Deck 8: Geologic Time

Question 1

Sandstone strata and a mass of granite are observed to be in contact.Which of the following statements concerning their relative age is geologically 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)They were both formed at 4004 B.C.E.but the Devil made them complicated to fool us.

Answer 1

C

Question 2

Working on fossiliferous strata in the mountains of western Italy, ________ was first to work out ________, which is the fundamental way geologists know which bed is older in any sedimentary sequence.

A)James Hutton, the principle of uniformitarianism
B)Charles Lyell, the sequence of orogenies
C)William Smith, the principle of fossil succession
D)Nicolaus Steno, the law of superposition

Answer 2

D

Question 3

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

A)strata typing
B)cross-cutting
C)radioactive intuition
D)correlation

Answer 3

D

Question 4

The study of paleontology focuses on ________?

A)fossils and evidence concerning ancient life forms
B)sedimentary rocks and their diagenetic transformations after deposition
C)absolute age determinations on minerals from igneous and metamorphic rocks
D)palinspastic restorations of deformed strata that were once horizontal

Question 5

Visualize (or draw)five, horizontal, sedimentary strata as 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 are true?

A)bed 5 is the oldest
B)beds 1 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 6

Pieces of one rock contained within another are called ________ and give evidence that that smaller rock is ________ the main body.

A)coprolites, rejects from
B)inclusions, older than
C)surprises, more valuable than
D)xenoliths, younger than

Question 7

Which of the following means to recognize, identify, and describe similar-aged strata or similar lithologies in nearby areas or in widely separated, different areas?

A)coagulation
B)correlation
C)strata-titling
D)fossicking

Question 8

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 supposition
C)law of superposition
D)theory of superstition

Question 9

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

A)Charles Edward Stuart, 17th century
B)William Smith, 18th century
C)George Dawson, 19th century
D)Nicolaus Steno, 17th century

Question 10

What geologic law/principle states that fossil organisms (fauna)changed and evolved in a definite, progressive way such that strata of specific ages can be recognized by the fossils they contain?

A)fossil exhibitionism
B)fossil superposition
C)fossil succession
D)fossil transubstantiation

Question 11

The task of matching geologic formations of the same age over vast distances (like between continents)is termed ________.

A)correlation
B)cross dressing
C)lithification
D)stratification

Question 12

An unconformity is ________.

A)an erosional (or non-depositional)surface with younger strata above and older rocks below
B)the lower contact of an intrusive sill with sedimentary strata
C)a fault with younger, sedimentary rocks above and older, igneous rocks below
D)the contact between a cross-cutting pluton and sedimentary rocks

Question 13

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 dyke of basalt intruding a sandstone
C)the feldspar and quartz contents of a granite
D)an nonconformity between a granite and sandstone

Question 14

Which rocks are most useful in unraveling Earth's geologic history?

A)phaneritic igneous rocks
B)high grade metamorphic rocks
C)fossiliferous sedimentary rocks
D)meteorites

Question 15

Which of the following statements is true, concerning sedimentary strata separated by a disconformity?

A)The younger strata were tilted after the older strata were.
B)All strata exhibit parallel bedding or stratification, but there is a hiatus (missing record).
C)The older strata were tilted when the younger strata were deposited.
D)All of the older strata were eroded away before the younger strata were tilted.

Question 16

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 uniquely 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 17

An unconformity is a buried ________.

A)fault or fracture with older rocks above and younger rocks below
B)surface of erosion or non-deposition 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 18

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

A)An angular deformity
B)An angular unconformity
C)A disconformity
D)A cross-cutting fault

Question 19

Which English engineer and amateur geologist (his first name was William)is generally credited with first demonstrating the principle of faunal succession from his observations in building canals?

A)Tell
B)Smith
C)Wordsworth
D)Blake

Question 20

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)Igneous dykes cutting through sills at an angle.

Question 21

In radiometric dating, an unstable radioactive isotope is called ________.

A)an alpha particle
B)the parent
C)a red hot mama
D)a tachyon

Question 22

How can radiometric dating yield reliable values for the ages of minerals, rocks and some fossils?

A)The decay constants are fixed and well measured for isotopic decay.
B)One only needs to analyse for the parent isotope.
C)The physical conditions that control decay, like temperature and pressure, are always well known.
D)There are absolute fossil ages to compare to and test the radiometric clocks.

Question 23

The radioactive isotopes uranium-238, uranium-235, and thorium-232 eventually decay to different, stable, daughter isotopes of ________.

A)iron
B)argon
C)strontium
D)lead

Question 24

Which type of microfossils have tests (hard parts)made of calcium carbonate and are useful as index fossils as well as for measuring past sea temperatures and climates since the Cretaceous?

A)acritarchs and dinoflagellates
B)coccoliths and formaminifera
C)conodonts
D)diatoms and radiolaria

Question 25

Of an original amount of radioactive parent isotope, 25% remains and 75% has decayed.How many half-lives have elapsed?

