tectonic movement

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  • tectonic movement
    • evidence for tectonics theory
      • the evidence of sea floor speading
        • mid Atlantic ridge discovered in 1948 during a survey also mountain ranges in the pacific
          • analysis in the 1960s created idea of sea floor spreading
        • 1960s further rock dating tchneches found the youngest of rocks closest to the ridge and the oldest further away further supoting this
        • paleomagnatism shown a pattern of corresponding strips of iron particles must have once been joined together
        • earth not getting bigger so plates must be destroyed elsewhere
      • continental drift wegneres idea
        • geological evidence
          • rocks in south west Africa and eastern brazil as well as eastern Canada and northern Scotland are similar type and formation.
        • biological evidence
          • fossils found in brazil and south east Africa (mesosauraus) must hav been layed down when the continents where once joined
        • climatological evidence
          • red sandstones and coal formed in different climatological conditions than where they currently are
        • continental fit
          • continents seemed to fit together the continents today formed through the splitting of Pangaea
        • was dismissed at the time as couldn't come up with process in which  would cause the movement of the continents
      • convection currents
        • the convection currents cause the magma to be more ductile in the athsenosphere
          • leads to the spreading forming rift valleys as magma moves more sideways it cools becoming more dense eventually sinking back into the lower mantle
            • oceanic plates cooled into the subduction zones forming trenches like Peru chili trench
      • todays ideas
        • what happens on the surface links to activity below
        • slab pull
          • greater density of the old lithosphere causes it to sink into the mantle at subduction zones sinking deep into the mantle with suction from the asthenosphere as well as gravity
    • structure links to plate movements
      • heat left over
        • radioactive decay and from creation of earth
        • leads to convection currents
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