Deck 10: Deep Time: How Old Is Old

Question 1

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

Answer 1

B

Question 2

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 equally correct.

Answer 2

D

Question 3

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

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

Answer 3

C

Question 4

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

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

Question 5

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 6

In an 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 7

Concerning 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 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

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

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

Question 10

The basalt body is best described as a ____________.

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

Question 11

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 12

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

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

Question 13

Concerning 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 14

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 15

Concerning relative ages of the shale and sandstone,____________.

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 16

Contact #3 is both a ____________ at various points.

A) conformable contact and an unconformity
B) fault and an unconformity
C) nonconformity and an angular unconformity
D) disconformity and a nonconformity

Question 17

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

A) relative age
B) numerical age

Question 18

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 19

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

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

Question 20

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 21

Buried erosional surfaces between parallel sedimentary strata are termed ____________.

A) disconformities
B) angular unconformities
C) nonconformities

Question 22

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

A) disconformity
B) angular unconformity
C) nonconformity

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) Archean
B) Phanerozoic
C) Proterozoic

Question 25

The correct answer to question 30 illustrates the principle of ____________.

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

Question 26

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

Question 27

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 (predate sedimentary deposition)

Question 28

Numerical ages for recent geologic events can sometimes be determined by the study of ____________.

A) layering (growth lines) in shells
B) annual growth rings in trees
C) seasonal layering in glacial ice
D) all of the above

Question 29

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

Question 30

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 31

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 32

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 33

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 34

Within the world's sedimentary rocks,fossils ____________.

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

Question 35

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 36

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.

Question 37

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 38

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 39

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 40

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) The Earth was once hotter than it presently is today.
B) The Earth may have been molten when first formed.
C) No new heat has been added to the Earth since its initial formation.
D) The Earth would lose heat over time through radiation into outer space.

Question 41

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

Question 42

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

Question 43

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

Question 44

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

Question 45

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