Lithology of rocks on top of bedrock like glacial till and Sedimentary rocks like limestone are very soluble and
tephra may affect recession as well. Glacial till is a becomes dilute carbonic acid by absorbing CO2 from the
mixture of clay and stones left behind by retreating ice air and slowly dissolved into bicarbonate which is carried
sheets creating vulnerable cliffs like along Holderness away in solution. Seawater also contains CO2 from the
coast. In some places, receding 1m a year. Recession is atmosphere and dissolves limestone create pits and
fastest from new islands formed by tectonic activity like pinnacles. In hydrolysis, water chemically combines with
islands of tephra can recede at 40m a year. igneous rocks like granite to produce clay and salt.
The importance of vegetation
1. Bind together the soil and stabilise the loose material
Plant succession sequence helps this process. Pioneer plants first establish themselves. These differ
depending on coastal ecosystem. Halophytic plants like samphire establish in haloseres or salt marshes and
can survive salty conditions. Xerophytic plants like marram grass in psamosseres or sand dunes can survive in
dry conditions. These pioneer plants encourage further growth and development. Add nutrients to the soil
through decayed plants known as humus. They retain moisture and reduce saltiness and stabilise material so
new plants can establish themselves
2. If completely submerged, they form a protective barrier over the ground to prevent further erosion of material
3. They reduce windspeed which reduces the rate of erosion
Coastal ecosystems
1. Psamosseres
2. Haloseres
Psamosseres are sand dunes and they absorb the impact of storms. They are common in low energy environments like
estuaries and sheltered bays. Sand dunes form where there is plentiful sand, large area for sand to dry, onshore winds to
blow the sand towards the land and obstacles to trap the sand. Psamosseres have 3 stages in their development. Embryo,
yellow and grey dunes. 50 – 100 years is enough time for a significant dune sequence to develop. Embryo dunes form first
as sand starts to accumulate around small obstacles like ridges and wood. Pioneer plants start colonising these
accumulations and hold sand together. Plant succession happens and traps more sand. Yellow dunes are the highest and
form a ridge near the dune front with marram grass but are subject to alteration by wind and waves. Slacks may hold
seawater from storm conditions allowing more plant growth from plants like marsh orchids. Grey dunes form as their
humus content is greater and climax vegetation is either pine (high acidity) or oak forest (shell deposits neutralise the soil)
Haloseres are salt marshes and they absorb coastal flooding water. The form in low energy environments of estuaries and
sheltered bays. Tides bring sediment in and out. River currents bring fine muds and silts and deposit them at the sides of
the estuary. Flocculation occurs which clumps the muds and silts together. Once deposited, they are colonised by algae.
Algal stage binds together muds and silts so pioneer plants like halophytic plants of samphire can inhabit them. These
change the conditions by trapping more sediment to build the salt marsh higher so more plants can colonise. Many
invertebrates live in the muds and many plants are grazed by migrating wildfowl like Brent geese.
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