Name:___________________________________ Date:________________
Chapter 12 Geologic Time
12.1
Define:
Uniformitarianism –
Relative dating –
Law of superposition –
Principle of original horizontality –
Principle of cross – cutting relationships –
Unconformity –
Correlation –
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1. Rocks record ___________________ events and changing ___________ forms of the past.
2. What has removed a lot of Earth’s rock but left enough to be studied and interpreted?
3. Earth is much ____________ than anyone had previously imagined and its surface and interior have been changed by the same
_________________________.
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4. What is the primary goal of a geologist?
5. Which rocks best explain the past?
6. Who put forth the fundamental principle of uniformitarianism?

7. Uniformitarianism means that the ____________ and _____________ we observe today have been at work for a ________________________.
8. What do we have to do before we can understand the past?
9. Relative dating tells the ______________ in which ____________ occurred, not _____________________________.
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10. Who thought of the law of superposition?
11. The law of superposition states that in an undeformed sequence of
____________________ rocks, each bed is ____________ than the one above it, and ________________ than the one below it.
12. What else did Steno observe?
13. The principle of original horizontality means that layers of sediment are generally deposited in a ___________________ position.
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14. What was Steno’s 3 rd observation?
15. Summarize the principle of cross cutting relationships.
16. What is an inclusion?
17. The inclusions indicate that the _______________ layer was deposited on
__________ of the weathered igneous mass.
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18.What does an unconformity represent?
19. Give 2 reasons why unconformities are important to a geologist.

20. What are 3 basic types of unconformities?
21. Which is most easily recognized?
22. How does it appear?
23. An angular unconformity indicates that during the pause in _____________, a period of deformation (__________________________) and
_______________ occurred.
24. What is the difference in a disconformity and a nonconformity?
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25. How do we develop a geologic time scale that can be applied to the entire
Earth?
26. How can you correct the problem of having rocks covered by soil and vegetation when correlating rocks in a locality?
27. Be a geologist! Practice relative dating! List the letters in the following picture in the order of which came first.

In the space provided, create your own relative dating puzzle. Look at the puzzle above to get an idea of how to code your separate layers. Make it hard! Whoever makes the hardest puzzle to solve that still makes sense will get a prize and the whole class will have to work their puzzle! You must also provide me with a key to the side to make sure it makes sense!
Answer reviewing concepts 1-6 (you may need to use some of your own paper.
Remember to summarize the question in the answer and use complete sentences)

12.2 Fossils: Evidence of Past Life
Define:
Fossil
Index Fossil
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1. Fossils are important components of sediment and __________________ rock.
2. Fossils are important ____________ indicators.
3. What determines the type of fossil that is formed?
4. What type of remains may not be altered at all over time?
5. What type of remains are less common to find?
6. Why do you think this is? (refer to question 3 and 4 to help)
7. What does it mean for a fossil to be petrified?
8. How is a fossil petrified?
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9. What is a fossil mold?
10. What does a fossil mold reveal? What does it not reveal?
11. What is a cast?
12. What is effective in preserving leaves and delicate animal forms?
13. _____________________ often contains abundant carbonized remains.
14. How must the fossil of an insect form?
15. What is a trace fossil? Define and give an example.
16. What are some of the oldest known fossils?

17. ____________________ are highly polished _____________ stones that were used in grinding food by some extinct _________________.
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18. What 2 conditions are important for preservation?
19. Why is each condition important?
20. Who observed the principle of fossil succession?
21. Fossil succession states that fossil organisms _____________ one another in a definite and determinable _____________.
22. Any time period can be recognized by its _____________ content.
23. List the 5 ages that have been identified.
24. _____________________ are widespread geographically, are limited to a
_____________ span of geologic time, and occur in ____________ numbers.
25. What does their presence provide?
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26. Fossils can also be used to interpret and describe
_____________________________.
27. What can you conclude from a region that contains the remains of many clam shells encased in limestone?
28. Fossils can indicate the former ___________________ of the water.
29. Give an example of how this is possible.

30. Now try this relative dating puzzle! List the letters from oldest to youngest.
31. What happened to the Earth in the location with the dotted line marked with the “?” mark?
Answer the reviewing concepts questions 1-4 (use the back and your own paper if necessary.)