Test: Oceanography - 2

30 Questions MCQ Test Geography for UPSC (Civil Services) Prelims | Test: Oceanography - 2

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The Rannutsav has highlighted the Rann of Kutch. This region is well known for which of these geographical features?

Solution: Sunderban delta is the largest in India, so A is wrong. Rann of Kutch is one of the largest salt deserts in the world. In summer monsoon, the flat desert of salty clay and mudflats fills with standing water. Kutch is also the cultural district of Gujarat, which has been given a new identity by Rannutsav.


Bay of Bengal shows low salinity of water as compared to the Arabian Sea due to

1. Huge influx of fresh water in the Bay of Bengal

2. High evaporation in the Arabian Sea as compared to the Bay of Bengal

3. Low influx of fresh water in the Arabian Sea

Choose the correct answer using the codes below:

Solution: The average salinity of the Indian Ocean is 35 o/oo. The low salinity trend is observed in the Bay of Bengal due to the influx of river water by the river Ganga. On the contrary, the Arabian Sea shows higher salinity due to high evaporation and a low influx of fresh water.


Which of the following factors has no or negligible effect on the salinity of oceans.

Solution: Some of the salt in the oceans comes from undersea volcanoes and hydrothermal vents. But its effect is negligible compared to other sources.


Tidal currents are

Solution: Tidal currents are the tides which are channelled between islands, bays and estuaries. Tidal current has significance in power generation.


Tidal range is the difference between high tide and low tide. Which of the following factors can influence the tidal range?

1. Depth of ocean water

2. Ocean current

3. Openness and closeness of the sea

4. Configuration of coastline

5. Gravitational pull of Sun and Moon

Select the correct answer using the code given below

Solution: Ocean current does not influence High tide or Low tide. All the other factors influence the tidal range.


Factors that affect the formation of tides in the Ocean are

1. Alignment of Earth, Sun and Moon

2. Relative distance between the Moon, Earth and Sun

3. Shape of bays and estuaries where tides are formed

4. Local wind and weather patterns in Ocean

Select the correct answer using the codes below:

  • The strong gravitational pull exerted by the Sun and the Moon on the Earth’s surface causes the tides. The tides are caused by the strong gravitational pull exerted on the surface of the Earth by the Sun and the Moon. Under the influence of the gravitational force of the Moon, the Earth’s water closer to the Moon is pulled and causes high tide.

  • The intensity of tides can be magnified by the shape of bays and estuaries. Especially funnel-shaped bays can dramatically alter the magnitude of ' the tide. The classic example of this effect is the Bay of Fundy in Nova Scotia, which has the highest tides in the world (15 km). Incoming tides are scattered by the narrow inlets and shallow water. Strong seasonal flows in the spring can severely alter or mask the incoming tide in estuaries with strong tidal rivers, e.g. the Delaware River and Columbia River.

  • Powerful offshore winds move water away from coastlines, magnify low tide exposures. Onshore winds can pile up water on the shoreline, virtually eliminating exposures to low tide. Sea levels are depressed by high-pressure systems, leading to clear sunny days with extremely low tides. By contrast, low-pressure systems that contribute to cloudy, rainy conditions typically are associated with tides that are much higher than predicted.


Tides in the ocean are highest in

  • The tides are caused by the strong gravitational pull exerted on the surface of the Earth by the Sun and the Moon. Under the influence of the gravitational force of the Moon, the Earth’s water closer to the Moon is pulled and causes high tide.

  • The Sun, the Moon and the Earth are in the same line during the full moon and the new moon days, and the highest tide called spring tides can be seen on those days.

  • But at the first and last quarters of the Moon, the ocean waters are drawn by the gravitational pull of Sun and Earth in diagonally opposite directions, resulting in low tides called neap tides.


Tidal energy is based on which of the following?

Solution: Tidal energy is generated from tides. By building dams at narrow openings of the sea, tidal energy can be harnessed. The tidal energy on the high tide days is used to operate the turbines that are mounted on the dam to generate electricity. Enormous tidal mill farms are found in Russia, France and India’s Gulf of Kutch.


