Geologic time periods are divided into segments based on two pieces of information describe them

The geologic time scale is divided based on the major changes in the earth’s surface and climate, and the other thing that divides them is the extinction of species. The appearance and disappearance of fossils also help influence this division.

This would be an open primary. a closed primary people can vote only prior to election day if the party if they are registered. independent voters can not participate. there is not a wide-open primary, but there is a semi-open primary.