Lesson 3 | Absolute-Age Dating
Student Labs and Activities
Page
Appropriate For:
Launch Lab
46
all students
Content Vocabulary
47
all students
Lesson Outline
48
all students
MiniLab
50
all students
Content Practice A
51
Content Practice B
52
Math Skills
53
all students
School to Home
54
all students
Key Concept Builders
55
Enrichment
59
Challenge
60
Lab A
63
Lab B
66
Lab C
69
Chapter Key Concepts Builder
70
all students
Assessment
Lesson Quiz A
61
Lesson Quiz B
62
Chapter Test A
71
Chapter Test B
74
Chapter Test C
77
Approaching Level
On Level
Beyond Level
Teacher evaluation will determine which activities to use or modify to meet any
Clues to Earth’s Past
English-Language Learner
student’s proficiency level.
45
Name
Date
Launch Lab
Class
LESSON 3: 10 minutes
How can you describe your age?
If you described your relative age compared to your classmates’, how would you do it?
How do you think your actual, or absolute, age differs from your relative age?
Procedure
1. One student, chosen at random by
your teacher, will write down his or her
birth date on an index card. The
student will hold the card while
everyone else files by and looks at it.
3. Remaining in your group, write down
your own birth date on an index card.
Quietly form a line in order of your
birth dates.
2. Form two groups depending on
whether your birth date falls before or
after the date on the card.
Think About This
1. When you were in two groups, what did you know about everyone’s age? When you
lined up, what did you know about everyone’s age? Which is your relative age? Your
absolute age?
2. Can you think of a situation where it would be important to know your absolute age?
3.
Key Concept Why do you think scientists would want to know the absolute age
of a rock?
46
Clues to Earth’s Past
Name
Date
Class
Content Vocabulary
LESSON 3
Absolute-Age Dating
Directions: On each line, write the term from the word bank that correctly replaces the underlined words in each
sentence. NOTE: You may need to change a term to its plural form.
absolute age
half-life
isotope
mineral
radioactive decay
1. Salt is a(n) naturally occurring, inorganic solid with a
definite chemical composition and an orderly
arrangement of atoms.
2. My friend’s youngest sibling is a toddler. Her age in
numbers is three years.
3. C-12 and C-14 are atoms with different numbers of
neutrons, but both are made of carbon.
4. For uranium-235, the length of time after which half of
the parent isotopes decay is 704 million years.
5. Elements that are used to determine the absolute age of
rocks are those elements that undergo a process in
which atoms of the element change into atoms of
another element that is stable.
Clues to Earth’s Past
47
Name
Date
Class
Lesson Outline
LESSON 3
Absolute-Age Dating
A. Absolute Ages of Rocks
1. The numerical age, in years, of any object is its
a.
.
can be used to help determine the absolute age
of rocks.
b. Radioactivity is the release of energy from
.
B. Atoms
1. A(n)
is the smallest part of an element that has the
properties of that element.
a. An atom contains protons and neutrons in its
b. Atoms also have
.
, which surround the nucleus.
2. All atoms of a specific element contain the same number
of
.
a. Nuclei of atoms of the same element can contain different numbers
of
.
b. Atoms of the same element that contain different numbers of neutrons are
called
.
3. An isotope that does not change under normal conditions is said to
be
.
a. Isotopes that are not stable are
isotopes.
b. During
, an unstable element naturally changes into
an element that is stable.
c. The element that undergoes radioactive decay is called
the
.
d. The element formed by radioactive decay is called
the
48
.
Clues to Earth’s Past
Name
Date
Class
Lesson Outline continued
4. Different radioactive isotopes decay at different rates, but the decay rate is
for each specific isotope.
a. For each radioactive isotope, the
is the time
necessary for half of the parent isotopes to decay into daughter isotopes.
b. After two half-lives,
of the original parent isotopes
remain.
C. Radiometric Ages
1.
dating uses isotopes of carbon-14 to determine the age
of once-living organisms.
a. As long as an organism lives, the amount of carbon-14 it contains
is
.
b. Radiocarbon dating involves comparing the amount of carbon-14 to the amount
of
in an organism that has died.
c. The half-life of carbon-14 is
years.
d. About
years after an organism has died, the
carbon-14 has decayed so much that it cannot be measured.
