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The Rock Record

The Rock Record. Chapter 21.1. The geologic time scale, based on fossil evidence , is used to organize the history of Earth’s living creatures into time periods in which they existed. Many geologists believe the Earth to be about 4.6 billion years old.

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The Rock Record

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  1. The Rock Record Chapter 21.1

  2. The geologic time scale, based on fossil evidence, is used to organize the history of Earth’s living creatures into time periods in which they existed. Many geologists believe the Earth to be about 4.6 billion years old. -They have divided this vast amount of time into large sections called eons. -Eons are subdivided into eras. -Eras are furthered divided into periods. -Periods are divided into epochs. Video – Fossil Record (1:28 min)

  3. Many geologists believe that it was during the Cambrian period that life on Earth increased dramatically. The time segments prior to this event have been lumped together and referred to as the Precambrian. Several periods are marked by sudden mass extinctions where as much as 90% of life forms disappeared from Earth. Assignment: “Visualizing the Evolutionary Geologic Time Scale” Video – Mass Extinction (4:50 min)

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