Geologic Time Scale

1. Geologic Time Scale Ch 18

2. Geologic Time Scale • Law of superposition- youngest is on top oldest on bottom • Geologic column- arrangement of rock layers

3. Era- A very large unit of time • Period-A division of an Era • Epoch-A division of a Period

4. Section 18.1 review • Scientists use events such as major changes in the earth’s surface and climate and the extinction of various species as the basis for dividing the geologic time scale into units. True

5. Section 18.1 review • Using the law of superposition and the study of index fossils, nineteenth century scientists determined the relative ages of rock layers True False • Eras are subdivisions of periods

6. Section 18.1 review • Scientists can use the geologic column to estimate the relative ages of rock layers only if the rock contains radioactive minerals False • Fossils of mammals are common in Cenozoic rocks True

7. Complete the statement • Rock layers in the geologic column can be distinguished from one another according to rock type and__________ • The geologic era that followed Precabrian time is called the _________ Fossil content Paleozoic Era

8. Complete the statement • According to the geologic column in the diagram, the oldest rock layer is__________ • Based on late Precambrian fossils and other types of geological evidence, scientists theorize that life began _________ Layer 4 In the ocean

9. Last question in 18.1 • The era that is divided into epochs is the ___________ Cenozoic Era

10. Theory of Evolution • Organisms change over time. New kinds of organisms are derived from ancestors.

11. Precambrian time • Started 4.6billion years ago • Ended 540million years ago • Characteristics of this time: • Soft-bodies or single cell organisms, Stromatolites • Lots of volcanoes, mountain formation, sediment formation & metamorphism

12. Paleozoic Era 540-248 million years ago • Periods: • Cambrian • Ordovician • Silurian • Devonian • Carboniferous • Permian

13. Paleozoic Era 540-248 million years ago • Cambrian • Advanced forms of marine life and first invertebrates appear • Ordovician • Brachiopods increase: trilobites decline: graptolites flourish: First vertebrates (fishes appear)

14. Paleozoic Era 540-248 million years ago • Silurian • First land plants and animals appear • Devonian • Age of fishes • First amphibians • Ferns and cone bearing plants

15. Paleozoic Era 540-248 million years ago • Carboniferous • Split into two epochs: Mississippian and Pennsylvanian • Amphibians flourish • Giant cockroaches • Permian • Pangaea comes together mass extinctions

16. Mesozoic Era248-65 million years ago • Periods • Triassic • First Dinosaurs, tropical weather, • Jurassic • Large Dinosaurs, tropical weather, • Cretaceous • First flowering plants, mass extinction

17. Cenozoic Era65 million years to today • Periods • Tertiary • Paleocene • Oilgocene • Miocene • Pliocene • Quaternary • Pleistocene • Holocene

18. Cenozoic Era65 million years to today • Periods • Tertiary • Age of mammals • Pangaea separates • Quaternary • Ice age and human’s develop

19. 18.2 review • The presence of cross-bedded sandstone may indicate that the region where it is present was once: • Shields are large areas of exposed rock of what era? • The fossil record indicates that which of the following thrived during the Paleozoic Era A desert Precambrian Advanced forms of marine life

20. 18.2 review • The Devonian period is also known as the Age of • Dinosaurs first appeared during the • During which era did glaciers cover nearly one third of the earth’s land area? Fishes Triassic period Cenozic

21. 18.2 review • During which epoch did the first modern horses appear? • Which geologic period is missing from this diagram? Pilocene Silurian The Paleozoic Era Cambrian Ordovician_________Devonian  Time

22. 18.2 review • What are the most common Precambrian fossils called? • Which period of the Cenozoic Era includes the time before the last major ice age Stromatolites Tertiary