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. True False 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. False True 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 Era 248-65 million years ago
Periods
Triassic
First Dinosaurs, tropical weather,
Jurassic
Large Dinosaurs, tropical weather,
Cretaceous
First flowering plants, mass extinction

17. Cenozoic Era 65 million years to today
Periods
Tertiary
Paleocene
Oilgocene
Miocene
Pliocene
Quaternary
Pleistocene
Holocene

18. Cenozoic Era 65 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. Cambrian Ordovician_________Devonian
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