A Trip Through Geological Time

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Across
  1. 5. A break in Earth's crust
  2. 6. A ball of dust, gas, and ice that orbits the sun
  3. 8. A solid copy of the shape of an organism
  4. 9. Magma that cools and hardens into a mass of igneous rock
  5. 10. Long units of time
  6. 11. A gap in the geologic record
  7. 12. Its age compared to the ages of other rocks
  8. 13. A process in which elements release particles and energy
  9. 15. Lava that hardens on the surface and forms igneous rock
  10. 16. An animal without a backbone
  11. 19. A record of the geologicic events and the evolution of life forms as shown in the fossil record
  12. 21. The number of years that have passed since the rock formed
  13. 22. An animal that lives part of its life on land and part in water
  14. 23. No longer exists and will never again live on earth
  15. 25. The change in living things over time
  16. 26. A fossil that widely distributes and represents an organism for a geologically short period of time
  17. 27. An extremely thin coating of carbon on rock
  18. 29. A vertebrate that can control its body temperature and feeds milk to its young
Down
  1. 1. Provides evidence of the activities of ancient organisms
  2. 2. In undisturbed horizontal rock layers the oldest layer is at the bottom
  3. 3. Scaly skin and lay eggs that have tough leathery shells
  4. 4. Fossils in which minerals replace all of an organism
  5. 7. Scientist that studies fossils
  6. 14. Units of geological time (subdivision of eras)
  7. 17. An animal with a backbone
  8. 18. The time it takes for half of the radioactive atoms to decay
  9. 20. Many types of living things became extinct at the same time
  10. 24. A hollow area in sediment in the shape of an organism
  11. 28. The preserved remains or traces of living things