Coasts EQ1 Flashcards
Coastal processes
What is morphology?
Shape/ form of landscapes + features
What is a landscape?
Section of coastline made by multiple landforms
What is a landform?
Features made by processes
What is the littoral zone?
The area of shoreline where land is subject to wave action
What are the 4 section of the littoral zone?
- Backshore (above high tide, only affected by waves during spring tides)
- Foreshore (wave processes confined here between high and low tide marks)
- Nearshore (shallow wave areas close to land)
- Offshore (intense human activity)
What are rocky coastlines?
- Cliffs varying in height from few-hundreds of m
(cliffs are formed from rock-> hardness of rock is variable) - Hangman’s Cliff- Devon
What are coastal plains?
- Land gradually slopes towards the sea across area of deposited material
(sand dunes/ mud flats) - referred to as alluvial coasts
Example of a cliffed coast
Flamborough Head- Yorkshire
- Transition from land to sea= abrupt
- Low tide= exposure of wave-cut platform
- Cliffs vertical, cliff angle much lower
- DISCORDANT
Example of sandy coastline
Belgium beach
- high tide= sandy beach inundated (vegetated dune not)
- Dune vegetation plays crucial role in stabilising beach
- CONCORDANT
Example of estuarine coastline
Lymington- Hampshire
- Mud flats, cut by channels, exposed at low tide, inundated at high tide
- Closer to backshore= mud flats vegetated (salt marsh)
- Gradually transitions from land to sea
What is the coastal system?
Narrow strip where sea and land interact is shaped + influenced by natural + human variables
What are the inputs of the coastal system?
- Marine
- Atmospheric
- Land
- People
What are the processes of the coastal system?
- Weathering
- Mass movement
- Transport
- Erosion
- Deposition
What are the outputs of the coastal system?
- Erosional landforms
- Depositional landforms
- Different types of coasts
What are formation processes?
Primary coasts= land based processes (deposition)
Secondary coasts= marine erosion/ deposition processes
What is relative sea level change?
Emergent coasts= coasts rising relative to sea level
Submergent coasts= flooded by sea
What is tidal range?
- Microtidal= 0-2m
- Mesotidal= 2-4m
- Macrotidal= >4m
What is wave energy?
Low energy= sheltered coasts, limited fetch, low wind speeds, small waves
High energy= exposed coasts, face prevailing winds, long wave fetch, powerful waves
What are some short term affects at the coast?
- Tidal range
- Energy
- Dynamic equilibrium
- Weathering
- Erosion v deposition
- Sea level through earthquakes
- Storms/ weather
What are some long term affects at the coast?
- Geology
- Sea level (human cause)
- Formation process
- Ice age sea level rise/ fall
List the rock types in order from most to least resistant
- Granite
- Limestone
- Chalk
- Sandstone
- Shale
- Clay
- Sand
What is unconsolidated rock?
Material deposited with no structural integrity
(Gravels, boulders, clay, sands)
What are coastal plains + how do they form?
Coastal plains= low lying, low relief areas close to the coast
Formed-> fall in sea level exposing seabed of what was shallow continental shelf sea OR deposition of sediment from land brought down to coast by river system cause coastal accretion (coastline gradually moves seaward)
How are coastal plains maintained in a state of dynamic equilibrium?
- Deposition of sediment from river systems inland + deposition of sediment from offshore + longshore sources
- Erosion by marine action at coast
What is concordant?
Rock strata runs parallel to coastline
What is discordant?
Rock strata intersect the coast at an angle
What landforms are at discordant coastlines + how do they form?
Eg. Dorset Coast
Headlands and bays
- Less resistant rocks erode to form bays, more resistant geology stays as headlands
Why are headlands more targeted to erosion compared to bays?
(Wave refraction)
- As waves approach shallower water offshore of headland they slow down + wave height increases (friction occurs)
- Wave crests curve to fill bay and wave height decreases
- Straight wave crests refract, spreading out into bays and concentrating on headlands
What are some features that effect coastline shape in the UK?
- SW effected by coast erosion (fetch from Brazil)
- Holderness coast effected by geology
- River erosion effects areas behind Ireland
Scotland change due to sea level
How do concordant coastlines have an effect of the coast?
eg. Lulworth Cove
- Resistant rock eroded due to faults causing weakness
- Marine erosion broken through resistant rock + rapidly eroded wide cove behind
- Chalk at the back (resistant) stopping erosion further inland
What is the Holocene?
Geological epoch that began 12,000 years ago at the end of last Pleistocene ice age
Give an example of a concordant coastline and what has happened to it?
Dalmatia- Croatia
Geology= limestone
- Area flooded during the Holocene
- Limestone folded by tectonic activity into series of (upstanding) anticlines + (lower basin) synclines that trend parallel to modern coastline
- Created long, narrow islands offshore
Example of a Haff coastline
Southern fringe- Baltic Sea
- Long sediments ridges topped by sand dunes run parallel to coast offshore
- Create lagoons between ridges
What effects the vulnerability of a coastline?
- Rock type
- Lithology
- Structure
- Angle/ direction in which it lies
What is lithology?
Rock type
(speeds up/ slows down erosion + weathering)
What is permeability?
Porosity= empty space-> ability to hold fluids
Permeability= allows fluids to move though
Why is permeability important?
Groundwater flow through rock layers + weaken rock by removing cement that binds rock together
What is strata?
- Layers of rock (happen at different times)
- Some is stronger than others-> collapse
- Encourages mass movement
What are bedding planes?
- Gaps in strata appear (horizontal cracks)
-> due to rock being put down + something changes where it is, stopping movement
What are joints?
