Deck 11: Geologic Time

Question 1

The principle of inclusions which states that the source of rock fragments found in a unit must be older than the unit with the fragments is important because ________.

A)it provided a tool for sorting out the relative timing of various geologic events
B)it provided a way to recognize if rocks had been deformed
C)it showed that igneous rocks were younger than sedimentary rocks
D)it allowed geologists to correlate rock units over large distances

Answer 1

A

Question 2

The principle of cross-cutting relationships which states that a geologic feature that cuts across another feature must be younger than the feature it cuts is important because ________.

A)it provided a tool for sorting out the relative timing of various geologic events
B)it provided a way to recognize if rocks had been deformed
C)it showed that igneous rocks were younger than sedimentary rocks
D)it allowed geologists to correlate rock units over large distances

Answer 2

A

Question 3

If you observe a nonconformity,you would infer that the region had experienced ________.

A)deposition in shallow water,uplift or lowering of sea level enough to expose the rocks to erosion and non-deposition for a period of time,and subsequent resubmergence of the remaining sedimentary units where they experience new deposition
B)uplift and tilting of sedimentary units that exposes them to erosion over a period of time with subsequent renewed deposition
C)intrusion of igneous rocks into a depositional setting,forcing the sedimentary layers upward and possibly deforming them,followed by subsidence of the remaining sedimentary layers and renewed deposition
D)deposition of sedimentary layers on crystalline igneous or metamorphic rocks that are exposed at the surface of the earth

Answer 3

D

Question 4

A major difference between Catastrophism and Uniformitarianism is ________.

A)Uniformitarianism does not allow for catastrophic events while Catastrophism is based on the assumption that they are the major forces of change in the earth
B)Catastrophism requires all changes on earth be due to unpredictable events that cannot be explained while Uniformitarianism proposes that all events are predictable
C)Uniformitarianism explains the young age of the earth by suggesting that while processes have not changed over time,the rates of processes may vary significantly
D)Catastrophism supports rapid changes on the earth and a young age of the earth while Uniformitarianism requires long times for changes to be significant and thus a very old earth

Question 5

The principle of lateral continuity proposes that sedimentary rock layers continue in all directions until they grade into a different rock type or thin out on the edge of a basin is important because ________.

A)it showed that catastrophism could not explain the flat layers of the earth
B)it provided a way to recognize if rocks had been deformed
C)it provided an explanation how rocks behave in a depositional setting
D)it allowed geologists to correlate sedimentary rock units over large distances

Question 6

An important tool in understanding the actual numerical dates of past geologic events is ________.

A)radioactivity
B)fossils
C)unconformities
D)depositional rates
E)cross-cutting relationships

Question 7

The principle of superposition which states that in undeformed rocks,the younger rocks will be on top of older rocks,is particularly important because ________.

A)it supports the laws of gravity which indicate that rocks must be deposited on something that already exists
B)it showed that the interior of the earth is not growing outward
C)it provided an order for assembling the relative ages of various rock layers
D)it proved that life evolved by putting fossils in a logical order

Question 8

In the late 1800's various principles (original horizontality,inclusions,cross cutting relations,etc.arête)were established and used to ________.

A)determine the age of the earth
B)determine the age of events on the earth
C)organize the order in which events occurred on earth
D)prove that evolution was a valid theory that could explain many geologic observations

Question 9

If you observe an angular unconformity,you would infer that the region had experienced ________.

A)deposition in shallow water,uplift or lowering of sea level enough to expose the rocks to erosion and non-deposition for a period of time,and subsequent resubmergence of the remaining sedimentary units where they experience new deposition
B)uplift and tilting of sedimentary units that exposes them to erosion over a period of time with subsequent renewed deposition
C)intrusion of igneous rocks into a depositional setting,forcing the sedimentary layers upward and possibly deforming them,followed by subsidence of the remaining sedimentary layers and renewed deposition.
D)deposition of sedimentary layers on crystalline igneous or metamorphic rocks that are exposed at the surface of the earth

Question 10

In the mid-1600s,James Ussher determined that the earth was created in 4004 BC based on ________.

A)ancient records from the Egyptians
B)Biblical passages
C)fossils
D)rates of deposition and erosion of earth materials
E)none of the above

Question 11

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 12

The principle of horizontality which states that sediments are usually deposited in relatively flat layers is important because ________.

