Deck 23: Geologic Time - Reading the Rock Record

Question 1

Deposition of sediment with each new layer younger than the layer below illustrates the principle of

A)original horizontality.
B)superposition.
C)nonconformity.
D)horizontality and nonconformity.

Answer 1

B

Question 2

An eroded surface of metamorphic rocks on which a horizontal bed rests is called a

A)strata.
B)dike.
C)nonuniform surface.
D)nonconformity.

Answer 2

D

Question 3

The principle of superposition states that the top layer of rock is

A)igneous.
B)the youngest.
C)sedimentary.
D)the oldest.

Answer 3

B

Question 4

Fossils are found in

A)sedimentary rocks.
B)metamorphic rock.
C)igneous rocks.
D)sedimentary and some metamorphic rocks.

Question 5

Which relative dating principle states that in an undeformed sequence of sedimentary rocks,each layer is older than the one above and younger than the one below?

A)original horizontality
B)superposition
C)cross-cutting
D)inclusion

Question 6

When comparing geologic time to a calendar year,the time of the dinosaurs is in the

A)middle of October.
B)first half of December.
C)second half of December.
D)first half of February.

Question 7

A surface of erosion between rocks that represents a gap in Earth history is

A)called a dike.
B)an unconformity.
C)a faunal conformity.
D)none of the above

Question 8

An assumption that Earth processes occurring today have always occurred is called

A)the principle of superposition.
B)uniformitarianism.
C)the principle of original horizontality.
D)theory of unconformity.

Question 9

In a sequence of rock layers we find trilobite fossils at the bottom of the rock sequence and dinosaur fossils directly above the trilobite fossils.We conclude that

A)trilobites survived up to the time of the dinosaurs.
B)the beds are overturned.
C)the processes of erosion created a gap between the age of trilobites and the age of dinosaurs.
D)dinosaurs fed on trilobites.

Question 10

The theory that different forms of animals throughout Earth's past occurred in a definite order is called the principle of

A)fossil assemblage.
B)faunal succession.
C)conformable fossils.
D)fossil determination.

Question 11

In a sequence of rock layers we find trilobite fossils at the bottom of rock layer 1 and dinosaur fossils directly above the fossil trilobites in layer 2.There are inclusions of trilobites in layer 2.We conclude that

A)dinosaurs were extinct long before trilobites came into existence.
B)dinosaurs are from the Cambrian Period.
C)by inclusion and faunal succession,layer 1 is older than layer 2.
D)there is no time gap between the rocks.

Question 12

An unconformity is

A)a scientific debate between Earth scientists.
B)when younger igneous plutonic rocks are above older sediments.
C)a continuous sequence of sedimentary layers.
D)a gap in an otherwise continuous time-sequence of rock layers.

Question 13

Sediments deposited in an even,horizontal manner illustrate the principle of

A)superposition.
B)original horizontality.
C)succession.
D)conformity.

Question 14

The principle of faunal succession states that

A)fossil organisms follow one another in a definite,irreversible time sequence.
B)rock cycling may dislodge and relocate fossils,making their age difficult to determine.
C)fossils are always older than the rock in which they are found.
D)fossils are ordained.

Question 15

Conditions for the preservation of fossils are best achieved

A)in desert environments.
B)in glaciated environments.
C)in shallow river beds.
D)on the floors of shallow seas.

Question 16

The principle of original horizontality states that each

A)sedimentary layer is older than the layer above.
B)sedimentary layer is younger than the layer above.
C)new layer of sediment is laid down nearly horizontally over older sediment.
D)new layer of sediment is laid down accordingly.

Question 17

An unconformity can be interpreted as

A)an occurrence of radioactive decay.
B)repeated intrusions of igneous rock.
C)a buried surface of erosion.
D)the result of repeated volcanic action.

Question 18

In a thick bed of sedimentary rocks we find an igneous dike.The order of formation is

A)together.
B)igneous before sedimentary.
C)sedimentary before igneous.
D)unknown.

Question 19

In a sequence of rock layers we find trilobite and dinosaur fossils.The dinosaur fossils are at the bottom of the rock sequence and the trilobites are at the top.This sequence tells us that

A)dinosaurs are older than trilobites.
B)the beds are overturned.
C)trilobites survived the age of the dinosaurs.
D)the beds are folded.

