Physical - Coasts Flashcards
What are inputs (in terms of systems)?
Energy and matter which are added into the system
What are outputs (in terms of systems)?
The end result of a system and the aspects of energy and matter that leave. Includes:
- Sediment removed beyond local sediment cells
- Depositional landforms
- Erosion landforms
- Dissipation of wave energy
- Accumilation of sediment above the tide line
What is a system?
An assemblage of interrelated parts that work together by way of process
What is an open system? Give a geographical example.
Matter and energy can be transferred.
Eg. Coastal systems
What is closed system?
Only energy can be transferred. Eg Planet Earth
What is an isolated system?
Neither energy or matter can be transferred
What is positive feedback?
When the effects of an action are amplified or multiplied by subsequent knock-on or secondary effects. (usually bad)
What is dynamic equilibrium?
When inputs and outputs of a system are in balance with use of feedback loops
What is negative feedback?
The effects of an action are nullified by its subsequent knock-on effects (usually good)
What sort of system are coasts?
An open system whereby matter and energy can be transferred
What is aeolian transportation?
Transportation with (suspended in) wind
What is the energy source of waves?
Wind as a result of low pressure rising under high temperatures
What is fetch?
The distance wind travels across the sea (or flat expanses of land)
From what points do you measure wavelength?
From crest to crest (OR trough to trough)
What is wave frequency?
How often a wave passes
What is wave height?
The distance (height) from crest to trough
What is swash?
The movement and deposition of sediment onto a beach
What is backwash?
The erosion (including removal) of sediment from the beach into the sea.
What is wave refraction?
The slowing down of waves in one location due to shallower water causing them to curve round into areas of faster current (in deeper water)
More erosion of headlands, forming arch, stack and stump
Give some characteristics of constructive waves.
- More elliptical orbital motion
- Long wavelength
- Short wave height
- Low energy
- More swash, less backwash
Give some characteristics of destructive waves.
- Short wavelength
- Long wave height
- High frequency
- High energy
- More backwash, less swash
Give a feedback loop for waves.
- Constructive waves build up a beach (with swash), steeper profile
- Steeper beach causes waves to become more destructive
- Destructive waves have more backwash, so beach is eroded and becomes shallow
RESTARTS
What is a spring tide?
Extremely high or low tides
Under what conditions do spring tides occur?
Sun and moon are parallel, causes larger ‘bulges’ of water due to more gravitational pull
Under what conditions do neap tides occur?
Sun and moon are not in alignment, so the water bulges are less big
Why are high tides helpful?
- The rise in sea level also rises the sediment suspended within it
- Builds up a bank of shingle to rear of shore and offshore
- Replenishes salt marshes with salty water
What is the tidal range?
The total area/distance tides affect a coastline (between HWM and LWM)
What are the 3 types of ocean current?
- Literal drift
- Rip currents
- Up welling
What are rip currents?
- Very strong currents moving away from a coastline
- Occurs due to a breaker zone or headland, forcing water to increase in speed
- Very localised
What is upwelling?
A type of current caused by the movement of cold water from the ocean floor to the surface. Replenishes nutrients and contributes to global ocean currents
What global ocean current affects the UK?
The gulf stream
Name the 6 major sources of sediment into coastal areas.
- Glaciers
- Off shore
- Cliff erosion
- Rivers
- Wind
- Literal drift
Why are rivers a source of sediment?
Deposit sediment in mouth of estuaries before being worked by tides
How do glaciers act as a source?
Glaciers calve out valleys, pic up and carry rocks in the process
What are components in systems?
Parts of a system which are all involved in its process
What are coastal system stores?
A non-permanent place where sediment is kept in system
What are coastal system sinks?
A (hypothetically) permanent place where sediment is kept forever. MORE DEPOSITED THAN RELEASED
What is a sediment cell?
- A stretch of coastline usually bordered by two headlands which acts as a (more closed) system
- Only a model, rarely actually acts as a separate system
How many sediment cells are there on England’s coastline?
11
What is accretion?
The build up of material
What is meant by a “Sediment budget”?
A combination of wave, current and tidal action which forms a beach or other prepositional landform. Includes losses and gains
What are “losses” in a coastal system/ sediment budget?
When sediment is deposited in a sediment sink
What can cause an upset in coastal systems?
