G-202 PHYSICAL GEOLOGY: EXAM #2
COMPREHENSIVE QUESTIONS AND
ANSWERS 100% VERIFIED. JUST
RELEASED
1. Which of the following processes is responsible for the formation of magma at subduction
zones?
A. Decompression melting
B. Radioactive decay in the crust
C. Flux melting due to the introduction of volatiles
D. Increase in pressure pushing atoms together
Answer: C
Conceptual Explanation: At subduction zones, water and other volatiles are released from
the subducting oceanic slab, lowering the melting point of the overlying mantle wedge (flux
melting).
2. Which mineral on the Bowen’s Reaction Series is the most stable at Earth’s surface
conditions?
A. Quartz
,B. Pyroxene
C. Calcium-rich Plagioclase
D. Olivine
Answer: A
Conceptual Explanation: Quartz crystallizes at the lowest temperatures in the
discontinuous series and is chemically most resistant to weathering at surface conditions.
3. A volcanic texture characterized by two distinct sizes of crystals is known as:
A. Aphanitic
B. Phaneritic
C. Vesicular
D. Porphyritic
Answer: D
Conceptual Explanation: Porphyritic texture indicates a two-stage cooling history: slow
cooling at depth (forming phenocrysts) followed by rapid cooling at or near the surface
(forming groundmass).
4. Which type of volcano is primarily composed of low-viscosity basaltic lava flows and has a
broad, slightly domed profile?
A. Composite Volcano
B. Cinder Cone
, C. Shield Volcano
D. Lava Dome
Answer: C
Conceptual Explanation: Shield volcanoes, like those in Hawaii, are built from fluid
basaltic lavas that can travel long distances, resulting in a broad shape.
5. The chemical weathering process specifically responsible for the formation of clay minerals
from feldspar is:
A. Oxidation
B. Hydrolysis
C. Dissolution
D. Frost Wedging
Answer: B
Conceptual Explanation: Hydrolysis is the reaction between H+ or OH- ions in water and
minerals, which commonly breaks down silicate minerals like feldspar into clay.
6. In a soil profile, which horizon is known as the ‘Zone of Accumulation’ (or subsoil)?
A. O Horizon
B. A Horizon
C. B Horizon
COMPREHENSIVE QUESTIONS AND
ANSWERS 100% VERIFIED. JUST
RELEASED
1. Which of the following processes is responsible for the formation of magma at subduction
zones?
A. Decompression melting
B. Radioactive decay in the crust
C. Flux melting due to the introduction of volatiles
D. Increase in pressure pushing atoms together
Answer: C
Conceptual Explanation: At subduction zones, water and other volatiles are released from
the subducting oceanic slab, lowering the melting point of the overlying mantle wedge (flux
melting).
2. Which mineral on the Bowen’s Reaction Series is the most stable at Earth’s surface
conditions?
A. Quartz
,B. Pyroxene
C. Calcium-rich Plagioclase
D. Olivine
Answer: A
Conceptual Explanation: Quartz crystallizes at the lowest temperatures in the
discontinuous series and is chemically most resistant to weathering at surface conditions.
3. A volcanic texture characterized by two distinct sizes of crystals is known as:
A. Aphanitic
B. Phaneritic
C. Vesicular
D. Porphyritic
Answer: D
Conceptual Explanation: Porphyritic texture indicates a two-stage cooling history: slow
cooling at depth (forming phenocrysts) followed by rapid cooling at or near the surface
(forming groundmass).
4. Which type of volcano is primarily composed of low-viscosity basaltic lava flows and has a
broad, slightly domed profile?
A. Composite Volcano
B. Cinder Cone
, C. Shield Volcano
D. Lava Dome
Answer: C
Conceptual Explanation: Shield volcanoes, like those in Hawaii, are built from fluid
basaltic lavas that can travel long distances, resulting in a broad shape.
5. The chemical weathering process specifically responsible for the formation of clay minerals
from feldspar is:
A. Oxidation
B. Hydrolysis
C. Dissolution
D. Frost Wedging
Answer: B
Conceptual Explanation: Hydrolysis is the reaction between H+ or OH- ions in water and
minerals, which commonly breaks down silicate minerals like feldspar into clay.
6. In a soil profile, which horizon is known as the ‘Zone of Accumulation’ (or subsoil)?
A. O Horizon
B. A Horizon
C. B Horizon
