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THE PRIMORDIAL EARTH Hadean and Archean Eons

THE PRIMORDIAL EARTH Hadean and Archean Eons

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THE PRIMORDIAL EARTH Hadean and Archean Eons

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

  2. 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

  3. 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)

  4. 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

  5. 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

  6. 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)

  7. 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

  8. Inner, Terrestrial planets have high density

  9. Outer, Jovian planets have low density

  10. 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

  11. 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).

  12. 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.

  13. 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)

  14. 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)

  15. 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

  16. THE PRIMORDIAL EARTH Hadean and Archean Eons Meteorites Types of Meteorites 3. Achondrites - stony meteorites without chondrules, resembling basalt

  17. 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

  18. 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.

  19. Proterozoic Eon 0.54-2.5 byBP Archean Eon 2.5-3.8 byBP Hadean Eon 3.8-4.6 byBP

  20. 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.

  21. 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.

  22. 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.

  23. THE PRIMORDIAL EARTH Hadean and Archean Eons Accretion and Differentiation Origin of the Earth's Internal Layering Differentiation is the result of heating and at least partial melting.

  24. THE PRIMORDIAL EARTH Hadean and Archean Eons Accretion and Differentiation Origin of the Earth's Internal Layering Iron and nickel sink to form core.

  25. 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).

  26. 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.

  27. THE PRIMORDIAL EARTH Hadean and Archean Eons Accretion and Differentiation Source(s) of heat for melting? 1. Accretionary heat from bombardment

  28. THE PRIMORDIAL EARTH Hadean and Archean Eons Manicouagan Crater, Quebec 206-214 myBP

  29. THE PRIMORDIAL EARTH Hadean and Archean Eons Accretion and Differentiation Chicxulub (Mayan Tail of the Devil, Mexico) Cretaceous-Tertiary (K-T) Boundary

  30. THE PRIMORDIAL EARTH Hadean and Archean Eons Barringer Crater, AZ 49,000 yBP

  31. THE PRIMORDIAL EARTH Hadean and Archean Eons Tunguska, Siberia 30 June, 1908

  32. 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

  33. THE PRIMORDIAL EARTH Hadean and Archean Eons Accretion and Differentiation Source(s) of heat for melting? 2. Heat from gravitational compression

  34. THE PRIMORDIAL EARTH Hadean and Archean Eons Accretion and Differentiation Source(s) of heat for melting? 3. Radioactive decay

  35. 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

  36. 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.

  37. THE PRIMORDIAL EARTH Hadean and Archean Eons The Hadean Crust

  38. THE PRIMORDIAL EARTH Hadean and Archean Eons Early Continental Crust

  39. THE PRIMORDIAL EARTH Hadean and Archean Eons Modern Crust

  40. THE PRIMORDIAL EARTH Hadean and Archean Eons Modern Crust

  41. 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.

  42. 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