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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: B. Bathymetric map
Explanation: A bathymetric map shows the depth and features of the ocean floor. Exam tip: connect it with submarine relief maps.
Correct answer: A. Sound wave
Explanation: Sonar sends sound waves and uses their echo to find depth. Exam tip: remember sonar with sound.
Correct answer: C. Isobath
Explanation: An isobath joins points of equal depth in a sea or ocean, so option C is correct. An isobar joins places of equal atmospheric pressure, whereas an isotherm represents equal temperature. Exam tip: associate “bath” in isobath with water depth.
Correct answer: B. Shallow sea area near the coast
Explanation: A continental shelf is a shallow area near the coast. Exam tip: connect it with resource-rich zones.
Correct answer: A. Continental shelf
Explanation: The continental slope begins after the shelf and deepens quickly. Exam tip: remember the order of shelf and slope.
Correct answer: B. Abyssal plain
Explanation: Abyssal plains are wide flat parts of the deep ocean. Exam tip: treat them as deep ocean plains.
Correct answer: C. Oceanic trench
Explanation: Oceanic trenches are long narrow and very deep parts. Exam tip: connect trenches with the deepest areas.
Correct answer: A. Mid-oceanic ridge
Explanation: A mid-oceanic ridge is a long raised chain on the ocean floor. Exam tip: understand it as an underwater mountain chain.
Correct answer: B. Seamount
Explanation: A seamount rises from the sea floor but often remains below the surface. Exam tip: remember it as a submerged mountain.
Correct answer: C. Guyot
Explanation: A guyot is a seamount whose summit has been eroded flat, usually by wave action when it was near sea level. Therefore, guyot is the correct answer. A ridge is a long elevated feature on the ocean floor, while a continental shelf is the shallow submerged edge of a continent. Exam tip: a flat-topped seamount is called a guyot.
Correct answer: A. Submerged deep valley
Explanation: The direct answer is A, a submerged deep valley. A submarine canyon is a long, narrow, steep-sided depression cut into the sea floor. It resembles a valley on land, but it is underwater. Such canyons may continue from the edge of a continent down the continental slope and can carry sediment into deeper parts of the ocean. Option A is correct because “submerged deep valley” describes its shape and position exactly. Option B, a desert dune, is a wind-built mound of sand on land and has the opposite form. Option C, a Himalayan peak, is a high mountain summit, not a deep channel in the ocean floor. Option D, a plain field, is broad and nearly level, whereas a canyon is narrow and deeply incised. The key is to separate “submarine” meaning under the sea from “canyon” meaning a deep valley. Memory cue: submarine canyon = underwater valley.
Correct answer: B. Recording water depth and bottom information
Explanation: Hydrographic survey deals with depths and bottoms of water bodies. Exam tip: connect it with navigation charts.
Correct answer: A. Because it shows marine depth and obstacles
Explanation: Knowing depths and obstacles helps ships choose safe routes. Exam tip: link mapping with ship safety.
Correct answer: B. It can measure a wide sea-floor area at once
Explanation: Multibeam sonar maps a wide floor area using many sound beams. Exam tip: connect it with detailed surveys.
Correct answer: A. It gives clues from small sea-surface variations
Explanation: Small sea-surface variations can indicate large features below. Exam tip: treat satellites as a supporting technique.
Correct answer: B. Between slope and abyssal plain
Explanation: The continental rise forms below the slope from sediments and meets the deep plain. Exam tip: treat it as a transition zone.
Correct answer: A. Deposition of sediments
Explanation: Sediments deposited in the deep sea cover uneven parts. Exam tip: link sediments with flatness.
Correct answer: B. Steep slope
Explanation: Closely spaced lines show a rapid change in depth. Exam tip: remember it like the rule of contour lines.
Correct answer: B. Gentle slope
Explanation: Isobaths join points of equal depth. When they are widely spaced, depth changes only slightly over a horizontal distance, indicating a gentle slope of the sea floor. A steep slope produces a rapid change in depth, so its isobaths are close together. Exam tip: closer contour or isobath lines indicate a steeper slope.
Correct answer: B. Mid-oceanic ridge
Explanation: New ocean floor formation is linked with mid-oceanic ridges. Exam tip: remember ridge and spreading together.
Correct answer: B. Convergent boundary
Explanation: Trenches often form where one plate sinks beneath another. Exam tip: connect trenches with convergence.
Correct answer: A. By giving information about marine structure and depth
Explanation: Knowing marine structure helps identify possible resource areas. Exam tip: connect resource exploration with mapping.
Correct answer: A. Because route depth and slope must be known
Explanation: The bottom structure and risks must be known for a safe cable route. Exam tip: connect it with modern communication.
Correct answer: A. Ocean floor features and trenches
Explanation: Trenches and marine structures help understand seismic zones. Exam tip: remember the link between undersea earthquakes and tsunamis.
Correct answer: A. Identification of undersea mountains and trenches
Explanation: Mapping identifies the real features of the ocean floor. Exam tip: treat identification and measurement as key results.
