How did scientist first designed the geologic time scale

The scientist first designed thee geologic time scale because the people who needed to understand the geological relationship of different rock units were miners. Mining had been of commercial interest since at least the days of the Romans, but it wasn't until the 1500s and 1600s that these efforts produced an interest in local rock relationship. 

The figure is not necessarily a parallelogram because only one diagonal is bisected and only one pair of sides is congruent.

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