2. Because carbon-14 is useful only for dating materials that are organic, it cannot be
used to date
.
a. Radioactive isotopes are most likely to be trapped in
rocks, which means they can be dated by comparing numbers of parent and
daughter isotopes.
b. Radioactive isotopes are not very useful in dating
rocks, because they are composed of grains of older rock.
c. To date old rocks, scientists use radioactive isotopes with
half-lives.
d. The age of the oldest rocks on Earth put Earth’s age at more than
4
Clues to Earth’s Past
years.
49
Name
Date
MiniLab
Class
LESSON 3: 10 minutes
What is the half-life of a drinking straw?
You can model half-life with a drinking straw.
Procedure
1. Read and complete a lab safety form.
2. On a piece of graph paper, draw an
x-axis and a y-axis. Label the x-axis
Number of Half-Lives, from 0 to 4 in
equal intervals. Leave the y-axis blank.
3. Use a metric ruler to measure a
drinking straw. Mark its height on
the y-axis, as shown in the photo in
your textbook. Use scissors to cut the
straw in half and discard half of it.
Mark the height of the remaining half
as the first half-life.
4. Repeat four times, each time cutting
the straw in half and each time adding
a measurement to your graph’s y-axis.
Analyze and Conclude
1. Compare your graph to the graph in Figure 16 in your textbook. How is it similar?
How is it different?
2.
Key Concept Explain how your disappearing straw represents the decay of a
radioactive element.
50
Clues to Earth’s Past
Name
Date
Class
Content Practice A
LESSON 3
Absolute-Age Dating
Directions: Label this diagram by writing the letter of the statement that explains each isotope on the lines
provided.
Flowchart of Radioactive Decay
Unstable hydrogen-3
Nucleus
1.
Stable helium-3
nucleus
2.
Stable helium-3
nucleus
3.
A. When the neutron decays, energy is released.
B. The extra neutron decays, and a stable element forms.
C. The extra neutron makes the atom unstable.
Directions: On the line before each statement, write T if the statement is true or F if the statement is false.
4. The absolute age of a rock is its numerical age.
5. Atoms of an element that have the same number of protons but different
numbers of neutrons are called isotopes.
6. In radioactive decay, a stable element changes to an unstable element.
7. The unstable isotope that decays is called the daughter isotope.
8. The half-life of an isotope is the time it takes to become 50 percent parent
isotope and 50 percent daughter isotope.
9. Radiocarbon dating is useful for dating organic material.
10. Radiometric dating is most useful for dating sedimentary rock.
Clues to Earth’s Past
51
Name
Content Practice B
Date
Class
LESSON 3
Absolute-Age Dating
Directions: Answer each question on the lines provided.
1. What is meant by the absolute age of rock?
2. What is an isotope?
3. What happens to unstable isotopes?
4. What happens during radioactive decay?
5. What is half-life?
6. What is radiocarbon dating?
7. Which rock is radiometric dating most useful with? Why?
52
Clues to Earth’s Past
Name
Date
Class
Math Skills
LESSON 3
Use Significant Digits
The answer to a problem cannot be more precise than the numbers used in the calculation.
For example, here are the masses of two objects.
123.6 g
135 g
The first measurement has four significant digits, and the second measurement has three.
When you add to find the total mass, the sum must be rounded to show only three
significant digits.
123.6 g + 135 g = 258.6 g, which rounds to 259 g.
Round up if the last digit is 5 or more and round down if the last digit is less than 5. In this
example, the sum was rounded up to 259 g.
The half-life of rubidium-87 is 48.8 billion years. What is the length of 4 half-lives?
Step 1 Count the number of significant digits.
There are three significant digits in 48.8.
Step 2 Multiply.
48.8 × 4 = 195.2 billion years
Step 3 Round the product to three significant digits.
The length of 4 half-lives of rubidium-87 is 195 billion years.
Practice
1. The half-life of rubidium-87 is
48.8 billion years. What is the
length of 6 half-lives?
