Coastal Landscapes and Change Flashcards
Define abrasion
When rock particles are gradually worn down by impact against other rocks, making pebbles smaller
Define adaptation
To change to suit the environment
Define ‘advance the line’
A management strategy where the aim is to make the coast advance into the sea.
Define arch
When a cave punches through a headland e.g. Durdle Door
Define attrition
When waves hurl sand and pebbles at a cliff, gradually chipping away at the rock and wearing it down
Define backshore
A part of the littoral zone that is furthest from the sea and usually above the influence of the waves
Define barrier beach
A ridge of sediment running parallel to the shore formed by deposition, blocking off the entrance into a lagoon
Define beach nourishment
When sediment is put on a beach after it has experienced increased erosion.
Define bedding planes
Natural breaks in strata representing time gaps between periods of rock formation
Define berm
A terrace on a beach formed backshore above water level at high tide
Define biological weathering
When living plants or animals work to gradually break apart rock and wear it down
Define carbonation
A form of chemical weathering where weak carbonic acids work to dissolve rocks like limestone and chalk
Describe boulder clay
Very soft geology that is found on the Holderness Coast and erodes very quickly
Define blowhole
Created when a cave manages to break through to the top of the cliff and sea water and spray bursts out when the cliff is hit by powerful waves.
Define cave
A microfeature which forms the start of the sequence that results in stump formation, often caused by weathering and erosion .
Define chemical weathering
When chemical processes such as carbonation and oxidation act to gradually wear down rocks
Define cliff profile
The height and angle of a cliff face and its features
Define cliff regrading/drainage
When water is taken out of cliffs to stabilise them
Define climax community
A stable and balanced ecosystem where species and their interactions are adapted to the environment, formed after succession.
Define coastal morphology
shape of the coast
Define coastal recession
The retreat of a coastline due to erosion, sea-level rise or submergence.
Define corrosion
A type of marine action where alkaline rocks such as chalk and limestone are vulnerable to solution by weak acids found in sea water.
Define concordant coast
Alternate bands of more or less resistant rock running parallel to the coast
Define constructive wave
A gentle wave with low height, long wavelength and low frequency.
They are associated with deposition due to their strong swash and weak backwash.
Define cost benefit analysis
A process used to measure benefits of a project vs the costs to see how good a decision it would be
Define cuspate foreland
Triangular features extending out from the shoreline formed when two spits which follow different LSD join
Define destructive wave
A powerful tall wave with short wavelength and high frequency.
They are associated with erosion due to their strong backwash and weak swash.
Define Dalmatian coast
A type of concordant coast associated with rising sea levels which submerged a series of valleys and ridges, parallel to the coast
E.g. Croatia
Define differential erosion
When less resistant rock erodes faster to form headlands and bays
Define discordant coast
Alternate bands of more or less resistant rock running at a right angle to the coast.
Define ‘do nothing’
A management strategy where no defences are made and allows the ocean to erode the coast
Define aligned beach
Beaches aligned with the direction of longshore drift
Define stabilisation
When species like marram grass are planted on sand dunes to stabilise the sediment and helps trap it so they can build more
Define dynamic equilibrium
The tendency towards a natural state of balance within a cycle
Define emergent coastline
Landforms created due to relative fall in sea level
Define an ‘Environmental Impact Assessment’
An assessment technique that aims to anticipate the impacts of a project
Define environmental refugee
When a person is forced to leave their homes due to a change to the environment such as sea level rise or flooding
Define eustatic change
The rise or fall of global sea level relatove to land due to thermal expansion or melting of sea ice
(ocean go up down, land stay still)
Define faults
Formed when stress on the rock exceeds its strength and causes it to fracture and split along a fault plane
Define fetch
The distance over which wind is blown, causing waves
Define fjords
A drowned glacial valley with very steep sides and deep water
Define folds
Formed by pressure during tectonic activity causing rocks to crumple, especially when less resistant e.g. Lulworth Crumple
Define freeze-thaw weathering
When water gets into a fracture in rocks, freezes and expands in volume, causing the fracture to widen, eventually breaking it.
