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)
Define weathering
The breakdown of rock in-situ through exposure to the Earths atmosphere, organisms and water.
Give 5 mechanical weathering examples.
Freeze thaw - Water enters cracks, freezes and expands exerting pressure up to 2100kg/cm2 when rocks can only withstand a pressure of 500kg/cm2
Pressure release - When overlying rocks are removed by weathering and erosion, the underlying rocks expand and fracture, parallel to the surface.
Thermal expansion - During the day the rock heats up and expands, at night it cools and contracts causing cracks.
Salt crystallisation - Solutions of salt in sea water enter pore of porous rocks such as chalk and limestone, which then precipitate out and expand up to 300% causing cracks.
Wetting and drying - rocks rich in clay expand when wet, and crack when dry.
Give 5 chemical weathering examples.
Oxidation - Some minerals such as iron in rocks react with oxygen/water causing it to become soluble under acidic conditions
Carbonation - Carbon dioxide dissolves in water creates carbonic acid which is then either reacted with rocks from the ocean or rainwater which will dissolve them depending on their lithology.
Solution - Some mineral such as halite are soluble in water and as they dissolve they weaken the structure of the rock
Hydrolysis - Is the chemical reaction between minerals in water. Silicates combine with water producing secondary minerals such as clay or feldspars
Hydration - Water molecules added to rock minerals to create new minerals of a larger volumes such as anhydrite forming gypsum
Give 3 biological weathering examples.
Tree roots grow into cracks and joints and exert outward pressure, causing rock to split
Burrows - Similar effects
Organic acids - Decay of organic matter release acids that may dissolve a rock
What are the 5 mass movements?
Rock fall - Fast change, rain on top or marine erosion undercuts the base of a cliff with horizontal bedding planes causing the rock on top of the undercut to fall and accumulate at the base of the cliff
Landslides - Involves a block of rock moving downwards. Frequently occurs during earthquakes or heavy rainfall, which causes rocks to slide down the seaward dipping bedding planes. Is fast
Slumping - A slump differs from slides as is curved slip plane rather than straight. Occur in weak and unconsolidated clays which build up in water and causes it to fall. Is also fast
Mud flows - Saturated soils and weak rock flows down a slope, materials become mixed. Is sudden and fast but not as fast as others.
Soil creep - Slowest, soil gets wet and heavy. Particles rise towards the ground due to wetting or freezing then retreat vertically to the surface causing the movement of the soil
What are the 5 types of marine erosion?
Abrasion - Rocks are thrown at the coastline eroding the coastline
Attrition - Rocks hit against eachother eroding them
Hydraulic action - Waves break against cliff face, and air and water get trapped in cracks and become compressed. When the pressure is released, the air and water expand rapidly and the crack is widened.
Pounding - Mass of breaking waves exert pressure on the rock up to 30 tonnes
Solution - Involves miners in coastal rock dissolving in sea water, will become more significant with increases of temperature.
What are the 4 transport methods?
TSSS
Traction - Largest particles slide or roll along the river/sea bed
Saltation - Smaller particles bounce along seabed
Suspension - Smaller particles suspended in water
Solution - Particles dissolved in water
Name 6 landforms of erosion
Headlands + bays
Caves, arches, stacks and stumps
Geos
Blowholes
Marine cliffs
Shore platforms
What is the case study used for a high energy coast?
Flamborough to Saltburn
How do Headlands and bays form?
Bands of soft and hard rock on a discordant coastline are eroded. The soft rock erodes faster and creates a bay leaving hard rock on either side of the bay called headlands.
How do caves, arches, stacks and stumps form?
- Cracks expand and widen due to marine erosional processes
- Cracks widen creating a cave which deepens from further erosion
- If two caves are aligned, the waves cut through to form an arch or just erode through original cave
- This creates an arch, which will weather at the top weakening the support
- Arch collapses creating a stack
- The stack gets eroded and a wave cut notch forms, collapses the stack creating a stump
How do geos form?
- Wave action creates faults which erode creating a wave cut notch
- More erosion making a cave which deepens
- The top of the cave collapses due to gravity and weathering at the top
- Creates a ravine in between rock (geo)
How do blowholes form?
Form when the bottom of a cliff erodes which is under the water. Continuous hydraulic action causes water to force its way up and comes out in bursts,
How do cliffs form?
Vertical cliffs form when the strata is horizontal, marine erosion erodes the base of a cliff creating a wave cut notch. Further erosion causes rock fall making the cliff retreat perpendicular to the shore.
How do shore platforms form?
Form when cliffs retreat leaving a platform of rock where the old cliff used to be. Can only have a max of 4 degrees and 500m before the waves erode the platform instead of the cliff.
What is wave refraction?
Wave refraction involves waves breaking onto an irregularly shaped coastline, e.g. a headland separated by two bays. Waves drag in the shallow water approaching a headland so the wave becomes high, steep and short. The part of the wave in the deeper water moves forward faster causing the wave to bend.
Name 3 headlands and bays
Robin hood bay
Filey Bay
Slewicks bay
What is the fetch and the rate of erosion at Flamborough?
Fetch = 1500km
Wave height = 4m
Rate = 0.1m/yr on hard rock, 0.8 m/yr on soft rock
Name 6 depositional landforms?
Beach
Spit
Bar
Tombolo
Marsh
Estuary/delta
What are the two types of beaches?
Shingle
Sand