14. Movement of ocean water

 NCERT Questions:

1. Multiple choice questions:

(i)  Upward and downward movement of ocean water is known as:

a) Tide

b) Current

c) Wave

d) None of the above

Ans. a) Tide

(ii) Spring tides are caused:

a) As a result of the moon and the Sun pulling the Earth gravitationally in the same direction

b) As result of the Moon and the Sun pulling the Earth gravitationally in the opposite direction

c) Indentation in the coastline

d) None of the above

Ans. a) As a result of the moon and the Sun pulling the Earth gravitationally in the same direction

(Spring Tides: During these moon phases, the solar tide coincides with the lunar tide because the sun and the moon are aligned with Earth and their gravitational forces combined to pull the oceans water in the same direction. These tides are known as spring tides or king tides.)

(iii) The distance between the Earth and the Moon is minimal when the moon is in:

a) Aphelion

b) Perihelion

c) Perigee

d) Apogee

Ans. c) Perigee

(iv) The earth reaches its perihelion in:

a) October

b) September

c) July

d) January

Ans. d) January

2. Answer the following questions in about 30 words:

(i) What are waves?

Ans.

a) Waves are oscillatory movements and water manifested by an alternate rise and fall of the sea surface.

b) Waves are actually the energy, not the water as such, which moves across the ocean surface.

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

d) 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.

e) Waves travel because wind pushes the water body in its course, while gravity pulls the crest of the waves downward.

f) The falling water pushes the format troughs upward and the wave moves to a new position.

g) The actual motion of the water beneath the waves is circular.

(ii) Where do waves in the ocean get their energy from?

Ans.

a) Wind provides energy to the waves

b) Wind causes waves to travel in the ocean and energy is released on shorelines.

c) The motion of the surface Earth seldom affects the stagnant deep bottom water of the oceans.

d) As a wave approaches the beach, it slows down. This is due to the friction occurring between the dynamic water and the sea floor.

e) Waves continue to grow larger as they move and absorb energy from the wind.

f) Most of the waves are caused by the wind driving against water.

g) When a breeze of two knots or less blows over calm water, small ripples form and grows as the wind speed increases until whitecaps appear in the breaking waves.

(iii) What are tides?

Ans.

a) 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.

b) Tides vary in their frequency, direction and movement from place to place and also from time to time.

(iv) How are tides caused?

Ans. Tides are caused by:

a) The moons gravitational pull to a great extent.

b) The sun’s gravitational pull to some extent are the major causes for the occurrence of tides.

c) Another factor is centrifugal force which is the force that acts to counter balance the gravity.

d) Together, the gravitational pull and the centrifugal force are responsible for creating the two major tides or tidal bulges on the Earth.

e) On the side of the earth facing the moon, a tidal bulge occurs, while on the opposite side though the gravitational attraction of the moon is less as it is farther away, the centrifugal force causes tidal bulge on the other side. The tide generating force is the difference between these two forces, i.e., the gravitational attraction and the moon and the centrifugal force.

(v) How are tides related to navigation?

Ans.

a) Since tides are caused by the Earth, Moon, Sun’s positions which are known accurately, the tides can be predicted well in advance.

b) This helps the navigators and fishermen plan their activities.

c) Tidal flows are of great importance in navigation.

d) Tidal heights are very important, especially harbours near rivers and within estuaries having shallow bars at the entrance which prevent ships and ports from entering into the harbour.

e) Kolkata port on Hooghly River is an example for it.

3. Answer the following questions in about 150 words:

(i) How do currents affect the temperature? How does it affect the temperature of coastal areas in the North West Europe?

Ans. Impact of currents on temperature varies depending on whether currents are warm or cold.

a) Cold currents bring cold water into warm water areas. These currents are usually found on the West Coast of the continents, in the low and middle latitudes, true in both hemisphere and on the East Coast in the higher latitudes in the northern hemisphere.

b) 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 hemisphere.

c) In the Northern Hemisphere, they are found on the West Coast of continents in high latitudes.

d) In North West Europe, warm currents exist. They increase the temperature in coastal areas of North West Europe.

