01 What is the main limitation of single-beam depth sounding in ocean-floor mapping?0 reads0 helpful★ – (0)
A It gives depth only along the line below the ship track B It does not use sound in water C It always tells rock age of the sea floor D It collects samples directly by satellite
Answer and explanation Correct answer: A . It gives depth only along the line below the ship track
Explanation: Single-beam sounding gives data along a limited line, so areas between tracks may be missed. Exam tip: connect survey coverage with method limitation.
02 In multibeam bathymetry, which explanation is most correct when swath width increases?0 reads0 helpful★ – (0)
A Depth measurement completely stops B A larger sea-floor area can be mapped in less time C Only atmospheric clouds are measured D Age of oceanic crust automatically decreases
Answer and explanation Correct answer: B . A larger sea-floor area can be mapped in less time
Explanation: A wide swath records more floor area in one pass. Exam tip: treat multibeam as a wide-coverage technique.
03 What is the most likely error if a sound-speed profile is not taken in sea-floor mapping?0 reads0 helpful★ – (0)
A Fish number will appear low B Coastline will become a political boundary C Calculation of depth and floor position may become wrong D Sediments will disappear immediately
Answer and explanation Correct answer: C . Calculation of depth and floor position may become wrong
Explanation: Temperature, salinity and pressure change sound speed. Exam tip: remember sound-speed correction for accurate sonar measurement.
04 If ridge segments appear offset and joined by transverse lines on a bathymetric map, what is the most suitable conclusion?0 reads0 helpful★ – (0)
A It indicates a river delta B It indicates a coral lagoon C It is a passive coastal plain D It may be linked with transform faults and fracture zones
Answer and explanation Correct answer: D . It may be linked with transform faults and fracture zones
Explanation: Offset ridge segments can indicate a transform fault system. Exam tip: study ridges, faults and plate motion together.
05 What does nearly equal age on both sides at equal distance from a ridge mean in a sea-floor age map?0 reads0 helpful★ – (0)
A Sea-floor spreading has occurred approximately symmetrically B The sea floor is static and unchanged C The shelf is the deepest part D New crust is forming in trenches
Answer and explanation Correct answer: A . Sea-floor spreading has occurred approximately symmetrically
Explanation: When new crust spreads on both sides of a ridge, age pattern can be symmetrical. Exam tip: treat age and distance as spreading evidence.
06 Which conclusion becomes strongest by reading magnetic stripes and rock age together?0 reads0 helpful★ – (0)
A Ocean salinity is zero B New crust forms at ridges and spreads to both sides C Ocean trenches are formed by river erosion D Mid-oceanic ridges are only sedimentary plains
Answer and explanation Correct answer: B . New crust forms at ridges and spreads to both sides
Explanation: Magnetic bands and age sequence are complementary evidence of sea-floor spreading. Exam tip: combine two evidences for the conclusion.
07 Why is it necessary to check satellite-altimetry ocean maps with ship-based maps?0 reads0 helpful★ – (0)
A Satellite only counts clouds B Ship-based measurement is always impossible C Satellite estimation is indirect, so direct depth verification is needed D Satellite brings samples from the sea floor
Answer and explanation Correct answer: C . Satellite estimation is indirect, so direct depth verification is needed
Explanation: Satellite estimates the floor from gravity and sea-surface signals. Exam tip: remember the difference between direct and indirect data.
08 In which situation can the gravity signal of a seamount create a slight bulge on the sea surface?0 reads0 helpful★ – (0)
A When the seamount has more mass than surrounding areas B When coastal wind completely stops C When a river mouth dries up D When tide occurs only on land
Answer and explanation Correct answer: A . When the seamount has more mass than surrounding areas
Explanation: Greater mass can increase local gravity and produce a tiny sea-surface bulge. Exam tip: understand this as the basis of satellite altimetry.
09 If depth decreases inward within closed isobaths on an ocean-floor map, what does it indicate?0 reads0 helpful★ – (0)
A Oceanic trench B Raised submarine feature C River flood plain D Zero sea level
Answer and explanation Correct answer: B . Raised submarine feature
Explanation: Lower depth inward indicates a sea-floor high or seamount. Exam tip: read the direction of depth change in closed lines.
10 If depth increases inward within closed isobaths, which conclusion is suitable?0 reads0 helpful★ – (0)
A There is a depression or trench-like part on the floor B A summit is raised on the floor C It is a coastal population centre D It is an atmospheric pressure zone
Answer and explanation Correct answer: A . There is a depression or trench-like part on the floor
Explanation: Greater inward depth shows a closed depression. Exam tip: read isobaths like contours but with depth logic.
11 Why is mapping a submarine fan important in the study of continental rise?0 reads0 helpful★ – (0)
A It changes sea-surface colour B It can show depositional pathways of sediments from the slope C It turns a mid-ridge into a river D It turns volcanoes into clouds
Answer and explanation Correct answer: B . It can show depositional pathways of sediments from the slope
Explanation: Submarine fans can indicate deposition by turbidity flows. Exam tip: understand the rise as a depositional zone.
12 Which feature on the ocean floor can turbidity currents help form?0 reads0 helpful★ – (0)
A Ring wall of a coral island B Atmospheric cyclone C Submarine canyon and depositional fan D Coastal political boundary
Answer and explanation Correct answer: C . Submarine canyon and depositional fan
Explanation: Turbidity currents can cut slopes and deposit sediments downslope. Exam tip: connect flow, canyon and fan in sequence.
13 What does the association of long linear trenches with earthquake epicentres indicate?0 reads0 helpful★ – (0)
A Floods of land rivers B Coastal tourism area C Only marine fishing zone D Active convergent plate boundary
Answer and explanation Correct answer: D . Active convergent plate boundary
Explanation: The association of trenches and earthquakes can indicate a subduction zone. Exam tip: read landforms and earthquake distribution together.
