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UPSC CIVIL SERVICES EXAMINATION PRELIMS SPECIAL 1995 - 2018 PREVIOUS YEAR QUESTIONS www.civilstap.com Oceanography
UPSC CIVIL SERVICES EXAMINATION
PRELIMS SPECIAL
1995 - 2018
PREVIOUS YEAR QUESTIONS
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Oceanography
CHAPTER LISTING
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Unit Chapter
World Geography
Physical Geography
Geomorphology
Climatology
Oceanography
Biogeography
Social Geography
Economic Geography
Indian Geography
Physical Geography
Basics of India
Physical features
River systems
Climate
Agriculture
Vegetation and Fauna
Social Geography
Economic Geography
L4-L7
L1 – L3
L8
CHAPTER LISTING
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Q 71-80
Chapter Topics
Oceanography
Ocean Relief
Ocean Salinity
Ocean Deposits
Ocean Currents
El Nino & La Nina
Waves & Tides
Q. On the planet earth, most of the freshwater exists as ice caps and glaciers. Out of the
remaining freshwater, the largest proportion [2013 - I]
(a) is found in atmosphere as moisture and clouds
(b) is found in freshwater lakes and rivers
(c) exists as groundwater
(d) exists as soil moisture
QUESTION 71
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QUESTION 71
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Distribution of Water:
Q. On the planet earth, most of the freshwater exists as ice caps and glaciers. Out of the
remaining freshwater, the largest proportion [2013 - I]
(a) is found in atmosphere as moisture and clouds
(b) is found in freshwater lakes and rivers
(c) exists as groundwater
(d) exists as soil moisture
Answer: c
QUESTION 71
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Q. . Consider the following factors: [2012 - I]
1. Rotation of the Earth
2. Air pressure and wind
3. Density of ocean water
4. Revolution of the Earth
Which of the above factors influence the ocean currents?
(a) 1 and 2 only
(b) 1, 2 and 3
(c) 1 and 4
(d) 2, 3 and 4
QUESTION 72
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QUESTION 72
They represent a regular movement of a volume of water in a definite path and direction.
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Ocean Currents
• Ocean currents are influenced by two types of forces namely: Primary forces: that initiate the movement of water Secondary forces: that influence the currents to flow.
Factors influencing Ocean Currents
• Heating by solar energy causes the water to expand. That is why, near the equator the oceanwater 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. The flow is normallyfrom east to west.
Primary Forces
Insolation
QUESTION 72
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Gravity tends to pull the water down to pile and create gradient variation.
Gravity
• Wind blowing on the surface of the ocean pushes the water to move. Friction between the windand the water surface affects the movement of the water body in its course.
• Winds are responsible for both magnitude and direction [Coriolis force also affects direction] ofthe ocean currents. Example: Monsoon winds are responsible for the seasonal reversal of oceancurrents in the Indian ocean.
• In regions of pronounced monsoonal flow [Northern Indian Ocean], the monsoon winds influencethe current movements which change directions according to seasons.
Winds
• Differences in water density affect vertical mobility of ocean currents (vertical currents).• Water with high salinity is denser than water with low salinity and in the same way cold water is
denser than warm water.• Denser water tends to sink, while relatively lighter water tends to rise.
Salinity
QUESTION 72
• Configuration of coast lines also influence thedirection of ocean currents by blocking anddiverting their path.
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Shape of coast lines
• The Coriolis force intervenes and causes the waterto move to the right in the northern hemisphereand to the left in the southern hemisphere.
• These large accumulations of water and the flowaround them are called Gyres. These produce largecircular currents in all the ocean basins. One suchcircular current is the Sargasso Sea.
Coriolis Force
Secondary Forces
Q. . Consider the following factors: [2012 - I]
1. Rotation of the Earth
2. Air pressure and wind
3. Density of ocean water
4. Revolution of the Earth
Which of the above factors influence the ocean currents?
(a) 1 and 2 only
(b) 1, 2 and 3
(c) 1 and 4
(d) 2, 3 and 4
Answer: b
QUESTION 72
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Q. In the given map, which one of the following pairs of ocean currents are shown? [1999]
(a) Benguela and Falkland
(b) Canary and Humboldt
(c) Agulhas and Guinea
(d) Benguela and Guinea
QUESTION 73
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QUESTION 73
• Surface currents constitute about 10 per cent of all the water in the ocean, these waters are theupper 400 m of the ocean;
• Deep water currents make up the other 90 per cent of the ocean water. These waters movearound the ocean basins due to variations in the density and gravity.
