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Landform Development (Dep. Landforms: Salt Marshes + Mudflats (Saltmarshes…

- - - - More mud trapped = greater height
    - - When water evaporates, the salt remains = very alkaline conds. = no vegetation growth
    - - As water drains out of the creek the creek depends as banks increase in height
    - - High salinity, muddy (turbid) water + long periods of inundation
  - - - a. Clay carries neg. ions
      - b. Sodium Chloride carries pos. ions
      - c. The particles attract, stick together + sink
  - - - Fishing, farming, recreation, environmental protection, narural defence
    - - Sea wall is protecting grazing marsh
      - This grazing marsh took 400 years to form, so its harder to replace
      - Marsh is easier to replace via coastal re-alignment
    - - 1000 years ago - was a freshwater sys. from the Thames
      - Middle ages - 18 Cent. - human influence
        
        Reclamation of marsh for farming
        
        Built a sea wall + developed new marsh in front of it
        
        S.l rise = salt marsh eroded + sea wall directly attacked
    - - Some areas will be protected but others will be let go
      - Increased erosion of marsh due to s.l. rise
      - Important for diversity + natural defense - endangered bird species there
- - - - Wave acts as a hammer on solid rock - vibrations loosen blcoks
      - Water cannot be compressed but it traps air in joints
        
        = pneumatic pressure
        
        As wave retreats, blocks may be forced out by explosive decompression of trapped air = wave quarrying
      - Swash + backwash can both remove sed. from the swash zones
    - - Blowholes, goes, caves, cliff profile + retreat
  - - - Slow on hard rocks = smooth surfaces
      - Differences in rock types are accenuated
        
        Bc of differential erosion - more res. rocks protrude + temporarily protect the less resis-rocks
    - - Wave-cut notches, caves, intertidal platforms
  - - - Dissolved CaCO3 is removed by breaking waves
      - Intensity of carbonation increases towards the LWM bc of increased biological + activity
    - - Limestone coasts - rounded hollows formed - can then be enlarged by abrasion = pinnables
    - - Lapies, visors
  - - - Pebbles becomes smaller + rounder while protecting the cliffs from hydraulic action + abrasion until they are small enough to be totally removed from the ITZ
    - - Beach
  - - - Abrasion
        
        Waves contain rock particles that scour the coastline
        
        Rock rubs on rock
      - Attrition
        
        Rock particles collide with each other + coastal rocks
        
        Becomes smaller + rounder until they become sand
      - Hydraulic Action
        
        Waves break against a cliff face + compresses air + water trapped in crevices
        
        Wave recedes = pressure released = air + water suddenly expands + crack widens
        
        11,000 kg/m3 is average pressure exerted by Atlantic waves
      - Pouding
        
        When mass of breaking wave exerts pressure on rock = it weakens
      - Solution
        
        Dissolving minerals e.g. magnesium carbonate minerals, in coastal rock
        
        Limited significance unless water is locally polluted and acidic
    - - Solution
        
        Minerals that have been dissolved into the mass of moving water
        
        Load is invisible
        
        Load will remain in solution until water is evaporated and the precipitate out of solution
      - Suspension
        
        Small particles carried by currents
        
        = muddy appearance of sea water
        
        Larger particles carried during storm events
      - Saltation
        
        Series of irreg. movements
        
        Mat. is too heavy to be carried continuously in suspension
        
        Turbulent flow = sand-sized particles entrained (carried an short distance and dropped0
        
        Other particles can be dislodged by the impact = water gets beneath them = entrainment
      - Traction
        
        Largest particles in load may be pushed along sea floor by force of flow
        
        Movement if seldom continuous
    - - Mat. is deposited when there is a loss of energy caused by a decrease in velocity and/or vol. of water
      - Occurs where/when
        
        Rate of sed. accumulation exceeds rate of removal
        
        Waves slow down immediately after breaking
        
        Water no longer moves for a brief movement at the top of the swash
        
        Water percolates into the beach material during backwash
        
        Areas are sheltered from winds + waves - low energy environments
      - Settling velocity
        
