Coasts Flashcards
What System is a coast?
Open System
Sediment cells
. Coasts split into sections, often bordered by prominent headlands
Dynamic equilibrium
The balance of inputs and outputs in a natural system
Dynamic equilibrium in a sediment cell
Where inputs and outputs are in a constant state of change but remain in balance
Dynamic equilibrium :longterm and short term
. Can be interrupted by human intervention ( hard engineering)- long term
. Can be interrupted by natural variations - short term
Inputs
Matter and energy entering the system from outside sources
Inputs examples
. Marine- waves and tides
. Atmosphere- sun, air pressure, wind speed and direction
. Humans- pollution, Defences
Outputs
Matters and energy moving from the system to outside sources
Outputs example (4)
. Ocean currents
. Rip tides
. Sediment transfer
. Evaporation
Stores/ sinks examples (6)
. Beaches
. Sand dunes
. Spits
. Bars
. Headlands and Bays
. Wave cute platform
Etc
Stores/ sinks
Individual elements of part of a system
Transfer/flows
the relationship between inputs, outputs and stores in a system
Flows/ transfers (5)
. Transportation
. Mass movement
. Weathering
. Erosion
. Deposition
Energy
driving force in a system
Energy examples
Wind
Waves
Tides
Currents
Positive feedback
The system becomes more unstable as it increases/ speeds up
Negative feedback
The system becomes more stable as it decreases/ slows down
Constructive waves (6)
. Strong Swash
. Weak Backwash
. Long wave length
. Low frequency ( 6-8 waves per minute)
. Flat and low
. Causing deposition
Destructive waves (6)
. Large height
. Short wavelength
. Strong backwash
. Weak swash
. High frequency( 13-15 waves per Minute)
. Causing erosion
Sediment budget
. The use of inputs, outputs ,stores and transfers to asses the gains and losses of sediment within a sediment cell
Tides
. The changes of sea levels due to gravitational effects from moon and the sun
Tidal ranges
The upper and lower limits of erosion and deposition ( the difference between high tide and low tide)
Tidal surges
Narrow neck of water, tides can be funnelled and increase in height and range
Highest high tide and lowest low tide3s
. when the sun and moon are in alignment, so gravitational forces work with each other - spring tides
Highest low tides and lowest high tides
. when the sun and the moon are perpendicular to each other so gravitational forces work against each other -neap tides
Currents
The seasonal movement of water in the seas and oceans
High energy coastlines (4)
. Strong steady prevailing winds, creating high energy waves
. Rate of erosion> Tate of deposition
. Typical landforms: headlands, cliffs and wave cut platforms
. Eg north Cornish coast
Low energy coasts (4)
. Coastlines where wave energy is low
. Rate of deposition > Rate of erosion
. Typical landforms: beaches and spits
. Eg the Baltic Sea
Backshore
Is the area lying between the high water mark and the landward limit of marine activity
Foreshore
Area lying between high water mark and low water mark
Inshore
Area between the low water mark and the point where waves have no influence on the land beneath them
Offshore
Area beyond the the point where waves impact the sea bed
Wave refraction (6)
. Waves refract onto the headland
. The waves become higher, steeper with shorter wave length
. High energy waves concentrated on the headland, increasing erosion
. Waves refract out onto bay
. Waves in the deep water are still moving forward so the waves bend
. Low energy waves concentrated in the bays, increasing deposition
Longshore drift (3)
( littoral drift)
. Prevailing wind approaching the beach at an angle
. Sediment is dropped back out to sea
. Picked up by the prevailing wind and pushed back up the beach before it’s then dragged back out to sea
. Rip currents (3)
. Strong currents moving away from the shoreline
. Sea water is piled along the coastline by incoming waves
. Current runs parallel to coast before flowing to breaker zone, at a headland
Sub-aerial processes (2)
. Weathering
. Mass movement
Marine processes ( 3)
. Erosion
. Deposition
. Transportation
Simple spits
. Longshore drift deposits sand and shingle across the river mouth, leaving a bank of sand and shingle sticking out to sea ( a straight spit that grows out roughly parallel to the coast is called a simple spit )
Compound spit
. Changes in wind direction lead to curved end
. This can happen multiple times creating multiple recurved ends
A bar
Formed where a spit grows across a bay. Behind the bar forms a lagoon where water is trapped. Over time the lagoon will be filled up with Silt and may gradually form salt marshes
Mudflats
. Found at the edge if the permanently submerged marine zones
Eustatic change
When sea level itself rises or falls (global)
Isostatic change
When land rises or falls relative to the sea (local )
What causes eustatic change?
