Geologic Time Scale Quick Check Why are time periods on the geologic time scale not even in length? (1 point) They are based on the thickness of the Earth's rock layers. They are based on a different type of calendar used to track Earth's history. They are based on the type of fossils found in rock layers of the Earth. They are based on important events that happened in Earth's history.

Answer 1

The correct answer is: They are based on important events that happened in Earth's history.

The geologic time scale is organized according to significant geological and biological events, such as mass extinctions and the emergence of major groups of organisms, rather than being divided into equal time intervals.