Chapter 7

A rock that is ________ million years old comes from the Archean Eon. A) 4,060 B) 30 C) 500 D) 1,500

A) 4,060

What percentage of the 339 natural isotopes are unstable? A) 99.9 B) 10.0 C) 50.6 D) 20.6

D) 20.6

Which event does not occur during the decay of potassium-40 isotopes? A) An electron orbiting near the nucleus enters into the nucleus and combines with a proton to produce a neutron. B) Electrons rearrange, producing x-rays. C) A neutron changes to a proton and emits an electron. D) A proton is ejected from the nucleus.

D) A proton is ejected from the nucleus.

A rock that is 400 million years old comes from the ________ Period. A) Paleozoic B) Phanerozoic C) Precambrian D) Silurian

D) Silurian

A rock that is 20 million years old comes from the ________ Epoch. A) Miocene B) Cretaceous C) Jurassic D) Paleocene

A) Miocene

The oldest dated minerals on Earth are ________ years old. A) 4.03 billion B) 542 million C) 4.4 billion D) 4.56 billion

C) 4.4 billion

A uranium-lead age determined from a zircon crystal removed from a sandstone would reflect the time elapsed since the ________ of the zircon. A) erosion B) deposition C) crystallization D) cementation

C) crystallization

What was a reason that Lord Kelvin wrong? A) He was a bit off on his calculations. B) He was actually correct. C) He based his estimation on the literal interpretation of the Bible. D) He assumed that Earth only cools by conduction.

D) He assumed that Earth only cools by conduction.

Where have the oldest dated sand grains been found on Earth? A) Australia B) Canada C) The United States D) Africa

A) Australia

Which radioactive-isotope-decay schemes would be optimal for determining the age of wood and bone? A) Carbon 14 method B) Potassium Argon method C) Uranium Lead method D) Rubidium Strontium method

A) Carbon 14 method

Why is potassium-argon dating least useful for sedimentary rock? A) Sedimentary rocks are too rare. B) Sedimentary rocks cannot be dated. C) Metamorphic and igneous rocks outnumber sedimentary rocks. D) Sedimentary rocks don't often contain potassium.

D) Sedimentary rocks don't often contain potassium.

Which mineral does not contain abundant potassium? A) feldspar B) biotite C) muscovite D) calcite

D) calcite

Metamorphism usually ________ the radioactive-isotope clock. A) retains B) preserves C) maintains D) resets

D) resets

True or False: Only sedimentary rocks can be assigned to geologic periods because they are the only rocks that contain fossils.

FALSE

True or False: Each radioactive-decay scheme has its own time range of usefulness depending on the size of the half-life.

TRUE

Why is the decay of potassium to argon used instead of the decay of potassium to calcium? A) Calcium is prevalent in too many rocks. B) Argon stays in the rock for a longer period of time so it is a more reliable measurement. C) Calcium dissolves in water so cannot be measured accurately. D) Argon is a reactive element and will only be present due to the decay of the potassium isotope.

A) Calcium is prevalent in too many rocks.

A rock that is 90 million years old comes from the ________ Period. A) Cretaceous B) Mesozoic C) Phanerozoic D) Jurassic

A) Cretaceous

Why does a potassium-argon dating time scale reset during heating? A) Expansion of the crystal structure may permit the loosely caged argon atoms to escape. B) Reduction of the crystal structure may permit the loosely caged argon atoms to escape. C) It gets so hot that it throws off the time scale. D) This does not happen.

A) Expansion of the crystal structure may permit the loosely caged argon atoms to escape.

Which statement is not true about the principle of faunal succession? A) Fossils that appear at different places and over different eras are of different species. B) Fossils of different organisms first appear at different times. C) Fossils of related organisms change in the same fashion in progressively younger rocks every place they occur. D) Fossil species disappear from the rock record everywhere when they become extinct and do not reappear in younger rocks.

A) Fossils that appear at different places and over different eras are of different species.

Why was Irish Bishop James Ussher so far off about the age of Earth? A) He based his estimation on the literal interpretation of the Bible. B) He was a bit off on his calculations. C) He did not account for the fact that Earth cools in more ways than just one. D) He was correct.

A) He based his estimation on the literal interpretation of the Bible.

