EQ2: How do characteristic coastal landforms contribute to coastal landscapes? Flashcards
What factors does wave size depend on?
The strength of the wind
The duration the wind blows for
Water depth
Wave fetch
When do waves break?
Waves break as the water depth shallows towards a coastline - at a water depth of approximately half the wavelength.
What happens as waves approach the shore?
As waves approach the shore, wavelength decreases and wave height increases, so waves ‘bunch’ together.
The wave crest begins to move forward much faster than the wave trough.
Where are constructive waves usually found?
Constructive waves are generally found where nearshore depths are shallow and there are gently sloping sandy beaches.
What are the four main processes that cause erosion?
Hydraulic action
Abrasion
Attrition
Corrosion
What is another word for hydraulic action?
Wave quarrying
What is the effectiveness of wave erosion processes determined by?
The type of wave (destructive or constructive)
The size of wave (linked to energy)
The tide level
The shape of the coastline
The lithology (characteristics of the rocks).
What is hydraulic action (wave quarrying)?
When a large destructive wave breaks on a cliff for one/two seconds the force of water exerts considerable pressure, around 50kg/cm2. This pressure may loosen pieces of rock. Air may also be trapped in the circular shape of the breaking wave and compressed into cracks and joints in the rock. Pressure released - rock shatters.
What factors in relation to structural geology influence the location of fault lines and fissures?
The location of fault lines and major fissures influences the location of caves and therefore arches.
Name the four ways in which transport of sediment happens.
Traction
Saltation
Suspension
Solution
Explain the process of longshore drift.
When wave crests approach a coast at an angle (rather than at 90 degrees to the coast) the swash from the breaking waves, and the subsequent backwash, follow different angles up and down the beach in a zig-zag pattern.
Where do rip currents take sediments from and to?
Rip currents take sediments from the foreshore to nearshore areas.
When does the strongest longshore drift occur?
The strongest longshore drift occurs when waves approach the coast at an angle of 30 degrees to the beach.
When is sediment deposited?
Sediment is deposited when the force transporting sediment drops.
Name the two ways in which deposition can occur.
Gravity settling
Flocculation
Name the process that transports sediment along the coastline and contributes to many depositional landforms.
Longshore drift
Why do sandy beaches have a gentle angle, while pebble beaches are steeper?
Because of the angle of rest of the particles and the wave energy shaping them.
What happens to the longshore drift current in the process of spit formation?
The longshore drift current spreads out and loses energy, leading to deposition.
Summarise the processes contributing to the formation of a bay head beach.
Waves break at 90 degrees to the shoreline and move sediment into a bay, where a beach forms. Through wave refraction, erosion is concentrated at headlands and the bay is an area of deposition.
What is a tombolo?
A sand or shingle bar that links the coastline to an offshore island.
Why is wave refraction key to how tombolos are formed?
Tombolos form as a result of wave refraction around an offshore island which creates an area of calm water and deposition between the island and the coast.
What two processes are the formation of tombolos determined by?
Wave refraction
Opposing longshore currents
Explain how a barrier beach/bar is formed.
A spit grows so long that it extends across a bay, closing it off.
What is the definition for a hooked/recurved spit?
A spit whose end is curved landward, into a bay or inlet.
Why does vegetation play a very important role in stabilising depositional landforms?
Vegetation binds the loose sediment together and encourages further deposition.
When do spits form?
Spits form when:
There is a dominant main longshore drift direction
There are plenty of sediments from mass movement and erosion
There is a gap in a coastline, such as an estuary or bay.
Name the three interlinked components that the sediment cell consists of.
Sources
Transfer zones
Sinks
What is the difference between negative feedback and positive feedback?
Negative feedback usually helps to maintain a balance within a system. Positive feedback tends to change the balance until a new equilibrium is reached.
What are the three types of weathering?
Mechanical weathering
Chemical weathering
Biological weathering
What are the three types of weathering?
Mechanical weathering
Chemical weathering
Biological weathering
Which type of weathering often speeds up mechanical or chemical weathering?
Biological weathering
Name the two types of mechanical weathering.
Freeze-thaw
Salt crystallisation
Name the three types of chemical weathering.
Carbonation
Hydrolysis
Oxidation
Name the two types of biological weathering.
Plant roots
Rock boring
Name the four types of mass movement processes.
Fall
Topple
Rotational slide/slumping
Flow
