Dating Earth's History Perfect 10

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Across
  1. 2. the time taken for the radioactivity of a specified isotope to fall to half its original value
  2. 5. the process of determining if one rock or geologic event is older or younger than another, without knowing their specific ages
  3. 6. the action or process of forcing body of ingenious rock between or through existing formations, without reaching the surface
  4. 7. a fossil that is useful for dating and correlating the strata in which it is found
  5. 8. a fraction or zone of fractures between two blocks of rock
Down
  1. 1. energy released in the form of particle or electromagnetic waves
  2. 3. the "calendar" for events in Earth's history that subdivides all time into units
  3. 4. the remains or impression of a prehistoric organism preserved in petrified form or a mold or cast in rock