How are eras and periods of the geologic time scale named?

Question

They are named for the places where geologists first described rocks or fossils from that time.
Their names are based on the names of scientists who discovered the rocks and fossils.
They are named after plants and animals that lived during that time.
Their names are based on the number of centuries within that length of time.

Answer 1

Eras and periods of the geologic time scale are named primarily for the places where geologists first described rocks or fossils from that time. This means the correct option is:

They are named for the places where geologists first described rocks or fossils from that time.

While some geological time units may also be named after specific plants or animals that were prominent during those periods, the naming convention is most commonly associated with geographic locations.