Chapter 5 - Ocean Currents
Q 1. Choose the correct option :
(a) In which ocean does the Labrador current flow?
(i) Pacific
(ii) South Atlantic
(iii) North Atlantic
(iv) Indian
Ans: Option (iii) – North Atlantic
(b) Which current out of the following flows in the Indian Ocean?
(i) East Australian Current
(ii) Peru current
(iii) South Polar current
(iv) Somali current
Ans: Option (iv) – Somali current
(c) Which factor out of the following does not affect the region along the coast?
(i) Precipitation
(ii) Temperature
(iii) Land breezes
(iv) Salinity
Ans: Option (iii) – Land breezes
(d) Which of the following occurs in the area where the cold and warm currents meet?
(i) High temperature
(ii) Snow
(iii) Low temperature
(iv) Thick fog
Ans: Option (iv) – Thick fog
(e) Which of these following currents flows from the northern polar region upto Antarctica?
(i) Warm ocean currents
(ii) Surface ocean currents
(iii) Cold ocean currents
(iv) Deep ocean currents
Ans: Option (iv) – Deep ocean currents
Q 2. Examine the given statements and correct the wrong ones.
(a) Ocean currents give specific direction and velocity to the water
Ans: Correct
(b) The deep ocean currents flow with high velocity
Ans: Correct
(c) Generally, surface ocean currents are formed in the equatorial regions.
Ans: Wrong
Correct Statement: Generally, surface ocean currents are formed in the equatorial region as well as the polar region.
(d) Ocean currents hold great importance for human life.
Ans: Correct
(e) The movement of icebergs is not dangerous for water transport.
Ans: Wrong
Correct statement: The movement of icebergs is dangerous for water transport.
(f) Water becomes warm near Brazil due to ocean currents. On the other hand, it becomes cold near African coast.
Ans: Wrong
Correct statement: Water becomes warm near Brazil due to ocean currents. Similarly, it also becomes warm near the African coast.
Q 3. Explain the effect of –
(a) Warm ocean currents on climate
Ans:
(i) The amount of precipitation increases in the coastal region along with the warm ocean currents.
(ii) Similarly, the temperature increases in the coastal region along with the warm ocean currents.
(b) Cold ocean currents on the movement of icebergs
Ans:
(i) Due to cold ocean currents, icebergs are moved away from the polar regions.
(ii) These icebergs come along the marine routes and prove hazardous to the ships.
(c) The shape of the coast line on ocean currents
Ans:
(i) The extended parts of the coastline act as an obstacle for ocean currents.
(ii) The extended parts of the coastline alter the direction and velocity of ocean currents.
(d) Meeting of warm and cold ocean currents
Ans:
(i) Dense fog is found at the meeting point of warm and cold ocean currents. Algae, plankton, etc. grow on a large scale in these areas.
(ii) Fish come to these areas on a large scale and breed. Therefore, extensive fishing grounds are found in areas where warm and cold ocean currents meet.
(e) The transportational capacity of ocean currents
Ans:
(i) The transportation capacity of ocean currents alters the amount of precipitation and temperature in the coastal regions along with which they flow.
(ii) The transportation capacity of ocean currents leads to the transfer of warm water to the bottom from the surface and cold water to the surface from the bottom.
(f) Deep ocean currents
Ans:
(i) Deep ocean currents lead to the transfer of warm water to the bottom from the surface and cold water to the surface from the bottom.
(ii) Deep ocean currents thus lead to the redistribution of seawater.
Q 4. Look at the map of ocean currents and answer the following :
(a) How does the Humboldt current affect the climate of the South American coast?
Ans: Humboldt current is a cold ocean current and so it decreases the amount of precipitation and temperature on the western coastal region of South America.
(b) In which oceans are counter equatorial currents not observed and why?
Ans: Counter equatorial currents are not observed in the Arctic Ocean and Southern Ocean. These oceans are located near the polar regions. Therefore, the effects of trade winds are found to be less in these oceans. Therefore, counter equatorial currents are not observed in these oceans.
(c) Which currents are absent in northern part of the Indian Ocean and why?
Ans: Cold currents are absent in the northern part of the Indian Ocean. The northern part of the Indian Ocean is included in the temperate zone. So cold currents are absent in the northern part of the Indian Ocean.
(d) In which regions do the cold and warm ocean currents meet?
Ans: The cold and warm ocean currents meet in the following regions:
(i) North Atlantic Ocean (cold Labrador current and warm Gulf stream current)
(ii) North Pacific Ocean (cold Oyashio current and warm Kurishio current)
(iii) South Atlantic Ocean (cold Falkland current and warm Brazil current)
(iv) South Pacific Ocean (cold South Polar current and warm East Australian current)
(v) Indian Ocean (cold South Polar current and Agulhas Current)
Q 5. Answer the following questions:
(a) What are the reasons responsible for the formation of deep ocean currents?
Ans:
(i) The temperature varies in various parts of the ocean.
(ii) Similarly, the density of water in various parts of the ocean is also found to be different.
(iii) The difference in temperature and density of seawater leads to its circulation, and the deep ocean currents are formed. This circulation is known as thermohaline circulation.
(iv) Thus, the difference in temperature and density of water in various parts of the ocean is responsible for the formation of deep ocean currents.
(b) What is the reason behind the dynamics of the ocean water?
Ans: Planetary winds are the reason behind the dynamics of the ocean currents.
(c) How do winds give direction to the ocean currents?
Ans: Winds give clockwise direction to the ocean currents in the northern hemisphere and anti-clockwise direction to the ocean currents in the southern hemisphere.
(d) Why do the ports in the eastern coast of Canada freeze in winter?
Ans:
(i) A Labrador cold current flows along the eastern coast of Canada.
(ii) Due to the Labrador cold current, the temperature of sea water near the eastern coast of Canada decreases.
(iii) Due to the fall in temperature, the sea water along the eastern coast of Canada starts freezing.
(iv) As a result, the ports on the eastern coast of Canada freeze in winter.