G202 PHYSICAL GEOLOGY FINAL
EXAM COMPREHENSIVE STUDY GUIDE
QUESTIONS AND ANSWERS 100%
VERIFIED. JUST RELEASED
1. Which tectonic driving force is currently considered the most significant contributor to
plate motion?
A. Mantle convection cells
B. Ridge push
C. Basal drag
D. Slab pull
Answer: D
Conceptual Explanation: While mantle convection provides the heat engine, slab pull—
the gravitational sinking of cold, dense subducting lithosphere—is the primary driver of
plate motion.
2. In the silicate mineral group, which structure is characterized by a 2:5 silicon-to-oxygen
ratio?
A. Sheet silicates (phyllosilicates)
B. Double chain silicates
,C. Single chain silicates
D. Framework silicates
Answer: A
Conceptual Explanation: Sheet silicates like mica share three oxygen atoms per
tetrahedron, resulting in a Si2O5 ratio.
3. Which of the following is the most likely cause of ‘flux melting’ in subduction zones?
A. A decrease in pressure as mantle rock rises toward the surface.
B. The introduction of volatiles, such as water, into the hot mantle wedge.
C. The increase in temperature due to friction between the two plates.
D. Radioactive decay within the subducting oceanic crust.
Answer: B
Conceptual Explanation: Volatiles (mostly water) released from the subducting slab
lower the melting temperature of the overlying mantle peridotite, causing flux melting.
4. According to Bowen’s Reaction Series, which mineral is the first to crystallize from a cooling
mafic magma?
A. Quartz
B. Biotite
C. Muscovite
, D. Olivine
Answer: D
Conceptual Explanation: Olivine is the highest-temperature mineral in the discontinuous
series and crystallizes first from a basaltic/mafic melt.
5. A metamorphic facies characterized by high pressure and low temperature, typically found
in subduction zones, is known as:
A. Greenschist facies
B. Granulite facies
C. Blueschist facies
D. Eclogite facies
Answer: C
Conceptual Explanation: Blueschist facies requires high pressure and relatively low
temperatures, conditions unique to the rapid subduction of oceanic lithosphere.
6. Which type of unconformity involves sedimentary layers deposited over older, eroded
igneous or metamorphic rocks?
A. Disconformity
B. Angular unconformity
C. Paraconformity
D. Nonconformity
EXAM COMPREHENSIVE STUDY GUIDE
QUESTIONS AND ANSWERS 100%
VERIFIED. JUST RELEASED
1. Which tectonic driving force is currently considered the most significant contributor to
plate motion?
A. Mantle convection cells
B. Ridge push
C. Basal drag
D. Slab pull
Answer: D
Conceptual Explanation: While mantle convection provides the heat engine, slab pull—
the gravitational sinking of cold, dense subducting lithosphere—is the primary driver of
plate motion.
2. In the silicate mineral group, which structure is characterized by a 2:5 silicon-to-oxygen
ratio?
A. Sheet silicates (phyllosilicates)
B. Double chain silicates
,C. Single chain silicates
D. Framework silicates
Answer: A
Conceptual Explanation: Sheet silicates like mica share three oxygen atoms per
tetrahedron, resulting in a Si2O5 ratio.
3. Which of the following is the most likely cause of ‘flux melting’ in subduction zones?
A. A decrease in pressure as mantle rock rises toward the surface.
B. The introduction of volatiles, such as water, into the hot mantle wedge.
C. The increase in temperature due to friction between the two plates.
D. Radioactive decay within the subducting oceanic crust.
Answer: B
Conceptual Explanation: Volatiles (mostly water) released from the subducting slab
lower the melting temperature of the overlying mantle peridotite, causing flux melting.
4. According to Bowen’s Reaction Series, which mineral is the first to crystallize from a cooling
mafic magma?
A. Quartz
B. Biotite
C. Muscovite
, D. Olivine
Answer: D
Conceptual Explanation: Olivine is the highest-temperature mineral in the discontinuous
series and crystallizes first from a basaltic/mafic melt.
5. A metamorphic facies characterized by high pressure and low temperature, typically found
in subduction zones, is known as:
A. Greenschist facies
B. Granulite facies
C. Blueschist facies
D. Eclogite facies
Answer: C
Conceptual Explanation: Blueschist facies requires high pressure and relatively low
temperatures, conditions unique to the rapid subduction of oceanic lithosphere.
6. Which type of unconformity involves sedimentary layers deposited over older, eroded
igneous or metamorphic rocks?
A. Disconformity
B. Angular unconformity
C. Paraconformity
D. Nonconformity
