Chapter 5 – Ocean Currents
Maharashtra Board – Standard 8 Geography
Q. 1. Choose the correct option:
(a) In which ocean does the Labrador current flow?
(b) Which current out of the following flows in the Indian Ocean?
(c) Which factor out of the following does not affect the region along the coast?
(d) Which of the following occurs in the area where the cold and warm currents meet?
(e) Which of these following currents flows from the northern polar region up to Antarctica?
Q. 2. Examine the given statements and correct the wrong ones.
(a) Ocean currents give specific direction and velocity to the water.
(b) The deep ocean currents flow with high velocity.
(c) Generally, surface ocean currents are formed in the equatorial regions.
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.
(e) The movement of icebergs is not dangerous for water transport.
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 the African coast.
Q. 3. Explain the effect of –
(a) Warm ocean currents on climate
- The amount of precipitation increases in the coastal regions along which warm ocean currents flow.
- The temperature also increases in the coastal regions along which warm ocean currents flow.
(b) Cold ocean currents on the movement of icebergs
- Due to cold ocean currents, icebergs are moved away from the polar regions.
- These icebergs may come along marine routes and prove hazardous to ships.
(c) The shape of the coastline on ocean currents
- The extended parts of the coastline act as obstacles to ocean currents.
- The shape of the coastline can alter the direction and velocity of ocean currents.
(d) Meeting of warm and cold ocean currents
- Dense fog is found at the meeting point of warm and cold ocean currents.
- Algae, plankton and other fish food grow on a large scale in these areas.
- Fish come to these areas in large numbers and breed.
- Therefore, extensive fishing grounds are found where warm and cold ocean currents meet.
(e) The transportational capacity of ocean currents
- The transportational capacity of ocean currents affects the amount of precipitation and temperature in the coastal regions along which they flow.
- Ocean currents also transfer warm water from the surface to the deeper parts and cold water from the deeper parts towards the surface.
(f) Deep ocean currents
- Deep ocean currents transfer warm water from the surface to the deeper parts and cold water from the deeper parts towards the surface.
- Thus, deep ocean currents help in the redistribution of seawater.
Q. 4. Look at the map of ocean currents and answer the following:
World Ocean Currents
(a) How does the Humboldt current affect the climate of the South American coast?
(b) In which oceans are counter equatorial currents not observed and why?
(c) Which currents are absent in the northern part of the Indian Ocean and why?
(d) In which regions do the cold and warm ocean currents meet?
- North Atlantic Ocean – Cold Labrador Current and warm Gulf Stream Current.
- North Pacific Ocean – Cold Oyashio Current and warm Kuroshio Current.
- South Atlantic Ocean – Cold Falkland Current and warm Brazil Current.
- South Pacific Ocean – Cold South Polar Current and warm East Australian Current.
- Indian Ocean – Cold South Polar Current and warm Agulhas Current.
Q. 5. Answer the following questions:
(a) What are the reasons responsible for the formation of deep ocean currents?
- The temperature varies in different parts of the ocean.
- The density of seawater also differs in different parts of the ocean.
- The differences in temperature and density of seawater lead to its circulation and the formation of deep ocean currents.
- This circulation is known as thermohaline circulation.
- Thus, differences in the temperature and density of seawater are responsible for the formation of deep ocean currents.
(b) What is the reason behind the dynamics of the ocean water?
(c) How do winds give direction to the ocean currents?
(d) Why do the ports on the eastern coast of Canada freeze in winter?
- The cold Labrador Current flows along the eastern coast of Canada.
- Due to the Labrador Current, the temperature of seawater near the eastern coast of Canada decreases.
- Due to the fall in temperature, the seawater along the eastern coast of Canada starts freezing.
- As a result, the ports on the eastern coast of Canada freeze in winter.
Quick Revision – Important Points
- Labrador Current: North Atlantic Ocean
- Somali Current: Indian Ocean
- Humboldt Current: Cold current along the western coast of South America
- Gulf Stream: Warm current in the North Atlantic Ocean
- Oyashio Current: Cold current in the North Pacific Ocean
- Kuroshio Current: Warm current in the North Pacific Ocean
- Warm + Cold currents meet: Thick fog and rich fishing grounds are commonly found.
- Deep ocean currents: Mainly associated with differences in temperature and density of seawater.
- Thermohaline circulation: Circulation caused by differences in temperature and density of seawater.
- Eastern coast of Canada: Affected by the cold Labrador Current.