ESS 101 B Lab 5 Sedimentary Rocks Quiz Actual Exam
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Section A: Sedimentary Rock Formation Processes
Q1: A student observes a granite boulder in the field that has developed cracks and is
slowly breaking apart into smaller fragments due to repeated freezing and thawing of
water in its fractures. Which weathering process is primarily responsible?
A. Chemical weathering through hydrolysis of feldspar minerals
B. Physical weathering through frost wedging [CORRECT]
C. Chemical weathering through oxidation of iron-bearing minerals
D. Biological weathering through root wedging by tree roots
Correct Answer: B
Rationale: Frost wedging is a physical (mechanical) weathering process where water
freezes in rock fractures, expanding by approximately 9% in volume and exerting
pressure that pries rock apart; repeated freeze-thaw cycles progressively break the rock
into smaller fragments. Hydrolysis and oxidation are chemical processes that alter
mineral composition; root wedging involves biological agents, not freeze-thaw cycles.
Q2: During a field trip, a geology student notices that a basalt outcrop has turned
reddish-brown in color and the feldspar crystals have been altered to clay minerals.
Which chemical weathering process best explains these observations?
A. Dissolution of calcite cement by acidic groundwater
B. Hydrolysis of silicate minerals with conversion to clay minerals and iron oxide
[CORRECT]
,C. Hydration of anhydrite to form gypsum
D. Carbonation of limestone to form calcium bicarbonate
Correct Answer: B
Rationale: Hydrolysis is a chemical weathering process where water reacts with silicate
minerals (such as feldspar in basalt), breaking chemical bonds and converting them to
clay minerals (kaolinite, smectite) while releasing iron that oxidizes to form
reddish-brown iron oxides (hematite, goethite). Dissolution affects carbonate and
evaporite minerals; hydration involves water incorporation into mineral structure;
carbonation specifically involves carbonic acid reacting with carbonate minerals.
Q3: A sedimentary rock sample shows sand grains that are tightly packed together with
calcite crystals filling the pore spaces between grains. Which lithification process is
primarily responsible for converting these loose sediments into solid rock?
A. Compaction alone reducing porosity through grain rearrangement
B. Cementation with precipitation of calcite minerals binding grains together [CORRECT]
C. Recrystallization of quartz grains into larger interlocking crystals
D. Melting and subsequent cooling of sedimentary material
Correct Answer: B
Rationale: Cementation is the lithification process where minerals precipitate from
groundwater into pore spaces between sediment grains, binding them together to form
solid rock; calcite is a common cementing mineral in sedimentary rocks. Compaction
reduces pore space but does not bind grains; recrystallization occurs during diagenesis
but is not the primary lithification mechanism; melting would produce igneous, not
sedimentary, rock.
, Q4: In a laboratory exercise, students are asked to identify the process that reduces the
porosity of buried sediments primarily through the weight of overlying materials forcing
grains closer together. Which term correctly identifies this process?
A. Cementation involving mineral precipitation from groundwater
B. Compaction from the weight of overlying sediments [CORRECT]
C. Lithification encompassing both compaction and cementation
D. Diagenesis including all post-depositional chemical changes
Correct Answer: B
Rationale: Compaction is the physical process where the weight of overlying sediments
compresses buried deposits, reducing pore space by forcing grains closer together and
expelling water; this is distinct from cementation, which involves mineral precipitation.
Lithification is the overall process of turning sediment into rock (compaction +
cementation); diagenesis includes all physical and chemical changes after deposition.
Q5: A geology student observes that a sandstone outcrop has iron oxide staining
(reddish coloration) and the individual quartz grains appear to be held together by a
reddish mineral material filling the spaces between grains. Which combination of
processes and materials best explains these features?
A. Chemical weathering by dissolution and precipitation of halite cement
B. Oxidation of iron-bearing minerals followed by cementation with iron oxide
[CORRECT]
C. Physical weathering by abrasion and compaction of clay minerals
D. Hydrolysis of feldspar and recrystallization of calcite cement
Correct Answer: B
Rationale: The reddish coloration indicates oxidation of iron-bearing minerals during
weathering, producing iron oxides (hematite); when these iron oxides precipitate from
groundwater into pore spaces, they act as a cementing agent binding quartz grains
together. Halite cement would be soluble and not produce red coloration; abrasion and
2026/2027 – Complete Q&A with Detailed Rationales | 100%
Verified | Pass Guaranteed – A+ Graded
Section A: Sedimentary Rock Formation Processes
Q1: A student observes a granite boulder in the field that has developed cracks and is
slowly breaking apart into smaller fragments due to repeated freezing and thawing of
water in its fractures. Which weathering process is primarily responsible?
