plate tectonics

• theory of plate tectonics came from -> Wegener's theory of continental drift
• joint continents = Pangea
• evidence for continental drift:

  • East coast of South America + west coast of Africa appeared to fit together like a jigsaw
  • rocks on coastlines were the same
  • the fossils the rocks contained was the same
• constructive plate boundary = plates move apart and magma rises -> earthquakes and volcanoes happen here
• process of constructive plate boundary's:

  1. magma convection current in mantle moves two plates apart
  2. magma rises to the top through gap
  3. magma cools to form new crust -> igneous rock basalt
  4. process repeat
  5. rock gets older as it gets further from the boundary
• this is a constructive plate boundary

  
• A destructive plate boundary = plates move together -> rock is destroyed -> volcanoes + earthquakes
• destructive plate boundary:

  1. if plates have different densities , the plate with higher density will sink into magma and melt (oceanic under continental)
  2. if plates have same density the crust is deformed
• this is a destructive plate boundary

  
• conservative boundary = plates slide past each other -> friction creates earthquakes only
• this is a conservative plate boundary