Essential Notes Flashcards
Is the coast an open or closed system?
Open
What are different sections of the coast known as?
Sediment cells
What are sediment cells bordered by?
Prominent headlands
What is the movement of sediment like within sediment cells?
The movement of sediment is almost contained and the flows of sediment act in dynamic equilibrium
Why might the dynamic equilibrium of a sediment cell be upset in the long-term?
Because of human intervention
Why might the dynamic equilibrium of a sediment cell be upset in the short-term?
Natural variations may interrupt it
What is found within each sediment cell?
Smaller subcells
Inputs
May refer to material or energy inputs
What are the main three areas of inputs at the coast?
- Marine
- Atmosphere
- Humans
What do marine inputs include?
Waves, tides, salt spray
What do atmospheric inputs include?
Sun, air pressure, wind speed and direction
What do human inputs include?
Pollution, recreation, settlement, defences
Outputs
May refer to material or energy outputs
Examples of outputs
- ocean currents
- rip tides
- sediment transfer
- evaporation
Stores/sinks
Refers to the stores and sinks of sediment and material
Examples of stores and sinks
- beaches
- sand dunes
- spits
- bars and tombolos
- headlands and bays
- nearshore sediment
- cliffs
- wave-cut notches
- wave-cut platforms
- caves
- arches
- stacks
- stumps
- salt marshes
- tidal flats
- offshore bands and bars
Transfers/flows
The processes that link the inputs, outputs and stores in the coastal system
Types of transfers/flows
- wind-blown sand
- mass movement processes
- longshore drift
- weathering
- erosion
- transportation
- deposition
Transfers/flows: erosion examples
- hydraulic action
- corrosion
- attrition
- abrasion
Transfers/flows: transportation examples
- bedload
- in suspension
- traction
- in solution
Transfers/flows: deposition examples
- gravity settling
- flocculation
Energy
The power and driving force behind the transfers and flows in the system
Types of energy sources
- wind
- gravitational
- flowing water
Give some sediment sources
- rivers
- cliff erosion
- wind
- glaciers
- offshore
- longshore drift
Sediment sources: rivers
- account for majority of sediment in the coastal zone
- sediment may be deposited in estuaries, which are brackish and important wildlife habitats
Sediment sources: cliff erosion
- very important in areas with unconsolidated cliffs that are eroded easily
- most erosion occurs during the winter months due to more frequent storms
Sediment sources: wind
- the wind is a coastal energy source and can cause sand to be blown along or up a beach
- sediment transport by winds may occur where there are sand dunes, or in glacial and desert environments which provide sediment inputs
Sediment sources: glaciers
- glaciers can flow directly into the ocean, depositing sediment that was stored in the ice when they calve
Sediment sources: offshore
- sediment is transferred to the coastal zone when waves, tides and currents erode offshore sediment sinks, such as offshore bars. The sediment is transported onto the beach, helping to build up the beach
Sediment sources: longshore drift
- sediment is moved along the beach, due to prevailing winds, which alter the direction of the waves
- this allows sediment to be transported from one section of coastline (as an output) to another stretch of coastline (as an input)
Give two factors that can disrupt the state of dynamic equilibrium at the coast
- human actions
- natural variation in the system
What is the littoral zone?
The area of land between the cliff’s or dunes on the coast and the offshore area that is beyond the influence of the waves
Why is the littoral zone constantly changing?
Because of short-term and long-term factors
What short-term factors impact the littoral zone?
- tides
- storm surges
What long-term factors impact the littoral zone?
- changes in sea level
- human intervention
What is the primary source of energy for all natural systems?
The sun
What is the main energy source at the coast?
Waves which are formed offshore
What has direct influence on the formation of waves?
The sun
What factors affect wave energy?
- strength of the wind
- duration of the wind
- size of the fetch
Factors affecting wave energy: strength of the wind
The larger the pressure gradient between the two areas, the stronger the winds. As waves are caused by the wind, stronger winds also mean stronger waves.
Factors affecting wave energy: duration of the wind
If the wind is active for longer periods of time, then the energy of the waves will build up and increase.
Factors affecting wave energy: size of the fetch
The fetch is the distance over which the wind blows and the larger it is, the more powerful the waves will be.
What are the two wave types?
Constructive and destructive waves
Constructive waves
Act to build up and create a beach, increasing its size
Destructive waves
Act to remove the beach and decrease its size
How might the type of waves in a coastal environment vary?