A)2)0
B)0)5
C)1)5
D)3)0

Question 26

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 span of geologic time but was very widespread.
C)The fossils are exceptionally abundant for a long time span and readily preserved.
D)The fossils occur in deep-water marine sediments, but the organism actually lived in the sunlit, surface layer of the ocean.

Question 27

What gas is a radioactive daughter product of the U-238 decay series?

A)xenon-143
B)carbon-14
C)radon-226
D)argon-40

Question 28

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

A)540 billion years
B)4)6 million years
C)4)6 billion years
D)about 4600 thousand years

Question 29

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)1-2
B)<1
C)>3
D)2-3

Question 30

Which type of microfossils have a tooth-like shape made of apatite, are a mouth part of an extinct swimming eel-like chordate, and are useful index fossils for the Paleozoic through Triassic?

A)acritarchs and dinoflagellates
B)coccoliths and formaminifera
C)conodonts
D)diatoms and radiolaria

Question 31

Which organisms were free swimmers and found in a great variety of Paleozoic and Mesozoic marine habitats?

A)ammonoids and conodonts
B)chitnozoans and graptolites
C)diatoms and diatoms
D)flatclams and trilobites

Question 32

The ratio of radioactive parent to stable daughter atoms in a mineral is measured as 1:3.How many half-lives have elapsed since the mineral grain formed, assuming that only parent atoms were present when it crystallized?

A)2)0
B)0)5
C)3)0
D)1)5

Question 33

Assume that human 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 34

Both long-lived, naturally occurring, uranium isotopes decay through a series of intermediate, radioactive, daughter isotopes to stable isotopes of ________.

A)carbon
B)thorium
C)radon
D)lead

Question 35

Why is the major branch of the K-40 decay to Ca-40 not useful in most cases for whole rock dating?

A)It only works 89% of the time.
B)The Ca-40 that is produced by decay is indistinguishable from the naturally most abundant isotope of Ca that may have been present initially.
C)The decay to Ar-40 is faster and has wider geologic applicability.
D)Ca-40 is itself unstable and further decays to more daughter products.

Question 36

Acritarchs, conodonts, graptolites and trilobites would all be useful as index fossils, environmental indicators, or relative dating tools for ________.

A)Cretaceous through Eocene aeolian deposits
B)Cenozoic conglomerates
C)Mesozoic coals
D)Paleozoic marine shales and carbonates

Question 37

How can fossiliferous sedimentary rock most easily be dated and correlated if they lack the most diagnostic index fossil for that period or epoch?

A)by performing radiometric dating like U-238/Pb-206 or C-14 on fossils
B)by using the entire fossil assemblage and ranges for the two localities in question
C)by mapping out the intervening contacts or drilling a series of boreholes between
D)by paying a geologist to tell you the answer

Question 38

Which type of microfossils are organic walled cysts of planktonic algae primarily used in relative dating?

A)acritarchs and dinoflagellates
B)coccoliths and formaminifera
C)conodonts
D)diatoms and radiolaria

Question 39

Which of the following denotes remains of particular organisms that were widely distributed, but lived for only a relatively brief interval of geologic time?

A)internal moulds
B)fleeting impressions
C)index fossils
D)eratosthenes

Question 40

Which organisms were benthic (bottom dwellers)and extensively used as index fossils respectively for the Mesozoic and Lower Paleozoic?

A)ammonoids and conodonts
B)chitnozoans and graptolites
C)diatoms and diatoms
D)flatclams and trilobites

Question 41

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)animals
D)ancient

Question 42

Which of the following does not have at least one, very long-lived, natural, radioactive isotope?

A)Th; thorium
B)Ca; calcium
C)Rb; rubidium
D)K, potassium

Question 43

The rare element iridium has been implicated in which "ancient health" crisis?

A)poisoning of primitive algae in the Hadean Eon
B)extinction of the woolly mammoths in late Pleistocene time
C)disappearance of Neanderthal man during the early Cenozoic Era
D)extinction of the dinosaurs at the end of the Cretaceous Period

Question 44

What is the Jurassic Period named after?

A)Jura Mountains between France and Switzerland
B)the Jurassic Park movies
C)19th century Canadian geologist Sir William Jurass
D)a moon of Saturn

Question 45

Complex, invertebrate, life forms are common as fossils, beginning with marine strata of Cambrian age.How long ago did the Cambrian Period begin?

A)4)6 billion years
B)66 million years
C)541 million years
D)541 billion years

Question 46

The Phanerozoic Eon comprises approximately the ________ of geologic time.

A)last 15%
B)first 85%
C)last 85%
D)first 15%

Question 47

The name of which geologic era means "ancient life"?

A)Phanerozoic
B)Proterozic
C)Paleozoic
D)"Geezer-cene"

Question 48

A few rare times in earth history the majority of life forms disappeared "clearing the ecologic slate" for new ones.When this happens it is called ________.

A)an ecoshift
B)a half life
C)an iridium anomaly
D)a mass extinction

Question 49

What kind of materials can be reliably dated by the C-14 method?

