1. A few sample MC on metamorphic rocks….
Marble is a metamorphic rock that forms from __________?
A. granite
B. limestone
C. sandstone
D. shale
Answer = B (page 193)

2. A few sample MC on metamorphic rocks….
What is the pressure on a rock at 15 kilometers depth in the Earth’s crust?
A. approximately 4 times atmospheric pressure
B. approximately 40 times atmospheric pressure
C. approximately 400 times atmospheric pressure
D. approximately 4000 times atmospheric pressure
Answer = D (page 195)

3. A few sample MC on metamorphic rocks….
Which of the following processes will cause metamorphism?
A. an increase in pressure
B. an increase in temperature
C. interaction with hydrothermal fluids
D. all of the above
Answer = D (page 194)

4. A few sample MC on metamorphic rocks….
What type of metamorphism is caused by high temperature and high pressure imposed over a large volume of crust?
A. burial
B. contact
C. regional
D. shock
Answer = C (page 197)

5. A few sample MC on metamorphic rocks….
 Which of the following is not used to classify foliated rocks?
A. the metamorphic grade
B. the nature of the foliation
C. the size of the crystals
D. the texture of the parent rock
Answer = D (pages )

6. A few sample MC on metamorphic rocks….
Which of the following statements about the metamorphism of a shale is false?
A. With increasing metamorphism, clay minerals break down to form micas.
B. With increasing metamorphism, the grain size of the rock gets smaller.
C. With increasing metamorphism, foliation develops.
D. With increasing metamorphism, the amount of water in the rock decreases.
Answer = B (page 200)

7. TODAY: Chapter 10 Geologic Time 1) Relative dating principles
1) Relative dating principles
2) Correlation of rock layers
3) Absolute dating w/ radioactivity
4) Geologic time scale

8. Chapter 10 Study questions
What is the difference between absolute and relative dates, and how are they determined? Know the principles of original horizontality and superposition.
Learn the basics of fossils and how they’re used, concepts of faunal succession, formation.
How do we correlate rock layers in different regions?
What are the different types of unconformities, how do you apply cross-cutting relationships to determine the relative sequence of strata?
How was the geologic time-scale created? Study the most important divisions (eons, eras) of the geological time scale and extinctions between major divisions.
How do apply radioactive decay of some elements to add absolute dates to the geologic time scale (radiometric dating)?

9. “Telling time geologically”
1. Relative Dating: Key principles
“Telling time geologically”
Earth’s history concealed in rocks
Goal of geology: unraveling Earth’s history
Principle time keeping devices:
Relative dating - putting rocks/events in proper order
Absolute dating - determining rocks/event’s actual age

10. 1. Relative Dating: Key principles
A bed of rock is older than that above, younger than that below
Law of superposition
Principle of original horizontality
Principle of cross-cutting relationships
Inclusions
Unconformities
T&L Figure 8.2

11. Superposition is well illustrated by the strata in the Grand Canyon

12. 1. Relative Dating: Key principles
Law of superposition
Principle of original horizontality
Principle of cross-cutting relationships
Inclusions
Unconformities
A bed of rock is older than that above, younger than that below
Sedimentary layers deposited flat
T&L Figure 8.3

13. 1. Relative Dating: Key principles
Law of superposition
Principle of original horizontality
Principle of cross-cutting relationships
Unconformities
A bed of rock is older than that above, younger than that below
Sedimentary layers deposited flat
Faults & dikes are younger than beds they cross
See Figure Story 10.11

14. 1. Relative Dating: Key principles Unconformities
An unconformity is a break in the rock record produced by erosion and/or nondeposition of rock units
(Conformable layers: deposited w/out interruption)

15. Example: Grand Canyon 1. Relative Dating: Key principles
Has record of a huge expanse in time, and
multitude of sedimentary environments…
But: The record of time is not continuous because of
geological processes that happened after deposition.
Movie: watch for terminology of different kinds of
Unconformities and relative dating methods

17. Unconformities 3 types Angular unconformity Disconformity
Relative Dating: Key principles
3 types
Angular unconformity
Disconformity
Nonconformity

18. Unconformities 3 types Angular unconformity Disconformity
Relative Dating: Key principles
3 types
Angular unconformity
Disconformity
Nonconformity
Tilted/folded sedimentary rocks overlain by younger, more flat layers
See Fig. 10.6

19. Recipe for an angular unconformity
Deposition
Folding/Uplift
Erosion
Subsidence/more erosion
See Fig. 10.8

20. Unconformities 3 types Angular unconformity Disconformity
Relative Dating: Key principles
3 types
Angular unconformity
Disconformity
Nonconformity
Layers on either side of unconformity are parallel
See Fig. 10.7

21. Unconformities 3 types Angular unconformity Disconformity
Relative Dating: Key principles
3 types
Angular unconformity
Disconformity
Nonconformity
Interface between sedimentary layers and metamorphic or igneous rock