Crossword Radioactive Puzzle

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Across
  1. 5. How long a star will live based on the mass of it.
  2. 8. A very long period of time.
  3. 11. Period of time known as a half-life.
  4. 12. A long and distinct period of history.
  5. 13. Lighter elements join to form heavier elements.
  6. 14. Many different points in history continents were located close to each other.
  7. 16. Came up with the idea that Earth's continents were not always in their current locations.
  8. 18. A rock's age compared to the ages of the rocks around it.
Down
  1. 1. Exact number of years since the rock formed.
  2. 2. Star begins to run out of fuel.
  3. 3. Large number of species disappearing in a short time.
  4. 4. The amount of time it takes for half of the radioactive atoms to go away.
  5. 6. Lakes were formed due to glaciation.
  6. 7. Protons and neutrons that joined together to form elements.
  7. 9. Typically small changes that occur slowly on Earth.
  8. 10. To tell if an object is moving toward or away from us.
  9. 15. Glaciers covered large parts of Earth's surface.
  10. 17. A universe formed billions of years ago.