        Velocity at which particles are deposited
        
        As flow velocity decreases. particles are deposited sequentially
- - - - Rock Cohesion
        
        In cohesive rocks, the grains are cemented e.g. sandstone, this is resis. + slows erosion
        
        Not cemented e.g. clay = quickly eroded
        
        How the rock is put together
      - Lines of Weaknesses
        
        Joints + bedding planes are more easily eroded by hydraulic action
      - Composition
        
        Quartz - eroded slowly
        
        CaCO3 eroded quickly e.g. limestone
        
        Soluble in acidic conditions
      - Porosity
        
        Amount of pore spaces in rock
        
        Amount of water a rock can hold
      - Permeability
        
        The rate at which a fluid flows through the rock
        
        When a rock is saturated, it begins to disintegrate e.g. clay
    - - Precipitation
        
        Increased precip. = increased chem. weathering
        
        Increased in warm climates
      - Temperatures
        
        Warm = increased chem. weathering
        
        Cold = increased physical weathering e.g. freeze-thaw
        
        Freeze-thaw only occurs in conditions where the temps. fluctuation above + below 0 degrees
  - - - Clay minerals expand + stresses are set up by repeated cycles = rock breaks - slacking
      - Common in ITZ
      - Softer rocks will expand when wet + contract when dry = cracking which weakens the structure over a period of time
    - - Affects well-jointed, fractured + porous rock
      - Results from waves, spray + tides = sea water enters the rock
      - Salt precipitates = crystals
      - Crystals grow as they dry, prising the rock apart - honeycomb
      - Sodium sulphate + carbonate expand by 300% when temps. fluctuate around 26-28 degrees.
    - - Affects well-jointed, fractured + bedded rocks - even in v. resistant rocks
      - Water enters cracks, joints + bedding planes
      - Water expands by 10% when it freezes = pressure on rocks = progressive weakening + failure
      - Produces a residue of angular fragments - scree
    - - Insolation weathering
      - Igneous rocks e.g. granite
      - Thermal expansion + contraction occurs during temp. rising + falling over a 30-50 degree range
      - Exposed surfaces heat up + expand more than the cooler rocks beneath the surface
      - Causes the rocks to spall into curved sheets - onion skin weathering
      - Considered to be effective only if water is present
    - - Overlying rocks removed by weathering + erosion = underlying rock expands + fractures parallel to surface
      - Exposes sub-surface rocks e.g. grantie
      - Parallel fractures - known as pseudo bedding planes
  - - - Affects well-jointed + bedded limestone
      - Limestone contains CaCO3 that reacts with the acidic water = Ca bicarbonate which dissolves in water
      - Rain + pore water combines with dissolved CO2 from atmosphere = weak carbonic acid
        
        Air in the soil is rich wiht CO2 form plant decay = acidifies rainwater more
      - Carbonate is removed in solution
        
        Causes rock to disintegrate
        
        Leaves a residue of insoluble clays
        
        Dissolves sediments = rock decay
      - Reversible process - precipitation of calcite occurs during evaporation of Ca-rich water in caves
        
        = stalagmites + stalacites
    - - Affects rocks with Fe minerals e.g. sandstones
        
        Fe2+ becomes Fe3+
        
        Fe minerals mix with O2 = Fe2O3 which rusts
        
        Collapse of molecular structure
        
        Fe becomes soluble under extreme acidic conditions
      - Some minerals in rock react with oxygen in air of water
    - - Affects rocks rich in feldspars e.g. granite + sandstones
      - Water enters the cracks, joints, fractures + pores
      - Silica + carbonate are lost in solution
      - Chemical reaction between rock minerals and water
      - Water + silicate minerals = secondary minerals e.g. clays
      - Is quickened if the water contains carbonic acid
        
