Restless Earth

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  • The Restless Earth
    • Unstable Crust
      • Middle of the earth-core around that is the mantle, the top layer of the earth is called the crust.
      • 2 types of crust
        • Continental- less dense but thicker (30 km)
        • Oceanic- denser and thinner (5 km)
      • Tectonic Plates
        • 7 large tectonic plates and lots of smaller ones.
        • Some tectonic plates are: African , South American, Pacific
    • Plate Margins
      • Conservative
        • Plates slide past each other.
          • Sometimes they are going the same way but at different speeds.
        • Feature
          • Earthquakes
      • Constructive
        • Two plates move apart, magma rises to fill the gap.
        • Features
          • Usually found under the sea.
          • Shield volcanoes.
          • Volcanoes can form islands if they rise above sea level.
      • Destructive
        • Plates move together.
        • Lighter continental crust stays onto while the denser oceanic crust is pushed down.
          • Pushed into the mantle where it melts.
        • Features
          • Composite volcanoes.
          • Earthquakes
          • Fold mountains
          • Ocean trenches
    • Fold mountains and ocean trenches.
      • Ocean trench
        • Formed in the subduction zone.
        • One wall is formed by the subducting oceanic crust.
          • The other wall is the edge of the continental crust.
      • Fold mountains
        • Occur at destructive plate margins.
          • Alps, Himalayas and Andes
    • Fold mountains Info
      • Alps
        • Summer tourism based on the scenery.
        • Livestock graze on valley floor.
        • Rich soil on valley floor so crops are grown there.
        • Travel, railway tunnels have been cut through the mountains to make travel easier.
        • Winter tourism based on skiing- steep snowing slopes.
        • Steep valley sides and fast flowing mountain rivers are perfect for HEP.
    • Volcanoes
      • 2 main types of volcanoes, composite and shield.
        • Sheild
          • Runny lava
          • Regular and frequent eruptions
          • Not explosive
          • Gentle slopes and wide base.
          • Pours out smoothly.
          • Example Surtsey Island, near Iceland.
          • Magma rises to fill gap between plates.
        • Composite
          • Magma is forced up to the surface through cracks in the crust.
          • Viscous lava
            • Violent eruptions.
              • Example Etna, Italy
          • Cone shape, steep sides, narrow base.
          • Irregular eruptions with long dormant periods.
      • Supervolcano
        • 1000 times bigger than a normal volcano.
        • After an eruption the magma chamber collapses, forming a caldera.
        • Last known supervolcano was 75000 years ago.
    • Volcanoes as hazards
      • Positive Impacts
        • Fertile Soils
          • Tourist Attractions
            • Natural Hot Springs
      • Negative Impacts
        • Always Destructive (both types of volcano)
          • Global Destruction e.g Ash Clouds Disrupt Travel
            • Unpredictable so its difficult to prepare for them
      • Primary Effects
        • People injured/killed
          • Buildings/ Farmland Destroyed
            • Communications Desrupted
      • Secondary Effects
        • Costs of Rebuilding
          • Tourists Might Stay Away
            • Ash Improves Soil Fertility
      • Case Study
        • Montserrat 1995-1997
          • In the Carribbean
            • On a Destructive Plate Margin
          • Cause: Magma forced up through weak points in volcano.
          • Primary Effects
            • 20 people killed
              • 2/3 of homes destroyed and farmland
                • 5000 people evacuated
          • Secondary Effects
            • Costs of rebuilding
              • Tourist industry disrupted
          • Immediate Response
            • Evacuation
              • Emergency help to provide temporary shelters
          • Long-term Response
            • UK aid to rebuild infastructure
              • Volcano Observatory built to monitor volcano
                • Attempt to re-attract tourists
      • Predicting Eruptions
        • 1. Tiltmeters - Check for bulges on volcanoes slope
          • 2. Satelites - Monitor changes in the heat activity
    • Earthquakes
      • Facts
        • Can happen on all plate margins but most common on destructive plate margins
        • Features
          • Focus - Point where earthquake happens underground
            • Epicentre - Point on surface above focus (effects of the shock the worst)
              • Shockwaves - come out at all directions from the focus.
        • Higher number of deaths can be caused by a high density population or self built houses.
      • Measuring Earthquakes
        • Richter Scale - To measure the earthquakes magnitude from values 1-10.
          • Mercalli Scale - Measures its impact on people.
    • Earthquakes hazards
      • Primary effects - straight after
        • Deaths injures
        • Damage to buildings
        • Damage to roads, bridges, railways
      • Secondary effects - afterwards
        • fires caused by broken gas pipes/ electricity pylons
        • Landslides
        • Spread of disease cause sanitation
        • Tsunamis
      • Immediate response
        • rescue teams
        • medical care
        • Road clearance
      • Long-term response
        • Improving emergency procedures
        • Practising drills
        • Earthquake proof houses/ buildings
    • Tsunamis
      • Come after an earthquake.
      • How tsunamis happen
        • 1. Two plates get stuck and build up tension.
          • 2.Underwater earthquake happens as the tension breaks, bringing one plate upwards.
            • 3.Sea bulges upwards creating a huge swell of water.
              • 4.The swell reaches the coast and travels very fast inland.
      • Case Study
        • Asian Tsunami 2004
          • Caused by an earthquake underwater and the epicentre was off the coast of Sumatra, Indonesia.
          • Places that were effected- Sri Lanka, Indonesia, Thailand, India.
          • Over 220,000 people killed.
          • 500,000 houses destroyed.
          • Farmland ruined by the salt, tourism and fishing disrupted.

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