(ii) What are the causes of currents?

Ans. Ocean currents are like river flow in oceans. They are caused by two types of forces, namely:

a) The primary forces that initiate the movement of water.

b) Secondary forces that influence the currents to flow.

The forces that influence the current are:

a) Heating by solar energy: Heating by solar energy causes the water to expand. That is why near the equator, the ocean water is about 8 centimetres higher in the level than in the middle latitudes. This causes a very slight gradient and water tends to flow down the slope.

b) Wind: Wind blows on the surface of the ocean water and pushes the water to move. Friction between the wind and the water surface affects the movement of the water body in its course.

c) Gravity: Gravity tends to pull the water down the pile and create gradient variation.

d) Coriolis force: The Coriolis force intervenes and causes the water to move to the right in the northern hemisphere and to the left in the southern hemisphere. These large accumulations of water and the flow around them are called Gyres. These produce large circular currents in all the ocean basins.

Question Bank:

1. Upward and downward movement of ocean water is known as the:

a) Tide

b) Current

c) Wave

d) None of the above

Ans. a) Tide

Tide is the periodical rise and fall of the sea level due to gravitational pull of sun and moon on earth.

2. Spring tides are caused:

a) As result of the moon and the sun pulling the earth gravitationally in the same direction

b) As result of the moon and the sun pulling the earth gravitationally in the opposite direction

c) Indentation in the coastline

d) None of the above

Ans. d) None of the above

When the sun the moon and the earth are in straight line, the height of the tide is higher. These are called spring tides. They occur twice a month.

3. The distance between the earth and the moon is minimal when the moon is in

a) Aphelion

b) Perigee

c) Perihelion

d) Apogee

Ans. b) Perigee

The moon’s orbit around the earth is elliptical. The point of the orbit closest to earth is called perigee, while the point farthest from the earth is known as apogee.

4. The earth reaches its perihelion in:

a) 4^th October

b) 4^th September

c) 4^th July

d) 4^th January

Ans. d) 4^th January

The earth reaches its perihelion position on 4^th of January.

5. The most common tidal pattern, featuring two high tides and two low tides each day is called:

a) Neap tide

b) Mixed tired

c) Semidiurnal tide

d) Diurnal tide

Ans. c) Semidiurnal tide

The most common tidal pattern, featuring two high tides and two low tides each day is called semidiurnal tide.

6. When the tide is channelled between islands or bays and estuaries they are called:

a) Tidal currents

b) Ocean currents

c) Electric currents

d) Waves

Ans. a) Tidal currents

When the tide is channelled between islands or bays and estuaries they are called tidal currents.

7. _______ is the vertical distance from the bottom of trough to the top of a crest of a wave

a) Wave speed

b) Wave height

c) Wavelength

d) Wave frequency

Ans. b) Wave height

Wave height is the vertical distance from the bottom of a trough to the top of a crest of a wave.

8. _______ is the number of waves passing a given point during a second time interval?

a) Wave height

b) Wavelength

c) Wave frequency

d) Wave speed

Ans. c) Wave frequency

Wave frequency is the number of waves passing in a given point during one second time interval.

9. Wave speed is the rate of which the waves moves through the water, is measured in:

a) Knots

b) Miles

c) Kilometres

d) Kilogram

Ans. a) Knots

Wave speed is the rate at which the waves moves through the water, and is measured in knots.

10. When a ______ blows over calm water, small ripples form and grow as the wind speed increases until whitecaps appear in the breaking waves:

a) Breeze of two knots or less

b) Jet stream

c) Ocean current

d) Airplane

Ans. a) Breeze of two knots or less

When a breeze of two knots or less blows over calm water, small ripples forms and grow as the wind speed increases until whitecaps appear in the breaking waves.

11. _______ causes waves to travel in the ocean and the energy is released on shorelines

a) Wind

b) Land

c) Water

d) Soil

Ans. a) Wind

Water particles only travel in a small circle as a wave passes. Wind causes waves to travel in the ocean and the energy is released on shorelines.