A)it showed that catastrophism could not explain the flat layers of the earth
B)it provided a way to recognize if rocks had been deformed
C)it provided an explanation how rocks behave in a depositional setting
D)it allowed geologists to correlate sedimentary units over large distances

Question 13

Unconformities which represent a break in the geologic record of deposition are important because ________.

A)they cannot be mapped
B)they represent a period of major activity
C)the fossils found in the unconformities can be used to correlate global time period
D)they give an indication of sea level rise within an ocean basin

Question 14

Which of the following best characterizes an angular unconformity?

A)Tilted strata lie below the unconformity; bedding in younger strata above is parallel to the unconformity.
B)Horizontal lava flows lie below the unconformity and horizontal; sedimentary strata lie above.
C)The discordant boundary between older strata and an intrusive body of granite.
D)Tilted strata that lie below the unconformity are truncated at the unconformity,and strata above the unconformity are also tilted and truncated,but at a different angle

Question 15

One of the primary goals of geology is to ________.

A)identify all of the rocks on the surface of the earth
B)develop a comprehensive relationship between fossils and geologic formations
C)understand the role of plate tectonics in the earth's evolution
D)understand the history of the earth
E)determine the role of meteorites in the decline of species over time

Question 16

One reason that Catastrophism was popular was ________.

A)Ussher's estimated age of the earth required catastrophic events to form mountains and canyons
B)Hutton's observations of great geologic time could not explain the rise of mountains or formation of deep canyons
C)everyone loves a disaster and as a result,the hypothesis that supported disasters was a favorite
D)there were many real catastrophes,like earthquakes and volcanic eruptions,to support the Catastrophism idea

Question 17

If you observe a disconformity,you would infer that the region had experienced ________.

A)deposition in shallow water,uplift or lowering of sea level enough to expose the rocks to erosion and non-deposition for a period of time,and subsequent resubmergence of the remaining sedimentary units where they experience new deposition
B)uplift and tilting of sedimentary units that exposes them to erosion over a period of time with subsequent renewed deposition
C)intrusion of igneous rocks into a depositional setting,forcing the sedimentary layers upward and possibly deforming them,followed by subsidence of the remaining sedimentary layers and renewed deposition
D)deposition of sedimentary layers on crystalline igneous or metamorphic rocks that are exposed at the surface of the earth.

Question 18

Who is credited with formulating the doctrine of uniformitarianism?

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

Question 19

The basic concept of Uniformitarianism is ________.

A)nothing has changed since the earth was formed
B)geology has not changed since the earth was formed but other things do change
C)geology changes constantly but the rules that control those transformations do not change
D)there is a predictable way that the laws of nature change over time and we are beginning to understand them
E)evolution,Plate Tectonics,and similar theories are all related and can be viewed as the grand theory of Uniformitarianism.

Question 20

In the late 1700s James Hutton published his important work titled ________.

A)Catastrophism
B)Principles of Geology
C)Modern Earth Science
D)Theory of the Earth

Question 21

You pick up a sandstone.In the rock sample you see an impression of a sea shell in the rock.This type of fossil is a ________.

A)mold
B)cast
C)permineralized fossil
D)pseudofossil

Question 22

Paleontology is the study of ________.

A)paleo meaning old,and ontology referring to philosophical study of nature,so paleontology is the study of old nature
B)ancient life
C)prehistoric human history
D)none of the above

Question 23

Little Johnnie from down the street from your house brings an object that looks like a bone,and Johnnie says "look,I found a dinosaur bone." Which of the following would not be useful in evaluating Johnnie's claim?

A)Examine the object for hardness to determine if the sample is permineralized.
B)Ask if the object was found embedded in rock.
C)Evaluate the object for fine textures indicative of bone material or replaced bone material.
D)Extract charcoal from the object and use carbon-14 dating

Question 24

The Morrison Formation is exposed in the western United States and represents a nonmarine deposit with abundant dinosaur fossils.Much of the Morrison is pure mudstone,yet it is common to find highly polished pebbles and cobbles in the mud.Which of the following do you think is the best explanation of these cobbles?

A)They were placed in the mud by space aliens.
B)They represent meteorites that killed the dinosaurs.
C)They are impossible; people must have put them there.
D)They are gastroliths,a trace fossil.

