Deck 12: Deep Time: How Old Is Old

Question 1

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,with the distributions of ocean basins and continents identical to what we see today
B)igneous,metamorphic,and sedimentary rocks are uniformly mixed throughout the crust of the Earth
C)physical processes observed today (such as erosion and volcanic eruption)have been active in the past and are responsible for the geologic history we see preserved in the rock record
D)physical processes observed today (such as erosion and volcanic eruption)have been occurring throughout Earth history at constant rates;for example,no eruption in geologic time would have been greater than the 1815 Tambora eruption

Answer 1

C

Question 2

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

Answer 2

B

Question 3

Uniformitarianism is succinctly summarized by which phrase?

A)The future is the key to the present.
B)The present is the key to the past.
C)The past is the key to the present.
D)The present is the key to the future.

Answer 3

B

Question 4

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

Question 5

Period names on the geologic time scale,such as Devonian and Permian,provide examples of ____________.

A)relative age
B)numerical age

Question 6

James Hutton,the "father of geology," put forth the principle of ____________.

A)superposition
B)original continuity
C)original horizontality
D)uniformitarianism

Question 7

Which method of correlation is more reliable for determining age equivalence among bodies of rock that are physically isolated by vast distances?

A)lithologic correlation
B)fossil correlation

Question 8

Which of the following geologic principles is a direct result of gravity?

A)baked contacts
B)cross-cutting relationships
C)original horizontality
D)inclusions

Question 9

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
B)original continuity
C)original horizontality
D)uniformitarianism

Question 10

The marble rind surrounding the granite pluton must be younger than the limestone according to the principle of ____________.

A)superposition
B)baked contacts
C)original horizontality
D)original continuity

Question 11

Concerning the relative ages of the shale and sandstone,the ____________.

A)shale must be older,according to the principle of superposition
B)sandstone must be older,according to the principle of superposition
C)shale must be older,according to the principle of components
D)Their relative ages cannot be determined from the information given.

Question 12

In a undisturbed sequence of sedimentary rocks,younger layers overlay older layers,according to the principle of ____________.

A)superposition
B)original continuity
C)original horizontality
D)uniformitarianism

Question 13

If the numerical ages of two formations are known,then the relative age of each with respect to one another can be inferred.

Question 14

The basalt body is best described as a ____________.

A)pluton
B)sill
C)dike
D)laccolith

Question 15

Which eon of geologic time is represented by rocks containing abundant shelly fossils?

A)Archean
B)Phanerozoic
C)Proterozoic

Question 16

Within the world's sedimentary rocks,fossils ____________.

A)are rarely,if ever,found
B)are randomly distributed
C)occur in an ordered sequence

Question 17

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 older than the limestone.
B)The limestone must be older than the marble.
C)The marble must be older than the intrusive rock.
D)The relative ages of the three units cannot be determined with the information given.

Question 18

Concerning the relative ages of the basalt and the fault,the ____________.

A)fault must be older,according to the principle of cross-cutting relationships
B)basalt must be older,according to the principle of cross-cutting relationships
C)basalt must be older,according to the principle of original horizontality
D)Their relative ages cannot be determined from the information given.

Question 19

If the relative age of two formations (with respect to one another)is known,then the numerical ages for each formation can be inferred.

Question 20

Which of the following geologic principles is NOT a result of gravity?

A)original horizontality
B)cross-cutting relationships
C)original continuity
D)superposition

Question 21

Buried erosional surfaces between parallel sedimentary strata are termed ____________.

A)disconformities
B)angular unconformities
C)nonconformities

Question 22

Contact #1 is an example of a(n)____________.

A)conformable sedimentary contact
B)fault
C)baked contact
D)unconformity

Question 23

The youngest geologic unit visible in the cross section is the ____________.

A)granite
B)limestone
C)conglomerate
D)marble

Question 24

Which of the following is always the same for multiple isotopes of a single element?

A)atomic number
B)atomic mass number
C)tendency to decay radioactively
D)None of the above are correct.

Question 25

The surfaces named contacts #2 and #3 are examples of ____________.

A)conformable sedimentary contacts
B)faults
C)baked contacts
D)unconformities

Question 26

Numerical ages for boundaries between time units on the geologic time scale primarily resulted from the study of ____________,in conjunction with relative age data.

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

Question 27

Contact #3 is both a ____________ and a(n)____________ at various points.

A)conformable contact;unconformity
B)fault;unconformity
C)nonconformity;angular unconformity
D)disconformity;nonconformity

Question 28

When an unstable isotope decays,the daughter isotope that results is always a stable isotope.

