Deck 8: Geologic Time

Question 1

Examine the figure. If the Wingate Sandstone was deposited in the Triassic period and the Carmel Formation in the Jurassic, a visitor to Bryce Canyon National Park shouldn't expect to find any strata older than the ________ period.

A)Triassic
B)Cretaceous
C)Permian
D)Tertiary

Answer 1

A

Question 2

Which of the following describes radioactive decay by beta particle emission?

A)The atomic number of the daughter isotope is one more than the parent; the mass numbers are the same.
B)The daughter isotope has an atomic number one less than the parent and a mass number two less.
C)The mass number of the daughter isotope is one more than the parent and both isotopes have the same atomic number.
D)The daughter isotope has an atomic number two less than the parent and a mass number four less.

Answer 2

A

Question 3

Who first formulated the principle of uniformitarianism?

A)Aristotle
B)Lyell
C)Steno
D)Hutton

Answer 3

D

Question 4

Examine the figure that shows the sequence of strata in three Colorado Plateau national parks. Which unit(s)are shared by Grand Canyon National Park and Zion National Park?

A)Toroweap and Kaibab
B)Kaibab and Monekopi
C)Moenkopi and Chinle
D)Kaibab only

Question 5

An unconformity is a buried ________.

A)fault or fracture with older rocks above and younger rocks below
B)surface of erosion separating younger strata above from older strata below
C)fault or fracture with younger strata above and older strata below
D)surface of erosion with older strata above and younger strata below

Question 6

Since the Moenkopi Formation was deposited at the end of the Permian period and the very beginning of the Triassic, and the Navajo Sandstone was deposited at the end of the Triassic and into the Jurassic, what is the age of the Chinle Formation?

A)Permian
B)Triassic
C)Jurassic
D)Cambrian

Question 7

The longest subdivision of the geologic time scale is the ________.

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

Question 8

A datable mineral crystal contains 40% parent isotope. How many half-lives have passed since the crystal formed?

A)1
B)more than 1 but less than 2
C)more than 2 but less than 3
D)more than 3

Question 9

Which of the following is an essential characteristic of an index fossil?

A)The organism lived in a very specific environment or two, such as tropical volcanic islands.
B)The organism lived for a very limited period of geologic time.
C)The fossils of the organism are exceptionally well preserved.
D)The organism lived on the land, not in the ocean.

Question 10

Why isn't the Precambrian more finely divided into sub-divisions like periods and epochs?

A)Fewer and less diverse fossils exist in Precambrian rocks.
B)Precambrian rocks don't have radioactive isotopes in them.
C)Geologists just don't care about the Precambrian the way they do about more recent time periods.
D)The Precambrian lacks the igneous rocks that are most useful for radiometric dating.

Question 11

Examine the geologic timescale shown here. Which is the earliest period listed in the Mesozoic?

A)Cambrian
B)Permian
C)Triassic
D)Cretaceous

Question 12

Why do the eras of the Pharnerozoic eon all end with "zoic"?

A)They are based on rock called zoisites.
B)These names refer to life or living things; they invoke the changes in fossil organisms from one era to the next.
C)"Zoic" means "time" in Latin.
D)These eras were all first described near the London Zoo, so the names pay tribute to that location.

Question 13

The principle of ________ is the concept that ancient life forms evolved in a definite order and therefore their fossils can help determine the geologic ages of strata.

A)superposition
B)cross-cutting relationships
C)fossil succession
D)fossil assemblage

Question 14

Using the known rates of radioactive decay to date the crystallization of certain minerals is known as ________ dating.

A)conventional
B)radiometric
C)relative
D)fossil assemblage

Question 15

"This rock is fifteen million years old," is an example of ________.

A)a numerical date
B)a relative date
C)superposition
D)the principle of cross-cutting relationships

Question 16

Among the following radioactive parent isotopes, which has the shortest half-life?

A)uranium-238
B)potassium-40
C)rubidium-87
D)carbon-14

Question 17

The earliest 88 percent of geologic time is represented by the time span informally called the ________.

A)Paleozoic
B)Precambrian
C)Mesozoic
D)Phanerozoic

Question 18

Which of the following geologic observations would NOT bear directly on working out the sequence of geologic events in an area?

A)inclusions of sandstone in a granite pluton
B)a well-exposed dike of basalt in sandstone
C)an unconformity between a granite and sandstone
D)the feldspar and quartz contents of a granite

Question 19

The white arrow in this cross-section points to an unconformity (black line). What kind of unconformity is it?

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

Question 20

Catastrophism and uniformitarianism differed in which way?

A)Catastrophism argued for a young Earth, while uniformitarianism argued for an old Earth.
B)Catastrophism emphasized rapid change, while uniformitarianism argued for slow, gradual change being more important.
C)both of the above
D)none of the above

Question 21

Sandstone strata and a mass of granite are observed to be in contact. Which of the following statements is correct?

A)The sandstone is younger if the granite contains sandstone inclusions.
B)The sandstone is younger if it shows evidence of contact metamorphism.
C)The granite is older if the sandstone contains pebbles of the granite.
D)The granite is older if it contains inclusions of sandstone.

Question 22

Sedimentary layers can be important indicators of past environmental conditions that existed when the sediments were deposited.

Question 23

A worm would stand a poor chance of being fossilized because ________.

A)worms were very rare during the geologic past
B)worms have no hard parts
C)worms contain no carbon-14
D)worms live in the shallow ocean

Question 24

Alpha emission, beta emission, and electron capture are three different kinds of radioactive decay.

Question 25

The geologic time scale was devised before the techniques for numerical dating using radioactivity were developed.

