The correct answer is: They are based on important events that happened in earth's history.
Time periods on the geologic time scale are not based on the length of time, but rather on significant events or changes that occurred in Earth's history. These events, such as mass extinctions or the formation of major geological features, are used as markers to divide Earth's history into different time periods. The length of each time period can vary greatly, as it is based on the occurrence of these important events rather than on a consistent measure of time.
Why are time periods on the geologic time scale no even in length?
They are based on the type of fossils found in rock layers of the earth.
They are based on important events that happened in earths history.
They are based on a different type of calendar used to track earths history.
They are based on the thickness of the earths rock layers.
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