Name _______________________________Class __________________ Date __________________
Skills Worksheet
Directed Reading A
PALEONTOLOGY—THE STUDY OF PAST LIFE
Match the correct definition with the correct term. Write the letter in the space provided.
_____ 1. the study of past life using fossils
_____ 2. scientists who study past life using fossils
_____ 3. remains of organisms preserved by geologic processes
a. paleontology
b. fossils
c. paleontologists
d. geology
_____ 4. the study of the history of the Earth
Write the letter of the correct answer in the space provided.
_____ 1. Determining the age of objects or events in relation to other objects or events is called
a. relative sequencing.
b. relative dating.
c. relative history.
d. relative geology.
THE PRINCIPLE OF SUPERPOSITION
_____ 2. As long as a sequence of rock layers is undisturbed, scientists know that
a. older rocks lie above younger rocks.
b. younger rocks lie under older rocks.
c. younger rocks lie above older rocks.
d. older rocks have eroded away.
_____ 3. The principle that states that younger rocks lie above other rocks in undisturbed sequences is
called
a. relative dating.
b. superposition.
c. uniformitarianism.
d. catastrophism.
4. How do disruptions of rock sequences pose a challenge to geologists?
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THE GEOLOGIC COLUMN
5. What is the geologic column?
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Name _______________________________Class __________________ Date __________________
6. How do geologists use the geologic column?
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Disturbed Rock layers
7. Explain how a crosscutting feature is always younger than the rock layers it cuts across.
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Match the correct description with the correct term. Write the letter in the space provided.
_____ 8. a break in the Earth’s crust along which blocks of crust slide relative
to one another
a. superposition
b. folding
c. fault
d. tilting
e. intrusion
_____ 9. younger sediment deposited on top of older layers
_____ 10. molten rock that has squeezed into existing rock and hardened
_____ 11. rock layers bent and buckled by the Earth’s internal forces
_____ 12. rock layers slanted by the Earth’s internal forces but without folding
GAPS IN THE RECORD—UNCONFORMITIES
13. When a layer or several layers of rock are missing from a rock-layer sequence, this is called a(n)
______________________
14. Name two possible explanations for a missing layer in a rock-layer sequence.
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15. When sediment stops at some point and restarts, an unconformity is created by __________________.
16. An unconformity is created when an area is uplifted and exposed to ______________________ by
wind and water.
Match the correct description with the correct term. Write the letter in the space provided.
_____ 17. found between horizontal layers of sedimentary rock and rock
layers that have been tilted or folded
_____ 18. where sedimentary rock layers lie on top of an eroded surface of
older intrusive igneous or metamorphic rock
_____ 19. most common type of unconformity
a. disconformity
b. nonconformity
c. angular unconformity
Name _______________________________Class __________________ Date __________________
ROCK-LAYER PUZZLES
20. How do geologists figure out rock-layer puzzles?
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Section: Relative Dating: Which Came First?
Write the letter of the correct answer in the space provided.
_____ 1. Determining the age of objects or events in relation to other objects or events is called
a. relative sequencing.
b. relative dating.
c. relative history.
d. relative geology.
_____ 2. As long as a sequence of rock layers is undisturbed, scientists know that
a. older rocks lie above younger rocks.
b. younger rocks lie under older rocks.
c. younger rocks lie above older rocks.
d. older rocks have eroded away.
_____ 3. The principle that states that younger rocks lie above other rocks in undisturbed sequences is
called
a. relative dating.
b. superposition.
c. uniformitarianism.
d. catastrophism.
4. How do disruptions of rock sequences pose a challenge to geologists?
_______________________________________________________________
_______________________________________________________________
Section: Absolute Dating: A Measure of Time
1. What is the purpose of absolute dating?
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2. Atoms of the same element that have the same number of protons but a different number of neutrons are
called ______________________.
