THE PRIMORDIAL EARTH

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THE PRIMORDIAL EARTH Hadean and Archean Eons
THE PRIMORDIAL EARTH Hadean and Archean
Eons Formation of the Solar System
The Solar Nebula Hypothesis
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THE PRIMORDIAL EARTH Hadean and Archean Eons
THE PRIMORDIAL EARTH Hadean and Archean
Eons Formation of the Solar System

• The Solar Nebula Hypothesis
• Planets revolve around sun in same direction
• Counter-clockwise

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THE PRIMORDIAL EARTH Hadean and Archean Eons
THE PRIMORDIAL EARTH Hadean and Archean
Eons Formation of the Solar System

• The Solar Nebula Hypothesis
• Planets lie roughly within sun's equatorial plane
  
• (plane of sun's rotation)

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THE PRIMORDIAL EARTH Hadean and Archean Eons
THE PRIMORDIAL EARTH Hadean and Archean
Eons Formation of the Solar System

• The Solar Nebula Hypothesis
• Solar system is disk-like
• in shape

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THE PRIMORDIAL EARTH Hadean and Archean Eons
THE PRIMORDIAL EARTH Hadean and Archean
Eons Formation of the Solar System

• The Solar Nebula Hypothesis
• 4. Planets rotate CCW on their axes, except for
  
• Venus - slowly CW
• Uranus - on its side
• Pluto - on its side

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THE PRIMORDIAL EARTH Hadean and Archean Eons
THE PRIMORDIAL EARTH Hadean and Archean
Eons Formation of the Solar System

• The Solar Nebula Hypothesis
• Moons go CCW around planets
• (with a few exceptions)

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THE PRIMORDIAL EARTH Hadean and Archean Eons
THE PRIMORDIAL EARTH Hadean and Archean
Eons Formation of the Solar System

• The Solar Nebula Hypothesis
• Distribution of planet densities and compositions
  is
• related to their distance from sun

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Inner, Terrestrial planets have high density
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Outer, Jovian planets have low density
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THE PRIMORDIAL EARTH Hadean and Archean Eons
THE PRIMORDIAL EARTH Hadean and Archean
Eons Formation of the Solar System
The Solar Nebula Hypothesis 7. Age - Moon and
meteorites 4.6 billion years
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THE PRIMORDIAL EARTH Hadean and Archean Eons
THE PRIMORDIAL EARTH Hadean and Archean
Eons Formation of the Solar System
The Solar Nebula Hypothesis Cold cloud of gas
and dust, contracts, flattens, and
rotates.Turbulence in cloud caused matter to
collect in certain locations. Accretion of
matter around central mass to form protoplanets
(cold accretion).
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THE PRIMORDIAL EARTH Hadean and Archean Eons
THE PRIMORDIAL EARTH Hadean and Archean
Eons Formation of the Solar System
The Solar Nebula Hypothesis 90 of mass to
center. Cloud condensed, shrank, and heated by
gravitational compression to form Sun. Solar
wind drove lighter elements outward causing
observed distribution of masses and densities.
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THE PRIMORDIAL EARTH Hadean and Archean
Eons Meteorites

• Meteorites are chunks of rock from the solar
  system
• that have impacted the Earth.
• They include fragments of the following objects
  that
• were broken off by collisions with other solar
  system
• objects
• Asteroids
• Moon rock
• Planets, such as Mars (Martian meteorites)

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THE PRIMORDIAL EARTH Hadean and Archean
Eons Meteorites

• Types of Meteorites
• Ordinary chondrites
• Most abundant type of meteorite
• About 4.6 billion years old,
• May contain chondrules (spherical bodies that
• solidified from molten droplets thrown into
  space
• during solar system impacts)

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THE PRIMORDIAL EARTH Hadean and Archean
Eons Meteorites

• Types of Meteorites
• Carbonaceous chondrites
• a. Contain about 5 organic compounds,
  including
• amino acids (building-blocks of proteins, DNA,
  and RNA)
• b. May have supplied basic building blocks of
  life to
• Earth
• c. Contain chondrules

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THE PRIMORDIAL EARTH Hadean and Archean
Eons Meteorites
Types of Meteorites 3. Achondrites - stony
meteorites without chondrules, resembling
basalt
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THE PRIMORDIAL EARTH Hadean and Archean
Eons Meteorites
Types of Meteorites 4. Iron meteorites       
Iron-nickel alloy a. Coarse-grained intergrown
crystal structure (Widmanstatten pattern) b.
About 5 of all meteorites
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THE PRIMORDIAL EARTH Hadean and Archean
Eons Meteorites
Types of Meteorites 5. Stony-irons Composed
partly of Fe, Ni and partly of silicate
minerals, including olivine (like Earth's
mantle). a. About 1 of all meteorites.
Least abundant type.
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Proterozoic Eon 0.54-2.5 byBP
Archean Eon 2.5-3.8 byBP
Hadean Eon 3.8-4.6 byBP
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THE PRIMORDIAL EARTH Hadean and Archean
Eons Accretion and Differentiation

• Origin of the Earth's Internal Layering
• Solar Nebular Theory or Cold Accretion Model
• (secondary differentiation)Earth was
  originally homogeneous.

