Earth & Space Crossword!

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Across
  1. 2. hard pieces that form the frame of each human
  2. 6. a long period of history with occurring events
  3. 7. wind, water or other natural agents
  4. 9. to adjust to its surroundings
  5. 10. mass extinction of about 90% of marine species and 70% of terrestrial species
  6. 11. Also known as "The Age Of The Dinosaurs"
  7. 13. extinction of a large number of species
  8. 15. a layer filled with sedimentary rock from the same age
  9. 17. presence of numerous marine algae species
  10. 18. appearance of first flowering plants
  11. 20. a solid inorganic substance
Down
  1. 1. appearance of first amphibians and insects
  2. 3. multiplication of reptile and insect species
  3. 4. a star, main source of light and heat in the solar system
  4. 5. formed by compressed sediments
  5. 8. when the remains of an organism harden
  6. 12. preserved remains of an organism
  7. 14. the result of a force applied to a surface
  8. 15. group of organisms that can reproduce
  9. 16. person who studies the ancient life
  10. 19. appearance of 1st dinosaurs