ESS 101 B EXAMINATION 3 ACTUAL EXAM 2026/2027 |
Complete Solution with Questions and Answers and Detailed
Rationales | Aligned with University Geology Curriculum &
Earth Science Standards | Pass Guaranteed - A+ Graded
Domain 1: Surface Water and Hydrology (12 Questions)
Q1
A stream gauge records the following data: cross-sectional area = 25 m², average
velocity = 0.8 m/s. What is the stream discharge, and which factor would most increase
it?
A. 20 m³/s; decreasing channel roughness [CORRECT]
B. 20 m³/s; increasing channel sinuosity
C. 31.25 m³/s; decreasing gradient
D. 31.25 m³/s; increasing water temperature
Correct Answer: A
Rationale: Discharge (Q) = cross-sectional area (A) × average velocity (V). Q = 25 m² ×
0.8 m/s = 20 m³/s. Discharge increases with: increased precipitation (water input),
increased gradient (steeper slope increases velocity), decreased channel roughness
(reduced friction increases velocity), or increased channel cross-section. Decreasing
roughness (smoother channel) most directly increases velocity and thus discharge.
Distractor Analysis: 31.25 m³/s (C, D) results from incorrect calculation (division instead
of multiplication). Increasing sinuosity (B) decreases gradient and velocity. Decreasing
gradient (C) reduces velocity. Water temperature (D) has minimal effect on discharge in
this context.
,Q2
A topographic map shows a drainage basin with dendritic stream patterns, gentle
gradients in the lower reaches, and steep headwaters. During a 50-year flood event,
which area is most susceptible to erosion and which to deposition?
A. Headwaters experience deposition; lower reaches experience erosion
B. Headwaters experience erosion; lower reaches experience deposition [CORRECT]
C. Entire basin experiences simultaneous erosion
D. Entire basin experiences simultaneous deposition
Correct Answer: B
Rationale: Stream competence (ability to transport sediment) depends on velocity,
which depends on gradient. Steep headwaters have high velocity and stream power
(proportional to velocity³), causing erosion of bed and banks. Gentle lower reaches have
reduced velocity, causing decreased competence and capacity, leading to deposition
(point bars, channel bars, floodplain aggradation). This is the fundamental longitudinal
profile of stream systems—erosion in steep upper reaches, transport in middle reaches,
deposition in gentle lower reaches.
Distractor Analysis: Reversed pattern (A) contradicts fluvial geomorphology principles.
Entire basin erosion (C) or deposition (D) ignores the energy gradient that drives fluvial
processes.
Q3
Which drainage pattern indicates specific bedrock structures? [Select all that apply]
A. Dendritic pattern = uniform, horizontal bedrock with no structural control [CORRECT]
B. Trellis pattern = alternating resistant and weak rock layers (folded or faulted)
[CORRECT]
,C. Radial pattern = volcanic cone or structural dome [CORRECT]
D. Rectangular pattern = jointed or fractured bedrock with right-angle intersections
[CORRECT]
E. Parallel pattern = areas with uniform slope but no structural control
F. Annular pattern = flat-lying sedimentary layers only
Correct Answer: A, B, C, D
Rationale:
● A: Dendritic (tree-like, irregular branching) develops on homogeneous material
without structural control.
● B: Trellis (main stream with right-angle tributaries) follows folded/faulted strata
where resistant ridges and weak valleys alternate.
● C: Radial (streams diverging from central point) indicates conical topography
(volcanoes, domes, buttes).
● D: Rectangular (right-angle bends) follows orthogonal joint systems or fault
patterns.
Why E and F are incorrect: Parallel pattern (E) indicates regional slope control on steep
slopes or parallel landforms, not "no structural control." Annular pattern (F) develops on
domes or structural basins with resistant outer rim and weak core, not flat-lying layers.
Q4
A floodplain shows natural levees 2-3 meters high adjacent to the channel, with
backswamp deposits of fine silt and clay beyond. Which process formed this
geomorphic assemblage?
A. Lateral erosion and point bar migration
B. Overbank flooding with coarse bedload deposition near channel, fines in distal areas
[CORRECT]
C. Tectonic subsidence and differential compaction
D. Glacial outwash deposition
Correct Answer: B
, Rationale: Natural levees form during overbank flooding when water spreads beyond
channel confines. Velocity drops immediately at the channel margin, depositing coarse
sand and gravel to build up levees. Finer silt and clay remain suspended longer, traveling
farther into the floodplain (backswamp) before settling. This creates the characteristic
grain-size segregation: coarse levees adjacent to channel, fine backswamp deposits
beyond. This is a universal feature of alluvial river systems.
Distractor Analysis: Lateral erosion (A) forms point bars and meander scrolls, not
vertical levee deposits. Tectonic subsidence (C) may create accommodation space but
doesn't explain the specific grain-size pattern. Glacial outwash (D) produces braided
stream deposits with different characteristics.
Q5
A stream has a drainage area of 500 km². During a storm, total precipitation was 50
mm, with 60% becoming runoff. What is the total runoff volume in cubic meters?
A. 15,000 m³
B. 150,000 m³
C. 15,000,000 m³ [CORRECT]
D. 150,000,000 m³
Correct Answer: C
Rationale: Calculation: (1) Convert area: 500 km² = 500 × (1,000 m)² = 500 × 1,000,000
m² = 500,000,000 m². (2) Convert precipitation: 50 mm = 0.050 m. (3) Total precipitation
volume: 500,000,000 m² × 0.050 m = 25,000,000 m³. (4) Runoff volume (60%):
25,000,000 × 0.60 = 15,000,000 m³.
Distractor Analysis: 15,000 m³ (A) uses km² as m² without conversion. 150,000 m³ (B)
has decimal errors. 150,000,000 m³ (D) uses 100% runoff or area conversion errors.
