ESS 101B Laboratory 2 Prep 2026 | Plate Tectonics & Rock
Cycle | 200 Practice Questions with Answers & Explanations
SECTION A: PLATE TECTONICS – FUNDAMENTALS AND BOUNDARIES (Questions 1–70)
1. A geologist measures the age of oceanic crust at increasing distances from a mid-ocean ridge. Which
pattern would confirm seafloor spreading?
A. Age increases symmetrically away from the ridge
B. Age decreases symmetrically away from the ridge
C. Age is random with no correlation
D. Age is constant across the ocean basin
Answer: A
Explanation: Paleomagnetic and drill data show that oceanic crust is youngest at ridges and
progressively older toward subduction zones, confirming seafloor spreading.
2. At a convergent boundary where an oceanic plate subducts beneath a continental plate, which
feature is NOT typically formed?
A. Rift valley
B. Deep ocean trench
C. Volcanic arc
D. Metamorphic belt
Answer: A
Explanation: Rift valleys form at divergent boundaries; trenches, volcanic arcs, and metamorphic belts
occur at convergent margins.
3. A transform boundary is characterized by:
A. Horizontal sliding of plates past each other without creating or destroying lithosphere
B. Plates moving toward each other with subduction
C. Plates moving apart with seafloor spreading
,D. Plates moving vertically with uplift
Answer: A
Explanation: Transform faults accommodate horizontal motion; lithosphere is neither created nor
destroyed.
4. The San Andreas Fault in California is a classic example of which type of plate boundary?
A. Transform
B. Divergent
C. Convergent (ocean-continent)
D. Convergent (continent-continent)
Answer: A
Explanation: The San Andreas Fault is a right-lateral strike-slip fault marking the boundary between the
Pacific Plate and the North American Plate.
5. A deep-focus earthquake (magnitude 7.0) occurs at a depth of 600 km beneath an island arc. This
earthquake is most likely associated with:
A. Subduction of a cold, dense slab into the mantle
B. Magma movement in a hotspot
C. Rifting at a mid-ocean ridge
D. Strike-slip motion on a transform fault
Answer: A
Explanation: Deep earthquakes occur only in subduction zones where cold slabs remain brittle to great
depths.
6. Which of the following is NOT a piece of evidence that supported the theory of continental drift
before the discovery of plate tectonics?
A. Matching fossil assemblages across oceans
B. Paleoclimatic evidence of past glaciation in now tropical regions
C. Seafloor magnetic stripe patterns
D. Geometric fit of continental margins
,Answer: C
Explanation: Seafloor magnetic stripes were discovered after the development of plate tectonic theory;
the other lines of evidence were used by Wegener.
7. At a divergent boundary on land (continental rift), the expected rock type and topographic feature
are:
A. Basalt and a valley (graben)
B. Granite and a mountain range
C. Andesite and a volcanic arc
D. Rhyolite and a plateau
Answer: A
Explanation: Continental rifting produces basaltic volcanism and normal faulting, creating a rift valley
(e.g., East African Rift).
8. A geologist finds a piece of oceanic crust that is 180 million years old. Where is this rock most likely
located relative to a mid-ocean ridge?
A. Far from the ridge, near a subduction zone
B. Directly at the ridge axis
C. Within 100 km of the ridge
D. In the middle of an abyssal plain with no relation
Answer: A
Explanation: Oceanic crust older than 150-180 Ma is typically found only at passive margins or near
trenches because older crust has been subducted.
9. Which of the following plate boundaries is most likely to produce a large mountain range composed
of folded and thrust-faulted sedimentary rocks?
A. Continent-continent convergent boundary
B. Ocean-continent convergent boundary
C. Divergent boundary
D. Transform boundary
Answer: A
, Explanation: Continent-continent collision (e.g., Himalayas) produces thick crust, folding, and thrust
faulting; no subduction occurs.
10. The Wadati-Benioff zone is a dipping plane of earthquakes that defines the:
A. Subducting slab
B. Mid-ocean ridge axis
C. Transform fault plane
D. Continental rift zone
Answer: A
Explanation: Earthquakes along the Wadati-Benioff zone trace the path of the downgoing slab to depths
of up to 700 km.
11. A volcanic island arc forms at which type of plate boundary?
A. Ocean-ocean convergent
B. Ocean-continent convergent
C. Ocean-ocean divergent
D. Continent-continent convergent
Answer: A
Explanation: When two oceanic plates converge, one subducts, and the overriding plate produces a
chain of volcanic islands (e.g., Mariana Islands).
12. Which statement best describes the motion of the Pacific Plate relative to the Hawaiian hotspot?
A. The Pacific Plate moves northwest, creating a chain of older volcanoes to the northwest
B. The Pacific Plate moves southeast, creating older volcanoes to the southeast
C. The Pacific Plate is stationary, and the hotspot moves
D. The plate moves randomly, producing no age progression
Answer: A
Explanation: The Hawaiian-Emperor seamount chain shows increasing age to the northwest, indicating
plate motion over a fixed hotspot.
