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Chapter 2

Chapter 2 . Creation of Oceans. Big Bang 13 bya. Supporting Evidence for the Big Bang Edwin Hubble discovered spreading of galaxies. Cosmic background radiation (the glow left over from the explosion itself) discovered in 1964 . . Origin of a Galaxy. Andromeda Galaxy.

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Chapter 2

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  1. Chapter 2 Creation of Oceans

  2. Big Bang 13 bya • Supporting Evidence for the Big Bang • Edwin Hubble discovered spreading of galaxies. • Cosmic background radiation (the glow left over from the explosion itself) discovered in 1964.

  3. Origin of a Galaxy Andromeda Galaxy • Huge rotating aggregation of stars, dust, gas and other debris held together by gravity.

  4. Origin of the Solar System • Rotating cloud of gas from which sun and planets formed • Initiated by “supernova” = exploding star

  5. Nuclear Fusion: The joining of atoms under tremendous temperatures and pressures to create atoms of a heavier element. In the Sun, four hydrogen atoms are fused to create each helium atom. Two of the hydrogen's protons become neutrons in the process

  6. Moderate Size Stars (Our Sun): C & O Large Stars (more, H & He): Fe Supernova: Heavier Elements Formed

  7. Condensation Theory A nebula (a large, diffuse gas cloud of gas and dust) contracts under gravity. As it contracts, the nebula heats, flattens, and spins faster, becoming a spinning disk of dust and gas. Star will be born in center. Planets will form in disk. Warm temperatures allow only metal/rock “seeds” to condense in the inner solar system. Cold temperatures allow “seeds” to contain abundant ice in outer solar system. Hydrogen and helium remain gaseous, but other materials can condense into solid “seeds” for building planets. The seeds of gas giant planets grow large enough to attract hydrogen and helium gas, making them into giant, mostly gaseous planets; moons form in disks of dust and gas that surround the planets. Terrestrial planets are built from metal and rock. Solid “seeds” collide and stick together. Larger ones attract others with their gravity, growing bigger still. Terrestrial planets remain in inner solar system. Gas giant planets remain in outer solar system. “Leftovers” from the formation process become asteroids (metal/rock) and comets (mostly ice). Not to scale

  8. Earth, Ocean and Atmosphere accumulated in layers sorted by density The planet grew by the aggregation of particles. Meteors and asteroids bombarded the surface, heating the new planet and adding to its growing mass. At the time, Earth was composed of a homogeneous mixture of materials. Earth lost volume because of gravitational compression. High temperatures in the interior turned the inner Earth into a semisolid mass; dense iron (red drops) fell toward the center to form the core, while less dense silicates move outward. Friction generated by this movement heated Earth even more. The result of density stratification: an inner and outer core, a mantle, and the crust.

  9. Sources of Water • Mantle rocks • Evidence from meteorites • Release through volcanic activity • Outer space • Evidence from Dynamics Explorer

  10. 100 Methane, ammonia 75 Atmosphere unknown Concentration of Atmospheric Gases (%) Nitrogen 50 Water 25 Oxygen Carbon dioxide 0 1 3 4.5 4 2 Time (billions of years ago) Fig. 2-11, p. 49 The evolution of our atmosphere initial rise of O2 2.7 b. y. ago – but conclusive evidence is from 2.3 b. y. ago Early atmosphere quite different from today’s

  11. Billions of years ago Billions of years ago Big bang 13 Earth forms 4.6 Millions of years ago Ocean forms 4.2 11 First galaxies form First animals arise 3.8 800 Oldest dated rocks 3.6 First evidence of life Past Solar nebula begins to form Millions of years ago 66 First fishes appear 510 5.5 End of dinosaurs Oxygen revolution begins 2 Earth forms 4.6 50 First marine mammals Pangaea breaks apart 210 Ocean and atmosphere reach steady state (as today) 0.8 End of dinosaurs Humans appear 0 3 66 Today Today Today Today Today Sun's output too low for liquid-water ocean Future 3.5 The sun swells, planets destroyed 5 Billions of years in the future Fig. 2-15, p. 51

  12. Age and Time 1 billion = 1,000,000,000 or 109 Earth is 4.6 * 109 years old Oceans are 4.2 * 109 years old Oldest rocks date from 3.8 * 109 years ago First evidence of life dates from 3.6 * 109 years ago 1 million = 1,000,000 or 106 Ocean and atmosphere reach the state we know today 800 * 106 years ago

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