Class Notes
Water
Chapter - 7 (Geography)
Chapter
7 (geography) Water
A.
Tick the correct answer.
1.
The
total amount of freshwater present on earth is about. – a) 3 per cent
2.
The
upper part of the sea wave is called. – b) crest
3.
What
is the main cause for the occurrence of tides? – c)
gravitational pull
4.
Which
of the following is not an important causes for the occurrence of ocean
currents?- b) Gravitational Pull
5.
Which
of the following is a cold current? – d) Peru
current.
B.
Write True or False.
1.
True
2.
True
3.
False
4.
False
C.
Match the columns.
1.
Mozambique
current d) Indian
Ocean
2.
Beguela
current a) Atlantic
Ocean
3.
California
current b) Pacific ocean
4. Broad current c) Drift
D.
Distinguish between crest and trough, waves and
tides, spring and neap tides, current and drift.
|
Crest |
Trough |
|
The highest surface
of a wave is called the crest |
The lowest
surface of a wave is called tides |
|
|
|
|
Waves |
Tides |
|
Waves are formed in
the oceans or seas when the wind and water influences interact with each
other. |
The
alternative rise and fall in the level of sea water is called tides. |
|
|
|
|
Spring
tides |
Neap
tides |
|
When the moon is
either new or full and the sun, the moon and the earth are in the same
position or line then spring tides occur. |
When the sun
and moon are at the rights angles to
the earth then neap tides occurs. |
|
|
|
|
Current |
Drift |
|
The movement of ocean
water in the form of a stream in a definite direction on the ocean surface is
called an ocean current. |
The forward
movement of surface water of the ocean under the influence of prevailing
winds is called drifts. |
E.
Give short answers for the following
questions.
1.
Describe the general distribution of
salinity in the ocean.
Ans: The general
distribution of salinity in the ocean is that estimately every 1000g of ocean
water has 35g of dissolved salt. Thus, the average salinity is 35 per thousand.
2.
How do ocean current influence climate
in the coastal areas?
Ans: Ocean currents
influence the distribution of temperature over the globe. The warm and the cold
currents increases or decreases the temperature of the coastal areas.
3.
Name the main currents of the Pacific
Ocean?
Ans: The main
current of the Pacific Ocean are:-
i.
Northern
Hemisphere
ii.
Southern
Hemisphere.
4.
What is Tsunami? How does it affect life
in the coastal areas?
Ans: Tsunami is
Japanese word, which means harbor wave. “Tsu” stands for harbor and “nami”
stand for wave.
In the coastal
areas, a tsunami may appear as a huge wall of water coming towards the coast.
With its tremendous energy, the fast moving waves can crush houses and other
structures in the coastal areas.
F.
Give long answer for the following
questions.
1.
Explain the working of the hydrological
cycle with the help of a neatly labeled diagram.
Ans:- Water is
continuously moving from the earths’ surface into the atmosphere through
evaporation in the form of water vapour and due to the loss of heat in the
atmosphere, the process of condensation takes places. Thus, water vapour is
converted backed into water drops. This leads to precipitation in the form of
rain, snow or sleet. This never ending movement of water is called hydrological
cycle or water cycle.
Diagram:-
2.
What are the causes for the occurrence
of tides and currents?
Ans: The causes for
the occurrences of tides and currents can be the gravitational pull of the moon
and the sun on the surface of the earth.
3.
What do you know about the importance of
Tides?
Ans: The importance
of Tides are:-
i.
Tides
make some rivers navigable for ocean-going vessels during the high tides.
ii.
It
helps to clear the sediment deposited by rivers on their beds.
iii.
During
high tide, the saline sea water is stored in low-lying coastal areas.
iv.
The
fishing industry is helped by the rhythm of tides.
v.
The
energy of tides is used to generate electricity.
4.
Write about the main effects of ocean
currents. Give example where ever possible.
Ans:
i.
The
warm and the cold currents increase or decrease the temperature of the coastal
areas.
ii.
Warm
current increase the moisture-bearing capacity of the wind.
iii.
Mixing
of cold and warm currents causes dense fog which hampers navigation.
iv.
Ocean
currents help in navigation.
v.
The
fishing ground of the world are- Newfoundland and Japan are rich in Fish.
5.
Why is the ocean water salty?
Ans: The ocean
water is salty because of the presence of a large amount of dissolved salt. Where
most of it is sodium chloride or common salt.
6.
How do tide helps in trade and fishing?
Ans: Tides makes
some river navigable for ocean-going vessels during high tides, so that the
depth of water at the mouth of some rivers increases. This helps the ships to reach
the ports located on those rivers.
The fishing
industry is helped by the rhythm of tides. Since during high tides, fish come
near the coast and make it easy for the fisherman.
7.
In the coastal areas, the tsunami
appears as a huge wall of water- Explain
Ans: In the coastal areas, the tsunami
appears as a huge wall of water since tsunami travels at speed of about 500 to
1000km per hour. With its tremendous energy, the fast moving waves can crush
the houses and other structures in the coastal areas. Even large object such as
ships can be pushed several kilometers inland. Most of the deaths caused by a
tsunami are due to drowning.
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