2. The half-life of potassium-40 is
1.25 billion years. What is the
length of 11 half-lives?
Clues to Earth’s Past
3. The half-life of potassium-40 is
1.25 billion years. What is the
length of 14 half-lives?
4. The half-life of radon-222 is 3.823 days.
What is the length of 4 half-lives?
53
Name
Date
School to Home
Class
LESSON 3
Absolute-Age Dating
Directions: Use your textbook to answer each question.
1. Geologists describe rocks and fossils using relative age and absolute age.
How is the relative age of a rock different from its absolute age?
2. Radioactive decay is the process by which an unstable element naturally
changes into another element that is stable.
Why is radioactive decay useful for determining the age of rocks?
3. Unstable parent isotopes change into stable daughter isotopes at a
constant rate.
Why is carbon dating not useful for determining the age of human artifacts that are
100,000 years old?
4. Most radiometric dating is carried out using igneous rocks.
Why is sedimentary rock not useful for conducting radiometric dating?
54
Clues to Earth’s Past
Name
Date
Key Concept Builder
Class
LESSON 3
Absolute-Age Dating
Key Concept What does absolute age mean?
Hydrogen
nucleus
Hydrogen-2
nucleus
Hydrogen-3
nucleus
Directions: Use the diagram to answer each question on the lines provided.
1. How are the forms of hydrogen shown in the diagram different?
2. How are the forms of hydrogen shown in the diagram the same?
Directions: Answer each question on the lines provided.
3. What is absolute age?
4. What is radioactivity?
5. What are atoms?
6. What does an atom contain?
7. What is an isotope?
8. Which method is more specific, relative-age dating or absolute-age dating? Why?
Clues to Earth’s Past
55
Name
Date
Class
Key Concept Builder
LESSON 3
Absolute-Age Dating
Key Concept How can radioactive decay be used to date rocks?
Directions: On each line, write the term from the word bank that correctly completes each sentence. Each
term is used only once.
atoms
constant
daughter
energy
half-lives
normal
one-half
parent
radioactive
radioactive decay
rates
stable
1. Most isotopes are
.
2. Under
conditions, isotopes do not change.
3. Unstable isotopes are known as
isotopes.
4. Unstable isotopes release
when they break down and form
new stable
.
5. The process by which an unstable element changes into another element that is stable
is called
.
6. Radioactive isotopes decay at different
.
7. For every given isotope, the rate of decay is
.
8. Rate of decay is measured in
.
9. Half-life for an isotope occurs when half of the parent isotopes have
become
isotopes.
10. By two half-lives, 25 percent of the isotopes are
isotopes.
11. By three half-lives, parent isotopes have changed to daughter isotopes by
another
56
.
Clues to Earth’s Past
Name
Date
Key Concept Builder
Class
LESSON 3
Absolute-Age Dating
Key Concept How can radioactive decay be used to date rocks?
Directions: On the line before each statement, write T if the statement is true or F if the statement is false.
1. Radioactive isotopes decay at a constant rate.
2. Radiometric dating involves measuring the difference between the amount
of parent isotope and daughter isotope.
3. The decay of radioactive isotopes is used to determine the size of the material
in which they are present.
4. One commonly used isotope for radioactive dating is hydrogen.
5. The ratio of C-14 to C-12 in the atmosphere is unpredictable.
6. Another name for radioactive carbon is C-14.
7. In carbon-14, there are six protons and eight neutrons in its nucleus.
8. Radiocarbons form when it mixes with C-8 in Earth’s upper atmosphere.
9. One element used by all living things to build tissue is carbon.
10. The ratio of C-14 to C-12 in the tissues of living organisms always changes.
11. The ratio of C-14 to C-12 in dead organisms stays the same.
12. One way to measure the passage of time is to determine the ratio of C-14 to
C-12 in dead organisms.
13. The half-life of uranium is 5,730 years.
14. Carbon is useful for dating remains that are more than 50,000 years old.
15. Radiometric dating must take place where the remains are discovered.
16. Radioactive dating uses an isotope of radon.
Clues to Earth’s Past
57
Name
Date
Class
Key Concept Builder
LESSON 3
Absolute-Age Dating
Key Concept How can radioactive decay be used to date rocks?
