P1 - The earth and the universe

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  • The Earth and The Universe
    • Solar system
      • There are eight planets that orbit the sun - Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus (a) Nest
        • An easier way to remember them is to say - My Very Energetic Mum Just Sat Under (a) Nest
      • The suns diameter is more than 100 times of the earths.
        • The solar system was formed over a long period from big clouds of dust and gas
          • A cloud started to get squeezed slightly and particles started to move closer together gravity took over and pulled things together until the whole cloud collapsed in on itself
    • Wegener's Theory of Continental Drift
      • Alfred Wegener hypothesised that Africa and South America have previously been one continent which had then split.
        • He found his evidence that there were matching layers in the rocks on the different continents and also similar fossils in both South America and South Africa/
        • Wegener's theory of 'continental drift' supposed that about 300 million years ago there had been just one "supercontinent" which he called Pangaea and according to him Pangaea broke into smaller chunks and now are slowly still drifting apart
    • The earths structure
      • The earth has a layered structure consisting of the solid inner core, the liquid outer core, the mantle, the lithosphere, the asthenosphere and crust.
        • There are two types of crusts - oceanic (under oceans) and continental (forming the land)
          • The earth is made from tectonic plates which float on the mantle.
            • Convection currents in the mantle caused by heating in the core and mantle cause the planes to drift.
              • Movements in the mantle cause the sea floor to move.
                • Most plates move at speeds of a few cm per year. Tectonic plates occasionally move suddenly in turn causing an earthquake
    • Seismic Waves
      • When there's an earthquake it produces wave motions which travel on the surface and inside the earth. There are two types - p-waves and S-waves
        • P-waves travel through solids and liquids, they also travel faster than S-waves and they are longitudinal.
        • S-waves only travel through solids hence them being S-WAVES they are also slower than P-waves and they are transverse

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