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Extrusive igneous activity


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Extrusive igneous activity

  1. 1. Unit 4: Geographical Research Tectonic Activity and Hazards
  2. 2. What are these? Where are they? How did they get there?
  3. 7. Tectonic landscapes
  4. 9. Lesson 7: What are the landscape impact of extrusive igneous activity? <ul><li>Learning objectives </li></ul><ul><li>To outline the formation of extrusive igneous landforms such as lava plateaus and volcanoes </li></ul><ul><li>To investigate the different types of volcanoes and eruptions </li></ul>
  5. 10. Extrusive igneous activity <ul><li>Once extruded onto the surface of the earth, magma is referred to as lava which cools to form igneous rocks </li></ul><ul><li>The most significant landforms are lava plateaus and volcanoes </li></ul><ul><li>Their distribution is determined by the pattern of tectonic plates </li></ul><ul><li>Their impact on the landscape with vary according to the magnitude and scale of the events causing them and the types of material being extruded. </li></ul>
  6. 11. Lava Plateau
  7. 12. The Deccan Plateau
  8. 14. Volcanoes
  9. 15. Types of volcanoes
  10. 16. Types of volcano <ul><li>The type of volcano will be affected by: </li></ul><ul><ul><li>The type of lava erupted </li></ul></ul><ul><ul><li>The nature of the eruption </li></ul></ul><ul><ul><li>The type of plate margin </li></ul></ul>
  11. 17. Magma type & volcano morphology <ul><li>Basaltic – huge, low relief shield volcanoes plus small scoria cones and fissure vents . </li></ul><ul><li>Andesitic – steep sided strato-volcanoes ; layers of lava, ash and tephra. </li></ul><ul><li>Rhyolitic – central craters with lava plugs / domes , due to high viscosity of the lava. </li></ul>
  12. 18. Types of volcano <ul><li>Divergent margins </li></ul><ul><li>Fissure eruptions and shield volcanoes </li></ul><ul><li>Low, gently sloping sides, wide base </li></ul><ul><li>Basaltic lava, low viscosity, high temp so covers long distances before it cools and solidifies </li></ul><ul><li>Frequent, low magnitude eruptions </li></ul><ul><li>Also found at hotspots </li></ul><ul><li>Convergent margins </li></ul><ul><li>Cone shaped </li></ul><ul><li>Less frequent, more explosive eruptions </li></ul><ul><li>More silica and cooler, so more viscous </li></ul><ul><li>Flows slowly, cools quickly creating cone shape with narrow base and greater height </li></ul><ul><li>Often composite with alternating layers of ash and lava </li></ul>Watch video
  13. 19. Hawaii – shield volcanoes Oceanic hotspot location Volcanoes formed by tectonic plate moving north west over hotspot Gently sloping sides New volcano, 3000m tall and 2000m below sea
  14. 20. Soufriere Hills, Montserrat – Composite volcano
  15. 22. Wherever possible, try to use examples we have already used e.g. Kiluaea, Montserrat, Yellowstone Volcano type Diagram Key features Explanation Example Fissure Shield Dome Cinder Composite Caldera
  16. 23. Types of eruption <ul><li>Hawaiin – calm, non explosive </li></ul><ul><li>Vulcanian – explosive, short lived </li></ul><ul><li>What type of eruption is associated with your case studies? Why? What impact has this had? Add this to the explanation column on your table </li></ul>
  17. 24. Suggested resources <ul><li>Read pages 253-255 OUP text book </li></ul><ul><li>Pages 162-165 Byrne et al </li></ul><ul><li>Page 67 Frampton et al </li></ul><ul><li>Page 14-15 Nagle </li></ul><ul><li>Page 22-26 Waugh </li></ul><ul><li>National geographic “Forces of nature” – see types of volcano link on Moodle </li></ul><ul><li>Explore google earth locations </li></ul>
  18. 25. Next lesson …. <ul><li>Intrusive igneous landforms </li></ul>