The early Earth

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The early Earth
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Goals

• To understand (1) the solar nebula theory for
  formation of the Earth, (2) how this led to
  Earths stratification, and (3) the methods weve
  used to understand Earths layering.

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Formation of Earth
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Age of Earth
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Early Earth
Hadean Eon and stratification
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Early Earth

• About 4,000-million years ago semi-permanent
  crust formed

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Earths layers

• Core
• Solid inner core
• Liquid outer core
• Mantle
• The upper and lower mantle
• The asthenosphere

Relative thickness of layers
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Earths layers

• The lithosphere
• Rigid upper-most mantle
• The crust thin rind of light elements floating
  on top of the Earth.

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Relative thickness of Earths layers
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So, how do we know what the mantle and core are
made of?
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1. Composition of meteorites
Iron-nickel alloy
Magnesium-silicate rocks
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2. Inclusions of the mantle in volcanic rocks
The mantle
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3. Fragments of uppermost mantle trapped in
mountain belts
The mantle in Oman
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4. Behavior of sound waves from earthquakes
large explosions
Structure of fetus modeled from sound velocities
Structure of mantle modeled from sound velocities