Are eons subdivided into periods

Yes, eons are subdivided into eras, which are further divided into periods. The geological time scale is structured hierarchically, with eons being the largest divisions, followed by eras and then periods. Each period is characterized by significant geological and biological events. For example, the Phanerozoic Eon includes the Paleozoic, Mesozoic, and Cenozoic eras, each containing multiple periods.