Radioactive dating

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Across
  1. 5. a time where the earth's temp drops and ice covers the earth
  2. 9. where scientists try to find out the order in witch events, happened
  3. 10. came up with the Theory of plate tectonics,l, and continental drift.
  4. 12. The earth warming due to green house gasses and human activity
  5. 15. a process that creates new atomic nuclei
  6. 17. when multiple species of animal dies, and within the same time period.
Down
  1. 1. the numeric age of rocks and fossil
  2. 2. the life of atomic nucli
  3. 3. used to describe the mass of a start because it changes over time.
  4. 4. when the Continets move and run into one another.
  5. 6. describes how star wavelengths become shorter and longer
  6. 7. A theory that everything in the universe came into existence at the same time within an explosion.
  7. 8. a process where atoms fuse together
  8. 11. can be used to describe any unit in time no matter how big or small
  9. 13. glaciers include the Wisconson and Illinois ice ages
  10. 14. a period in time that is historically undefined
  11. 16. the longest unit in time
  12. 18. when a star runs out of Hydrogen fuel