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Illinois (IL) ASBOG Fundamentals of Geology Exam | Latest
Verified Questions and Detailed Answers
OVERVIEW DESCRIPTION:
This comprehensive set of multiple-choice questions is designed for the Illinois ASBOG
Fundamentals of Geology Exam, the first of two examinations required for professional
geologist licensure. The exam assesses foundational knowledge across the geosciences,
including general and field geology, mineralogy, petrology, geochemistry, sedimentology,
stratigraphy, paleontology, geomorphology, structural geology and tectonics,
hydrogeology, engineering geology, and economic geology and environmental geophysics.
It is developed by the National Association of State Boards of Geology (ASBOG) and used by
state licensing boards, including Illinois, to evaluate core competencies needed for entry-
level geologic practice.
QUESTION 1
Which mineral has a Mohs hardness of 7?
A. Orthoclase
B. Quartz
C. Topaz
D. Apatite
CORRECT ANSWER: B
EXPERT RATIONALE: Quartz has a Mohs hardness of 7, making it harder than glass and
useful in field testing. Orthoclase has hardness 6, apatite 5, and topaz 8.
QUESTION 2
Which mineral group is most abundant in Earth's continental crust?
A. Carbonates
B. Oxides
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C. Feldspars
D. Sulfides
CORRECT ANSWER: C
EXPERT RATIONALE: Feldspars are the most abundant mineral group in continental
crust, comprising about 60% by volume. They occur in igneous, metamorphic, and
sedimentary rocks.
QUESTION 3
An igneous rock with phaneritic texture composed chiefly of plagioclase feldspar and
pyroxene is called
A. Rhyolite
B. Gabbro
C. Granite
D. Diorite
CORRECT ANSWER: B
EXPERT RATIONALE: Gabbro is the phaneritic intrusive equivalent of basalt, dominated
by calcium-rich plagioclase and pyroxene. Granite contains quartz and alkali feldspar,
while diorite has more amphibole and less pyroxene.
QUESTION 4
A bed strikes N45°E and dips 30°SE. What is the dip direction?
A. N45°E
B. S45°E
C. N45°W
D. S45°W
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CORRECT ANSWER: B
EXPERT RATIONALE: Dip direction is perpendicular to strike and in the down-slope
direction. For a strike of N45°E dipping SE, the dip direction is S45°E.
QUESTION 5
On a topographic map, contour lines crossing a stream form a V that points
A. Downstream
B. Upstream
C. East
D. Downhill
CORRECT ANSWER: B
EXPERT RATIONALE: Contour lines bend upstream when crossing valleys because the
stream occupies the lowest local elevation. The V points in the direction of higher
elevation, which is upstream.
QUESTION 6
Which instrument is standard for measuring strike and dip in the field?
A. Barometer
B. Brunton compass
C. Gravimeter
D. Seismometer
CORRECT ANSWER: B
EXPERT RATIONALE: A Brunton compass combines a compass, clinometer, and level for
measuring strike, dip, and trend. It is the standard field instrument for structural
measurements.
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QUESTION 7
In an undeformed sedimentary sequence, the principle of superposition states that
A. The oldest layer is at the top
B. The oldest layer is at the bottom
C. All layers are the same age
D. Ages cannot be determined
CORRECT ANSWER: B
EXPERT RATIONALE: In an undisturbed sequence, each sedimentary layer is younger
than the one beneath it, so the oldest is at the bottom. This is a fundamental
stratigraphic principle.
QUESTION 8
An erosional surface separating parallel sedimentary strata is a(n)
A. Nonconformity
B. Angular unconformity
C. Disconformity
D. Paraconformity
CORRECT ANSWER: C
EXPERT RATIONALE: A disconformity is an unconformity between parallel sedimentary
beds, often marked by erosion or a paleosol. Angular unconformities separate tilted
from horizontal strata, and nonconformities separate sedimentary rocks from crystalline
rocks.
QUESTION 9
Which field test best distinguishes calcite from dolomite?
