plate tectonics

• What are the compositional layers of the earth?

  • Crust
  • Mantle
  • Core
• Crust?

  • 2 types of crust, oceanic and continental crust
  • thinnest layer of the earths surface, below it is the mantle
• Characteristics of oceanic crust?

  • Thinner and denser than continental crust
  • Average of 7km thick
  • made of basalt, silicon and magnesium - darker colour due to this
• Characteristics of continental crust?

  • thicker and less dense than oceanic crust
  • on average 35km thick
  • composed of granite, feldspar - sial layer - silicon and aluminium
• What is the boundary between the crust and mantle called?

  The Moho
• Characteristics of the mantle ?

  • upper mantle - peridotite - 2900km thick
  • silica rocks mainly in a liquid state
  • rock sits ontop of the asthenosphere
  • denser than both types of crust
• Core characteristics?

  • Made of iron and nickel
  • temps reach 5000 degrees
  • semi-liquid -
  • its thought that when the liquid outer core spins as the earth rotates - creates earths magnetic field
• Lithosphere?

  • made up of crust as well as upper mantle
  • densities increase as you go further down
  • carried ontop of the athenosphere
  • Tectonic plates are found here
• Asthenosphere?

  • Moves slowly carrying the lithosphere on top - under high pressure
  • plastic type layer
• What is the difference between compositional layers and mechanical layers?

  compositional - rock properties

  mechanical - how layers move around and interact with each other
• What two layers is the mantle made up of?

  • asthenosphere and lithosphere
• Outer core?

  • semi-liquid, iron nickel alloy
  • earthquakes are a result of movement in this layer
  • high pressure
  • seismic waves are used to study the structure of this level
• Inner core?

  • Hotter than outer core, made of solid iron (due to highest pressure)
  • mechanically moves as one
  • heat caused by radioactive decay of elements such as uranium and potassium inside the earths core