The continental shelf is important for fisheries mainly because:
- A.It is the deepest part of the ocean floor
- B.It is shallow, so sunlight reaches the bottom and plankton grows well
- C.It has the highest salinity in the ocean
- D.It is free from the effect of ocean currents
Correct answer
Explanation
The correct answer is B. The continental shelf is the gently sloping submerged edge of a continent, usually taken down to about two hundred metres. Because it is shallow, sunlight penetrates to the sea bed and supports abundant plankton, and rivers add nutrients from the land as well. Fish gather where plankton is plentiful, so almost all the world's major fishing grounds, and most offshore petroleum, lie on continental shelves.
Option A is wrong because the deepest parts of the ocean are the trenches, which lie far beyond the shelf and are dark and nearly lifeless by comparison. Option C is wrong because the shelf usually has slightly lower salinity than the open ocean, since rivers dilute it. Option D is wrong as well: currents and upwelling reach shelf waters constantly, and in fact the upwelling of nutrients along some shelves is exactly what makes them so productive.
Read the full article: Oceans and Ocean Currents: Tides, Salinity and PYQs
Practice Questions
View allWhich of the following ocean currents is associated with the Indian Ocean?
- A.Florida current
- B.Canary current
- C.Agulhas current
- D.Kurile current
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It is a warm current of the Indian Ocean that flows southward along the eastern coast of southern Africa, carrying tropical water towards the Cape before most of it turns back into the Indian Ocean.
Read the full explanation →El Nino is a name given to the periodic development of a warm ocean current along the coast of _______.
- A.Columbia
- B.Peru
- C.Chile
- D.Bolivia
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El Nino, Spanish for the child, is the warm surface water that appears off the coast of Peru and Ecuador around Christmas in some years, replacing the normally cold Peru or Humboldt current.
Read the full explanation →With which of the following oceans would you associate the 'Ring of Fire'?
- A.Pacific
- B.Indian
- C.Atlantic
- D.Arctic
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The Ring of Fire is a horseshoe-shaped belt running around the rim of the Pacific Ocean, from the Andes up the west coast of the Americas, across the Aleutians and down through Japan, the Philippines and Indonesia to New Zealand.
Read the full explanation →The percentage of earth's water found in the oceans is ______.
- A.94 percent
- B.97.2 percent
- C.90.2 percent
- D.92.2 percent
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Textbooks describing the distribution of water on earth give about 97.2 per cent as ocean water, roughly 2 per cent locked in ice caps and glaciers, and well under 1 per cent as groundwater, lakes, rivers, soil moisture and water vapour together.
Read the full explanation →Spring tides, the highest tides of the month, occur when:
- A.The sun, the earth and the moon are in a straight line
- B.The sun and the moon are at right angles with respect to the earth
- C.The moon is farthest from the earth
- D.The season of spring begins in the northern hemisphere
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Spring tides occur at new moon and at full moon, when the sun, the earth and the moon lie in a straight line, a position called syzygy.
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