The Geologic Time Scale

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Across
  1. 2. The meteorite that struck Earth in the Paleogene period caused a change in global _______
  2. 3. Element found in the K-T boundary that is not prevalent on Earth
  3. 5. Earth's _________ was 4.6 billion years ago
  4. 7. Epoch in which humans began to form civilizations
  5. 10. An event in which many species become extinct in a short time; they occur every 26 to 30 million years on average and are known as mass ___________
  6. 11. Cause of the mass extinction of the dinosaurs after the Cretaceous period
  7. 14. Extensive glaciation occured before the______
  8. 15. By the end of the Carboniferous period, the first ____ began to roam the forests
  9. 16. Era that means "recent life"
  10. 17. The appearance of the first mammals
Down
  1. 1. Number of eras in the Phanerozoic eon
  2. 2. Groups of organisms rapidly diversified in the _______ explosion
  3. 4. Birds evolved from ________, who lived in the Mesozoic era
  4. 6. The land mass that existed on Earth 225 million years ago
  5. 8. 90 percent of all history
  6. 9. Largest division divides the scale into ______ parts
  7. 12. Movement of plate ________ that make up the surface of Earth
  8. 13. The model that expresses the major geological and biological events in Earth's history is known as the ________ time scale