Define geology
Type of rock and its chemical properties
Define groyne
vertical stone or timber structures built at a 90 degree angle to the coast to trap sediment
Define Haff coast
A concordant coastline with a spit with lagoons parallel to the coast
Define halophytes
Salt marsh pioneer plants which are very salt tolerant e.g. cordgrass
Define halosere
The salt marsh plant succession overtime as a whole
Define hard engineering
Long term physical structures, usually expensive
Define headlands and bays
Bays are when less resistant rock is eroded faster, while headlands are left behind due to being more resistant
Define high energy coastline
Also known as rocky coasts
Typically, rocky and steep, experiences powerful waves that form erosional landforms
E.g. Hangman’s Cliff in Devon
8% of UK coastline is cliffs
Define ‘hold the line’
A management strategy which focuses on keeping the coast where it is
Define impermeable
Water cannot pass through
Define hydraulic action
A type of marine action which erodes the cliff due to the sheer power of the waves forcing air into the cracks, which expand as the waves recede, causing them to widen and the cliff to weaken
Define ICZM
Integrated Coastal Zone Management - Plans defences while looking at the whole coast and manages them fairly
Define isostatic change
Local rise or fall of land level relative to the sea due to presence or absence of weight on land due to glacial ice or accretion
(Land move up down, ocean stays)
Isostatic recovery/subsidence
The change in land level where land is compressed and sinks due to the weight of ice or sediment or when it rebounds after this ice melts
Define joints
Vertical cracks caused by contraction of rock or by tectonic forces during uplift
Define lithology
The physical characteristics of a rock
Define littoral zone
The zone between land and sea, includes backshore, foreshore, nearshore and offshore
Define longshore drift
Transportation of sediment due to waves approaching the coast at an angle of the prevailing winds, swash carries the material along
Define low energy coastline
Also known as coastal plains.
Sheltered coasts with limited fetch and low wind speeds, making waves smaller
E.g. sand dunes, salt marshes, estuaries
Define ‘managed retreat’
A management strategy which focuses on flooding low lying coastal areas in a controlled manner
Define mass movement
A type of sub-aerial action where rocks, sand, soul etc move downslope under the influence of gravity
Define mechanical weathering
Processes that break up cliffs using physical force
Define mitigation
To reduce or prevent the effects of an event
Define mudflow
Unconsolidated soil becomes saturated by heavy rain which can cause the top layer to flow off the cliff
Define offshore
The area of a coast that is beyond the influence of waves
Define nearshore
The wave breaker zone
Define offshore bar
A submerged or partially exposed ridge of sand/sediment that is built by offshore waves
Define offshore breakwater
Walls built parallel to the shoreline offshore which dampen energy of waves reaching protected coastlines
Define permeable
The ability for fluids to flow through a rock
Define plant succession
The process of vegetation stabilising dynamic depositional features like sand dunes from colonisation of pioneer species to a climax community
Define pioneer species
Plants that are able to cope with harsh conditions such as water shortages and highly saline conditions. They are the first to grow on sand dunes and salt marshes.
Define polder
Low lying land that was reclaimed from a body of water
Define positive feedback
A process that continues/furthers the effects of a disturbance
Define negative feedback
A process that returns disturbances back to normal conditions
Define porous
Presence or absence of pore spaces within a rock between grains
Define raised beach
A feature of an emergent coastline.
A flat area well above sea level formed as sea level has dropped e.g. Isle of Arran, Scotland
Define recurved spit
A spit with a hooked end due to secondary wind direction
Define relic cliffs
A feature of emergent coasts
Cliffs that used to be actively eroded when the sea reached the raised beach beneath it. Now these cliffs are relic because they receive no erosion and have vegetation on them.
Define relief
The shape of land focussing on aspects such as high and low elevation
Define revetments
A sloping concrete wall which are often permeable. They also absorb wave energy and reduce swash
Define rias
A flooded V-shaped river valley
Define rip current
A strong localised and narrow current of water that moves away from the shore
Define rock armour
Large rock boulders used to break up, dissipate and reduce wave energy
Define rock fall/slide
Examples of mass movements where rocks fall vertically or slide down the slope along the bedding plane
Define rotational scar
The scar left behind due to rotational slump
Define salt marsh
An area of periodically flooded low lying coastal wetlands
Define salt weathering
When saltwater evaporates and leaves salt crystals behind which can grow in joints in rock causing it to break overtime
Define saltation
A transport process whereby sediment bounces along the beach or seabed
Define sand dunes
A depositional feature that forms when sand is initially trapped by debris and builds up towards the back of the beach
Define sea wall
A form of coastal defence constructed on coasts which dissipate wave energy
Define sediment cell
A system with sources, transfers and sinks where sediment moves along coastlines. There are 11 major sediment cells along the coastline of England and Wales.
