LSU GEOL 1001 EXAM 1, 2 and Final
Exam Questions with Answers Updated
Pass Guaranteed | Verified Questions
LSU GEOL 1001 EXAM 1, 2 and | Comprehensive Examination
LSU GEOL 1001 EXAM 1, 2 and Final Exam Questions with
Answers Updated Pass Guaranteed actual exam preparation
document with verified questions, complete answers, and
INTRODUCTION
This document is an important and very helpful preparation
resource for LSU GEOL 1001 EXAM 1, 2 and Final Exam
Questions with Answers Updated Pass Guaranteed. Every item
uses a focused exam stem, four response options, a keyed
response, and a clear rationale, making it easier to understand
the subject, spot distractors, and build real exam confidence.
Page 1
, Question 1
A seismic tomography cross-section beneath a subduction zone shows a
high-velocity slab dipping to ~600 km, yet intermediate-depth earthquakes
cease abruptly at ~300 km. Which mechanism best explains this cutoff?
A. Brittle failure ceases because confining pressure exceeds rock strength
at that depth.
B. Dehydration embrittlement drives faulting only where hydrous
minerals remain stable; below ~300 km the slab is too dry and too hot to
fracture.
C. The slab reaches the asthenosphere and begins to melt, eliminating
elastic strain accumulation.
D. Phase transformation to ringwoodite absorbs seismic energy,
suppressing rupture.
Correct Answer: B - Dehydration embrittlement drives faulting
only where hydrous minerals remain stable; below ~300 km the
slab is too dry and too hot to fracture.
RATIONALE
Intermediate-depth seismicity in subducting slabs is widely attributed
to dehydration embrittlement - fluids released from hydrous phases
(e.g., antigorite, lawsonite) reduce effective normal stress and permit
brittle failure. Below ~300 km, hydrous minerals are largely exhausted
and temperatures are too high, so earthquakes cease even though the
slab continues to descend. High confining pressure alone does not
eliminate earthquakes (deep-focus events occur to ~700 km), and
melting is not required.
Question 2
A sandstone thin section shows well-rounded, well-sorted quartz grains with
quartz overgrowths and minor chert fragments. Which depositional setting and
diagenetic history is most consistent?
A. Glacial till deposited rapidly, then buried and metamorphosed at
Page 2
, greenschist facies.
B. Aeolian dune or high-energy beach sand, later subjected to deep burial
and quartz cementation.
C. Deep-marine turbidite deposited by waning flows, with early calcite
cementation.
D. Volcaniclastic debris flow with subsequent zeolite-facies alteration.
Correct Answer: B - Aeolian dune or high-energy beach sand,
later subjected to deep burial and quartz cementation.
RATIONALE
Well-rounded, well-sorted quartz-rich sand indicates prolonged
transport and winnowing typical of aeolian or beach environments.
Quartz overgrowths form during burial diagenesis when
silica-saturated fluids precipitate on detrital quartz. Glacial tills are
poorly sorted, turbidites are graded and matrix-rich, and volcaniclastic
deposits contain abundant lithic and feldspar grains.
Question 3
A granite contains zircon crystals with inherited cores. U-Pb analysis of cores
yields 1.8 Ga, rims yield 1.1 Ga, and whole-rock Rb-Sr yields 0.9 Ga. Which
interpretation is most defensible?
A. The granite crystallized at 1.8 Ga and was later metamorphosed at 1.1
Ga; the 0.9 Ga age is a cooling age.
B. The granite crystallized at 1.1 Ga from a 1.8 Ga source; 0.9 Ga reflects
later thermal resetting of Rb-Sr.
C. The granite crystallized at 0.9 Ga; zircon cores and rims are both
inherited xenocrysts.
D. All three ages are unreliable because different isotopic systems cannot
be compared.
Correct Answer: B - The granite crystallized at 1.1 Ga from a 1.8
Ga source; 0.9 Ga reflects later thermal resetting of Rb-Sr.
Page 3
, RATIONALE
Zircon rims record the crystallization age of the host magma (1.1 Ga),
while cores are inherited from a 1.8 Ga source. Rb-Sr whole-rock ages
are sensitive to later thermal events; 0.9 Ga likely reflects a
subsequent metamorphic or hydrothermal resetting. This is a classic
example of using multiple chronometers to disentangle magmatic and
metamorphic histories.
Question 4
A region experiences a magnitude 7.2 earthquake at 15 km depth on a reverse
fault. Which combination of secondary hazards is most likely to be amplified
by local site conditions?
A. Tsunami and volcanic eruption
B. Liquefaction and ground shaking amplification in unconsolidated
sediments
C. Fault creep and aseismic slip
D. Isostatic rebound and glacial surges
Correct Answer: B - Liquefaction and ground shaking
amplification in unconsolidated sediments
RATIONALE
Shallow reverse-fault earthquakes produce strong ground shaking that
is amplified in soft, water-saturated sediments, promoting
liquefaction. Tsunamis require offshore displacement, volcanic
eruptions are unrelated, and creep/asiesmic slip are not secondary
hazards of a single event.
Question 5
A metamorphic rock contains garnet porphyroblasts with inclusion trails that
are straight and continuous with the matrix foliation, while the matrix wraps
around the garnets. What does this texture indicate?
