Page 146 - SST Class 07

are caused due to difference in temperature,
salinity and prevailing winds.
w March 22nd is celebrated as World Water Day.
Think how you would like to celebrate it in your Wave
school. How would you use this day to create When the water on the surface of the ocean rises
awareness about conservation of water? and falls alternately, they are called waves. They
w Our earth is called the ‘watery planet’. 71% of the are formed when winds scrape the ocean floor.
earth’s surface is covered with water while only When we throw a ball in the ocean, it gets
29% is the land area. The water is found in oceans,
washed back to the shore by the waves. The
seas, lakes, rivers, etc. The domains of water is
stronger the wind blows, the bigger the wave
called the hydrosphere.
becomes. During a storm, the wind blows at a
MOVEMENT OF OCEAN WATER very high speed forming huge waves. These may
Oceans are very large water bodies surrounding cause tremendous destruction. The following can
the continents and contain more than 70% of the shift large amount of ocean water :
total quantity of water available on the earth’s g An earthquake
surface. There are four oceans on the surface of g A volcanic eruption
the earth. These are— the Pacific Ocean, the g Underwater landslide
Atlantic Ocean, the Indian Ocean and the Arctic
Due to the above, a huge tidal wave called
Ocean. These oceans have a moderating effect
tsunami is formed. It may be as high as 15
on the climate of coastal areas. The ocean waters
meters. The highest tsunami ever measured was
are never still. Their movement can be categories
150 m high. These waves travel at a speed of
as waves, tides and currents. These movements
700 km/h.

ARCTIC OCEAN
ARCTIC OCEAN
BEAUFORT
SEA
Arctic Circle
NORTH Okhotse
R. Makenzit
SEA R. Volga L. Baykal Sea
Great Lakes R. Rhine ARAL SEA L. Balkhash
LABRADOR SEA
NORTH
PACIFIC R. NORTH R. Yangtze NORTH
OCEAN MISSISSIPI ATLANTIC MEDITERRANEAN R. Indus PACIFIC
SEA
OCEAN
OCEAN
Tropic of Cancer R. Ganga
L. Chad
R. Zalre
Equator L. Victoria
R. Amazon
INDIAN OCEAN
L. Titicaca
L. Tanganyika
Tropic of Capricorn
R. Eyre
R. Parana R. Darting
SOUTH SOUTH Rauray
PACIFIC ATLANTIC
OCEAN
OCEAN
SOUTHERN OCEAN
Antarctic Circle
ANTARCTICA
Major Water Bodies
Social Science-7 146