RL Hanna
Geology
Historical Geology Exam 1
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you may use a ruler and a calculator (of your choosing)
you will need colored pencils
the exam is closed book
unlimited time
no scantron necessary – put all answers on these pages
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RL Hanna
Geology
The Geologic Time Scale….
Using the graph paper on the next page,
1. draw the Geologic Time Scale – to-scale…
2. In dark blue - label the Eons, Eras and Periods
3. In dark blue - label the Cenozoic Epochs
4. In green - label the dates
a. at the beginning and end of the time scale
b. at the beginning of each Eon and Era
5. In red - print all major events and “Ages of….”
6. In regular pencil - print brief descriptions of the life and conditions in each Eon
and Era. – lists are sufficient; do not use complete sentences (you won’t have
room)
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RL Hanna
Geology
The Geologic Time Scale
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RL Hanna
Geology
Radiometric Dating
Use the graph paper on the following page
7. Using your ruler, draw a general radiometric decay graph
8. Label both axes appropriately (both words and numbers)
9. Graph the points for at least 8 half-lives
10. Don’t forget to graph the starting point at t1/2 = 0
11. Using your graph, estimate how much parent material is left after XX half-lives.
12. Again, using your graph, how many half-lives must pass for XX% of the material
to decay to the daughter element?
List 4 common radiometric parent-daughter elements and estimate their half-lives.
Radiometric Parent-Daughter Elements
13. C14 decays to ?
Half-Lives
14.
15. U238 decays to ?
16.
17. Rb87 decays to ?
18.
19. K40 decays to ?
20.
21. Using your radiometric graph, and your half-lives listed above, estimate the age of
a sample with XX% K40 left.
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Geology
Radiometric Dating
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Geology
22. What is the oldest sample that can be reasonably dated with radiocarbon?
23. Why can’t trilobite fossils be dated with radiocarbon?
24. What type of rock are most fossils found in?
25. What type of rock generally provides the most accurate radiometric dating
results?
26. Which of the following should you use to get the best results for radiometric
dating of an Anasazi pottery shard?
27. Which of the following has a half-life that is “convenient” for estimating the age
of the Earth’s formation?
28. What are the ages of the oldest Earth rocks?
29. Radiometric age-dating indicates that the earth is
30. Even though no rocks have ever been found from the initial solidification of the
earth’s crust, what is used to estimate is the age of the early earth?
31. What group of fossils is the oldest known “find” of metazoans (multi-cellular
organisms)?
32. The group of fossils above included
33. Which of the following fossil assemblages indicate Paleozoic rocks?
34. Giant ammonites fossils are most commonly found in rocks of what age?
35. The earliest “bird-like” fossils with definite feathers are found in rocks of what
age?
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RL Hanna
Geology
36. The fossil record indicates that whales, dolphins, sea lions and all other sea
mammals evolved from
37. Which of the following are “living fossils”?
38. What is the common measurement error in radiocarbon dating?
(give your answer in +/- years)
39. What is the common measurement error in K-Ar dating?
(give your answer in +/- years)
40. What is the common measurement error in Rb-Sr dating?
(give your answer in +/- years)
41. Explain how a single rock layer can have trilobite fossils, ammonites and dolphin
vertebrate in it?
42. Three samples are taken from the same rock layer. One sample yields a
radiometric age of 3.7 billion years, the second sample yields a radiometric age of
2.5 million years and the third sample yields an age of 150 million years. How is
this possible?
43. A certain sandstone layer is still in its original stratigraphic orientation (has not
been tilted by plate textonics). Biostratigraphic dating indicates this sandstone
layer is progressively younger as one traverses it laterally to the east. Explain
how this can be true.
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44.
Geology
List and briefly explain how geologic processes can “contaminate” (or produce
false) radiometric age-dating results.
45. Explain cladograms.
Make up an example cladogram and explain all parts of your diagram.
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RL Hanna
Geology
46. Write a general equation which describes the fact that radiometric elements decay
such that
½ is left after one half life
¼ is left after two half lives
1 is left after three half lives
8
1 is left after four half lives
16
1 is left after five half lives
32
etc……
Define all of your terms and/or variables.
47. Using your general equation above, what fraction of parent material is left after XX
half lives? You may use your calculator but show all of your work and show what
you plug where in your equation(s).
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RL Hanna
Geology
48. Solve (or rework) your general half-life equation so that it is a general equation
which calculates the age of the sample from the fraction of parent material remaining.
You may use log base 2 or log base e.
Define all of your terms and/or variables.
49. Using your general age equation, calculate the age of a sample where XX% of the K40
parent material remains.
50. Compare your answer above to the your answer for question 21.
Which answer is more accurate? Why?
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RL Hanna
Geology
For the following questions, use the Powerpoint Slide Show HistGeolExam.
For each of the slides, identify the organism or fossil from the list provided below.
51. _____________________________
abalone
52. _____________________________
ammonite
archeopteryx
barnacles
belemnite
53. _____________________________
54. _____________________________
55. _____________________________
brachiopod
bryzoans
coccolithophores
conodont
56. _____________________________
57. _____________________________
58. _____________________________
diatoms
flat worms
foraminifera
graptolite
59. _____________________________
60. _____________________________
61. _____________________________
radioloarians
rugose coral
sand dollars
scallops
62. _____________________________
63. _____________________________
64. _____________________________
sea pen
sea urchins
stalked crinoid
stromatolites
65. _____________________________
66. _____________________________
67. _____________________________
trilobites
68. _____________________________
69. _____________________________
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Geology
The following questions refer to the last slide # 70.
70. Identify this group of organisms. ____________________
71. How old are they? _____________
72. Where were these fossils found? _____________
73. What is the significance of this group of organisms?
74. List the organisms in this group of fossils.
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Geology
75. Explain 2 ways that the age of the Earth can be determined.
76. What minerals are the most commonly tested for radiometric dating?
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