Test 2 Review
MATCHING: Match the correct definition to the term.
_____ 1. relative age
_____ 2. absolute age
_____ 3. radiometric dating
_____ 4. half-life
_____ 5. carbon dating
A. using radioactive carbon-14 to determine the absolute age of rocks or fossils
B. length of time it takes half of a radioactive isotope to decay
C. estimated age of rock determined by comparing it to other rocks
D. the exact age of a rock
E. use of radioactive decay to measure absolute age
MULTIPLE CHOICE: Choose the best answer that completes each statement.
6. The principle that Earth’s history can be explained by studying current geologic processes is
A. uniformitarianism. B. superposition C. Evolution
7. The order of rock layers reveals
a. the type of rock in the layers.
b. periods of volcanic activity.
c. the relative age of the layers.
d. the exact years in which each layer formed
8. Younger layers of sedimentary rock are above older layers according to
A. the principle of uniformitarianism. B. Unconformities C. Law of Superpostion
9. Which of the following methods is NOT used to determine absolute age?
a. The rate at which a stream erodes
b. Recording which layer of rock is on top of other layers.
c. Determining how much radioactive isotope has decayed.
10. An absolute age can be determined by counting varves, which are
a. layers of sediment deposited annually.
b. the chemicals that make up rocks.
c. irregular patterns in rock.
11. Radioactive isotopes emit particle and energy (decay)
a. at differing rates regardless of surrounding conditions.
b. at differing rates depending on surrounding conditions.
c. at a constant rate regardless of surrounding conditions.
d. at a constant rate if conditions remain the same.
SHORT ANSWER: Answer the following questions in the space provide. Use complete sentences.
12. What did James Hutton contribute to our understanding of the Earth?
13. Describe how sedimentary rock forms.
14. Explain how the law of superposition can be used to determine the relative age of sedimentary rocks.
15. Summarize why calculations of absolute age based on rates of erosion and deposition can be incorrect.
16. Explain how radiometric dating is used to estimate absolute age.
17. Label the layers of the Earth. Label the youngest layer #1, second youngest #2, etc. through #12.
18. The clam shell is ______than the bone.
19. The footprints are ______than the fish.
20. The oldest fossils are in the ______layer.
21. The youngest fossils are in the ______layer.
22. Questions 11 and 12 describe the law of ______.
radiometric dating: Answer the following questions about radioactive isotopes.
23. What do you call the original radioactive isotope? ______
24. What do you call the newly formed stable isotope? ______
25. Label the lines in the graph using your answers
from questions 1 and 2.
26. Complete the next 2 boxes and indicate the time above them.
27. What is the half-life of the element pictured in number 5? ______
28. If you have 20g at 6 minutes, how much did you start with?______
29. What is the half-life of Carbon-14? ______
30. If you start with 800g of Carbon-14, how much will remain after 2 half-lives? ______
31. Carbon-14 would be a good method for dating materials of what age? ______
32. Another fossil originally contained 100,000 Potassium-40 atoms and it now contains only 12,500. How old is this fossil? ______
33. Suppose you have a shark’s tooth that you suspect is about 15,000 years old. Would you use U-238 or C-14 to date the tooth? Explain your answer.
34. Explain why scientists used these different radioactive isotopes to determine the age of rocks and fossils. Why don’t they always use Carbon-14?
interpreting observations: Read the following passage and answer the questions below.
Hominids are extinct, human-like creatures that pre-date modern humans. Some of the oldest known hominid fossils have been found at Olduvai Gorge in Tanzania. The gorge is a 15-mile long eroded canyon, 328 feet deep, with undisturbed layers of sediment and rock that geologists can date back nearly 2 million years. The remains of at least 48 hominids have been found at Olduvai Gorge.
But 30 miles south of Olduvai Gorge, at Laetoli, hominid bones have been found that date to about 3.5 million years ago, and 59 footprints preserved in a volcanic ash layer have been found nearby. From the footprints, scientists have assumed that the hominids walked upright like modern humans, and that the adults were under 5 feet tall.
