Deck 9: Deep Time: How Old Is Old

Question 1

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.

Answer 1

A

Question 2

Several geologic principles are used to determine __________ ages.

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

Answer 2

A

Question 3

If horizontal sedimentary strata overlie tilted strata (and no fault is present), the eroded surface between the horizontal and tilted strata must be a(n)

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

Answer 3

B

Question 4

If the relative ages of two formations are known, their __________ can be inferred.

A)absolute ages
B)fossil assemblages
C)lithologies
D)relative positions in a sequence of rock layers

Question 5

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 6

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 without additional information.

Question 7

An erosional surface between two sequences of flat-lying sedimentary rocks is called a(n)

A)angular unconformity.
B)disconformity.
C)nonconformity.
D)misconformity.

Question 8

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 9

A tilted sequence of sedimentary rocks violates which principle?

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

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

A __________ consists of a sequence of similar rocks that can be found across a region.

A)geologic contact
B)stratigraphic formation
C)stratigraphic column
D)marker bed

Question 12

Unconformities represent __________ in the rock record.

A)erosion or nondeposition
B)continuing sequences
C)changes in size of the sediments
D)iridium layers from meteorites

Question 13

It is known that Rock A is older than rock B but younger than rock C. It would then be accurate to say that rock __________ is the oldest, followed by rock __________, with rock __________ being the youngest.

A)A; C; B
B)C; B; A
C)C; A; B
D)B; A; C

Question 14

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 15

The beginning and end points of eras, epochs, and periods on the geologic time scale are set by __________ ages.

A)relative
B)systematic
C)numerical
D)isotrophic

Question 16

The geologic time scale is broken into a series of eras, epochs, and periods based mainly on the fossils found in each section. This is an example of __________ dating.

A)relative age
B)radiometric
C)numerical
D)isotopic

Question 17

Buried erosional surfaces between parallel sedimentary strata are termed

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

Question 18

Based on the following 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

A basaltic lava flow contains fragments of sedimentary rocks. Which of the following statements is true regarding their relative ages?

A)The lava flow is younger than the sedimentary rock.
B)The lava flow is older than the sedimentaryrock.
C)The lava flow and the sedimentary rock are the same age.
D)More information would be needed to determine their relative ages.

Question 20

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 21

A geologist in South Dakota finds an assemblage of dinosaur bones in an outcrop for the Hilltown Formation, and his colleague in China discovers an assemblage of bones from a different dinosaur in the Liaoning Formation. What can be said about the two formations?

A)They are no younger than Cretaceous in age.
B)They are no older than Jurassic.
C)They are the exact same age.
D)They are no younger than Triassic in age.

Question 22

A __________ is a geologic layer that is distinct enough to allow it to be found regionally and used to correlate rocks.

A)marker bed
B)geologic contact
C)stratigraphic bed
D)disconformity

Question 23

A layer of shale that contains a distinctive fossil could be used as a

A)geologic contact.
B)marker bed.
C)stratigraphic sequence
D)depositional contact.

Question 24

Two layers of rock contain trilobites that have the same body morphology; however, one rock layer is a shale and the other is an ironstone. Can these two layers be used for correlation?

A)No, layers with the same lithology can only be used for correlation purposes.
B)No, the ironstone has been altered by oxidation and thus is older than the shale.
C)Yes, if the trilobites are the same, then the layers were formed at the same time.
D)Yes, the ironstone is the altered remains of the shale and thus the layers are the same.

Question 25

The surfaces named contacts #2 and #3 in the following image are examples of

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

Question 26

According to the following image, 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 27

In the following image of the Grand Canyon, identify the angular unconformity.

A)A
B)B
C)C
D)D

Question 28

In the following image, 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

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 to daughter isotopes
C)the time for parent isotopes to undergo half the decay steps to produce a daughter isotope
D)half of the average rate of decay of the parent isotope

Question 30

The geologic column

A)is a composite stratigraphic column that symbolizes the history of life on Earth.
B)is a composite stratigraphic column that symbolizes the entirety of Earth history.
C)can be seen in its entirety in Ethiopia, where the earliest hominid fossils are found.
D)is exposed in its entirety in the Grand Canyon.

Question 31

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

A)parents
B)isotopes
C)isotherms
D)daughters

Question 32

Concerning the relative ages of the marble and sandstone,

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

Question 33

Stratigraphic correlation is conducted by matching __________ and __________ .

A)geologic contacts; rock types
B)fossils; unconformities
C)lithologic layers; fossils
D)marker beds; eras

Question 34

In the following image of the Grand Canyon, identify the nonconformity. Vishnu

A)A
B)B
C)C
D)D

Question 35

Concerning the relative ages of the limestone and sandstone,

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

Question 36

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

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

Question 37

In the following image of the Grand Canyon, identify the disconformity.

A)A
B)B
C)C
D)D

Question 38

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 39

Which of the units in the following image would be least useful for obtaining a numerical age?

A)A
B)B
C)C
D)D

Question 40

The __________ represents the global strata from the entire Earth's history.

A)stratigraphic formation
B)lithologic sequence
C)geologic column
D)stratigraphic column

Question 41

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 42

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

Question 43

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 44

What is the parent-to-daughter isotope ratio if 1 half-life has passed?

A)16:0
B)8:8
C)4:12
D)2:14

Question 45

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

Question 46

Do the fossils preserved in the rock record accurately and completely represent the entire extent and biodiversity of life on Earth? What does it take to create and preserve a fossil?

Question 47

It appears that the dates that early geologists identified as the boundaries between eras coincide with mass extinction events. What is a mass extinction event? What might this event look like in the fossil record?

Question 48

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 49

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 50

Describe the plausible geologic history of the rocks in the diagram below.

Question 51

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?

Question 52

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 53

If the ratio of parent to daughter isotopes is 25:75, how many half-lives have passed?

A)2
B)3
C)1
D)4

Question 54

In the 1800s, Lord Kelvin estimated the age of 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)Earth was once hotter than it presently is today.
B)Earth may have been molten when first formed.
C)No new heat has been added to Earth since its initial formation.
D)Earth would lose heat over time through radiation into outer space.

Question 55

How much of a radioactive parent isotope will remain after 3 half-lives have passed?

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

Question 56

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 57

Which type of unconformity requires there to have been little to no deformation in the rocks before and after the unconformity was created?

A)disconformity
B)angular unconformity
C)misconformity
D)nonconformity

Question 58

Sedimentary rocks cannot be used to determine dates on the geologic time scale because the numerical age

A)is the time that the rocks were exposed at the surface.
B)retains too much error associated with diagenesis.
C)is the age of the igneous rocks that make up the sediment.
D)is reset when the sediments are buried and cemented.

Question 59

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