The California Ocean current, which flows along the west coast of North America, is a

  • The California Current is a Pacific Ocean current that moves southward along the western coast of North America, beginning off southern British Columbia and ending off southern Baja California Peninsula.

  • It is considered an Eastern boundary current due to the influence of the North American coastline on its course.

  • It is also one of five major coastal currents affiliated with strong upwelling zones, the others being the Humboldt Current, the Canary Current, the Benguela Current, and the Somali Current.

  • The California Current is part of the North Pacific Gyre, a large swirling current that occupies the northern basin of the Pacific.


The meeting of the cold Labrador current and warm Gulf stream current leads to

1. Dense mist and fog

2. An Arid Climate Zone

Which of the above is/are correct?

  • When cold and warm ocean current meets, the warm ocean current condenses after getting in contact with cold air and it results in fog.

  • It also leads to a high rate of precipitation in the region. The circulation in the area where the Labrador Current and Gulf Stream meet is one of the most complex and variable regions in the world.


Which of these forces help in the movement or generation of ocean currents?

1. Coriolis force

2. Gravitational force

3. Solar insolation

4. Movement of wind

Select the correct answer using the codes below:

  • Surface currents are generated largely by the wind. Their patterns are determined by wind direction, Coriolis forces from the Earth’s rotation, and the position of landforms that interact with the currents.

  • Near the equator, the ocean water is about 8 cm higher in level than in the middle latitudes. This causes a very slight gradient and water tends to flow down the slope.

  • Solar energy makes the current warm or cold and decides their circulatory patterns.


It is the western boundary current of the southwest Indian Ocean. It acts as an oceanic convergence zone. This ocean current is

  • It flows down the east coast of Africa from 27°S to 40°S. It is narrow, swift and strong. It is even suggested that the Agulhas is the largest western boundary current in the world ocean. The Agulhas acts as an oceanic convergence zone.

  • Due to mass continuity, this drives surface waters down, resulting in the upwelling of cold, nutrient-rich water south of the current.


World’s best fishing grounds are formed where

Solution: The following conditions are good for fisheries production and catch: Coastal upwelling of nutrient-rich colder water Abundance of phytoplankton Meeting of warm and cold currents Shallow continental shelves in cold regions It is exemplified by the fact that one of the world’s richest fishing grounds situated around the coast of Iceland.


Within the Earth’s ocean and atmosphere, Rossby waves form as a result of

Solution: Waves in the ocean come in many different shapes and sizes. Slow-moving oceanic Rossby waves are fundamentally different from ocean surface waves.
  • Unlike waves that break along the shore, Rossby waves are huge, undulating movements of the ocean that stretch horizontally across the planet for hundreds of kilometres in a westward direction.

  • Also known as planetary waves, they naturally occur in rotating fluids.

  • They are so large and massive that they can change Earth’s climate conditions.


Which of the following factors affect the direction of movement of ocean currents?

1. Ocean Salinity

2. Ocean temperature

3. The Earth’s rotation

4. The planetary winds

Choose the correct answer using the codes below

Solution: All the above factors contribute to determining the direction of the movement of ocean currents.


Cold currents bring cold water into warm water areas. These currents are usually found on the

1. West coast of the continents in the low and middle latitudes in both hemispheres

2. East coasts in the higher latitudes in the Northern Hemisphere

Which of the above is/are correct?

Solution: Ocean currents can also be classified based on temperature: as cold currents and warm currents

(i) Cold currents are usually found on the west coast of the continents in the low and middle latitudes (true in both hemispheres) and on the east coast in the higher latitudes in the Northern Hemisphere.

(ii) Warm currents bring warm water into cold water areas and are usually observed on the east coast of continents in the low and middle latitudes (true in both hemispheres). In the Northern Hemisphere, they are found on the west coasts of continents in high latitude.


Equatorial counter-currents are unique because

  • Equatorial counter-currents are major surface flows that carry water eastwards in the Atlantic, Indian, and Pacific Oceans.

