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SubjectsGeography
महासागर तल का मानचित्रण
In this Class 11 Geography topic from “Distribution of Oceans and Continents,” students learn how the ocean floor is mapped and interpreted. They explore major features such as continental shelves, slopes, deep-sea plains, mid-ocean ridges, trenches and seamounts, and understand how soundings, sonar and bathymetric maps reveal underwater relief. The topic also helps connect ocean-floor patterns with plate boundaries, seafloor spreading and the changing distribution of continents and oceans.
Correct answer: A. Depth and ocean floor relief
Explanation: A bathymetric map shows depth and shape of the sea floor. Exam tip: treat it as a topographic map of the ocean.
Correct answer: B. The sea floor is deeper
Explanation: Longer time means the sound travelled a greater distance. Exam tip: remember the direct relation between time and depth.
Correct answer: C. The slope is steep
Explanation: Closely spaced isobaths show a rapid depth change over a short distance. Exam tip: link close lines with steep slope.
Correct answer: D. It maps a wide strip of relief at once
Explanation: Multibeam sonar uses many sound beams to collect data over a wider area. Exam tip: treat it as a detailed mapping technique.
Correct answer: A. A shallow submerged continental part near the coast
Explanation: The continental shelf is a shallow resource-rich zone near the coast. Exam tip: connect it with coast and resources.
Correct answer: B. Because it shows the change from shelf to deep ocean basin
Explanation: The continental slope is the transition from shallow shelf to deep basin. Exam tip: remember slope after shelf in the sequence.
Correct answer: C. Broad flat area in deep ocean
Explanation: Abyssal plains are broad low-slope parts of the deep ocean. Exam tip: understand them as flat plains of the deep sea.
Correct answer: D. Because they are linked with plate spreading zones
Explanation: Mid-oceanic ridges are often linked with sea-floor spreading. Exam tip: connect them with plate boundaries.
Correct answer: A. Subduction
Explanation: Oceanic trenches are generally linked with subduction zones. Exam tip: remember trenches with convergent plate boundaries.
Correct answer: B. It estimates floor relief from small sea-surface height variations
Explanation: Small variations in sea surface can indicate large features below. Exam tip: understand it as an indirect mapping method.
Correct answer: C. A deep cut valley on the sea floor
Explanation: A submarine canyon is a deep valley-like cut on the sea floor. Exam tip: understand it as a submerged valley.
Correct answer: A. A guyot has a flat top, whereas a seamount generally has a conical or irregular summit
Explanation: A guyot is essentially a submerged volcanic seamount whose summit has been flattened by wave action and erosion. An ordinary seamount commonly has a conical, rounded, or irregular summit. Option D is incorrect because a seamount does not reach sea level; if it rises above the surface, it becomes an island. Exam tip: the key identifying feature of a guyot is its flat top.
Correct answer: A. It helps understand relief in three-dimensional form
Explanation: Digital models visually show depth height and slope of the sea floor. Exam tip: treat models as tools of analysis.
Correct answer: B. It gave only point depth and was slow
Explanation: The rope-and-weight method was slow and limited to point measurements. Exam tip: see sonar as progress over it.
Correct answer: C. To show depth changes along a selected line
Explanation: A profile line helps create a cut-view of the ocean floor. Exam tip: connect it with cross section.
Correct answer: D. Geological history and nature of deposition
Explanation: Sediment thickness gives clues about deposition and past environment. Exam tip: treat sediments as records of the sea floor.
Correct answer: A. To reduce errors and improve accuracy
Explanation: Repeated checking detects wrong readings and instrument errors. Exam tip: link quality control with accurate maps.
Correct answer: B. Because the legend changes weather
Explanation: A map legend helps interpret colours and symbols. Exam tip: always check the legend in map questions.
Correct answer: C. Continental slope or trench
Explanation: A sudden depth increase may indicate a steep slope or trench. Exam tip: identify features from depth change.
Correct answer: B. Ship method directly measures depth while satellite gives indirect estimates
Explanation: Ships directly measure with sonar while satellites estimate from surface signals. Exam tip: separate direct and indirect methods.
Correct answer: A. Because safe routes can be selected
Explanation: Knowledge of trenches slopes and obstacles reduces cable risk. Exam tip: remember practical uses of mapping.
Correct answer: B. Depth affects light pressure and living conditions
Explanation: Changing depth affects light pressure and thermal conditions. Exam tip: connect depth with habitat zones.
Correct answer: C. Coastal depth and sea-floor slope
Explanation: Coastal depth and slope can affect wave height and speed. Exam tip: remember the role of bathymetry in disaster studies.
Correct answer: D. By a gentle sedimented zone below the continental slope
Explanation: Continental rise forms due to sediments below the continental slope. Exam tip: remember the sequence shelf slope rise.
Correct answer: A. Relief and geological structure
Explanation: Relief and geological structure help identify mineral zones. Exam tip: connect resource exploration with sea-floor mapping.
