Before radiometric dating, how did scientists assign the age of the rock layers that are found in the Earths crust?

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    by measuring the amount of radioactive elements that were in the layers
    by the types of fossils that were found in the layers
    by measuring the thickness of the layer in centimeters; each centimeter was equal to 100 years
    by looking at the different types of rocks that were found in each layer
asked May 19, 2013 in Biology by anonymous
    

1 Answer

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by the types of fossils that were found in the layers
answered May 20, 2013 by Bioshare ~Top Expert~ (34,070 points)

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