Earth’s Geological Time

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Across
  1. 1. Long units of time.
  2. 5. Record of geological events and the evolution of life forms.
  3. 6. Helped scientists determine the absolute age of the divisions in the geologic time scale.
  4. 8. Scientists first developed the geologic time scale by studying.
  5. 9. Includes three periods: the Triassic period, the Jurassic period, and the Cretaceous period.
  6. 11. Provided evidence of change on Earth.
  7. 12. Geologists use the start of a period of major global cooling to mark the beginning of.
Down
  1. 2. At the end of the Cretaceous period, major volcanic eruptions coincided with the impact on Earth of a.
  2. 3. The Mesozoic era is defined by the dominance of.
  3. 4. Eras divided into units.
  4. 7. Covers about 88 percent of Earth's history.
  5. 10. The new boundary, based on new physical evidence, reflects a major change in Earth's.