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# GS Geography Quiz for IAS Prelims – Movements of Ocean Water

Apr 11, 2017 16:04 IST

Geography is technical in its orientation and hence only the candidates having a widespread understanding of the subject can answer all the questions of geography for the IAS Prelims Exam. Geography is so vast in its syllabus that it covers the most part of the General Studies for the IAS Prelims Exam.

UPSC IAS Prelims Exam 2017 : GS Geography Study Material

The IAS aspirants cannot overlook the geography portion because there are various aspects of geography which enormously helps in the overall General Studies Preparations. So, it’s advisable to prepare geography from standard sources starting with NCERTS.

1. Consider the following statements regarding the motion of waves and water molecules on the sea surface:

1) Water particles only travel in a small circle as a wave passes.

2) When the depth of water is less than half the wavelength of the wave, the wave breaks.

3) The largest waves are found in enclosed sea.

4) Most of the waves are caused by the wind driving with the water.

Which of the above statements is true?

a. 1 and 2
b. 3 and 2
c. 2 and 4
d. 3 and 4

Explanation:

Waves are actually the energy, not the water as such, which moves across the ocean surface. Water particles only travel in a small circle as a wave passes. The Wind provides energy to the waves. The Wind causes waves to travel in the ocean and the energy is released on shorelines. The motion of the surface water seldom affects the stagnant deep bottom water of the oceans.

As a wave approaches the beach, it slows down. This is due to the friction occurring between the dynamic water and the sea floor and when the depth of water is less than half the wavelength of the wave, the wave breaks. The largest waves are found in the open oceans. Waves continue to grow larger as they move and absorb energy from the wind.

Most of the waves are caused by the wind driving against water. When a breeze of two knots or less blows over calm water, small ripples form and grow as the wind speed increases until white caps appear in the breaking waves.

UPSC IAS Prelims Exam 2017 : the oceans

2. Which of the following factors influence the movement of ocean water?

1) Temperature
2) Salinity of Ocean
3) Density of Ocean Water
4) Wind System
5) Coriolis Force

Choose the correct codes:

a. 1,2 and 3
b. 2 and 3
c. 1,2,3 and 5
d. All of the above

Explanation:

The ocean water is dynamic. Its physical characteristics like temperature, salinity, density and the external forces like of the sun, the moon and the winds influence the movement of ocean water. The horizontal and vertical motions are common in ocean water bodies. The horizontal motion refers to the ocean currents and waves. The vertical motion refers to tides.

3. The wave’s size and shape reveal the origin the wave. Consider the following correlations in this regard:

1) Slow and steady waves are fairly young ones and are probably formed by local wind.

2) Steep waves originate from faraway places, possibly from another hemisphere.

Which of the above statements is true?

a. Only 1
b. Only 2
c. Both 1 and 2
d. Neither 1 nor 2

Explanation:

A wave’s size and shape reveal its origin. Steep waves are fairly young ones and are probably formed by local wind. Slow and steady waves originate from faraway places, possibly from another hemisphere. The maximum wave height is determined by the strength of the wind, i.e. how long it blows and the area over which it blows in a single direction.

Waves travel because the wind pushes the water body in its course while gravity pulls the crests of the waves downward. The falling water pushes the former troughs upward, and the wave moves to a new position.

The actual motion of the water beneath the waves is circular. It indicates that things are carried up and forward as the wave approaches, and down and back as it passes.

IAS Prelims Questions on Oceanography

4. Tides and surges are the two different types of movement of ocean water. Consider the following statements in this regard:

1) Movement of water caused by meteorological effects is called surges.

2) The periodical rise and fall of the sea level mainly due to the attraction of the sun and the moon is called a tide.

3) Surges are also regular like tides.

Which of the above statements is true?

a. Only 1
b. 1 and 2
c. Only 2
d. Only 3

Explanation:

The periodical rise and fall of the sea level, once or twice a day, mainly due to the attraction of the sun and the moon, is called a tide. Movement of water caused by meteorological effects (winds and atmospheric pressure changes) are called surges. Surges are not regular like tides. The study of tides is very complex, spatially and temporally, as it has great variations in frequency, magnitude and height.

The moon’s gravitational pull to a great extent and to a lesser extent the sun’s gravitational pull, are the major causes for the occurrence of tides. Another factor is the centrifugal force, which is the force that acts to counterbalance the gravity.

5. Consider the following statements regarding the characteristics of tide-generating forces:

1) The tidal bulges on wide continental shelves have the greater height.

2) The shape of bays and estuaries along a coastline can also magnify the intensity of tides.

3) When tidal bulges hit the mid-oceanic islands they become low.

Which of the above statements is true?

a. Only 1
b. 1 and 2
c. Only 2
d. 1, 2 and 3

Explanation:

The ‘tide-generating’ force is the difference between these two forces; i.e. the gravitational attraction of the moon and the centrifugal force. On the surface of the earth, nearest the moon, pull or the attractive force of the moon is greater than the centrifugal force, and so there is a net force causing a bulge towards the moon.

On the opposite side of the earth, the attractive force is less, as it is farther away from the moon, the centrifugal force is dominant. Hence, there is a net force away from the moon. It creates the second bulge away from the moon.

On the surface of the earth, the horizontal tide-generating forces are more important than the vertical forces in generating the tidal bulges. The tidal bulges on wide continental shelves have a greater height. When tidal bulges hit the mid-oceanic islands they become low.

The shape of bays and estuaries along a coastline can also magnify the intensity of tides. Funnel-shaped bays greatly change tidal magnitudes. When the tide is channelled between islands or into bays and estuaries they are called tidal currents.

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6. Which of the following is not the relevant use of tidal movement?

a. Tidal flows are of great importance in navigation.
b. Tides help in the development of coral reefs.
c. Tides are also helpful in desilting the sediments and in removing polluted water from river estuaries.
d. Tides are used to generate electrical power.

Explanation:

Tides are caused by the earth, moon and sun positions which are known accurately and hence the tides can be predicted well in advance. This helps the navigators and fishermen plan their activities. Tidal flows are of great importance in navigation.

Tidal heights are very important, especially harbours near rivers and within estuaries having shallow ‘bars’ at the entrance, which prevent ships and boats from entering into the harbour. Tides are also helpful in desilting the sediments and in removing polluted water from river estuaries. Tides are used to generate electrical power especially in Canada, France, Russia, and China.

7. Consider the following types of tides based on their frequency of occurrence and their height:

1) In Diurnal tide, there is only one high tide and one low tide during each day.

2) Mixed tides generally occur along the west coast of South-East Asia.

3) In Semi-diurnal tide, successive high or low tides of the same height occur.

Which of the above statements is true?

a. Only 1
b. 1 and 3
c. Only 2
d. 1, 2 and 3

Explanation:

Tides vary in their frequency, direction and movement from place to place and also from time to time. Tides may be grouped into various types based on their frequency of occurrence in one day or 24 hours or based on their height.

Tides based on Frequency Semidiurnal tide: The most common tidal pattern, featuring two high tides and two low tides each day. The successive high or low tides are approximate of the same height.

Diurnal tide: There is only one high tide and one low tide during each day. The successive high and low tides are approximate of the same height.

Mixed tide: Tides having variations in height are known as mixed tides. These tides generally occur along the west coast of North America and on many islands of the Pacific Ocean.

Tides based on the Sun, Moon and the Earth Positions: The height of rising water (high tide) varies appreciably depending upon the position of sun and moon with respect to the earth.

UPSC IAS Study Material for Civil Services Prelims 2017

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