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Which of the following statements is correct regarding the continent shelf? (i) Sedimentary deposits are responsible for the continental shelf. (ii) The gradient of the continental shelf is 1 degree or even less. (iii) Average depth up to 200 m.

Which of the following statements is correct regarding the continent shelf? (i) Sedimentary deposits are responsible for the continental shelf. (ii) The gradient of the continental shelf is 1 degree or even less. (iii) Average depth up to 200 m. Correct Answer All are true

The correct answer is Option 4) i.e All are true.

  • Continental Shelf of all oceans together covers 7.5% of the total area of the oceans.
  • The gradient of continental is 1° or even less. Hence statement (ii) is true.
  • The continental shelves are covered with variable thicknesses of sediments brought down by rivers, glaciers etc.
  • Massive sedimentary deposits received over a long time by the continental shelves become the source of fossil fuels . Hence statement (i) is correct.
  • Seaward extension of the continent from the shoreline to the continental edge approx. 200 m deep. Hence Statement (iii) is true.
  • In some places, where the coasts are extremely mountainous, such as at the Rocky Mountains, the continental shelf may be entirely absent.

Importance of continental shelves:

  • Sources of marine food.
  • Provide the richest fishing goods.
  • Potential sides for fossil fuel.

 

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Notes:

Continental slope:

  • When seaward slope immediately becomes steep & gradient to about 1 in 20 with average depth 200 – 3000m.
  • Most of the canyons & trenches are observed in this region
  • The continental slope connects the continental shelf and the ocean basins. ​

​Abyssal Plains:

  • The average depth is 3000 – 6000 m.
  • These plains are covered with fine-grained sediments like clay and silt.

​Oceanic Trench:

  • They are some 3-5 km deeper than the surrounding ocean floor.
  • The trenches lie along the fringes of the deep-sea plain at the bases of continental slopes and along island arcs.
  • The trenches run parallel to the bordering fold mountains or the island chains.
  • Deepest trench of the world → Marina trench (11 km) of Guam Islands (Pacific Ocean) 

 

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