Layers of Earth

• Layers of the Earth


  • Crust
  • Mantle
  • Core
• Crust


  • Thinnest layer of the Earth
  • Made up of large amounts of silicon and aluminum
  • Composed of plates on which the continents and oceans rest
  • Part of the lithosphere
  • Two types: Oceanic and Continental
• Types of Crust


  • Oceanic
  • Continental
• Oceanic Crust


  • Rock type: Basalt
  • Thickness: 3-8 km (thinner)
  • State: Solid
  • Age: 180 million years old or younger
  • Density: More dense
• Continental Crust


  • Rock type: Granite
  • Thickness: 5-70 km (thicker)
  • State: Solid
  • Age: 4 billion years old or older
  • Density: Less dense
• Lithosphere


  The crust and the upper layer of the mantle together make up a zone of rigid, brittle rock
• Lithospheric Plates


  1. The crust of the Earth is broken into many pieces called plates

  2. The plates "float" on the soft, semi-rigid asthenosphere
• Mantle


  • The largest layer of the Earth at 2900 km thick
  • The middle mantle is composed of very hot dense rock that flows like asphalt under a heavy weight
  • The movement of the middle mantle (asthenosphere) is the reason that the crustal plates of the Earth move
• Asthenosphere


  The semi-rigid part of the middle mantle that flows like hot asphalt under a heavy weight
• Convection Currents


  1. The middle mantle "flows" because of convection currents

  2. Convection currents are caused by the very hot material at the deepest part of the mantle rising, being less dense, then cooling, becoming more dense, and sinking again - repeating this cycle over and over
• Mantle Composition


  • Magnesium
  • Silicon
  • Oxygen
  • Iron
• Outer Core


  • Composition: Molten (liquid) metal that is about 4,700°C (8,500°F)
  • Thickness: 2,266 km (1,400 miles)
  • State of Matter: Composed of the melted metals nickel and iron (liquid)
  • Located about 1,800 miles beneath the crust
• Inner Core


  • Solid sphere made mostly of iron and has Nickel
  • It is believed to be as hot as 6,650°C (12,000°F)
  • Heat in the core generated by the radioactive decay of uranium and other elements
  • It is solid because of the pressure from the outer core, mantle, and crust compressing it
  • Thickness: 1271 km (800 miles)
• Temperature, Density and Pressure

  Increases as depth increases
• Scientists have drilled 7.6 miles into the Earth - only 0.2% of the distance to the Earth's core
• We know a lot about what's under the Earth's surface through indirect evidence, mostly from seismic waves caused by earthquakes
• Indirect evidence is sometimes the only option for scientists to develop a theory
• The Earth is divided into 3 main layers: Crust, Mantle, Core
• The main rock type of the 2 types of crust are: Oceanic - Basalt, Continental - Granite
• Oceanic crust is denser than continental crust
• The lithosphere is divided into tectonic plates
• The mantle has the convection currents which causes the plates to move
• The asthenosphere flows semi-liquid on which the plates move