ESS 101 B LAB 5 QUIZ 2026/2027 | Sedimentary Rocks |
Introduction to Geology | 100% Correct Solved |
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Section 1: Sedimentary Rock Classification & Textures
(Questions 1-12)
Q1. According to the Udden-Wentworth grain size scale, which particle size range
correctly defines sand?
A. <0.004 mm
B. 0.004–0.0625 mm
C. 0.0625–2 mm
D. >2 mm
Rationale: The Udden-Wentworth scale defines sand as particles between 0.0625
mm and 2 mm. Clay is <0.004 mm (Option A), silt is 0.004–0.0625 mm (Option B),
and gravel is >2 mm (Option D). These boundaries are fundamental for classifying
clastic sedimentary rocks.
Correct Answer: C
Q2. A sedimentary rock sample contains clasts ranging from 0.5 mm to 64 mm with
no dominant size fraction. Which term best describes the sorting of this sediment?
A. Well-sorted
B. Moderately well-sorted
C. Poorly sorted
D. Very well-sorted
Rationale: Poorly sorted sediments contain a wide range of grain sizes with no
dominant fraction, indicating deposition from high-energy, variable flows such as
,debris flows or glacial till. Well-sorted (Option A) and very well-sorted (Option D)
sediments have uniform grain sizes. Moderately well-sorted (Option B) shows a
narrower range than described.
Correct Answer: C
Q3. A sandstone sample from an ancient beach deposit shows grains that are nearly
spherical with all sharp edges and corners removed. Which term best describes the
roundness of these grains?
A. Angular
B. Sub-rounded
C. Rounded
D. Well-rounded
Rationale: Well-rounded grains have all edges and corners removed and approach
spherical shape, indicating prolonged transport in high-energy environments like
beaches or rivers. Angular grains (Option A) retain sharp edges. Sub-rounded
(Option B) shows partial edge removal. Rounded (Option C) has most edges removed
but is less spherical than well-rounded.
Correct Answer: D
Q4. Which combination of textural characteristics indicates the HIGHEST textural
maturity in a clastic sedimentary rock?
A. Fine-grained, poorly sorted, angular grains with abundant matrix
B. Medium-grained, well-sorted, well-rounded grains with minimal matrix
C. Coarse-grained, poorly sorted, sub-angular grains with clay matrix
D. Very fine-grained, moderately sorted, sub-rounded grains with silt matrix
Rationale: Textural maturity increases with better sorting, increased roundness, and
reduced matrix (fine-grained material between larger grains). Well-sorted, well-
rounded grains with minimal matrix represent maximum transport distance and
, reworking. Options A, C, and D all show lower maturity due to poor sorting, angular
grains, or abundant matrix.
Correct Answer: B
Q5. In clastic sedimentary rocks, compositional maturity refers to which
characteristic?
A. The uniformity of grain sizes within the rock
B. The proportion of stable minerals (quartz) versus unstable minerals (feldspars,
lithic fragments) in the framework grains
C. The degree of cementation holding the grains together
D. The presence of fossils within the rock
Rationale: Compositional maturity measures the stability of framework minerals.
Quartz-rich rocks are compositionally mature because quartz resists weathering and
transport. Feldspar- or lithic-rich rocks are immature, indicating minimal transport
from source. Option A describes textural maturity. Option C describes diagenesis.
Option D describes biogenic content.
Correct Answer: B
Q6. A river transports quartz, feldspar, and lithic fragments from a granite source.
After 500 km of transport, which mineral would MOST likely dominate the deposited
sediment?
A. Feldspar, because it is the most abundant mineral in granite
B. Lithic fragments, because they are the most durable
C. Quartz, because it is the most chemically and physically stable during weathering
and transport
D. All three minerals would be present in equal proportions
Rationale: Quartz is the most stable common silicate mineral under surface
conditions. Feldspar weathers to clay, and lithic fragments break down mechanically
Introduction to Geology | 100% Correct Solved |
University of Washington | Pass Guaranteed - A+ Graded
Section 1: Sedimentary Rock Classification & Textures
(Questions 1-12)
Q1. According to the Udden-Wentworth grain size scale, which particle size range
correctly defines sand?
A. <0.004 mm
B. 0.004–0.0625 mm
C. 0.0625–2 mm
D. >2 mm
Rationale: The Udden-Wentworth scale defines sand as particles between 0.0625
mm and 2 mm. Clay is <0.004 mm (Option A), silt is 0.004–0.0625 mm (Option B),
and gravel is >2 mm (Option D). These boundaries are fundamental for classifying
clastic sedimentary rocks.
Correct Answer: C
Q2. A sedimentary rock sample contains clasts ranging from 0.5 mm to 64 mm with
no dominant size fraction. Which term best describes the sorting of this sediment?
A. Well-sorted
B. Moderately well-sorted
C. Poorly sorted
D. Very well-sorted
Rationale: Poorly sorted sediments contain a wide range of grain sizes with no
dominant fraction, indicating deposition from high-energy, variable flows such as
,debris flows or glacial till. Well-sorted (Option A) and very well-sorted (Option D)
sediments have uniform grain sizes. Moderately well-sorted (Option B) shows a
narrower range than described.
Correct Answer: C
Q3. A sandstone sample from an ancient beach deposit shows grains that are nearly
spherical with all sharp edges and corners removed. Which term best describes the
roundness of these grains?
A. Angular
B. Sub-rounded
C. Rounded
D. Well-rounded
Rationale: Well-rounded grains have all edges and corners removed and approach
spherical shape, indicating prolonged transport in high-energy environments like
beaches or rivers. Angular grains (Option A) retain sharp edges. Sub-rounded
(Option B) shows partial edge removal. Rounded (Option C) has most edges removed
but is less spherical than well-rounded.
Correct Answer: D
Q4. Which combination of textural characteristics indicates the HIGHEST textural
maturity in a clastic sedimentary rock?
A. Fine-grained, poorly sorted, angular grains with abundant matrix
B. Medium-grained, well-sorted, well-rounded grains with minimal matrix
C. Coarse-grained, poorly sorted, sub-angular grains with clay matrix
D. Very fine-grained, moderately sorted, sub-rounded grains with silt matrix
Rationale: Textural maturity increases with better sorting, increased roundness, and
reduced matrix (fine-grained material between larger grains). Well-sorted, well-
rounded grains with minimal matrix represent maximum transport distance and
, reworking. Options A, C, and D all show lower maturity due to poor sorting, angular
grains, or abundant matrix.
Correct Answer: B
Q5. In clastic sedimentary rocks, compositional maturity refers to which
characteristic?
A. The uniformity of grain sizes within the rock
B. The proportion of stable minerals (quartz) versus unstable minerals (feldspars,
lithic fragments) in the framework grains
C. The degree of cementation holding the grains together
D. The presence of fossils within the rock
Rationale: Compositional maturity measures the stability of framework minerals.
Quartz-rich rocks are compositionally mature because quartz resists weathering and
transport. Feldspar- or lithic-rich rocks are immature, indicating minimal transport
from source. Option A describes textural maturity. Option C describes diagenesis.
Option D describes biogenic content.
Correct Answer: B
Q6. A river transports quartz, feldspar, and lithic fragments from a granite source.
After 500 km of transport, which mineral would MOST likely dominate the deposited
sediment?
A. Feldspar, because it is the most abundant mineral in granite
B. Lithic fragments, because they are the most durable
C. Quartz, because it is the most chemically and physically stable during weathering
and transport
D. All three minerals would be present in equal proportions
Rationale: Quartz is the most stable common silicate mineral under surface
conditions. Feldspar weathers to clay, and lithic fragments break down mechanically