  • They are located near the equator and are sandwiched between two westward flowing currents, the North Equatorial Current and the South Equatorial Current.

  • Equatorial counter-currents are unique, in that they flow in the opposite direction of the surface winds. The other major surface currents in the tropics flow in the same direction as the prevailing winds.

  • The equatorial counter-currents are thus driven by a distinct surface wind pattern in the tropics. Strong westward trade winds result in westward surface flow in most of the tropical Atlantic and Pacific Oceans.


The Humboldt Current is

Solution: The Humboldt Current is a cold, low-salinity ocean current that flows north along the west coast of South America from the southern tip of Chile to northern Peru. Also called the Peru Current, it is an eastern boundary current flowing in the direction of the equator.


Consider the following statements:

1. It is found that subsurface ocean currents once absorbed carbon dioxide from winds and released them elsewhere.

2. Ocean currents redistribute heat in the oceans.

Which of the above statements is/are correct?

Solution: Most of the debate on climate change focuses on greenhouse gases released into the atmosphere. But it has emerged that ocean circulation has an equally important role. It was believed that the severe cooling of the Earth underwent 2.7 million years ago was caused by changes in carbon dioxide (CO2) levels. But analyses of ocean sediments (2.5 million-to 3.3 million-year-old) suggest the cooling happened due to the emergence of sub-surface ocean currents. These currents absorb heat and CO2 from winds blowing close to the ocean surface in the Atlantic and release them in the Pacific.


Which of the following ocean currents is/are cold ocean currents?

1. Benguela Current

2. Labrador Current

3. Gulf Stream

4. Brazilian Current

Choose the correct answer using the codes below

Solution: Gulf stream and Brazilian current are warm ocean currents.


The Chilean and Peruvian coasts are practically rainless. This is because of

Solution: Humboldt current passes close to it.


The Agulhas current acts as an oceanic convergence zone. This zone has higher primary productivity than surrounding waters. This is because

1. The zone is a meeting point of all major ocean currents of the Indian Ocean.

2. There is an upwelling of cold ocean water from the lower layers of the ocean.

Which of the above is/are correct?

Solution: Agulhas current is a major Indian Ocean current.
  • A convergence zone is a region in the atmosphere where two prevailing flows meet. It is not a meeting of all major ocean currents.

  • There is an upwelling of cold, nutrient-rich water south of the current. Additionally, the convergence tends to increase the concentration of plankton in and around the Agulhas.

Both Of These factors result in the area being one of enhanced primary productivity as compared to the surrounding waters.


The West Wind Drift is the most important current in the Southern Ocean and the only current that flows completely around the globe. However, its circulation is circumpolar in nature due to

  • The Antarctic Circumpolar Current (ACC) (West Wind Drift) is an ocean current that flows clockwise from west to east around Antarctica.

  • It is the largest ocean current. The ACC connects the Atlantic, Pacific and Indian Oceans, and serves as a principal pathway of exchange between them. The circumpolar current is driven by the strong westerly winds in the latitudes of the Southern Ocean.

  • The current is circumpolar due to the lack of any landmass connecting with Antarctica and this keeps warm ocean waters away from Antarctica, enabling that continent to maintain its huge ice sheet. It means that in the Southern Hemisphere since there is no obstruction of the Antarctica continent, the west wind drifts across the Pacific, the Atlantic and the Indian Ocean in the south, forming a circulation (also known as the westerly circulation).


Consider the following statements:

Assertion (A): In the North Indian Ocean, there is a complete reversal of the direction of ocean currents between summer and winter.

Reason (R): Monsoon winds change direction from South-west to Northeast.

In the context of the above, which of these is/are correct?


In the North Indian Ocean, a complete reversal of direction of Monsoon Current, twice a year is observed between summer and winter because the Monsoon winds change their direction according to seasons. South-West Monsoon Current (warm).

  • In the summer season, the monsoon winds blow from south-west to north-east. Consequently, the ocean current also flows from south-west to north-east direction.

  • The main current moves in the Arabian Sea and the Bay of Bengal along the coast of India. North-East Monsoon Current (warm)

  • In the winter season, the monsoon winds blow from northeast to south-west. The ocean current also flows from northeast to south-west under the influence of these winds.