12. A current of Atlantic Ocean is the extended part of West Wind Drift

a) Agulhas current

b) Mozambique Current

c) Benguela Current

d) Canary Current

Ans. c) Benguela current

The Benguela Current moves north from the southern Atlantic Ocean around Antarctic Ocean along the west coast of Africa. Accompanying bends, the Benguela current reaches as far as southern Angola; making it extremely difficult to travel southward along the Atlantic Coast. Finally, the Benguela meets the South Equatorial Current.

13. The factor that affects the origin and movement of current is:

a) Magnetic field

b) Human activities

c) Shape of the coast

d) Topography of the continent

Ans. c) Shape of the coast

An ocean current is a continuous, direct movement of ocean water generated by the forces acting upon the water, such as the rotation, wind, temperature, salinity differences and time. Depth, contours, shoreline figurations and interaction with other currents influence currents direction and strength.

14. Great Barrier Reef is in:

a) Antarctic Ocean

b) Australia

c) Austria

d) China

Ans. b) Australia

The Great Barrier Reef is a site of remarkable variety and beauty on the North East coast of Australia. Within this vast expanse is a unique range of ecological communities, habitats and species – all of which make the Great Barrier Reef one of the most complex natural ecosystem in the world.

It contains the world’s largest collection of coral reefs, with 400 types of coral, 1500 species of fish, and 4000 types of molluscs. It also holds great specific scientific interest as the habitat of species such as a du gong (sea cow) and the large green turtle are in the verge of extinction.

15. A wave slows down when it reaches the beach:

a) Due to friction

b) Due to velocity

c) Due to gravity

d) Due to currents

Ans. a) Due to friction

The friction occurs between the dynamic water and the sea floor.

16. Deep water currents constitute ______ of ocean water:

a) 10%

b) 45%

c) 80%

d) 90%

Ans. d) 90%

90% of the ocean water currents are deep water currents. The ocean currents are of two types’ surface currents and deep water currents

17. The shape of the ocean that resembles the English letter ‘S’ is

a) Indian Ocean

b) Pacific Ocean

c) Southern Ocean

d) Atlantic Ocean

Ans. d) Atlantic Ocean

Atlantic Ocean resembles the English letter ‘S’.

18. Coral are mainly confined to the seas and oceans of:

a) Higher latitudes

b) Mid-latitudes

c) Lower latitudes

d) Tropics

Ans. b) Mid-latitudes

Coral are confined to the seas and oceans of mid-latitudes.

19. The dense fog is due to:

a) Intermixing of Labrador current and Gulf Stream

b) Condensation of salt nuclei present in the ocean water

c) Upwelling of waters

d) Warm waters

Ans. a) Intermixing of Labrador Current and Gulf Stream

Dense fog is due to intermixing of cold Labrador Current and warm Gulf Stream water.

20. Which one of the following current is wrongly matched with its ocean of origin?

a) Brazil current Atlantic ocean

b) Kuroshio Current Pacific Ocean

c) West Wind Drift Indian Ocean

d) Benguela Current Pacific Ocean

Ans. d) Benguela current – Pacific Ocean

Benguela Current flows in Atlantic Ocean.

21. Kuroshio Current is the current of:

a) Atlantic Ocean

b) Pacific Ocean

c) Indian Ocean

d) Arctic Ocean

Ans. b) Pacific Ocean

The Kuroshio Current is a north flowing Pacific Ocean current on the west side of the North Pacific Ocean near Japan.

22. Labrador Current is found in:

a) Atlantic Ocean

b) Pacific Ocean

c) Indian Ocean

d) Arctic Ocean

Ans. a) Atlantic Ocean

Labrador Current is a cold current east of Canada.

23. The large accumulation of water and the flow around them is called:

a) Gyres

b) Years

c) Currents

d) Eddies

Ans. a) Gyres

Gyres are any large system of rotating ocean currents with large wind movements. Gyres are caused by the Coriolis force, planetary vortices along with horizontal and vertical friction.

24. In ‘Perigee’

a) Low tides occur

b) High tides occur

c) No tides occur

d) Surface currents occur

Ans. b) High tides occur

High tides occur when the moon’s orbit is closest to the earth it is known as ‘Perigee’ during which high tides occur.

