1. Geologic Time Notes Page 3
©Mark Place,

2. Fossils can only be found in rocks.
sedimentary

3. On to the next question...

4. never lived at the same time
Why is this statement false: “The caveman had dinosaur for breakfast.”?
man and dinosaurs
never lived at the same time

5. Answers to Questions on Page 3
On to page 4....

6. Relative Age
If a sedimentary rock outcrop has not been overturned, which layer would be the oldest? What is this principle known as?

7. oldest rock layers are on bottom Principle of Superposition

8. Using this principle, label the strata below from oldest to youngest.

9. On to the next question...

10. Faults are always (older, younger) than the rocks they cut through.

11. there first (it's older)
Which is older:
F or S
How do you know?
F cuts through S
S must have been
there first (it's older)

12. On to the next question...

13. If a geologist finds an igneous sill, how can she determine if the sill is an intrusion or an extrusion?

14. contact metamorphism on all sides
Intrusions
contact metamorphism on all sides

15. no contact metamorphism on top
extrusions
no contact metamorphism on top

16. Is “H” an intrusion or extrusion? How can you tell?

17. H is an intrusion. Contact metamorphism on top

18. On to the next question...

19. a buried erosional surface
What is an unconformity?
a buried erosional surface
How does it complicate the relative dating of rock layers?
a part of the rock record
is missing

20. weathering and erosion
What processes could lead to an unconformity?
weathering and erosion

21. Using the diagram to the left, identify where the unconformity is located by drawing an arrow and writing the word “unconformity” next to it.

22. On to the next question...

23. What characteristics must fossils have in order to be good index fossils?
lived over a large geographic area (large horizontal distribution)
lived for a short period of time (small vertical distribution)

24. In geology, this is referred to as CORRELATION
In the diagram below, a geologist has matched up rock layers based on index fossils.

25. On to the next question...

26. Evolution organisms adapt to their environment in order to survive
Explain the theory of evolution.
organisms adapt to their environment
in order to survive

27. Evolution can see that different organisms have changed over time
Explain how the fossil record supports this theory
can see that different organisms have
changed over time

28. their half-lives are constant
Absolute Age
Why are radioactive isotopes useful in
determining the absolute age of a rock?
their half-lives are constant

29. NOTHING! it is reliable to calculate age
Absolute Age
What can be done to change the
half-life of a radioactive isotope?
Why is this important?
NOTHING!
it is reliable to calculate age

30. stable atoms unstable atoms Draw the generic graph for the
half-life of a radioactive isotope.
stable atoms
unstable atoms

31. carbon-14 What radioactive isotope could be
Absolute Age
What radioactive isotope could be
used to determine the absolute
age of material that was recently living?
carbon-14

32. What is the half life of uranium-238?
Please answer the two questions
on page 7 of your Notes
What is the half life of uranium-238?
4.5 x 109
4,500,000,000
4.5 billion years
choice (c)

33. 3 half-lives x (5.7 x 103) =1.71 x 104 = 17,100 years
Please answer the two questions
on page 7 of your Notes
If there is a 100g sample of C14, how many grams of
C14 would remain after three half-lives?
How long would this take? Show all work.
100g 
50g 
25g 
12.5g
3 half-lives x (5.7 x 103) =1.71 x 104
= 17,100 years