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Geologic Time Crossword

Across
Only found in rocks dating back to 180-206 mya
Indicates that one layer is older or younger but does not say the rocks age.
Younger rocks are on top, older rocks are on the bottom.
Carbon dating-N14
The rocks age in specific years.
To meet the requirements index fossils must be present over large what?
Down
Using the _______ known decay rate , they determine absolute age.
The amount of C14 steadily ________ untill only N14 is left
Measures the concentrations of the original radioactive isotope and of the newly formed isotope.
Carbon Dating-C14
The fossil that only occurs in rocks layers of a particular age.