25. Wave speed is measured in

a) Kilometres

b) Knots

c) Miles

d) Shots

Ans. b) Knots

26. Brazilian current is an important current of

a) Indian Ocean

b) Atlantic Ocean

c) Pacific Ocean

d) Arctic Ocean

Ans. b) Atlantic Ocean

Brazilian current is an important current of Atlantic Ocean it is a warm current.

27. Factor which is not responsible for the generation of currents is:

a) Wind

b) Gravity

c) Coriolis force

d) Precipitation

Ans. d) Precipitation

28. The relief features that are the best areas for fishing are:

a) Continental slope

b) Continental shelves

c) Abyssal plains

d) Trench

Ans. b) Continental shelves

Continental shelves are the best relief features for fishing.

29. Corals are made by dead:

a) Organism shells containing calcium dead

b) Organism shells containing silica

c) Accumulation of sediments

d) Organic remains of plants and animals

Ans. b) Organism shells containing calcium dead

Organism shells containing calcium dead deposits.

30. The thermodynamics of the ocean are:

a) Currents

b) Waves

c) tides

d) Salinity

Ans. d) Salinity

31. The current of Atlantic Ocean is:

a) West Wind Drift

b) Gulfstream

c) Equatorial Counter Current

d) Alaska current

Ans. b) Gulfstream

Gulfstream is the current of Atlantic Ocean. It is warm current which bring warm water into cold water areas.

32. The current of Indian Ocean is

a) West Wind Drift

b) Labrador Current

c) California Current

d) Kuroshio Current

Ans. a) West Wind Drift

The West Wind Drift is the current of Indian Ocean. It’s a cold current, which bring cold water into warm water areas.

33. Tides are used to generate:

a) Gravity

b) Energy

c) Minerals

d) Rocks

Ans. b) Energy

Tides are used to generate tidal energy.

34. Wave Crest and trough refers to:

a) Wave size

b) Wavelength

c) The highest and lowest points of wave

d) Wave speed

Ans. c) The highest and lowest points of a wave

35. Tsunamis are the waves caused due to

a) Gravitational pull of the sun

b) Gravitational pull of the moon

c) Due to winds

d) Due to earthquake in the water

Ans. d) Due to underwater earthquake

36. Wave amplitude is:

a) The height of the wave

b) The breath of the wave

c) One half of the wave height

d) Time interval between two successive waves

Ans. c) Wave amplitude is one half of the wave height.

37. The factor that affects the origin and movement of current is:

a) River flow

b) Salinity and density of water

c) Tides prevailing winds

d) Prevailing winds

Ans. b) Salinity and density of water

Salinity and density of water, direction and shape of the coast with added gravitational force decide the origin and movement of currents.

38. Wave slows down when it reaches the beach due to

a) Friction

b) Velocity

c) Gravity

d) Wind direction

Ans. a) Friction

As a wave approaches the beach, it slows down due to the friction occurring between the dynamic water and the sea floor. It is because the depth of water is less than half the wave length of the wave, the wave breaks.

39. Kuroshio Current is the current of:

a) Atlantic Ocean

b) Pacific Ocean

c) Indian Ocean

d) Arctic Ocean

Ans. b) Pacific Ocean

The Kuroshio Current also called the Japan Current is the second strongest current in the world after the Gulf of Stream and it’s famous for its strong and fast flow. It is a strong western boundary current in the western North Pacific Ocean. It begins from the East Coast of Taiwan and flows northwest north world past Japan, where it merges with the Easterly Drift of the North Pacific Current.

40. The surface currents constitute about:

a) 15%

b) 10%

c) 80%

d) 20%

Ans. b) 10%

10% of the ocean currents are surface currents.

1. Define ‘Apogee’.

Ans. The maximum distance between the earth and moon is called apogee. At this time moons gravitational force is limited and the tidal ranges are less than their average heights.

2. Define ‘Perigee’.

Ans. The minimum distance between the earth and moon is called ‘Perigee’ when the moon’s elliptical path is closest to the earth; unusually high and low tides occur.

