Geological Time Puzzle

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Across
  1. 4. Believed to have caused extinction of dinosaurs
  2. 7. Period of the cenozoic the present era, that are further divided
  3. 8. began about 65 million years ago with the cretaceous mass extinction and continues to present
  4. 10. stretches from about 2.6 million years ago to the present
Down
  1. 1. a period when dinosaurs lived
  2. 2. Eon The atmosphere had no free oxygen until
  3. 3. began about 540 million years ago as the global supercontinent pannotia was breaking up
  4. 5. Paleozoic, mesozoic, and cenozoic
  5. 6. Much for Earth's land surfaces were located near the poles and covered in ice
  6. 9. Released oxygen in the air during the process of photosynthesis