GCSE Geography Volcanoes

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  • Created by: Jonafon
  • Created on: 22-03-16 19:54
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  • Volcanoes
    • They are found at Destructive and Constructive Plate Margins
      • Destructive
      • Constructive
        • The magma rises up into the gap created by the plates moving apart, forming a volcano
      • Some volcanoes also form over parts of the mantle which are really hot (hotspots) e.g Hawaii
    • 3 Different types of Volcanoes
      • Composite volcanoes (Mount Fuji, Japan)
        • Made up of ash and lava that's erupted, cooled and hardened to layers
        • Lava flows slowly and is thick
        • It hardens quickly to form a steep-sided volcano
      • Shield volcanoes (Mauna Loa on the Hawaiian islands)
        • Made up of only lava
        • Lava is runny, flows quickly and spreads over a wide area
        • Forms a low, flat volcano
      • Dome volcanoes (Mount Pelée in Caribbean)
        • Made up of only lava
        • Lava is thick. Flows slowly and hardens quickly
        • Forms a steep-sided volcano
    • Volcanoes and Earthquiakes are Tectonic Hazards
      • Tectonic hazards are natural hazards caused by the movement of tectonic plates
        • Natural hazard is a naturally occurring event that has the potential to affect people's lives or property
          • When they do affect peoples lives or property, they are called Natural Disasters
    • Impacts of volcaoes
      • Reasons why people live close to volcanoes
        • Soil around volcanoes is fertile because its full of minerals from volcanic ash and lava. Its good for growing crops, this attracts farmers
        • Volcanoes are tourist attractions. Many people live near volcanoes to work in tourist industry
        • Volcanoes are a source of geothermal energy, used to generate electricity. People live around them to work at power stations
    • Impacts of volcanic eurptions
      • Primary
        • Buildings and roads are destroyed by lava flows and pyroclastic flows. Buildings collapse if enough ash falls on them
        • People and animals are injured or killed mainly by pyroclastic flow but also by lava flows and falling rocks
        • Crops are damaged and water supplies are contaminated when ash falls on them
        • People, animals and plants are suffocated by carbon dioxide
      • Secondary
        • Lahars (mudflows) form where volcanic material mixes with water (snow melt). This causes more destruction, injuries and deaths
        • Fires are started by lava flows and pyroclastic flows, which then spread
        • People may suffer psychological problems if they knew people who died or lose their homes
        • People are left homeless
        • Shortage of food because crops are damaged
        • Shortage of clean water
        • Roads are blocked so emergency vehicles and aid cant get through
        • Sulfur dioxide released causing acid rain
        • Business are damaged or destroyed which causes unemployment
      • Impacts are more severe in LEDCs than MEDCs
        • low quality of housing, less stable, easier destroyed by earthquakes
        • Poor quality of roads make it harder for emergency services to reach injured people so more deaths
        • Not enough money to earthquiake proof buildings or have resources to react straight away so more people are effected by secondary impacts
        • Healthcare is worse so they dont have enough supplies to deal with lots of casualties so people die from treatable injuries
    • Reducing impacts of Volcanoes
      • Prediction
        • Scientists can monitor signs before an eruption
        • tiny earthquakes, escaping gas and changes in shape of volcano mean an eruption is likely
        • Gives people time to evacuate, reduces deaths and injuries
      • Planning
        • Future developments can be planned to be built in areas of low risk from eruption
        • Firebreaks reduce fire and emergency services can train and prepare
        • Evacuation routes can be carefully planned if it was to happen
      • Building techniques
        • Buildings can be strengthened to withstand falling ash
        • Lava diverted using barriers
      • Education
        • Government educate what to do if an eruption happens, how to get out
        • people can be told how to make a survival kit
      • Aid
        • Receive aid like food, water, money and people (doctors)
        • Help reduces impacts (stops people going hungry)
    • Supervolcano
      • They develop at destructive plate margins or Hotspots
        • Hotspots
          • Magma rises up through the cracks in the crust to form a large magma basin
            • This pressure of the magma causes a circular bulge on the surface (several kilmoetres wide)
              • The bulge cracks, creating vents for lava to escape. Lava erupts out of vents causing earthquakes and sends gigantic plumes of ash and rock
                • as magma basin empties, bulge is no longer supported so it collapses spewing more lava
                  • When the eruption is finished, a Caldera (big crater) is left where the bulge collapsed. These get filled with water to form a large lake
      • They are flat, cover a large area (much bigger rthan normal volcanoes) and have a Caldera (crater at the top)
      • Ash shoots kilometres in the air, blocking out daylight over continents, causing mini ice ages as less heat energy from the sun gets to earth

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