1 Chapter 2 Creation of Oceans

2 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 Big Bang 13 bya

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

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 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. Hydrogen and helium remain gaseous, but other materials can condense into solid “seeds” for building planets. Cold temperatures allow “seeds” to contain abundant ice in outer solar system. Terrestrial planets are built from metal and rock. Solid “seeds” collide and stick together. Larger ones attract others with their gravity, growing bigger still. 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 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 Condensation Theory

8 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. The result of density stratification: an inner and an inner and outer core, outer core, a mantle, a mantle, and the crust. and the crust. 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. Earth, Ocean and Atmosphere accumulated in layers sorted by density

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

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

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

12 Age and Time 1 billion = 1,000,000,000 or 10 9 Earth is 4.6 * 10 9 years old Oceans are 4.2 * 10 9 years old Oldest rocks date from 3.8 * 10 9 years ago First evidence of life dates from 3.6 * 10 9 years ago 1 million = 1,000,000 or 10 6 Ocean and atmosphere reach the state we know today 800 * 10 6 years ago