. An increase in temperature causing melting ice sheets, which increases sea level
. A decrease in temperature causing more precipitation to fall as snow. This increases the volume of water stores in glaciers and so reduces the volume of the sea, decreasing sea level
. Changes in earth’s tectonic movement alters the earths shape and volume of ocean basin e.g sea floor spreading increases the volume of basin so decreases sea level
What causes Isostatic change ?
. Slow uplift of land can continue for thousands of years after the weight of retreating glacier has gone
. Subsidence of land due to shrinkage after abstraction of ground water e.g drainage of marshland
. tectonic crustal processes: one plate is forced beneath another at a plate margin
Submergent coastlines
Stretches along the coast have been inundated by the sea due to eustatic changes
Emergent coastlines
Stretches along the coast have been exposed by the sea due to Isostatic changes
Submergent landforms
. Rias
. Fjords
. Dalmatian coastlines
Emergent landforms
. Raised beaches
. Marine platforms
Land slides (6)
. Shifting material downhill due to gravity
. In coastal areas, cliffs are undercut by wave action which causes an unsupported overhang and collapses
. Slides- material shifts in a straight line
. Slumping- material shifts with rotation
. Unconsolidated rocks are prone to collapse as there is little friction
. Runoff can erode fine particles and transport them downslope
Mudflows (4)
. Water gets trapped in rocks, increasing water pressure which forces rock particles apart and leads to slope failure
. Unconsolidated rock is prone to collapse due to little friction
. Heavy rainfall can saturate Unconsolidated rock, further reducing friction and making it more likely to collapse
. Runoff can erode fine particles and transport them downslope
Mechanical Weathering (3)
Freeze thaw-
.water enters cracks in the rocks which the freezes (temp below 0 degrees)
. the water expands by almost 10% meaning ice occupies more space and so exerts pressure surrounding the rock
. As process repeats, the crack widens, breaking the rock
Biological weathering
breakdown of rocks by the Action of vegetation and coastal organisms
. marine organism such as piddocks (a shell fish ), have specifically adapted shells that enable them to drill into solid rock
Chemical weathering
Carbonation
. When carbon dioxide dissolves in rainwater makes a weak carbonic acid. This reaction with calcium carbonate in rocks like limestone and chalk creates calcium b carbonate, which dissolves easily in water
Littoral zone
Area of land between the cliffs or dunes and offshore area beyond the limit of the waves
Wave formation (4)
. Winds move across surface of the water
Causing frictional drag ( ripples and waves are created)
. the sea bed becomes shallower towards the coastline and orbit of water particles becomes more elliptical, leading to horizontal movement of the waves
. The wave height increases but the wave length and wave velocity decreases
. This causes water to back up behind the wave until wave breaks and surges up the beach
Factors effecting wave energy
. Strength of wind- the larger the pressure between two areas, the stronger the wind
. Duration of wind- if wind is active for longer periods of time, then the energy of the waves build up and increase
.Size of Fetch- the larger the distance over the wind blows the more powerful the waves will be
Types of waves in a coastal environment
. Constructive waves dominate but destructive waves dominate in winter
. Constructive waves may become destructive waves if a storm begins
. Climate change may increase storm frequency within the UK
. Coastal management may affect the type of waves that occur
Negative feedback ( beaches and waves)
. constructive waves causes deposition on the beach, which leads to the beach profile becoming steeper
. Steeper beaches favour the formation of destructive waves, which are then more likely to occur
. Destructive waves erode the beach, reducing the beach profile and leading to the formation of constructive waves
. Constructive waves occur more frequently in the summer, meaning that beach profile is more gentle and steeper durning the winter where destructive waves are more common
Négative feedback
. Due to different rock strengths, erosion leads to the formation of headlands, where resistant rock exists and bays where unconsolidated rocks and clays are dominant
. This increases the forces of erosion in headlands and reduced erosion in bays.