- in summer, constructive waves dominate, but destructive waves dominate in winter
- constructive waves may become destructive waves if a storm begins
- climate change may increase the storm frequency within the UK
- coastal management may affect the type of waves that occur
Give another key source of energy in coastal environments
Gravity
What is the difference in height between the tides known as?
Tidal range
Where does tidal range tend to be the largest?
In channels such as river estuaries
What type of tide creates the largest possible tidal range?
A spring tide
What type of tide creates the smallest possible tidal range?
A neap tide
Spring tide
When the sun, moon and earth are in alignment
Neap tide
When the sun and the moon are perpendicular to the earth
Rip currents
- rip currents are powerful underwater currents occurring in areas close to the shoreline on some beaches when plunging waves cause a buildup of water at the top of the beach.
- the backwash is forced under the surface due to resistance from breaking waves, forming an underwater current.
- rip currents are an energy source in a coastal environment and can lead to outputs of sediment from the beach area.
What type of coastlines are more powerful waves associated with?
High-energy coastlines
What type of coastlines have a large fetch?
High-energy coastlines
What type of coastlines are less powerful waves associated with?
Low-energy coastlines
High-energy coastline characteristics
- occur in areas where there is a large fetch
- typically have rocky headlands and landforms + fairly frequent destructive waves
- these coastlines are often eroding, as the rate of erosion exceeds the rate of deposition
Low-energy coastline characteristics
- less powerful waves
- occur in sheltered areas where constructive waves prevail
- often fairly sandy areas
- there are landforms of deposition, as the rates of deposition exceed the rates of erosion
Wave refraction
Process by which waves turn and lose energy around a headland on uneven coastlines. The wave energy is focused on the headlands, creating erosive features in these areas. The energy is dissipated in bays, leading to the formation of features associated with lower-energy environments such as beaches.
What are the main processes of erosion?
- corrasion
- abrasion
- hydraulic action
- corrosion (solution)
- wave quarrying
Corrasion
Sand and pebbles are picked up by the sea from an offshore sediment sink or temporal store and hurled against the cliffs at high tide
Abrasion
Sediment is moved along the shoreline, causing it to be worn down over time
Hydraulic action
As a wave crashes onto a rock or cliff face, air is forced into cracks, and the high pressure causes the cracks to force apart. Bubbles found within the water may implode under the high pressure, creating tiny jets of water that, over time, erode the rock. This erosive process is cavitation.
Corrosion (solution)
The mildly acidic seawater can cause alkaline rock, such as limestone, to be eroded.
Wave quarrying
This is when breaking waves hit the cliff face to directly pull away rocks from a cliff face or remove smaller weathered fragments.
What factors affect coastal erosion?
- waves
- beach size and presence
- activity of subaerial processes
- rock faults
- rock lithology
Where is erosion based?
It can be marine or land based
What is coastal transportation responsible for?
Transferring sediment within a sediment cell and between other sediment cells
What are the 4 main processes of transportation?
- traction
- saltation
- suspension
- solution
Traction
Large, heavy sediment rolls along the seabed, pushed by currents
Saltation
Smaller sediment bounces along the seabed
Suspension
Small sediment is carried within the flow of the water
Solution
Dissolved material is carried within the water
What is the process of longshore drift?
- waves hit the beach at an angle determined by the direction of the prevailing wind
- the waves push sediment in this direction and up the beach in the swash
- this wave then carries sediment back down the beach in the backwash
- this moves sediment along the beach over time
When does deposition occur?
- when sediment becomes too heavy for the water to carry
- if the wave loses energy
What is weathering?
The breakdown of rocks over time
What types of weathering are there?
- mechanical (physical) weathering
- chemical weathering
- biological weathering
Types of physical weathering
- freeze-thaw weathering
- crystallisation
- exfoliation
- wetting and drying
Do rocks expand when they are wet or dry?
Rocks expand when they are wet
Types of chemical weathering
- carbonation
- oxidation
Types of biological weathering
- plant roots
- birds
- rock boring
- seaweed acids
- decaying vegetation
What is mass movement?
The movement of material down a slope under the influence of gravity
Types of mass movement
- rockfall
- landslides
- slumping
- soil creep
- mudflows
What type of weathering is more common in colder climates?
Mechanical weathering
What type of weathering is more common in warmer climates?
Chemical weathering
