AVON RICE

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Across
  1. 3. time it takes for half the atoms of an isotope to decay
  2. 5. gap in the rock layer due to erosion or periods without deposition
  3. 6. era of recent life that began about 66mil years ago
  4. 9. next smaller division of geologic time after the period
  5. 12. third longest division of geologic time
  6. 13. middle era of earths history
  7. 15. age in years or other objects(can be
  8. 16. imprints of an organisms
  9. 17. indent of something
  10. 18. type of body fossil that forms when crystals fill a mold
  11. 19. chlorophyll containing photosynthetic bacteria
  12. 20. longest part of earths history
Down
  1. 1. age of something compared with others
  2. 2. era of ancient life
  3. 4. second longest division of geologic time
  4. 7. group of organisms that normally breed amongst themselves
  5. 8. division of earths history into time units
  6. 10. organism with 3 lobbed exoskeleton
  7. 11. longest subdivision in the geologic time
  8. 14. thin film of carbon residue preserved as a fossil