Directions: Complete this chart by writing how each fact relates to radiometric dating.
Fact
How It Relates to Radiometric Dating
Isotopes are trapped in
minerals.
1.
Minerals in igneous rocks
trap radioactive isotopes
when they form.
2.
Sedimentary rock is formed
from grains of a variety of
eroded rocks.
3.
Radiometric dating records
the age of the grains that
make up sedimentary rock.
4.
C-14 decays to form N-14
when organisms die.
5.
U-235 in igneous rock
decays to Pb-207, with a
half-life of 704 million years
6.
The half-life of rubidium-87
is 48.8 billion years. Its
daughter product is
strontium-87.
7.
The half-life of rubidium-87
is 48.8 billion years. Its
daughter product is
strontium-87.
8.
58
Clues to Earth’s Past
Name
Date
Class
Enrichment
LESSON 3
Ancient Mysteries and Carbon-14 Dating
When was Stonehenge built? How old
are the Dead Sea Scrolls? Scientists are able
to determine the ages of ancient artifacts
by measuring the residues of atomic
behavior.
In 1946 Willard F. Libby of the
University of Chicago developed a method
that determines the age of carboncontaining materials. The carbon atoms
in the materials can be used to determine
their ages, back to about 50,000 years.
Libby’s method, called radiocarbon dating,
earned him the Nobel Prize in Chemistry
in 1960.
Examples of How Carbon-14 Dating
Has Been Used
Tutankhamen (1323 B.C.)
An examination of mummified remains
revealed that this Egyptian child-king reigned
more than 3,300 years ago.
Stonehenge (3100 B.C.)
Carbon-14 dating of wood in the area
revealed that this circle of huge stones was
built by a group of prehistoric people who
lived in England 5,000 years ago.
How does it work?
Dating the Dead Sea Scrolls
Radiocarbon dating, or carbon-14
dating, is based on the fact that all living
matter contains carbon. Three isotopes
of carbon are present in living matter.
Carbon-12 and carbon-13 are stable
isotopes that have been around for a long
time. The other isotope, carbon-14, emits
beta (electron) radiation as it changes to
carbon-12 or carbon-13. The rate at which
carbon-14 changes is called the decay rate.
If the amount of carbon-14 in a piece of
material can be determined and the decay
rate for carbon-14 can be measured, then
the age of the material can be determined.
The decay rate for carbon-14 has been
established. Half of the existing carbon-14
atoms will decay in 5,730 years. Therefore,
5,730 years is the half-life of carbon-14.
A herdsman who was looking for a stray
goat in caves east of Jerusalem discovered
the first of the Dead Sea Scrolls in 1947. The
scrolls almost instantly sparked scholarly
controversy about when they were written.
Nearly 50 years later, the date of the scrolls
was settled by radiocarbon dating.
In 1994 researchers from the University
of Arizona dated 18 of the texts. The paper
from one of the texts dates to between
150 B.C. and 5 B.C. with a 95 percent
probability. The dates that the Arizona
team established confirmed the dates
determined by a lab in Zurich, Switzerland,
in 1990. The Arizona team took small
samples from the ragged edges of the
manuscripts and analyzed them using a
tandem accelerator mass spectrometer.
Using small samples of material, the
accelerator measures the amount of
carbon-14 in a substance.
Applying Critical-Thinking Skills
Directions: Respond to each statement.
1. Explain why radiocarbon dating cannot be used to determine the age of inorganic rocks.
2. Explain why carbon-14 dating cannot be used to determine the age of dinosaur bones.
Clues to Earth’s Past
59
Name
Date
Class
Challenge
LESSON 3
Radioactive Isotopes and Half-Lives
Half-life is a way of describing the rate of radioactive decay. One half-life is the amount
of time necessary for one-half of the nuclei in a sample to decay to a stable isotope. In other
words, a half-life is the lifetime of half of the radioactive isotope that is present in a system
at any given time. The half-life of carbon-14 in a sample is 5,730 years. In 5,730 years, there
will be half of the carbon-14 left in the sample. That remaining carbon-14 still has a halflife of 5,730 years. After 11,460 years, one-fourth the original amount of carbon-14 is in
the sample.