Question 20

In any sequence of sedimentary rock layers that have not been subjected to stress,you would expect to find

A)horizontal layers.
B)older layers at the bottom and younger layers at the top.
C)fossils in the bottom layers and inclusions in the upper layers.
D)older horizontal layers at the bottom with younger horizontal layers at the top.

Question 21

Walking along a dry river bed,you find a conglomerate rock.What can you say about the rock's relative age?

A)The rock formed in place,at the river bed.
B)The rock and mineral fragments that make up the rock are older than the actual rock.
C)The rock is relatively young since it contains lots of small rock fragments.
D)The rock and mineral fragments that make up the rock are younger than the actual rock.

Question 22

On what four assumptions is the principle of faunal succession based?

Question 23

In a sequence of sedimentary rocks,the bottom layer is the youngest and the top layer is the oldest.This type of sequence suggests that the

A)principles of original horizontality and superposition are flawed.
B)beds must have been overturned by some structural disturbance.
C)dates for these rocks must be in error.
D)principles of original horizontality and superposition hold true.

Question 24

To help determine the age of rock layers over a large area we can use the principle of

A)original horizontality.
B)lateral continuity.
C)superposition.
D)fossil assemblage.

Question 25

Fossils can be used to determine the relative age of rock layers because they are

A)found in a definite order.
B)deposited horizontally,one fossil at time.
C)radioactive.
D)found in sedimentary rocks.

Question 26

The five principles used to determine the relative ages of rock include original

A)horizontality,superposition,cross cutting,inclusion,and faunal succession.
B)horizontality,nonconformity,cross cutting,inclusion,and faunal succession.
C)inclusion,superposition,uniformitarianism,horizontality,and fossil succession.
D)horizontality,uniformitariansism,cross cutting,stromatolite,and faunal succession.

Question 27

Who established the principle of faunal succession?

A)Alfred Wegener.
B)Harry Hess.
C)William "Strata" Smith.
D)Andrija Mohorovicic.

Question 28

What types of rocks are representative of the principle of original horizontality? Why?

Question 29

What type of igneous formation would agree with the principle of superposition?

Question 30

According to most estimates,Earth is approximately

A)4.5 thousand years old.
B)4.5 million years old.
C)4.5 billion years old.
D)45 billion years old.

Question 31

What does the principle of superposition say about the ages of rocks?

Question 32

The ordering of rocks in sequence by their comparative ages is called

A)faunal succession.
B)original horizontality.
C)relative dating.
D)uniformitarianism.

Question 33

How do geologists determine the relative ages of different rocks?

Question 34

The laws of physics,chemistry,and geology have operated unchanged through time to shape Earth as we know it today.This statement can be summed up by the idea of

A)evolution.
B)everlasting change.
C)uniformitarianism.
D)natural history.

Question 35

When tilted or folded sedimentary layers are covered by younger,horizontal rock layers it is called

A)an intrusion.
B)an angular unconformity.
C)a syncline.
D)conformable.

Question 36

In a sedimentary rock that contains inclusions of metamorphic rock,the inclusions must be

A)older than the sedimentary rock.
B)younger than the sedimentary rock.
C)on top of the sedimentary rock.
D)below the sedimentary rock.

Question 37

The idea of uniformitarianism suggests that

A)the natural laws that operate today are different than those that have operated in the past.
B)sediments are laid down layer upon layer with younger layers always on the top.
C)the processes and natural laws that operate today have been valid throughout geologic time.
D)all rocks layers are originally uniform.

Question 38

If we compress 4.5 billion years into a calendar year,humans make their mark on the calendar

A)the very last minute of New Years Eve.
B)on December 25^th.
C)at 12:00 pm,December 30^th.
D)at 11:50 pm,December 31^st.

Question 39

Relative dating tells us the

A)time gaps that occur during deposition.
B)age of rock layers.
C)sequence of rock layers-which formed first,second,and last.
D)actual date of formation for a rock layer.

