Evolution of Earth Crust

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  • Big Bang Theory - “tiny ball” (Small volume of Indefinite mass with high density and high temperature) exploded violently → some energy was converted into matter → first three minutes from the Big Bang event, the first atom began to form → gave rise to atomic matter.
  • Age of Universe about 13.6 billion years ago.
  • Age of Earth about 4.6 billion years ago.
  • Age of Moon about 4.4 billion years ago - Mars sized asteroid hit the earth, the particular part/fragment rotate earth called natural satellite (Moon).
  • Tidally locked – Rotation of earth & moon are merely same.
Earth
  • Lithosphere – land/Rock & Feature.
  • Hydrosphere – Water/Ocean & Feature.
  • Atmosphere – Gas.
  • Biosphere – Combination of Lithosphere, Hydrosphere & Atmosphere.Lithosphere: Hot/Volatile → Cooling → Solidify → Contraction of earth
  • Hardest - Diamond, Densest - Ni, Pb (Lead)
3 Stages of Hydrosphere and Atmosphere
  • 1st Stage – loss & Replacement of Premodial Atmosphere.
  • 2nd Stage – Degassing.
  • 3rd Stage – Photosynthesis – Modification factor
Structure of earth interior
  • Heterogeneous in Composition
    • Soft minerals (Rock) Composition
  • Layered Structure
    • Basis of density variation
    • Most dense elements – Concentrated in the center.
    • Less dense elements – Found along the outermost surface.
  • Temperature & Pressure
    • Temperature directly proportional to Pressure at earth interior (Temp inversely proportional to Pressure on Open system)
    • After 100 km (temp increase 1°/ 32 m)
Earth interior – Crust, Mantle & Core
  • Crust (Density: 2.7 – 2.9 g/cm3)
    • Continental Crust (CC) – Silica + Aluminum – SIAL layer (Granite Rock)
    • Oceanic Crust (OC) – Silica + Magnesium – SIMA layer (Basaltic Rock)
  • Mantle (3 – 3.3 g/cm3) – Silica + Magnesium – SIMA layer – Rich in olivine.
  • Core (5 – 11 g/cm3) – Nickel + Iron – NIFE layer
    • Outer Core – Liquid State.
    • Inner Core – Solid State.
    • Thickness: CC > OC
    • Density: OC > CC
Discontinuity
  • Conrad – Separate upper & Lower crust.
  • Mohorinic/ moho/M – separate crust & Asthenoshpere.
  • Rapitti – Separate upper and lower Mandle.
  • Gutternberg/G – Separate mandle & Outer core.
  • Lahmann – Separate upper and lower core.
  • Mnemonics – CM RaGuL
  • Asthenosphere (80 – 200 km) [Weak zone / Zone of low velocity] – Source of Magma – Discontinuous layers of molted rock Between Crust & Mandle 

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