Movement, Relief, Temperature and Salinity of Ocean Water MCQ Questions and Answers

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#1. It is a warm Ocean current, carrying tropical water towards the pole. It flows in the southwest Indian ocean along the east coast of Africa. The ocean current described is

Agulhas current is the warm current that flows through the east coast of Africa in the southwest Indian ocean. It finally merges with the west wind drift.

Option a is incorrect — Benguela current is a cold current that flows near the western coast of Africa in the southeast Atlantic Ocean. It is associated with the Namib desert.

Option b is incorrect – Falkland current is a cold current that flows near the Argentinian coast in the southwest Atlantic Ocean.

Option c is incorrect — Canaries current is a cold current that flows near the Spain-Portugal coast and North- Western Africa in the Atlantic Ocean.

#2. Consider the following pairs:
Which of the pairs given above is/are correctly matched?

The hot Deserts are generally associated with cold currents in its vicinity which creates the desiccating effect and hence low levels of rainfall.

Pair 1 is incorrectly matched. Kalahari Desert — Benguela current. It is a cold current. Benguela current moves from the Southern Ocean (around Antartica) and flows northwards along the West Coast of Africa.

Pair 2 is incorrectly matched. Sahara Desert – Canary current. It is a cold current. ‘The Canary Current flows along the African coast from north to south.

Pair 3 is correctly matched. Atacama Desert — Peru current. Also known as Humboldt current. It is a cold ocean current of low salinity that flows in the north-west direction along the coast of South America.

Pair 4 is correctly matched. Australian desert -West Australian current. It is relatively cold surface current of the southeast Indian Ocean, part of the general counter clockwise movement in the southern section of that ocean.

#3. Which of the following factor(s) influence the flow of Ocean Currents?
1. Planetary winds
2. Temperature difference between the ocean waters at equator and poles
3. Variation in salinity of ocean water from place to place
4. Rotation of Earth
5. Presence of Landmass
Select the correct answer using the code given below:

Statement 1 is correct. Planetary winds play dominant influence on the flow of ocean currents. Trade winds move equatorial water poleward and westwards and warm the eastern coasts of continents. In the temperate latitudes, though westerlies are less consistent than the trade winds, they result in a north- easterly flow of water in the northern hemisphere.

Statement 2 is correct. There is difference in the temperature of ocean waters at the equator and at the poles. As warm water is lighter and rises, and cold water is denser and sinks, warm equatorial waters move slowly along the surface polewards, while the heavier cold waters of the polar regions creep slowly along the bottom of the sea equatorwards.

Statement 3 is correct. ‘The Salinity of ocean waters varies from place to place. Waters of high salinity are denser than waters of low salinity. Hence, waters of low salinity flow on the surface of waters of high salinity while waters of high salinity flow at the bottom towards waters of low salinity.

Statement 4 is correct. The earth’s rotation deflects freely moving objects, including ocean currents, to the right. In the northern hemisphere (ex- the circulation of the Gulf Stream Drift and the Canaries Current), this is a clockwise direction and in the Southern hemisphere, it is an anti- clockwise direction (ex- the Brazilian Current and the West Wind Drift).

Statement 5 is correct. A landmass always obstructs and diverts a current. For instance, the tip of southern Chile diverts part of the West Wind Drift northwards as the Peruvian Current. Similarly, the ‘shoulder’ of Brazil at Cape Sao Roque, divides the west-flowing equatorial currents into the Cayenne Current which flows north- westwards and the Brazilian Current which flows south- westwards.

#4. With reference to cold-water corals, consider the following statements:
1.There are more cold-water coral reefs than tropical reefs in the oceans.
2. Deep water corals requires zooxanthellae to survive.
3. Lophelia reefs are deep water corals which can host species of fish and invertebrates.
Which of the statements given above is/are correct?

Statement 1 is correct: According to the United Nations Environment Programme, there are more cold-water coral reefs worldwide than tropical reefs. ‘The largest cold- water coral reef is the Rost Reef off Norway.

Statement 2 is incorrect: Like tropical corals, they provide habitat to other species, but deep-water corals do not require zooxanthellae to survive.