Question 29

The surface below sedimentary rocks that overlie igneous or metamorphic rocks is termed a(n)____________.

A)disconformity
B)angular unconformity
C)nonconformity

Question 30

Dendrochonology 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

Question 31

Which statement about contact #3 is correct?

A)It and contact #2 once formed a continuous unconformity.
B)It was once elevated farther above contact #2,but faulting has brought them closer together.
C)It presents an example of an angular unconformity.
D)It must be younger than the conglomerate,due to the principle of baked contacts.

Question 32

Why is radiocarbon dating only rarely applied in geological work?

A)No substances on 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.

Question 33

The age of Earth CANNOT be reliably estimated from sediment thicknesses because ____________.

A)sedimentation rates are not likely to remain constant at any one locality over all of Earth's history
B)sedimentary rocks can be metamorphosed or melted
C)locally,much of Earth's history is represented by unconformities between strata rather than the strata themselves
D)All of the above are correct.

Question 34

The oldest geologic unit in the cross section is the ____________.

A)granite
B)marble
C)limestone
D)sandstone

Question 35

Concerning the relative ages of the granite and sandstone,the ____________.

A)granite must be older,according to the principle of superposition
B)sandstone must be older,according to the principle of superposition
C)granite must be older,according to the principle of components
D)Their relative ages cannot be determined from the information given.

Question 36

The principle of ____________ explains the occurrence of young rock within a newer igneous body.

A)baked contacts
B)cross-cutting relationships
C)original horizontality
D)inclusions

Question 37

Two atoms of a single element that differ in number of neutrons are said to represent two distinct ____________ of that element.

A)isomers
B)isotopes
C)isotherms
D)atomic species

Question 38

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
B)angular unconformity
C)disconformity
D)nonconformity

Question 39

Basaltic clasts within the basal layers of the conglomerate imply which of the following statements (choose the most correct answer)?

A)The conglomerate must be the older of the two.
B)The basalt must be the older of the two.
C)The section must not have been overturned by tectonic activity at any time.
D)B and C are both correct.

Question 40

Which of the following always varies among multiple isotopes of a single element?

A)atomic number
B)atomic mass number
C)tendency to decay radioactively
D)None of the above are correct.

Question 41

If all of Earth history were compressed into a single year,Homo sapiens would first appear on ____________.

A)February 26 (close to Mardi Gras)
B)April 15 (just before taxes are due)
C)October 31 (just in time for Halloween)
D)December 31,at 11:59 P.M.(just before the ball drops on New Year's Eve)

Question 42

In an unweathered sample of detrital sedimentary 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 reaction is 50 million years,how old is the rock?

A)200 million years
B)400 million years
C)750 million years
D)None of the above are correct.

Question 43

Magnetostratigraphy takes advantage of the fact that ____________.

A)Earth's magnetic field only arose 10,000 years ago
B)Earth's magnetic field has been uniformly strong,with constant polarity,throughout Earth's history
C)Earth's magnetic field has experienced numerous polarity reversals,with periods of normal and reversed polarity of varying lengths

Question 44

Basaltic clasts within the conglomerate have been radiometrically dated to 50 million years ago (Eocene epoch of the Tertiary period).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.

Question 45

Which proportion of a radioactive isotope is expected to remain in an unaltered (unreacted)state after the passage of three half-lives?

A)one-third
B)three-halves
C)one-eighth
D)one-sixth

Question 46

Radiometric dates applied to sedimentary rocks produce ages that are ____________.

A)just as accurate as when the technique is applied to igneous rocks
B)too young (postdate sedimentary deposition)
C)too old (pre-date sedimentary deposition)

Question 47

Attempts to measure the age of Earth by extrapolating modern riverine influx rates into the past to produce modern marine salinity from an initially freshwater ocean failed to take into account that ____________.

A)salt is removed through precipitation,balancing riverine input
B)dissolved salts from weathering of rock only rarely are transported all the way to the ocean
C)salts derived from the weathering of rock are insoluble in water

Question 48

Which statement best summarizes the development of the geologic time scale?

A)Numerical ages for rocks were known well before the relative sequence of sedimentary layers was established.
B)Relative ages for sedimentary strata were known well before accurate numerical dates for these rocks could be provided.
C)Names of relative ages (such as Silurian)and accurate numerical dates for these ages appeared at about the same time.

Question 49

Precisely speaking,a measured radiometric age for a mineral crystal within an igneous rock denotes 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 the Curie point for the mineral
D)temperature of the crystal became equal to the closure temperature for the mineral

Question 50

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 reaction is 50 million years,how old is the rock?

A)200 million years
B)400 million years
C)750 million years
D)None of the above are correct.