global issue topic

• There are 4 layers to the earth

  1. Crust
  2. mantle
  3. outer core
  4. Inner core
• the crust is a brittle layer
• the mantle is made of magma
• the outer core is a liquid layer made of iron and nickel
• the inner core is a solid ball made of iron
• Continental drift is a theory which explains the world was made up of a single continent, Pangea. That continent eventually separated and drifted apart, forming the seven continents we have today
• proof of continental drift

  • Continent share - appear as though they would fit together like a jigsaw puzzle.
  • Rock formations - rock formations found on different continents that match up perfectly when continents are put back together
  • Fossils - fossils found on different continents which also match up nicely
• Convection currents 


  These occur in the mantle. These movements enable the crustal plates to move. When magma rises towards the crust, plates are pulled apart, and when magma sinks towards the core, the plates move together.
• the convention currents cause plates to move around 2-3 cm per year.
• 75% of the worlds volcanoes are located along the pacific ring of fire
• the mid Atlantic ridge is an underwater mountain range and is 77,000km long.
• 95% of volcanic activity occurs along the mid Atlantic ridge
• there are 3 types of plate boundaries

  1. divergent
  2. convergent (subduction and collision)
  3. transform
• volcano definition

  A volcano is a geological landform usually generated by the eruption through a vent. Magma and molten rock escape from the planets interior
• volcanic eruption

  1. Pressure builds up in the magma chamber
  2. magma forces its way up the vent
  3. magma erupts out of the volcano
  4. lava flows down the mountain side
  5. ash, bombs, gas and steam are released into the atmosphere
• Conditions of volcanoes

  1. Active - a volcano that could erupt at any time (must have been an eruption in the last 100 years).
  2. Dormant - a volcano that has not erupted for a long time, 100 years or more.
  3. a volcano that can’t erupt again.
• main types of volcanoes

  1. Composite volcanoes
  2. cinder cones
  3. sheild volcanoes
  4. lava domes
• composite volcanoes 


  Example - Mount st Helens, Washington USA

  steep sides and are made from lots of layers of volcanic rock. Explosive eruptions due to sticky lava And built up pressure.
• cinder cones 


  Example - sunset crater, Arizona USA

  circular or oval cone shaped. Made from. Small fragments of lava which are blown into the air through a single vent. when they cool down they form rock around the vent. grow quickly but are not very big not very dangerous