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The Earth in Context

The Earth in Context. GLY 2010 – Summer 2013 Lecture 2. Nebular Hypothesis. Painting of Nebula. An artistic impression of the nebula disk of gas and dust from which the planets in our solar system grew Image: Don Dixon. Collisions Between Planetesimals.

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The Earth in Context

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  1. The Earth in Context GLY 2010 – Summer 2013 Lecture 2

  2. Nebular Hypothesis

  3. Painting of Nebula • An artistic impression of the nebula disk of gas and dust from which the planets in our solar system grew • Image: Don Dixon

  4. Collisions Between Planetesimals • Don Dixon’s impression of collisions between planetesimals – a gravitationally driven mechanism for accretion of the planetary embryos that eventually built the Earth

  5. The Earth In Context

  6. Unique Features of the Earth • Liquid water oceans • Free oxygen in the atmosphere

  7. The Earth Is a Differentiated Planet - It Has Layers

  8. Early Atmosphere • Earth’s original atmosphere - Hydrogen and Helium • Light elements escape • Earth’s current atmosphere is secondary and evolved from other processes

  9. Outgassing • Early volcanism emitted gases into the atmosphere • Present day volcanic gas composition • Water Vapor ~ 50--60% • Carbon Dioxide ~ 24% • Sulfur ~ 13% • Nitrogen ~ 5.7% • Argon ~ 0.3%

  10. Earth’s Atmosphere Today • Nitrogen ~ 78% • Oxygen ~ 21% • Argon ~ 1% • Carbon dioxide ~ 396.78 parts per million (0.039%), measured at Mauna Loa, Hawaii in May, 2012 • Increased from 394.16 in May, 2011

  11. Problems • Not enough water to fill oceans • No oxygen in the atmosphere • Carbon dioxide levels much too high • Sulfur gas levels much too high

  12. Changes • Carbon dioxide and sulfur gases are absorbed by water and removed in rain • Resulting acid solutions weather the rocks • Carbon dioxide becomes limestone • Sulfur gases become sulfide minerals

  13. Oxygen? • The early earth had no oxygen • Life appeared on earth at least 3.5 billion years ago – recent claims of 3.9 billion, and perhaps even 4.4 billion • Cyanobacteria appeared around 2.5 billion years ago

  14. Catastrophism • Early theory – series of catastrophes • Earthquakes • Volcanic eruptions • Floods • Age of earth assumed to be a few thousand years Abraham Gottlob Werner, 1750-1817

  15. James Hutton, 1726-1797 • Originator “The present is the key to the past” • Originator of the concept of “deep time”

  16. Uniformitarianism

  17. Geologic Time

  18. Paleozoic Era • Trilobite fossil, early Paleozoic era

  19. Mesozoic Era • Dinosaurs were the dominant life forms

  20. Cenozoic Era • Kangaroos are marsupials, a type of mammal

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