When Carbon 14 decays, the product is A) Nitrogen 14. B) Aluminum 13. C) Carbon 12. D) Carbon 13.

A) Nitrogen 14.

The principle that states that sediment tends to be deposited in horizontal layers is the Principle of ... A) Original Horizontality. B) Inclusions. C) Superposition. D) Cross-cutting relationships.

A) Original Horizontality.

A student concluded, "The rock record is incomplete because of weathering and erosion." Evaluate this statement. A) The statement is true. B) The statement is partially true; the student forgot to include metamorphism. C) The statement is partially true; the student forgot to include tectonic forces. D) The statement is partially true; the student forgot to include soft-shelled animals that are now extinct and not fossilized.

A) The statement is true. Answer: A Skill: Evaluation Objective: 7.5

A comparison of ages calculated by carbon-14 analysis with ages known by other means results in A) a match of the ages, within known uncertainties. B) the calculated ages being older. C) the known ages being older. D) some calculated ages being younger and some older.

A) a match of the ages, within known uncertainties.

Which feature separates an overlayer of volcanic rock from underlying metamorphic rocks? A) a nonconformity B) a disconformity C) an angular unconformity D) an unconformity

A) a nonconformity

What is the most common way to name a geologic period? A) by the name of the place where rocks of that period were first described B) by the name of the tectonic continent that existed at that time C) by the name of the scientist who first defined that period D) by the name of the metamorphic processes that were occurring at that time

A) by the name of the place where rocks of that period were first described

Choose the option that orders the measurement of time from shortest to longest. A) epoch, period, era, eon B) era, epoch, eon, period C) period, epoch, era, eon D) epoch, period, eon, era

A) epoch, period, era, eon

Plutonic rocks record which part of Earth's history? A) interior B) surface C) future D) core

A) interior

Which principle is described below? "Objects enclosed in rock must be older than the time of rock formation." A) the principle of inclusions B) the principle of superposition C) the principle of cross-cutting relationships D) the principle of original horizontality

A) the principle of inclusions

What did the author of the following quote mean? "The result, therefore, of our present enquiry is, that we find no vestige of a beginning -- no prospect of an end." A) James Hutton had postulated the age of the Earth, and it was considerably older than most scientists imagined. B) Unconformities, nonconformities, and the slow rate of erosion defined Earth as much older than religious leaders and scientists of the time believed. C) The water cycle had a much greater scope and a capacity of hidden water than scientists had imagined. D) Rocks had been transforming through the rock cycle for billions of years and could be expected to continue to do so for billions of years more.

B) Unconformities, nonconformities, and the slow rate of erosion defined Earth as much older than religious leaders and scientists of the time believed.

Choose the option that correctly arranges the steps involved in the formation of a nonconformity. 1. Metamorphic and plutonic rocks form below the surface. 2. Sedimentary rock is deposited on the eroded surface. 3. Erosion removes overlying rock. A) 1, 2, 3 B) 1, 3, 2 C) 2, 1, 3 D) 3, 1, 2

B) 1, 3, 2 Skill: Analysis Objective: 7.5

How are disconformities different from uncomformities? A) They are the same. B) A disconformity has uniformly layered sediments whereas an uncomformity has horizontal layers with angular beneath or above. C) A disconformity has horizontal layers with angular beneath or above whereas an unconformity has uniformly layered sediments. D) A discomformity is older than an unconformity.

B) A disconformity has uniformly layered sediments whereas an uncomformity has horizontal layers with angular beneath or above. Skill: Knowledge Objective: 7.5

The determination that a granite pluton is not intrusive into overlying sedimentary layers because there are pebbles of granite in the bottom-most layer is an application of the Principle of A) Superposition. B) Inclusions. C) Cross-cutting relationships. D) Original Horizontality.

B) Inclusions.

A rock that is 200 million years old comes from the ________ Era. A) Cenozoic B) Mesozoic C) Paleozoic D) Jurassic/Triassic

B) Mesozoic

How are the principles of lateral continuity and superposition related? A) They help to understand the processes that obstructs sedimentary layers. B) They help to extend relative age relationships over larger areas. C) They help to understand cross-cutting relationships. D) They help to show that sediment tends to accumulate in horizontal layers.

