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Plate tectonics 1

Earthquakes – San Francisco 1906, 1989 (MEDC)

  • Two plates (N. American and Pacific) got locked and tension was built until the plates suddenly moved by – 6m (1906) and 1.2m (1989) (TRANSFORM MARGIN)
  • San Francisco was built on sand so when the ground shook, liquefaction occurred. This is when water is brought to surface.
  • 1906 – 8.2 Richter Scale
    • 450 people died
    • 25, 000 buildings destroyed
    • Sparks ignited gas escaping from pipes. Result: fire. Initially there were few deaths but the fire raged the whole town and buildings collapsed
    • Liquefaction cause a lot of buildings to tilt over
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Plate tectonics 2

  • 1989 – 6.9 Richter Scale
    • 63 people died
    • Fewer buildings collapsed as many are now earthquake-proof
    • Valves reduce chance of gas escaping
    • The double-deck Bay Bridge collapsed as it was not constructed well. Fire destroyed the Marina district as most buildings are wooden. It was also constructed on top of the rubble of previous earthquake.
  • Reasons for why people choose to stay
    • Most are highly paid – difficult to find similar jobs elsewhere
    • Always lived there (inertia) - moving would mean leaving friends and families
    • Technology (earthquake-proof buildings and monitoring equipment) – people feel safer
    • Believe in own good fortune

Volcanoes – Mt St Helens 18 May 1980 (MEDC)

  • Juan de Fuca Plate driven under west coast of N. American Plate.
  • Lighter material is forced to surface – this creates the volcanic cone
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Plate tectonics 3

  • The main vent has cooled so it’s blocked
  • Early May 1980
    • Bulge grows on the north-facing side of mountain (blocked vent)
    • Summit was 2950 m
    • Vegetation on slopes
    • There were several minor earthquakes and eruptions previously
  • 18 May 1980
    • An earthquake occurred, which caused bulge to move
    • Landslide filled Spirit Lake, causing a mudflow
    • Removal of ice and rock caused magma to explode sideways
    • Result: the top and northern side blasted off
    • Volcanic bombs, steam and ash
    • New summit – 2560 m
    • No vegetation left
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Plate tectonics 4

  • Effects
  • Trees within 10 miles blasted off
  • 61 people died (despite warnings). Remember old Harry Truman, who refused to leave and died during the eruption
  • Ashes reached as far as the east coast of America
  • Ruined crops
  • Roads, bridges, buildings destroyed
  • However, tourism flourished after the eruption as they want to see the site themselves
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Rivers 1

Floods - Lynmouth, Devon, 15 August 1952 (MEDC)

  • Reasons
    • Very heavy rain for 2 weeks before flood: ground saturated before flood
    • Another heavy storm on 15 August – water could not be saturated so they ran overland to rivers
    • Lynmouth is situated by a confluence, hence increasing chance of flooding
    • The West Lyn river had been ‘channelled into a culvert that proved too narrow’
    • Small bridges on the river trapped boulders and trees; this resulted to water being trapped as well (artificial dam). This ‘dam’ then burst causing a 12 m wave that swept the whole town
  • Effects
    • 34 people died
    • 90 buildings destroyed
    • 1000 people homeless
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Rivers 2

  • Attempts to prevent further disasters
    • setting up early warning system (evacuation)
    • West Lyn river allowed to run its natural course
    • Bridges rebuilt spans
    • Likely flooded areas are left without building plans

Floods - Bangladesh, 1998 (LEDC)

  • Reasons
    • 80% of Bangladesh on flood plain
    • Strong winds lead to storm: seawater is forced towards Bangladesh in autumn
    • Rivers flood in summer due to monsoon rain
    • Deforestation in Nepal – trees hold the ground together and without them a) soil is washed to river, raising water level, b) water flows directly on land and c) no interception
    • Global warming – 12% of Bangladesh can disappear in next 100 years
    • River Ganges used for irrigation upstream – less silt in downstream to build up the floodplain
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Rivers 3

    • Rising population – more wells  decrease in water table  slope collapse
  • Effects
    • 1040 people died
    • Over half the country flooded
    • 23 million homeless
    • 130 million cattle drowned
    • Crops ruined
    • Drinking water polluted
    • Communities destroyed
  • Attempts to reduce affects of future flooding: Bangladesh is an LEDC so advances are limited
    • Embankments to protect major settlements
    • Better warning systems
    • Better education
    • Afforestation in upstream
    • Special shelters above flood level
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Rivers 4