14 What do very closely spaced isobaths on the continental slope prove in ocean-floor mapping?0 reads0 helpful★ – (0)
A Rapid change in depth over a short horizontal distance B Very gradual change in depth over a short horizontal distance C Nearly flat ocean floor D Broad shallow continental shelf
Answer and explanation Correct answer: A . Rapid change in depth over a short horizontal distance
Explanation: Isobaths join points of equal depth. When they are very close together, depth changes rapidly over a short horizontal distance, indicating a steep slope. This is typical of a continental slope. Widely spaced isobaths, in contrast, indicate a gentle slope or a nearly flat floor. Exam tip: the smaller the spacing between isobaths, the steeper the slope.
15 Why is identification of the shelf break useful on a continental shelf margin?0 reads0 helpful★ – (0)
A It marks the sharp transition from shelf to continental slope B It separates the ocean from the atmosphere C It turns volcanoes into glaciers D It makes sea water permanent
Answer and explanation Correct answer: A . It marks the sharp transition from shelf to continental slope
Explanation: Shelf break is an important bend in the depth profile. Exam tip: treat it as an indicator of shelf boundary.
16 Which statement is more correct in bathymetric comparison of active and passive continental margins?0 reads0 helpful★ – (0)
A Passive margins may commonly have wider shelves and more sediments B Trenches never occur at active margins C Slope is always identical at both margins D Passive margins are only mid-ocean ridges
Answer and explanation Correct answer: A . Passive margins may commonly have wider shelves and more sediments
Explanation: Passive margins can be sediment-rich and gentler, while active margins are tectonically sharper. Exam tip: distinguish their profiles.
17 What historical process can a flat-topped submerged volcanic mountain show?0 reads0 helpful★ – (0)
A Only river deposition B Earlier wave erosion and later subsidence C Atmospheric pressure reversal D Terrestrial glacial deposition
Answer and explanation Correct answer: B . Earlier wave erosion and later subsidence
Explanation: The flat top of a guyot may be linked with wave erosion at an older sea level. Exam tip: identify guyot by its flat top.
18 What can be the most scientific meaning of an age-progressive seamount chain?0 reads0 helpful★ – (0)
A Permanent absence of tide B River branches in the sea C Passage of a moving plate over a fixed hotspot D Complete flatness of the shelf
Answer and explanation Correct answer: C . Passage of a moving plate over a fixed hotspot
Explanation: Plate motion over a hotspot can form seamounts of different ages. Exam tip: treat age progression as evidence of plate motion.
19 Which clue is decisive in distinguishing an oceanic plateau from a normal abyssal plain?0 reads0 helpful★ – (0)
A It occurs only on the coast B It forms only at river mouths C It floats on the sea surface D It is a broad and relatively elevated sea-floor area
Answer and explanation Correct answer: D . It is a broad and relatively elevated sea-floor area
Explanation: An oceanic plateau is higher and broader than an abyssal plain. Exam tip: look for both elevation and extent.
20 What can sediment-layer thickness in a seismic reflection profile indicate about sea-floor development?0 reads0 helpful★ – (0)
A Sedimentation history and relative age of crust B Taste of sea water C Coastal market price D Daily movement of clouds
Answer and explanation Correct answer: A . Sedimentation history and relative age of crust
Explanation: More sediment may indicate older or more deposited areas. Exam tip: connect layer thickness with time and deposition.
21 Dominance of basalt in oceanic crust samples supports which interpretation in ocean-floor mapping?0 reads0 helpful★ – (0)
A Oceanic crust is mainly made of volcanic basaltic material B Oceanic crust is only sandstone C There are no rocks on the sea floor D Continental and oceanic crust are completely identical
Answer and explanation Correct answer: A . Oceanic crust is mainly made of volcanic basaltic material
Explanation: Basaltic composition is a common identity of oceanic crust. Exam tip: remember the difference between oceanic and continental crust.
22 The occurrence of pillow lava indicates which environment on the ocean floor?0 reads0 helpful★ – (0)
A River flood plain B Submarine basaltic volcanic eruption C Desert wind deposit D Glacial moraine
Answer and explanation Correct answer: B . Submarine basaltic volcanic eruption
Explanation: Pillow lava forms by rapid cooling of lava under water. Exam tip: connect it with oceanic volcanic activity.
23 Why is mapping hydrothermal vents important in the study of mid-oceanic ridges?0 reads0 helpful★ – (0)
A They indicate active heat, fluid flow and mineral deposits B They show coastal sand colour C They make water fresh D They show only seabird nests
Answer and explanation Correct answer: A . They indicate active heat, fluid flow and mineral deposits
Explanation: Hydrothermal vents may be linked with active ridge systems. Exam tip: connect them with heat, minerals and new crust.
24 Why is it necessary to read calcareous ooze distribution with depth?0 reads0 helpful★ – (0)
A Because depth can affect dissolution and preservation of shells B Because it only stops tides C Because it is equally thick everywhere D Because it makes the sea floor invisible
Answer and explanation Correct answer: A . Because depth can affect dissolution and preservation of shells
Explanation: Calcareous material can be affected by depth and chemical conditions. Exam tip: connect biogenic sediment with environmental conditions.
25 Where is greater thickness of terrigenous sediments more likely in marine areas?0 reads0 helpful★ – (0)
A Near river mouths and continental margins B Only on the axis of mid-ocean ridges C Always equally at the bottom of deep trenches D In the air above sea surface
Answer and explanation Correct answer: A . Near river mouths and continental margins
Explanation: Terrigenous sediments come from land sources, so they may be greater near margins. Exam tip: remember terrigenous means land-derived.