GLG 103 Lab 3: Plate Tectonics | Questions
and Answers | 2026/2027 Updated | Arizona
State University.
Practice Question Bank & Answer Rationale
THIS PACK CONTAINS
50 exam-style multiple-choice questions. Each question includes the correct answer and a complete rationale
for focused revision.
COVERAGE
This lab exam assesses mastery of plate tectonic theory, including divergent, convergent, and transform
boundaries, seafloor spreading and magnetic anomalies, earthquake and volcano distribution, continental drift
and Pangaea, hotspots and mantle plumes, and modern plate motion evidence from GPS. Questions require
synthesis of geological data, map interpretation, and quantitative reasoning at an advanced undergraduate
level.
STUDY GUIDE
Recommended duration: 2 hours. Passing target: 70%.
HIGHP - Page 1 of 18
,1. A marine magnetic survey across a mid-ocean ridge reveals symmetric magnetic
anomalies with a full spreading rate of 6 cm/yr. If the Brunhes normal chron began 0.78
Ma, what is the expected distance from the ridge axis to the Brunhes-Matuyama reversal
boundary on one flank?
[ ] A. 2.34 km
[ ] B. 4.68 km
[ ] C. 23.4 km
[ ] D. 46.8 km
CORRECT: C. 23.4 km
Half-spreading rate = 3 cm/yr. Distance = 3 cm/yr × 780,000 yr = 2,340,000 cm = 23.4 km. Option A is half
the correct distance, B is double, and D is ten times too large.
2. Which observation best distinguishes a transform plate boundary from a divergent plate
boundary in a continental setting?
[ ] A. Presence of shallow-focus earthquakes
[ ] B. Offset of pre-existing linear features (e.g., streams, roads) with no volcanic activity
[ ] C. High heat flow and crustal thinning
[ ] D. Normal faulting and basin formation
CORRECT: B. Offset of pre-existing linear features (e.g., streams, roads) with no volcanic activity
Transform boundaries are characterized by strike-slip faulting that offsets linear features, with minimal
volcanism. Divergent boundaries exhibit normal faulting, high heat flow, and crustal thinning. Options A, C,
and D are typical of divergent boundaries, not transform.
3. A deep-ocean trench, a volcanic arc, and a Benioff zone dipping ~45° are present.
Which plate boundary type and associated seismic pattern is most consistent with this
setting?
[ ] A. Divergent boundary with shallow seismicity
[ ] B. Transform boundary with intermediate-depth seismicity
[ ] C. Ocean-ocean convergent boundary with a Wadati-Benioff zone
[ ] D. Continental rift with deep seismicity
CORRECT: C. Ocean-ocean convergent boundary with a Wadati-Benioff zone
A trench, volcanic arc, and dipping Benioff zone indicate subduction, typical of ocean-ocean convergence.
Divergent and transform boundaries lack deep subduction seismicity. Continental rifts produce shallow
seismicity without a Benioff zone.
HIGHP - Page 2 of 18
, 4. Which set of evidence was most critical in demonstrating that continents have moved
horizontally over Earth's surface?
[ ] A. Matching mountain belts, glacial striations, and fossil distributions across now-separated
continents
[ ] B. Identical rock types found on all continents
[ ] C. Uniform sediment thickness on all continental shelves
[ ] D. Similar ages of oceanic crust in all ocean basins
CORRECT: A. Matching mountain belts, glacial striations, and fossil distributions across
now-separated continents
Matching mountain belts, glacial striations, and fossil distributions across continents provided key evidence
for continental drift. Options B, C, and D are either too general or incorrect because oceanic crust ages vary
systematically.
5. A hotspot track on the Pacific Plate shows a bend at ~47 Ma. What does this bend most
directly indicate?
[ ] A. A change in the direction of absolute plate motion
[ ] B. A sudden increase in mantle plume temperature
[ ] C. A reversal in Earth's magnetic field
[ ] D. A change in the rate of seafloor spreading
CORRECT: A. A change in the direction of absolute plate motion
The Hawaiian-Emperor bend records a change in Pacific Plate motion direction relative to the fixed hotspot.
Magnetic reversals and spreading rate changes do not cause such bends. Plume temperature changes
would affect volume, not direction.
6. GPS measurements show that a station on the Nazca Plate moves eastward at 65 mm/yr
relative to a stable South American station. What does this most directly constrain?
[ ] A. The absolute motion of the Nazca Plate only
[ ] B. The relative convergence rate between the Nazca and South American Plates
[ ] C. The rate of seafloor spreading at the East Pacific Rise
[ ] D. The rate of hotspot motion beneath the Nazca Plate
CORRECT: B. The relative convergence rate between the Nazca and South American Plates
GPS relative motion between two plates directly gives their relative convergence rate. Absolute motion
requires a fixed reference frame. Spreading rate at the East Pacific Rise involves other plates, and hotspot
motion is independent.