  • Coastal erosion - Holderness coast, Yorkshire.
    Tip: Remember the shape of the coastline as the man with a beard
    • Main rock is boulder clay so cliffs are unstable. Other main rock is chalk
    • Cliffs retreat by 1m a year
    • 50 villages that exist during the medieval times are lost today
    • 5 km of land already lost
    • Major features (in order from north to south) – Flamborough Head, Holderness Coast and Spurn Head
  • The Great Debate – Protect Mappleton/ B 1242?
    • Problem: Protecting an area of land always mean greater pressure and coastal erosion on neighbouring stretches of coast
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Rivers 5

(See OS map of Hornsea). Hornsea is a big town so groynes are necessary. However this means greater coastal erosion will occur in the south; meaning it would affect Mappleton. Mappleton is a small village but an important road, the B1242, runs through it and losing it would mean compensation of millions of pounds. Planners decided to protect it, but this would mean the coastal area down further south will suffer from greater erosion (10 metres a year).

FOR Build rock groyne - trap sand at Mappleton - southern coast and farms destroyed

  • One example would be Sue Earl, a farmer in Great Cowden. Although she had lost a lot of land every year, she was determined to keep the farm running. Eventually the sea will claim the whole farm so she had to give up, especially when the farmhouse went too.

AGAINST Do nothing - Mappleton and parts of B 1242 destroyed; huge compensation - sands continue protect southern coast and farms

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Population 1

Population densities – South Wales

  • Mountainous region (hills of over 500 m) – sparsely populated as it is cold and steep-sided (most people living there are sheep farmers)
  • Southern strip is lower and flatter, however
  • Once: The mountainous areas attracted high no. of people
    • These areas were once major world centres for coal mining/iron and steel industries
    • Raw materials can be found in mountains and valleys  mining jobs. Industries developed
    • Rail and road routes in mountain valleys
  • Now: The southern strip attracted high no. of people
    • This include the M4 running from east to west and the ports of Cardiff, Swansea and Talbot
    • Modern manufacturing e.g. Ford’s in Bridgend
    • Tertiary activities e.g. the Driver and Vehicle License Centre (Swansea)
    • Some old mining and steel towns, such as Tredegar, still survive although employment is difficult
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Population 2

Population control – China’s one child policy 1950s Large families encouraged to strengthen the nation

1960s Population accelerated without the influence of the government

1970s Advertising and family planning policies – population continued to rise still, however. It was estimated that the population will double in size in the next 50 years


  • Couples must have permissions to get married/have a baby. Large fines for ‘unauthorised births’ or enforced abortions and sterilisation
  • Benefits
    • Free education
    • Better housing
    • Better medical care
    • Etc
  • ‘Unauthorised children’ receive the opposite of what is listed above
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Population 3

1990s Public protest – second child is allowed in rural areas (it is also difficult to control these areas). Also, if the first child is female, a second child is permitted. Government is also trying to promote the idea of the policy through education

Positive results

  • Birth rate fell from 40 per 100 in 1968 to 17 per 1000 in 1980
  • Family size has fallen from 5.8 to 2.4 in 20 years
  • It is estimated that the policy has curbed 300 million people in 20 years

Negative results

  • High rate of ‘infanticide’, especially baby girls as boys are favoured more. Huge imbalance in both sexes are resulted **– dangers of population manipulation
  • Population is still rising despite of this policy – it has already passed 1200 million people
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Population 4

Migration – Turks to Germany 1950 Turkey - high rate of unemployment and low wages Germany - short of workers to do unskilled jobs

  • Result: Turkish workers invited to Germany as ‘guest workers’
  • Turkish families were encouraged to come as well – they live in cheap areas and it is difficult for them to learn German. Therefore, the two groups do not mix together

1970s Economic depression; many factories closed down

  • Result: unemployment – Germans, 10% and Turks, 20%
  • Resentment and suspicion between the two groups. Turks stay in Germany despite of low conditions as they are still needed to do the most low-paying jobs
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