Statement 3 is correct: Deep-sea corals together with other habitat-forming organisms host a rich fauna of associated organisms. Lophelia reefs can host up to 1,300 species of fish and invertebrates. Various fish aggregate on deep sea reefs. Deep sea corals, sponges and other habitat- forming animals provide protection from currents and predators, nurseries for young fish, and feeding, breeding and spawning areas for numerous fish and shellfish species.

#5. This ocean relief feature is a seaward extension of the continent from the shoreline to the continental edge. Its width varies greatly and may be entirely absent in some areas. They form the richest fishing grounds in the world. The ocean relief feature described in the above paragraph is?

Option a is correct – Continental shelf is a seaward extension of the continent from the shoreline to the continental edge. Its width varies greatly, from a few miles in North Pacific off the continent of North America, to over 100 miles off North-west Europe. In some places where the coasts are extremely mountainous, such as rocky mountain and Andean coasts, the continental shelf may be entirely absent. Their shallowness enables sunlight to penetrate through the water, which encourages the growth of minute plants and other microscopic organisms. They are thus rich in planktons and form the richest fishing grounds in the world.

Option b is incorrect – Continental slope connects the continental shelf and the ocean basins. It begins where the bottom of the continental shelf sharply drops off into a steep slope. The gradient of the slope is about 1 in 20. The depth of the slope region varies between and 3,000 m.

Option c is incorrect — The seaward edge of the continental slope loses gradient at this depth and gives rise to continental rise. It has very little slope.

Option d is incorrect — With increasing depth the rise becomes virtually flat and merges with the abyssal plain. These are the flattest and smoothest regions of the world because ofterrigenous [denoting marine sediment eroded from the land] and shallow water sediments that buries the irregular topography. It covers nearly 40% of the ocean floor.




#6. With reference to Ocean Floor Configuration, which of the following statements is incorrect?

Statement a is correct. An abyssal plain is an underwate plain on the deep ocean floor, usually found at depth between 3,000 metres and 6,000 metres. They ar generally found between the foot ofa continental rise an a mid-ocean ridge. Abyssal plains are the largest habita on earth.

Statement b is correct. The continental slope conne the continental shelf and the ocean basins. It begin where the bottom of the continental shelf sharply drop off into a steep slope. The gradient of the slope regio varies between 2-50. The depth of the slope region vari between 200 and 4000 m. The slope boundary indicat the end of the continents. Canyons and trenches observed in this region.

Statement c is incorrect. ‘The waters along th continental shelf are usually very productive ecosyste This is due to sunlight and nutrients from upwelling an land water runoff. Abyssal plains are less productive ecosystems those along the continental shelf. This is mainly beca sunlight does not penetrate to the sea floor; thu it supports very less plants, making these deep, dar ecosystems less productive.

Statement d is correct. The mid-ocean ridge system forms the longest and largest mountain range on Earth. ‘The mid-ocean ridge consists of thousands of individual volcanoes or volcanic ridge segments which periodically erupt.

#7. Which of the following are located in the Indian Ocean?
1. Socotra-Chagos Ridge
2. Reunion Island
3. Diamantina Trench
4. Mariana Trench
Select the correct answer using the code given below:

Option 1 is correct: Submarine ridges in this ocean include the Lakshadweep-Chagos Ridge [Reunion Hotspot], the Socotra-Chagos Ridge, the Seychelles Ridge, the South Madagascar Ridge, Carlsberg Ridge etc.

Option 2 is correct: The islands of Indian ocean include the Andaman and Nicobar, Sri Lanka, Madagascar and Zanzibar. The Lakshadweep and Maldives are coral islands and Mauritius and the Reunion Islands are of volcanic origin.

Option 3 is correct: Trenches of Indian Ocean includes Sunda and Diamantina.

Option 4 is incorrect: ‘The Mariana Trench is a crescent- shaped trench in the Western Pacific, just east of the Mariana Islands near Guam.

