Geologic Time Scale Puzzle

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Across
  1. 4. The Earth is currently in the ___________ Period
  2. 10. The radioactive ____________ change over time, and this helps geologists determine the approximate age of the rock.
  3. 11. ___________occurs over an extended period
  4. 12. Geologists use ____________ to discover the age of substances found throughout the Earth.
  5. 13. The age of the __________ is about 4.6 billion years old
Down
  1. 1. During the ___________ Era and future periods, many organisms became extinct
  2. 2. _____________ Time is the chronological time related to the events that have occurred during Earth's history
  3. 3. The scale is broken down into ________, eras, periods, epochs, and events.
  4. 5. The algae and other organisms during this time-period released _________ into the air
  5. 6. the ________________ Period is known as the 'Age of Man.'
  6. 7. The Geologic Time __________ (GTS) is used to show the development of the Earth during its 4.6-billion-year existence.
  7. 8. The _____________ Era is called the 'age of Reptiles'
  8. 9. Early life during the ______________ Era is found in the seas only