Geologic Time Scale

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Across
  1. 2. Huge explosion of life - trilobites, Fishes appear.
  2. 5. law that states oldest rock is on the bottom layer
  3. 6. impression of an organisms
  4. 8. Age of the mammals
  5. 10. organism with 3 lobbed exoskeleton. Found at the start of the cambrian explosion.
  6. 11. uses atom to figure out a more 'exact' age of a fossil or rock layer
  7. 14. age of something compared with others
Down
  1. 1. time it takes for half the atoms of an isotope to decay
  2. 3. when magma or dike cuts through a layer it is younger. this is the law of...
  3. 4. division of earths history into time units
  4. 7. Age of the dinosaurs - seed bearing plants
  5. 9. longest part of earths history - simple life
  6. 12. protects earth from suns DEADLY LAZER.
  7. 13. fossil that helps quickly identify how old a rock layer is