#8. Consider the following statements about Sargasso Sea:
1. It has no land boundary and is de ned by ocean currents.
2. It is located in Atlantic Ocean.
3. It is named after critically endangered tortoise species called Sargassum.
Which of the statements given above is/are correct?

Statement 1 is correct. While all other seas in the world are defined at least in part by land boundaries, the Sargasso Sea is defined only by ocean currents.

Statement 2 is correct. It lies within the Northern Atlantic Subtropical Gyre. The Gulf Stream establishes the Sargasso Sea’s western boundary, while the Sea is further defined to the north by the North Atlantic Current, to the east by the Canary Current, and to the south by the North Atlantic Equatorial Current.

Statement 3 is incorrect. The Sargasso Sea is a vast patch of ocean named for a genus of free-floating seaweed called Sargassum.

#9. Consider the following statements with regard to the Continental slope:
1. Its boundary indicates the end of the continents.
2. Canyons and trenches are observed in this region.
Which of the statements given above is/are correct?

Statement 1 is correct. ‘The Continental slope connects the continental shelf and the ocean basins. It begins where the bottom of the continental shelf sharply drops off into a steep slope. ‘The slope boundary indicates the end of the continents.

Statement 2 is correct. Continental slopes are characterized by numerous submarine canyons and trenches.

‘The gradient of the continental slope region varies between 2-5 degrees. The depth of the slope region varies between 200 and 3000 m.

#10. Consider the following pairs, with reference to relief of the Ocean Floor.
Which of the pairs given above is/are correctly matched?

Pair 1 is incorrectly matched. Seamounts is a mountain with pointed summits, rising from the seafloor that does not reach the surface of the ocean, unlike mid oceanic ridge composed of two chains of mountains separated by a large depression.

Pair 2 is correctly matched. Guyots are flat-topped seamount. They show evidences of gradual subsidence through stages to become flat topped submerged mountains.

Pair 3 is correctly matched. Atolls are low islands found in the tropical oceans consisting of coral reefs surrounding a central depression. It may be a part of the sea (lagoon), or sometimes form enclosing a body of fresh, brackish, or highly saline water.




#11. Consider the following statements:
1.The rate of decrease of temperature of oceans with depths is lower at the equator than at the poles.
2. The winds blowing from the land towards the ocean helps in upwelling of cold water at coast.
3. The enclosed seas in the high latitudes record relatively higher temperature than the open seas.
Which of the statements given below is/are correct?

Statement 1 is incorrect. The rate of decrease of temperature with depths is greater at the equator than at the poles. Though the surface temperature of the seas decreases from equator towards the poles but the temperature at the ocean bottoms is uniform from the equator towards the pole, which means that the rate of decrease of temperature with increasing depth is more rapid near the equator than towards the poles.

Statement 2 is correct. The winds blowing from the land towards the oceans drive warm surface water away from the coast resulting in the upwelling of cold water from below.

Statement 3 is incorrect. The enclosed seas in the low latitudes record relatively higher temperature than the open seas. Whereas the enclosed seas in the high latitudes have lower temperature than the open seas.

#12. Variation is salinity in various seas and oceans is/are directly affected by which of the following factors?
1. Amount of addition of fresh water.
2. Rate of evaporation.
3. Rotation of earth.
Select the correct answer using the code given below:

Factors that affect the salinity of the oceans can be broadly grouped into two categories, (a) factors that increase salinity and (b) factors that decrease salinity.

The factors responsible for increase of salinity are:
1. evaporation Option 2 is correct
2. Ice formation,
3. advection of more saline water
4. mixing with more saline deep water and
5. solution of salt deposits.

The factors that are responsible decrease of salinity are:
1. Precipitation,
2. melting of ice
3. advection of less saline water,
4. mixing with less saline deep water and
5. in flow of fresh water from land Option 1 is correct

Option 3 is incorrect. Rotation of earth has no direct impact on variation of salinity of seas or oceans.

#13. Consider the following statements regarding Ocean salinity.
1. Sea ice contains more salt than Sea water.
2. Halocline is a distinct zone where salinity decreases sharply.
3. Salinity is lower than the average in equatorial waters.
Which of the statement given above is/are incorrect?