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THE PRIMORDIAL EARTH Hadean and Archean
Eons Accretion and Differentiation
Origin of the Earth's Internal Layering Earth
formed by accretion of dust and larger
particles of metals and silicates.
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THE PRIMORDIAL EARTH Hadean and Archean
Eons Accretion and Differentiation
Origin of the Earth's Internal Layering Origin
of layering requires a process of
differentiation.
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THE PRIMORDIAL EARTH Hadean and Archean
Eons Accretion and Differentiation
Origin of the Earth's Internal Layering Different
iation is the result of heating and at least
partial melting.
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THE PRIMORDIAL EARTH Hadean and Archean
Eons Accretion and Differentiation
Origin of the Earth's Internal Layering Iron and
nickel sink to form core.
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THE PRIMORDIAL EARTH Hadean and Archean
Eons Accretion and Differentiation
Origin of the Earth's Internal Layering Less
dense material (silicon and oxygen mixed with
remaining iron and other metals) forms mantle
and lighter crust (primarily silicon and
oxygen).
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THE PRIMORDIAL EARTH Hadean and Archean
Eons Accretion and Differentiation
Origin of the Earth's Internal Layering Presence
of volatile gases on Earth today indicates that
complete melting did not occur.
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THE PRIMORDIAL EARTH Hadean and Archean
Eons Accretion and Differentiation
Source(s) of heat for melting? 1. Accretionary
heat from bombardment
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THE PRIMORDIAL EARTH Hadean and Archean Eons
Manicouagan Crater, Quebec 206-214 myBP
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THE PRIMORDIAL EARTH Hadean and Archean
Eons Accretion and Differentiation
Chicxulub (Mayan Tail of the Devil,
Mexico) Cretaceous-Tertiary (K-T) Boundary
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THE PRIMORDIAL EARTH Hadean and Archean Eons
Barringer Crater, AZ 49,000 yBP
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THE PRIMORDIAL EARTH Hadean and Archean Eons
Tunguska, Siberia 30 June, 1908
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THE PRIMORDIAL EARTH Hadean and Archean Eons
Samuel Taylor Coleridge The Rime of the Ancient
Mariner The upper air burst into life! And a
hundred fire-flags sheen, To and fro they were
hurried about! And to and fro, and in and out,
The wan stars danced between And the coming
wind did roar more loud, And the sails did sigh
like sedge And the rain poured down from one
black cloud The Moon was at its edge may have
been inspired by the Leonid meteor shower that he
witnessed in 1797
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THE PRIMORDIAL EARTH Hadean and Archean
Eons Accretion and Differentiation
Source(s) of heat for melting? 2. Heat from
gravitational compression
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THE PRIMORDIAL EARTH Hadean and Archean
Eons Accretion and Differentiation
Source(s) of heat for melting? 3. Radioactive
decay
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THE PRIMORDIAL EARTH Hadean and Archean
Eons Accretion and Differentiation
2. Hot Accretion Model - (primary
differentiation) Originally hot, heterogeneous
Earth     Zoning developed during cooling
           High-temperature crystallization 
elements (Fe, Ni) cool first and form Earth's
core      Low-temperature crystallization (Si,
O)       elements cool late to form Earth's
crust
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THE PRIMORDIAL EARTH Hadean and Archean Eons The
Hadean Crust
Dominated by iron and magnesium silicates.If
Earth experienced heating and partial melting,
it may have been covered by an extensive magma
ocean in the Hadean.Magma cooled to form rocks
called komatiites.Komatiites form at
temperatures greater than those at which basalt
forms (greater than 1100oC).Komatiites are
ultramafic rocks composed mainly of olivine and
pyroxene.Formed Earth's Hadean crust.
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THE PRIMORDIAL EARTH Hadean and Archean Eons The
Hadean Crust
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THE PRIMORDIAL EARTH Hadean and Archean
Eons Early Continental Crust
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THE PRIMORDIAL EARTH Hadean and Archean
Eons Modern Crust
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THE PRIMORDIAL EARTH Hadean and Archean
Eons Modern Crust
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THE PRIMORDIAL EARTH Hadean and Archean
Eons Evolution of the Atmosphere
First Atmosphere Earth's atmosphere has evolved
or changed over time. Earth's first, primitive
atmosphere lacked free oxygen. The primitive
atmosphere was derived from gases associated
with the comets and meteorites which formed the
Earth formed during accretion.
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THE PRIMORDIAL EARTH Hadean and Archean
Eons Evolution of the Atmosphere
First Atmosphere Composition - Probably H2, He
These gases are relatively rare on Earth
compared to other places in the universe and
were probably lost to space early in Earth's
history because Earth's gravity is not strong
enough to hold lighter gases
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THE PRIMORDIAL EARTH Hadean and Archean
Eons Evolution of the Atmosphere
First Atmosphere Earth still did not have a
differentiated core (solid inner/liquid outer
core) which creates Earth's magnetic field
(magnetosphere Van Allen Belt) which deflects
solar winds. Once the core differentiated the
heavier gases could be retained
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THE PRIMORDIAL EARTH Hadean and Archean
Eons Evolution of the Atmosphere
Second Atmosphere Produced by volcanic out
gassing.   Gases produced were probably similar
to those created by modern volcanoes H2O,
CO2, SO2, CO, S2, Cl2, N2, H2, and NH3
(ammonia) and CH4 (methane) No free O2 at this
time (not found in volcanic gases).
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