LAYERS OF THE EARTH

• Layers of the Earth:

  • Rheological Differentiation
  • Chemical Differentiation
• Layers based on Rheology:

  • Lithosphere
  • Asthenosphere
  • Mesosphere
  • Outer Core
  • Inner Core
• Rheological Differentiation


  • Liquid state of rocks under pressure and temperature
  • Dividing the earth into layers
  • Lithosphere
  • Asthenosphere
  • Mesosphere
  • Outer Core
  • Inner Core
• Lithosphere 


  The topmost layer where tectonic plates lie. It is also the crust and the upper layer of the mantle. A rigid layer that can break under stress.
• Asthenosphere 


  Layer below the lithosphere where magma lies and can deform and reshape under heat. It is about 180 km thick.
• The movements of Asthenosphere can lead to formations of:


  • Mountains
  • Volcanoes
  • Islands
  • Trenches
  • Mid-Ocean ridges
• Layers based on Chemical Variations:


  • Crust
  • Mantle
  • Outer Core
  • Inner Core
• Crust


  The topmost layer where all life exists. It is broken into major and minor blocks of rocks referred to as tectonic plates.
• Types of Crusts

  1. Continental crust
  2. Oceanic Crust
• Crust


  The crust's thickness is around 5-70 km thick and its composition is Alumina (Al2O3) and Silica (SiO2), its state of matter is solid and its temperature ranges from 200-400 degrees Celsius.
• Continental Crust


  The crust that makes up the continents. It is about 40-70 km thick and is made up of less dense granitic rocks.
• Oceanic Crust


  Has an average thickness of 5 km and is made up of more dense basaltic rocks.
• Mantle 


  The largest layer that makes up 84% of the Earth's volume. It is a semi-solid rocky hot layer which acts like a plastic. It is deformable at geologic timescales under immense pressure and temperature.
• Convection Currents 


  Deformation in the mantle causes a convection-like process with large-scale upwelling and dwelling zones. It is also the Heat Energy from magma circulates in the process.
• Convection Currents :


  1. Heat energy from magma circulates
  2. Heat energy from the core heats up magma
  3. Less dense magma floats
  4. Magma cools off and sinks
• Mantle


  Its thickness is around 2,890 km with a composition of silicate rocks. Its state of matter is semi-solid and its temperature ranges from 500-4000 degrees Celsius.
• Outer Core


  The only layer that is liquid and is made up of molten nickel and molten iron. It is located below the mantle.
• Outer Core


  Its thickness is around 2270 km with a composition of molten nickel and molten iron. Its state of matter is liquid and its temperature ranges from 3700 - 4300 degrees Celsius
• Inner Core


  It is located below the outer core and it is the solid center of the earth that is mostly composed of solid iron. It is a plasma that is acting like a solid due to immense pressure.
• Inner Core


  Its thickness: 1220 km with a composition of solid iron. State of matter: solid with a temperature that ranges about 6000 degrees Celsius
• Rotations:

  • The earth rotates eastward (west to east)
  • The core rotates westward (east to west)
• DISCONTINUITIES

  • Conrad Discontinuity
  • Moho / Mohorovicic Discontinuity
  • Repetti Discontinuity
  • Gutenberg Discontinuity
  • Lehmann Discontinuity
• Conrad Discontinuity 


  Boundary between the upper and lower crust
• Moho / Mohorovicic Discontinuity 


  Boundary between the lower crust and upper mantle
• Repetti Discontinuity 


  Boundary between the upper mantle and lower mantle
• Gutenberg Discontinuity 


  Boundary between the lower mantle and outer core
• Lehmann Discontinuity 


  Boundary between the outer core and inner core
• Seismic Waves


  Waves of energy caused by the breaking of rock in the earth or an explosion.
• To determine the composition of the earth scientists utilize seismic waves
• Types of Seismic Instruments:

  • Seismographs
  • Seismometers
  • Seismograms
• Seismographs 


  Machines that record seismic waves from earthquake.
• Seismometers


  Digital devices that record seismic waves.
• Seismograms


  Products of seismographs and seismometers
• Types of Waves

  • Compressional Waves
  • Transverse Waves
• Compressional Waves


  Waves that displace materials parallel to the direction of the wave.
• Transverse Waves


  Waves that displace materials perpendicular to the direction of the wave.
• Types of Seismic Waves

  • Body Waves
  • Surface Waves
• Body Waves


  travel through the interior of the Earth. They move in all directions from the point of origin (focus) of an earthquake.
• Surface Waves 


  travels along the Earth's surface. They typically cause more damage than body waves due to their larger amplitude and the fact that they occur closer to the surface.
• Types of Body Waves

  • P-waves (Primary Waves)
  • S-waves (Secondary Waves)