Earth History

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Across
  1. 3. the branch of science involving the physical composition and history of earth
  2. 5. A fossilized piece of evidence of an organism's activity (footprint)
  3. 7. A common fossil found in many areas from a specific time; used to help identify the age of ither formations
  4. 9. Subdivision of an era
  5. 16. Fossil that forms when organic material is pressed between layers of rock
  6. 18. Fossil that forms when organic material is trapped i ice, rock,amber or tar
Down
  1. 1. method of determining the age of a rock based on measuring radioactive elements (radiometric)
  2. 2. The system of time measurement involving the formation of and changes to earth
  3. 4. Remains or impression of an organism preserved in petrified rock
  4. 6. Determination of the age of a rock based on surrounding evidence
  5. 8. Refers to the information provided by all discovered fossils throughout Earth's history
  6. 10. occurs when a species (organism) dies out and no longer lives on the planet
  7. 11. fossil that forms when minerals solidify into rock around the shape of the original organism, leaving a cavity behind
  8. 12. States that younger rock is found above older rock when comparing sedimentary rock layers
  9. 13. Subdivision of a period; shortest division of geologic time
  10. 14. fossil that forms when a mold is filled with sediment and hardens into the shape of that organism
  11. 15. Very large division of geologic time; usually referred to as the longest division of time
  12. 17. Subdivision of an eon (Paleozoic, Mesozoic, Cenozoic)