GEOL 1121L Lab 4: Rock Cycle and Igneous Rocks Exam 2026 GSU
1. Which process transforms any rock type into sediment?
A. Weathering and erosion
B. Melting and cooling
C. Heat and pressure
D. Lithification
Answer: A
Rationale: Weathering and erosion break down existing rocks into smaller particles called
sediment.
2. What is the primary difference between magma and lava?
A. Location (underground vs. surface)
B. Temperature
C. Chemical composition
D. Density
Answer: A
Rationale: Magma is molten rock below the Earth’s surface, while lava is molten rock that
has reached the surface.
3. Which igneous texture indicates two distinct stages of cooling?
A. Porphyritic
B. Aphanitic
C. Phaneritic
D. Glassy
Answer: A
Rationale: Porphyritic texture features large crystals (phenocrysts) indicating slow
cooling and a fine-grained matrix indicating faster cooling.
,4. An igneous rock that cools very slowly deep underground will most likely
have which texture?
A. Aphanitic
B. Phaneritic
C. Vesicular
D. Pyroclastic
Answer: B
Rationale: Slow cooling allows minerals to grow large enough to be seen with the naked
eye, resulting in a phaneritic texture.
5. Which of the following minerals is the first to crystallize from a cooling
magma according to Bowen’s Reaction Series?
A. Quartz
B. Olivine
C. Biotite
D. Muscovite
Answer: B
Rationale: Olivine is a high-temperature mineral and the first to crystallize in the
discontinuous series.
6. Felsic igneous rocks are primarily composed of which minerals?
A. Pyroxene and Olivine
B. Calcium-rich Plagioclase
C. Amphibole and Biotite
D. Quartz and Potassium Feldspar
Answer: D
Rationale: Felsic rocks are rich in silica and contain light-colored minerals like quartz and
feldspar.
, 7. What causes the vesicular texture found in rocks like scoria and pumice?
A. Gas bubbles trapped in cooling lava
B. High pressure during formation
C. Rapid cooling in water
D. Slow cooling in a magma chamber
Answer: A
Rationale: Vesicles are small holes formed by gas escaping from lava as it solidifies.
8. Which rock is the extrusive equivalent of granite?
A. Basalt
B. Rhyolite
C. Andesite
D. Gabbro
Answer: B
Rationale: Granite and rhyolite share the same felsic composition; granite is intrusive
(coarse-grained) and rhyolite is extrusive (fine-grained).
9. Mafic rocks are typically what color compared to felsic rocks?
A. Lighter
B. Pinker
C. Darker
D. More transparent
Answer: C
Rationale: Mafic rocks contain high amounts of magnesium and iron-rich minerals, making
them dark grey or black.
1. Which process transforms any rock type into sediment?
A. Weathering and erosion
B. Melting and cooling
C. Heat and pressure
D. Lithification
Answer: A
Rationale: Weathering and erosion break down existing rocks into smaller particles called
sediment.
2. What is the primary difference between magma and lava?
A. Location (underground vs. surface)
B. Temperature
C. Chemical composition
D. Density
Answer: A
Rationale: Magma is molten rock below the Earth’s surface, while lava is molten rock that
has reached the surface.
3. Which igneous texture indicates two distinct stages of cooling?
A. Porphyritic
B. Aphanitic
C. Phaneritic
D. Glassy
Answer: A
Rationale: Porphyritic texture features large crystals (phenocrysts) indicating slow
cooling and a fine-grained matrix indicating faster cooling.
,4. An igneous rock that cools very slowly deep underground will most likely
have which texture?
A. Aphanitic
B. Phaneritic
C. Vesicular
D. Pyroclastic
Answer: B
Rationale: Slow cooling allows minerals to grow large enough to be seen with the naked
eye, resulting in a phaneritic texture.
5. Which of the following minerals is the first to crystallize from a cooling
magma according to Bowen’s Reaction Series?
A. Quartz
B. Olivine
C. Biotite
D. Muscovite
Answer: B
Rationale: Olivine is a high-temperature mineral and the first to crystallize in the
discontinuous series.
6. Felsic igneous rocks are primarily composed of which minerals?
A. Pyroxene and Olivine
B. Calcium-rich Plagioclase
C. Amphibole and Biotite
D. Quartz and Potassium Feldspar
Answer: D
Rationale: Felsic rocks are rich in silica and contain light-colored minerals like quartz and
feldspar.
, 7. What causes the vesicular texture found in rocks like scoria and pumice?
A. Gas bubbles trapped in cooling lava
B. High pressure during formation
C. Rapid cooling in water
D. Slow cooling in a magma chamber
Answer: A
Rationale: Vesicles are small holes formed by gas escaping from lava as it solidifies.
8. Which rock is the extrusive equivalent of granite?
A. Basalt
B. Rhyolite
C. Andesite
D. Gabbro
Answer: B
Rationale: Granite and rhyolite share the same felsic composition; granite is intrusive
(coarse-grained) and rhyolite is extrusive (fine-grained).
9. Mafic rocks are typically what color compared to felsic rocks?
A. Lighter
B. Pinker
C. Darker
D. More transparent
Answer: C
Rationale: Mafic rocks contain high amounts of magnesium and iron-rich minerals, making
them dark grey or black.