Any action in one place (e.g. installing groynes) has an impact elsewhere in the cell.
Each cell operates between physical barriers that prevent the sediment from moving further along the coast.
Define sediment budget
The amount of sediment within a sediment cell
Define scree/talus
An accumulation of loose stones lying on a slope or at the base of it
Describe the Shoreline Management Plan (SMP)
The UK’s version of ICZM. It’s a large-scale assessment of risks associated with coastal processes and aims to reduce them
Define slump
A rotational mass movement usually occurring in saturated conditions
Define soft engineering
Works with natural processes to reduce erosion and flooding, usually cheaper and designed to fit with environment
Define soil creep
The slowest mass movement where damp soil moves very slowly down the slope as the weight of the water pushes it forwards
Define solifluction
Slow downslope movement of soil due to freezing and thawing of the ground
Define solution
Also known as corrosion, this is where rocks e.g. chalk are dissolved by weak acids in sea water
Define spit
A long narrow depositional feature made of sand or shingle, which extends from land into the sea
Define stack
An erosional feature where an isolated pillar of rock is left behind after an arch collapse
Define storm surge
Short term rise in sea level which occurs in an intense depression due to less weight pressing down on the seas surface
Define strata
Layers of rocks
Define stump
An erosional feature that forms when a stack collapses due to marine action and sub-aerial processes
Define sub-aerial processes
Cliff face processes where cliffs are attacked through weathering and mass movement
Define submergent coastlines
A coastline that has been flooded due to eustatic change
Define subsidence
The sinking of land surface which occurs when loose unconsolidated sediment (e.g. in deltas) begin to compress
Define summer/winter profiles
Summer beaches have berms and winter beaches dont due to berm erosion
Define suspension
Where light sediment is picked up and carried by water
Define sustainable
The practice of using resources responsibly, so they can support both present and future generations.
Define swash aligned beach
A beach created when sediment moves up and down the beach with little lateral transfer
Define terminal groyne syndrome
When higher rates of erosion occur immediately after a set of coastal defences
Define tidal range
The difference between high and low tide
Define tide
The advancing and retreating of sea water along a coastline. Formed by the gravitational pull of the moon. They are high twice a day and every 12 hours
Define thermal expansion
A cause of sea level rise, associated with water volume expanding as it gets warmer
Define tombolo
A beach or ridge of sand and shingle that has formed between the mainland and a small island
Define traction
A transportation process where large rocks or boulders are rolled along the sea floor
Define wave-cut platform/notch
A notch forms after waves erode the cliff and a cave forms. Then gravity causes the unstable cliff to collapse and a wave cut platform is made
Define weathering
the breakdown of rocks in situ
Define wetting and drying
A type of weathering where rocks rich in clay expand when wet and contract when dry, making them crack and break up
Define xenophytes
Sand dune pioneer plants that are drought resistant
How do we classify coasts?
Long Term Changes:
* Geology
* Changes in sea level
* Formation processes
Short Term Changes
* Tides
* Level of energy
What are the three rock types?
- Igneous
- Metamorphic
- Sedimentary
Describe features of igneous rocks and give examples.
- Has a very slow erosion rate
- They are crystalline (Interlocking crystals make then stronger)
- Have very few joints so have limited weaknesses, making them less vulnerable to erosion
E.g. granite and basalt
Describe features of metamorphic rocks and give examples.
- Has a slow erosion rate
- They are crystalline (Interlocking crystals make then stronger, but when crystals point in one direction, it is weaker)
- Can be folded and fractured making them vulnerable to erosion
E.g. slate and marble
Describe features of sedimentary rocks and give examples.
- Moderate to fast erosion rate
- They are clastic (made of broken pieces of older rocks)
- Geologically young so tend to be weak
- Many bedding planes = weaker
E.g. Sandstone, limestone (has a very slow erosion rate) and shale
Define unconsolidated sediment
Not stuck together so are loose and easily erode
E.g. sand, gravel, clay and silt
Define pore water pressure
The pressure water experiences at a particular point below the water table due to the height of the water above it
What is wave refraction?