Complete Solution with Questions and Answers and Detailed
Rationales | Aligned with University Geology Curriculum &
Earth Science Standards | Pass Guaranteed - A+ Graded
Domain 1: Surface Water and Hydrology (12 Questions)
Q1
A stream gauge records the following data: cross-sectional area = 25 m², average
velocity = 0.8 m/s. What is the stream discharge, and which factor would most increase
it?
A. 20 m³/s; decreasing channel roughness [CORRECT]
B. 20 m³/s; increasing channel sinuosity
C. 31.25 m³/s; decreasing gradient
D. 31.25 m³/s; increasing water temperature
Correct Answer: A
Rationale: Discharge (Q) = cross-sectional area (A) × average velocity (V). Q = 25 m² ×
0.8 m/s = 20 m³/s. Discharge increases with: increased precipitation (water input),
increased gradient (steeper slope increases velocity), decreased channel roughness
(reduced friction increases velocity), or increased channel cross-section. Decreasing
roughness (smoother channel) most directly increases velocity and thus discharge.
Distractor Analysis: 31.25 m³/s (C, D) results from incorrect calculation (division instead
of multiplication). Increasing sinuosity (B) decreases gradient and velocity. Decreasing
gradient (C) reduces velocity. Water temperature (D) has minimal effect on discharge in
this context.
,Q2
A topographic map shows a drainage basin with dendritic stream patterns, gentle
gradients in the lower reaches, and steep headwaters. During a 50-year flood event,
which area is most susceptible to erosion and which to deposition?
A. Headwaters experience deposition; lower reaches experience erosion
B. Headwaters experience erosion; lower reaches experience deposition [CORRECT]
C. Entire basin experiences simultaneous erosion
D. Entire basin experiences simultaneous deposition
Correct Answer: B
Rationale: Stream competence (ability to transport sediment) depends on velocity,
which depends on gradient. Steep headwaters have high velocity and stream power
(proportional to velocity³), causing erosion of bed and banks. Gentle lower reaches have
reduced velocity, causing decreased competence and capacity, leading to deposition
(point bars, channel bars, floodplain aggradation). This is the fundamental longitudinal
profile of stream systems—erosion in steep upper reaches, transport in middle reaches,
deposition in gentle lower reaches.
Distractor Analysis: Reversed pattern (A) contradicts fluvial geomorphology principles.
Entire basin erosion (C) or deposition (D) ignores the energy gradient that drives fluvial
processes.
Q3
Which drainage pattern indicates specific bedrock structures? [Select all that apply]
A. Dendritic pattern = uniform, horizontal bedrock with no structural control [CORRECT]
B. Trellis pattern = alternating resistant and weak rock layers (folded or faulted)
[CORRECT]
,C. Radial pattern = volcanic cone or structural dome [CORRECT]
D. Rectangular pattern = jointed or fractured bedrock with right-angle intersections
[CORRECT]
E. Parallel pattern = areas with uniform slope but no structural control
F. Annular pattern = flat-lying sedimentary layers only
Correct Answer: A, B, C, D
Rationale:
● A: Dendritic (tree-like, irregular branching) develops on homogeneous material
without structural control.
● B: Trellis (main stream with right-angle tributaries) follows folded/faulted strata
where resistant ridges and weak valleys alternate.
● C: Radial (streams diverging from central point) indicates conical topography
(volcanoes, domes, buttes).
● D: Rectangular (right-angle bends) follows orthogonal joint systems or fault
patterns.
Why E and F are incorrect: Parallel pattern (E) indicates regional slope control on steep
slopes or parallel landforms, not "no structural control." Annular pattern (F) develops on
domes or structural basins with resistant outer rim and weak core, not flat-lying layers.
Q4
A floodplain shows natural levees 2-3 meters high adjacent to the channel, with
backswamp deposits of fine silt and clay beyond. Which process formed this
geomorphic assemblage?
A. Lateral erosion and point bar migration
B. Overbank flooding with coarse bedload deposition near channel, fines in distal areas
[CORRECT]
C. Tectonic subsidence and differential compaction
D. Glacial outwash deposition
Correct Answer: B
, Rationale: Natural levees form during overbank flooding when water spreads beyond
channel confines. Velocity drops immediately at the channel margin, depositing coarse
sand and gravel to build up levees. Finer silt and clay remain suspended longer, traveling
farther into the floodplain (backswamp) before settling. This creates the characteristic
grain-size segregation: coarse levees adjacent to channel, fine backswamp deposits
beyond. This is a universal feature of alluvial river systems.
Distractor Analysis: Lateral erosion (A) forms point bars and meander scrolls, not
vertical levee deposits. Tectonic subsidence (C) may create accommodation space but
doesn't explain the specific grain-size pattern. Glacial outwash (D) produces braided
stream deposits with different characteristics.
Q5
A stream has a drainage area of 500 km². During a storm, total precipitation was 50
mm, with 60% becoming runoff. What is the total runoff volume in cubic meters?
A. 15,000 m³
B. 150,000 m³
C. 15,000,000 m³ [CORRECT]
D. 150,000,000 m³
Correct Answer: C
Rationale: Calculation: (1) Convert area: 500 km² = 500 × (1,000 m)² = 500 × 1,000,000
m² = 500,000,000 m². (2) Convert precipitation: 50 mm = 0.050 m. (3) Total precipitation
volume: 500,000,000 m² × 0.050 m = 25,000,000 m³. (4) Runoff volume (60%):
25,000,000 × 0.60 = 15,000,000 m³.
Distractor Analysis: 15,000 m³ (A) uses km² as m² without conversion. 150,000 m³ (B)
has decimal errors. 150,000,000 m³ (D) uses 100% runoff or area conversion errors.
