1. Physical Geology Chapter 9 Geologic Time

2. Geologic Column Represents a timeline of earth’s history Combined observations from many places, many people Ordered arrangement of rock layers Oldest rocks at the bottom Comparative dating made possible Best form is the Geologic Time Scale

6. Eons Hadean (precambrian) Archean (precambrian) Proterozoic (precambrian) Phanerozoic (divided into eras)

7. Eras Subdivisions of eons Phanerozoic Eon –Paleozoic – simplest marine/terrestrial life forms –Mesozoic – early birds and reptiles –Cenozoic – mammals to man

8. Periods Subdivisions of Eras Characterized by index fossils and named for where first discovered Divided into epochs by more complete and detailed fossil record

9. Epochs Most specific of index fossils Divided into ages of dominant life forms with distinct individual fossils History is a record of past events whether found in books or in solid rock! Rock record indicates environments, too

10. Evolution Change (scientifically, in forms of living things) Change has occurred; mechanisms of change highly debated Current scientific explanation is the theory of evolution by natural selection (Darwin)

12. What about recently?