Post on 19-Dec-2015
THE PRIMORDIAL EARTHHadean and Archean Eons
THE PRIMORDIAL EARTHHadean and Archean EonsFormation of the Solar System
The Solar Nebula Hypothesis
THE PRIMORDIAL EARTHHadean and Archean Eons
THE PRIMORDIAL EARTHHadean and Archean EonsFormation of the Solar System
The Solar Nebula Hypothesis
1. Planets revolve around sun in same directionCounter-clockwise
THE PRIMORDIAL EARTHHadean and Archean Eons
THE PRIMORDIAL EARTHHadean and Archean EonsFormation of the Solar System
The Solar Nebula Hypothesis
2. Planets lie roughly within sun's equatorial plane (plane of sun's rotation)
THE PRIMORDIAL EARTHHadean and Archean Eons
THE PRIMORDIAL EARTHHadean and Archean EonsFormation of the Solar System
The Solar Nebula Hypothesis
3. Solar system is disk-like in shape
THE PRIMORDIAL EARTHHadean and Archean Eons
THE PRIMORDIAL EARTHHadean and Archean EonsFormation of the Solar System
The Solar Nebula Hypothesis
4. Planets rotate CCW on their axes, except for: a. Venus - slowly CW b. Uranus - on its side c. Pluto - on its side
THE PRIMORDIAL EARTHHadean and Archean Eons
THE PRIMORDIAL EARTHHadean and Archean EonsFormation of the Solar System
The Solar Nebula Hypothesis
5. Moons go CCW around planets (with a few exceptions)
THE PRIMORDIAL EARTHHadean and Archean Eons
THE PRIMORDIAL EARTHHadean and Archean EonsFormation of the Solar System
The Solar Nebula Hypothesis
6. Distribution of planet densities and compositions is related to their distance from sun
Inner, Terrestrial planets have high density
Outer, Jovian planets have low density
THE PRIMORDIAL EARTHHadean and Archean Eons
THE PRIMORDIAL EARTHHadean and Archean EonsFormation of the Solar System
The Solar Nebula Hypothesis
7. Age - Moon and meteorites 4.6 billion years
THE PRIMORDIAL EARTHHadean and Archean Eons
THE PRIMORDIAL EARTHHadean and Archean EonsFormation 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).
THE PRIMORDIAL EARTHHadean and Archean Eons
THE PRIMORDIAL EARTHHadean and Archean EonsFormation 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.
THE PRIMORDIAL EARTHHadean and Archean EonsMeteorites
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:
1. Asteroids 2. Moon rock 3. Planets, such as Mars (Martian meteorites)
THE PRIMORDIAL EARTHHadean and Archean EonsMeteorites
Types of Meteorites
1. Ordinary chondrites a. Most abundant type of meteorite b. About 4.6 billion years old, c. May contain chondrules (spherical bodies that
solidified from molten droplets thrown into space during solar system impacts)
THE PRIMORDIAL EARTHHadean and Archean EonsMeteorites
Types of Meteorites
2. 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
THE PRIMORDIAL EARTHHadean and Archean EonsMeteorites
Types of Meteorites
3. Achondrites - stony meteorites without chondrules, resembling basalt
THE PRIMORDIAL EARTHHadean and Archean EonsMeteorites
Types of Meteorites
4. Iron meteorites Iron-nickel alloy
a. Coarse-grained intergrown crystal structure (Widmanstatten pattern)
b. About 5% of all meteorites
THE PRIMORDIAL EARTHHadean and Archean EonsMeteorites
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.
Hadean Eon 3.8-4.6 byBP
Archean Eon 2.5-3.8 byBP
Proterozoic Eon 0.54-2.5 byBP
THE PRIMORDIAL EARTHHadean and Archean EonsAccretion and DifferentiationOrigin of the Earth's Internal Layering
1. Solar Nebular Theory or Cold Accretion Model(secondary differentiation):
Earth was originally homogeneous.
THE PRIMORDIAL EARTHHadean and Archean EonsAccretion and Differentiation
Origin of the Earth's Internal Layering
Earth formed by accretion of dust and larger particles of metals and silicates.
THE PRIMORDIAL EARTHHadean and Archean EonsAccretion and Differentiation
Origin of the Earth's Internal Layering
Origin of layering requires a process of differentiation.
THE PRIMORDIAL EARTHHadean and Archean EonsAccretion and Differentiation
Origin of the Earth's Internal Layering
Differentiation is the result of heating and at least partial melting.
THE PRIMORDIAL EARTHHadean and Archean EonsAccretion and Differentiation
Origin of the Earth's Internal Layering
Iron and nickel sink to form core.
THE PRIMORDIAL EARTHHadean and Archean EonsAccretion 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).
THE PRIMORDIAL EARTHHadean and Archean EonsAccretion and Differentiation
Origin of the Earth's Internal Layering
Presence of volatile gases on Earth today indicatesthat complete melting did not occur.
THE PRIMORDIAL EARTHHadean and Archean EonsAccretion and Differentiation
Source(s) of heat for melting?
1. Accretionary heat from bombardment
THE PRIMORDIAL EARTHHadean and Archean EonsManicouagan Crater, Quebec 206-214 myBP
THE PRIMORDIAL EARTHHadean and Archean EonsAccretion and Differentiation
Chicxulub (Mayan Tail of the Devil, Mexico)Cretaceous-Tertiary (K-T) Boundary
THE PRIMORDIAL EARTHHadean and Archean EonsBarringer Crater, AZ 49,000 yBP
Tunguska, Siberia 30 June, 1908
THE PRIMORDIAL EARTHHadean and Archean Eons
Samuel Taylor ColeridgeThe 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
THE PRIMORDIAL EARTHHadean and Archean Eons
THE PRIMORDIAL EARTHHadean and Archean EonsAccretion and Differentiation
Source(s) of heat for melting?
2. Heat from gravitational compression
THE PRIMORDIAL EARTHHadean and Archean EonsAccretion and Differentiation
Source(s) of heat for melting?
3. Radioactive decay
THE PRIMORDIAL EARTHHadean and Archean EonsAccretion 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
THE PRIMORDIAL EARTHHadean and Archean EonsThe 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.
THE PRIMORDIAL EARTHHadean and Archean EonsThe Hadean Crust
THE PRIMORDIAL EARTHHadean and Archean EonsEarly Continental Crust
THE PRIMORDIAL EARTHHadean and Archean EonsModern Crust
THE PRIMORDIAL EARTHHadean and Archean EonsModern Crust
THE PRIMORDIAL EARTHHadean and Archean EonsEvolution 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.
THE PRIMORDIAL EARTHHadean and Archean EonsEvolution 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
THE PRIMORDIAL EARTHHadean and Archean EonsEvolution 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
Second AtmosphereProduced 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).
THE PRIMORDIAL EARTHHadean and Archean EonsEvolution of the Atmosphere