NEBULAR HYPOTHESIS

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a. Supernova and formation of primordial dust
cloud.
NEBULAR HYPOTHESIS
b. Condensation of primordial dust. Forms
disk-shaped nubular cloud rotating
counter-clockwise.
c. Proto sun and planets begin to form.
d. Accretion of planetesimals and differentiation
of planets and moons.
e. Existing solar system takes shape.
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• Evidence to support the nebular hypotheses
• Planets and moons revolve in a counter-clockwise
  direction (not random).
• Almost all planets and moons rotate on their axis
  in a counter-clockwise direction.
• Planetary orbits are aligned along the suns
  equatorial plane (not randomly organized).

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Terrestrial Planets Close to the sun Small rocky.

Jovian Planets Far from the sun Large, gaseous
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• Differntiated Earth
• 1. Iron-Nickel Core
• (outer core liquid)
• (inner core solid)
• Fe-Mg Silicate Mantle
• Fe-Mg-Al Silicate Crust
• (ocean and continental)
• Oceans
• Atmosphere
• Compositional zonation
• based on density.

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• How does the earth become compositionally zoned?
• Accretion of planetesimals.
• Initial heating due kinetic energy of colliding
  planetesimals and compressional heating.
• Additional heating from radiocactive decay.
• Iron catastrophe (melting temperarure of iron
  reached and dense iron-nickel sink to core and
  lighter materials are displaced outwards
  (including silicate rock of mantle and crust,
  ocean waters and atmospheric gases.
• Earth become compositionally zoned based on
  density (Densest iron-nickel in core-least dense
  materials comprise the atmosphere).
• Convective overturn in asthenosphere, mantle and
  outer core still occur today.

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Cratering on the moon is indicative of early
accretion process.
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Iron catastrophe and differentiation of the
earth. Think about transfer of heat when the
earth is solid versus when it becomes completely
molten following the iron catastrophe.
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Degassing of the earth occurred following iron
catastrophe and differentiation. Oceans and
atmosphere form during the differentiation
process.
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Emissions during degassing. Note that
oxygenation of the atmosphere occurs following
evolution of plants that use photosynthesis in
their life processes.
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• Differntiated Earth
• 1. Iron-Nickel Core
• (outer core liquid)
• (inner core solid)
• Fe-Mg Silicate Mantle
• Fe-Mg-Al Silicate Crust
• (ocean and continental)
• Oceans
• Atmosphere
• Compositional zonation
• based on density.

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Metallic meteorites Iron-Nickel
Chondritic meteorites Fe-Mg silicate (rocky)
Evidence of compositional materials Meteorite
composition.
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Seismic wave evidence. Compression Waves
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Seismic wave evidence Shear waves.
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Seismic waves refract because of velocity changes
related to density changes within the earth.
Seismic wave accelerate with increasing density.
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P-wave shadow zones. Note two shadow zones.
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S-wave shadow zone. Note S-waves absorbed by the
liquid outer core.
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