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Types of Ocean Currents
Based on Temperature
Based on Depth
• Cold currents bring cold water into warm water areas [from high latitudes to low latitudes]. Thesecurrents are usually found on the west coast of the continents in the low and middle latitudesand on the east coast in the higher latitudes in the Northern Hemisphere;
• Warm currents bring warm water into cold water areas[low to high latitudes] and are usuallyobserved on the east coast of continents in the low and middle latitudes (true in bothhemispheres).
QUESTION 73
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Q. In the given map, which one of the following pairs of ocean currents are shown? [1999]
(a) Benguela and Falkland
(b) Canary and Humboldt
(c) Agulhas and Guinea
(d) Benguela and Guinea
Answer: d
QUESTION 73
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Q. Consider the following statements:
1. Ocean currents are slow-surface movement of water in the ocean.
2. Ocean currents assist in maintaining the Earth's heat balance
3. Ocean currents are set in motion primarily by prevailing winds
4. Ocean currents are affected by the configuration of the ocean
Which of these statements are correct? [2002]
(a) 1 and 2
(b) 2, 3 and 4
(c) 1, 3 and 4
(d) 1, 2, 3 and 4
QUESTION 74
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QUESTION 74
• Ocean Currents help in transfer of surplus heatfrom energy surplus areas of lower latitudes toenergy deficient areas of higher latitudes.
• Warm ocean currents raise the temperature in coldareas while the cold currents decrease thetemperature in warm ocean areas.
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Significance of Ocean Currents
Moderating Effect
Maintaining Heat Balance
• They are responsible for moderate temperatures atcoasts. [North Atlantic Drift brings warmness toEngland. Canary cold current brings cooling effectto Spain, Portugal etc.]
QUESTION 74
• Cold ocean currents have a direct effecton desert formation in west coast regions ofthe tropical and subtropical continents.
• There is fog and most of the areas are ariddue to desiccating effect (loss of moisture).
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Significance of Ocean Currents
Rains
Desert Formation
Warm currents flow parallel to the east coastsof the continents in tropical and subtropicallatitudes. This results in warm and rainyclimates. These areas lie in the western marginsof the subtropical anti-cyclones.
QUESTION 74
• The mixing of warm and coldcurrents help to replenish theoxygen and favor the growthof planktons, the primary food forfish population. The best fishinggrounds of the world exist mainly inthese mixing zones.
• Example: Grand Banks aroundNewfoundland, Canada and North-Eastern Coast of Japan.
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Significance of Ocean Currents
Tropical Cyclones
Fishing
Ocean Currents pile up warm waters in tropics and this warm water is the major force behind tropical cyclones.
QUESTION 74
• Currents are referred to by their “drift”. Usually,the currents are strongest near the surface andmay attain speeds over five knots (1 knot = ~1.8km).
• Ships usually follow routes which are aided byocean currents and winds.
• Example: If a ship wants to travel from Mexico toPhilippines, it can use the route along the NorthEquatorial Drift which flows from east to west.
• When it wants to travel from Philippines toMexico, it can follow the route along thedoldrums when there is counter equatorialcurrent flowing from west to east.
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Significance of Ocean Currents
Navigation
Q. Consider the following statements:
1. Ocean currents are slow-surface movement of water in the ocean.
2. Ocean currents assist in maintaining the Earth's heat balance
3. Ocean currents are set in motion primarily by prevailing winds
4. Ocean currents are affected by the configuration of the ocean
Which of these statements are correct? [2002]
(a) 1 and 2
(b) 2, 3 and 4
(c) 1, 3 and 4
(d) 1, 2, 3 and 4
Answer: d
QUESTION 74
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Q. What could be the main reason/reasons for the formation of African and Eurasian desert
belt? [2011 - I]
1. It is located in the sub-tropical high pressure cells.
2. It is under the influence of warm ocean currents.
Which of the statements given above is/are correct in this context ?