Storms and river floods. Also, and increasingly so, human activity is a factor
Give an example of how human activity has disrupted a system. What happened their?
Hallsands, Devon
- Offshore dredging ocured in 1895, under government orders
- Beach subsided and retreated, much less wide
- Storms caused more and more damage until it was abandoned in early 20th century
Give an example of a regional study into coastal erosion conducted by the USGS.
The south Carolina Coastal Erosion Study
What was the main objective of the South Carolina Coastal Erosion study?
To determine the geologic and oceanographic processes that control sediment movement along the region’s coastline. Allowed for projections to be made
What is a wave-cut notch? How is it formed?
Where the cliff overhangs. Formed when softer bands of rock are eroded with harder rocks laying on top of them. Eg: Clay eroded laving Limestone over the top. Depends on LITHOLOGY
.
What affects the resistance of different types of rock to weathering?
The materials in the rock, the coherence of the materials and how compressed the constituent materials are
What is the difference between weathering and erosion?
Weathering: The disintegration of rock slowly, in situ
Erosion: The subsequent removal of rock
Give some example of physical weathering.
- Exfoliation (heated by sun)
- Freeze Thaw
- Wind power
- Hydrolic power
- Expansion of wet rocks
Give some example of chemical weathering.
- Crystallisation with salt
- Carbonation (dissolved by acid rain + sea water)
- Oxidation of iron-containing rocks
Give some example of biological weathering.
- Plant roots
- Excavation of nests/burrows by animals
What is a rockfall?
Cliffs undercut, overhangs form and fall down after time under gravity (often in storms)
What is a landslide?
Heavy rainfall can cause rocks and other sediment to loosen, starts slow, increasing in speed
What is a Runoff?
The movement of water over land. At the coast this is often a stream which causes vertical erosion
What are mudflows?
Soils become incredibly saturated after a long duration of persistent, heavy rainfall. Surface becomes fluid and flows downhill - depends on angle of hilside
What is slumping/rotational slip?
Soft rocks (or clay) slide over harder rocks, so soil slides down a concave slope. Common on glacial deposits
What soil creep?
The very slow movement of soil down a shallow slope, likely to the the result of saturated soils
What role does weathering and erosion play in a coastal system?
By removing material away from a source and depositing at a sink offshore (such as offshore bar) the force of the waves is reduced so less erosion occurs
What is hydraulic action?
The force of water/waves creating negative pressure, ripping off pieces of rock. Very strong, no debris involved
What is cavitation?
The expansion of a small crack in rock (as a result of freeze thaw) by hydraulic action
What is abrasion?
Sand suspended within the water wears away rock faces (sand papering effect), common on wave cut platforms
What is wave quarrying?
Combination of cavitation and hydraulic action. large waves in a storm enter gaps in the rock under extremely high pressure
What is corrosion? (weathering)
Calcium-rich rocks like limestone are dissolved
What is attrition?
Rocks suspended in the sea are slowly broken down/rounded by clattering together frequently
What is the term used to describe material transported in the wind?
Aeolian transportation
What is marine transportation?
Movement of material in the water
What is the movement of sediment along a coastline called?
Littoral drift
What are the two types of aeolian transport?
- Surface creep (rolling along the surface
2. Saltation (picked up in wind)
What are the 4 types of marine transportation?
- Traction (large rocks rolling along sea bed)
- Saltation (particles bouncing on sea bed)
- Suspension
- Solution (solutes dissolved in water)
What causes coastal deposition?
Low energy environments where the effects of waves, storms and tides are reduced
How do some coastal engineering strategies cause +ve feedback loops?
By reducing the effects of erosion or LSD at a particular location the effects are magnified elsewhere on the coastline where energy is highest
What type of ecosystem are sand dunes?
A psammosere ecosystem
What are inputs to sand dunes?
Sand, onshore prevailing winds, long tidal range, pioneer species and obstacle to trap sand
Outline the formation of sand dunes.
- Large tidal range exposed at low tide, wind blows sand inland
- An obstacle traps the sand so it builds up on the windward side
- The leeward side of the obstacle is sheltered so further sand is deposited
- Land is warmer than sea, causing lower pressures - aiding further deposition
- Sand progressively builds up and becomes fixed in place by pioneer species
What are “mobile dunes”?
The fore and yellow dune, move over time - hence the term moblie
What re the youngest dunes in sand dune succession?