B) They help to extend relative age relationships over larger areas.

A student commented, "A metamorphic rock must have a greater relative age than a sedimentary rock." Is the student using the term "relative age" here in the correct context, and why or why not? A) No. Relative age must compare the age of at least three things. B) Yes. The ages of the rocks are ordered in relation to each other. C) No. Relative age should state a specific number of years in which the event occurred. D) Yes, the term is used in the correct context, however knowing how long ago these types of rocks formed would be useful.

B) Yes. The ages of the rocks are ordered in relation to each other.

Geologists know that radioactive dating methods are valid A) because they are consistent with proposed theories. B) because they have been compared with dates determined by other methods and have been found to correlate well. C) because they have been compared with dates determined by other methods and have the same exact dates. D) because the instruments always work well when performing laboratory tests.

B) because they have been compared with dates determined by other methods and have been found to correlate well.

Name two features defined by the principle of cross-cutting relationships. A) convergent tectonic plates and faults B) faults and dikes C) dikes and sills D) convergent tectonic plates and sills

B) faults and dikes

What additional evidence did William Smith utilize to make his correlations? A) fossils in different layers in the same mine B) fossils in the same layers in different mines C) chemical composition of coal seams in different mines D) chemical compositions of rock layers in the same mine

B) fossils in the same layers in different mines

Atoms that have the same number of protons and different numbers of neutrons are called A) radioactive. B) isotopes. C) electrons. D) carbon atoms.

B) isotopes.

The two keys to determining the absolute age of a rock are A) measuring the abundance of parent isotope and measuring the abundance of daughter isotope. B) knowing the half-life and measuring the abundance of parent and daughter isotopes. C) knowing the composition and the geologic period the rock is from. D) identifying all the minerals in the rock and knowing the half-life of each mineral.

B) knowing the half-life and measuring the abundance of parent and daughter isotopes.

According to radioactive dating, which celestial object is the oldest? A) Earth B) meteorites C) the Moon D) Jupiter

B) meteorites

What are radioactive decay rates in minerals affected by? A) temperature and pressure B) nothing C) variations in gravity and magnetism D) heat

B) nothing

What does a radioactive-isotope aging test on a rock determine? A) the age of the rock since metamorphism B) the date of formation of the rock-forming minerals C) the length of time the rock has existed in its location D) the age of the rock since sedimentation

B) the date of formation of the rock-forming minerals

Which principle is a geologist applying when deciding that a fossil in a mud layer is older than a fossil in a sandstone layer above it? A) the principle of inclusions B) the principle of superposition C) the principle of cross-cutting relationships D) the principle of original horizontality

B) the principle of superposition

If a person found a fossil and presented it to William Smith, what would the scientist be able to conclude about that fossil? A) which type of animal it was and where it had lived B) which layer the fossil had come from and where that layer was exposed C) where the fossil was found and what type of animal it was D) when the animal had lived and which layer it had come from

B) which layer the fossil had come from and where that layer was exposed

Which isotope is the least stable? A) Carbon 12 B) Carbon 13 C) Carbon 14 D) Nitrogen 14

C) Carbon 14

The principle that states that geologic features that cut across rocks must form after the rocks that they cut through is the Principle of ... A) Inclusions. B) Superposition. C) Cross-cutting relationships. D) Original Horizontality.

C) Cross-cutting relationships.

How did William Smith produce a complete picture of the layers in a deep section of local rocks when the layer was not actually exposed in any one place? A) He made inferences based upon his observations and knowledge of a complete section of exposed rock 150 km away. B) He utilized the chemical compositions of rocks that were brought up by a well-driller's core sampler. C) He drew correlations between different parts of the deep section that were exposed in nearby locations. D) He applied his knowledge of the past history of the local geology and matched up the fossils.

C) He drew correlations between different parts of the deep section that were exposed in nearby locations.

In the following quote, who and what was James Huxley criticizing? "Mathematics may be compared to a mill of exquisite workmanship, which grinds you stuff of any degree of fineness; but nevertheless, what you get out depends on what you put in. . . so pages of formulae will not get a definite result of loose data." A) He thought that Hutton's time scale, based on sedimentation, was too slow. B) He thought that Earth's age, as calculated from biblical stories, was too young. C) He thought that William Thomson's heat-based model was inaccurate. D) He thought that John Joly's salty water calculations were too fastidious.

