Natural Hazards: Tectonic Hazards: Volcanoes

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  • Tectonic Hazards: Volcanos
    • Causes
      • Caused by movements beneath the Earth's surface.
        • The crust is broken into sections known as plates
          • They float on the less dense mantle.
            • As a result of convection currents in the Earth's mantle the plates either move towards or away from each other.
              • Oceanic and continental
                • Continental is less dense than oceanic
                • Continental is permanent whereas oceanic is constantly being destroyed and replaced.
              • Convergent, Divergent and Transform boundaries.
                • Convergent
                  • This is where  the continental and oceanic plates collide
                    • The oceanic is forced downwards into the mantle forming a subduction zone.
                      • This forms an oceanic trench.
                      • As the oceanic descends into the mantle the rock melts causing this melted rock to rise through the continental forming volcanic eruptions when it reaches the surface.
                    • The edge of the continental is folded upwards into a huge mountain range.
                      • Intensive folding makes rock in both plates break and slip causing earthquakes.
                • Divergent
                  • Where plates move away from the each other.
                    • The crust is pulled apart, the block between the faults, crack and falls into the mantle.
                      • This forms a rift where magma seeps upward to fill the cracks.
                        • This causes new crust but also earthquakes occur along the faults and volcanoes are formed where magma reaches the surface.
                • Transform
                  • This is where plates slide past each other.
                    • They do not slide smoothly and often get stuck and jot out forward causing shock waves that cause earthquakes.
    • Volcanoes
    • Is it safe to live near a volcano?
      • Reasons to:
        • Geothermal energy
          • Energy can be harnessed by using underground steam resources that have been heated by the earth's magma
        • Mineral rich soils
          • Ideal for farming
          • Lava and material from pyroclastic flow are weathered to form nutrient-rich soil.
        • Tourism
          • Creates jobs for people in tourism
        • Mineral for mining
          • Lava deep within the earth contains minerals that can be mined when cooled such as gold, silver, diamonds.
    • How can you predict volcanoes?
      • Composition of gas escaping from a volcano can indicate that an eruption is about to take place.
      • The amount of water flowing off the volcano can be measured (hydrology). If the discharge increases or the density changes , it can signal eruptions


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