Question 26

"John is older than Susan" is an example of a relative date.

Question 27

The further back in geologic time we go, the more detail we can discern about conditions on the ancient Earth.

Question 28

The idea of ________ suggests that the physical, chemical, and biological laws that operate today have also operated in the geologic past.

Question 29

A granite dike cuts across a shale. The dike gives a radiometric date of 84 million years old. The shale was therefore deposited more than 84 million years ago.

Question 30

The strata shown on the left can be correlated with units J, I, and H, on the right.

Question 31

Which is most useful for determining the age of the raisins in raisin bread, relative to the bread in which they are found?

A)principle of superposition
B)principle of original horizontality
C)principle of cross-cutting relationships
D)principle of inclusions

Question 32

According to the figure, the age of the Dakota Sandstone must be less than 160 million years, and greater than 66 million years old.

Question 33

The process by which geologists identify and match sedimentary strata and other rocks of the same ages in different areas is called superposition.

Question 34

Use the geological cross-section to determine the age of rock layer D as precisely as possible.

A)It is 40 million years old.
B)It is between 39 million years old and 25 million years old.
C)It is between 39 million years old and 17 million years old.
D)It is older than 17 million years old.

Question 35

James Hutton's proclamation that "we find no vestige of a beginning-no prospect of an end" is a concise summary of the philosophy of catastrophism.

Question 36

The Phanerozoic, Proterozoic, and Archean are all eons.

Question 37

The four basic units that make up the geologic time scale are the eon, the aria, the episode, and the period.

Question 38

Assuming that this is an undisturbed sedimentary sequence (that is, superposition is valid), and that unit G is Cambrian in age, unit F could be Ordovician.

Question 39

Permineralization and carbonization are methods of correlating rock units.

Question 40

Fossils of an organism can be found in rocks older than the organism itself.

Question 41

Compare the doctrine of catastrophism with the doctrine of uniformitarianism.

Question 42

Is carbon-14 an appropriate isotope for dating the metamorphic rocks at the bottom of the Grand Canyon? Explain.

Question 43

The amount of time it takes for half of the remaining radioactive isotopes to decay is the ________ of a isotope system.

Question 44

Most sedimentary rocks cannot be dated directly by ________ methods.

Question 45

All of geologic time prior to the beginning of the Paleozoic era is commonly referred to as the ________.

Question 46

What sequence of events would have to occur in order to produce the unconformity shown here?

Question 47

We now live in the ________ era.

Question 48

After three half-lives, ________ of an original, radioactive, parent isotope remains and the rest has decayed into the daughter isotope.

Question 49

Match the items in the first column with the correct descriptions in the second column.

A)fossil poop
B)a fossil organism that is restricted to a certain brief stretch of geologic time, but was widespread and abundant during its time on Earth
C)the notion that we can understand the geologic past by focusing on present day processes and physical laws; geologic change may be slow or gradual
D)a group of fossils that co-existed at the same time. Their overlapping ranges can help constrain the age of a rock unit that contains them
E)fossil tree sap
F)the defunct notion that the Earth is only a few thousand years old, and that all geologic change is accomplished rapidly through violent events
G)indirect evidence of ancient life, such as footprints, bite marks, and gastroliths
H)the remains or traces of ancient life
1)catastrophism
2)fossil
3)amber
4)fossil assemblage
5)coprolite
6)uniformitarianism
7)index fossil
8)trace fossil

Question 50

When radioactive potassium-40 decays, the stable daughter isotope ________ is produced.

Question 51

The remains or traces of prehistoric life are called ________.

Question 52

A sandstone is found to overlie a shale. The shale contains a volcanic ash layer that has been radiometrically dated to 84 million years ago. Both the shale and the sandstone are cut by a pluton of gabbro that has been dated to 60 million years old. How old is the sandstone layer? ________

Question 53

Compare and contrast relative age dating with radiometric age dating. What is a limitation (if any)of each?

Question 54

A lava flow includes fragments of limestone in it. Which rock unit is older, the lava flow or the limestone? ________

Question 55

The process by which geologists identify and match sedimentary strata and other rocks of the same ages in different areas is ________.

Question 56

Examine the figure that shows the age ranges of some fossil groups. If trilobites ranged from the Cambrian to the Permian, and ferns ranged from the Devonian until the present day, then rock unit B must have been deposited ________.

Question 57

All else being equal, in a horizontal sequence of sedimentary rock layers, each higher bed is younger than the bed below it. This idea is the principle of ________.

Question 58

Identify and label the three types of unconformities shown in this cross-section of the Grand Canyon.

Question 59

Would a pigeon or a penguin make a better index fossil for the present day? ________

Question 60

A(n)________ is an erosional unconformity with parallel beds or strata above and below.

Question 61

Which rock unit is most likely to have undergone regional metamorphism?

Question 62

Examine the geological cross-section and describe the order of all the geological events that can be depicted from this image. Don't limit yourself to merely the lettered rock units; include episodes of folding and erosion, too. Use descriptive geologic verbs like "deposition" and "intrusion" rather than simply saying the "rock unit J was formed."

Question 63

If numerical dating of rock unit A gave a crystallization age of 1.2 billion years, and numerical dating of rock unit F gave a crystallization age of 500 million years, then how old is rock unit E?

Question 64

Is rock unit F likely to be sedimentary, metamorphic, or igneous?

Question 65

Is rock unit D likely to be sedimentary, metamorphic, or igneous?

Question 66

What is the sense of offset on fault G?

Question 67

How would you figure out if rock unit A or rock unit D formed first, or if they coincided?

Question 68

Is there any way to say for sure whether rock unit A or rock unit D is older? Why or why not?