3. What are waves?

Ans. Waves are actually the energy, not the water that moves across the ocean surface. Wind causes waves to travel in the ocean and the energy is released on shorelines.

4. Where do waves in the ocean get their energy from?

Ans. Waves in the ocean take their energy from the winds.

5. What is a trough?

Ans. The lowermost part of the wave is called the trough.

6. Define Crest.

Ans. The uppermost part of the wave is called the crest.

7. What factors cause the waves to decline?

Ans. The factors that decline waves are:

a) The friction of water on seafloor.

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

7. Where are the largest waves found?

Ans. The largest waves are found in the open ocean.

8. Name the two types of waves.

Ans. The two types of waves are:

a) Transverse waves

b) Longitudinal waves

9. What are the highest and the lowest part of waves called?

Ans. The highest part of the waves is called ‘crest’ and the lowest part of the waves is called ‘through’.

10. When do waves begin to break?

Ans. Waves begin to breakdown when the depth of the water is less than half the wavelength of the waves.

11. What are the things that affect the size of waves?

Ans. The three things that affect the size of waves are:

a) Wind speed

b) Wind duration (how long the wind blows)

c) The distance over water that the wind blows in a single direction

12. Name the important cold current of the Atlantic Ocean.

Ans. Important currents of the Atlantic Ocean are:

a) Labrador Current

b) Canary Current

c) Benguela Current

d) Falkland Current

e) West Wind Drift

13. How are tides caused?

Ans. Tides are caused due to the gravitational force of the moon and the sun.

14. What is gyre?

Ans. A gyre is a large system of rotating ocean currents. Due to Coriolis force the movement of water in the ocean takes an elliptical shape which is known as gyre.

There are five major gyres in the ocean water. The ocean churns up various types of currents. Together, these larger and more permanent currents make up the systems of currents known as gyres.

15. What are tides?

Ans. 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 are called tides.

16. How are tides caused?

Ans. Tides are set to be caused by the gravitational pull of the sun and moon.

17. How are tides related to navigation?

Ans. The main benefit of high tide is that it helps in navigation. When high tides occur, the wave water level rises up this is the time when it is safe for the large ships to enter and leave the harbour. Large ships can easily sale in water when there is high tide.

18. How do currents affect the temperature?

Ans. Ocean currents act like a conveyor belt, transporting warm water and precipitation from the equator towards the poles and cold water from the poles back to the tropics. Thus, ocean currents regulate global climate, helping to counter act the uneven distribution of solar radiation reaching Earth’s surface.

19. How do currents affect the temperature of coastal areas in the North West Europe?

Ans. The North Atlantic drift, carrying warm Equatorial waters northwards, increases temperatures along the coast of North West Europe and helps to keep coastal areas warm throughout the year.

20. What are the causes of currents?

Ans. Mostly currents are caused due to temperature variation, salinity, prevailing winds, Coriolis force and topography of ocean floor.

21. Define tide.

Ans. The continuous rise and fall of water of the oceans due to the gravitational force of moon and sun is known as tide.

22. What is the drift?

Ans. Currents are known as movement of the mass of water in a fairly defined direction over its long distance. Ocean currents are like rivers in the ocean, thousands of kilometres in length and sometimes about 200 kilometre wide. These ocean currents can be cold or warm currents, known as drifts.

23. What are icebergs?

Ans. The drifting blocks of ice in the ocean water are icebergs. These are carved pieces of glaciers. Hence they are formed of compact snow, composed entirely of fresh water, like floating ice cubes. Icebergs are very common near poles.

24. What are the major characteristics of waves?

Ans. The major characteristics of waves are as follows:

Wave Crest and Trough:  The highest and the lowest points of the waves are known as the crest and trough respectively.

Wave height:  It is vertical distance between the bottom of the trough and the top of the Crest.

Wave amplitudes:  It is 1/2 of the wave height.

Wave Period:  It is merely the time interval between the two successive wave Crest and troughs as they pass through a particular point.

Wave Length:  It is the horizontal distance between the two successive crests.