A. Streak test
Illinois (IL) ASBOG Fundamentals of Geology Exam | Latest
Verified Questions and Detailed Answers
OVERVIEW DESCRIPTION:
This comprehensive set of multiple-choice questions is designed for the Illinois ASBOG
Fundamentals of Geology Exam, the first of two examinations required for professional
geologist licensure. The exam assesses foundational knowledge across the geosciences,
including general and field geology, mineralogy, petrology, geochemistry, sedimentology,
stratigraphy, paleontology, geomorphology, structural geology and tectonics,
hydrogeology, engineering geology, and economic geology and environmental geophysics.
It is developed by the National Association of State Boards of Geology (ASBOG) and used by
state licensing boards, including Illinois, to evaluate core competencies needed for entry-
level geologic practice.
QUESTION 1
Which mineral has a Mohs hardness of 7?
A. Orthoclase
B. Quartz
C. Topaz
D. Apatite
CORRECT ANSWER: B
EXPERT RATIONALE: Quartz has a Mohs hardness of 7, making it harder than glass and
useful in field testing. Orthoclase has hardness 6, apatite 5, and topaz 8.
QUESTION 2
Which mineral group is most abundant in Earth's continental crust?
A. Carbonates
B. Oxides
,2|Page
C. Feldspars
D. Sulfides
CORRECT ANSWER: C
EXPERT RATIONALE: Feldspars are the most abundant mineral group in continental
crust, comprising about 60% by volume. They occur in igneous, metamorphic, and
sedimentary rocks.
QUESTION 3
An igneous rock with phaneritic texture composed chiefly of plagioclase feldspar and
pyroxene is called
A. Rhyolite
B. Gabbro
C. Granite
D. Diorite
CORRECT ANSWER: B
EXPERT RATIONALE: Gabbro is the phaneritic intrusive equivalent of basalt, dominated
by calcium-rich plagioclase and pyroxene. Granite contains quartz and alkali feldspar,
while diorite has more amphibole and less pyroxene.
QUESTION 4
A bed strikes N45°E and dips 30°SE. What is the dip direction?
A. N45°E
B. S45°E
C. N45°W
D. S45°W
,3|Page
CORRECT ANSWER: B
EXPERT RATIONALE: Dip direction is perpendicular to strike and in the down-slope
direction. For a strike of N45°E dipping SE, the dip direction is S45°E.
QUESTION 5
On a topographic map, contour lines crossing a stream form a V that points
A. Downstream
B. Upstream
C. East
D. Downhill
CORRECT ANSWER: B
EXPERT RATIONALE: Contour lines bend upstream when crossing valleys because the
stream occupies the lowest local elevation. The V points in the direction of higher
elevation, which is upstream.
QUESTION 6
Which instrument is standard for measuring strike and dip in the field?
A. Barometer
B. Brunton compass
C. Gravimeter
D. Seismometer
CORRECT ANSWER: B
EXPERT RATIONALE: A Brunton compass combines a compass, clinometer, and level for
measuring strike, dip, and trend. It is the standard field instrument for structural
measurements.
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QUESTION 7
In an undeformed sedimentary sequence, the principle of superposition states that
A. The oldest layer is at the top
B. The oldest layer is at the bottom
C. All layers are the same age
D. Ages cannot be determined
CORRECT ANSWER: B
EXPERT RATIONALE: In an undisturbed sequence, each sedimentary layer is younger
than the one beneath it, so the oldest is at the bottom. This is a fundamental
stratigraphic principle.
QUESTION 8
An erosional surface separating parallel sedimentary strata is a(n)
A. Nonconformity
B. Angular unconformity
C. Disconformity
D. Paraconformity
CORRECT ANSWER: C
EXPERT RATIONALE: A disconformity is an unconformity between parallel sedimentary
beds, often marked by erosion or a paleosol. Angular unconformities separate tilted
from horizontal strata, and nonconformities separate sedimentary rocks from crystalline
rocks.
QUESTION 9
Which field test best distinguishes calcite from dolomite?
A. Streak test
