Different periods of the geologic time scale are different in length. Why?
◦ The time scale was developed ad hoc, as a relative time scale based on rocks and fossil succession with no reference to absolute time when it was developed.
◦ The geologists who developed the time scale did not care about absolute ages.
◦ Early geologists made mistakes, but it was easier to retain the terminology in the time scale.
◦ None of the above.