Test Bank Chapter.10 Deep Time How Old Is Old? 6th Edition - Geology Essentials 6e Complete Test Bank by Stephen Marshak. DOCX document preview.
CHAPTER 10: Deep Time: How Old Is Old?
LEARNING OBJECTIVES
10A. Explain the meaning of geologic time and the difference between relative and numerical ages.
10B. Use geologic principles (uniformitarianism, cross-cutting relations, superposition, fossil succession) to determine relative ages.
10C. Draw a sketch illustrating how unconformities form and what they represent.
10D. Explain the basis for correlating stratigraphic formations, and show how correlation led to the development of the geologic column.
10E. Illustrate the concept of a half-life, and use it to explain how geologists determine the numerical age of rocks.
10F. Describe the basis for determining dates on the geologic time scale and the age of the Earth.
MULTIPLE CHOICE
1. If the relative ages of two formations are known, what else about them can be inferred?
a. | their absolute ages |
b. | their fossil assemblages |
c. | their lithologies |
d. | their relative position in the geologic column |
2. A birthdate is an example of a(n) ________ age.
a. | relative | c. | radiocarbon |
b. | numerical | d. | isotopic |
3. Uniformitarianism is succinctly summarized by which phrase?
a. | The future is the key to the present. | c. | The past is the key to the present. |
b. | The present is the key to the past. | d. | The present is the key to the future. |
4. James Hutton, the “father of geology,” put forth the principle of
a. | superposition. | c. | original horizontality. |
b. | original continuity. | d. | uniformitarianism. |
5. As understood by modern geologists, the principle of uniformitarianism implies that
a. | the Earth has always had the same basic appearance that it has today. |
b. | igneous, metamorphic, and sedimentary rocks are uniformly mixed throughout the crust. |
c. | physical processes observed today (such as erosion and volcanic eruptions) have been active in the past at approximately the same rates. |
d. | physical processes observed today (such as erosion and volcanic eruption) occurred much more rapidly in the past, quickly sculpting the Earth’s surface. |
6. In the area immediately surrounding an igneous intrusion, a host limestone is locally metamorphosed to produce marble. Which of the following statements is correct?
a. | The intrusive igneous rock must be younger than the limestone. |
b. | The limestone must be younger than the igneous rock. |
c. | The limestone must be younger than the marble. |
d. | The relative ages of the three units cannot be determined with the information given. |
7. Within the world’s sedimentary rocks, fossils
a. | are rarely, if ever, found. | c. | occur in limited intervals of strata. |
b. | are randomly distributed. | d. | are found only in igneous rocks. |
8. Based on the figure, what is the age of Layer 7 relative to Layer 3?
a. | Layer 7 is younger than Layer 3. |
b. | Layer 7 is older than Layer 3. |
c. | Layer 7 and Layer 3 are the same rock type, so they are the same age. |
d. | Their relative ages cannot be determined. |
9. Which principle of stratigraphy could be used to determine the relative ages of Layer 7 and Layer 3?
a. | the principle of fossil succession | c. | the principle of lateral continuity |
b. | the principle of original horizontality | d. | the principle of inclusions |
