Vocab Words Chapter 6

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Across
  1. 2. the time it takes for half of radioactive atoms to decay
  2. 6. eras that are subdivided into units of geologic time
  3. 9. time scale record of the geologic events and the evolution of life forms
  4. 11. Scientists who study fossils
  5. 13. the change in living things over time
  6. 14. Magma that cools and hardens into a mass of igneous rocks
  7. 15. a type of organism that no longer exists and never again will on Earth
Down
  1. 1. Age rocks that age compared to the other rocks
  2. 3. Age number of years that have passed since the rock has formed
  3. 4. geologists divide the time between precambrian time and present time into three long units of time
  4. 5. preserved remains or traces of living things
  5. 7. ball of dust, gas, and ice that orbits the sun
  6. 8. a gap in the geologic record
  7. 10. decay elements that release particles and energy in a process
  8. 12. lava that hardens on the surface and forms igneous rocks