The Earth and Space

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Across
  1. 3. A rock formed from consolidated clay sediments
  2. 5. Organic material is converted into stone with the replacement of minerals
  3. 15. Physical force used against an object
  4. 16. A layer of rock from a certain time period
  5. 19. An era from 230 million to 190 million years ago (disappearance of dinosaurs)
  6. 20. The extinction of a large number of species within a relatively short period of geological time
  7. 21. The star around which the earth orbits
Down
  1. 1. An era from 500 million to 425 million years ago
  2. 2. A long and distinct period of history with a particular feature or characteristic
  3. 4. A discharge of electricity
  4. 6. A change where a species becomes better suited with its environment
  5. 7. A group of living organisms who look similar and are able to reproduce
  6. 8. The eruption of a volcano
  7. 9. Hard, whitish tissue making up the skeleton in humans
  8. 10. A specialist in paleontology
  9. 11. An era from 135 million to 63 million years ago
  10. 12. An era from 405 million to 345 million years ago
  11. 13. A solid inorganic substance of natural occurrence
  12. 14. The process of being eroded by natural agents
  13. 17. An era from 280 million to 230 million years ago
  14. 18. The remains of an organism preserved in petrified form