Different isotopes of elements have different half-lives. Examine the table below.
Radioactive Decay Rates
Parent Isotopes Daughter Isotopes
Half-Lives
carbon-14
nitrogen-14
5,730 years
Potassium-40
argon-40
1.28 billion years
uranium-238
lead-206
4.47 billion years
rubidium-87
strontium-87
48.8 billion years
Directions: Respond to each statement on the lines provided.
1. Explain how the radioactive decay of an element’s isotope can result in the isotope of
an entirely different element.
2. Predict what fraction of the original amount of potasium-40 will remain in a sample
after 3.84 billion years.
3. Assess the statement An isotope can never completely decay. Explain your reasoning.
60
Clues to Earth’s Past
Name
Date
Class
Lesson Quiz A
LESSON 3
Absolute-Age Dating
Multiple Choice
Directions: On the line before each statement, write the letter of the correct answer.
1. An absolute age of a rock is an age
A. in years.
B. based on fossils.
C. relative to another rock.
2. Isotopes are atoms of the same element with different numbers of
A. protons.
B. neutrons.
C. electrons.
3. During radioactive decay,
A. the amount of parent material increases.
B. the amount of daughter material increases.
C. the half-life of the parent material gets longer.
4. An absolute age of a mammoth bone could be determined using
A. carbon-14.
B. rubidium-87.
C. uranium-238.
5. Earth’s approximate age was determined using isotopes that have
A. very long half-lives.
B. low ratios of C-14 to C-12.
C. steep radioactive decay curves.
6. Radiometric methods provide accurate ages for
A. igneous rocks.
B. carbon-rich rocks.
C. sedimentary rocks.
7. Radiometric dating methods indicate that Earth is about
A. 4.54 billion
B. 4.54 million
C. 4.54 thousand
Clues to Earth’s Past
years old.
61
Name
Date
Lesson Quiz B
Class
LESSON 3
Absolute-Age Dating
Matching
Directions: On the line before each definition, write the letter of the term that matches it correctly. Not all terms
are used.
1. the time required for half of the amount
of a radioactive isotope to decay
2. process by which an unstable element
changes into another element
3. a numerical age, in years, of a rock or
other object
4. an element with a varying number
of neutrons
A. absolute age
B. carbon-14
C. half-life
D. isotope
E. radioactive decay
F. radiometric dating
G. uranium-238
Short Answer
Directions: Respond to each statement on the lines provided.
5. Describe three objects that could be dated using the radioactive isotope carbon-14.
6. Explain how radiometric dating can be used to date some rocks and not others.
7. Explain how scientists determined Earth’s age and state this value.
62
Clues to Earth’s Past
Name
Date
Lab A
Class
40 minutes
Correlate Rocks Using Index Fossils
Imagine you are a geologist and you have been asked to correlate, or match, the rock
columns below in order to figure out the relative ages of the layers. Remember that
geologists can correlate rock layers in different ways. In this lab, use index fossils to
correlate and find the ages of the layers.
Question
How can index fossils be used to figure out the relative ages of Earth’s rocks?
Procedure
1. Carefully examine the three rock columns on this page.
Each rock layer can be labeled with a letter and a number. For example, the
second layer down in column A is layer A-2.
2. Look at the fossil key on the next page. It shows the time range during which each
organism or group of organisms lived on Earth.
Use the key to correlate the layers using only the fossils—not the types of rock.
You might want to correlate by drawing lines to connect the layers.
Clues to Earth’s Past
63
VName
Date
Class
Lab A continued
Lab Tips
You might want to copy the rock layers in your Science Journal and correlate them by
drawing lines connecting the layers.
Analyze and Conclude
3. Differentiate Which fossils in the key seem to be index fossils? Explain your choices.
64
Clues to Earth’s Past
Name
Date
Class
Lab A continued
4. Match Correlate layer A-2 to one layer in each of the
other two columns. Approximately how old are these
layers? How do you know?
