Deck 12: Deep Time: How Old Is Old

Question 1

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 1

B

Question 2

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

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

Answer 2

C

Question 3

Magma has intruded into some 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
B)baked contacts
C)original horizontality
D)original continuity

Answer 3

B

Question 4

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 a sequence of rock layers

Question 5

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 components
D)their relative ages cannot be determined from the information given

Question 6

In an undisturbed sequence of sedimentary rocks,younger layers overlie older layers,according to the principle of ________.

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

Question 7

Which principle of stratigraphy could be used to determine the relative ages of Layer 7 and Layer 3?

A)the principle of fossil succession
B)the principle of original horizontality
C)the principle of lateral continuity
D)the principle of inclusions

Question 8

Basaltic clasts within the basal layers of a conglomerate imply which of the following statements?

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)The basalt intruded into the conglomerate.

Question 9

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

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

Question 10

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 11

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 12

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 cross-cutting relationships.
B)The basalt must be older,according to the principle of cross-cutting 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.

Question 13

If an igneous dike cuts across a sequence of sedimentary beds,________.

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

Question 14

Within the world's sedimentary rocks,fossils ________.

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

Question 15

The principle of ________ explains the occurrence of older rock within a newer igneous body.

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

Question 16

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

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

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

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

Question 19

The oldest geologic unit is ________.

A)Layer 1
B)Layer 8
C)Layer 5
D)Layer 10

Question 20

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 eruption)have been active in the past and are 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

Question 21

Buried erosional surfaces between parallel sedimentary strata are termed ________.

A)disconformities
B)angular unconformities
C)nonconformities
D)marker beds

Question 22

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
B)fossil correlation
C)inclusion correlation
D)unconformity correlation

Question 23

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 24

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

A)Hadean
B)Archean
C)Phanerozoic
D)Proterozoic

Question 25

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

Question 26

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
B)400 million years
C)750 million years
D)1 billion years

Question 27

Magnetostratigraphy takes advantage of the fact that Earth's magnetic field ________.

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

Question 28

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

Question 29

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 30

Can the age of Earth be reliably estimated from sediment thicknesses?

A)Yes: sedimentation rates remain constant at any one locality throughout 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 Earth's surface.
D)No: much of Earth's history is represented by unconformities between strata rather than the strata themselves.

Question 31

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

A)atomic number
B)atomic mass number
C)tendency to decay radioactively
D)half-life

Question 32

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

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

Question 33

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

A)disconformity
B)angular unconformity
C)nonconformity
D)marker bed

Question 34

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.
D)Carbon-14 is destroyed by the heat of magma.

Question 35

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 the Curie point for the mineral
D)temperature of the crystal became equal to the closure temperature for the mineral

Question 36

After one half-life has passed,what is the ratio of parent isotopes to daughter isotopes?

A)16:0
B)8:8
C)4:12
D)2:16

Question 37

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 38

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

Question 39

When an unstable parent isotope decays,which of these is true?

A)The daughter isotope will be a stable isotope.
B)The daughter isotope may continue to decay.
C)The parent isotope's rate of decay slows.
D)The parent isotope becomes stable and stops decaying.

Question 40

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 41

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)isotopes are no longer free to move out of a crystal lattice
D)the last remaining magma crystallizes

Question 42

Accurate radiometric dating is possible only if a rock contains a measurable amount of ________.

A)parent isotope atoms
B)daughter isotope atoms
C)either parent or daughter atoms
D)both parent and daughter atoms

Question 43

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.

Question 44

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 45

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 46

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.

Question 47

How is the half-life of a radioactive parent isotope defined?

A)the time it takes for half of the parent isotope to decay to daughter isotope
B)half the time it takes for the parent isotope to completely decay
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

Question 48

How much of a radioactive parent isotope will remain after three half-lives have passed?

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

Question 49

If all of Earth's 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 50

In an unweathered sample of 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
B)400 million years
C)750 million years
D)1 billion years

Question 51

Seasonal changes create layering in glaciers known as ________.

A)growth banding
B)rhythmic layering
C)seasonal layering
D)annual banding