Name
Class
Date
How do fossils help us date rocks?
Lesson Review
Use the diagrams below to answer the questions that follow.
1. Write the order in which the rock layers in Figure 1 were laid down. _____________________________
2. Which rock layer in Figure 1 is oldest? Use the law of superposition to explain your answer.
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3. a. What organism is shown in Figure 2? ___________________
b. Figure 3? ______________________
4. How can the organisms in Figures 2 and 3 be used to determine the relative ages of rock layers?
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Skill Challenge
Skills: analyzing, inferring
Use the diagrams below to answer the questions that follow.
A
Graptolite fossils
B
Rock Layers
G
Rock Layers
C
D
Trilobite fossils
E
Figure 1
Human skull
F
Rock layers in China
Figure 2
H
Graptolite fossils
I
Trilobite fossils
J
Trilobite fossils
Rock layers in Africa
1. Which rock layers in Figure 1 have the same relative ages as those in Figure 2? ____________________
2. Which country has the older rock bed? Explain. ________________________________________________
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3. What inference can you make about the two layers of rock that contain trilobite fossils in Figure 2?
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Concepts and Challenges in Earth Science, Teacher’s Resources CD-ROM
(c) by Pearson Education, Inc./Globe Fearon/Pearson Learning Group. All rights reserved.
The Rock Record
Answer Key
How do fossils help us date rocks?
Lesson Review
1. F, E, D, C, B, A 2. Layer F; The law of
superposition states that each undisturbed rock
layer is older than the one above it. Since Layer F is
on the bottom, it is older than all of the other layers.
3. a. trilobite b. graptolites 4. Trilobites and
graptolites are index fossils. If these fossils are found
in a rock layer, the rock layer is about the same age
as the fossil.
Skill Challenge
1. Layers A and H are about the same age; Layers D,
I, and J are about the same age. 2. China; The oldest
layer in China is older than the trilobite fossils. The
oldest layer in Africa is the same age as the trilobite
fossils. 3. Both layers of rock were laid down at the
time that trilobites existed. Thus, both layers are
between 590 and 250 million years old.
Concepts and Challenges in Earth Science, Teacher’s Resources CD-ROM
(c) by Pearson Education, Inc./Globe Fearon/Pearson Learning Group. All rights reserved.
The Rock Record