5. Infer What is the age of layer B-4? Hint: It lies
between two index fossils.
6. Infer How old is the fault in column C?
7. Compare and Contrast How is correlating rocks using fossils different from
correlating rocks using types of rock?
8.
The Big Idea How can fossils be used to figure out the relative ages of rocks?
Communicate Your Results
Choose a partner. One of you is a reporter and one is a geologist. Conduct an interview
about what kinds of fossils are best used to date rocks.
Clues to Earth’s Past
65
Name
Date
Class
Lab B
40 minutes
Correlate Rocks Using Index Fossils
Imagine you are a geologist and you have been asked to correlate the rock columns below
in order to determine the relative ages of the layers. Recall that geologists can correlate rock
layers in different ways. In this lab, use index fossils to correlate and date the layers.
Question
How can index fossils be used to determine the relative ages of Earth’s rocks?
Procedure
1. Carefully examine the three rock columns on this page. Each rock layer can be
identified with a letter and a number. For example, the second layer down in
column A is layer A-2.
2. Correlate the layers using only the fossils—not the types of rock. Before you begin,
look at the fossil key on the next page. It shows the time intervals during which each
organism or group of organisms lived on Earth. Refer to the key as you correlate.
Lab Tips
You might want to copy the rock layers in your Science Journal and correlate them by
drawing lines connecting the layers.
66
Clues to Earth’s Past
Name
Date
Class
Lab B continued
Analyze and Conclude
3. Differentiate Which fossils in the key appear to be index fossils? Explain your choices
4. Match Correlate layer A-2 to one layer in each of the other two columns.
Approximately how old are these layers? How do you know?
5. Infer What is the approximate age of layer B-4? Hint: It lies between two index fossils.
6. Infer How old is the fault in column C?
Clues to Earth’s Past
67
Name
Date
Class
Lab B continued
7. Compare and Contrast How does correlating rocks
using fossils differ from correlating rocks using types
of rock?
8.
The Big Idea How can fossils be used to determine
the relative ages of rocks?
Communicate Your Results
Choose a partner. One of you is a reporter and one is a geologist. Conduct an interview
about what kinds of fossils are best used to date rocks.
Extension
Choose one of the three rock formations you correlated. Based on your results, provide
a range of dates for each of the layers within it.
68
Clues to Earth’s Past
Name
Date
Class
Lab C
Correlate Events
Directions: Use the information and data from the Lab Correlate Rocks Using Index Fossils to perform this lab.
You have learned that rock types and index fossils are important tools for scientists to
use when they need to determine the relative ages of rock layers. In this lab, you will
determine a way to identify ten events that have been important in your life. Then you
will correlate your events with those of a partner. Use your understanding of the concepts
of relative age and the Principle of Superposition to form a hypothesis of how you will
correlate your events with those of your partner. How are these procedures similar to the
tasks of a geologist?
Please note that you must complete Lab B before beginning Lab C. Have your teacher
approve your design and safety procedures before beginning your experiment.
Clues to Earth’s Past
69
Name
Date
Class
Chapter Key Concepts Builder
Clues to Earth’s Past
End-of-Chapter Practice
Directions: Work with a small group to create a display you might see in the geology section of a museum. Here
is what you need to do to complete this activity:
As a group, list the important
concepts from this chapter.
The following clues must be
included on your display in
some way:
• fossil formation
• index fossils
• rock layers
• relative-age dating
• absolute-age dating
Things to remember:
• The display should be neat.
• The display should be
organized.
• The display can be any size
your teacher approves.
• Everyone in the group
must participate in some
way.
• Then as a group, divide the duties for creating the wall mural.
Designing the display:
• How will it be constructed?
• What materials will be
needed?
Writing text or captions:
• What will it say?
• How will it say it?
Artwork:
• What artwork will you
include?
• How will it be obtained or
created?
• Present the display to the class.
Your wall mural should accomplish the following:
• convey information accurately
• convey information in an interesting way
• Be prepared to answer questions from your class and teacher.