        H+ ions react with the mineral ions
      - Feldspar (granite) + H (water) = kaolin (China clay)
    - - Affects lichens + decaying organic matter (humus) on any rock
      - Organic acids enter joints, fractures + pores
      - Organic acids attack certain minerals, releasing Fe + Al
      - Al + Fe are lost in solution = rock disintegration
    - - Some salts are soluble in water
      - Fe is only solubble in very acidic water
      - Mineral specific processes can be identified e.g. carbonation
    - - Water molecules added to rock minerals + new minerals of a larger volume
      - Anhydrite takes up water = gypsum
      - = surface flaking bc some minerals expand by 0.5% bc they absorb water
  - - - Grow in cracks/joints and exert outawrd pressure - similar to freeze-thaw
      - Exert leverage on rocks on soil as trees topples = exposure of rock + soil for further weathering
      - Burowing animals = exposure of further mat. for weathering
      - Significant on cliff tops + faces
    - - Produced during decomposition of plant + animal litter
      - = soil water becomes more acidic + reacts with some minerals - chelation
      - Blue-green algae produce a film on iron and magnese oxides on rocks
      - Molluscs secrete acids = small surface hollows on shore platforms
- - - - Slides, slumps, flows
    - - Falls, toppling, landslides
    - - Rock fall
        
        40 degrees or more - esp. if face is bare
        
        Rocks detatched by physical weathering
        
        Wave processes remove mat. at cliff base or it accumulates as relatively straight scree slope
      - Slides
        
        Linear
        
        Movement along a straight line slip plane e.g. fault/bedding plane between rock layers
        
        Undercutting by wave erosion at base of cliff = no support for mats. above
        
        Rotational
        
        Movement along a curved slip plane
        
        Common in weaker rocks e.g. clay
        
        Rock becomes heavier when wet - adds to downslope force
        
        Layer of sand above clay = rainwater cannot penetrate impermeable clay = increased pore pressure in sands
  - - - Binds slopes together
      - Lack of veg. = more susceptible
    - - Removes mat. from base of cliff - undercutting
      - Keeps cliffs steep
      - Leave lower cliff unstable
    - - Pore spaces can make up as much as 30% of the rock vol.
      - Pores hold water = increased mass of rock
    - - Water can saturate the soil + rocks = loss of strength + failure
      - Reduces friction + increases the mass of material so that it is more likely to move
      - Dry periods allow the ground to dry out + crack so that the next rainfall can infiltrate the ground rapidly = fast mass movement
    - - Jointing, bedding + variation in porosity + permeabilty
    - - Coastal protection
      - Change the movement of LSD
      - Leaves some areas deprived of sediment + vulnerable to wave attack
      - Rock armour can be used to protect the cliffs but is unsightly
  - - - Soil Creep
        
        Individual soil particles are pushed to the surface by wetting, heating and/or freezing
        
        Move at right angles to the surface bc it is the zone of least resistance
      - Rain Splash
        
        Compacts soil + dislodges particles equally in all directions
    - - Surface Wash
        
        When soil infiltration capacity is exceeded, gullies are formed
        
        Water drains across saturated/frozen ground after heavy downpours or snow melt
      - Sheet Wash
        
        Occurs on footpaths + moorlands
        
        Unchannelled flow of water over a soil surface
        
        Areas of high velocity are separated by areas of low velocity on a slope
        
        Transports materials dislodged by rainfall
        
        Can form steep, narrow gullies
      - Throughflow
        
        Water moving down thru soil + channeled into natural pipes = sufficient energy to transport materials
        
        Its energy + solute load = considerable vol.
      - Mud Flow
        
        Occurs where the rock is predominantly clay, mudstone or shale
        
        Mat moved by landslides can liquefy to form a mudflow
    - - Slides
        
        Sliding mats. maintain shape + cohesion until impact
        
        Causes large + slumped terrace
        
        Mat. moved by landslides can liquefy into a mudfloe
      - Falls
        
        Occur on steep slopes - > 70 degrees
        
        Initial cause is often weathering
        
        = scree slopes + slumped terraces
        
        Short fall = straight scree
        
        Long fall = concave scree
        
        Important sed. source for rivers on high land
      - Slumps
        
        Occur on weaker rocks e.g. clay
        
        Have a rotational movement along a curved slip plane
        
        Clay absorbs water, becomes saturated + exceeds its liquid limit + then flows along a slip plane
  - - - Danger form hazards on a number of factors
      - Risk may be low if the event occurs rarely or is not particularly dangerous
      - Risk equation: (Freq. / Magnitude * Level of Vulnerability) / Capacity of Population to Cope
      - Severity also depends on the response of the population
    - - Closure of beaches
        
