P1 - The Earth - Revision Mindmap

The Earth
1. when first formed the earth was completely molten
2. 4500 million years old as it is older than oldest rocks
3. studying rocks tells us more about earth
  1. erosion - the earth's surface is made of rock layers, the layers are compacted sediment produced by weathering and erosion
  2. craters - the moon's surface is covered with impact craters from meteors, earth also has been been eroded
  3. mountain formation - if new mountains weren't being formed, earth's surface would have eroded down to sea level
  4. folding - some rocks look as if they've been folded in half, requires huge force over time
Structure Of Earth
1. thin rocky crust
  1. - thickness varies between 10km and 100 km
  2. - oceanic crust lies beneath the oceans
  3. - continental crust forms continents
2. the mantle
  1. - extends almost halfway to the centre of the earth
  2. has a rougher density than rock in crust
  3. very hot but under pressure
3. the core
  1. - accounts for over half of the earth's radius
  2. -made of nickel and iron
  3. - decay of radioactive elements inside the earth, keeping hot
Sea Floor Spreading
1. 1. convection currents in the mantle cause magma to rise
  1. 2. the current moves the solid part of mantle and the tectonic plates
    1. 3. when the plates are moving apart, magma reaches the suface and hardens, forming new areas of oceanic crust
plate tectonics
1. earth has a magnetic field, changes polarity every m years
  1. combined with sea floor spreading produces rock stripes of alternating polarity
    1. 4. this pushes the existing floor outwards, and the the new crust is continuously forming at the crest of an oceanic rifge - leads to sea floors seperating a few cm each year
    2. can be used to see how quickly crust formed by width of stripes
2. when oceanic and continental plates collide the denser oceanic plate if forced under (subduction)
  1. the oceanic plate melts and molten rock can rise to form volcanoes
  2. mountain ranges form along plate boundaries as sed rock is forced up by pressure in collision
  3. earthquakes
    1. waves from earthquakes
      1. primary waves
        travels faster than s-waves
        can travels through both liquids and solids
        can travel through liquid region of outer core of earth
        longitudinal
        vibrates backwards and forwards
        moves backwards and forwards in the same plane as the direction of wave movement
        sound waves travel as longitudinal
      2. secondary waves
        can only travel through solid
        cannot travel through liquid region of outer core
        tranverse
        each particle vibrates up and down in normal position
        moves up and down at right angles to the direction of wave movement
        light and water ripples and electromagnetic waves travel in transverse
        example: /\/\/\/\/\/\/\/\/\/\
      3. wave features
        amplitude - the maximum disturbance caused by a wave, measured by the distance from a crest of the wave to the undistrubed
        wave length - the distance between corresponding points on two adjacent disturbances
        frequency - number of waves produced per second (hertz, hz)
    2. 1. Plates slide past eachother
      1. 2. pressure builds up as plates push on each other
        3. eventually stored energy is released and waves from energy spread from epicenter
3. crucial in rock cycle
  1. - old rock is destroyed through subduction
    1. - plate collision can produce high temps causing rock to fold
      1. - igneous rock is formed when magma reaches surface
        - sed rock becomes metamorphic

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P1 - The Earth - Revision Mindmap

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