Plate boundaries

  • Created by: Izzie06
  • Created on: 26-05-18 09:12
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  • Plate boundaries
    • Divergent (constructive)
      • Two plates are moving away from each other and crust is forming from magma that rises to the surface between the two plates
      • Oceanic-oceanic
        • Mid ocean ridge
          • Two oceanic plates move away from each other, allowing magma to rise up. The magma reaches the bottom of the ocean, turns to lava and cools, forming new work. This continues as sea floor spreading occurs, adding new material
            • In Iceland, Surtsey has developed on the surface of the ridge
    • Conservative
      • Plates slide past/next to each other in different speeds of directions
        • San Andreas Fault- Pacific plate and North American plate both moving NW at different speeds- Pacific is faster at 5-9cm a year, North American is 2-1cm. Jerky and sporadic movement, frictional forces lock blocks together for long periods of time but when friction is overcome, the plates slip suddenly and cause shallow focus earthquakes. If current rates continue, LA will be next to SF in 20 million years
  • Convergent (destructive)
    • When 2 lithospheric plates are moving towards each other
    • Plate boundaries
      • Divergent (constructive)
        • Two plates are moving away from each other and crust is forming from magma that rises to the surface between the two plates
        • Oceanic-oceanic
          • Mid ocean ridge
            • Two oceanic plates move away from each other, allowing magma to rise up. The magma reaches the bottom of the ocean, turns to lava and cools, forming new work. This continues as sea floor spreading occurs, adding new material
              • In Iceland, Surtsey has developed on the surface of the ridge
      • Conservative
        • Plates slide past/next to each other in different speeds of directions
          • San Andreas Fault- Pacific plate and North American plate both moving NW at different speeds- Pacific is faster at 5-9cm a year, North American is 2-1cm. Jerky and sporadic movement, frictional forces lock blocks together for long periods of time but when friction is overcome, the plates slip suddenly and cause shallow focus earthquakes. If current rates continue, LA will be next to SF in 20 million years
    • Oceanic-oceanic
      • Island arcs
        • Same as volcanoes on land. Subducted oceanic plate melts and rises to reach the surface, building up until the volcano breaks the surface of the water, creating a chain of islands
          • Aleutian Islands in Pacific Ring of Fire
      • Ocean trenches
        • More dense ocanic plate subducts under less dense plate (can be oceanic or continental), pulls front edge of the less dense plate down, creating a trench.  Seaward side has gentle 5 degree slope as plate bends when it plunges down
          • Mariana's Trench- 11000m below sea level, where the Pacific plate subducted beneath the Philippine plate
    • Continental- continental (Collison plate boundary)
      • Fold mountains
        • Two continental plates collide. Continental is not dense enough to subduct so the continental crust folds upward as it has nowhere else to go, creating a chain of folded mountains
          • Himalayas formed due to collision of Indian and Eursian plate 50 million years ago- India used to be off Australian coast but began to drift towards  Asia. Tethys ocean floor began to subduct but not all of it as most were scraped off to build an accretionary wedge, which formed the Himalayas. Still rising as India continues to move North, gives off earthquakes- However is being weathered at same rate
  • Oceanic-oceanic
    • Island arcs
      • Same as volcanoes on land. Subducted oceanic plate melts and rises to reach the surface, building up until the volcano breaks the surface of the water, creating a chain of islands
        • Aleutian Islands in Pacific Ring of Fire
    • Ocean trenches
      • More dense ocanic plate subducts under less dense plate (can be oceanic or continental), pulls front edge of the less dense plate down, creating a trench.  Seaward side has gentle 5 degree slope as plate bends when it plunges down
        • Mariana's Trench- 11000m below sea level, where the Pacific plate subducted beneath the Philippine plate

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