Universe Unit Crossword

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Across
  1. 4. Times where huge sheets of ice covered Earths surface.
  2. 5. Smaller divisions of time
  3. 7. a rocks age based on other rocks around it.
  4. 11. the exact number of years since the rock formed.
  5. 14. The time it takes for half of the radioactive atoms to decay.
  6. 15. Very small temperature changes that happen slowly
  7. 16. when we can tell if a star is moving away or towards us.
  8. 17. Large divisions of time.
  9. 18. When the continents were close together and created one continent.
Down
  1. 1. the process of how atomic nuclei are formed in space.
  2. 2. The reason why we have lots of lakes
  3. 3. how astronomers describe the mass of stars.
  4. 6. The enormous explosion that created the universe.
  5. 8. When lighter elements join together to create heavier elements.
  6. 9. When a large number of species disappear.
  7. 10. When stars run out of fuel to become a red giant or supergiant.
  8. 12. A very large span of time.
  9. 13. He found that continents weren't always in one place.