HIGHP - Page 3 of 18
and Answers | 2026/2027 Updated | Arizona
State University.
Practice Question Bank & Answer Rationale
THIS PACK CONTAINS
50 exam-style multiple-choice questions. Each question includes the correct answer and a complete rationale
for focused revision.
COVERAGE
This lab exam assesses mastery of plate tectonic theory, including divergent, convergent, and transform
boundaries, seafloor spreading and magnetic anomalies, earthquake and volcano distribution, continental drift
and Pangaea, hotspots and mantle plumes, and modern plate motion evidence from GPS. Questions require
synthesis of geological data, map interpretation, and quantitative reasoning at an advanced undergraduate
level.
STUDY GUIDE
Recommended duration: 2 hours. Passing target: 70%.
HIGHP - Page 1 of 18
,1. A marine magnetic survey across a mid-ocean ridge reveals symmetric magnetic
anomalies with a full spreading rate of 6 cm/yr. If the Brunhes normal chron began 0.78
Ma, what is the expected distance from the ridge axis to the Brunhes-Matuyama reversal
boundary on one flank?
[ ] A. 2.34 km
[ ] B. 4.68 km
[ ] C. 23.4 km
[ ] D. 46.8 km
CORRECT: C. 23.4 km
Half-spreading rate = 3 cm/yr. Distance = 3 cm/yr × 780,000 yr = 2,340,000 cm = 23.4 km. Option A is half
the correct distance, B is double, and D is ten times too large.
2. Which observation best distinguishes a transform plate boundary from a divergent plate
boundary in a continental setting?
[ ] A. Presence of shallow-focus earthquakes
[ ] B. Offset of pre-existing linear features (e.g., streams, roads) with no volcanic activity
[ ] C. High heat flow and crustal thinning
[ ] D. Normal faulting and basin formation
CORRECT: B. Offset of pre-existing linear features (e.g., streams, roads) with no volcanic activity
Transform boundaries are characterized by strike-slip faulting that offsets linear features, with minimal
volcanism. Divergent boundaries exhibit normal faulting, high heat flow, and crustal thinning. Options A, C,
and D are typical of divergent boundaries, not transform.
3. A deep-ocean trench, a volcanic arc, and a Benioff zone dipping ~45° are present.
Which plate boundary type and associated seismic pattern is most consistent with this
setting?
[ ] A. Divergent boundary with shallow seismicity
[ ] B. Transform boundary with intermediate-depth seismicity
[ ] C. Ocean-ocean convergent boundary with a Wadati-Benioff zone
[ ] D. Continental rift with deep seismicity
CORRECT: C. Ocean-ocean convergent boundary with a Wadati-Benioff zone
A trench, volcanic arc, and dipping Benioff zone indicate subduction, typical of ocean-ocean convergence.
Divergent and transform boundaries lack deep subduction seismicity. Continental rifts produce shallow
seismicity without a Benioff zone.
HIGHP - Page 2 of 18
, 4. Which set of evidence was most critical in demonstrating that continents have moved
horizontally over Earth's surface?
[ ] A. Matching mountain belts, glacial striations, and fossil distributions across now-separated
continents
[ ] B. Identical rock types found on all continents
[ ] C. Uniform sediment thickness on all continental shelves
[ ] D. Similar ages of oceanic crust in all ocean basins
CORRECT: A. Matching mountain belts, glacial striations, and fossil distributions across
now-separated continents
Matching mountain belts, glacial striations, and fossil distributions across continents provided key evidence
for continental drift. Options B, C, and D are either too general or incorrect because oceanic crust ages vary
systematically.
5. A hotspot track on the Pacific Plate shows a bend at ~47 Ma. What does this bend most
directly indicate?
[ ] A. A change in the direction of absolute plate motion
[ ] B. A sudden increase in mantle plume temperature
[ ] C. A reversal in Earth's magnetic field
[ ] D. A change in the rate of seafloor spreading
CORRECT: A. A change in the direction of absolute plate motion
The Hawaiian-Emperor bend records a change in Pacific Plate motion direction relative to the fixed hotspot.
Magnetic reversals and spreading rate changes do not cause such bends. Plume temperature changes
would affect volume, not direction.
6. GPS measurements show that a station on the Nazca Plate moves eastward at 65 mm/yr
relative to a stable South American station. What does this most directly constrain?
[ ] A. The absolute motion of the Nazca Plate only
[ ] B. The relative convergence rate between the Nazca and South American Plates
[ ] C. The rate of seafloor spreading at the East Pacific Rise
[ ] D. The rate of hotspot motion beneath the Nazca Plate
CORRECT: B. The relative convergence rate between the Nazca and South American Plates
GPS relative motion between two plates directly gives their relative convergence rate. Absolute motion
requires a fixed reference frame. Spreading rate at the East Pacific Rise involves other plates, and hotspot
motion is independent.
HIGHP - Page 3 of 18