35. What are hominids?
36. Could scientists use carbon dating to determine the age of early hominids? Explain.
37. How would scientists have found the relative age of the fossil bones found at Olduvai Gorge?
38. How do you think scientists determined the height of the hominids?
MATCHING: Match the correct definition to the term.
_____ 39. Fossils
_____ 40. paleontology
_____ 41. Sedimentary rock
_____ 42. gastrolith
A. Fossils are most often found in this material
C. Fossilized stones from a dinosaur’s digestive system.
D. The remains of animals or plants that lived long ago.
E. The scientific study of fossils.
MULTIPLE CHOICE: Choose the best answer that completes each statement.
43. Fossils provide clues to
a. past weather, cloud cover, and changes in seasons.
b. past geologic events, climates, and evolution of living things.
c. recent events in human history.
44. In general, what parts of organisms become fossils?
e. all parts are equally likely to be fossilized
f. only very hard woods
g. soft parts, such as skin and organs
h. hard parts, such as wood, bones, shell, or teeth
45. Tar seeps are formed by thick deposits of
a. clay.
b. petroleum.
c. amber.
d. silica.
46. An imprint shows
a. the surface features of an organism.
b. internal details of an organism.
c. an exact, complete form of an organism.
d. the soft portions of an organism.
47. Which type of fossil is formed when mud fills a mold and hardens?
a. Imprint
b. Coprolite
c. cast
d. mold
48. What type of fossil give scientists clues about what ancient animals ate?
a. Imprint
b. Coprolite
c. cast
d. mold
49. Scientists study trace fossils to find
d. exactly what an animals looked like.
e. precisely what an animal weighed.
f. clues to an animal’s appearance and activities.
50. Scientists use index fossils to
e. determine the relative ages of rock layers.
f. determine the absolute ages of rock layers.
g. determine branches of the development of species.
SHORT ANSWER: Answer the following questions in the space provide.
51. Do most dead plants and animals become fossils? Why or why not?
52. How can a scientist tell if an area of land was once covered by an ocean?
53. How are insects preserved in amber?
54. What about tar seeps led fossilized animals to become trapped in the sticky tar?
55. List the features that a fossil must have to be used as an index fossil.
56. Use arrows to show which rock layers are the same age.
57. Explain how you knew which rock layers were the same ages.
58. Label the oldest and youngest layers.
59. What are the 4 Era of Earth’s history? Put them in order from oldest to youngest. Briefly describe the events of each era.
MATCHING: Match the Event with each Era. Each term will be used more than once.
A. Precambrian Time
B. Paleozoic Era
C. Mesozoic Era
D. Cenozoic Era
_____ 60. Our current time period.
_____ 61. The Earth formed.
_____ 62. 251 million years ago to 65 million years ago.
_____ 63. One of the first living things, algae, appears on Earth.
_____ 64. The age of the dinosaurs and reptiles.
_____ 65. The Permian mass extinction ended this era.
_____ 66. The age of mammals.
_____ 67. Dinosaurs went extinct at the end of this era.
_____ 68. Most of Earth’s past is during this time period.
_____60. The supercontinent Pangea formed.
SHORT ANSWER: Answer the following questions in the space provided.
70. What is the geologic time scale?
71. What is Pangea? When did it form? When did it break up?
72. What evidence is there for Pangea?
73. What is mass extinction?
74. How can extinctions be beneficial?
Match each type of mass extinction to its description.
A. Gradualist Theory B. Impact Theory C. Volcano Theory
______75. Asteroid hit Earth about 6.5 million years ago.
______76. Climate changes like heating or cooling drastically changed the environment.
______77. Created huge craters and brought the mineral iridium to Earth.
______78. Caused Earth to be covered with lava and the air to be filled with dust and gases.
______79. Could have caused acid rain and the depletion of the ozone layer.
80. What does this graph show?