Question 25

By applying the law of superposition,________ dates can be determined.

A)conventional
B)radiometric
C)relative
D)both relative and radiometric

Question 26

You go for a hike across an outcropping of sandstone and you see large footprints in the sandstone.You have just found ________.

A)Bigfoot
B)a trace fossil
C)proof of an ancient flood
D)a mold

Question 27

Petrified wood is an example of a fossil formed by ________.

A)direct preservation
B)cast and mold preservation
C)permineralization replacing original cellulose of the wood
D)trace fossil imprints

Question 28

Who made the first clear statement of the law of superposition? When?

A)John Wesley Powell,nineteenth century
B)William Smith,eighteenth century
C)John Stuart Priestly,nineteenth century
D)Nicolaus Steno,seventeenth century

Question 29

Which of the following is not a fossil?

A)imprint of an invertebrate shell in a mudstone
B)a tooth from an early man site in a lake sediment deposit
C)a mummified sloth in a cave
D)None of the above-these are all fossils.

Question 30

________ is an erosional contact between tilted,older strata below and horizontal,younger strata above.

A)Inverse bedding
B)An angular unconformity
C)A disconformity
D)Cross cutting

Question 31

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

A)worms have been rare during the geologic past
B)worms have no hard parts
C)worms contain no carbon-14
D)all of these

Question 32

Rare,but complete preservation of fossils occurs in ________.

A)limestone
B)shale
C)amber
D)mudstone

Question 33

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)the feldspar and quartz contents of a granite
D)an unconformity between a granite and sandstone

Question 34

Visualize five horizontal sedimentary strata exposed in a cliff or canyon wall identified by consecutive numbers,1 being the lowest bed and 5 being the highest.Which of the following statements concerning the strata is true?

A)Bed 5 is the oldest.
B)Beds l and 3 are older than bed 4.
C)Bed 4 is older than bed 2.
D)Bed 3 is older than beds 2 and 4.

Question 35

Which of the following organisms would be most likely to be preserved in the geologic record?

A)the bones of a dinosaur that lived on semi-arid plains
B)a clam with a thick calcite shell that lived on a mudflat
C)a tree
D)a mussel that clings to rock outcrops in the surf zone

Question 36

Which of the following refers to the investigative process by which geologists identify and match sedimentary strata and other rocks of the same ages in different areas?

A)super matching
B)correlation
C)strata indexing
D)cross-access dating

Question 37

Assume that you have just examined several flat-lying sedimentary layers.After much study you determine that there is a considerable span of time for which no sedimentary rock layer exists at this site.You have just discovered a(n)________.

A)angular unconformity
B)series of conformable strata
C)disconformity
D)example of cross-cutting relationships

Question 38

One type of fossil that can preserve details of organic soft parts is ________.

A)permineralization
B)cast
C)coprolites
D)carbonized imprints

Question 39

Which type of unconformity would generally indicate the greatest amount of erosion prior to deposition of the overlying rocks?

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

Question 40

What fundamental concept states that in a horizontal sequence of conformable sedimentary strata,each higher bed is younger than the bed below it?

A)law of original correlation
B)theory of correlative deposition
C)law of superposition
D)theory of superstition

Question 41

An important geochronometer is the decay of 147Sm to 143Nd.What type of radioactive decay is involved in this parent-daughter pair?

A)beta decay
B)electron capture
C)alpha decay
D)a positron capture

Question 42

Which of the following is not a very long-lived,radioactive isotope?

A)U-238
B)K-40
C)Rb-87
D)C-14

Question 43

Consider the names of the eras in the geologic time scale.What is meant by "zoic"?

A)life; living things
B)rocks; lithified strata
C)time; recording of events
D)places; geographic references

Question 44

The decay of 40K has a half of 1.3 × 109 years.The age of the earth is estimated at 4.6 × 109 years.The decay of 40K is a major heat source for the earth's interior.Relative to today,how much more heat was produced by 40K in the early Archaeon era or 3.9 × 109 years ago?

A)2x
B)4x
C)6x
D)8x

Question 45

You observe a distinct,red sandstone rock body about 50 m thick that is depositionally overlain by a red shale with interbedded gypsum and you follow this boundary in the rock bodies for 1 km until you cross a fault which has displaced the boundary between the two rock bodies.You walk along the fault and see a boundary between a 50 m thick red sandstone and overlying red shale interbedded with gypsum.You conclude ________.