Statement 1 is incorrect. Sea ice contains very little salt, about a tenth of the amount of salt that sea water has. is is because ice will not incorporate sea salt into its crystal structure. erefore, sea ice is actually drinkable.

Statement 2 is incorrect. Salinity, generally, increases with depth and there is a distinct zone called the halocline, where salinity increases sharply.

Statement 3 is correct. Salinity is lower than average in equatorial waters because of the heavy daily rainfall and high relative humidity.

#14. Consider the following statements regarding the temperature of ocean water.
1.The surface temperature of ocean water is maximum at the Equator.
2. In higher latitudes the temperature in open sea is lower than in the enclosed sea.
3. Oceans in northern hemisphere receives more heat than oceans of southern hemisphere.
Which of the statements given above is/are incorrect?

Statement 1 is incorrect. The temperature of Ocean water decreases from equator to poles but highest temperature is not found at the equator but at the tropics. Due to high rainfall in the equatorial region, temperature is not so high.

Statement 2 is incorrect. The enclosed seas in the low latitudes record relatively higher temperature than the open seas; whereas the enclosed seas in the high latitudes have lower temperature than the open seas. It is because of the influence of ocean currents, prevailing winds, land- water expanse and latitudinal differences.

Statement 3 is correct. Oceans in the northern hemisphere receives more heat due to their contact with larger extent of land than the oceans in the southern hemisphere.

#15. Which of the following factors contribute to the movement of ocean currents?
1. Temperature di erence of oceanic water
2. Planetary winds
3. Earth’s rotation
4. Gravity
Select the correct answer using the code given below:

Statement 1 is correct. Temperature difference of oceanic water results in movements of oceanic water. Heating by solar energy causes the water to expand. That causes piling up of water near the equator than in the middle latitudes. ‘This results in a slight gradient and water tends to flow down the slope.

Statement 2 is correct.Winds are responsible for both magnitude and direction. Wind blowing on the surface of the ocean pushes the water to move. Friction between the wind and the water surface affects the movement of the water in ocean.

Statement 3 is correct.Earth’s rotation deflects freely moving objects including ocean currents to the right in the northern hemisphere and left in the southern hemisphere.

Statement 4 is correct. Gravity causes movement of water in ocean.Gravity causes the denser water to fall, pushing away the less dense water.




#16. With reference to the minor relief features of the ocean floor, consider the following statements:
1. Submarine Canyons are deep valleys that cut across the continental shelves and slopes.
2. Guyots are flat-topped sea mountains.
Which of the statements given above is/are correct?

Statement 1 is correct. Submarine Canyons are deep valleys that cut across the continental shelves and slopes. They are very similar to the gorges found on the continents. ‘The underwater landslide is one of the reasons for the formation of the submarine canyons. The Hudson Canyon is the best known submarine canyon in the world.

Statement 2 is correct. Guyot is a flat topped seamount that forms with the subsidence of the volcanic mountains. They are usually submerged mountains unlike seamounts that may reach the surface of the ocean.

#17. With reference to Ocean Currents, consider the following statements:
1. Ocean Currents are stronger at the surface than at the depths.
2. Rotation of Earth have an influence on the movement of Ocean Currents. 3. Difference in water density affect the mobility of Ocean Currents.
Which of the statements given above is/are correct?

Ocean currents are the continuous, predictable, directional movement of seawater. It is driven by factors like gravity, wind (Coriolis Effect), and water density.

Statement 1 is correct. Ocean currents are generally referred to by their “drift”. Ocean currents are stronger at the surface and may attain speeds over 5 knots. At depths, currents are generally slow with speed less than 0.5 knots.

Statement 2 is correct. Rotation of Earth leads to Coriolis effect which influences direction of ocean currents. The Coriolis effect causes air and water to move towards the right in the northern hemisphere and the left in the southern hemisphere.