Straight wave crest refracts, becoming curved. They spread out in bays and become concentrated on the headlands
This causes powerful waves hitting the headland.
How are sand dunes formed?
- Sand becomes trapped by debris at the back of the beach
- Due to the sands high pH and low moisture retention, xerophyte pioneer plants like Lyme grass colonise. This is an embryo dune.
- More sand accumulates and roots from pioneer plants bind the sediment together and protect from wind erosion, making the dune larger. These plants add more nutrients, help in water retention and make dunes more hospitable. This is a yellow dune.
- Less specialised species, such as mosses, are able to colonise due to humus being added to the sand and conditions getting better. These are grey dunes.
- After a while the soil becomes less sand than soil and large plants like trees can colonise, forming a climax community.
Define psammosere.
The full succession of sand dunes from bare sand to climax community
Define plagioclimax.
An area or habitat in which the influences of the humans have prevented the ecosystem (climax community) from developing further.
Where do salt marshes occur?
In sheltered areas like estuaries and behind spits
How are salt marshes formed?
- Halophyte pioneer vegetation, like eel grass, slows down water and traps sediment. This allows for more eelgrass to grow.
- As pioneer plants reduce the harshness of the environment, plants like sea lavender can colonise to produce dense mats of vegetation that build up more sediment.
- After a while, the salt marsh is higher than sea level so is no longer covered in sea water. This allows for less specialised plants like reeds to colonise.
- This eventually leads to a marsh uplands with plants like oak trees able to colonise.
What causes waves?
A wave forms when wind blows over water and the friction transfers some energy from wind to water. The size and energy of a wave is determined by the strength and duration of wind, the wave fetch and the depth of the water.
Prevailing winds are the ones that blow most frequently.
What is a wave crest?
The highest point of a wave
What is a wave trough?
The lowest point of a wave
What is a wave wavelength?
The distance between two wave crests
What is a wave wave height?
The vertical distance from the crest to the trough
What is a wave amplitude?
The height of the crest above the wave base
What is a wave base?
The depth below the water which does not feel the wave
What is swash?
When a wave breaks, water is washed up the beach aligned with the wind
What is backwash?
When the water runs back down the beach at a right angle from the swash end point
What are the 4 types of erosion?
- Hydraulic action
- Abrasion
- Attrition
- Solution
What is hydraulic action and what is its role in lithology?
Air trapped in cracks in rock is compressed by the force of the waves crashing against the cliff. Pressure forces the cracks open.
Rocks with many joints are most vulnerable. May be the only force acting of very hard igneous rock
What is abrasion and what is its role in lithology?
Sediment is thrown against the cliff face, gradually wearing it down.
Soft sedimentary rocks are more vulnerable.
What is attrition and what is its role in lithology?
As sediment is moved around by waves, collisions between particles slowly chip away at the sediment, making it smaller.
Soft rocks can very quickly reduce in size via attrition.
What is solution and what is its role in lithology?
Carbonate rocks are vulnerable to solution by rainwater, spray from sea or seawater.
It mainly effects limestone which is vulnerable to solution by weak acids
What is a spring tide?
When the moon is between the Earth and the sun, and their combined gravitational pull creates higher tides
What are cliff foot processes?
Aka marine action. When the sea attacks the base of a cliff and erode the cliff foot.
E.g. hydraulic action, abrasion and solution
What are cliff face processes?
Aka sub-aerial processes. When processes like weathering and mass movement help break down the cliff.
What are some examples of erosional landforms?
- Cliff dip
- Wave cut notch/platform
- Headlands and bays
- Caves, arch, stack and stumps
What are the three types of weathering?
- Mechanical
- Chemical
- Biological
What are some examples of mechanical weathering?
- Freeze thaw
- Salt crystalisation
What are some examples of chemical weathering?
- Carbonation/acid rain
What are some examples of biological weathering?
- Plant roots
- Animal boring
What is freeze thaw?
- Water enters cracks
- Colder temperatures freeze water and it expands
- Ice melts leaving crack bigger
Whats an example of mass movement?
St Oswalds Bat in Dorest has a landslide scar which was formed after a 2013 landslide
What are the different types of mass movement?
