Costal Landscapes And Change Flashcards
What is the littoral zone?
Area of the coast where rapid change happens. Contains the back-shore, foreshore nearshore and offshore.
Coastal characteristics
Waves:
Constructive - low energy, depositional
Destructive - high energy, remove sediment
Processes:
LSD - depositional, due to wind and tides
River and current causes sediment depositing
Sediment from erosion can build up due to mass movement/weathering
What are examples of erosional landforms?
Erosional landforms are caused by high energy
Cliffs, wave-cut platforms, arches, sea caves, stacks
What are examples of depositional landforms?
Depositions landforms are caused by low energy
Beaches, spits, bars, sand dunes, mudflats and salt marches
Low energy and high energy coast
Low energy - sheltered, lowland, coastal plains
Heigh energy - exposed, highland and lowland, rocky
What is meant by strata?
The layers of rock that make up the geology of the coast
What is meant by deformation and faulting?
Deformation - Is the result of rocks being deformed by tectonic activity
Faulting - fractures in rocks causing them to move from original positions
What is a concordat coastline?
Parallel strata, long sediment ridges parallel to the coast, lagoons are created between the strata
what is a Discordant coastline?
Strata perpendicular to the coastline, alternating hard rock and soft rock cause the formation of headlands and bays. Due to greater wave energy, headlands are eroded quicker to their corresponding bay.
Igneous rocks
Strong, pretty resistant to erosion and weathering
Metamorphic rock
Pretty resistant, van have faults and fracture more easily(slate)
Sedimentary rock
Lots of layers make it prone to erosion, more strata make erosion faster(shale)
Unconsolidated rock
Easily eroded, not held together strongly(clay, sand)
What can make rock/coastal geology prone to erosion
Unconsolidated/weakly consolidated strata which make the rock permeable,so will be prone to erosion as water permeates the strata and weakens it.
How can vegetation protect coastlines?
Unconsolidated sediment is bonded together by plant roots
Reduce wind speeds
Plant leaves decompose and create soil
Three formations due to coastal vegetation:
Sand dunes
Salt marches
Mangroves
What is a Halophyte?
Plants which can tolerate salt water
What is a xerophyte?
Plants which can tolerate very dry conditions (allows them to grow on beaches, forming sand dunes)
Explain plant succession on dunes?
Embryo dunes form with ‘pioneer’ species which create conditions for new plants to grow which makes them foredunes, and a new embryo dune will appear.
Yellow dunes and grey dunes are behind these new dunes with marram grass and gorse.
Explain the process of salt marsh succession:
In what conditions does most coastal erosion occur?
When:
Waves are largest
Waves are at 90* to the cliff
High tide
Heavy rainfall (percolation of strata and surface runoff)
Define hydraulic action:
Air trapped in the cliff/rock forces cracks to open as waves hit. As cracks get bigger, so does the impact each wave has.
Define abrasion:
Loose sediment is hit against cliffs by waves
Define attrition:
Lose sediment hits against other sediment and becomes smaller and more rounded over time
Define Corrosion:
Rain or seawater dissolves carbonate rocks
Describe wave cut notch:
Destructive waves erode base of cliff by abrasion and hydraulic action
Describe wave-cut platform:
After wave cut notch, the overhang collapses(mass movement) and the rock left at the base of where the cliff was is now a wave cut platform
Cave, arch, stack, stump - process
Cave is formed where section of soft rock is eroded quicker
Cave cuts through the other side of the cliff and an arch is formed
The center/roof of the cave collapses or erodes over time and a stack is formed, which erodes into a cliff.
Sediment transport - define traction
Sediment rolled along shoreline by waves/currents
Sediment transport- define Saltation
Sediment bounced along the shoreline
Sediment transport- define Suspension
Sediment carried in water
Sediment transport- define Solution
Material dissolved in the water
Define LSD
Waves meet the shore at an angle and moves sediment along the shoreline (effected by currents, tide and wind)
Depositional landforms - define spit
Long strip of sand or shingle protruding into the sea
Due to LSD depositing sediment in its direction regardless of moving coastline
Depositional landforms - define bay beaches
A beach formed within a bay due to low energy waves(because of protection from the headland)
Depositional landforms - define tombolos
When a spit continues forming and eventually connects between an island and the mainland and forms a bridge between
Depositional landforms - define barrier beach/bar
Where a lagoon is formed as a spit has continued forming until it connects to the mainland at each end
Depositional landforms - define hooked spit
Secondary prevailing wind causes a spit formation to curve inwards towards the land
Depositional landforms - define cuspate foreland
Triangular shaped feature extending outwards due to two winds going in opposite directions causing deposition from two directions
What is the sediment cell concept?
Positive feedback: where change happens, and this change works to further increase the rate of change
Negative feedback:where change happens and works to decrease the rate of change and even reverse it
This introduces the theory that a sediment cell is constantly trying to reach dynamic equilibrium.
