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The Geologic Timeline

The Geologic Timeline. Geologic Time Scale. The division of Earth’s history is divided into units of time, based on the fossil records contained in the rocks. The Geologic Time Scale is broken-up into four major divisions… Eons, Eras, Periods, Epochs. Eons of Geologic Time.

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The Geologic Timeline

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  1. The Geologic Timeline

  2. Geologic Time Scale • The division of Earth’s history is divided into units of time, based on the fossil records contained in the rocks. • The Geologic Time Scale is broken-up into four major divisions… • Eons, Eras, Periods, Epochs

  3. Eons of Geologic Time • These are the largest division • They are measured in hundreds of millions to billions of years • There are four of them • Hadean • Archaean • Protoerozoic • Phanerozoic • Hadean, Archaen and Proterozoic are often classified as “Precambrian Time”

  4. Precambrian Time • The Hadean Eon (4.6 – 3.8 Billion Years Ago) • Earth cooled and formed from a cloud of gas, and from asteroid collision. • Iron and Nickel sank to the core. • Oxygen and Silicon rose to the surface. • Earth’s solid surface is created • (Hadean is sometime not recognized) • The Archaean Eon (3.8 – 2.5 Billion Years Ago) • An early atmosphere develops • Ancient oceans develop • Continent-building occurs • The first forms of life (bacteria) arrive • The Proterozoic Eon (2.5 Billion – 543 Million Years Ago) • Single, super continent of Rodinia forms • Atmosphere becomes oxygen-rich • Multi-cellular plant and animal life develops

  5. Eras of Geologic Time • The Eras are the second longest division of the geologic time scale • They are measured in hundreds of millions of years • They are defined by the life forms found in the rocks as fossils

  6. The Phanerozoic Eon, and the “Big Three” Eras • The fourth Eon (Phanerozoic) contains the only real Eras... • The Paleozoic Era • An explosion of life forms • Fish develop • Life comes on land • Giant insects • The Mesozoic Era • Pangaea is formed • Reptiles and Dinosaurs thrive • The Cenozoic Era • Flowers, Birds and Mammals thrive • Pangaea breaks up • Volcanoes and Mt. Building occur • Remember that an Era is defined by the different life forms found as fossils in the rocks.

  7. Periods of Geologic Time • Geologic Periods are defined by the life forms that were abundant, or became extinct. • Each Era is broken-down into multiple Geologic Periods, based on the life forms that thrived or died • They are measured in millions to tens of millions of years

  8. Epochs of Geologic Time • These are the smallest of the major divisions • They are measured in millions of years to tens of millions of years • They are distinguished by different groups of organisms

  9. So where are we… • We are in the… • Phanerozoic Eon… • The Cenozoic Era… • The Quaternary Period… • The Holocene Epoch.

  10. A “graph” representing Geologic Time • Label the… • The Hadean Eon, • Archaean Eon, • Proterozoic Eon • Label all three of the early Eons as “Pre-Cambrian” Time. • Label the… • Paleozoc Era • Mesozoic Era • Cenozoic Era • Label all three of these Eras as the Phanerozoic Eon.

  11. A “football field” representing Geologic Time

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