Question 40

The rather simple idea that,unless disturbed,younger sedimentary layers overlie older layers,is referred to as the principle of

A)original horizontality.
B)uniformitarianism.
C)faunal succession.
D)superposition.

Question 41

Radiometric dating assumes that,once a mineral has crystallized,any daughter product results only from the decay of the original unstable parent.Some complications are

A)variations in temperature.
B)failure to take samples too close together.
C)"time clock resetting" due to metamorphism,and product leakage that yields false age estimation.
D)a poorly maintained teleometer.

Question 42

The numerical dates associated with events on the geologic time scale were determined by

A)relative dating.
B)superposition.
C)radiometric dating.
D)fossil assemblages through time.

Question 43

To date relatively young rocks and materials,we use the decay of

A)uranium-238 to lead-206.
B)potassium-40 to argon-40.
C)carbon-14 to nitrogen-14.
D)uranium-235 to lead-207.

Question 44

If a radioactive element has a half-life of 704 million years,and the amount of parent material remaining is one-eighth of the original amount,the specimen is about

A)2,112,000,000 years old.
B)1,408,000,000 years old.
C)2,816,000,000 years old.
D)3,520,000,000 years old.

Question 45

The oldest rocks that have been dated by radioactivity are approximately

A)2 million years old.
B)200 million years old.
C)4 billion years old.
D)10 billion years old.

Question 46

By radiometric dating,the oldest mineral in a sedimentary rock was found to be 1.4 million years old.What is the age of the sedimentary rock?

A)1.4 million years
B)no older than 1.4 million years
C)no younger than 1.4 million years
D)Radiometric dating does not work for sedimentary rocks.

Question 47

To date the age of Earth,we look for rocks with a high percentage of

A)uranium-235 to lead-207.
B)uranium-238 to lead-206.
C)potassium-40 to argon-40.

Question 48

The resetting of a mineral's time clock means that

A)a mineral can be formed and reformed again and again.
B)the date obtained will be the date of the metamorphic event,not the date of the rock's formation.
C)the date obtained will be the date of the rock's formation,not the date of the metamorphic event.
D)minerals can tell time just like a clock can tell time.

Question 49

To date a rock thought to be many millions of years old,you should not use the decay of

A)uranium to lead.
B)potassium to argon.
C)carbon-14.

Question 50

The process where an element spontaneously changes into a different element (transmutation)by a change in the nucleus of an atom is called

A)radiometric dating.
B)radioactive decay.
C)radiometric decay.
D)none of these

Question 51

The isotope most useful for dating rocks from the late Pleistocene is

A)uranium-238.
B)uranium-235.
C)potassium-40.
D)carbon-14.

Question 52

In radioactive decay,when the parent material decays to one-quarter of its original amount,the time is

A)one half-life.
B)two half-lives.
C)three half-lives.
D)four half-lives.

Question 53

Radiocarbon dating is limited to the remains of plants and animals that died no longer than about

A)100 years ago.
B)5700 years ago.
C)40,000 years ago.
D)1,000,000 years ago.

Question 54

Radiometric dating is based on

A)decay of uranium-238 to lead-206.
B)sequence of rocks and the relative position of one layer to another.
C)proportions of radioactive isotopes and their decay products.
D)the half-life of radioactive atoms.

Question 55

The time required for one-half of a radioactive material to decay is called the

A)absolute age.
B)half-life.
C)date age.
D)true-life.

Question 56

The ultimate truth of any radiometric date depends on the

A)size of the given sample.
B)chemical composition of the sample being tested.
C)precision and accuracy of the lab techniques.
D)reset date of the sample.

Question 57

If the half-life of some radioactive element is 1 billion years,and a mass of rock originally contained 100 g of that element,how many grams of the radioactive element would be left after three billion years had passed?

A)6.25 g
B)12.5 g
C)25 g
D)50 g
E)none

Question 58

Granitic pebbles with a radiometric age of 300 million years are embedded in a sedimentary rock.A dike,dated at 200 million years,intrudes into the sedimentary rock.With all this information we can estimate the age of the sedimentary rock to be

A)older than 300 million years.
B)younger than 200 million years.
C)between 200 and 300 million years old.
D)precisely 300 million years old.

