Geography - Physical

Physical
1. Coasts
  1. Wave energy
    1. Depends on
      1. The strength of the wind
      2. The duration of the wind
      3. The fetch
  2. Weathering
    1. Physical
      1. Pressure release
      2. Freeze-thaw
      3. Temperature changes
      4. Salt crystal growth
      5. Wetting and drying
    2. Biological
    3. Chemical
  3. Mass movement
    1. Rock falls
    2. Mudflows
    3. Land slides/slumping
  4. Coastal erosion
    1. Hydraulic action
    2. Attrition
    3. Corrosion
    4. Abrasion/corrasion
  5. Bays and headlands
    1. Indented
    2. Variable geology
    3. CS: Swanage bay, Dorset
      1. South England
      2. Headlands
        Ballard point (N)
        Chalk
        Peveril point (S)
        Limestone
      3. Swanage bay
        Soft clays and sand
    4. CS: The erosion of ballard point to for caves arches and stacks
      1. Wave energy concentrated around headlands
        Due to refraction
      2. Erosion
        Hydraulic action
        Abrasion
        Corrosion
      3. Formations
        Cave
        Arch
        Stack
        Old Harry rocks
        Stump
      4. Wave energy is reduced around bays
        Due to refraction
        Sediment dropped
        Forms beach
        Protects bay from erosion
        From headlands
  6. LSD
    1. Transportation of sediment
      1. Solution
      2. Suspension
      3. Saltation
      4. Traction
    2. Longshore drift
      1. Waves approach obliquely
        Wave breaks
        Swash may carry sediment
        Water runs up beach at an angle
        Water runs out of energy
        Backwash runs directly down the steepest part of the beach
        Backwash may carry sediment
        Sediment returns to sea further along the beach
      2. Zig-zag
      3. Needs
        Waves to approach at an angle
        The swash and backwash to be strong enough to lift sediment
    3. Spits, bars and tombolos
      1. Where the cost changes direction waves are refracted and therefore loose energy
      2. Spits grow across river mouths or jut out to sea
      3. Saltmarsh forms behind spit
      4. Sometimes spits grow across bays until they form a bar
      5. CS: Blakeney spit
        North Norfolk
        South East England
        Aligned east to north-west
        Grown from east to west
        Diverts the mouth of the Glaven
      6. Hooks form when waves change direction
      7. Made more permanent by:
        Pebbles thrown on top during storms
        Sand dunes formed by wind blowing across the beach
  7. Beaches
    1. Made of loose material, usually sand and shingle
    2. Conditions needed:
      1. Waves are gentle
        Lets sediment settle
      2. Wave build up matterial
    3. Types:
      1. Bay-head
        Form in bays
        Waves loose energy and drop sediment due to refraction
        Sediment comes from eroding headlands and is transported by 'mini' LSD
      2. Pathway
        Narrow
        Occur where sediment is moving by LSD
  8. CS: Holderness - A rapidly eroding coastline
    1. Yorkshire
    2. Eroding rapidly
      1. 2m a year
      2. Reasons
        Cliffs made of unconsolidated grains of glacial clays and sand
        Easily eroded
        Waves cut a notch
        Material above notch slumps easily
        Hydraulic action
        Scouring
        2/3 of cliff material is clay
        Most erosion occurs after rain
        Clay can absorb rainwater
        Water adds weight
        Weight is greater than cliff strength
        Mass movement - Slumping
        Water separates the grains of the clay
        Weathering
        Freeze-thaw
        Wetting and drying
        Erosion is most rapid in winter
        More storms
        Storms blow more often from the N and NW
        Large fetch
  9. Management of coastal erosion
    1. Hard engineering
      1. Solid structures designed to prevent erosion/slow it down
      2. Stops sediment from reaching other parts of the coastline
      3. Interferes with natural processes
    2. Soft engineering
      1. Works with natural processes
      2. Less harmful to the appearance of the coastline
    3. Do nothing/manager retreat
      1. Allow the coastline to erode naturally
      2. Where value of land and property is less than the cost of defences
      3. People affected by this erosion do not recive compensation
      4. Sediment needs to be sent to other parts of the coast
    4. Types of defence
      1. Sea wall
        Curved concrete walls
      2. Rock armour/RIP-RAP
        Large boulders placed along the base of the cliff
      3. Gabions
        Wire cages containing pebbles built into the foot of the cliff
      4. Revetment
        Slanted wooden fences with slats built parallel to the cliff
      5. Groynes
        Long wooden/rock fences built at a right-angle to the beach
      6. Sea palling
        Off-shore walls of boulders