Statement 3 is correct. Differences in water density affect the mobility and speed of ocean currents. Denser water tends to sink whereas lighter water tends to rise. Coldwater ocean currents occur when the cold water at the poles sinks and slowly moves towards the equator. Warmwater currents travel out from the equator along the surface, flowing towards the poles to replace the sinking cold water.

#18. Why thermohaline circulation is called as the “global conveyer Belt”?

Thermohaline circulation is an oceanographic phenomenon which drives a global-scale system of currents. Thus, it is can be said to be the “global conveyor belt”.

There is constant motion in the ocean in the form of a global ocean conveyor belt. This motion is caused by a combination of thermohaline currents in the deep ocean and wind-driven currents on the surface. Cold, salty water is dense and sinks to the bottom of the ocean while warm water is less dense and remains on the surface.

In this, the upper part of the Atlantic thermohaline circulation carries warm, upper ocean water through the tropics and subtropics toward the north pole while the deep part carries cold, dense polar water move southward through the Atlantic, around the tip of Africa, and into the ocean beyond.

#19. With reference to the life forms in the deep ocean, consider the following:
Assertion: Aquatic life form is found even in the submarine trenches.
Reason: Aquatic life forms rely upon the chemosynthesis for energy.

Assertion is correct: Oceanic exploration have revealed the life forms do exist even in trenches. For instance, as per study of Mariana Trench which is the deepest location in earth’s crust about which although little is known about the life forms living in the Trench but despite the lack of light, acidic and freezing conditions, more than 200 known micro-organisms and small creatures, including crustaceans and amphipods, have been known to be living there. The three most common organisms at the bottom of the Mariana Trench are xenophyophores, amphipods and small sea cucumbers (holothurians).

Reason is correct: ‘The deep-sea fauna/life form in trenches has found source of energy alternative to sunlight. To compensate for the absence of photosynthesis, they rely on chemosynthesis carried out by various bacteria, in which they turn inorganic substances into organic.

Chemosynthesis is the process by which certain microbes create energy by mediating chemical reactions. So the animals that live around hydrothermal vents make their living from the chemicals coming out of the seafloor in the vent fluids.

Some have developed much sharper vision while some have abandoned the need of vision, as they rely on touch and vibration.

#20. With reference to the bottom ocean topography of Pacific, Atlantic and Indian Ocean, consider the following statements:
1. Ninety East Ridge is found in Pacic Ocean.
2. New Caledonia reef system is located in South Pacific Ocean.
3. Siberian shelf located in Arctic Ocean is the largest continental shelf on the earth.
4. The Pacific Ocean does not have oceanic ridges like Atlantic and Indian Ocean.
Which of the statements given above is/are correct?

Statement 1 is incorrect. Indian ocean has the Ninety East Ridge which extends from continental shelf of Irrawaddy River mouth. It runs almost North-South direction parallel to 90-degree North longitude up to 40-degree South where it merges with Amsterdam-St Paul Plateau. Central Ridges or Mid Oceanic Ridge in Indian Ocean which is known as Mid Indian Oceanic Ridges extends from Southern tip of Indian Peninsula in the North to Arctica in the South almost in North-South direction and forms a continuous chain of highlands.

Statement 2 correct. The New Caledonia Barrier Reef which is located in the South Pacific is one of the longest reefs in the world, covering a length of 930 miles. It is a home to more than 1000 different species– some of which are still unclassified which live within the reef.

Statement 3 is correct. Pacific continental shelf of South America is represents the example of narrow shelf ( 16km). ‘The Atlantic continental shelf off the east coast of North America represents the example of medium size shelves (96-120km) and extensive shelves having width of a few hundred kilometres are found off the coast of in Arctic Sea, Arafura Sea, China Sea Adriatic Sea etc. Ihe world’s largest continental shelf extends 1,500 km (about 930 miles) from the coast of Siberia into the Arctic Ocean.

Statement 4 is incorrect. The Pacific Ocean does have oceanic ridges. Pacific-Antarctic Ridge (PAR) is a divergent tectonic plate boundary located on the seafloor of the South Pacific Ocean. Also, the east pacific ridge known as Albatross Plateau is 1600 km wide and it extends from the North of New Zealand to the California,




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