Question 59

In radioactive decay,when the parent material decays to one-half of its original amount,the time is

A)one half-life.
B)two half-lives.
C)three half-lives.
D)four half-lives.

Question 60

If a radioactive element has a half-life of 5760 years,and the amount of parent material remaining is one-fourth of the original amount,the specimen is about

A)11,520 years old.
B)17,280 years old.
C)23,040 years old.
D)28,800 years old.

Question 61

During the Precambrian,the development of the ozone layer helped

A)primitive organisms on Earth's surface to nucleate.
B)shield Earth's surface from harmful ultraviolet radiation.
C)promote the emergence of stromatolites.
D)promote the development of anaerobic organisms.

Question 62

A radiometric date is determined from mica that has been removed from a rock.What does the date signify if the mica is found in granite? What does the date signify if the mica is found in schist?

Question 63

The oldest known fossils are

A)trilobites and brachiopods.
B)algae and bacteria.
C)fungi and algae.
D)worms and jellyfish.

Question 64

The Precambrian witnessed the development of

A)the first atmosphere.
B)the ozone layer.
C)photosynthesis.
D)photosynthesis,an oxygenated atmosphere,and the ozone layer.

Question 65

Earth's first atmosphere was rich in water vapor but poor in free oxygen.The atmosphere became more oxygenated with the

A)development of the ozone layer.
B)emergence of stromatolites that developed a simple version of photosynthesis.
C)emergence of gases from volcanic eruptions.
D)both A and B.

Question 66

Which of the following is not true of the fossil record?

A)The fossil record spans 3 billion years of Earth's 4.6 billion year age.
B)The most common fossils are from organisms that had hard parts like shells and bones.
C)Similar to present day stromatolites,the first fossils were simple,anaerobic algal plants.
D)The Paleozoic era is credited with the emergence of life.

Question 67

From first to last,name the eons on the Geologic Time Scale.

A)Phanerozoic,Proterozoic,Archean,Hadean.
B)Hadean,Archean,Proterozoic,Phanerozoic.
C)Proterozoic,Phanerozoic,Hadean,Archean.
D)Precambrian,Phanerozoic,Proterozoic,Paleozoic.

Question 68

In dating a mineral,what is meant by "resetting of the mineral's time clock"?

Question 69

The geologic time scale is broken up into time units of different sizes based on

A)eons,eras,periods,and epochs.
B)changes in fossilization.
C)visible and nonvisible life forms.
D)major changes in life forms.

Question 70

What are some of the uncertainties in obtaining radiometric carbon dates?

Question 71

Why are periods the most fundamental time unit?

Question 72

What are the limitations in obtaining radiometric dates?

Question 73

Life forms in the Precambrian included

A)trilobites.
B)brachiopods.
C)coelacanths.
D)cyanobacteria.

Question 74

Life forms in the Precambrian include

A)trilobites,brachiopods and stromatolites.
B)cyanobacteria and trilobites.
C)the agnatha and the coelacanths.
D)stromatolites and certain primitive blue-green algae.

Question 75

The oldest known fossils of single-celled organisms are

A)4.6 billion years old.
B)3.9 billion years old.
C)3.3-3.5 billion years old.
D)1.3-1.5 billion years old.

Question 76

Which isotopes are most appropriate for dating formations from the following ages: (a)the early Precambrian; (b)the Mesozoic; (c)the late Pleistocene?

Question 77

The banded iron formations began to form when

A)carbon dioxide dissolved in seawater.
B)varying oxygen levels allowed the precipitation of alternating layers of iron oxide.
C)oxide minerals were deposited on the ocean bottom.
D)iron from lava flows settled into layered formations.

Question 78

Development of Earth's early oceans was likely due to

A)water-rich meteors bombarding Earth's surface.
B)volcanic outgassing in Precambrian time.
C)intense convection in the mantle,and severe heat dissipation from Earth's interior.
D)cooler temperatures that promoted the condensation of water vapor in the atmosphere.

Question 79

The fundamental time unit representing a major change in life forms is the

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

Question 80

On the Geologic Time Scale,the time unit representing the largest span of time is the

A)Phanerozoic.
B)Precambrian.
C)Proterozoic.
D)Mega-annum.