Unique Landforms Locate At Plate Margins Bv


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Unique Landforms Locate At Plate Margins Bv

  1. 1. Unique landforms locate at plate margins Objectives: To understand and be able to explain the location and formation of fold mountains ocean trenches, composite volcanoes Shield volcanoes.
  2. 2. Fold mountains What are fold mountains? Fold mountains are found in many parts of the world. They form along the plate boundaries where great movements have taken place and mountains formed from the folding of the earth's crust.
  3. 3. Describe the formation of fold mountains http://uk.youtube.com/watch?v=ngV66m00UvU&feature=related http://uk.youtube.com/watch?v=jVyBsUgD7Gk&NR=1
  4. 4. How are fold mountains formed? <ul><li>Fold mountains are formed when two plates move together (a destructive plate margin). This can be where two continental plates move towards each other or a continental and an oceanic plate. </li></ul><ul><li>The movement of the two plates forces sedimentary rocks upwards into a series of folds. </li></ul>
  5. 5. Formation <ul><li>Formed by compression as 2 plates collide </li></ul><ul><li>Compressional boundary such as Himalaya, Alps, Andes </li></ul><ul><li>Could be continental to continental </li></ul><ul><li>Continental to oceanic </li></ul><ul><li>Sedimentary rock is squeezed upwards </li></ul><ul><li>As rock is squashed at different rates layers of rock bend at different angles </li></ul><ul><li>Forms anticlines and synclines </li></ul>
  6. 6. Anticline
  7. 7. Syncline
  8. 8. <ul><li>Stage 1 </li></ul><ul><li>There were long periods of quiet between Earth movements during which sedimentary rocks formed in huge depressions called geosynclines. </li></ul><ul><li>Stage 2 </li></ul><ul><li>Rivers carried sediments and deposited them into the depressions. Over millions of years the sediments were compressed into sedimentary rocks. </li></ul><ul><li>Stage 3 </li></ul><ul><li>The rocks were then forced upwards into a series of folds by the movement of tectonic plates. When plates and the continents riding on them collide, the accumulated layers of rock crumple and fold like a tablecloth that is pushed across a table. </li></ul>
  9. 9. <ul><li>There are two types of fold mountains: </li></ul><ul><li>Young fold mountains (10 to 25 million years of age, e.g. Rockies and Himalayas) and </li></ul><ul><li>Old fold mountains (over 200 million years of age, e.g. Urals and Appalachians of the USA). </li></ul>
  10. 10. map
  11. 11. Ocean trenches http://visual.merriam-webster.com/images/earth/geology/ocean-trenches-ridges.jpg
  12. 13. Which is the deepest ocean trench? Mariana Trench has a maximum depth of about 11 km (6.8 miles)
  13. 14. At destructive plate boundaries the lava is viscous (thick like treacle) and it cannot flow very far from the volcano’s vent. This makes the volcano steep sided. At constructive plate boundaries the lava is runny and it can flow far away from the volcano’s vent. This makes the volcano gentle sided.
  14. 15. Composite volcano <ul><li>Composite volcanoes . </li></ul><ul><li>Examples: Mount Etna, Vesuvius, Mt St Helens </li></ul><ul><li>Characteristics </li></ul><ul><li>Steep sided symmetrical cone shape </li></ul><ul><li>High with narrow base </li></ul><ul><li>Alternate layers of acid lava and ash </li></ul><ul><li>Lava may cool inside the vent – the next eruption is very explosive to remove the plug </li></ul><ul><li>Subsidiary cones and vents form. </li></ul>
  15. 16. Examples: Mauna Loa, Kilauea - both Hawaiian islands Characteristics: Basic lava Gentle slopes Wide base Lava flows more easily, travels longer distances before cooling Usually non-violent