GEOLOGY 1001 SOLUTION MANUAL
Course: Introductory
COMPREHENSIVE FINAL EXAMINATION — OFFICIAL ANSWER KEY & Geology
RATIONALES Total Questions: 50
1. Seismic body waves that travel fastest through the Earth and can propagate through solids, liquids,
and gases are:
Answer: A P-waves (Primary waves)
RATIONALE: P-waves are compressional longitudinal body waves. Because all phases of matter resist volumetric
compression, P-waves travel through solids, liquids, and gases.
2. Seismic shear waves (S-waves) cannot propagate through which Earth interior layer?
Answer: C outer core
RATIONALE: S-waves rely on shear strength to propagate. Because liquids have zero shear strength, S-waves cannot
travel through the liquid outer core, creating an S-wave shadow zone beyond $103^\circ$.
3. The boundary separating the crust from the underlying mantle is known as the:
Answer: B Mohorovičić discontinuity (Moho)
RATIONALE: Discovered in 1909 by Andrija Mohorovičić, the Moho represents a compositionally sharp boundary marked
by a jump in P-wave velocity from $\approx 6.5\text{ km/s}$ (crust) to $\approx 8.0\text{ km/s}$ (peridotite mantle).
4. The point within the Earth where energy is first released during an earthquake fault slip is the:
Answer: D focus (hypocenter)
RATIONALE: The focus (or hypocenter) is the exact 3D subterranean origin of rupture along a fault plane. The epicenter is
the point on Earth's surface directly above it.
5. How many seismic station recording intervals are required at minimum to locate an earthquake
epicenter?
Answer: C 3
RATIONALE: Triangulation requires at least 3 seismic stations. The S-minus-P arrival time difference determines distance,
and the intersection of 3 distance circles identifies the epicenter.
6. Earthquake magnitude measured on the Moment Magnitude Scale ($M_w$) quantifies:
Answer: B total energy released during rupture
RATIONALE: Moment Magnitude calculates energy released based on rock rigidity, fault surface rupture area, and average
slip displacement along the fault.
7. Each whole-number increase on the logarithmic earthquake magnitude scale corresponds to an
energy release increase of approximately:
Answer: E 32-fold
RATIONALE: Energy release scales exponentially as $10^{1.5} \approx 31.6$ (roughly a 32-fold increase in seismic energy
per single magnitude step).
GEOLOGY 1001 — Final Exam Answer Key Page 1 of 5
, 10. The principle of relative dating stating that in undisturbed sedimentary sequences, older rocks lie at
the bottom is:
Answer: B Principle of Superposition
RATIONALE: Formulated by Nicolas Steno, Superposition dictates that successive sedimentary layers accumulate on top
of older pre-existing layers.
11. A geological cross-cutting feature (such as an igneous dike or fault line) is always:
Answer: A younger than the rock layers it cuts through
RATIONALE: The Principle of Cross-Cutting Relationships states that a geological feature must exist prior to being
fractured or intruded by a newer feature.
12. The time required for one-half of the unstable parent radioisotopes in a sample to decay into
daughter products is:
Answer: C half-life
RATIONALE: Half-life ($t_{1/2}$) is a constant nuclear decay rate specific to each radioactive isotope system (e.g., U-Pb,
C-14, K-Ar).
13. If a rock sample retains $25\%$ of its original parent isotope and $75\%$ daughter isotope, how many
half-lives have elapsed?
Answer: B 2 half-lives
RATIONALE: $100\% \xrightarrow{t_{1/2}} 50\% \xrightarrow{t_{1/2}} 25\%$ parent remaining. Two half-lives have passed
($1/2 \times 1/2 = 1/4 = 25\%$).
14. Radiocarbon ($^{14}\text{C}$) dating is suitable for dating geological or archaeological materials up
to approximately:
Answer: D 50,000 years old
RATIONALE: Due to Carbon-14's short half-life ($5,730\text{ years}$), insufficient parent atoms remain after $\approx
50,000\text{ years}$ for precise measurement.
15. The eon representing the vast expanse of Earth history prior to the explosion of complex shell-
bearing life is the:
Answer: E Precambrian (Hadean, Archean, Proterozoic)
RATIONALE: The Precambrian spans from Earth's origin ($4.54\text{ Ga}$) to the base of the Cambrian period ($541\text{
Ma}$), accounting for nearly $88\%$ of Earth history.
16. The era known colloquially as the "Age of Reptiles" or "Age of Dinosaurs" is the:
Answer: B Mesozoic Era
RATIONALE: The Mesozoic Era ($252\text{--}66\text{ Ma}$), comprising the Triassic, Jurassic, and Cretaceous periods,
was dominated by archosaurian reptiles.
17. The largest mass extinction event in Earth history occurred at the boundary between which
geological periods?