        Greater risk of accidents when there are more people
      - Signage
      - Fencing sections of beach
    - - Protective measures can be ignored
        
        Fossil collectors often rummage among rock falls
      - Measures destroyed by high tides + further mass movements
  - - - Is a World Heritage Site
      - English Channel coast of S England
      - Exmouth, E Devon to Studland Bay, Dorset - 96 miles
      - Regular rock falls + landslides
    - - Dorset Coast
        
        Several different rock types = variet of landforms
        
        Clay is underlain by chalk
        
        Shale underlain by limestone
        
        Softer rocks give way first
        
        High energy coastal environment
        
        2 main types of mass movement
        
        Landslides - mat. moved by landslides can sometimes liquefy to form a mudflow
        
        Mudflows - when rock type is predominantly clay, mudstone or shale
      - All its rocks are sedimentary:
        
        Sandstone, clay, limestone
      - Cliffs are not supported on seaward side + may slump due to gravity
        
        Likelihood may be increased by marine erosion
        
        Removes mat. from the base of cliffs (undercutting) = steep + unstable
    - - 50% more rainfall than the area averag ein 2012
      - Saturated the soil + rock = loss of strength + failure = various mass movments
      - Halfway along the Jurassic coast
      - Very dry months at the start of the year follower by very wet months
      - No month after June was below the rainfall average
      - Previous 2 years had been very dry also
        
        Dry weather = ground dried + cracked = rainfall infiltrates quickly = fast mass movements
    - - Property
        
        Mass movement at Monmouth Beach, Lyme Regis, disturbed beach huts and chalets - one of which was purchased for £140,000
        
        Rock falls at Sidmouth
        
        Affected properties to the E of the town
        
        Gardens are being lost
        
        Eventually the properties themselves will be at risk + become worthless
    - - Agricultural land lost as cliffs crumble
      - Housing value decreasing
      - Public footpaths constantly monitored e.g. SW Coast Path - several section closed
      - Bad press associated with tragic events damage economy of area
      - Coastal Defences: Sidmouth
        
        Defences have worsened the situation
        
        Defences were introduced in 1995 below the promenade
        
        Groynes, Breakwaters, Beach Replensihments
        
        Peennington Points - E of the town
        
        Starved of beach sediment as the W-E movement of LSD has been stopped by the defences
        
        Increased wave attack
        
        Owners want rock armour but it unsightly and may cause the loss of the World Heritage Status for the Dorset + E Devon Coast
- - - - Wind-blown mats.
      - Cliff weathering + mass movements
      - Human activities
      - Onshore deposition, LSD + Rivers
  - - - Only small streams feed the lakes so they aren't able to break thru the tombole
    - - Connects Dorset to Isle of Portalnd
      - 18 km long
      - Longshore size grading
        
        Pebbles come from SW
        
        Pebbles are 1-2cm at West Bay; and 5-7.5cm at Portland
        
        Pebble size increases to the E
- - - - Groynes keep sed. in place
    - - Looks at where sed. is moving + effects on a large scale
      - Mapping movements of mats in literal cells - circular sediment movement
      - Some movement of mats. between cells
  - - - Larger particles roll on the sea floor
    - - Sand grains skip along the sea bed
      - Arc shaped trajectory
      - When indv. grain land, they move others
    - - Sand + finer particles
      - Continuous movemets by turbulent water
    - - Minerals dissolved in water
  - - - Offshore winds, change in beach gradient, behind a spit/bar or in a cove
  - - - Shingle - energy is dissipated bc of percolation in coarser sed. with little backwash
        
        So mat. is moved up but little is returned = steep profile
    - - Low Wave Energy
        
        Steep profiles - 11 degree
        
        Reflect wave energy back into sea
        
        Waves travel up beach as swash
        
        Constructive wave action
        
        Backwash returns before the next swash + therefore does not interfere with the next waves
        
