Coasts KQ1 Flashcards
What is a system?
Aims to maintain equilibrium by using feedback loops so as to not exceed the threshold
Give 5 types of energy at the coast?
1.Kinetic
2.Potential
3.Solar/Thermal
4.Geothermal
5.Gravitational
Why is interdependency so important at the coastline?
The coast is interdependent and complex, it relies on other stores, e.g. without erosion from cliffs there would be virtually no sediment inputs to the coastline
How many sediment cells are in the UK?
11
Define Sediment cell.
A stretch of coastline and its nearshore areas where the movement of coarse sediment, sand and shingle is largely self-contained
Are sediment cells closed or open?
The topography and any natural physical barriers significantly reduce transfer of sediment between cells, however this is inevitable due to variations in wind and other factors
What are the 5 physical factors?
- Geology
- Tides
- Ocean Currents
- Wind
- Waves
Give 2 ways in which wind influences coastal landscapes?
- The longer the fetch, the greater the wind speed, the more frictional drag across the sea and greater the wave energy
- Wind approaching the coast at an oblique angle allow for longshore drift to take place
What type of energy is possessed by waves due to its position above the trough?
Potential
Between Wave height and wave period, which of the 2 are greater factors in determining the wave energy? Provide evidence
In the Atlantic ocean, wave height is up to 8x higher than that in the English channel, both have similar wave periods, with wave energy 70x higher in the Atlantic, so wave height is more important.
What are the 3 characteristics of swell waves?
- Formed in open oceans and can travel long distances
- Long wavelength
- Period of up to 20 seconds
What are the 3 characteristics of storm waves?
- Shorter wavelength
- greater height
- shorter wave period
Explain how a wave breaks.
As wave approach shallow water the deepest circling water molecules start to drag across the bottom due to friction, this causes them to slow down, the wavelength starts to decrease as successive waves bunch up and the crest advances ahead of the base and will eventually break when the depth of water is 1.3 x wave height, there is then a significant movement of not only water but energy.
How do waves move up the beach?
The waves move up the beach as swash driven by the energy from the waves breaking, the speed will eventually decrease due to friction and a steeper uphill gradient, when energy can no longer move it forwards, it will return as backwash.
Describe what constructive waves are and how they break. As well as there frequency
They have a longer wavelength and less height, and frequency of 6-8/min, they break by spilling forwards, where the swash travels a long way up the gently sloping beach, the backwash occurs before the next swash so energy is retained
Describe what destructive waves are and how they break.As well as there frequency
Shorter wavelength, greater height, and frequency of 12-14/min, backwash will exceed the swash, the waves break by plunging forwards, little transfer of forward energy, over a steeply sloping beach, the swash doesn’t travel far before it moves back again as backwash where it meets the swash, causing frictional effect
What is the relationship between wave type and beach gradient?
High energy waves, typical of winter, tend to remove material, reducing the gradient, where as in summer low energy waves, build up the beach through deposition of material
How are tides formed?
Tides form due to the gravitational pull of the moon
How do spring tides form and how often?
They are formed when the sun, earth and moon are aligned and occur 2x a lunar month with a high tidal range
How do neap tides form and how often?
They form when the earth, moon and sun are right angles to each other and occur 2x a lunar month and have a low tidal range
How do tidal ranges impact the shape of the coastline? Use Tunisia and Severn estuary as examples
In Tunisia, tidal ranges can be up to 1.5m, which is lower than the 14m at the Severn, these tidal ranges impact weathering processes
List 4 types of Lithology from strongest to weakest and give the properties of each
- Igneous- e.g. granite, they are much more likely to form cliffs, with interlocking crystals, strong and resistant
- Metamorphic e.g. Marble, they often have foliation which makes them more susceptible to erosion
- Sedimentary- e.g. chalk, is more soluble and vulnerable to chemical weathering, often clastic so less resistant
- Unconsolidated clay
Meaning of porosity
Volume of spaces
Meaning of perviousness
rocks such as limestone have joints so more weaknesses
Meaning of strata
Layers of rock running parallel to coast
List the meaning of these 3 words:
Dips
Faults
Joints
Bedding planes
Folds
Planform
- Dips- angle of strata in relation to the coastline
- Faults- weaknesses formed by tectonic processes
3.Joints- vertical cracks which can form as land lifts up or dries out - These are horizontal cracks, often found in sedimentary rock
- These are compressions, with both synclines and anticlines
- structure of rock e.g. discordant or concordant
What are discordant coastlines? and what 2 features do they form.
These run at right angle to the coast and can form headlands and bays
What are concordant coastlines?
These run parallel to the coast
What are Rip Currents and what can cause them to be formed?
They are localised currents, caused by narrow seaward flowing waves against the breaking winds and are generated by waves at right angles to the coast. They can also have a velocity of up to 1-2 feet per second
What 2 things at a global scale drive ocean currents?
Earths rotation and convection
Where do warm ocean currents travel from and what do they impact most?
They travel from the latitudes to the pole, driven by onshore winds and they typically impact western facing coastlines the most
Where do cooler ocean currents travel from and what do they impact most?
They travel from the pole to latitudes and are driven by offshore winds and they usually don’t impact coastlines
How do ocean currents impact sub aerial processes?
Ocean currents can transfer heat energy to the surrounding and increase air temperature, impact sub aerial processes
How may ocean currents be impacted in the future due to climate change?
They may slow down or become warmer and lead to more destructive waves
What 3 things supply the coast with sediment?
- Terrestrial
- Offshore
- Human
Describe 2 ways in which offshore sources supply the coast with sediment.
- Wind which carries very fine sediment, it has less energy than water
- Constructive waves bring sediment to the shoreline via marine deposition
How are humans sources of sediment to the coast?
Beach nourishment is done to bring about equilibrium, done globally, when the sediment supply is in deficit
70% of the coastal sediment budget can come from..
wave erosion from high energy waves during storm surges, where cliffs can be eroded to provide boulders and rocks as cliffs are undercut
Can sediment delivery be intermittent (irregular)?
YES!! absolutely, e.g. from floods
Give 2 other ways in which sediment can be supplied from terrestrial sources.
- Rivers- which in some locations can amount for up to 90% of the total sediment budget,
- Longshore drift