A)biotite, hornblende, and muscovite; particularly in Mesozoic and older rocks
B)Recent: clams, foraminifera, and wood <50,000 years old
C)Paleozoic oil and gas deposits in limestones
D)Precambrian zircons in igneous and metamorphic rocks

Question 50

Which of the following is the name of an eon in the geologic time scale?

A)Cretaceous
B)Eocene
C)Phanerozoic
D)Paleozoic

Question 51

At the end of the Cretaceous (K/T boundary)what unusual geologic phenomenon occurred that has been linked to mass extinction and the end of the dinosaurs?

A)A 10 kilometre diameter meteor impact occurred on the Yucatan peninsula.
B)Enormous outpourings of basaltic lavas built the Rocky Mountains in British Columbia.
C)The climate abruptly warmed and massive weathering of iridium poisoned the seas
D)Dinosaurs were hunted to extinction by Klingons.

Question 52

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 53

What is the source of natural carbon-14?

A)nuclear fission of the heavy, radioactive elements uranium and thorium
B)fusion of hydrogen and helium in the Sun and eruption of solar flares
C)leakage of radioactive gases from the liquid, outer core
D)cosmic ray collisions triggering "neutron-capture" in ordinary atmospheric nitrogen

Question 54

Why are the successive periods and epochs of the geologic time scale of unequal lengths?

A)The passage of time has been speeding up and the length of the day is variable.
B)It is based on evolution and some creatures are slow learners.
C)The periods and epochs are based on the duration of unique environments like basins, or events in earth history like extinctions, and orogenies which happen intermittently.
D)They were originally all of equal duration but most of them got eroded and are full of unconformities.

Question 55

The half-life of carbon-14 is about 5730 years.Assume that a sample of charcoal formed by burning wood that lived 25,000 years ago.How much of the original carbon-14 would remain today?

A)1/16 to 1/32
B)1/2 to 1/4
C)1/4 to 1/8
D)1/8 to 1/16

Question 56

Which geologic eon denotes the first 800 million years of Earth history?

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

Question 57

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 58

Which two Paleozoic, geologic, time-scale periods used in the United States are combined into the Carboniferous period in Europe and elsewhere?

A)Triassic; Jurassic
B)Cambrian; Ordovician
C)Permian; Pennsylvanian
D)Mississippian; Pennsylvanian

Question 59

The half-life of carbon-14 is about 5730 years.Assume that a sample of charcoal formed by burning wood that lived 15,000 years ago.How much of the original carbon-14 would remain today?

A)1/4 to 1/8
B)>1/2
C)1/2 to 1/4
D)1/8 to 1/16

Question 60

While the Precambrian represents 88% of Earth's history, it is not divided into periods or epochs like the Phanerozoic because there ________.

A)are few remaining Precambrian rocks to correlate or divide due to active tectonics
B)are no Precambrian sedimentary rocks to use for internal divisions
C)were no multi-cellular organisms nor hard-bodied fauna to leave much of a fossil record
D)are few resources in Precambrian rocks and few geologists take an interest in them

Question 61

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

Question 62

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

Question 63

An isotope's mass is equal to the sum of its protons and neutrons in its nucleus.

Question 64

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

Question 65

Monotids and inoceramids are planktonic microfossils useful for zoning the Cenozoic Era.

Question 66

Correlation of rock units between continents or widely separated areas is accomplished by using physical features such as colour, texture, and thickness of units.

Question 67

Uranium has two, long-lived, radioactive isotopes, U-238 and U-235.

Question 68

In relative dating, the principle of cross-cutting relationships allows one to infer that the rock body that does the cutting is clearly older.

Question 69

Benthic foraminifera are useful for correlation and dating of Paleozoic through Recent marine sedimentary rocks.

Question 70

Paleophrenology is the study of fossils and ancient life forms.

Question 71

The radioactive decay of U-238 to Pb-206 is slightly faster in hot magmas than in cool, solidified rock.

Question 72

The Earth is billions of years old and its surface and interior have changed repeatedly by the same processes still operating today.

Question 73

James Hutton was the very first geologist to recognize the vast amount of missing time (at least all of Silurian)represented by the angular unconformity where the gently dipping Devonian "Old Red Sandstone" overlies vertical Ordovician slates at Siccar Point, Scotland.

Question 74

Unconformities often mark times of uplift and erosion.

Question 75

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

Question 76

Pebbles of granite in sandstone and conglomerate resting on the granite suggest that the granite intruded the sedimentary beds.

Question 77

Carbon-14 is produced by cosmic rays reacting with nuclei of iron atoms in the Earth's core.

Question 78

Phanerozoic, marine, sedimentary strata of the same age on different continents can usually be correlated by their fossil assemblages.

Question 79

Carbon-14 is very helpful for dating geologic events from the beginning of the Paleocene Epoch until the present.

Question 80

Carbon-14 can be used to date wood and other natural organic materials used by aboriginal peoples of North and South America.