The Class 8 is an important year in a student’s life and Maharashtra State Board Social Science Grography is one of the subjects that require dedication, hard work, and practice. It’s a subject where you can score well if you are well-versed with the concepts, remember the important formulas and solving methods, and have done an ample amount of practice. Worry not! Home Revise is here to make your Class 8 journey even easier. It’s essential for students to have the right study material and notes to prepare for their board examinations, and through Home Revise, you can cover all the fundamental topics in the subject and the complete Maharashtra State Board Class 8 Social Science Grography Book syllabus.
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
(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
(c) Which factor out of the following does not affect the region along the coast?
(i) Precipitation
(ii) Temperature
(iii) Land breezes
(iv) Salinity
(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
(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
Answer a: (ii) South Atlantic
Answer b: (iv) Somali current
Answer c: (iv) Salinity
Answer d: (iv) Thick fog
Answer e: (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
(b) The deep ocean currents flow with high velocity
(c) Generally, surface ocean currents are formed in the equatorial regions.
(d) Ocean currents hold great importance for human life.
(e) The movement of icebergs is not 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.
Answer a: The statement is correct.
Answer b: The statement is wrong. The difference in temperatures of various parts of the ocean is the major reason behind the deep-sea currents. Warm water has lower salinity and density. Such water comes to the surface of the sea. Cold water with high density goes down. This movement causes the deep sea water currents.
Answer c: The statement is wrong. Surface ocean currents form in both Polar regions as well as equatorial regions.
Answer d: The statement is true.
Answer e: The statement is wrong. The movement of icebergs is potentially dangerous, as it may hinder or hit the water vehicles.
Answer f: The statement is correct.
Q 3. Explain the effect of –
(a) Warm ocean currents on climate
(b) Cold ocean currents on the movement of icebergs
(c) The shape of the coast line on ocean currents
(d) Meeting of warm and cold ocean currents
(e) The transportational capacity of ocean currents
(f) Deep ocean currents
Answer a: Ocean currents especially affect the climate of the regions having proximity to the sea. In cold regions where warm ocean currents flow, climate becomes warmer. In some regions, the amount of precipitation increases. For example, the warm ocean currents flowing near Western Europe, Southern Alaska, and Japanese coast, reduce the intensity of the winters there and make them warmer. As a result, these ports do not freeze in winters.
Answer b: At places where the cold and the warm currents meet, thick fog is formed. Such fogs create problems for transportation. The warm Gulf Stream and the cold Labrador currents meet near Newfoundland island. This leads to dense fog. Owing to the cold currents, icebergs are carried away from the polar areas. If such icebergs come along the marine routes, they are hazardous to the ships.
Answer c: Longshore currents are generated when a train of waves reach the coastline and release bursts of energy. The speed at which waves approach the shore depends on sea floor and shoreline features and the depth of the water. As a result, the wave tends to bend and conform to the general shape of the coastline.
Answer d: Areas where warm and cold currents meet tend to have regular foggy conditions, as the overlying warm and cold air come in contact with each other. They also tend to have high biological productivity, because plankton growth is encouraged by the mixing of warm and cold currents.
Answer e: The ocean currents are very important, with respect to the water transport. If the transportation is done according to the flow of ocean currents, the speed of the ships increase and the fuel is saved too.
Answer f: Water currents beyond the depth of 500 metres are known as deep water/ocean currents. These currents are formed due to the differences in temperature and density of the water in different parts of the ocean. This is known as thermohaline circulation. These currents flow till the sea-bed of the ocean. They flow like rivers continuously below the surface of the sea.
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?
(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?
Answer a: The Humboldt Current, is an ocean current that flows along the western coast of South America, affecting the water and air temperatures of coastal Chile and Peru. It is one of the largest ocean currents in the world, bringing cold water north from the South Pacific for thousands of kilometers before it dissipates in the warmer waters around the equator.
Answer b: Counter Equatorial Currents noted near the equator, an eastward flow of oceanic water in opposition to and flanked by the westward equatorial currents of the Atlantic, Pacific, and Indian oceans. The counter currents shift south during the northern winter and north during the summer.
Answer c: The cold currents are absent in the northern part of the Indian Ocean. The currents in the northern portion of the Indian Ocean change their direction from season to season in response to the seasonal rhythm of the monsoons. The effect of winds is comparatively more pronounced in the Indian Ocean.
Answer d: At places where the cold and the warm currents meet, thick fog is formed. Such fogs create problems for transportation. The warm Gulf Stream and the cold Labrador currents meet near Newfoundland island. This leads to dense fog.
Q5. Answer the following questions:
(a) What are the reasons 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 in the eastern coast of Canada freeze in winter?
Answer a: Water currents beyond the depth of 500 metres are known as deep water/ocean currents. These currents are formed due to the differences in temperature and density of the water in different parts of the ocean. This is known as thermohaline circulation. These currents flow till the sea-bed of the ocean. They flow like rivers continuously below the surface of the sea. The difference in temperatures of various parts of the ocean is the major reason behind the deep-sea currents. Warm water has lower salinity and density. Such water comes to the surface of the sea. Cold water with high density goes down. This movement causes the deep sea water currents.
Answer b: Ocean currents can be generated by wind, density differences in water masses caused by temperature and salinity variations, gravity, and events such as earthquakes. Currents are cohesive streams of seawater that circulate through the ocean.
Answer c: Trade winds are primarily responsible for change in direction of ocean currents. Wind creates waves that occur on the free surface of bodies of water. These waves are generated by blowing wind over the water surface. Winds push the water on top of ocean currents &causes them to deflect. This is how wind gives direction to ocean current.
Answer d: The ports in the Eastern coast of Canada freeze in winter because as we know that Canada and other parts of it are located near Northern poles where the temperature is low and everything freezes.