Consider the following about the phenomenon of Upwelling in the Indian Ocean:

1. It is a seasonal phenomenon associated with the monsoon.

2. It is weakest in regions closest to the equator and strongest near subtropical latitudes.

3. It brings nutrient-rich water to the surface and enhances the biological productivity of the region.

Select the correct answer using the codes below:

  • Associated with the monsoon, it sees the migration of deep-sea oxygen minimum zone (OMZ) towards the coast. During the northeast monsoon, strong upwelling occurs along the western coast of India.

  • During the southwest monsoon, upwelling occurs off the Somali and Arabian coasts and south of Java. It is most intense between 5° and 11° N, with the replacement of wanner surface water by the water of about 14 °C.

  • It involves wind-driven motion of dense, cooler, and usually, nutrient-rich water towards the ocean surface, replacing the warmer, usually nutrient-depleted surface water. The nutrient-rich upwelled water stimulates the growth and reproduction of primary producers such as phytoplankton.


Regarding corals, consider the following statements:

1. Coral are marine invertebrate species.

2. Corals secrete calcium carbonate which forms the outer skeleton.

3. Corals grow in shallow waters to absorb sunlight for photosynthesis to produce their food.

Which of the above is/are correct?

  • Live coral is colonies of small animals embedded in calcium carbonate shells. It is a mistake to think of coral as plants or rocks. Coral heads consist of accumulations of individual animals called polyps, arranged in diverse shapes.

  • Reef-building or hermatypic corals live only in the photic zone (above 50 m), the depth to which sufficient sunlight penetrates the water, allowing photosynthesis to occur.

  • Coral polyps do not photosynthesise, but have a symbiotic relationship with zooxanthellae; these organisms live within the tissues of polyps and provide organic nutrients that nourish the polyp. Because of this relationship, coral reefs grow much faster in clear water, which admits more sunlight.


Consider the following statements regarding the formation of corals:

1. The water temperature must be between 15 and 20°C

2. The depth of the water should not be more than 180 feet

3. The water should be fresh and should have rich sediment to provide nutrition

Which of the above is/are correct?

Solution: Coral formations require temperature not less than 20°C and saline water free from sediments.


Tropical coral reefs are very productive ecosystems. Which of the following are benefits accrued from coral reefs?

1. They sustain about a quarter of the ocean’s fish population.

2. Coral reefs break the power of the waves during storms, cyclones and tsunamis.

3. Coral reefs can provide potent anti-HIV proteins.

Select the correct answer using the codes below:

  • Coral reefs are vital to the world’s fisheries. They film the nurseries for about a quarter of the ocean’s fish and thus provide revenue for local communities as well as national and international fishing fleets.

  • Coral reefs break the power of the waves during storms, hurricanes, typhoons, and even tsunamis. By helping to prevent coastal erosion, flooding, and loss of property on the shore, the reefs save billions of dollars each year in terms of reduced insurance and reconstruction costs and reduced need to build costly coastal defences.

  • A new class of proteins capable of blocking HIV from penetrating T-cells has been discovered. The proteins have been found in a coral from Australia’s northern coast. Coral reefs are also being used in the treatment of cancer.


Regarding Lakshadweep islands, consider the following statements:

1. They form the smallest Union Territories of Government of India.

2. The islands do not have any aboriginal groups.

3. Lakshadweep has no coral reefs.

Which of the above is/are correct?

Solution: Lakshadweep is an archipelago of twelve atolls, three reefs and five submerged banks, with a total of about thirty-nine islands and islets. The reefs are in fact also atolls, although mostly submerged, with only small unvegetated sand cays above the high-water mark. The submerged banks are sunken atolls.


Which of the following islands are not coral islands:

1. Lakshadweep Islands

2. Maldives

3. Bermuda Islands

4. Andaman and Nicobar

Choose the correct answer using the codes below:

Solution: Andaman and Nicobar islands are not of coral origin. But few coral pockets are seen in these islands.

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