UPSC Static Quiz – Geography : 23 September 2024

Solution: a)

Statement 1 is incorrect because the depth of water over the continental shelf is between 120 and 370 meters, not kilometers. This is the depth range for shallow seas above continental shelves.

Statement 2 is incorrect. Although fold mountains running parallel to the coast can limit the width of the continental shelf, it is not universally true that wider shelves are only found where such mountains are absent. For example, the continental shelf is wider along the eastern coast of India compared to the western coast, despite the absence of fold mountains on either side.

Statement 3 is correct. Many continental shelves have formed through the erosional action of waves, deposition of river-borne material, and in some cases, glacial deposits in regions previously covered by ice sheets.

Solution: d)

Continental shelves are important for the fishing industry because their shallow waters allow sunlight to penetrate to the ocean floor, which promotes the growth of plankton. These planktons form the base of the marine food chain and serve as food for many fish species, making the shelves rich fishing grounds.

Solution: b)

Continental shelves are rich in resources like petroleum, natural gas, sand, and gravel. These shelves are essential areas for oil drilling and other mineral extractions. However, gold is not commonly mined from continental shelves, as it is generally found in other types of geological deposits, such as riverbeds and underground veins.

Solution: d)

Statement 1 is incorrect because the gradient of the continental slope is typically about 2.5 degrees, not 15 degrees. The slope is steeper than the shelf, but not to the extent described.

Statement 2 is incorrect. The continental slope has very little sediment accumulation compared to the continental shelf, as its steepness prevents significant sediment deposits. Sediments are more likely to be found at the base of the slope, forming the continental rise.

Statement 3 is incorrect. The continental slope is not biologically rich because it is located at greater depths where sunlight does not reach, and nutrients are scarce, limiting marine biodiversity compared to the continental shelf.

Solution: c)

Statement 1 is incorrect. Abyssal plains were once thought to be featureless, but modern surveys have shown that they contain submarine plateaus, hills, seamounts, and guyots, making them irregular in certain regions.

Statement 2 is incorrect. The sediments covering the abyssal plains near continents are mostly terrigenous, originating from land (brought by rivers, winds, and ocean currents), rather than being primarily volcanic.

Statement 3 is correct. In regions with abundant marine life, the sediments on the abyssal plains are often composed of oozes, formed from the accumulation of the remains of microscopic marine organisms like foraminifera and diatoms. These oozes form a thick sedimentary layer on the ocean floor.