(a) 1 only
(b) 2 only
(c) Both 1 and 2
(d) Neither 1 nor 2
Answer: a
QUESTION 75
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Q. The most important fishing grounds of the world are found in the regions where [2013 - I]
(a) warm and cold atmospheric currents meet
(b) rivers drain out large amounts of freshwater into the sea
(c) warm and cold oceanic currents meet
(d) continental shelf is undulating
QUESTION 76 (DO IT YOURSELF)
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Q. What explains the eastward flow of the equatorial counter-current? [2015 - I]
(a) The Earth's rotation on its axis
(b) Convergence of the two equatorial currents
(c) Difference in salinity of water
(d) Occurrence of the belt of calm near the equator
QUESTION 77
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QUESTION 77
• As the North Equatorial Current and SouthEquatorial Current take the water from east tothe western part of the ocean basins, there is apiling up water in the western parts of oceanbasins ( or eastern boundaries of landmassesnear the equator).
• This piled up water then flows from west to east,under the effect of gravity, resulting in CounterEquatorial Current (CEC).
• Moreover, as the Doldrums around the Equatorare zone of very feeble winds, counter currentscan flow without much hindrance.
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Equatorial Counter Currents
Q. What explains the eastward flow of the equatorial counter-current? [2015 - I]
(a) The Earth's rotation on its axis
(b) Convergence of the two equatorial currents
(c) Difference in salinity of water
(d) Occurrence of the belt of calm near the equator
Answer: b
QUESTION 77
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Q. Which one of the following factors is responsible for the change in the regular direction of
the ocean currents in the Indian Ocean? [1997]
(a) Indian Ocean is half an ocean
(b) Indian Ocean has monsoon drift
(c) Indian Ocean is a land-locked ocean
(d) Indian Ocean has greater variation in salinity
QUESTION 78
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QUESTION 78
• The currents in the northern portion of the IndianOcean change their direction from season to seasonin response to the seasonal rhythm of the monsoons.
• The effect of winds is comparatively morepronounced in the Indian Ocean.
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Monsoon & Indian Ocean Currents
Winter Circulation
• Under the influence of prevailing trade winds[easterly trade winds], the north equatorial currentand the south equatorial current start from the southof Indonesian islands, moving from east to west.
• The north-east monsoons drive the water along thecoast of Bay of Bengal to circulate in an anti-clockwisedirection.
• Similarly, the water along the coast of Arabian Seaalso circulate in an anti-clockwise circulation.
QUESTION 78
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Monsoon & Indian Ocean Currents
Summer Circulation
• North Equatorial Current Counter-Equatorial Currentare Absent
• In summer, due to the effects of the strong south-west monsoon and the absence of the north-easttrades, a strong current flows from west to east,which completely obliterates the north equatorialcurrent. Hence, there is no counter-equatorial currentas well.
• Thus, the circulation of water in the northern part ofthe ocean is clockwise during this season.
Q. Which one of the following factors is responsible for the change in the regular direction of
the ocean currents in the Indian Ocean? [1997]
(a) Indian Ocean is half an ocean
(b) Indian Ocean has monsoon drift
(c) Indian Ocean is a land-locked ocean
(d) Indian Ocean has greater variation in salinity
Answer: b
QUESTION 78
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Q. With reference to ‘Indian Ocean Dipole (IOD)’ sometimes mentioned in the news while
forecasting Indian monsoon, which of the following statements is/are correct?
1. IOD phenomenon is characterized by a difference in sea surface temperature between tropical
Western Indian Ocean and tropical Eastern Pacific Ocean.
2. An IOD phenomenon can influence an El Nino’s impact on the monsoon.
Select the correct answer using the code given below: [2017]
(a) 1 only
(b) 2 only
(c) Both 1 and 2
(d) Neither 1 nor 2
QUESTION 79
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QUESTION 79
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Indian Ocean Dipole
It is the difference in sea surface temperature betweentwo areas (or poles) – a western pole in the ArabianSea (western Indian Ocean) and an eastern pole in theeastern Indian Ocean south of Indonesia.
• When eastern Indian Ocean is unusually coldcompared to western pole [Thus high pressure ineast & low pressure in warm west Indian ocean &winds over the Indian Ocean consequently blowfrom east to west.
• This is good for Indian Monsoons as moreevaporation occurs in warm waters & SWmonsoonal winds blowing over the region beforestriking India are able to carry more moisture.
Positive-Indian Ocean Dipole
QUESTION 79
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Negative Indian Ocean Dipole
• When western Indian Ocean is unusually coldcompared to eastern pole [Thus high pressure inwest & low pressure in warm east Indian ocean& winds over the Indian Ocean consequentlyblow from west to east.