3. When an isotope is ______________________, it does not undergo radioactive decay.
4. When an isotope is ______________________, it is called radioactive.
5. During ______________________, an unstable isotope breaks down into a stable isotope.
Name _______________________________Class __________________ Date __________________
6.How do scientists use isotopes to determine the age of an object?
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7. An unstable isotope is called the ______________________ isotope.
8. The stable isotope is called the ______________________ isotope.
9. The more daughter material there is in a rock sample, the ______________________the rock is.
RADIOMETRIC DATING
10. The time it takes for one-half of a radioactive sample to decay is called a(n) ____________________.
11. Determining the age of a sample, based on the ratio of parent material to daughter material, is called
______________________
12. After every half-life, what has happened to the parent material in an object?
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TYPES OF RADIOMETRIC DATING
Match the description of the type of radiometric dating with the correct term.
_____ 13. used mainly for dating objects that are younger than 50,000 years
_____ 14. used mainly for dating rocks older than 100,000 years
_____ 15. used to date rocks older than 10 million years; half-life of isotope is
4.5 billion years
a. potassium-argon
b. uranium-lead
c. rubidium-strontium
d. carbon-14
_____ 16. used to date rocks older than 10 million years; half-life of isotope is
49 million years
Section: Looking at Fossils
FOSSILIZED ORGANISMS
_____ 1. What is the name for the trace or remains of an organism that lived long ago, most commonly
preserved in sedimentary rock?
a. sediment
b. fossil
c. cast
d. mold
_____ 2. Most fossils are preserved in
a. asphalt.
b. ice.
c. sedimentary rock.
d. igneous rock.
Name _______________________________Class __________________ Date __________________
_____ 3. Which of the following organisms is commonly found preserved in rock?
a. clam
c. insect
b. jellyfish
d. worm
_____ 4. Some of our best insect fossils are preserved in
a. amber.
c. ice.
b. rock.
d. asphalt.
_____ 5. Which of the following is an example of an organism whose tissue has been replaced by
minerals?
a. a shell preserved in rock
b. petrified wood
c. a frozen mammoth
d. an insect trapped in amber
_____ 6. The La Brea asphalt deposits have been trapping and preserving organisms
a. for less than 10,000 years.
b. for less than 500 years.
c. for at least 38,000 years.
d. for 1 million years.
_____ 7. In 1999, scientists removed remains of a wooly mammoth from what material?
a. asphalt
b. ice
c. wood
d. amber
Match the correct definition with the correct term. Write the letter in the space provided.
_____ 8. any naturally preserved evidence of an animal’s activity
_____ 9. a cavity in rock where a plant or animal was buried
_____ 10. an object created when sediment fills a mold and becomes a rock
a. mold
b. trace fossil
c. cast
11. What can animal tracks tell about the animal that left them?
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12. What can a coprolite tell about the animal that left it?
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_____ 13. Which of the following statements about the fossil record is true?
a. Most organisms never became fossils.
b. Scientists know more about organisms that had soft body parts than about organisms that had
hard body parts.
c. Scientists have learned nothing about the history of life on earth from fossils.
d. The fossil record is complete.
Name _______________________________Class __________________ Date __________________
_____ 14. The fossil record does NOT reveal information about which of the following?
a. past climates
b. ancient seas
c. the solar system
d. environmental change
USING FOSSILS TO DATE ROCKS
15. How is an index fossil useful to geologists in establishing the age of the rock layer in which they find
it?
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16. Imagine that you found a Tropites fossil. How old is the rock surrounding it? _____________________
17. Imagine that you found a Phacops fossil. How old is the rock surrounding it? _____________________
Section: Time Marches On
8. What do the boundaries between geologic time intervals represent?
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9. Number the following divisions of geologic time from largest to smallest.
_____ epoch
_______eon
_______era
_______period
10. What is extinction?
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11. What kinds of catastrophic events can cause extinction?
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12. What probably caused the extinction of dinosaurs?
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