Essentials of Oceanography 13th Edition Exam
Questions and Answers 2026/2027 – Complete
Exam-Style Questions with Correct Answers &
Detailed Rationales | Verified & Reliable
1.
Which characteristic of seawater most directly explains why
seawater is generally denser than freshwater at the same
temperature?
A. Its greater concentration of dissolved oxygen
B. Its higher salinity
C. Its greater wave energy
D. Its higher atmospheric pressure
Correct answer: B. Its higher salinity
Salinity increases the mass of seawater without producing a
proportional increase in volume, thereby increasing density.
Temperature also strongly affects seawater density, but under
otherwise comparable conditions, dissolved salts make
seawater denser than freshwater.
,2.
Which process is primarily responsible for the formation of
most oceanic crust at mid-ocean ridges?
A. Continental collision
B. Subduction of oceanic lithosphere
C. Seafloor spreading
D. Transform faulting
Correct answer: C. Seafloor spreading
At mid-ocean ridges, hot mantle material rises, partially melts,
and produces basaltic magma. As magma cools, it forms new
oceanic crust. Continued addition of crust pushes older seafloor
away from the ridge, a process known as seafloor spreading.
3.
A deep-sea sediment sample contains abundant microscopic
shells composed primarily of calcium carbonate. Which factor
would most strongly determine whether those shells are
preserved after they sink below the surface ocean?
A. Surface wave height
B. Carbonate saturation and depth
C. Solar radiation intensity
D. Tidal range
,Correct answer: B. Carbonate saturation and depth
Calcium carbonate dissolves more readily in cold, high-pressure,
carbon dioxide-rich seawater. The depth at which carbonate
dissolution becomes especially significant is related to the
carbonate compensation depth. Below this depth, carbonate
accumulation is greatly reduced because dissolution exceeds
preservation.
4.
Which observation provides the strongest evidence for the
theory of plate tectonics?
A. Ocean waves generally travel toward shore
B. Magnetic striping on the seafloor is symmetrical about mid-
ocean ridges
C. Tides occur approximately twice daily in many locations
D. Surface seawater contains dissolved gases
Correct answer: B. Magnetic striping on the seafloor is
symmetrical about mid-ocean ridges
Basalt formed at a mid-ocean ridge records the direction of
Earth's magnetic field as it cools. Because Earth's magnetic field
has reversed repeatedly, alternating magnetic patterns occur in
parallel bands on both sides of ridges. Their symmetry strongly
supports seafloor spreading and plate tectonics.
, 5.
What primarily causes the difference between spring tides and
neap tides?
A. Changes in Earth's rotation rate
B. Changes in the distance between Earth and the Sun only
C. The relative alignment of the Sun, Earth, and Moon
D. Seasonal changes in ocean temperature
Correct answer: C. The relative alignment of the Sun, Earth,
and Moon
Spring tides occur near new and full moons when the
gravitational effects of the Sun and Moon reinforce one
another, producing a larger tidal range. Neap tides occur near
the first- and third-quarter Moon, when the Sun and Moon act
at roughly right angles relative to Earth and their tidal effects
partially counteract each other.
6.
Which property of seawater generally increases when
temperature decreases, assuming salinity remains
approximately constant?
Questions and Answers 2026/2027 – Complete
Exam-Style Questions with Correct Answers &
Detailed Rationales | Verified & Reliable
1.
Which characteristic of seawater most directly explains why
seawater is generally denser than freshwater at the same
temperature?
A. Its greater concentration of dissolved oxygen
B. Its higher salinity
C. Its greater wave energy
D. Its higher atmospheric pressure
Correct answer: B. Its higher salinity
Salinity increases the mass of seawater without producing a
proportional increase in volume, thereby increasing density.
Temperature also strongly affects seawater density, but under
otherwise comparable conditions, dissolved salts make
seawater denser than freshwater.
,2.
Which process is primarily responsible for the formation of
most oceanic crust at mid-ocean ridges?
A. Continental collision
B. Subduction of oceanic lithosphere
C. Seafloor spreading
D. Transform faulting
Correct answer: C. Seafloor spreading
At mid-ocean ridges, hot mantle material rises, partially melts,
and produces basaltic magma. As magma cools, it forms new
oceanic crust. Continued addition of crust pushes older seafloor
away from the ridge, a process known as seafloor spreading.
3.
A deep-sea sediment sample contains abundant microscopic
shells composed primarily of calcium carbonate. Which factor
would most strongly determine whether those shells are
preserved after they sink below the surface ocean?
A. Surface wave height
B. Carbonate saturation and depth
C. Solar radiation intensity
D. Tidal range
,Correct answer: B. Carbonate saturation and depth
Calcium carbonate dissolves more readily in cold, high-pressure,
carbon dioxide-rich seawater. The depth at which carbonate
dissolution becomes especially significant is related to the
carbonate compensation depth. Below this depth, carbonate
accumulation is greatly reduced because dissolution exceeds
preservation.
4.
Which observation provides the strongest evidence for the
theory of plate tectonics?
A. Ocean waves generally travel toward shore
B. Magnetic striping on the seafloor is symmetrical about mid-
ocean ridges
C. Tides occur approximately twice daily in many locations
D. Surface seawater contains dissolved gases
Correct answer: B. Magnetic striping on the seafloor is
symmetrical about mid-ocean ridges
Basalt formed at a mid-ocean ridge records the direction of
Earth's magnetic field as it cools. Because Earth's magnetic field
has reversed repeatedly, alternating magnetic patterns occur in
parallel bands on both sides of ridges. Their symmetry strongly
supports seafloor spreading and plate tectonics.
, 5.
What primarily causes the difference between spring tides and
neap tides?
A. Changes in Earth's rotation rate
B. Changes in the distance between Earth and the Sun only
C. The relative alignment of the Sun, Earth, and Moon
D. Seasonal changes in ocean temperature
Correct answer: C. The relative alignment of the Sun, Earth,
and Moon
Spring tides occur near new and full moons when the
gravitational effects of the Sun and Moon reinforce one
another, producing a larger tidal range. Neap tides occur near
the first- and third-quarter Moon, when the Sun and Moon act
at roughly right angles relative to Earth and their tidal effects
partially counteract each other.
6.
Which property of seawater generally increases when
temperature decreases, assuming salinity remains
approximately constant?
