Chapter 8 Review
Multiple Choice
Identify the choice that best completes the statement or answers the question.
____
1. The principle that Earth’s history can be explained by current geologic processes is
a. unconformity.
c. superposition.
b. uniformitarianism.
d. evolution.
____
2. Younger layers of undisturbed sedimentary rock are above older layers according to
a. the principle of uniformitarianism.
c. law of superposition.
b. the principle of sedimentarianism.
d. angular unconformity.
____
3. The boundary between two sedimentary rock layers is called a(n)
a. crosscut plane.
c. bedding plane.
b. crosscut layer.
d. bedding layer.
____
4. The age of an object in relation to the ages of other objects is
a. absolute age.
c. relative age.
b. comparative age.
d. relational age.
____
5. A fault or body of rock is younger than any other body of rock it cuts through according to the law of
a. crosscutting relationships.
c. uniformitarianism.
b. superposition.
d. averages.
____
6. The numeric age of an object is called
a. relational age.
b. comparative age.
c. relative age.
d. absolute age.
____
7. How much sedimentary rock is deposited over 1,000 years?
a. about 3 cm
c. about 30 m
b. about 3 m
d. about 30 cm
____
8. Carbon-14 is an isotope
a. formed by radioactive decay.
b. used to date objects less than 70,000 years old.
c. used to date objects over 6,000 years old.
d. that cannot be used to date objects.
____
9. How many years of deposition are represented by a single varve?
a. three
b. two
c. one
d. The number of years cannot be measure.
____ 10. Rates of erosion are not used to date geographical features over a million years old because
a. rates of erosion are constant over a million years.
b. erosion ceases over a million years.
c. rates of erosion may greatly vary over a million years.
d. rates of erosion are constant only for about 20,000 years.
____ 11. Index fossils found in rock layers in different areas of the world indicate that the rock layers
a. formed during the same period of time.
b. formed during different periods of time.
c. are still forming.
d. never fully formed.
____ 12. Almost all fossils are discovered in
a. volcanic rock.
b. metamorphic rock.
c. igneous rock.
d. sedimentary rock.
____ 13. Amber is
a. petroleum that oozes from bogs.
b. hardened tree sap.
c. yellow rock that retains heat.
d. dried organic remains.
____ 14. A frozen organism does not decay because
a. most bacteria can’t survive freezing temperatures.
b. it is dried out.
c. it needs water to decay.
d. most bacteria survive freezing temperatures.
____ 15. Organisms that formed index fossils
a. lived during long spans of geologic time.
b. lived during short spans of geologic time.
c. were destroyed by igneous rocks.
d. were destroyed by sedimentary rocks.
____ 16. A varve is most like a(n)
a. igneous deposit.
b. fossil plant.
c. tree ring.
d. glacial lake.
____ 17. What is a coprolite?
a. fossilized fish
b. fossilized dung or waste
c. fossilized rocks
d. fossilized imprints of animals
____ 18. If an igneous intrusion is observed through a layer of sedimentary rock, what geological law applies?
a. law of superposition
c. law of crosscutting relationships
b. law of uniformitarianism
d. law of thermodynamics
____ 19. Using rates of erosion to determine the absolute age of a geologic feature is practical only for features formed
within the past
a. 2,000,000 years.
c. 10,000 to 20,000 years.
b. 100,000 to 200,000 years.
d. 10,000 years.
____ 20. Why is radioactive decay used to determine the absolute age of rocks?
a. Radioactive decay cannot be used to determine the age of a rock.
b. Radioactive decay happens very quickly.
c. Radioactive decay does not happen at a constant rate.
d. Radioactive decay happens at a relatively constant rate.
____ 21. How is radioactive decay used to determine the absolute age of rocks?
a. Parent isotopes are compared to daughter isotopes.
b. Isotopes of different compounds are compared.
c. Radioactive substances are compared to non-radioactive substances.
d. Daughter isotopes are compared to sister isotopes.
____ 22. What is a gastrolith?
a. a stone inside a fish
b. a stone that was inside a dinosaur
c. a gas that became a stone
d. fossilized waste
____ 23. Fossil imprints are
a. carbonized trace fossils.
b. carbonized isotopes of organic material.
c. carbonized impressions of plants or fish.
d. carbonized bones of animals or fish.
____ 24. Which of the following are all ways that organisms can be fossilized?
a. freezing, petrification, desiccation, amber
b. amber, petrification, mummification, freezing
c. desiccation, petrification, mummification, amber
d. mummification, desiccation, petrification, freezing
____ 25. In radiometric dating, scientists compare the proportion of a radioactive parent isotope to a stable
a. mother isotope.
c. daughter isotope.
b. sister isotope.
d. child isotope.
Completion
Complete each statement.
26. Comparing a varve to a tree, the sediment layers of the varve are like ____________________.
27. When mineral solutions replace original organic materials to create a fossil, the process is called
____________________.
Short Answer
28. Describe what causes graded bedding.
29. Explain why rates of erosion may be used to determine the absolute age of geologic features formed within
the past 10,000 to 20,000 years, but not for older features, such as the Grand Canyon.
30. Explain how the law of superposition is used to determine the age of rocks.
31. What is the law of crosscutting relationships?
32. What is an angular unconformity?
33. What does half-life mean?
34. What is the difference between a parent isotope and a daughter isotope?
35. What is the relative age of an igneous intrusion in a layer of sedimentary rock?
36. What is the principle of original horizontality?
37. What type of fossil would scientists use to get information about what ancient animals ate?
Problem
38. If the average rate of deposition is 30 cm in 1,000 years, how old would undisturbed sedimentary rock be that
was 20 m high? Show your work.
39. The rocky ledge above Niagara Falls has been eroding at the rate of about 1.3 m per year for nearly 10,000
years. At that rate, how many km will it erode in the next 5,000 years? Show your work.
40. Carbon-14 has a half-life of about 5,730 years. You have a sample of organic material that is about 6,000
years old and has 220 g of carbon-14. What was the original weight of the carbon-14 in the sample? Show
your work.