A)this is impossibly complex; the fault broke up all the rocks
B)this new exposure of sandstone,shale and gypsum must be a different age rock unit
C)the stratigraphic section must have been inverted by the deformation; the rocks are upside down
D)the second exposure of sandstone,shale and gypsum correlates to the first,and the boundary between the sandstone and shale is the same stratigraphic horizon

Question 46

Faunal succession recognized in the sequence of fossils in stratified sedimentary rocks was a key concept that led to ________.

A)the concept of evolution of life on Earth
B)continental drift
C)sea floor spreading
D)Catastrophism and evidence the world was once covered with water

Question 47

When a radioactive isotope decays by electron capture,the electron ________.

A)combines with a neutron in the nucleus,raising the mass number of the daughter isotope by one
B)combines with a proton in the nucleus; the atomic number of the daughter is one less than the parent
C)makes the parent isotope into an ion with a charge of negative one
D)makes the daughter isotope into an ion with a charge of positive one

Question 48

Assume that man's recorded history can be stretched back to 4600 years before the present.This is approximately what fraction of geologic time?

A)one ten-thousandth
B)one millionth
C)one billionth
D)one hundred-thousandth

Question 49

What is the age of the Earth accepted by most scientists today?

A)6)4 billion years
B)4)5 million years
C)4)5 billion years
D)6)4 million years

Question 50

The ratio of parent to daughter isotopes in a radioactive decay process is 0.40.How many half-lives have elapsed since the material was 100% parent atoms?

A)less than l
B)more than 3
C)between l and 2
D)between 2 and 3

Question 51

The ________ is the idea or concept that ancient life forms succeeded each other in a definite,evolutionary pattern and that the contained assemblage of fossils can determine geologic ages of strata.

A)principle of cross correlation
B)law of fossil regression
C)law of correlative indexing
D)principle of fossil succession

Question 52

The subdivision of the geologic time scale that represents the longest time span is called a(n)________.

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

Question 53

A geologist is working in an area with exposed sedimentary rocks and finds a well exposed sequence of stratified rocks.As he works through a thick sequence of limestone,he sees abundant large clam fossils that produce an interlocking texture suggesting a reef,but within the limestone section these clams disappear and the overlying limestone is made up primarily of fragments of corals.He now moves 50 km away and finds limestones interbedded with shales,and the limestones contain the same clam fossils he had seen previously 50 km away.As he continues through this section,the rocks become entirely limestone,and the clams disappear again with coral fossils above forming a reef structure.He concludes ________.

A)this is impossible; the rocks are different at the same place the fossils change
B)the horizon where the clams disappear occurred at the same time in the two sections when the clams went extinct
C)clams have nothing to do with reefs,so he needs to go back to the first section to determine what he missed
D)sea level must have risen abruptly in a great catastrophe to produce the coral fragments scattered over 50 km

Question 54

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

A)The organism lived only in specific environments such as beaches or estuaries.
B)The organism only lived for a short period of geologic time.
C)The fossils are exceptionally abundant and well preserved.
D)The fossils occur in deep-water marine sediments,but the organism actually lived in the sunlit,surface layer of the ocean.

Question 55

In the last 20 years geologists have begun measuring accumulation of Helium (He)in some minerals because these minerals can retain He at temperatures up 100-200°C.The "date" gives a time when the material cooled below the temperature where the helium began to be retained,which is related to the depth of the material.Where do you think the He comes from that allows this technique to work?

A)the atmosphere,like carbon-14
B)the sun
C)beta decay of some radioactive element
D)alpha decay of some radioactive element

Question 56

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

Question 57

A geologist observes abundant fossils of a distinctive trilobite species in a shale,but this trilobite disappears as she walks through the shale.In younger rocks,just above the horizon where the fossil disappears another species of trilobite becomes the prominent fossil in similar shales.Which conclusion is most logical for this observation?

A)The organisms whose remains form the first fossil moved from the area for unknown reasons.
B)A hurricane or other catastrophe killed all of the early species so the other species could move in.
C)The second,trilobite group in the upper section went extinct where the change in fossils is seen.
D)The first trilobite species went extinct and its ecological niche was occupied by another species,which may have evolved from the first.

