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Formation of The Earth

Formation of The Earth. Composition of the Sun. The Most Unusual Element. Administratium (Ad) No protons: Atomic Number Zero One neutron 27 Assistant neutrons 137 Deputy assistant neutrons 332 Associate neutrons Detectable indirectly: slows down all reactions it participates in.

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Formation of The Earth

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  1. Formation of The Earth

  2. Composition of the Sun

  3. The Most Unusual Element Administratium (Ad) • No protons: Atomic Number Zero • One neutron • 27 Assistant neutrons • 137 Deputy assistant neutrons • 332 Associate neutrons • Detectable indirectly: slows down all reactions it participates in

  4. Composition of the Sun • Abundance of Light Elements • Rarity of Lithium, Beryllium, Boron • Preference for Even Numbers • Abundance peak at Iron, trailing off after

  5. How Elements Form in Stars • Sun: 4 H  He • He + particle  Mass 5 – Unstable • He + He  Mass 8 – Unstable • He + He + He  C • Add more He to make heavier elements • End of the line is iron for energy production • Atoms beyond Iron made in massive stars

  6. What are Planets Made of? • Same material as Sun • Minus the elements that remain mostly in gases • We find this pattern in a certain class of meteorites

  7. Chondrites

  8. Chondrite

  9. The Earth’s Crust looks Very Different

  10. Composition of the Crust

  11. Hot or Cold? • Up to 1940: Earth is hot inside, so must have formed hot • 1940-1970: Earth need not have formed hot • 1970- Earth did form hot after all

  12. Hot Early Earth? • Lord Kelvin, 1862: estimate age of Earth from cooling. • Earth’s heat is left over from its formation • Heat travels outward by conduction • Earth is not producing heat • Only one problem (actually three): Every one of Kelvin’s assumptions was wrong

  13. Three Images of Early Earth

  14. Chesley Bonestell’s Classic Image

  15. Nuclear Processes • Radioactivity (Becquerel, 1896) • Importance for Earth history: • Used for dating rocks • Explains sun’s energy output • Earth does produce heat

  16. Maybe Earth Formed Cool? • Planets formed by accretion of smaller bodies • Each impact produces heat • If rate is slow enough, heat can radiate away as fast as it is produced

  17. Earth Formed Hot After All • Apollo samples: Moon had “magma ocean” • Better understanding of impact physics • Role of mega-impacts • Formation of core

  18. Magma Ocean by Ron Hartmann

  19. Craters and Planetary History • Superposition • Crater Saturation • Crater Degradation

  20. Superposition

  21. Crater Saturation

  22. Crater Degradation

  23. Biggest and Oldest Crater on the Moon

  24. Impact History • Earliest records on Moon, Mars and Mercury: Intense Cratering • As planets grow, their gravity increases. Impacts get more violent • Debris from impacts buries hot rocks from earlier impacts • Heat builds up • Magma Ocean

  25. Basalt and Anorthosite

  26. How Do Planets Accrete? • Tiny objects can be held together by welding, electrical forces, chemical interactions • Big objects hang on to incoming material by gravity • Things the size of a car are the mystery right now

  27. Computer Studies • Start with as many orbiting objects as your computer can handle • Let them collide • Don’t get 8-10 nice, regular planets • Get 100’s of Moon and Mars-sized objects • These collide to make bigger planets • Violent beyond your wildest dreams

  28. How Did the Moon Form? • Co-Creation? • Fission? • Capture? • 1985: Bill Kaufmann, Jay Melosh and others: Mega-Impact

  29. Mega-Impacts: As Usual, Gary Larson Gets There First

  30. Computer Simulations by H.J. Melosh (University of Arizona)

  31. Formation of the Moon

  32. Formation of the Moon

  33. View from the early MoonEarth would have been as hot as the Sun for 10,000 Years

  34. Earth’s Atmospheres and Oceans • Primordial from accretion • Magma Ocean • Mega-Impacts (1000 km +) • Magma Ocean • Vaporized Rock (100’s years) • Steam • Smaller Impacts (100 km +) • Vaporized Rock (Years) • Steam (Boil off Oceans)

  35. Earth Finally Settles Down • Origin of Atmosphere and Oceans? • Outgassing? • Impacts of comets? • Early Atmosphere Probably Mostly CO2, and H2O

  36. Bonestell: The Earth Cools

  37. Bonestell: The Oceans Form

  38. Hartmann: The First Moonrise

  39. The Very Early Earth (Hadean) • Intense cratering on Moon (and presumably Earth) ends about 4 billion years ago. • Oldest earth material: 4 billion year old zircon from Australia. • Oldest rocks: 3.9 billion years, NW Canada. • Minnesota River Valley rocks: 3.1 billion years. • Can’t say much about processes • Liquid water from the git-go

  40. The Faint Early Sun • Sun 4 billion years ago was only 70% as bright as now. • Would make average temperature of earth -15 F (-26 C) • But earth has always had liquid water • Must have had denser atmosphere, greater greenhouse effect.

  41. The Archean • 3.0 – 2.5 billion years ago • About half of earth’s continental crust forms • Granite, deep-water sediments and volcanic rocks, deep crustal rocks • Were there mountains? • Did Plate Tectonics exist?

  42. Molasse, Switzerland

  43. Molasse and the High Alps

  44. Archean Granite

  45. Archean Pillow Lava

  46. Archean Iron Formation

  47. 3.1 Billion Year Old Gneiss

  48. Archean North America

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