Name ______________________________ Class ___________________ Date __________________
Directed Reading 6.5 pages 172 - 177
Section: Time Marches On
GEOLOGIC TIME
______ 1. How much geologic time do the layers of rock exposed at Grand Canyon
National Park represent?
a. 10 million years
b. 6 million years
c. 2 billion years
d. 6 billion years
THE GEOLOGIC TIME SCALE
2. Why have geologists created the geologic time scale?
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Match the correct description with the correct term. Write the letter in the space
provided.
a. Hadean
______ 3. the eon during which the earliest known rocks formed
on Earth
b. Archean
______ 4. the eon in which we live
c. Proterozoic
d. Phanerozoic
______ 5. the eon from which scientists have found rocks and
meteorites only from the moon
______ 6. the eon in which the first organisms with welldeveloped cells appeared
7. What do the boundaries between geologic time intervals represent?
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8.Number the following divisions of geologic time from largest to smallest.
______ Epoch
_____era
______ Eon
_____period
9.What is extinction?
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Original content Copyright © by Holt, Rinehart and Winston. Additions and changes to the original content are the responsibility of the instructor.
Holt Science and Technology
11
The Rock and Fossil Record
Name ______________________________ Class ___________________ Date __________________
10. What kinds of catastrophic events can cause extinction?
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11. Describe the beginning of the Paleozoic era.
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12. How did the Paleozoic era end?
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13. Why is the Mesozoic era called the Age of Reptiles?
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14. Why is the Cenozoic era called the Age of Mammals?
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15. What probably caused the extinction of dinosaurs?
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16. What unique traits probably helped mammals survive?
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Original content Copyright © by Holt, Rinehart and Winston. Additions and changes to the original content are the responsibility of the instructor.
Holt Science and Technology
12
The Rock and Fossil Record