Mineral Resources and Geology

The availability of earth’s resources was determined when the planet was formed

• Earth was formed 4.6 Billion Years ago

The Formation and Structure of Earth

• Earth was formed from dust in solar system

• Early earth = molten sphere

• As earth cooled, materials separated based on their masses

  • Heavy sank lower
    • Iron
  • Lighter floated up
    • Silica
  • Gaseous became part of atm

• B/c earth is divided up into layers based on mass, if its cut, it is possible to see layers.

  • The innermost layer = core
    • The innermost zone of Earth’s interior, composed mostly of iron and nickel. Includes a liquid outer and solid inner layer.
  • Above core is mantle
    • Layer of earth above the core, containing magma
      • Magma is molten rock
      • Magma circulates in convection cells like the atmosphere
  • Asthenosphere
    • Layer of earth located in outer part of mantel
    • Consists of semi molten rock
  • Lithosphere
    • Outermost layer of earth
    • Includes mantel and crust
    • Made up many large and small plates
      • Overlie the convection currents in asthenosphere
  • Crust
    • Chemically distinct outermost layer of lithosphere

  

Hot Spots

• Earth remains hot at the center
• High temps of earth’s outer core and mantle is due radioactive decay
• Heat causes plumes of magma to go upwards
  • Causes Hotspots
    • Place where molten material from earth’s crust reaches lithosphere

The theory of plate tectonics describes the movement of lithosphere

• Alfred Wegener published hypothesis that continents used to be joined to form a single mass called “Pangea”
  • He proved this by:
    • Finding identical rock formations on both sides of Atlantic ocean
    • Fossil evidence also suggests that there was a single landmass
• Theory of plate tectonics
  • Theory that lithosphere of earth is divided into plates, most of which are in constant motion
  • Tectonic cycle
    • Sum of the processes that build up and break down the lithosphere

Plate Movement

• Crust of ocean plates is dense and rich in iron
• Crust of continental plates contains more silicon dioxide (less dense)
• Both these plates float on denser material
  • Their movements are driven by convection cells in mantle
  • This convection current also drives the continuous creation and renewal of earths materials as well as destruction
  • Rising magma cooling and forming new crust is known as seafloor spreading