A. The garnets grew after the foliation formed and were rotated by later
Page 4
Exam Questions with Answers Updated
Pass Guaranteed | Verified Questions
LSU GEOL 1001 EXAM 1, 2 and | Comprehensive Examination
LSU GEOL 1001 EXAM 1, 2 and Final Exam Questions with
Answers Updated Pass Guaranteed actual exam preparation
document with verified questions, complete answers, and
INTRODUCTION
This document is an important and very helpful preparation
resource for LSU GEOL 1001 EXAM 1, 2 and Final Exam
Questions with Answers Updated Pass Guaranteed. Every item
uses a focused exam stem, four response options, a keyed
response, and a clear rationale, making it easier to understand
the subject, spot distractors, and build real exam confidence.
Page 1
, Question 1
A seismic tomography cross-section beneath a subduction zone shows a
high-velocity slab dipping to ~600 km, yet intermediate-depth earthquakes
cease abruptly at ~300 km. Which mechanism best explains this cutoff?
A. Brittle failure ceases because confining pressure exceeds rock strength
at that depth.
B. Dehydration embrittlement drives faulting only where hydrous
minerals remain stable; below ~300 km the slab is too dry and too hot to
fracture.
C. The slab reaches the asthenosphere and begins to melt, eliminating
elastic strain accumulation.
D. Phase transformation to ringwoodite absorbs seismic energy,
suppressing rupture.
Correct Answer: B - Dehydration embrittlement drives faulting
only where hydrous minerals remain stable; below ~300 km the
slab is too dry and too hot to fracture.
RATIONALE
Intermediate-depth seismicity in subducting slabs is widely attributed
to dehydration embrittlement - fluids released from hydrous phases
(e.g., antigorite, lawsonite) reduce effective normal stress and permit
brittle failure. Below ~300 km, hydrous minerals are largely exhausted
and temperatures are too high, so earthquakes cease even though the
slab continues to descend. High confining pressure alone does not
eliminate earthquakes (deep-focus events occur to ~700 km), and
melting is not required.
Question 2
A sandstone thin section shows well-rounded, well-sorted quartz grains with
quartz overgrowths and minor chert fragments. Which depositional setting and
diagenetic history is most consistent?
A. Glacial till deposited rapidly, then buried and metamorphosed at
Page 2
, greenschist facies.
B. Aeolian dune or high-energy beach sand, later subjected to deep burial
and quartz cementation.
C. Deep-marine turbidite deposited by waning flows, with early calcite
cementation.
D. Volcaniclastic debris flow with subsequent zeolite-facies alteration.
Correct Answer: B - Aeolian dune or high-energy beach sand,
later subjected to deep burial and quartz cementation.
RATIONALE
Well-rounded, well-sorted quartz-rich sand indicates prolonged
transport and winnowing typical of aeolian or beach environments.
Quartz overgrowths form during burial diagenesis when
silica-saturated fluids precipitate on detrital quartz. Glacial tills are
poorly sorted, turbidites are graded and matrix-rich, and volcaniclastic
deposits contain abundant lithic and feldspar grains.
Question 3
A granite contains zircon crystals with inherited cores. U-Pb analysis of cores
yields 1.8 Ga, rims yield 1.1 Ga, and whole-rock Rb-Sr yields 0.9 Ga. Which
interpretation is most defensible?
A. The granite crystallized at 1.8 Ga and was later metamorphosed at 1.1
Ga; the 0.9 Ga age is a cooling age.
B. The granite crystallized at 1.1 Ga from a 1.8 Ga source; 0.9 Ga reflects
later thermal resetting of Rb-Sr.
C. The granite crystallized at 0.9 Ga; zircon cores and rims are both
inherited xenocrysts.
D. All three ages are unreliable because different isotopic systems cannot
be compared.
Correct Answer: B - The granite crystallized at 1.1 Ga from a 1.8
Ga source; 0.9 Ga reflects later thermal resetting of Rb-Sr.
Page 3
, RATIONALE
Zircon rims record the crystallization age of the host magma (1.1 Ga),
while cores are inherited from a 1.8 Ga source. Rb-Sr whole-rock ages
are sensitive to later thermal events; 0.9 Ga likely reflects a
subsequent metamorphic or hydrothermal resetting. This is a classic
example of using multiple chronometers to disentangle magmatic and
metamorphic histories.
Question 4
A region experiences a magnitude 7.2 earthquake at 15 km depth on a reverse
fault. Which combination of secondary hazards is most likely to be amplified
by local site conditions?
A. Tsunami and volcanic eruption
B. Liquefaction and ground shaking amplification in unconsolidated
sediments
C. Fault creep and aseismic slip
D. Isostatic rebound and glacial surges
Correct Answer: B - Liquefaction and ground shaking
amplification in unconsolidated sediments
RATIONALE
Shallow reverse-fault earthquakes produce strong ground shaking that
is amplified in soft, water-saturated sediments, promoting
liquefaction. Tsunamis require offshore displacement, volcanic
eruptions are unrelated, and creep/asiesmic slip are not secondary
hazards of a single event.
Question 5
A metamorphic rock contains garnet porphyroblasts with inclusion trails that
are straight and continuous with the matrix foliation, while the matrix wraps
around the garnets. What does this texture indicate?
A. The garnets grew after the foliation formed and were rotated by later
Page 4
