Deck 12: Deep Time: How Old Is Old

Question 1

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 limestone must be younger than the marble.
D) The relative ages of the three units cannot be determined with the information given.

Answer 1

B

Question 2

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.

Answer 2

A

Question 3

The oldest geologic unit is

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

Answer 3

A

Question 4

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 5

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.

Question 6

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 eruptions)have been active in the past at roughly the same rates.
D) physical processes observed today (such as erosion and volcanic eruption)occurred much more rapidly in the past,quickly sculpting the Earth's surface.

Question 7

A birthdate is an example of a(n)________ age.

A) relative
B) numerical
C) radiocarbon
D) isotopic

Question 8

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 original horizontality.
D) their relative ages cannot be determined from the information given.

Question 9

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 10

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 11

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

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

Question 12

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

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

Question 13

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

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

Question 14

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 15

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 the geologic column

Question 16

Which of the following statements is true regarding the clasts (labeled 5)inside the granite pluton?

A) The inclusions are the same age as the pluton.
B) The inclusions are younger than the pluton.
C) The inclusions are older than the pluton.
D) The relative age of the inclusions and the pluton cannot be determined.

Question 17

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 18

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 19

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) lateral continuity.
C) original horizontality.
D) uniformitarianism.

Question 20

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

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 21

Look at the figure below.The contact between the Vishnu Schist and the Tapeats Sandstone is a(n)

A) conformable contact.
B) disconformity.
C) nonconformity.
D) angular unconformity.

Question 22

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 23

Look at the figure below.The contact between the Unkar Group and the Tapeats Sandstone is a(n)

A) conformable contact.
B) disconformity.
C) nonconformity.
D) angular unconformity.

Question 24

Which of the following lists the divisions on the geologic column from largest (most general)to smallest (most specific)?

A) epoch,period,era,eon
B) period,epoch,eon,era
C) era,eon,epoch,period
D) eon,era,period,epoch

Question 25

Look at the figure below.Notice the erosional surface on the top of the Muav Limestone.This contact between the Muav limestone and the Temple Butte Formation is an example of a(n)

A) conformable contact.
B) disconformity.
C) nonconformity.
D) angular unconformity.

Question 26

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 27

Accurate radiometric dating typically requires that 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 28

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 29

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

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

Question 30

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 31

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 32

Buried erosional surfaces between parallel sedimentary strata are termed

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

Question 33

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 34

Which of the following is true of the geologic column?

A) It is the complete record of the Earth's history that is preserved in the rocks at any given location.
B) It portrays the spatial distribution of rock units at the Earth's surface.
C) It is a composite stratigraphic column created by correlating strata from millions of locations around the world.
D) It is an interval of strata composed of a specific rock type or group of rock types that together can be traced over a broad region.

Question 35

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

A) the time it takes for half of the parent isotope to decay
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 36

Referring to the graph below,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

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

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

Question 38

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 surface temperatures.
D) temperature of the crystal became equal to the closure temperature for the mineral.

Question 39

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 40

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 41

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 42

Correlate the layers in the following three stratigraphic columns by drawing lines from the top and bottom of matching formations.What is the oldest unit in this region? The youngest unit?

Question 43

Discuss what the numerical age represents when radiometrically dating a basalt,a gneiss,and a sandstone.

Question 44

Seasonal changes create layering in glaciers known as

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

Question 45

What is an unconformity? Illustrate the three types of unconformities.

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

Why have no rocks older than 4.12 Ga been found in the Earth's crust?

Question 48

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 49

Describe the plausible geologic history of the rocks in the following photo/diagram.

Question 50

Compare and contrast lithologic correlation and fossil correlation.In what circumstance is each most useful? Provide an example of each.

Question 51

Your friend the archaeologist,who studies the ancient human past,has asked you to find a numerical date for some hominid artifacts found buried by ash from a volcanic eruption.To do this,you can use carbon-14 dating,which has a half-life of 5,730 years,or uranium-238,which has a half-life of
4.5 billion years.Based on their half-lives,which isotopic dating system will give your friend the most accurate numerical age? Explain.

Question 52

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 53

Why is radiocarbon dating rarely applied in geological work?

A) No substances on the 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 54

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 55

Place the layers and geologic events in order from oldest to youngest.Make sure to include all of the layers and events,including the top surface.(There will be one event/layer per line when complete.)

Question 56

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 57

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

A) only arose 10,000 years ago.
B) has been uniformly strong,with constant polarity,throughout the 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 58

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 59

How is a relative age different from a numerical age? How are each of these determined?

Question 60

What is the principle of uniformitarianism? How does this principle apply to our understanding of the Earth system? How is this useful in the context of relative dating?