Sediment budget/equilibrium .
What are the three types of weathering?
Mechanical: rocks breaking down due to physical force
Chemical: involves chemical reaction
Biological: action from plants, bacteria or animals
Describe two mechanical weathering processes:
Freeze thaw: water in cracks expanding when it freezes(can cause breaking)
Salt crystallization: salt crystals forming in cracks exerting pressure on the rock
Describe three Chemical weathering processes:
Carbonic acid in rain dissolves rocks
Hydrolysis?
Oxidation in minerals increases volume and can cause mechanical breakdown
Biological weathering processes:
Plant roots: cracking rocks
Animal species boring into rock
Describe mass movement
Falling of sediment due to gravity
Describe the types of mass movement:
Rockfall: blocks of rock breaking off
Materials absorb water and become saturated, leads to mudflow
Topple: when strata tilt down towards the sea, causes sediment to topple forward
Short term sea level change causes:
High tide, low tide
Atmosphere pressure can change sea level slightly
Long term sea level change causes:
Sea temp change
Change in land height/level (isostatic change)
Define eustatic change:
Change in sea level
(Ice melt and ice freezing, in glacial periods)
Define isostatic change
Change in land level
(Glacier weight pushes land down, which rebounds when the ice melts)
Emergent coastlines
Raised beaches(from isostatic rebound)
Fossil cliffs (coastline isolated from the sea and is no longer being eroded)
Submergent coastlines
Often as a result of sea level rise(eustatic change)
Deep water rivers and fjords (at their bottoms)
Dalmatian coasts, the sea has drowned coastal land.
Impacts of global warming on coasts
Higher seas and waves, so more erosion.
Disappearance of low Luke g ecosystems and landforms
Stronger storms (destructive waves, faster erosion)
What physical factors affect rates of coastal erosion?
Wave types, destructive.
Prevailing Winds cause steeper and stronger waves.
Tides, higher leads to greater erosion
Submerging coast leads to faster erosion
Rock type changes erosion rates
Certain strata layout is more vulnerable to erosion
What physical factors affect rates of erosion?
Coastal defenses can reduce erosion at one location but starve another of sediment supply
Example: groynes reduce LSD
Dams lead to less sediment input
Dredging reduces sediment supply
What subaerial factors affect erosion at coasts?
Weathering: harsher weather, vulnerable rock types
Mass movement: rockfalls can expose more vulnerable rock types behind
Factors affecting risk of flooding:
Low lying land
Subsiding land(isostatic sinking)(eg the Essex coast)
Vegetation removal: mangroves and marshes reduce wave power
Roots build up sediment
How can climate change increase flood risk?
Change in precipitation patterns
Increased river discharge, shorter lag times)
Ice and permafrost can melt leading to flooding of surrounding areas
What is the likely rise of sea level by 2100
28-98cm
(Likely 55cm)
Adaptation strategies - water conservation and management
Positive: low cost and low impact
Negative: hard to maintain and can be costly in some areas
Adaptation strategies - resilient agricultural systems
Changing crop cycles and types due to changes in climate
Takes a long time and requires demand for the new crop types
Adaptation strategies - land use planning
Reduce risk to humans by preventing or managing risky land
Building changes can allow for revised risk assessment
Require developed community
Existing Land use cannot always be changed
Adaptation strategies - flood risk management
Identify areas with risk to flooding, adapting the area to better cope
Afforestation and wetlands as well as mangrove can be used to reduce risk
High cost usually
Displacement of people
Adaptation strategies- solar radiation management
Involves reducing heat energy for the sun
Requires international agreement as well as geoenginering (expensive)
Mitigation strategies - renewable energies
Reduces emissions
Not always viable for developing countries
Mitigation strategies - CCS
Can be used to reduce emissions from large power stations and factories
Suitable dumping locations are not always available
Expensive technology
Reduces profit margins
Mitigation strategies - energy efficiency
Doesn’t keep up with increasing use of machine
Mitigation strategies - carbon taxation
Encourage low carbon alternatives
Expensive alternatives
Some may not always want to change as well as increase expenses
Mitigation strategies -
Reduces co2 emissions
Not all countries may agree
Economic consequences due to coastal recession and flooding
Loss of property, UK does not pay compensation for lost homes
Falling property prices
Difficult to get insurance
Social consequences due to coastal recession and flooding
Relocation cost
Loss of QOF
Health impacts
Death, injury
Environmental consequences due to coastal recession and flooding
Loss of ecosystems and habitat
Landscape change
Stats of people displaced due to climate related events
22.5 million 2008-2016
What is rip rap?
Boulders
Expensive and unattractive
Reduces wave energy and increases deposition
What is offshore breakwater?
Rocks out to sea to reduce wave energy
