Name:
1.
------------------------------------Chapter 8 Section 2 Pages
Period:
191-196
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Differentiate between relative and absolute age.
2. Describe varves, and describe how and where they form.
3. Explain how radiometric dating is used to estimate absolute age.
4. Define half-life, and explain how it helps determine an object's absolute age.
5. List three methods of radiometric dating, and explain the age range for which they are
most effective.
6. Demonstrating reasoned Judgement: Suppose you have a shark's tooth that you suspect
is about 15,000 years old. Would you use 238U or 14C to date the tooth? Explain your
answer.
7. Use the following terms to create a concept map: absolute age, varve, radiometric dating,
parent isotope, daughter isotope, and carbon dating.
Nrume
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e. 111 - /tb
Section: Determining Absolute Age
MATCHING
In the space provided, write the letter of the definition that best matches the term
or phrase.
1. half-life
2. radiometric dating
3. radiocarbon dating
4. varve
5. alpha decay
a. two protons and two neutrons emitted by
the nucleus
b. determining age through comparison of
isotopes
c. the time it takes for half of a sample of
radioactive isotope to decay
d. using organic remains to date objects
e. banded layers of sediment deposited
annually
MULTIPLE CHOICE
In the space provided, write the letter of the answer choice that best completes
each statement or best answers each question.
6. The numeric age of an
9. How many years of
object is called
a. relational age.
b. comparative age.
c. relative age.
d. absolute age.
deposition are represented
by a single varve?
a. three
b. two
c. one
d. The number of years
cannot be measured.
7. How much sedimentary
rock is deposited over
1,000 years?
a. about 3 em
b. about 3 m
c. about 30 m
d. about 30 cm
_____
8. Carbon-14 is an isotope
a. formed by radioactive
decay.
b. used to date objects less
than 70,000 years old.
c. used to date objects over
6,000 years old.
d. that cannot be used to
date objects.
10.
Rates of erosion are not
used to date geographical
features over a million years
old because
a. rates of erosion are
constant over a million
years.
b. erosion ceases over a
million years.
c. rates of erosion may
greatly vary over a
million years.
d. rates of erosion are
constant only for about
20,000 years.
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33
The Rock Record
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11.
1. Where can we find evidence of changes
use to describe
in conditions
on Earth's surface?
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Date
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in the oldest layers of rock have
for millions of years.
When the first geologic columns were developed,
use to estimate the ages of rock layers?
what factors did scientists
and length of changes in
the sequence
12. What method
accurately?
3. What is the purpose
Class
Many of the fossils that have been discovered
been
Section: Geologic Time
2. What do scientists
Earth's crust?
10.
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Reading continued
has enabled scientists
to determine
the ages of rock layers more
of the geologic time scale?
13.
Suppose a scientist wants to determine the age of a rock layer with a geologic
column. With what does the scientist compare the rock layer?
THE GEOLOGIC COLUMN
4. What two things did 19'" century scientists
of sedimentary rock allover the world?
do to determine
the relative ages
14. Suppose a layer of rock matches a layer on the geologic column. What does
thls tell a scientist?
5. Why did scientists
combine their observations
of rocks allover the world?
DIVISIONS
OF GEOLOGIC TIME
15. What three indicators
smaller units?
6. The ordered arrangement
do geologists use to divide the geologic time scale into
of rock layers is called
a(n)
_
16. How are rocks grouped within each unit of geologic time similar?
7. In a geologic column, the oldest rocks are located at the
__________
a. What
of the column.
two things distinguish
17. A unit of geologic time is usually characterized
by
a rock layer in a geologic column?
__________
18.
9. How do the fossils in the upper layers of a geologic column differ from those
in the lower, older layers?
of a dominant life-form.
What does the abbreviation
19. When did Precambrian
Ma stand for?
time begin?
20. What species were common during the Cambrian
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resert ..cd.
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Period?
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A View of Earth's Past
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View of
Earth's
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21. What happened to the atmosphere
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during the Ordovician Period?
_ Class
36. Why is it difficult to divide Precambrian
22. When did the Silurian Period begin?
_
time into smaller time units?
37. An eon is divided into smaller units of geologic time
called
23. During which period did the age of fishes begin?
Period?
eon was the
Era lasted about
'
.
40. What kinds of fossils are found in rocks from the Paleozoic
Is the Carboniferous
25. In North America, into what two periods
_
38. The first era of the Phanerozoic
39. The Paleozoic
24. In what era was the Carboniferous
Date
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Era?
Period divided?
41. The era after the Paleozoic Era was the
42. What kinds of fossils are found in rocks from the Mesozoic
26. What was the dominant life-form of the Jurassic
Period?
43. The present
27. What marked the end of the Mesozoic Era?
geologic era is called the
44. When did the present
28. In which epoch did the age of mammals
_
Era?
.
geologic era begin?
begin?
45. What kinds of fossils are common in Cenozoic rocks?
29. When did the Eocene Epoch begin'?
46.An era is divided into shorter time units called
30. In what epoch did large carnivores
appear?
31. In what period was the Pleistocene
Epoch?
32. In what. epoch did complex human societies
47.
'
How do geologic periods get their names?
48. A period may be divided into smaller units called
49. Why can scientists
develop?
33. The largest unit of geologic time is called a(n)
not always divide a period into epochs?
_
34. Name the four eons into which geologic time is divided,
50. An epoch may be divided into shorter units called
_
51. How is an age defined?
35. The Hadean eon, the Archean eon, and the Proterozoic
interval called
eon make up an
__
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Holt Earth Science
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winston.
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A View of Earth's Past