9th geography chapter4

 

Answer the following in brief:

1. What do you mean by the term Hydrosphere?

1.The 'Hydrosphere' is the watery part of the earth. 

2.This consists of water in various forms found on the earth

3.About 97% of Earth's water is sea water,the remaining 3% is fresh water

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 2. What is hydrological cycle? 

1.The Earth's water is not static. 

2.It is always in motion. 

3.Water changes its form (Ice, Water and Water Vapour) constantly is "Hydrological Cycle"

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 3. Mention the various relief features of ocean floor. 

(i)Continental shelf

(ii) Continental slope

(iii) Continental rise

(iv) Deep sea plain or Abyssal plain

(v) Oceanic deep

(vi) Oceanic ridge

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 4. What are the factors that generate the ocean currents? 

1.Earth's rotation
2.Salinity of ocean water
3.Differences in temperature
4.Prevailing winds

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5. Write a brief note on sea waves. 

(i)Of all the movements of the oceans, sea waves are considered to be the strongest.

(ii) Sea waves are ripples on water caused when winds blow over the sea.

(iii) The height of these waves depends on the speed of wind, its duration and the direction from which they blow.

(iv) Sometimes waves are also caused by vibrations felt on the ocean floor.

(v) Such waves are quite destructive and called Tsunami.

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Give reasons for the following:

 1. The northern hemisphere and the southern hemisphere are called land and water hemispheres respectively. 

(i)The Northern Hemisphere holds 61% of land.

(ii) The Southern Hemisphere holds 81% of water.

(iii) It is because of this pattern of land and water distribution, the Northern hemisphere is called as the land hemisphere and the Southern hemisphere is called as the water hemisphere.

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 2. Continental shelf provides good fishing ground.

(i)The continental shelf is shallower, thus enables sunlight to penetrate through the water.

(ii) This encourages abundant growth of grass, sea weeds and plankton.

(iii) Hence these zones become the richest fishing grounds in the world.

(iv) Example: The Grand Banks of Newfoundland.

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Distinguish the following:

1. Spring tide and Neap tide. 

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 2. Abyssal plains and Ocean deeps. 

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Answer in a paragraph:

 1.Write a note on continental shelf and continental slope. 

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 2.What do you mean by ocean currents? Explain its types. 

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3.Explain the influences of the marine resources on mankind.

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