Geological Eras

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Across
  1. 2. A period of time in Earth's history characterized by particular fauna and flora
  2. 6. A type of fossilization in which an organism is preserved in a solidified tree resin
  3. 7. The division of geologic time that is longer than an eon
  4. 9. A group of organisms that do not have a nucleus and are often found in extreme environments
  5. 11. The study of fossils
  6. 12. A period in Earth's history characterized by the first appearance of land animals
  7. 13. The period in Earth's history from about 2.5 to 4 billion years ago
  8. 15. A type of fossilization in which a hollow impression of an organism is left in sedimentary rock
  9. 17. A period in Earth's history characterized by the dominance of dinosaurs
  10. 19. A geological time division shorter than an era but longer than an age
  11. 20. The process of change in all forms of life over generations, driven by natural selection
  12. 23. A type of fossilization in which minerals replace the organic matter of an organism
  13. 25. A period in Earth's history when amphibians were dominant
  14. 27. A period in Earth's history characterized by the rise of mammals and birds
  15. 28. A group of organisms lacking a nucleus and other membrane-bound organelles
  16. 29. A period in Earth's history characterized by the rise of humans
Down
  1. 1. A period in Earth's history characterized by the rise of fish
  2. 2. A period in Earth's history characterized by the rise of mammals
  3. 3. A type of invertebrate characterized by a hard outer shell and two hinged parts
  4. 4. The period in Earth's history from about 252 to 66 million years ago
  5. 5. A fossilized impression of an organism formed in sedimentary rock by the impression left by its remains
  6. 8. A period in Earth's history characterized by the dominance of flowering plants
  7. 10. A group of invertebrates characterized by a hard outer shell and jointed legs
  8. 14. A group of organisms with a nucleus and other membrane-bound organelles
  9. 16. A period in Earth's history characterized by the first appearance of complex life forms
  10. 18. The process by which organic material is preserved in a fossil
  11. 21. A period in Earth's history characterized by the dominance of reptiles
  12. 22. The period in Earth's history from about 541 to 252 million years ago
  13. 24. A period of time in Earth's history characterized by a particular set of rock layers
  14. 26. A division of geologic time longer than an era but shorter than a supereon