10. The oldest geologic unit is
a. | Layer 1. | c. | Layer 5. |
b. | Layer 8. | d. | Layer 10. |
11. In an undisturbed sequence of sedimentary rocks, younger layers overlie older layers, according to the principle of
a. | superposition. | c. | original horizontality. |
b. | original continuity. | d. | uniformitarianism. |
12. Which of the following geologic principles is a direct result of gravity?
a. | baked contacts | c. | original horizontality |
b. | crosscutting relationships | d. | inclusions |
13. What type of age are the geologic principles described by Charles Lyell used to determine?
a. | absolute age | c. | relative age |
b. | numerical age | d. | fossil age |
14. If an igneous dike cuts across a sequence of sedimentary beds, then
a. | the beds must be older. |
b. | the dike must be older. |
c. | the beds and the dike must have formed at the same time. |
d. | their relative ages cannot be determined from the information given. |
15. If a basalt body cuts across a fault, what are the relative ages of the basalt and the fault?
a. | The fault must be older, according to the principle of crosscutting relationships. |
b. | The basalt must be older, according to the principle of crosscutting relationships. |
c. | The basalt must be older, according to the principle of original horizontality. |
d. | Their relative ages cannot be determined from the information given. |
16. Magma has intruded into a limestone and a marble rind formed surrounding the granite pluton. The marble rind must be younger than the limestone according to the principle of
a. | superposition. | c. | original horizontality. |
b. | baked contacts. | d. | lateral continuity. |
17. If a sandstone lies on top of a shale,
a. | the shale must be older, according to the principle of superposition. |
b. | the sandstone must be older, according to the principle of superposition. |
c. | the shale must be older, according to the principle of original horizontality. |
d. | their relative ages cannot be determined from the information given. |
18. The principle of ________ explains the occurrence of older rock within a newer rock.
a. | baked contacts | c. | original horizontality |
b. | crosscutting relationships | d. | inclusions |
19. Which of the following statements is true regarding the clasts (labeled 5) inside the granite pluton?
a. | The inclusions are the same age as the pluton. |
b. | The inclusions are younger than the pluton. |
c. | The inclusions are older than the pluton. |
d. | The relative age of the inclusions and the pluton cannot be determined. |
20. If the lithology and fossil content of two bodies of rock on opposite sides of a canyon are identical, then these remaining outcrops were likely physically connected at one time and formed part of an extensive, sheet-like layer of rock. This idea summarizes the principle of:
a. | superposition. | c. | original horizontality. |
b. | lateral continuity. | d. | uniformitarianism. |
21. What is the term for a boundary surface in a sequence of rock strata indicating lack of deposition, where erosion and deformation may have occurred?
a. | an unconformity | c. | a fossil succession |
b. | a fault | d. | an inclusion |
22. The surface below sedimentary rocks that overlie igneous or metamorphic rocks is termed a(n)
a. | disconformity. | c. | nonconformity. |
b. | angular unconformity. | d. | marker bed. |
23. If horizontal sedimentary strata overlie tilted strata (and no fault is present), the surface between the horizontal and tilted strata must be a(n)
a. | conformable sedimentary contact. | c. | disconformity. |
b. | angular unconformity. | d. | nonconformity. |
24. Look at the figure below. The contact between the Unkar Group and the Tapeats Sandstone is a(n)
a. | conformable contact. |
b. | disconformity. |
c. | nonconformity. |
d. | angular unconformity. |
25. Look at the figure below. The contact between the Vishnu Schist and the Tapeats Sandstone is a(n)
a. | conformable contact. | c. | nonconformity. |
b. | disconformity. | d. | angular unconformity. |
26. Look at the figure below. Notice the erosional surface on the top of the Muav Limestone. This contact between the Muav limestone and the Temple Butte Formation is an example of a(n)
a. | conformable contact. |
b. | disconformity. |
c. | nonconformity. |
d. | angular unconformity. |
27. Can the age of the Earth be reliably estimated from sediment thicknesses?
a. | Yes. Sedimentation rates remain constant at any one locality throughout the Earth’s history. |
b. | Yes. Sedimentary rocks are rarely metamorphosed or melted. |
c. | No. Sedimentary rocks make up only a small fraction of the rocks on the Earth’s surface. |
d. | No. Most of the Earth’s history is represented by unconformities between strata rather than the strata themselves. |
28. Which method of correlation is most reliable for determining age equivalence among bodies of rock that are physically separated by vast distances?