      7. Cliff drainage and re-grading
        Cliff drainage is put in so water is removed after rain
        Slope may be re-graded to a more gentle angle
      8. Beach nourishment
        Sediment is replenished
      9. Do nothing
    5. CS: Holderness - The management of erosion
  10. Coastal sand dune systems
    1. Winds blow sand from a beach onto the land
      1. Beyond the line of normal high tide
    2. Conditions needed:
      1. The wind needs to be frequent onshore winds
      2. The beach in front of the dunes must be wide so there is a good supply of sand
      3. The grains of sand must be fine so the wind can lift them
      4. Land behind the beach needs to be flat
    3. Plants
      1. Conditions that sand dune plants need to cope with
        Strong winds
        Salty enviroment
        Risk of being covered by sea water
        Strong sunlight
        Lack of nutrients
        Physiological drought
      2. Pioneer plants
        First to grow through sand
        Can grow through sand
        Long tap roots
        Wide roots close to surface
        Succulent leaves
        Tolerant of some salt
        Waxy cuticle
        Low nutrient demands
        Strong stem
2. Water on the land
  1. Erosion
    1. Abrasion
    2. Attrition
    3. Corrosion
    4. Hydraulic action
    5. Vertical in upper cource
    6. Horizontal in lower cource
  2. Movement of sediment
    1. Traction
    2. Saltation
    3. Suspension
    4. Solution
  3. Waterfalls
    1. Occur where the river crosses from hard to soft rock
    2. Soft rock is eroded faster
    3. Plunge pools form at the base of the waterfall
    4. The waterfall is undercut
      1. An overhang forms
    5. Overhang collapses
      1. The position of the waterfall retreats upstream
    6. Gorges form in front of the waterfall as they retreat
    7. Eventually the waterfall disapears
  4. Flood plains
    1. Meanders
      1. Migrate downstream
      2. Cut off interlocking spurs
      3. Straighten valley sides
      4. Widens and flattens valley floor
      5. Formed by erosion and deposition
        River cliffs formed by erosion
        The fastest current is slightly ahead of the outside bend
        Slip off slopes formed by deposition
        Slowest current on inside bend so sediment is deposited
      6. Ox bow lakes
        If the meander loops become too exaggerated the meander loop can get cut off
        Forming an oxbow lake
        The neck of the meander becomes narrower
        During a flood the river will break through the meander neck
        Straightening river
        Leaving meander loop detached
        Over time plants grow in the oxbow lake, it gets silted up and disapears
    2. Area covered by flood waters when river spills over its banks
      1. River drops alluvium
        Very fertile
      2. Levees form as heaviest sediment is deposited nearest to the river
  5. Features of rivers
    1. Source
      1. Where the river begins
    2. Mouth
      1. The point where the river meets the sea
    3. Tributary
      1. A smaller stream that meets a larger streem
    4. Confluence
      1. The point where two streams/rivers join
    5. Drainage basin
      1. The area around the river from which it takes its water
    6. Watershed
      1. The circumference of the drainage basin
  6. Inputs, outputs, transfers and storage
    1. Precipitation
    2. Interception
    3. Evaporation
    4. Solar radiation
    5. Drip flow
    6. Surface storage
    7. Infiltration
    8. Soil storage
    9. Uptake through roots
    10. Vegetation storage
    11. Transpiration
    12. Percolation
    13. Ground storage
    14. Surface flow
    15. Ground flow
    16. Through flow
  7. Factors affecting river flow
    1. The amount of precipitation
    2. How heavy the precipitation
    3. The length of time it has been raining for
    4. Snow melt
    5. Percentage of rainfall reaching the channel
    6. Speed at which precipitation reaches the channel
    7. Human activity
      1. Drains transfer water very quickly to nearest river channel
        Shape is designed to do this
      2. Roofs, gutters and road camber transfers water to the nearest drain
        Less evaporation
      3. Impermeable surfaces
        Prevents slower through and ground flow
        Water runs into drains
      4. Additional water from homes and industry
        More water added to river flow
      5. Removal of vegetation
        Less interception and evaporation
        Water hits ground at a faster speed
        Cannot infiltrate
        Flows as surface flow
        Less water taken into plants and lost by transpiration
      6. Drainage ditches transfer water quickly
      7. Compaction by animals and machinery makes infiltration and through flow difficult
  8. Hydrograph
    1. Precipitation is shown as a bar graph
    2. River flow is shown as a line graph