A. Chemical weathering through hydrolysis of feldspar minerals
B. Physical weathering through frost wedging [CORRECT]
C. Chemical weathering through oxidation of iron-bearing minerals
D. Biological weathering through root wedging by tree roots
Correct Answer: B
Rationale: Frost wedging is a physical (mechanical) weathering process where water
freezes in rock fractures, expanding by approximately 9% in volume and exerting
pressure that pries rock apart; repeated freeze-thaw cycles progressively break the rock
into smaller fragments. Hydrolysis and oxidation are chemical processes that alter
mineral composition; root wedging involves biological agents, not freeze-thaw cycles.
Q2: During a field trip, a geology student notices that a basalt outcrop has turned
reddish-brown in color and the feldspar crystals have been altered to clay minerals.
Which chemical weathering process best explains these observations?
A. Dissolution of calcite cement by acidic groundwater
B. Hydrolysis of silicate minerals with conversion to clay minerals and iron oxide
[CORRECT]
,C. Hydration of anhydrite to form gypsum
D. Carbonation of limestone to form calcium bicarbonate
Correct Answer: B
Rationale: Hydrolysis is a chemical weathering process where water reacts with silicate
minerals (such as feldspar in basalt), breaking chemical bonds and converting them to
clay minerals (kaolinite, smectite) while releasing iron that oxidizes to form
reddish-brown iron oxides (hematite, goethite). Dissolution affects carbonate and
evaporite minerals; hydration involves water incorporation into mineral structure;
carbonation specifically involves carbonic acid reacting with carbonate minerals.
Q3: A sedimentary rock sample shows sand grains that are tightly packed together with
calcite crystals filling the pore spaces between grains. Which lithification process is
primarily responsible for converting these loose sediments into solid rock?
A. Compaction alone reducing porosity through grain rearrangement
B. Cementation with precipitation of calcite minerals binding grains together [CORRECT]
C. Recrystallization of quartz grains into larger interlocking crystals
D. Melting and subsequent cooling of sedimentary material
Correct Answer: B
Rationale: Cementation is the lithification process where minerals precipitate from
groundwater into pore spaces between sediment grains, binding them together to form
solid rock; calcite is a common cementing mineral in sedimentary rocks. Compaction
reduces pore space but does not bind grains; recrystallization occurs during diagenesis
but is not the primary lithification mechanism; melting would produce igneous, not
sedimentary, rock.
, Q4: In a laboratory exercise, students are asked to identify the process that reduces the
porosity of buried sediments primarily through the weight of overlying materials forcing
grains closer together. Which term correctly identifies this process?
A. Cementation involving mineral precipitation from groundwater
B. Compaction from the weight of overlying sediments [CORRECT]
C. Lithification encompassing both compaction and cementation
D. Diagenesis including all post-depositional chemical changes
Correct Answer: B
Rationale: Compaction is the physical process where the weight of overlying sediments
compresses buried deposits, reducing pore space by forcing grains closer together and
expelling water; this is distinct from cementation, which involves mineral precipitation.
Lithification is the overall process of turning sediment into rock (compaction +
cementation); diagenesis includes all physical and chemical changes after deposition.
Q5: A geology student observes that a sandstone outcrop has iron oxide staining
(reddish coloration) and the individual quartz grains appear to be held together by a
reddish mineral material filling the spaces between grains. Which combination of
processes and materials best explains these features?
A. Chemical weathering by dissolution and precipitation of halite cement
B. Oxidation of iron-bearing minerals followed by cementation with iron oxide
[CORRECT]
C. Physical weathering by abrasion and compaction of clay minerals
D. Hydrolysis of feldspar and recrystallization of calcite cement
Correct Answer: B
Rationale: The reddish coloration indicates oxidation of iron-bearing minerals during
weathering, producing iron oxides (hematite); when these iron oxides precipitate from
groundwater into pore spaces, they act as a cementing agent binding quartz grains
together. Halite cement would be soluble and not produce red coloration; abrasion and