a. | lithologic correlation | c. | inclusion correlation |
b. | fossil correlation | d. | unconformity correlation |
29. Relative ages expressed on the geologic time scale primarily resulted from the study of
a. | fossil content and spatial relationships among igneous rocks. |
b. | fossil content and spatial relationships among sedimentary rocks. |
c. | radiometric dating of igneous rocks. |
d. | radiometric dating of sedimentary rocks. |
30. Which of the following is true of the geologic column?
a. | It is the complete record of the Earth’s history that is preserved in the rocks at any given location. |
b. | It portrays the spatial distribution of rock units at the Earth’s surface. |
c. | It is a composite stratigraphic column created by correlating strata from millions of locations around the world. |
d. | It is an interval of strata composed of a specific rock type or group of rock types that together can be traced over a broad region. |
31. Which of the following lists the time divisions on the geologic column from longest (most general) to shortest (most specific)?
a. | epoch, period, era, eon | c. | era, eon, epoch, period |
b. | period, epoch, eon, era | d. | eon, era, period, epoch |
32. What type of spatial representation of geologic information shows the distribution of rock units at
the Earth’s surface, their contacts, and the structures that affect them?
a. | a block diagram | c. | a geologic map |
b. | a geologic cross section | d. | a digital elevation model |
33. What type of age does the measurement of parent and daughter isotopes in a mineral determine?
a. | relative age | c. | seasonal age |
b. | numerical age | d. | fossil age |
34. Basaltic clasts within a conglomerate have been radiometrically dated to 50 million years ago. Is this a reliable age for the conglomerate?
a. | Yes. |
b. | No, this age is likely too old. |
c. | No, this age is likely too young. |
d. | No, basalt never contains minerals bearing radioactive isotopes. |
35. In an unweathered sample of igneous rock, the ratio of an unstable isotope to its stable daughter isotope is 1:15. If no daughters were present at the time the rock cooled below closure temperature, and the half-life of the isotope is 50 million years, how old is the rock?
a. | 200 million years | c. | 750 million years |
b. | 400 million years | d. | 1 billion years |
36. Referring to the graph below, after one half-life has passed, what is the ratio of parent isotopes to daughter isotopes?
a. | 16:0 | c. | 1:3 (i.e., 4:12) |
b. | 1:1 (i.e., 8:8) | d. | 1:7 (i.e., 2:14) |
37. Two atoms of a single element that differ in number of neutrons are said to represent two distinct ________ of that element.
a. | isomers | c. | isotherms |
b. | isotopes | d. | atomic species |
38. Which of the following is ALWAYS the same for different isotopes of a single element?
a. | atomic number | c. | the number of neutrons |
b. | atomic mass | d. | half-life |
39. A radiometric age for a mineral crystal within an igneous rock measures the amount of time that has passed since the
a. | atoms within the crystal were part of a body of molten magma. |
b. | crystal solidified. |
c. | temperature of the crystal became equal to surface temperatures. |
d. | temperature of the crystal became equal to the closure temperature for the mineral. |
40. How is the half-life of a radioactive parent isotope defined?
a. | the time it takes for half of the parent isotope to decay |
b. | half the time it takes for the amount of parent isotope to reach zero |
c. | the time it takes the parent isotope to go through half the decay steps necessary to produce a stable daughter isotope |
