Essentials of Oceanography 13th Edition Exam
Review Questions and Solutions 2026/2027 –
Complete Exam-Style Questions with Correct
Answers & Detailed Rationales | Verified &
Reliable
Question 1
Which process is primarily responsible for the formation of new
oceanic crust at a mid-ocean ridge?
A. Subduction
B. Transform faulting
C. Seafloor spreading
D. Continental collision
Correct Answer: C. Seafloor spreading
Seafloor spreading occurs as mantle material rises beneath a
divergent plate boundary, partially melts, and produces
magma. The magma cools to form new basaltic oceanic crust.
As additional crust forms, older crust is progressively moved
away from the ridge. Subduction later removes much of this
oceanic crust at convergent boundaries.
,Question 2
Which characteristic of seawater most directly increases its
density?
A. Increased temperature
B. Decreased salinity
C. Increased salinity
D. Increased dissolved oxygen
Correct Answer: C. Increased salinity
Higher salinity generally increases seawater density because
dissolved salts add mass without producing a proportional
increase in volume. Temperature has the opposite effect under
ordinary oceanic conditions: colder seawater is generally
denser. Density differences produced by temperature and
salinity are fundamental to thermohaline circulation.
Question 3
What is the principal source of energy that drives Earth's ocean
tides?
A. Solar radiation
B. Earth's internal heat
C. Gravitational interactions involving the Moon and Sun
D. Geothermal activity beneath the seafloor
,Correct Answer: C. Gravitational interactions involving the
Moon and Sun
Tides result primarily from gravitational interactions between
Earth, the Moon, and the Sun, with the Moon having the
stronger direct tidal influence because it is much closer to Earth.
Tidal forces produce periodic changes in sea-surface elevation.
The Sun modifies the lunar tidal pattern, producing phenomena
such as spring and neap tides.
Question 4
Which statement best describes a transform plate boundary in
an oceanic setting?
A. Two plates move toward each other and one is destroyed
B. Two plates move apart and new crust forms
C. Two plates slide horizontally past one another
D. A continental plate overrides a stationary oceanic plate
Correct Answer: C. Two plates slide horizontally past one
another
At transform boundaries, tectonic plates move laterally past
one another. Because crust is neither systematically created nor
destroyed along the transform boundary itself, these
boundaries differ from divergent and convergent boundaries.
, Transform faults commonly offset segments of mid-ocean
ridges.
Question 5
Which oceanic region receives sufficient sunlight for
photosynthetic organisms to thrive?
A. Aphotic zone
B. Hadal zone
C. Photic zone
D. Abyssal plain
Correct Answer: C. Photic zone
The photic zone is the portion of the ocean where enough
sunlight penetrates to support photosynthesis. Its depth varies
with water clarity and other environmental conditions. Most
marine primary production by phytoplankton occurs within this
illuminated region.
Question 6
What is the primary reason that sound generally travels faster
in seawater than in air?
Review Questions and Solutions 2026/2027 –
Complete Exam-Style Questions with Correct
Answers & Detailed Rationales | Verified &
Reliable
Question 1
Which process is primarily responsible for the formation of new
oceanic crust at a mid-ocean ridge?
A. Subduction
B. Transform faulting
C. Seafloor spreading
D. Continental collision
Correct Answer: C. Seafloor spreading
Seafloor spreading occurs as mantle material rises beneath a
divergent plate boundary, partially melts, and produces
magma. The magma cools to form new basaltic oceanic crust.
As additional crust forms, older crust is progressively moved
away from the ridge. Subduction later removes much of this
oceanic crust at convergent boundaries.
,Question 2
Which characteristic of seawater most directly increases its
density?
A. Increased temperature
B. Decreased salinity
C. Increased salinity
D. Increased dissolved oxygen
Correct Answer: C. Increased salinity
Higher salinity generally increases seawater density because
dissolved salts add mass without producing a proportional
increase in volume. Temperature has the opposite effect under
ordinary oceanic conditions: colder seawater is generally
denser. Density differences produced by temperature and
salinity are fundamental to thermohaline circulation.
Question 3
What is the principal source of energy that drives Earth's ocean
tides?
A. Solar radiation
B. Earth's internal heat
C. Gravitational interactions involving the Moon and Sun
D. Geothermal activity beneath the seafloor
,Correct Answer: C. Gravitational interactions involving the
Moon and Sun
Tides result primarily from gravitational interactions between
Earth, the Moon, and the Sun, with the Moon having the
stronger direct tidal influence because it is much closer to Earth.
Tidal forces produce periodic changes in sea-surface elevation.
The Sun modifies the lunar tidal pattern, producing phenomena
such as spring and neap tides.
Question 4
Which statement best describes a transform plate boundary in
an oceanic setting?
A. Two plates move toward each other and one is destroyed
B. Two plates move apart and new crust forms
C. Two plates slide horizontally past one another
D. A continental plate overrides a stationary oceanic plate
Correct Answer: C. Two plates slide horizontally past one
another
At transform boundaries, tectonic plates move laterally past
one another. Because crust is neither systematically created nor
destroyed along the transform boundary itself, these
boundaries differ from divergent and convergent boundaries.
, Transform faults commonly offset segments of mid-ocean
ridges.
Question 5
Which oceanic region receives sufficient sunlight for
photosynthetic organisms to thrive?
A. Aphotic zone
B. Hadal zone
C. Photic zone
D. Abyssal plain
Correct Answer: C. Photic zone
The photic zone is the portion of the ocean where enough
sunlight penetrates to support photosynthesis. Its depth varies
with water clarity and other environmental conditions. Most
marine primary production by phytoplankton occurs within this
illuminated region.
Question 6
What is the primary reason that sound generally travels faster
in seawater than in air?