Wave speed:  It is the rate at which the wave moves through the water and is measured in knots.

Wave Frequency:  It is the number of waves passing at a given point during one second time.

25. Name the main types of wind produced waves.

Ans. The major types of wind produced waves can be classified into three categories:

a) Longshore waves: when the waves break against the shore and move parallel to the shore.

b) Undertow wave: is seaward movement of water. It’s a strong seaward bottom current returning of broken waves back out to sea.

c) Rip currents: are localised cheeks of returning water. They typically extend from the shoreline, through the surf zone, and past the line of breaking waves. Rip currents can occur at any beach with breaking waves.

26. Examine the relationship between earthquakes, tsunamis and waves.

Ans. The waves, earthquakes and tsunamis are interrelated phenomena. The earthquake may generate waves as well as tsunamis. Minor earthquakes may generate waves that have low depth and height as major earthquakes may cause tsunamis that may be 20 to 30 metres in height. All the major tsunamis are caused by major earthquakes occurred on the ocean floor.

27. What are tides and how do they form?

Ans. The sequential rise and fall of the ocean water twice in a day is called tied.

a) Spring tide: During the full moon and the new moon time, the sun, the earth and the moon are in a same line and the tide is the highest. This is called spring tide.

b) Neap tide: The tide that occurs every seven days and co insides with the first and the last quarter of the moon. This tide has a small tidal range because the gravitational force of the moon and the sun are perpendicular to each other.

28. Distinguish between the spring tide and neap tide.

Ans.

29. Distinguish between warm ocean currents and cold ocean currents.

Ans.

30. Discuss the importance of tides.

Ans.

a) Tides are the most important element in navigation. High tide causes the ships to enter into narrow harbours.

b) Tides are also helpful in de-silting the sediments and removing polluted water from river or coral reefs.

c) Tides are used to generate electricity.

31. Distinguish between the waves and the currents:

Ans.

32. Describe the movements of Atlantic Ocean surge?

Ans. The currents of the Atlantic Ocean can be defined on the basis of its division in North and South parts.

North Atlantic currents:

North Equatorial current: It flows from the coast of Africa in the east Atlantic to the West Indies in the west parallel to the equator under the influence of the trade winds.

Gulfstream: Is a warm current that flows along the Gulf of Mexico. Near the Halifax, it comes under the influence of the westerlies and reaches the Gulf of St. Lawrence.

Labrador Current: It is a cold current that starts from the Baffin Bay and flows along the coast of Labrador. It joins the Gulfstream in the South and causes into thick fog near the New Found land Islands.

North Atlantic Drift: From the Grand Bank, the Gulf Stream flows eastward across the Atlantic under the influence of the prevailing Westerly Winds. Here, it is known as the North Atlantic drift. Its speed is quite high in the open seas.

Canaries Current: It is an extension of the North Atlantic drift. It flows along the Spain and the Azores (archipelago) and is known as the cold Canary Current. It finally joins the north Equatorial current while completing the circuit in the North Atlantic Ocean.

Southern Atlantic currents:

South Equatorial current: It lies South of the equator and flows almost parallel to it from east to west.

Brazilian current: The South Atlantic current splits into two branches near (Cape de Sao Roque) Brazil. The northern branch joins the northern Equatorial current whereas the southern branch turns southward and flows along the South American coast as the Brazil current. It is a warm current

Falkland current: The Falkland current is a cold current. It flows along the south-eastern coast of South America from south to north.

Benguela current: It is a cold current that flows along the coast of South Africa it finally joins the South Equatorial currents. It also forms South Atlantic Ocean gyre.

33. Describe the movements of the Indian Ocean currents.

Ans. The currents of the Indian Ocean can be divided into two categories:

North Indian Ocean currents and South Indian Ocean currents:

North Indian Ocean currents the basic characteristic of the north Indian Ocean currents lies in their movement in the summer and in the winter month:

Winter conditions; in winter season the North Equatorial Current is under the influence of the North East Monsoon and blows from east to west. This is known as the Northeast Monsoon Drift

During summer, a strong current flow from west to east; this completely obliterates the North Equatorial Current during this season. It is due to the absence of the North East trade winds. There is no scan counter equatorial current at this time of year. Thus, the circulation of water in the northern part of the ocean is clockwise during the summer season.