d. | half of the average rate of decay of the parent isotope |
41. Accurate radiometric dating typically requires that a rock contains a measurable amount of
a. | parent isotope atoms. | c. | either parent or daughter atoms. |
b. | daughter isotope atoms. | d. | both parent and daughter atoms. |
42. How much of a radioactive parent isotope will remain after three half-lives have passed?
a. | one-third | c. | one-eighth |
b. | three-halves | d. | one-sixth |
43. The closure temperature represents the point when
a. | a magma cools to the point where minerals begin to crystallize. |
b. | radioactive isotopes begin to decay. |
c. | atoms are no longer free to move out of a crystal lattice. |
d. | the last remaining magma crystallizes. |
44. Why is radiocarbon dating rarely applied in geological work?
a. | No substances on the Earth contain significant amounts of carbon-14. |
b. | The half-life of carbon-14 is so long that it is effectively a stable isotope. |
c. | The half-life of carbon-14 is so short that it can only be used to date materials that are less than 70,000 years old. |
d. | Carbon-14 is destroyed by the heat of magma. |
45. Dendrochronology involves dating of historic and geologic events through the study of
a. | growth layers in shells. |
b. | oxygen isotope profiles in glacial ice. |
c. | remnant magnetism in iron-rich minerals. |
d. | annual growth rings in trees. |
46. Radiometric dates applied to sedimentary rocks produce ages that
a. | are just as accurate as when the technique is applied to igneous rocks. |
b. | are too young (postdate sedimentary deposition). |
c. | are too old (predate sedimentary deposition). |
d. | represent the time the sediments became lithified. |
47. How long are the half-lives of radioisotopes commonly used to date igneous and metamorphic rocks?
a. | seconds to minutes |
b. | a few years |
c. | hundreds of millions to billions of years |
d. | hundreds to thousands of years |
48. Numerical ages for boundaries between time units on the geologic time scale primarily resulted from the study of ________, in conjunction with relative age information determined from geologic principles.
a. | fossil content and spatial relationships among igneous rocks |
b. | fossil content and spatial relationships among sedimentary rocks |
c. | radiometric dating of igneous rocks |
d. | radiometric dating of sedimentary rocks |
49. In the 1800s, Lord Kelvin estimated the age of the Earth, utilizing a number of assumptions. Which wrong assumption was the primary reason why his estimate (approximately 20 million years) was so wildly inaccurate?
a. | that the Earth was once hotter than it presently is today |
b. | that the Earth may have been molten when first formed |
c. | that no new heat has been added to the Earth since its initial formation |
d. | that the Earth would lose heat over time through radiation into outer space |
50. Which statement best summarizes the development of the geologic time scale?
a. | Numerical ages for rocks were known before the relative sequence of sedimentary layers was established. |
b. | Relative ages for sedimentary strata were known before accurate numerical dates for these rocks were measured. |
c. | Names of relative ages (such as Silurian) and accurate numerical dates for these ages became known at about the same time. |
d. | Numerical ages for fossils were known before the relative sequence of sedimentary layers was established. |
1. What is the principle of uniformitarianism? How does this principle apply to our understanding of the Earth system? How is this useful in the context of relative dating?
2. How is a relative age different from a numerical age? How is each of these determined?
3. Place the layers and geologic events in order from oldest to youngest. Make sure to include all of the layers and events, including the top surface. (There will be one event/layer per line when complete.)
Youngest | |
Oldest |
Youngest | Erosion of land surface |
Intrusion of basalt dike | |
Faulting | |
Intrusion of granite pluton | |
Folding | |
Intrusion of sill | |
Sandstone 7 | |
Shale 6 | |
Sandstone 5 | |
Shale 4 | |
Sandstone 3 | |
Shale 2 | |
Oldest | Limestone 1 |
4. Describe the plausible geologic history of the rocks in the following photo/diagram.
5. What is an unconformity? Describe the three types of unconformities.
6. Compare and contrast lithologic correlation and fossil correlation. In what circumstance is each most useful? Provide an example of each.
7. Correlate the layers in the following three stratigraphic columns by drawing lines from the top and bottom of matching formations. What is the oldest sedimentary rock unit in this region? The youngest unit?
8. Discuss what the numerical age represents when a basalt, a gneiss, and a sandstone are dated using radiometric techniques.
9. Your friend the archaeologist, who studies the ancient human past, has asked you to find a numerical date for some hominid artifacts found buried by ash from a volcanic eruption. To do this, you can use carbon-14 dating, which has a half-life of 5,730 years, or uranium-238, which has a half-life of
4.5 billion years. Based on their half-lives, which isotopic dating system will give your friend the most accurate numerical age? Explain.
10. Why have no rocks older than 4.03 Ga been found in the Earth’s crust?