Question 58

The half-life of carbon-14 is about 6000 years.Assume that a sample of charcoal formed by burning of living wood 15,000 years ago.How much of the original carbon-14 would remain today?

A)more than one-half
B)between one-fourth and one-eighth
C)between one-half and one-fourth
D)between one-half and one-third

Question 59

Oysters are an invertebrate the lives today in brackish waters along coastal zones.When a geologist working in stratified rocks observes a limestone bed with oyster fossils overlain by beds with clam and echinoderm fossils indicative of marine conditions,the fossils probably indicate ________.

A)the oysters went extinct while these rocks were being deposited
B)the oysters evolved into clams and echinoderms
C)the environment changed as sea level rose,displacing the oysters environment with marine conditions represented by the clams and echinoderms
D)There is not sufficient information to reach any conclusion from these observations.

Question 60

Which radioactive decay used for radiometric dating is not an isotope that was generated during nuclear synthesis in the star that went supernova and its products became our solar system?

A)238U
B)147Sm
C)40K
D)14C

Question 61

Radiometric data was the key to modern geology replacing catastrophism.

Question 62

The era known as the "age of mammals" is the ________ era.

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

Question 63

A disconformity is an erosional unconformity with parallel beds or strata above and below.

Question 64

Numerical dates based on radioactivity are very important for studying Precambrian geologic history because fossils are rare or absent.

Question 65

superposition correlation original horizontality inclusions

Question 66

Which method best describes how the geologic time scale,which was developed through fossil successions in sedimentary rocks,was tied to absolute time even though sedimentary rocks cannot usually be dated directly by geochronology?

A)Geologists estimated time through sedimentation rates,then using those rates together with maximum ages of underlying rocks that are datable,to extract a time interval and rate for deposition of the sedimentary rocks.
B)Geologist used things like volcanic ash beds,interbedded volcanic rocks,cross-cutting intrusive igneous rocks,etc.in sedimentary sections with a known fossil succession,and this age was extrapolated globally.
C)Geologists recently developed a technique to directly date sedimentary rocks,solving the problem.
D)Geologists realized that there were many other cosmogenic isotopes besides Carbon 14 that allow the dating of sediments,and this has allowed the dating of sedimentary rocks.

Question 67

About 88 percent of geologic time is represented by the time span called the ________ era.

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

Question 68

The era of "ancient life" is the ________ era.

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

Question 69

The radioactive isotope,potassium-40,has argon-40 as a daughter product.

Question 70

Which of the following denotes the divisions of the geologic time scale in correct order of decreasing lengths of time beginning with the longest time interval and ending with the shortest?

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

Question 71

In the last few years improvements in technology have allowed geologists to date single grains of some minerals in rocks.A geologist separates 5 grains of the mineral zircon,which can be dated by the Uranium-lead method,and the crystal retains parent and daughter through weathering,erosion,and deposition.Thus,dating each mineral grain only gives the age of the source rock that was eroded,to produce that sand,from which the zircon grain is derived.The 5 grains yield ages of 160,110,2020,66,and 162 million years.What do these ages tell you about the age of the sedimentary strata?

A)They are Precambrian rocks,older than 2020 million years.
B)They are between 160 and 162 million years.
C)They are younger than 66 million years.
D)There are no age constraints from this data; sedimentary rocks cannot be dated by geochronology.

Question 72

Different periods of the geologic time scale are different in length.Why?

A)Early geologists made mistakes,but it was easier to retain the terminology in the time scale.
B)The time scale was developed ad hoc,as a relative time scale based on rocks and fossil succession with no reference to absolute time when it was developed.
C)The geologists who developed the time scale did not care about absolute ages.
D)None of the above

Question 73

An unconformity involving older metamorphic rocks and younger sedimentary strata is termed a nonconformity.

Question 74

When a beta particle is emitted,the mass number of the isotope remains unchanged.

Question 75

There is geologic evidence that the earth has experienced many episodes of mountain building and erosion.

Question 76

electron capture alpha emission delta capture beta emission

Question 77

Strata above an angular unconformity were tilted before the older strata were eroded.

Question 78

After three half-lives,one-ninth of an original radioactive parent isotope remains,and eight-ninths has decayed into the daughter isotope.

Question 79

The percentage of radioactive atoms that decay during one half-life is always the same.

Question 80

Paleozoic Mesozoic Phanerozoic Cenozoic