    3. Discharge is river flow
      1. Shown as m3/sec
    4. Lag time
    5. Storm flow
    6. Base flow
  9. Had and soft engineering solutions to flooding
    1. Hard engineering
      1. Straightening rivers
        Lining with concrete
      2. Dams
        E.g. Clywedog reservoir
    2. Soft engineering
      1. Warning
        hone, TV and internet
        Environment Agency
        Trained people warn people in their villages/local area
      2. Preparation
        Moving possessions upstairs
        Turn off gas and electricity
        Store supplies of dried food, water purification tablets and first aid
        Flood insurance
      3. Flood plain zoning
      4. Do nothing
        UK
        Allow flooding upstream
        Restore floodplain
        River restoration
        Bangladesh
        Rebuild after flood
        Preparation
        Warning system
      5. Other UK approaches
        Permeable surfaces
        Green spaces
        Removable barriers
        Planting trees
  10. CS: River Severn in Gloucestershire
    1. Causes
      1. Saturated ground
      2. Steep slopes and impermeable rock near source
      3. 120mm in 24 hours
      4. July 20th 2007
      5. Large urban areas
      6. Loss of vegetation
    2. Effects
      1. Water rose by 1-4 meters
      2. Gloucestershire was the worst affected county
      3. 2,225 properties were flooded
      4. Tewkesbury was cut off for several days
      5. 2000 people were evacuated to emergency centres
      6. Emergency services received 1800 calls
      7. Transport routes were disrupted for several days
        Thousands of people stranded on the M5 overnight
      8. Water treatment works was flooded
        140000 homes left without water for 2 weeks
        People collected water from bowsers or queued for bottled water
      9. 50,000 homes were without electricity for several days
      10. Tourism badly affected
        National Waterway Museum lost 700 customers - about £25,000
      11. Insurance premiums rise
      12. Some properties took months to dry out
      13. Financial costs
        Insurance claims for repairs around £165 million
        Cost to emergency services and the repair of transport and public palaces around £50million
        Cost to water companies for repairs and bottled water around £35 million
    3. Responses
      1. Immediate
        Forcasting
        Warnings
        Temporary flood barriers
        Home owners and businesses prepare
        2000 people evacuated
        Emergency services
      2. Longer term
        Insurance companies assess damage and begin repairs
        Some people stay in temporary accommodation for up to a year whilst damage is repaired
        Home owners and businesses make changes to lower levels
        Insurance companies insist that home flood defences are installed
        Authorities start to look at other solutions to the flood problems
  11. CS: Bangladesh
3. Restless Earth
  1. Crust
    1. The crust is the thin outer shell of the Earth
    2. It is brittle
    3. Consists of:
      1. Oceanic crust
        Thin, continuous shell around Earth
        5-10km thick
        Dense
      2. Continental crust
        Not continuous
        Up to 70km thick
        Sits on oceanic crust
        Light
    4. Lying on top of the mantle
    5. Broken into tectonic plates
      1. Move over the mantle
        Driven by convection currents
    6. Tectonic plates
      1. Some plates carry a continent and ocean crust and some just carry ocean crust
      2. Types of margin
        Destructive
        An oceanic plate and a continental plate colliding
        Collision
        Continental plates colliding
        Constructive
        Plates diverging
        Conservative
        Plates moving alongside each other
  2. Composite volcanoes
    1. Occur at subduction zones
    2. Form chains along plate boundaries
    3. Magma forms at about 70-100km below the surface
    4. Water trapped in the subducting oceanic plate is released into the surrounding mantle
      1. This lowers the melting point of the mantle rocks around it
    5. Magma rises due to its lower density
    6. Magma melts through continental crust
      1. This makes the magma more viscous
    7. A magma chamber forms as the mantle nears the surface
      1. Pressure is lower
      2. Water and gases form bubbles
        Bubbles cannot escape as the magma is too viscous
        Can be trapped if the vent is blocked
    8. Once a critical volume of magma and gas accumulates there is a sudden explosive eruption
    9. Features
      1. Magma chamber
      2. Main vent
      3. Crater
      4. Ash
      5. Vapour
      6. Gas
      7. Bombs and pumice
      8. Lava flow
      9. Pyroclastic flow
      10. Cone
      11. Secondary vent
      12. Secondary cone

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