C) He thought that William Thomson's heat-based model was inaccurate.

What results from instability in an atom? A) Instability results in the implosion of the element. B) Instability results in the explosion of the element. C) Instability causes a transformation of an unstable isotope to a stable one by changing the number of protons, neutrons, or both. D) Instability causes a transformation of an unstable isotope by ridding itself of a certain amount of electrons.

C) Instability causes a transformation of an unstable isotope to a stable one by changing the number of protons, neutrons, or both.

Which statement about John Joly's salty ocean theory to calculate Earth's age is false? A) John Joly's theory gives a more accurate estimate of Earth's age now that more accurate observational data is available. B) Joly believed that the ocean began as a salty body of water and that salt entered it from rock sources at a steady rate. C) Joly's method was less accurate than Kelvin's. D) Joly underestimated the amount of precipitated rock salt in the world.

C) Joly's method was less accurate than Kelvin's.

A rock that is 50 million years old comes from the ________ Period. A) Phanerozoic B) Cenozoic C) Paleogene D) Eocene

C) Paleogene

A rock that is 300 million years old comes from the ________ Era. A) Cenozoic B) Mesozoic C) Paleozoic D) Permian

C) Paleozoic

How does the structure of a nonconformity show geologists that there was a lapse in the record of time? A) Carbon-dating radioactive tests on the rocks shows that a lapse in time occurred. B) The coal seam between layers must have taken millions of years to form. C) Rock must have eroded away because the metamorphic or igneous rocks underneath were formed at great depth, not near the surface. D) The fossil record shows missing specimens.

C) Rock must have eroded away because the metamorphic or igneous rocks underneath were formed at great depth, not near the surface. Skill: Analysis Objective: 7.5

A rock that is 20 million years old comes from the ________ Period. A) Miocene B) Paleogene C) Tertiary D) Paleocene

C) Tertiary

How can the age of a sample be determined from a graph of daughter and parent atoms versus time? A) The y-intercept will show the amount of sample present in a certain mass. B) The intersection of the daughter and parent atom lines will show the age. C) The ratio of daughter to parent atoms will show the age. D) The slope can be interpreted to find the age. Answer: C

C) The ratio of daughter to parent atoms will show the age.

What observable data would not help a scientist piece together the layers of rock according to the principle of lateral continuity? A) core samples from a drilled well B) a view of a cliff exposed by blasting a train track through it C) an adjacent igneous mountain D) a view of layers exposed in a river valley

C) an adjacent igneous mountain

How did the science community piece together the relative time scale of rocks in the nineteenth century? A) through the discovery of plate tectonics B) from the study of ancient ocean environments C) from the study of fossil-bearing rocks D) through the discovery of active volcanoes

C) from the study of fossil-bearing rocks

Sedimentary rocks do not record A) the tectonic history of Earth over time. B) organisms that lived in the past. C) metamorphic processes that have occurred over time. D) regional climate changes.

C) metamorphic processes that have occurred over time.

A geologist observing a break in a rock formation consisting of sedimentary layers concludes that the layers were displaced as a result of fault movement. Which principle is described here? A) the principle of inclusions B) the principle of superposition C) the principle of cross-cutting relationships D) the principle of original horizontality

C) the principle of cross-cutting relationships

An angular unconformity does not record A) the order of layers in the upper section. B) the order of layers in the bottom, tilted section. C) the time that passed during erosion and tilting. D) fossils.

C) the time that passed during erosion and tilting. Skill: Knowledge Objective: 7.5

A rock that is 375 million years old comes from the ________ Period. A) Tertiary B) Permian C) Cretaceous D) Devonian

D) Devonian

What was wrong with Benoit de Maillet's method of determining the age of Earth? A) He did not use the scientific method and instead made guesses. B) He based his theories on personal observations without taking into account actual evidence. C) His measuring instruments were of poor quality so he could not collect accurate data. D) He studied the knowledge and assumptions of the scientists of his time and before.

