P1 - The Earth - Revision Mindmap

P1 - The Earth - Revision Mindmap

1. The Earth

   • when first formed the earth was completely molten
   • 4500 million years old as it is older than oldest rocks
   • studying rocks tells us more about earth
     • erosion - the earth's surface is made of rock layers, the layers are compacted sediment produced by weathering and erosion
     • craters - the moon's surface is covered with impact craters from meteors, earth also has been been eroded
     • mountain formation - if new mountains weren't being formed, earth's surface would have eroded down to sea level
     • folding - some rocks look as if they've been folded in half, requires huge force over time

2. Structure Of Earth

   • thin rocky crust
     • - thickness varies between 10km and 100 km
     • - oceanic crust lies beneath the oceans
     • - continental crust forms continents
   • the mantle
     • - extends almost halfway to the centre of the earth
     • has a rougher density than rock in crust
     • very hot but under pressure
   • the core
     • - accounts for over half of the earth's radius
     • -made of nickel and iron
     • - decay of radioactive elements inside the earth, keeping hot

3. Sea Floor Spreading

   • 1. convection currents in the mantle cause magma to rise
     • 2. the current moves the solid part of mantle and the tectonic plates
       • 3. when the plates are moving apart, magma reaches the suface and hardens, forming new areas of oceanic crust

4. plate tectonics

   • earth has a magnetic field, changes polarity every m years
     • combined with sea floor spreading produces rock stripes of alternating polarity
       • 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
       • can be used to see how quickly crust formed by width of stripes
   • when oceanic and continental plates collide the denser oceanic plate if forced under (subduction)
     • the oceanic plate melts and molten rock can rise to form volcanoes
     • mountain ranges form along plate boundaries as sed rock is forced up by pressure in collision
     • earthquakes
       • waves from earthquakes
         • 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
         • 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: /\/\/\/\/\/\/\/\/\/\
         • 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)
       • 1. Plates slide past eachother
         • 2. pressure builds up as plates push on each other
           • 3. eventually stored energy is released and waves from energy spread from epicenter
   • crucial in rock cycle
     • - old rock is destroyed through subduction
       • - plate collision can produce high temps causing rock to fold
         • - igneous rock is formed when magma reaches surface
           • - sed rock becomes metamorphic