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The Geologic Time Scale

The Geologic Time Scale. If we condensed the Geologic Time Scale to One Minute when would humans appear?. Origin of Life in One Minute. Geologic time is divided into: EONS ERAS PERIODS EPOCHS. WHY DO WE HAVE DIFFERENT NAMES FOR EONS AND ERAS?.

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The Geologic Time Scale

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  1. The Geologic Time Scale

  2. If we condensed the Geologic Time Scale to One Minute when would humans appear? • Origin of Life in One Minute

  3. Geologic time is divided into: EONS ERAS PERIODS EPOCHS

  4. WHY DO WE HAVE DIFFERENT NAMES FOR EONS AND ERAS? Image courtesy of the UC Museum of Paleontology Understanding Evolution: http://evolution.berkeley.edu."

  5. Precambrian Time • 88% of the Geologic Time Scale • 4.6 bya – 540 mya • Almost 4 Billion Years!

  6. The Precambrian is like a book with missing pages. 1. Precambrian rocks are buried under newer layers of rocks (Law of Superposition) • There are some areas like the Canadian shield where these rocks are exposed and can be studied No fossils to identify rocks from this time b/c they have been metamorphosed, eroded, or hidden by overlying rock by now.

  7. What DO we know about the Precambrian 1. When Earth first formed it was hot and made of lava…it took time for the lava on the surface to cool and harden into rock 2. The atmosphere was made of water vapor, carbon dioxide (CO2), and Nitrogen (N) Earth’s Atmosphere Today:

  8. What DO we know about the Precambrian 3. Torrential rains helped cool the Earth and the low areas filled with water ….this is how we got our oceans 4. The first signs of life evolved in the oceans since there was oxygen in water, but none in the air Hydrogen

  9. One of the first organisms on Earth to evolve (in the oceans) were a type of prokaryote called cyanobacteria

  10. Precambrian Fossils • During the Precambrian, there are not many fossils because not much evolution yet • Most common fossil from cyanobacteria…they made ocean formations called stromatolites • These date cyanobacteria back to ~ 3.5 bya

  11. Precambrian Fossils • Other things that happened during the Precambrian include: • Ocean plants evolved • Ocean eukaryotes (organisms with a nucleus) evolved ***Note: ALL fossils found from the Precambrian are from ancient seafloor since no plants or animals has yet to evolve onto land***

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