GEOLOGIC TIME (HISTORY)

Geologic history can be divided into five great Eras of recorded time. These Eras and approximate time periods include: (1) Archeozoic: 4,500 million years ago (MYA) to 3,500 MYA; (2) Proterozoic (or Prepaleozoic): 3,500 MYA to 586 MYA; (3) Paleozoic: 570 MYA to 230 MYA; (4) Mesozoic: 230 MYA to 65 MYA; and (5) Cenozoic: 65 MYA to present.