South Indian Ocean currents the currents in the South Indian Ocean are similar to the South Atlantic Ocean:

South Equatorial current:  like other oceans, Indian Ocean has South Equatorial current flowing parallel to the equator from east to West.

Mozambique current: the South Equatorial current divides itself into two branches on reaching Madagascar. This is a warm current and is known as warm Mozambique current or Agulhas Current. It merges with the West wind drift.

The West Wind drift: This is a cold current that flows from west to east and reaches the southern tip of the west coast of Australia.

West Australian Current: the West Wind Drift divides into two branches, one branch is known as the West Australian Current, which flows along the east coast of Australia. The other branch flows towards the south of Australia, which is known as the West Wind Drift.

34. If there were no ocean currents, what would have happened to the world?

Ans. The oceanic currents deeply affect the physical and economic environment of the areas where they flow. If there were no ocean currents then the following advantages could not be availed

a) Effect on climate: the climate of coast is highly influenced by the type of current, be it a cold current or warm current.

b) Temperature: oceanic currents also regulate the temperature and rainfall. The ocean currents are the major causes of precipitation.

c) Effects on the marine life: ocean currents sweep a large refuge of the ghost, which is food for plankton.

d) Effect on trade: the absence of the ocean current will adversely affect the trade and transport.

35. Give an account of the currents of the Pacific Ocean Currents.

Ans. The currents of the Pacific Ocean can be divided into two categories:

Northern Pacific current and Southern Pacific currents

North Equatorial Currents: It is a warm current. It flows north of the equator from east to west.

South Equatorial Currents: It is also a warm current. It flows south of the equator from east to West.

Kuroshio Current:  It is a warm current. It flows along the coast of Japan.

Oyashio Current:  It is a cold current that flows out from the Arctic pool and merges into the Kuroshio Current of Japan.

North Pacific drift: It is an extension of Kuroshio Current of Japan. The North Pacific drift is a warm current.

California Current: it is a cold current. It flows along the coast of California and Mexico. It is an extension of the North Pacific drift.

Kuril Current: It is a cold current which flows from Bering Strait; it flows south along the coast of Kuril Island.

Humboldt Current:  it is also known as the Peru Current as it flows along the coast of Peru. Humboldt discovered it, thus it is known as the Humboldt Current. It is a cold current. It is the part of Atlantic Drift.

New South Wales Current:  It is also known as the East Australian Current. It is a warm current. It flows south along the east coast of Australia.

36. What are the major factors that lead to the origination of ocean currents?

Ans. The main factors that lead to the origination of currents in the ocean are:

a) Prevailing winds: These winds blow consistently in a particular direction and drag the surface water due to the force of friction. This leads to the formation of ocean currents. Within Tropics, there are Trade Winds blowing from east. They are responsible for North Equatorial and South Equatorial currents; blowing from east to west.

b) Temperature differences column: The temperature differences at the poles and the Equatorial areas make the currents move. The cold water of at the poles that is heavy sinks while the warm light water floats. This causes the warm equatorial water at the tropics to float towards the poles where due to the sinking of heavy water, the water balance is disturbed.

c) Salinity differences: water having high salinity is heavier and it subsides. As a result, light water with less salinity rushes towards the area of high salinity and current is formed. To maintain the balance, and undercurrent of high salinity water moves towards the area of lower salinity.

d) Evaporation the high rate of evaporation at a particular place lowers down the amount of water. To balance the sea level, water from other places comes and takes place of the evaporated water.

e) Rotation of the earth: Due to the rotation of earth, the Coriolis force gets effective in both the hemisphere of the globe. According to the Farrell’s law, the winds move right in the northern hemisphere and left in the southern hemisphere, which causeway new currents; due to the Coriolis force.

f) Shape of the coast: Change of season changes the direction of the flow of the currents. The best example is the current of the North Indian Ocean. The counter Equatorial current is found in winter only and Equatorial in summer only.

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