• Thus, region around Indonesia is much warmerand rainier while Indian monsoon is weakenedbecause of less evaporation in west IndianOcean and Arabian sea. .
Since the anomaly is similar to El Nino SouthernOscillation (ENSO), IOD (Equatorial Indian OceanOscillation) is also known as Indian Nino.
Q. With reference to ‘Indian Ocean Dipole (IOD)’ sometimes mentioned in the news while
forecasting Indian monsoon, which of the following statements is/are correct?
1. IOD phenomenon is characterized by a difference in sea surface temperature between tropical
Western Indian Ocean and tropical Eastern Pacific Ocean.
2. An IOD phenomenon can influence an El Nino’s impact on the monsoon.
Select the correct answer using the code given below: [2017]
(a) 1 only
(b) 2 only
(c) Both 1 and 2
(d) Neither 1 nor 2
Answer: b
QUESTION 79
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Q. La Nina is suspected to have caused recent floods in Australia. How is La Nina different from
El Nino ?
1. La Nina is characterized by unusually cold ocean temperature in equatorial Indian Ocean whereas
El Nino is characterized by unusually warm ocean temperature in the equatorial Pacific Ocean.
2. El Nino has adverse effect on south-west monsoon of India, but La Nina has no effect on monsoon
climate.
Which of the statements given above is/are correct? [2011 - I]
(a) 1 only
(b) 2 only
(c) Both 1 and 2
(d) Neither 1 nor 2
QUESTION 80
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QUESTION 80
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El Nino
El Niño is the name given to occasional development of warm ocean surface waters along the coast of Ecuador & Peru.
Normal Condition El Nino Condition
QUESTION 80
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La Nina
This phenomenon is just theopposite of El Niño. In some years,the trade winds can becomeextremely strong and an abnormalaccumulation of cold water canoccur in the central and easternPacific. This event is called a LaNiña.La Niña results in abnormally heavymonsoons in India and SE Asia, wetwinter in Eastern Africa & Australia,and drought in southern UnitedStates & South America.
Q. La Nina is suspected to have caused recent floods in Australia. How is La Nina different from
El Nino ?
1. La Nina is characterized by unusually cold ocean temperature in equatorial Indian Ocean whereas
El Nino is characterized by unusually warm ocean temperature in the equatorial Pacific Ocean.
2. El Nino has adverse effect on south-west monsoon of India, but La Nina has no effect on monsoon
climate.
Which of the statements given above is/are correct? [2011 - I]
(a) 1 only
(b) 2 only
(c) Both 1 and 2
(d) Neither 1 nor 2
Answer: d
QUESTION 80
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Q. In which one of the following oceans Diamantine Trench is situated? [2006]
(a) Pacific Ocean
(b) Atlantic Ocean
(c) Indian Ocean
(d) Arctic Ocean
QUESTION 81
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QUESTION 81
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Ocean Relief
Major relief features of oceanbottom are:• The Continental Shelf• The Continental Slope• The Continental Rise• The Abyssal Plain or Deep Sea
Plain
QUESTION 81
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Continental Shelf
• Continental Shelf is the gentlysloping seaward extension of continentalplate.
• Continental Shelf of all oceans togethercover 7.5% of the total area of the oceans.
• The average width of continental shelvesis between 70 – 80 km.
• the Siberian shelf in the Arctic Ocean, thelargest in the world, stretches to 1,500 kmin width.
• The depth of the shelves also varies. Itmay be as shallow as 30 m in some areaswhile in some areas it is as deep as 600 m.
QUESTION 81
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La Nina
This phenomenon is just theopposite of El Niño. In some years,the trade winds can becomeextremely strong and an abnormalaccumulation of cold water canoccur in the central and easternPacific. This event is called a LaNiña.La Niña results in abnormally heavymonsoons in India and SE Asia, wetwinter in Eastern Africa & Australia,and drought in southern UnitedStates & South America.
Q. In which one of the following oceans Diamantine Trench is situated? [2006]
(a) Pacific Ocean
(b) Atlantic Ocean
(c) Indian Ocean
(d) Arctic Ocean
Answer: c
QUESTION 81
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Q. Tides occur in the oceans and seas due to which among the following? [2015 - I]
1. Gravitational force of the Sun
2. Gravitational force of the Moon
3. Centrifugal force of the Earth
Select the correct answer using the code given below.
