1. Geologic Time
Geologic Time Notes

3. Fossils can only be found in rocks.
SEDIMENTARY

4. Why is this statement false? “The cavemen ate dinosaur for breakfast.”
Man and dinosaurs did not live at the same time.
65 million years apart

5. Name the primary way that geologists find the absolute and relative age of rock layers.
ABSOLUTE AGE
Radioactive dating
RELATIVE AGE
Ordering rock layers

6. Use your Earth Science Reference Tables Pages 3, 8 & 9; Maybe 6 & 7
Answers Questions
Use your
Earth Science
Reference Tables
Pages 3, 8 & 9;
Maybe 6 & 7

9. Answers the Questions 1
Approximately how many million years ago did the earliest amphibians appear? 2
Approximately how many million years ago was the initial opening of the Atlantic Ocean? 3
During which era did the earliest fish appear?
Paleozoic 4
During which epoch did large carnivores appear?
Pliocene 5
Of the following rocks which would be most likely to contain fossils?
a. rhyolite b. basalt c. metaconglomerate d. limestone
limestone (it’s sedimentary) 6
At Binghamton, NY what is age of the bedrock?
Devonian ( million years) 7
How does the age of the bedrock at Old Forge compare with that at Jamestown?
Jamestown is younger 8
Name a location in NY State where you may be able to find bedrock which was formed at the peak of the eurypterid’s development.
Silurian age bedrock: Niagara Falls, Syracuse 9
Why would fossils be unlikely to be found in quartzite?
it’s metamorphic 10
For each of the following locations in NY State below, identify whether fossils would be likely or unlikely: Old Forge; Binghamton; Albany
Old Forge: unlikely
Binghamton: likely
Albany: likely

14. Do the vocabulary maps.

15. The age of an object compared to other objects.
Relative Age
The age of an object compared to other objects.
Saying one object is older than another.
Related (relative) means compared to.
Fossils,
rock layers, history

16. The actual age of an object expressed in time.
Absolute Age
How old something really is.
The actual age of an object expressed in time.
Absolutely means “fer sure.”
Fossils; history

17. Principle of Uniformitarianism
I thought of it.
Things that happen today probably happened in the past.
Copy-cat!
James Hutton
I know you are but what am I?
But I made it popular.
“The present is the key to the past.”
Charles Lyell

18. Oldest rock layers are on the bottom.
Relative Age
If a sedimentary rock outcrop has not been overturned, which layer would be the oldest?
Oldest rock layers are on the bottom.

19. Principle of Superposition
What is this principle (oldest on bottom) known as?
Principle of Superposition

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

21. On to the next question...

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

24. 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)
Not in your notes!

25. Which is older: rock layer 7 or fault ?
Why?
Rock layer 7 is cut by the fault.

26. Which is older: rock layer 12 or fault ?
Why?
Rock layer 12 is NOT cut by the fault.

27. On to the next question...

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

30. Intrusions
contact metamorphism
on all sides

31. no contact metamorphism
extrusions
no contact metamorphism
on top

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

33. H is an intrusion. Contact metamorphism on top

34. Do the vocabulary maps.

35. a part of the rock record is missing
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

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

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

38. Do the vocabulary maps.

39. What characteristics must fossils have in order to be good index fossils?
Lived over wide geographic distribution (lots of places).
Horizontally abundant
Short-lived (became extinct quickly).
Vertically limited

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

41. Evolution Organisms adapt to their environment in order to survive.
Explain the theory of evolution.
Organisms adapt to their environment in order to survive.

42. Evolution Different organisms have changed over time.
Explain how the fossil record supports this theory
Different organisms have changed over time.
99.9% of all living things are extinct.

44. Do the vocabulary maps.

45. 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

46. 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

47. Trials
Students

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

49. 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

50. 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)

51. 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
5,700 yr
11,400 yr
17,100 yr
3 half-lives x (5.7 x 103) =1.71 x 104
= 17,100 years