1. Chapter 9 Study Notes
A View of Earth’s Past

3. 1
A geologic _________ is usually named for the place where its characteristic ______ were first discovered.
period
fossils

4. 2 A large area of ______ Precambrian _____ is called a _______.
exposed
rocks
shield

5. 3 A _______ is a unit of geologic time into which an era is divided.
period

6. 4
According to the ______ hypothesis, dinosaurs became extinct when a giant meteorite crashed into Earth.
impact

7. 5 _________ became _______ at the end of the _________ era. Dinosaurs
extinct
Mesozoic

8. 6
Geologic time is divided into ____________.
four eons

9. 7
If the Cretaceous Period began about ______, this means it began __________ years ago.
146-Ma
146-million

10. 8
_______ fossils can be used to _____ rocks.
Index
date

11. 9 _________ became the dominant animals during the ________ era.
Mammals
Cenozoic

12. 10
Nearly half the Earth’s valuable mineral deposits are found in rocks from __________ time.
Precambrian

13. 11
New mammal species developed when temperatures ______ during the ice ages of the Cenozoic Era.
decreased

14. 12 On a geologic column, the ______ _____ are on the _______.
oldest rocks
bottom

15. 13
Rock _______ that match a similar layer in a geologic column may have formed at the ______ time.
layers
same

16. 14
Scattered landmasses on Earth merged into a _______ _______ during the Paleozoic Era.
super continent

17. 15
Scientists created the first _________ __________ by determining the relative ages of sedimentary rock in areas all over the world.
geologic
column

18. 16
Scientists have most accurately determined the _______ ages of rock layers by using radiometric dating methods.
absolute

19. 17 The __________ Era is known as the Age of ________ . Cenozoic
Mammals

20. 18
The division of geologic time that makes up about ____ % of Earth’s history is called _____________ time.
88%
Precambrian

21. 19
The geologic column is an ordered arrangement of rock layers ______ on their ____.
based
ages

22. 20
The geologic _____ ______ is a table that outlines the development of _______.
time scale
Earth

23. 21
The ________ development of new organisms from preexisting organisms is called _______.
gradual
evolution.

24. 22 The most common Precambrian _________ are ________. fossils
stromatolites

25. 23 The ________ Epoch began about 5.3 Ma, or 5.3 _______ ______ ago.
Pliocene
million years

26. The End!!!