Answer: A Permian and Triassic (P-T extinction)
GEOLOGY 1001 — Final Exam Answer Key Page 2 of 5
Course: Introductory
COMPREHENSIVE FINAL EXAMINATION — OFFICIAL ANSWER KEY & Geology
RATIONALES Total Questions: 50
1. Seismic body waves that travel fastest through the Earth and can propagate through solids, liquids,
and gases are:
Answer: A P-waves (Primary waves)
RATIONALE: P-waves are compressional longitudinal body waves. Because all phases of matter resist volumetric
compression, P-waves travel through solids, liquids, and gases.
2. Seismic shear waves (S-waves) cannot propagate through which Earth interior layer?
Answer: C outer core
RATIONALE: S-waves rely on shear strength to propagate. Because liquids have zero shear strength, S-waves cannot
travel through the liquid outer core, creating an S-wave shadow zone beyond $103^\circ$.
3. The boundary separating the crust from the underlying mantle is known as the:
Answer: B Mohorovičić discontinuity (Moho)
RATIONALE: Discovered in 1909 by Andrija Mohorovičić, the Moho represents a compositionally sharp boundary marked
by a jump in P-wave velocity from $\approx 6.5\text{ km/s}$ (crust) to $\approx 8.0\text{ km/s}$ (peridotite mantle).
4. The point within the Earth where energy is first released during an earthquake fault slip is the:
Answer: D focus (hypocenter)
RATIONALE: The focus (or hypocenter) is the exact 3D subterranean origin of rupture along a fault plane. The epicenter is
the point on Earth's surface directly above it.
5. How many seismic station recording intervals are required at minimum to locate an earthquake
epicenter?
Answer: C 3
RATIONALE: Triangulation requires at least 3 seismic stations. The S-minus-P arrival time difference determines distance,
and the intersection of 3 distance circles identifies the epicenter.
6. Earthquake magnitude measured on the Moment Magnitude Scale ($M_w$) quantifies:
Answer: B total energy released during rupture
RATIONALE: Moment Magnitude calculates energy released based on rock rigidity, fault surface rupture area, and average
slip displacement along the fault.
7. Each whole-number increase on the logarithmic earthquake magnitude scale corresponds to an
energy release increase of approximately:
Answer: E 32-fold
RATIONALE: Energy release scales exponentially as $10^{1.5} \approx 31.6$ (roughly a 32-fold increase in seismic energy
per single magnitude step).
GEOLOGY 1001 — Final Exam Answer Key Page 1 of 5
, 10. The principle of relative dating stating that in undisturbed sedimentary sequences, older rocks lie at
the bottom is:
Answer: B Principle of Superposition
RATIONALE: Formulated by Nicolas Steno, Superposition dictates that successive sedimentary layers accumulate on top
of older pre-existing layers.
11. A geological cross-cutting feature (such as an igneous dike or fault line) is always:
Answer: A younger than the rock layers it cuts through
RATIONALE: The Principle of Cross-Cutting Relationships states that a geological feature must exist prior to being
fractured or intruded by a newer feature.
12. The time required for one-half of the unstable parent radioisotopes in a sample to decay into
daughter products is:
Answer: C half-life
RATIONALE: Half-life ($t_{1/2}$) is a constant nuclear decay rate specific to each radioactive isotope system (e.g., U-Pb,
C-14, K-Ar).
13. If a rock sample retains $25\%$ of its original parent isotope and $75\%$ daughter isotope, how many
half-lives have elapsed?
Answer: B 2 half-lives
RATIONALE: $100\% \xrightarrow{t_{1/2}} 50\% \xrightarrow{t_{1/2}} 25\%$ parent remaining. Two half-lives have passed
($1/2 \times 1/2 = 1/4 = 25\%$).
14. Radiocarbon ($^{14}\text{C}$) dating is suitable for dating geological or archaeological materials up
to approximately:
Answer: D 50,000 years old
RATIONALE: Due to Carbon-14's short half-life ($5,730\text{ years}$), insufficient parent atoms remain after $\approx
50,000\text{ years}$ for precise measurement.
15. The eon representing the vast expanse of Earth history prior to the explosion of complex shell-
bearing life is the:
Answer: E Precambrian (Hadean, Archean, Proterozoic)
RATIONALE: The Precambrian spans from Earth's origin ($4.54\text{ Ga}$) to the base of the Cambrian period ($541\text{
Ma}$), accounting for nearly $88\%$ of Earth history.
16. The era known colloquially as the "Age of Reptiles" or "Age of Dinosaurs" is the:
Answer: B Mesozoic Era
RATIONALE: The Mesozoic Era ($252\text{--}66\text{ Ma}$), comprising the Triassic, Jurassic, and Cretaceous periods,
was dominated by archosaurian reptiles.
17. The largest mass extinction event in Earth history occurred at the boundary between which
geological periods?
Answer: A Permian and Triassic (P-T extinction)
GEOLOGY 1001 — Final Exam Answer Key Page 2 of 5
