Geologic time and Earth's History

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Across
  1. 3. age of mammals
  2. 5. any rock fragments that are included in a rock must be older than the rock in which they are included.
  3. 8. author of the theory of evolution.
  4. 10. large reptile like creatures alive during early times on earth.
  5. 11. the preserved remains of an organism that has died.
  6. 12. Next to longest subdivision; marked by major changes in the fossil record
  7. 17. occurs when no more members of a particular species remains.
  8. 19. animals that live in water for the earlier parts of life and go onto land during the rest of their lives.
  9. 22. states that layers of sediment initially extend laterally in all directions
  10. 23. the species of man that live today
  11. 25. means rock
  12. 26. Longest subdivision; based on the abundance of certain fossils
  13. 27. Shortest subdivision; marked by differences in life forms and can vary from continent to continent.
  14. 30. people who study fossils
  15. 31. said to be the closest descendants of dinosaurs.
  16. 32. closest species of animals related to humans
  17. 33. the earliest animals that lived had hard outer layers called
  18. 35. divides up the history of the earth based on life-forms that have existed during specific times since the creation of the planet.
  19. 36. our planet
  20. 38. activity commonly happened during precambrian period releasing ash and lava.
  21. 40. When organism parts are pressed between layers of mud or clay that hardens over time, squeezing the decaying organism away and leaving a carbon imprint in the rock, since all living things contain carbon.
  22. 41. refers to the process where over long periods of time, helpful variations can appear in a species while “unfavorable” one disappear.
Down
  1. 1. The organism decays slowly inside the rock, leaving an cavity in the shape of the organism.
  2. 2. When the mud or sand hardens into rock where a footprint, trail or burrow was left behind.
  3. 4. Minerals like calcium can soak into the buried remains of an organism. The mineral replaces the remaining bone and changes it into rock.
  4. 6. The cavity or mold mentioned above can filled in with mud. When the mud hardens, it takes on the shape of the organism.
  5. 7. a principle of geology that states that the geologic feature which cuts another is the younger of the two features.
  6. 9. the earliest era of earth
  7. 13. the substance that is crucial to the life sustaining environment of earth.
  8. 14. the period during the mesozoic era where dinosaurs were dominant.
  9. 15. caused by a large comet that impacted the earth in present day Mexico
  10. 16. sudden change in the world's climate.
  11. 18. All rock layers were originally deposited horizontally.
  12. 20. the idea that Earth has always changed in uniform ways and that the present is the key to the past.
  13. 21. other term for marine animals.
  14. 24. the largest continent that is believed to be the origin where the continents of today broke off from.
  15. 28. The layer on the bottom was deposited first and so is the oldest.
  16. 29. a phenomenon where the earth is covered in ice.
  17. 34. animals that have specific glands to feed their young.
  18. 37. Based on types of life existing at the time
  19. 39. age of reptiles