. Headlands are worn away which again increases erosion within the bays
Wave Quarrying
When breaking waves hit the cliff face to directly pull away rocks or remove smaller weathered fragments
Factors effecting erosion
. Waves
. Beach size
. Activity of sub aerial processes
Rock armour ( hard engineering)
. Coast effective - P
. Rocks are sourced from elsewhere so do not fit with the local geology- N
. A hazard if climbed upon- N
Marsh Creation ( soft engineering)
. Created and important wild life habitat- P
. Farmers lose land and may need to compensate as a result- N
Sea walls
. Effective erosion prevention- P
. Promenades has tourism benefits-P
. Visually unappealing- N
. Expensive to construct
Integrated coastal zone management ( ICZM)
. ICZM recognises that coastal management must be sustainable
. Involves all stakeholders and plans for the long term
. In 2013, the EU adopted a new initiative which promotes the use of ICZM
Shoreline management Plans (SMP’s)
. Hold the line- defences used to maintain the current position of the shoreline
. Managed retreat- engineering techniques are used to allow the coastline to advance inland and create its own natural defences
. Advance the line- defence are built to try and move the shoreline seawards
. No active intervention- the shoreline is exposed to natural processes
Rias
When rising sea levels flood narrow inlets and river valleys. They are deeper at the mouth of the inlet, with the water depth decreasing further inland
Fjords
when rising sea levels flood deep glacial valleys to create natural inlets and harbours eg in New Zealand
very straight and narrow and has very steep sides
Dalmatian coasts
when valleys running parallel to the coast become flooded as a result of sea level changes, eg Croatia
how does tidal Range link to sub-aerial weathering?
Determining spatial limits and the length of time the littoral zone is exposed to sub aerial weathering
Wave cut platform ( 4)
. Sea erodes the land so cliff retreats due to action of waves and weathering
. This forms a wave cut notch at the high water mark which eventually develops into a cave
. Rock above becomes unstable and collapses
. Wave cut platform is
formed
Headlands and bays (2)
. Bands of hard rock and soft rock at right angles to the shoreline
. Soft rock erodes quickly forming a bay, the hard rock erodes slowly and sticks out as a headland.
Spits (5)
. Spits are formed when the coast suddenly changes direction
. Longshore drift continues to deposit material across the river mouth leaving a bank of sand and shingle
. A straight spit that grows parallel to the coast is called a simple spit
. Changes in dominant wind and wave direction may lead to spit having curved end ( recurved end). Over time this can create compound spits
. The area behind this develops into mudflats and saltmarshes
Offshore bars and tombolos (4)
. Spit joins two headlands together and a bar is formed
. A lagoon forms behind the bar
. Some bars form off the coast when material moves towards the coast( at sea level rise)- offshore bars
. Bar connects the shore to an island is called tombolo e.g St Ninian’s Isle
Sand dunes (4)
. Sand deposited by littoral drift
. Sand trapped by berms is colonised by plants and grasses.
. The vegetation stabilises the sand and encourages more sand to accumulate forming embryo dunes
. Over time, older dunes move inland- mature dunes can reach 10m in height
Estuarine Mudflats and salt marshes (3)
. Silt and mud are deposited by the river tide- mudflats develop
. Mudflats colonised by vegetation that survived high salt levels and long periods of submergence by tides
. Plants trap mud and silt creating exposed salt marshes between tides
Barrier Islands/ beaches (5)
. Sand runs parallel to the shore that is detached.
. Form in areas with large amount of sediment, gentle slopes offshore, powerful waves and small tidal ranges
. Not clear how it is formed but scientists say it was formed after last ice age which caused rapid sea level rise.
. Another theory is that islands where originally bars attached to the coast which is eroded into sections causing beaches.
. Lagoon formed behind barrier island eg in Horn Island in Mississippi, east coast of USA
Raised beaches
. the fall of sea level leaves beaches above high tide mark
. sea level fall exposes wavecut platforms, leaving them raised above their former level
. The cliffs above the raised beaches are no longer eroded by the sea, so they are slowly covered by vegetation ( relict cliffs)
. these raised features are degraded overtime
sea level change
. around 20,000 years ago, sea levels have been rising
.sea levels have increased in about 235mm