        Sed. transported up the beach
        
        Steep summer beach profiles with berm at the back
      - High Wave Energy
        
        Gentle profile - 5 degrees
        
        The incline dissipates wave energy
        
        Waves are close together
        
        Swash is interrupted by the return of backwash + therefore can't transport sed. up the beach
        
        Sed. is removed from the beach by offshore destructive wave action
        
        Beaches have runnels/gullies cut by small rip channels
        
        Storm/winter profile
  - - - Wave crests are parallel to the shoreline
      - Waves are fully refracted
      - Sed. moves up + down the beach
      - Landforms
        
        Prochet-shaped beaches
        
        Current-shaped coves - waves are refracted = swash-aligned beach
        
        Small rip currents - beach cusps
        
        Onshore bars/barrier beaches
    - - Wave crest approaches beach at an angle = LSD
      - Beaches fed by sed. grow outawrds from coast
      - Landforms
        
        Abrupt change in coastline = detached beaches, spits + tombolos
        
        Wave refraction around the end = recurved ends
        
        Relic ends - indicate stages in beach growth
        
        Spits - in areas of low tidal range
- - - - Rivers entering sea are carrying sed. loads
      - Broad continental shelf margin at river mouth = platform for sed. accumulation
      - Low energy environs. exist in coastal areas
      - Low tidal ranges
    - - = channel splits into 2
      - = 2 channels with reduced energy levels = more deposition + further dividing
    - - = deposition of lobes of sed. in low-lying areas between levees
  - - - Sed. accumulation = a pointed extension to the coastline - this is shaped by regular gentle currents from oppo. dirs.
    - - Sufficient sed, is available for delta to grow seawards
      - Wave action is strong enough to smooth + trim its leading edge
    - - Distributaries bilid out from the coast in a branching pattern
      - River sed. suppyl exceeds the rates of removal by waves + currents
  - - - Furthest inland
      - Beyond reach of tides
      - Composed entirely of river deposits
    - - In the ITZ
      - Regularly submerged
      - Composed of both river + marine deposits
    - - Lies below LWM
      - Composed mostly of marine sed.
      - Represents the seaward growth of the delta
  - - - Foreshore plain
        
        Elongated ridges
        
        Lagoons
        
        Alluvial deposits in depression between marshes
        
        Salt marshes
      - Frontal plain
        
        S of forsehroe plain
        
        Scattered eroded limestone outcrops + clay deposits
      - Sandy zone
        
        Variety of sand formation
        
        Sheets, dunes, hummocks
    - - Huge sed. load despite relatively low discharge
      - 600mm annual rainfall
      - Low-energy coastal environment
      - Rates of fluvial deposition exceed rates of marine erosion for 3000 years
        
        This is now changing bc of human + physical factors
      - Nile is 6650km long
      - Huge catchment area - over 3m km2
    - - NW winds over Mediterranean Sea for most of year = constant eastward movement of water + sed.
      - Underwater sand bars
        
        Typical of tideless seas
      - Parallel bars
        
        Extend from Abu Qir to Port Said
        
        Generated by dominant eastward LSD
      - Crescentic bars
        
        Found on beaches W of Abu Qir headland
        
        Associated with rip currents
    - - Aswan High Dam
        
        Built in 1964
        
        Created an imbalance between erosion + accretion
        
        Is changing the delta from a low-energy environment
        
        Higher sea levels (1.2mm/year) = higher erosion rates
        
        Deeper water = larger waves w more energy + they reach further inland
        
        Rapid decrease in amount of sed. accreted
        
        = accelerated erosion + coastal retreat along shoreline of the NW delta
- - - - Electrical charges = these fine mats. clump together in saline conds. = become heavier + sink to sea bed
- - - - Affect + modify the cliffs + foreshore above wave heights
      - Weathering + mass movements
    - - Affect the coastline below wave heights
      - Erosion - transportation + deposition
      - Hydraulic action, abrasion, attrition, solution
  - - - Freeze-thaw, pressure release, thermal expansion, salt crystalisation
      - Oxidation, carbonation, solution, hydrolisis, hydration
      - Tree roots, organic acids
    - - Rock fall
      - Slides
    - - Erosion
        
