Reconstructing Earth's History Crossword

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Across
  1. 3. ___ equals 1 million years
  2. 5. we are currently in the __ epoch
  3. 7. these are what eras get divided into
  4. 9. equal hundreds of millions of years long
  5. 12. if you wanted to know what earth looked like millions of years ago, start with these.
  6. 13. scientists use fossil evidence to find the _____ ages of rock layers.
  7. 15. these are what periods get divided into
  8. 16. mass ____ occur when a large number of species go extinct over a short period of time.
  9. 17. ___ equals 1 thousand years
Down
  1. 1. the mesozoic era has ____ periods
  2. 2. ____ equals 1 billion years
  3. 3. Scientists construct ____ that explain Earth's history by comparing sequences of rock strata from different locations
  4. 4. equal billions of years long
  5. 6. there have been ___ major mass extinctions in Earth's history.
  6. 8. also known as sea lilies. An extinct group of ocean creatures.
  7. 10. this eon is what we are currently in
  8. 11. the geologic ___ scale is a model of earth's history divided into main units of geologic time.
  9. 14. this eon lasted the longest (over 1 billion years)