(a) 1 only
(b) 2 and 3 only
(c) 1 and 3 only
(d) 1, 2 and 3
QUESTION 82
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QUESTION 82
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Tides
• The periodical rise and fall of the sea level,once or twice a day, mainly due to theattraction of the sun and the moon, is calleda tide.
• The moon’s gravitational pull to a greatextent and to a lesser extent the sun’sgravitational pull, are the major causes forthe occurrence of tides.
• Another factor is centrifugal force which actsopposite to gravitational pull of earth.
• Tides occur due to a balance between allthese forces.
Q. Tides occur in the oceans and seas due to which among the following? [2015 - I]
1. Gravitational force of the Sun
2. Gravitational force of the Moon
3. Centrifugal force of the Earth
Select the correct answer using the code given below.
(a) 1 only
(b) 2 and 3 only
(c) 1 and 3 only
(d) 1, 2 and 3
Answer: d
QUESTION 82
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Q. Assertion (A) : During the neap tides, the high tide is lower and the low tide is higher than
usual.
Reason (R) : The neap tide, unlike the spring tide, occurs on the new moon instead of on the
full moon.
Select the appropriate code: [2001]
(a) Both A and R are true and R is the correct explanation of A
(b) Both A and R are true but R is NOT a correct explanation of A
(c) A is true but R is false
(d) A is false but R is true
QUESTION 83
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QUESTION 83
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Types of Tides
• When the sun, the moon and the earth are in a straight line,the height of the tide will be higher.
• These are called spring tides and they occur twice a month,one on full moon period and another during new moonperiod.
Spring Tide
• A tide in which the difference between high and low tide isthe least.
• Normally, there is a seven day interval between the springtides and neap tides.
• At this time the sun and moon are at right angles to eachother and the forces of the sun and moon tend to counteractone another.
Neap Tide
Q. Assertion (A) : During the neap tides, the high tide is lower and the low tide is higher than
usual.
Reason (R) : The neap tide, unlike the spring tide, occurs on the new moon instead of on the
full moon.
Select the appropriate code: [2001]
(a) Both A and R are true and R is the correct explanation of A
(b) Both A and R are true but R is NOT a correct explanation of A
(c) A is true but R is false
(d) A is false but R is true
Answer: c
QUESTION 83
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Q. Consider the following statements: [2000]
1. Tides are of great help in navigation and fishing.
2. High tide enables big ships to enter or leave the harbour safely
3. Tide prevents siltation in the harbours
4. Kandla and Diamond Harbour are tidal ports
Which of these statements are correct?
(a) 1 and 4
(b) 2, 3 and 4
(c) 1, 2 and 3
(d) 1, 2, 3 and 4
QUESTION 84
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QUESTION 84
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Importance of Tides
• Tidal heights are very important, especially harbours near riversand within estuaries having shallow ‘bars’ [Marine Landforms] atthe entrance, which prevent ships and boats from entering intothe harbour.
• High tides help in navigation. They raise the water level close tothe shores. This helps the ships to arrive at the harbour moreeasily.
• Tides generally help in making some of the rivers navigable forocean-going vessels. London and Calcutta [Tidal Ports] havebecome important ports owing to the tidal nature of the mouthsof the Thames and Hooghly respectively.
Navigation
QUESTION 84
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Importance of Tides
Tides are also helpful in desilting the sediments and in removing polluted water from river estuaries.
Desilting
• Tides are used to generate electrical power (in Canada, France, Russia, and China).• A 3 MW tidal power project was constructed at Durgaduani in Sunderbans of West Bengal.
Power Generation
The high tides also help in fishing. Many more fish come closer to the shore during the high tide. This enablesfishermen to get a plentiful catch.
Fishing
Q. Consider the following statements: [2000]
1. Tides are of great help in navigation and fishing.
2. High tide enables big ships to enter or leave the harbour safely
3. Tide prevents siltation in the harbours
4. Kandla and Diamond Harbour are tidal ports
Which of these statements are correct?
(a) 1 and 4
(b) 2, 3 and 4
(c) 1, 2 and 3
(d) 1, 2, 3 and 4
Answer: d
QUESTION 84
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Q. Which one of the following is not a lagoon? [2002]
(a) Ashtamudi lake
(b) Chilka lake
(c) Periyar lake
(d) Pulicat lake
QUESTION 85 (DO IT YOURSELF)
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Q. What is a lagoon?
