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ESS 101 B Lab 5 Quiz 2026-2027 BANK QUESTIONS WITH
DETAILED VERIFIED ANSWERS EXAM QUESTIONS WILL
COME FROM HERE (100% CORRECT ANSWERS A+ GRADED
1. In a sequence of undisturbed sedimentary rocks, where is the oldest
layer located?
A. At the top
B. In the middle
C. At the bottom
D. Interspersed randomly
Answer: C
Explanation: This is a direct application of the Principle of
Superposition. In any undisturbed sequence of strata, the layers at the
bottom were deposited first and are therefore older than the layers
above them, which were deposited progressively later.
2. A fault cutting through a layer of sandstone is discovered. Which
principle dictates that the fault is younger than the sandstone?
A. Principle of Original Horizontality
B. Principle of Superposition
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C. Principle of Cross-Cutting Relationships
D. Principle of Faunal Succession
Answer: C
Explanation: The Principle of Cross-Cutting Relationships states that a
geologic feature which cuts across another is the younger of the two
features. Since the fault fractures and displaces the sandstone, the
sandstone must have been present first for the fault to cut through it.
3. Which type of unconformity represents an erosional surface between
parallel sedimentary strata?
A. Angular unconformity
B. Disconformity
C. Nonconformity
D. Paraconformity
Answer: B
Explanation: A disconformity is a type of unconformity where the beds
above and below the erosional surface are parallel. The gap in the
geologic record is often marked by an irregular surface of erosion, and
can be difficult to identify without fossil evidence.
4. A radioactive isotope has a half-life of 10,000 years. If a sample starts
with 1,000 atoms of the parent isotope, how many parent atoms
remain after 20,000 years?
A. 500
B. 250
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C. 125
D. 0
Answer: B
Explanation: Each half-life reduces the amount of parent isotope by
half. After 10,000 years (one half-life), 500 atoms remain. After another
10,000 years (20,000 years total, or two half-lives), the 500 atoms are
halved again, leaving 250 parent atoms.
5. A dike of basalt is found intruding a sequence of limestone and shale
layers. The basalt is radiometrically dated to 201 million years old. A
dinosaur fossil found in the shale is therefore:
A. Exactly 201 million years old
B. Older than 201 million years
C. Younger than 201 million years
D. The same age as the limestone
Answer: B
Explanation: The Principle of Cross-Cutting Relationships tells us the
basalt dike is younger than the shale it intrudes. If the dike is 201 Ma,
the shale, and the fossil within it, must have existed before the
intrusion. Therefore, the fossil is older than 201 million years.
6. What does the Principle of Original Horizontality state about
sediment deposition?
A. Sediments are deposited at the bottom of a basin first.
B. Sediments are deposited in nearly horizontal layers.
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C. Sediments are deposited in a vertical orientation.
D. Sediments are deposited based on particle size.
Answer: B
Explanation: The Principle of Original Horizontality posits that layers of
sediment are originally deposited horizontally under the action of
gravity. If we observe folded or tilted strata, we can infer that
deformation occurred after the deposition of the layers.
7. Which fossil type is most useful for correlating strata over wide
geographic areas and defining short intervals of geologic time?
A. A large, slow-evolving dinosaur bone
B. A small, rapidly evolving marine invertebrate
C. A trace fossil of a worm burrow
D. A petrified log from an ancient forest
Answer: B
Explanation: An ideal index fossil, or guide fossil, is geographically
widespread, abundant, and existed for a very short period of geologic
time. Rapidly evolving marine invertebrates like ammonites and
graptolites are classic examples, allowing for precise biostratigraphic
correlation.
8. An igneous rock's numerical age is determined using the ratio of
parent to daughter isotopes. This method is known as:
A. Relative dating
B. Stratigraphic correlation
ESS 101 B Lab 5 Quiz 2026-2027 BANK QUESTIONS WITH
DETAILED VERIFIED ANSWERS EXAM QUESTIONS WILL
COME FROM HERE (100% CORRECT ANSWERS A+ GRADED
1. In a sequence of undisturbed sedimentary rocks, where is the oldest
layer located?
A. At the top
B. In the middle
C. At the bottom
D. Interspersed randomly
Answer: C
Explanation: This is a direct application of the Principle of
Superposition. In any undisturbed sequence of strata, the layers at the
bottom were deposited first and are therefore older than the layers
above them, which were deposited progressively later.
2. A fault cutting through a layer of sandstone is discovered. Which
principle dictates that the fault is younger than the sandstone?
A. Principle of Original Horizontality
B. Principle of Superposition
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C. Principle of Cross-Cutting Relationships
D. Principle of Faunal Succession
Answer: C
Explanation: The Principle of Cross-Cutting Relationships states that a
geologic feature which cuts across another is the younger of the two
features. Since the fault fractures and displaces the sandstone, the
sandstone must have been present first for the fault to cut through it.
3. Which type of unconformity represents an erosional surface between
parallel sedimentary strata?
A. Angular unconformity
B. Disconformity
C. Nonconformity
D. Paraconformity
Answer: B
Explanation: A disconformity is a type of unconformity where the beds
above and below the erosional surface are parallel. The gap in the
geologic record is often marked by an irregular surface of erosion, and
can be difficult to identify without fossil evidence.
4. A radioactive isotope has a half-life of 10,000 years. If a sample starts
with 1,000 atoms of the parent isotope, how many parent atoms
remain after 20,000 years?
A. 500
B. 250
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C. 125
D. 0
Answer: B
Explanation: Each half-life reduces the amount of parent isotope by
half. After 10,000 years (one half-life), 500 atoms remain. After another
10,000 years (20,000 years total, or two half-lives), the 500 atoms are
halved again, leaving 250 parent atoms.
5. A dike of basalt is found intruding a sequence of limestone and shale
layers. The basalt is radiometrically dated to 201 million years old. A
dinosaur fossil found in the shale is therefore:
A. Exactly 201 million years old
B. Older than 201 million years
C. Younger than 201 million years
D. The same age as the limestone
Answer: B
Explanation: The Principle of Cross-Cutting Relationships tells us the
basalt dike is younger than the shale it intrudes. If the dike is 201 Ma,
the shale, and the fossil within it, must have existed before the
intrusion. Therefore, the fossil is older than 201 million years.
6. What does the Principle of Original Horizontality state about
sediment deposition?
A. Sediments are deposited at the bottom of a basin first.
B. Sediments are deposited in nearly horizontal layers.
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C. Sediments are deposited in a vertical orientation.
D. Sediments are deposited based on particle size.
Answer: B
Explanation: The Principle of Original Horizontality posits that layers of
sediment are originally deposited horizontally under the action of
gravity. If we observe folded or tilted strata, we can infer that
deformation occurred after the deposition of the layers.
7. Which fossil type is most useful for correlating strata over wide
geographic areas and defining short intervals of geologic time?
A. A large, slow-evolving dinosaur bone
B. A small, rapidly evolving marine invertebrate
C. A trace fossil of a worm burrow
D. A petrified log from an ancient forest
Answer: B
Explanation: An ideal index fossil, or guide fossil, is geographically
widespread, abundant, and existed for a very short period of geologic
time. Rapidly evolving marine invertebrates like ammonites and
graptolites are classic examples, allowing for precise biostratigraphic
correlation.
8. An igneous rock's numerical age is determined using the ratio of
parent to daughter isotopes. This method is known as:
A. Relative dating
B. Stratigraphic correlation
