Deck 10: Deep Time: How Old Is Old

Question 1

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 1

C

Question 2

Why did James Hutton deduce that there must have been a long time before human history began?

A) He found no physical remains of humans in his geologic investigations.
B) No human had seen the full process of sediment deposition to mountain formation.
C) He found no signs of humans in the ancient rock record.
D) No human had observed continents in different locations.

Answer 2

B

Question 3

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

Answer 3

B

Question 4

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

A) relative age
B) numerical age

Question 5

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 6

As understood by modern geologists,the principle of uniformitarianism implies that ____________.

A) 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 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 7

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

Question 8

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 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

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 12

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

A) Archean
B) Phanerozoic
C) Proterozoic

Question 13

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 14

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

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

Question 15

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 16

Within the world's undisturbed sequences of sedimentary rocks,fossils ____________.

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

Question 17

What principle allows geologists to deduce that folds in beds occurred after deposition?

A) principle of uniformitarianism
B) principle of superposition
C) principle of lateral continuity
D) principle of original horizontality

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

The basalt body is best described as a ____________.

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

Question 20

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 21

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) Both b and c are both correct.

Question 22

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 23

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 24

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

A) disconformity
B) angular unconformity
C) nonconformity

Question 25

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 26

Which of the following is the most correct reason why no single location on Earth contains a complete record of Earth history?

A) because of unconformities
B) because of erosion
C) because of times of nondeposition
D) because deposition is constantly occurring

Question 27

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 28

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 29

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

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

Question 30

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

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

Question 31

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 32

Buried erosional surfaces between parallel sedimentary strata are termed ____________.

A) disconformities
B) angular unconformities
C) nonconformities

Question 33

The principle of ____________ explains the occurrence of older rock within an igneous body.

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

Question 34

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 35

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 36

Why do some rock formations go by names containing specific rock types,while others retain the word "formation"?

A) It depends on the locality of the rock formation.
B) Areas named as a "formation" contain more than one rock type.
C) The rock type could not be determined if it was named "formation."
D) It is the choice of the person who first studies the rock formation.

Question 37

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

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

Question 38

Presented with an outcrop containing a succession of beds and only the knowledge of relative-age dating,which of the following would be the best to look for to determine the story of the outcrop?

A) a fossil that could be found in all of the beds
B) an intrusion, as it would be older than the surrounding rock
C) a fossil found in only a few layers
D) a fault, as it would be older than the surrounding rock

Question 39

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

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

Question 40

If no single location records all of Earth's history,how was the geologic column created?

A) by interpolating the rest of the column from the largest column that could be found
B) by ignoring universal gaps in time
C) by using only the information from the largest column found
D) by globally correlating small columns and filling in the gaps

Question 41

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 42

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 43

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 44

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 45

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 46

Why can't geologists isotopically date a clastic sedimentary rock?

A) They do not contain the appropriate minerals.
B) These types of rocks do not contain enough of the appropriate minerals to date.
C) The minerals would yield the date of when they crystallized in a metamorphic or igneous rock.
D) The minerals would yield the date of when they weathered from their source material.

Question 47

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

Question 48

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.

Question 49

Why don't we find rocks with ages between 4.03 and 4.57 Ga in the Earth's crust?

A) The crust was molten during the Hadean Eon.
B) At the beginning of Earth's history, the planet was heavily bombarded with meteorites.
C) They have been subducted and lost to geologists.
D) Both a and b are correct.
E) Both b and c are correct.

Question 50

Why were geologists able to switch from determining relative age of geologic events to determining the numerical age?

A) New fossils were discovered.
B) Radioactivity was discovered.
C) New geologic units were discovered.
D) Numerical age dating became more widely accepted.

Question 51

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 52

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 53

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 54

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 55

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 grains formed,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 56

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 57

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 58

When radioactively dating a rock,which of the following would NOT result in an inaccurate age reading?

A) using weathered rocks
B) homogenizing the rock material
C) using all of the minerals present
D) using only the daughter isotopes

Question 59

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 60

If a geologist wished to date an outcrop of sandstone beds that he or she found,which of the following should they look for to yield a specific date?

A) a fossil known to have a wide geographic distribution and to have existed over a long range of time
B) a sedimentary layer constrained by igneous or metamorphic rocks
C) a fossil known to have a small geographic distribution and to have existed over a short range of time
D) a sedimentary layer cut across by a fault