Cycle | 200 Practice Questions with Answers & Explanations
SECTION A: PLATE TECTONICS – FUNDAMENTALS AND BOUNDARIES (Questions 1–70)
1. A geologist measures the age of oceanic crust at increasing distances from a mid-ocean ridge. Which
pattern would confirm seafloor spreading?
A. Age increases symmetrically away from the ridge
B. Age decreases symmetrically away from the ridge
C. Age is random with no correlation
D. Age is constant across the ocean basin
Answer: A
Explanation: Paleomagnetic and drill data show that oceanic crust is youngest at ridges and
progressively older toward subduction zones, confirming seafloor spreading.
2. At a convergent boundary where an oceanic plate subducts beneath a continental plate, which
feature is NOT typically formed?
A. Rift valley
B. Deep ocean trench
C. Volcanic arc
D. Metamorphic belt
Answer: A
Explanation: Rift valleys form at divergent boundaries; trenches, volcanic arcs, and metamorphic belts
occur at convergent margins.
3. A transform boundary is characterized by:
A. Horizontal sliding of plates past each other without creating or destroying lithosphere
B. Plates moving toward each other with subduction
C. Plates moving apart with seafloor spreading
,D. Plates moving vertically with uplift
Answer: A
Explanation: Transform faults accommodate horizontal motion; lithosphere is neither created nor
destroyed.
4. The San Andreas Fault in California is a classic example of which type of plate boundary?
A. Transform
B. Divergent
C. Convergent (ocean-continent)
D. Convergent (continent-continent)
Answer: A
Explanation: The San Andreas Fault is a right-lateral strike-slip fault marking the boundary between the
Pacific Plate and the North American Plate.
5. A deep-focus earthquake (magnitude 7.0) occurs at a depth of 600 km beneath an island arc. This
earthquake is most likely associated with:
A. Subduction of a cold, dense slab into the mantle
B. Magma movement in a hotspot
C. Rifting at a mid-ocean ridge
D. Strike-slip motion on a transform fault
Answer: A
Explanation: Deep earthquakes occur only in subduction zones where cold slabs remain brittle to great
depths.
6. Which of the following is NOT a piece of evidence that supported the theory of continental drift
before the discovery of plate tectonics?
A. Matching fossil assemblages across oceans
B. Paleoclimatic evidence of past glaciation in now tropical regions
C. Seafloor magnetic stripe patterns
D. Geometric fit of continental margins
,Answer: C
Explanation: Seafloor magnetic stripes were discovered after the development of plate tectonic theory;
the other lines of evidence were used by Wegener.
7. At a divergent boundary on land (continental rift), the expected rock type and topographic feature
are:
A. Basalt and a valley (graben)
B. Granite and a mountain range
C. Andesite and a volcanic arc
D. Rhyolite and a plateau
Answer: A
Explanation: Continental rifting produces basaltic volcanism and normal faulting, creating a rift valley
(e.g., East African Rift).
8. A geologist finds a piece of oceanic crust that is 180 million years old. Where is this rock most likely
located relative to a mid-ocean ridge?
A. Far from the ridge, near a subduction zone
B. Directly at the ridge axis
C. Within 100 km of the ridge
D. In the middle of an abyssal plain with no relation
Answer: A
Explanation: Oceanic crust older than 150-180 Ma is typically found only at passive margins or near
trenches because older crust has been subducted.
9. Which of the following plate boundaries is most likely to produce a large mountain range composed
of folded and thrust-faulted sedimentary rocks?
A. Continent-continent convergent boundary
B. Ocean-continent convergent boundary
C. Divergent boundary
D. Transform boundary
Answer: A
, Explanation: Continent-continent collision (e.g., Himalayas) produces thick crust, folding, and thrust
faulting; no subduction occurs.
10. The Wadati-Benioff zone is a dipping plane of earthquakes that defines the:
A. Subducting slab
B. Mid-ocean ridge axis
C. Transform fault plane
D. Continental rift zone
Answer: A
Explanation: Earthquakes along the Wadati-Benioff zone trace the path of the downgoing slab to depths
of up to 700 km.
11. A volcanic island arc forms at which type of plate boundary?
A. Ocean-ocean convergent
B. Ocean-continent convergent
C. Ocean-ocean divergent
D. Continent-continent convergent
Answer: A
Explanation: When two oceanic plates converge, one subducts, and the overriding plate produces a
chain of volcanic islands (e.g., Mariana Islands).
12. Which statement best describes the motion of the Pacific Plate relative to the Hawaiian hotspot?
A. The Pacific Plate moves northwest, creating a chain of older volcanoes to the northwest
B. The Pacific Plate moves southeast, creating older volcanoes to the southeast
C. The Pacific Plate is stationary, and the hotspot moves
D. The plate moves randomly, producing no age progression
Answer: A
Explanation: The Hawaiian-Emperor seamount chain shows increasing age to the northwest, indicating
plate motion over a fixed hotspot.