D) He studied the knowledge and assumptions of the scientists of his time and before. Skill: Evaluation Objective: 7.6

A rock that is 2,000 million years old comes from the ________ Era. A) Phanerozoic B) Paleozoic C) Proterozoic D) Paleoproterozoic

D) Paleoproterozoic

Which was not an incorrect assumption or estimated value made by geology professor John Joly to determine the 80 to 100 million year age of Earth based on the salinity of the oceans? A) The salt content of river water through time. B) The volume of the ocean. C) The amount of ancient rock salt. D) The salinity of seawater.

D) The salinity of seawater.

What evidence might suggest a time interval between two rock layers? A) a metamorphosed band in the bottom layer B) a metamorphosed band in the top layer C) a coal layer between the two layers D) an irregular boundary between the two layers

D) an irregular boundary between the two layers

Radioactive dating is used to determine the age of fossil-bearing sedimentary beds A) by comparing the fossils to known fossils in other areas. B) by using carbon dating on the sedimentary rock. C) by using potassium-argon dating on the sedimentary rock. D) by dating adjacent metamorphic or volcanic layers.

D) by dating adjacent metamorphic or volcanic layers.

What evidence would lead geologists to conclude that granite underlying sedimentary rock is younger than the sedimentary rock? A) fragments of sedimentary rock included in the granite B) pebbles of the granite included in the bedding of the sedimentary rock C) tilting of the sedimentary bedding D) contact metamorphism between the granite and the deepest sedimentary bedding

D) contact metamorphism between the granite and the deepest sedimentary bedding

Due to rock cycle processes, finding old rocks by radioactive methods is difficult. What is the age of the oldest single rock found on Earth to date? A) more than 2 billion years B) more than 2.5 billion years C) more than 3 billion years D) more than 4 billion years

D) more than 4 billion years

In order to use a radioactive-decay scheme to calculate the age of a mineral all of the following conditions must be met except A) the half-life must be known. B) no daughter isotope present prior to the start of parental decay or the amount of daughter can be determined. C) no parent or daughter isotopes can be gained or lost from the mineral once decay starts. D) only one radioactive isotope can exist in the rock so that cross-decay doesn't occur.

D) only one radioactive isotope can exist in the rock so that cross-decay doesn't occur.

What evidence would lead geologists to conclude that granite underlying sedimentary rock is older than the sedimentary rock? A) contact metamorphism between the granite and the deepest sedimentary bedding B) fragments of the sedimentary rock included in the granite C) completely horizontal bedding of the sedimentary rock D) pebbles of the granite included in the bedding of the sedimentary rock

D) pebbles of the granite included in the bedding of the sedimentary rock

While looking at a cliff, you observe that three visible layers of rocks are tilted about 30 degrees. There are four straight horizontal layers above the tilted layers. Which two principles suggest that the tilted layers are older than the horizontal layers? A) the principle of inclusions and the principle of original horizontality B) the principle of superposition and the principle of inclusions C) the principle of cross-cutting relationships and the principle of superposition D) the principle of original horizontality and the principle of superposition

D) the principle of original horizontality and the principle of superposition

How did the science community piece together the absolute ages of rocks in the last half of the twentieth century? A) based on where the rock is found, scientists know exactly how old the rock is B) based on the type of rock, scientists know exactly how old it is C) they never did D) through the measurement of radioactive decay

D) through the measurement of radioactive decay

If daughter isotopes are lost from a mineral after radioactive decay begins the calculated age of the mineral in questions will be A) correct. B) no age can be calculated. C) too old. D) too young.

D) too young.

What did William Smith correlate while researching coal mines in Britain? A) fossils in different layers in the same mine B) fossils in the same layers in different mines C) composition of coal seams in different mines D) types of rock layers in different mines

D) types of rock layers in different mines

True or False: A characteristic number of neutrons defines each element.

FALSE

True or False: Gaps in the rock record are of no importance to geologists because no rocks exist from the gap to be studied.

FALSE

True or False: Revisions of the absolute ages of the geologic time-scale boundaries exposes flaws inherent to the geologic time-scale.

FALSE

True or False: The fact that the seafloor, riverbeds and other depositional surfaces are not perfectly flat violates the Principle of Original Horizontality.

FALSE

True or False: The major problem with geologic correlations is that some unconformities extend around the entire planet.

FALSE

True or False: Radioactive decay permits geologists to determine the age of some minerals.

TRUE