        Abrasion, attrition, hydraulic action, pounding, solution
      - Transportation
        
        Solution, suspension, saltation, traction
      - Deposition
    - - Erosion, transportation, deposition,
    - - Erosion, transportation, deposition
- - - - Blows from NW all year
      - Shamal winds are winter storm winds (10m/second) + form waves >1m
        
        Waves are dissipated by offshore banks
      - Carry sed. landwards ontp the sabkha
      - Breach + erode dunes, + build offshore bars
      - LSD moves mats. eastwards by the NW winds
    - - Large tidal range >1m/year
      - Low salinity water enters from the Straits of Hormuz
      - Evaporation increases density + a deep water reverse estuary flow occurs out of the SofH
      - Density-driven circulation is the main part
      - Wind dominated circulation in the MW - deposits around the peninsula
    - - Tides + tidal currents operate + carry sed. in the lagoons
      - Offshore tides are E-1
      - They reach high velocities in channels = small tidal deltas
    - - Semi-arid + tropical
      - Evap. is greater than both river inflow + precip. at 500 cm.year
      - Evap. is important for sabkha development
    - - As waves pass between barrier islands they refract = decreased energy + increased length = deposition
  - - - Intertidal sand flats
        
        Surfaces are ripple-marked + seaweed covered
        
        Landward side has mangroves, spits + bars
      - Break point bars
        
        Sand ridges parallel to caost
        
        Formed in storms by plunging breakers
        
        Energy loss is a result of refraction by seabed friction = deposition
      - Runnels + bars
        
        Bars - formed by swash of breaking wavs
        
        Runnels - formed by backwash + rip currents
    - - Tidal channels
        
        In offshore banks
        
        Some cut by flood tide currents
        
        Some have tidal ebb deltas at seaward end
      - Megaripples
        
        Longitudinal + transverse ripples
        
        Shape is controlled by:
        
        Sed. supply
        
        Sed. grain size
        
        Waater depth
        
        Current velocity
        
        Formed by fast-moving currents
    - - Barrier islands
        
        Growth from offshore beaches
      - Tombolos
        
        Leeward growth of barrier islands
      - Coastal plan
        
        Accreation of suprtidal, intertidal + lagoon sediments
      - Sabkha
        
        Low gradient salt flats
        
        Composed of unconsolidated carbonate sed. + evaporite mat.
    - - Coral reefs
        
        On offshore shoals
        
        Includes brain corals + reef builders
      - Reef fronts
        
        On seaward side of shoals
        
        Some coral pinnacles
        
        Micro atolls
        
        Coral spurs
    - - Bushes + trees in narrow strips at top of intertidal flats parallel to the sea
        
        Protected from wave action
      - Covered roots at high water
        
        Replace salt marshes in temperate areas
  - - - These restrict circulation
    - - Energy decreases
      - Length increases
      - Material is deposited
        
        These mats. will then form a tombolo
- - - - Sand grains are relatively heavy so they are not carried in suspension
      - Restricts abrasive erosion to 1m = limited effect
    - - Particles are carried greater distances
      - Particles are not protected from collisions by film of water around them
  - - - Friction from veg + surface irregularities are greater than in open ocean
- - - - Cracks in rock contain tiny pockets of air
      - Water is forced into these cracks, compressing the air particles
      - When water retreats, the sudden release of tension causes air pockets to explode
    - - They are exposed at low tide
      - They widen as the headland retreats
- - - - Contains salt traces
      - Rain water also has salt traces and picks up minerals as it weathers other rocks = increased acidity
      - This rainwater joins streams + rivers that flow into the sea + deposit the salt
    - - Some areas are very salty if there are no outlet rivers
      - Therefore the water evaporates, leaving the salt - this means that there is a higher conc. of salt
    - - Found on the sea floor where they heat water
      - Heated water can absorb more salt
      - The sea water goes through the vent, is heated by geothermal energy and expands out
    - - The lava reacts with the salt water + heats it
      - The heated water can absorb more salt