Chapter 9:View of Earth’s Past

Megan Darvish June 1

Geologic Column

• Represents a timeline of Earth’s history• Invented in the 19th century• Oldest rock at top bottom• Newest rock at the top• Distinguished by the type of rock and kinds of

fossils• Fossils in more recent layers are modern day

plants/animals

Using a Geologic Column

• Uses ages of rock layers• Radiometric dating• Compare two similar rocks together; if

matched, probably from same time period

Divisions of Time

• Marked by climate, Earth’s surface, and types of organisms

• So long scientists use abbreviations • Separated into periods/eras

Major Elements of Column

• Precambrian Tertiary• Mesozoic Permian• Cenozoic Carboniferous • Paleozoic Devonian• Cretaceous Silurian• Jurassic Ordovician• Triassic Cambrian • Quatemary

Law of Superposition

• States that older rock layers will sink to the bottom of the strata due to age.

• Intrusions are youngest, most often.

Eon

• Period in time marked by major events• Precambrian Eon• Lasted approx. 4,058 million years• Cambrian Eon• From when the Precambrian Eon ended until

present day

Era

• Important time periods within an eon• Paleozoic• Lasted 251 million years• Mesozoic• Lasted 65.5 million years• Cenozoic• Present day

Period

• Cambrian- 542 million years• Ordovician- 488 million years• Silurian- 444 million years• Devonian- 416 million years• Carboniferous (includes Pennsylvanian and

Mississippian)- 677 million years• Permian- 299 million years• Triassic- 251 million years

Period

• Jurassic- 200 million years• Cretaceous- 146 million years• Tertiary- 183.5 million years• Quaternary- approx. 1.8 million years

Epoch

• Only in the Cenozoic Era• Longer than an age; shorter than a period• Divided into ages- events of distinct fossils in

the fossil record• 7 total• 5 in the Tertiary Period• 2 in the Quaternary Period

Epoch

• Tertiary:• Paleocene- 65.5 million years• Eocene- 55.8 million years• Oligocene- 33.9 million years• Miocene- 23 million years• Pliocene- 5.3 million years

Epoch

• Quaternary:• Pleistocene- 1.8 million years• Holocene- .0115 million years

When do I live?

• Cenozoic Era• Quaternary Period