- Vertical cracks (due to tectonic movement/ rock contracting during transformation fracture dividing rocks into 2 sections)
What is faulting?
- Cracks across which rocks have been offset (pressure caused by tectonic activity)
- Faults move along bedding plane
What are dip angles?
- Angles at the strata in relation to waves (encourages waves o erode strata)-> causes more landslides/ mass movements
- More stable if angle steeper compared to horizontal position
How are dip angles formed?
- Horizontal strata produce steep cliff
- Rocks dip gently towards the seas (with almost vertical joints)
- Steep dip towards sea-> rock slabs slide down cliff along plane
- Rocks dip inland producing stable, steep cliff profile
- Rock dip inland, but with well developed joints at right angles to bedding planes
Lithology example?
Glamorgan Heritage Coast
- Bedding planes + strata
- wavecut platform (slows waves down-> friction)
- Caves at different stages (lithology affecting formation of microfeatures)
Reynards Cave-> horizontal strata, porous holes (encourage hydraulic action), bedding planes
- Mass movement at bottom (scree)= abrasion erosion
What is the rate of erosion of igneous rock?
Very slow
- Crystalline-> interlocking crystals are strong, hard erosional resistant
- Few joints (granite)
What is the rate of erosion of metamorphic rock?
Slow
- Crystalline-> resistant
- Foliation= crystal orientated in one direction (produces weakness)
- Folded + heavily fractured (weaknesses)
What is the rate of erosion of sedimentary rock?
Moderate/ fast
- Younger rocks= weaker
- Many bedding places + fractures (vulnerable)
How does vegetation stabilise sediment?
- Roots of plants bind sediment particles
- Provide a protective layer (when submerged) so surface of sediment not directly exposed to moving water
- Protect sediment from wind erosion (reduces wind speed due to friction)
What are halophytes?
Tolerate salt water
What are xerophytes?
Tolerate very dry conditions
What does succession mean?
Changing structure of plant community over time as area of initially bare sediment colonised by plants
What are pioneer species?
Plants that begin to grow in bare sad/ mud (they are able to tolerate extreme conditions)
What is the seral stage?
Each stage in a succession (each stage gives different soil + microclimate)
What is a climate climax community?
Combination of species in particular climate once succession is completed
What is the humus layer?
A layer of natural plant decay which increases the number of nutrients in soil
What is a sand dune ecosystem called?
Psammosere
Where are sand dune located?
Coastlines with gentle relief, constructive waves, small fetch
How is vegetation adapted to the psammosere ecosystem?
- Thick cuticle-> stops uncontrolled evaporation through leaf cell
- Sunken stomata + rolled leaves-> maintains humid air around stoma (marram grass)
What is needed for the formation of sand dunes?
- Regular sediment supply
- Wide exposed sandy beach at low tide
- Onshore winds
- Adequate vegetation (stabilise)
- Protection from humans
What is the order of sand dune formation?
- Embryo dunes
- Fore dunes
- Yellow dune
- Grey dune
- Dune slack
- Nature dune
Describe how a sand dune is formed
- LOW TIDE-> Sand dries out, wide expoed beach, aeolian processes
- EMBRYO DUNE-> Object, sand gathers + allows colonisation (<1m)
- FORE DUNE-> Marram grass traps more sand (<5m)
- YELLOW DUNE-> Less extreme conditions-> 80% surface coverage, humus layer developed (>10m)
- GREY DUNE-> 100% plant coverage (brambles), true soil forms
- DUNE SLACK-> Water table reaches surface, waterlogged, planted adapted to damp sheltered hollows (willow)
- NATURE DUNE-> Climatic climax community reached
What are destabilising issues at sand dunes?
- Human intervention
- Biological weathering
- River landforms
- Tuvial processes
- River flows
What are the influences of sand dune recession?
- Wind regime
- Sand supply
- Plant succession/ grazing pressure
How are sand dunes dynamic?
- Periods of wind erosion create low areas without dune systems (dune slack)
- Embryo + fore dunes prone to wind + wave erosion
What is a salt marsh ecosystem called?
Halosere
Why are estuaries ideal for the development of salt marshes?
- Sheltered from strong waves (sediment can deposit)
- Rivers transports sediment to river mouth (adding to sediment flow)
What is a flocculation process?
Small particles suspended in water lump + form larger aggregates/ flocs (weigh more so drop)
What are factors that effect salt marsh development?
- Climate (sea level)
- Tidal regime
- Human action (industry)
- Sediment supply
- River regime
How is corngrass adapted to survive in hostile environments?
1.Glands secreting salt (minimise dehydration)
2. Deeply recessed pores (reduce water loss)
3. 2 root system
Describe how salt marshes are formed
- Tidal currents slow + deposit material
- Uneven mudflats develop (exposed at low tide)
- Becomes colonised by pioneer plants (halophytes)
- Gradually develop close vegetation over mud
- Vegetation causes friction to slow tidal currents
- Plants grow leave/ stalks that die to build sediment supply
- Process increases mud flat levels by 30mm a year + food supply
- Mud level rise + land rise above sea level as new species established
What are direct human actions towards salt marshes?
- Water sports
- Grazing
- Industrial pollution
- Dredging removes sediment
- Reclamation
- Pressure for development
- Agricultural pollution
Example of a salt marsh in the UK
Keyhaven marshes
- linked to formation of Hurst Castle spit (spit receded across marsh, creating high crest to spit)
- Caused marsh to become exposed at seaward side
Not dealt with= spit become isolated + marsh overwhelmed by marine attack
- If erosion happens= coastline exposed to wake attack + flooding
Management plan-> 550m rock armour, spit nourishment with 300,000 m^3 shingles, 100m rock revetment
