The tectonic Hazards

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  • The tectonic hazards
    • Earthquakes
      • A sudden and intense shaking motion that usually lasts for a few secons. It is caused by the 'Snapping' of rocks as enormous stresses, which may have built up over many years, are suddenly released
      • PRIMARY
        • Ground shaking
      • SECONDARY
        • Fires
      • Case studies : - Armenia 1988, Mexico City 1985
        • Mexico City 1985 - Long waves , Nature of surface (Dried up lake bed)
      • Vast majority occur on plate margins
      • EFFECTS
        • Nature of the bedrock
        • Strenght of the earthquake
        • Depth of focus
        • Wealth of a country
        • Building design and competance
        • Population distribution
      • Loma Prieta epicentre - San Francissco 1989
        • Primary - Marina district badly effected (27 fires)
    • Volcanoes
      • Pyroclastic flow
        • Humans can't out run them
        • PRIMARY
        • Kills in seconds
        • Occur under high pressure
        • Speeds of 200+kph
        • Reach upto 800 Degrees C
        • Case studies : - Mt Unzen, Japan 1991 - 34 killed, Mt St Helens 1980, Mt Vesuvious, Soufriere Hills, Monserat 1995-97
      • Only about 50 volcanoes are likely to errupt in a year and on average the death toll is 10% that of earthquakes
      • Basalt flow
        • PRIMARY
        • Humans are able to out run them
        • SECONDARY - Fires
        • Predictable - not too hazardous
        • Lava plateau
        • Rilavea, Hawaii
      • Tephra
        • Airbourne volcanic rock/ash
        • Consists of many rock types
        • Ash less than 2mm
      • Ash cloud
        • Can cause buildings to collapse under its sheer wieght
        • Icelandic volcano hazard
        • Ground flights - air traffic
        • Reduces visability
      • Bombs
        • Larger than 64mm
      • Landslide
        • SECONDARY
        • Mt St Helen's
      • Tsunami
        • Undert he sea, large ocean waves, earthquakes - Soufriere Hills 1997
        • Displacement of water
      • Flooding
        • Lahars
        • Landslides blocking rivers causing quakelakes
        • Significant flooding
      • Jokulhlaups
        • Grimsvoth 1996
        • Volcanic eruption under glacier
          • Melts the glacier to form a glacial lake
      • SECONDARY
        • Famine
          • Economic distruption
            • Loss of jobs, less jobs, less opportunities, SOL reduces
          • Crops destroyed
            • Decimated food supply
            • Problem for subsistent farmers (LEDCs)
      • Volcanic gases
        • SECONDARY - Global warming
        • Enormous cloud of CO2 - Silent and deadly
        • Lake Nyos, Cameroon - PRIMARY HAZARD - Killed over 1700 people
      • Lahars
        • When pyroclastic mixes with mud and water causing volcanic mud flows
        • SECONDARY
        • Most eadyl products of an eruption because they flow very fast down the river valledy, demolishing property and bridges, and litterally burying people alive in what amounts to a quick-setting cement
        • Thick hot slurry
        • Case studies : - Phillipines 1991, Nevada Derruiz 1985 - 23,000 killed in Armero
    • Liquifaction - when soil and rock acts like a liquid, buildings can collapse or become unstable
      • As a result of seismic waves running through the rock and soil

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