Inside Our Earth

• Interior of the Earth

  • Like an onion, made of several concentric layers
  • Crust
    • Uppermost layer
    • Thinnest layer
    • Continental Crust
      • Thickness: ~35 km
      • Main minerals: Silica and Alumina (Sial)
    • Oceanic Crust
      • Thickness: ~5 km
      • Main minerals: Silica and Magnesium (Sima)
  • Mantle
    • Just beneath the crust
    • Extends up to a depth of 2900 km
  • Core
    • Innermost layer
    • Radius: ~3500 km
    • Main minerals: Nickel and Iron (Nife)
    • Outer Core: Liquid state
    • Inner Core: Solid state

• Rocks and Minerals

  • Rock Definition: Any natural mass of mineral matter that makes up the earth's crust
  • Igneous Rocks
    • Formed by cooling of molten magma
    • Also called Primary Rocks
    • Intrusive Rocks: Cools deep inside the earth (e.g., Granite)
    • Extrusive Rocks: Cools on the earth's surface (e.g., Basalt)
  • Sedimentary Rocks
    • Formed by accumulation and compression of sediments
    • Often contain fossils of plants and animals
    • Example: Sandstone
  • Metamorphic Rocks
    • Formed under great heat and pressure
    • Example: Limestone changes into Marble

• Rock Cycle

  • Continuous transformation of one rock type to another
  • Magma $\rightarrow$ Igneous Rocks $\rightarrow$ Sediments $\rightarrow$ Sedimentary Rocks $\rightarrow$ Metamorphic Rocks $\rightarrow$ Melting into Magma

• Minerals

  • Naturally occurring substances
  • Physical properties: Hardness, color, density
  • Chemical properties: Chemical composition
  • Examples: Iron, Coal, Aluminium, Gold
  • Importance: Used as fuels and in industries