- Rockfall -> When individual rocks fall off a cliff face, usually from freeze thaw
- Landslide -> Rapid movement of detatched slabs of rock down an angled cliff face
- Slump -> Huge masses of material slowly rolls downslope, forms rotational scars and a terraced cliff profile
- Soil creep -> Very slow downhill movement of soil and rock
- Mudflow -> Saturated soil flows downhill, often due to heavy rain
What are the transport processes?
- Traction
- Saltation
- Suspension
- Solution
What is traction?
When sediment rolls along the seafloor, being moved by waves and currents
What is saltation?
When sediment bounces along the seafloor, due to the force of wind or water
What is suspension?
Sediment is suspended in the water column
What is solution?
Dissolved material is carried in the water
What are examples of depositional landforms?
- Swash aligned beaches
- Spit
- Recurved spit
- Barrier beach
- Tombolo
- Cuspate foreland
Why are depositional landforms vulnerable?
Depositional landforms consist of unconsolidated sediment that can be easily eroded.
This means they are vulnerable to change and are dynamic landforms.
Change can result from major storms, especially when these occur during very high tides (spring tides).
Huge volumes of sediment can be eroded in a single storm.
Depositional landforms depend on a continual supply of sediment and continuous deposition to balance any erosion that takes place.
How are depositional landforms stabilised?
Vegetation plays a very important role in stabilising depositional landforms.
Plant succession, in the form of salt marshes and sand dunes, bind the sediment together and encourage further deposition.
The landforms are therefore more vulnerable when their vegetation is damaged, perhaps due to overgrazing or trampling.
What is dredging and what effect does it have on coastal recession?
Dredging is the removal of sand and gravel from the seabed or river beds. Carried out to provide sand and gravel for construction purposes and for beach nourishment and to widen / deepen rivers and entrances to ports to increase navigability and accessibility.
It reduces the supply of sediment to the coast – this can reduce the size of beaches, increasing exposure to erosion. It can deepen the nearshore and offshore area, allowing larger waves to reach the land with more erosive power.
What are dams and what effect does it have on coastal recession?
Dams can cause water and sediment levels in rivers to decrease. This is due to water withdrawals for human use, and because the water may be more slow moving, sediment is likely to be deposited and trapped behind the dam.
What is the case study for coastal recession?
The River Nile
A delta is formed by the deposition of sediment at the river mouth. Over half of Egypt’s population live on the delta and this coastline is experiencing rapid coastal retreat, with significant erosion taking place on at least half of the delta.
What % of the Nile delta is classified as highly vulnerable?
A third of the delta is classified as highly vulnerable.
What are the 5 sources of sediment at The Wash? (Holderness Coast Case Study)
- Sandstone cliffs eroding between West Runton and Weybourne
- Tidal currents pick up glacial deposits from sea floor
- Erosion of Holderness Cliffs
- Sand from Lincolnshire
- Discharge from 4 rivers
What is an ICZM?
Integrated coastal zone management
This is how the entire coastal zone is managed. It recognises the importance of the coast to livelihoods and the management must be sustainable.
It requires long term planning and many different stakeholders are involved. Plans are adaptive in case of change and they try to work with natural processes.
What is eustatic change?
The global rise/fall in sea level relative to the land
What is isostatic change?
The local rise/fall in land level relative to the sea
Subsidence can be caused by the weight of build up of ice on the land or sediment at estuaries that compresses them down
Recovery can be due to land ice melting, allowing for the land to rebound
What are the causes of sea level rise?
- Eustatic change
- Isostatic change
- Global warming
- Tectonic uplift
What are examples of submergent coastal features?
- Rias
- Dalmatian coasts
- Fjord
What are examples of emergent coastal features?
- Relic cliffs
- Raised beach
What is a ria?
A permanently flooded lower course and estuary of a river as it approaches the sea on a discordant coastline
E.g. Kingsbridge Estuary, Devon
What is a Dalmatian coast?
A series of flooded river valleys on a concordant coastline that form islands
E.g. Croatian coast
What is a fjord?
A drowned glacial valley with very steep sides and deep water.
E.g. Hardangerfjord, Norway
What are relic cliffs?
Cliffs that are too high above sea level to be eroded
What is a raised beach?
A flat beach where the sea no longer reaches
What are the daily changes in sea level?
- Tidal range
- Air pressure (low causes a slight rise in sea level)
What is the main cause for sea level rise?
Thermal expansion