70
Clues to Earth’s Past
Name
Date
Class
Chapter Test A
Clues to Earth’s Past
Multiple Choice
Directions: On the line before each question, write the letter of the correct answer
1. Which item is NOT a fossil?
A. a million-year-old bacteria
B. a dead tree on a forest floor
C. a mosquito inside a piece of amber
2. Which object would most likely become a fossil?
A. a shark tooth
B. a pine needle
C. a large jellyfish
3. Which item is a trace fossil?
A. a woolly mammoth’s footprint
B. a carbon film of an extinct plant
C. a dinosaur bone preserved in rock
4. What is a relative age?
A. an exact age of a rock or fossil
B. a radiometric age of a rock or fossil
C. the age of a rock or fossil with respect to other rocks or fossils
5. What is a half-life?
A. the numerical age of half of the daughter material
B. the numerical age, in years, of a rock or other object
C. the time required for half the amount of a radioactive substance to decay
6. Which object could be accurately dated using carbon-14?
A. Earth itself
B. a sedimentary rock
C. a mammoth preserved in ice
7. Which isotope would be most useful for dating some of Earth’s oldest rocks?
A. one with a long half-life
B. one with a short half-life
C. one with two different half-lives
Clues to Earth’s Past
71
Name
Date
Class
Chapter Test A continued
Matching
Directions: On the line before each definition, write the letter of the term that matches it correctly. Each term
is used only once
8. states that the oldest rocks are at the bottom
A. catastrophism
9. idea that Earth’s features and its life-forms
B. correlation
change quickly
C. superposition
10. process of matching rocks at different locations
D. uniformitarianism
11. states that processes occurring today are similar
to processes that occurred in the past
Interpreting a Diagram
Directions: Use the diagram to answer each question or respond to each statement.
12. Interpret Which one is older—rock A or rock B?
13. Identify Rock A is an igneous rock. The thin, black bed above it is coal, a sedimentary
rock. What type of unconformity exists at point D?
14. Sequence Feature G is a fault. Did the fault occur before or after rock layer F was
deposited?
15. Compare Which one is older—rock C or rock B? Explain.
72
Clues to Earth’s Past
Name
Date
Class
Chapter Test A continued
Short Answer
Directions: Respond to each statement on the lines provided.
16. Contrast fossil molds and fossil casts.
17. List three characteristics of index fossils.
Concept Application
Directions: Answer the question or respond to each statement on the lines provided.
18. A rock layer at Earth’s surface contains many fish fossils. Describe how the fossils
formed. Also explain how this part of Earth has changed over time.
19. Infer three things that can be learned about ancient organisms by studying similarlooking modern organisms. Consider what you know about trilobites and horseshoe
crabs as you write your answer.
20. Evaluate Suppose you are in a river valley. Which two geologic principles could you
use to determine whether the rock beds on either side of the valley are the same?
Clues to Earth’s Past
73
Name
Date
Class
Chapter Test B
Clues to Earth’s Past
Multiple Choice
Directions: On the line before each question or statement, write the letter of the correct answer.
1. Petrified wood is an example of a
A. trace fossil.
B. microfossil.
C. carbon film fossil.
D. mineral replacement fossil.
2. Which object has the best chance of becoming fossilized?
A. an unfertilized bird egg
B. bark from a redwood tree
C. a leaf buried under sand on a forest floor
D. a microscopic organism with hard spines
Completion
Directions: On each line, write the term from the word bank that correctly completes each sentence. Not all
terms are used.
carbon-14
relative dating
catastrophism
superposition
correlation
trace
index
lateral continuity
uncomformity uniformitarianism
3. A break, or gap, in the rock record is evidence of
4. Fossilized bird footprints are excellent
fossils.
5. Sedimentary rocks are often dated using
6.
.
methods.
might be used to determine the ages of some Egyptian
mummies.
7.
is the idea that conditions and creatures on Earth change
as a result of quick, violent events.
8. Matching rock layers in different parts of the same state is an example
of
9.
.
states that in undisturbed rock layers, the youngest rock layers
are on top.
10. According to
, processes that are occurring today are similar
to processes that occurred in the past.
