Geological Time Scale Crossword Puzzle

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Across
  1. 1. smallest period of time out of the 4
  2. 4. the era we live in currently
  3. 7. what ends an era; majority of the population dies out
  4. 9. index fossil that was abundant in paleozoic oceans
  5. 10. period modern humans first arrived
  6. 13. 2nd era,age of ancient life
  7. 16. basically the calendar for earth
Down
  1. 2. this is the first era, mainly single cell life
  2. 3. what m.y. stands for
  3. 5. age of medieval life
  4. 6. what b.y. stands for
  5. 8. biggest period of time, have only been 4 so far
  6. 11. smaller than era but bigger than epoch
  7. 12. animal that began in the mesozoic era, wiped out by a meteor
  8. 14. long period of history ending with a mass extinction
  9. 15. first animal that appeared out of amphibians, fish, reptiles