Earth-Space Ch 15

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Across
  1. 1. Age that is the actual age.
  2. 5. Age dating by tree rings.
  3. 6. Age that is in comparison with other ages.
  4. 9. 4.6 billion years old
  5. 10. Preserved remains of past organisms.
  6. 13. Layers of rocks that are similar in composition.
  7. 14. Fossils that include shells, bones, and teeth.
  8. 16. Stresses that push toward each other.
  9. 17. Fossils that indicate the relative age of the rock in which it is found.
Down
  1. 2. Rings of wood equaling 1 year of tree growth.
  2. 3. Paired deposits of sediments in glacial lakes.
  3. 4. Amount of time required for half of radioactive atoms to decay.
  4. 7. The inside of sheets of ice.
  5. 8. Fossils that are evidence of activity of an organism. Includes tracks and bite marks.
  6. 9. Fossilized tree sap.
  7. 11. Atoms of an element that has a different number of neutrons.
  8. 12. A gap between rock of very different ages.
  9. 15. An impression made in sediment.