Embryo dunes (<5 years old)
What measures are used to prevent footfall on sand dunes?
Dune fences can be erected
How do plant roots aid the sand dune ecosystem?
They retain water as it is a very dry, well-drained environment
How much sand is exposed on a healthy dune?
10-25%
Name some plant species found on sand dunes.
- Sand Sedge
- Sea Buckthorn
- Maram grass
- Reedbeds
- Heathland species
- Alder Carr
- Xmas trees are sometimes added for stability
What are blowouts in dunes?
Wind carves out a depression in dunes (promoted by footfall/animals weathering). Forms a dune slack
What are the dunes furthers from sea called?
Mature dunes. No longer interfered by coast
How old are most mature dunes?
400 years old
Name some threats to sand dunes.
- Agriculture
- Wildfires
- Interception of LSD, prevents transportation of sand, narrower beach
- Trampling by humans and sometimes animals
Name some management strategies for sand dunes.
- Education (leaflets by national trust)
- Signposting to prevent trampling
- Planting of maram grass + xmas trees
Give an example of sand dunes.
Studland, Dorset
How old are some of the dunes at Studland?
700 years old
What type of plant is maram grass?
A xerophyte, thriving in low water avaliablity
What is the term used to describe sand dunes in dynamic equilibrium?
Plagioclimax
What does inundation mean?
Flooding of inland areas with sea water, becoming area of sea
What is an ecosystem comprised of salt-tolerant species called?
A halosere ecosystem
How do mudflats form?
- Sea water and fresh water meet at the sea
- Velocities cancel out
- Particles suspended in the water flocculate (join together)
- Particles are deposited at the intertidal zone
- Halophytes colonise the area, securing the sediment
How do salt marshes form?
- Creeks form on mudflats where the current is strongest
- Leaves areas with higher ground, less effected by currents
- Pioneer species colonise, slow down current more, causing more deposition
- Land begins to be raised up over years
Give some examples of plant species present on salt marshes.
- Eelgrass
- Grasswort
- Sea blite
Of sand and shingle which forms shallower beaches? Why?
Sand (<5 degrees). Becomes compact when wet
Of sand and shingle which absorbs more wave energy? Why?
Shingle. It has much more large gaps between them so hydraulic action is absorbed, energy dissipates. Does also reduce backwash, forming steeper beaches.
What are drift-aligned beaches?
Beaches orientated parallel to direction of LSD, 45 degrees to prevailing wind direction, sediment travels along the beach. If coastline changes direction forms spits + tombolos
Why is equilibrium vital on drift-aligned beaches?
Without a continuous supply of sand they are more prone to erosion (less sediment inputted)
How do swash-aligned beaches vary with drift-aligned beaches?
- Orientated parallel to oncoming waves
- On irregular coastlines where headlands funnel waves
- Rare, examples include Lulworth Cove
What are ridges and runnels? How are they formed?
- Runnels are depressions in beach cross sections with water still present within them at low tide
- Ridges are located either side of runnels
- Formed by sediment deposited when current looses energy after being eroded from beach in backwash
What are berms?
Small ridges form near HWM of beach, built up by waves
What are cusps on beach profiles?
Small indentations beneath berms due to backwash
Give an example of an exemplar beach cross-section
Harlech beach, north Wales
Give a global example of a beach
Cox’s Bazar, Bangladesh
Give some facts on Cox’s Bazar Beach.
- 2nd longest uninterrupted beach in world
- 120km long, drift-aligned beach
- Human impacts from tourism threaten future
Give a UK example of a beach
West Wittering
In what ways is west wittering unique?
Litteral drift runs east to west (not west to east like much of southern UK
What was the speed of LSD at W Wittering in 2017?
2.7m/s
On what type of coastline do spits form?
On drift-aligned coasts at the point where a concordant coast turns discordant
Why do spits not cross an entire estuary (forming a bar)?
Too deep and currents are strong and persistent
What are the two types of sand spit?
Simple spits and compound spits
What are the differences between simple and compound spits?
Compound spits have minor spits to the landward side and multiple recurved edges which mark the old position of the spit. Simple spits do not
Give a global example of a spit.
Farewell Spit, NZ
Where is Farewell spit located?
Northernmost point on New Zealand south island
How long is Farewell spit?
26km long