11. According to
, sediment is deposited in large, continuous
sheets.
74
Clues to Earth’s Past
Name
Date
Class
Chapter Test B continued
Interpreting a Diagram
Directions: Use the diagram to answer each question or respond to each statement or answer each question.
12. Name two geologic principles that can be used to determine the ages of the rocks
in this sequence.
13. Identify Rock A is igneous. The top of rock A has been eroded. The rocks above it are
sedimentary. Does an unconformity exist in this sequence of rocks? If it does, what
type is it and where is it located?
14. Sequence Feature G is a fault. Which rocks in the sequence are younger than the fault?
15. Summarize the geologic history of rocks A, B, C, and E using relative-age dating
methods.
Clues to Earth’s Past
75
Name
Date
Class
Chapter Test B continued
Short Answer
Directions: Respond to each statement on the lines provided.
16. Compare and contrast preserved remains and mineral replacement fossils.
17. Explain which object would be a better index fossil—a trilobite or a horseshoe crab.
Concept Application
Directions: Answer the question or respond to each statement on the lines provided.
18. Hypothesize Mammoth remains have been discovered frozen in ice. Explain how these
fossils formed and what they indicate about Earth’s past.
19. Infer Coal beds are present in Antarctica. What does this tell you about this continent’s
past?
20. Evaluate Why do geologists often use relative- and absolute-age dating methods to
determine the ages of rocks in a sequence?
76
Clues to Earth’s Past
Name
Date
Class
Chapter Test C
Clues to Earth’s Past
Multiple Choice
Directions: On the line before each question or statement, write the letter of the correct answer.
1. A
A.
B.
C.
D.
is a fossil of preserved remains.
mineralized fish bone in mud
sabertooth tiger bone trapped in tar
petrified tree trunk buried in volcanic ash
cast of dinosaur footprints along a lake bed
2. Which object has the best chance of becoming fossilized?
A. an unfertilized bird egg
B. bark from a redwood tree
C. a leaf buried under sand on a forest floor
D. a microscopic organism with hard spines
3. Which object is NOT a trace fossil?
A. a trilobite mold
B. fossilized wastes
C. dinosaur footprints
D. an ancient worm burrow
Completion
Directions: On each line, write the term that correctly completes each sentence.
4. After one
, half of the amount of any radioactive isotope
remains.
5.
might be used to determine the ages of some Egyptian mummies.
6. The idea that extinctions occur as the result of a single event is known
as
.
7. Because the sedimentary rocks in the Grand Canyon are horizontal, the geologic
principle of
can be used to determine the relative ages
of these rocks.
8. Fossils are often used in
when rock layers are
geographically separated.
9. When scientists use processes occurring today to interpret events of the past, they are
using the principle of
10. The principle of
.
states that sedimentary rocks form
continuous layers until they thin out or hit a barrier.
Clues to Earth’s Past
77
Name
Date
Class
Chapter Test C continued
Interpreting a Diagram
Directions: Use the diagram to answer each question or respond to each statement.
11. Evaluate Which rock in the diagram is the
oldest? Explain your choice.
12. Identify If rock A is an igneous rock, the top of
rock A has been eroded, and the overlying beds
are sedimentary, then what type of contact exists
at point D? Define the term.
13. Identify feature G and state when it occurred.
14. Explain Which rocks can be dated using relative-age dating methods, and which ones
can be dated using absolute-age dating methods?
15. Identify feature C and infer its relative age.
78
Clues to Earth’s Past
Name
Date
Class
Chapter Test C continued
Short Answer
Directions: Respond to each statement on the lines provided.
16. Contrast five different modes of fossil formation.
17. Explain the significance of index fossils and give an example of one.
Concept Application
Directions: Answer the question or respond to each statement on the lines provided.
18. Explain how three different types of fossils might form from organisms in a forest setting.
19. Synthesize A geologist discovers seashells preserved in sedimentary rocks on a
mountaintop. What can she conclude from her discovery?
20. Summarize how relative- and absolute-age dating methods could be used to
determine the age of a sedimentary rock containing ice age fossils.
Clues to Earth’s Past
79