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Earth History

Earth History. In order to understand the environment today, we must first understand the Physical History of the Earth. What was the Earth’s surface Like 1 Billion Years ago?. Super Continent

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Earth History

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  1. Earth History

  2. In order to understand the environment today, we must first understand the Physical History of the Earth.

  3. What was the Earth’s surface Like 1 Billion Years ago? Super Continent Evidence from the oldest rocks on the planet suggest that there was a Super continent 1 billion years ago.

  4. Past Climate Cool time in Earth history. We are warming rapidly however. Cool time in Earth history. Sun was weaker Only 70% current output! Source: www.scotese.com

  5. How do we know? • Globorotalia mendarii used in ocean temperature studies • Left coiling= cold; Right coiling = warm

  6. What was the Atmosphere like? • No Oxygen • Methane • Carbon Dioxide • Nitrogen

  7. How do we know? • Certain minerals are easily oxidated in an oxygenated atmosphere • These minerals are commonly found in rocks >2.3 by • Pyrite and Uranite

  8. How do we know? • Banded Iron Formations are found exclusively in these older rocks • Iron was deposited in the ancient oceans • If the atmosphere contained oxygen, they would have oxidated-rusted

  9. Banded Iron Formations (BIF’s) • >1.9 BY • These BIF’s have been exposed to the modern atmosphere causing them to oxidate (rust)

  10. What else do we know? • After ~2 by oxygen was in the atmosphere

  11. How do we know? • Disappearance of BIF’s • Pyrite & Uranite not found commonly • Presence of “Red Beds”

  12. Red Beds • <2 BY • Iron in the rocks was oxidized due to higher concentrations of oxygen in the atmosphere

  13. Environmental degradation=loss of habitat! Methanogenic bacteria polluted their world Methanogenic bacteria fed on Hydrogen Carbon dioxide Acetate formed from anoxic decay of organic matter Gave off Methane as a by product What Happened?

  14. The Methane atmosphere that resulted warmed the planet Initially this was good for the methanogens Too much methane in the atmosphere creates reactions that produce smog This smog would have cooled the earth keeping temperatures livable Methane Atmosphere

  15. This warm planet allowed the rise of the photosynthesizers These took in carbon dioxide and produced oxygen as a by product Oxygen was poison to the methanogenic bacteria Forcing them into refuges What happened next

  16. Snowball Earth? • The demise of the methanogens may have caused the Pre Cambrian ice age.

  17. Cyanobacteria-one of the early oxygen producers

  18. Stromatolites Modern Stromatolite, Australia Fossil Stromatolites, end Archean

  19. Source: www.scotese.com

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