Coasts Flashcards
What is a system?
A set of inputs, outputs, stores and flows which are all connected to form a unified system.
Define equilibrium
Where inputs are = to outputs
Define dynamic equilibrium?
Where the equilibrium is disturbed, the system undergoes self regulation to undo said changes
What are sediment cells?
A stretch of coastline and its associated nearshore area which sediment is self contained in. They are closed systems so no sediment will transfer in, or out.
What are the 5 physical factors that work on coastal systems.
Winds
Waves
Tides
Currents
Geology
How are waves generated?
Is generated by frictional drag from winds moving across the surface of the ocean.
What affects a waves power?
Fetch - The distance the wind travels
Wind speed
How do waves break?
When the water gets more shallower, the waves come in contact with more friction, which reduces the wave energy, creating an elliptical wave orbit instead of circular creating a higher wave height. The deepest part of the wave slows more than the top part of the wave and then break when the depth is less than 1.3x the height
Define swash and backwash
Swash - The movement of water up a beach after a wave has broken
Backwash - The movement of water won a beach after a wave has broken
What are constructive and destructive waves?
Constructive - Swash is greater than the backwash so the beach is built up
Destructive waves - Backwash is greater than the swash so beach is destroyed
What is the frequency of both constructive and destructive waves?
Constructive = 6-8 per min
Destructive = 12-14 per min
What will the beach profile be like in the winter?
Higher wind speeds, means more destructive waves will be present, eroding material off of the beach. This will reduce the beaches gradient making it gentle gradient, and flat.
What will the beach profile be like in the summer?
Lower energy waves, means more constructive waves will be present, building up the beach. This will increase the beaches gradient, making it steeper.
How are tides generated?
Rise and fall of the sea surface is caused from the gravitational pull of the moon. Moon pulls water towards it giving a high tide. When the moon is aligned with the Earth and the Sun which happens twice per lunar month giving spring tides. When moon and sun are at right angles neap tides arise
Where are tidal ranges the lowest on the Earth?
Mediterranean. Which reduces wave action
Where are tidal ranges the highest on the Earth?
UK, where the coast is funnelled such as in estuaries, which increases the wave action.
How do tides affect a coasts shape?
Determines the wave action, low tidal ranges will have little wave action so therefore landforms of deposition will be present. High tidal ranges will have more wave action, so therefore more landforms of erosion due to more marine erosion and chemical weathering.
What are the two components geology is split into?
Lithology - Refers to the physical and chemical composition of rocks
Structure - Properties such as jointing, bedding, permeability and faulting
What is meant by concordant and discordant?
Concordant - Where rock outcrops are uniform and lie parallel to the coast
Discordant - Where different rock types lie at right angles to the coast, which create headlands and bays
What are the two types of coastlines?
Swash aligned - These coastlines are found near small bodies of ocean or are protected by offshore barriers or islands. The prevailing wind is unable to influence the wind directions and so waves approach the coast parallel to the shore. These build large beaches with possible dunes.
Drift aligned - These coastlines are exposed to a large open ocean, prevailing wind dominates wind direction and waves approach the coastline at an angle. These are associated with longshore drift. These will have beaches that are narrower and may be exposed to higher rates of erosion
What are the 3 types of strata on a coastline?
Horizontal - Undercutting by wave action lead to rockfall ; the cliff retreats inland parallel to the coast
Seaward dipping - Undercutting removes base support, which causes landslides and slumping along the bedding plane
Landward dipping - Rocks loosened by erosions and weathering are difficult to dislodge, the slope profile gradually lowers by weathering and mass movement.
How are currents generated?
Earths rotation and convection along with wind across the water surface. Warm currents transfer heat from low latitudes towards to poles so move upwards. Cold ocean currents do the opposite so move towards the equator.
What are 5 sources of sediment?
Fluvial deposition - Rocks eroded from the upper course of the river are transported downstream and deposited at the end of the river
Marine erosion - Cliff erosion by waves erodes the cliffs causing mass movement which then is deposited on beaches
Aeolian deposition/ offshore - Wind carries fine particles and deposits them as they loose energy
Longshore drift- This can supply sediment to one coastal area to another
Human- Beach nourishment via rainbowing and dumping of sand
What are 7 geomorphic processes?
Erosion
Weathering
Mass movement
Transportation
Deposition
Fluvial processes (Erosion, transportation and deposition in rivers)
Aeolian processes (Erosion, transportation and deposition in wind)