Page 148 - SST Class 07

The height of tides depends upon the relative electricity. Tidal power stations have been
position of the moon and the sun with respect to set up in UK, Canada, France and Japan.
the earth. During the full moon and the new Ocean Current
moon days, the sun, the moon and the earth are They are streams of water flowing continuously
in the same line resulting in extra high tides. on the ocean’s surface in definite directions. They
These are called spring tides. When the moon is
influence the temperature conditions of the area.
in the first and the last quarter, the sun and the
They may be warm or cold.
moon are at right angles and the water gets
Warm Current : They originate near the equa-
drawn in diagonally opposite directions. This
tor and move towards the poles. The Gulf
results in low tides which are called neap tides.
Stream is a warm current. They bring warm
Tides are useful for navigation, fishing and trade.
temperature over land surface.
High tides help the ships to enter or leave the
Cold Current : They carry water from polar or
harbours easily. Tides help in fishing. During high
higher latitudes to tropical or lower latitudes. For
tides, more fishes come near the shore helping
example, the Labrador Ocean Current. They
the fishermen to get plentiful catch. Tides help to
result in cold temperature over the land surface.
generate electricity. As the seawater gushes in
during a high tide, its energy can be tapped and They provide the best fishing grounds of the
used to generate electricity. India is yet to start world. Some example of these are— seas around
untilising tidal energy. Japan and seas around the eastern coast of
North America.
Importance of Tides
They lead to foggy weather which makes naviga-
g Tides make some rivers navigable for
tion difficult.
ocean-going vessels. During high tide, the
Currents of the Pacific Ocean
depth of water at the mouth of some rivers
increases. This help the ships to reach the 1. In the Northern Hemisphere
ports located on those rivers. The impor- g North Equatorial current (warm)
tance of the Kolkata port on River Hugli and g Japan (Kuroshio) current (warm)
the London port on River Thames is due to
g North Pacific current (warm)
tides.
g California current (cold)
g Tides help to clear the sediments deposited
2. In the Southern Hemisphere
by rivers on their beds and thus prevents
g South Equatorial current (warm)
siltation of harbours.
g East Australian current (warm)
g During high tide, the saline sea water is
stored in low-lying coastal areas. This saline g West Wind Drift (cold)
water is spread out in the fields and used to g Peru current (cold)
make common salt. Currents of the Atlantic Ocean

g The fishing industry is helped by the rhythm 1. In the Northern Hemisphere
of tides. During high tide, fish come near
g North Equatorial current (warm)
the coast. The fishermen mostly sail out to
g Gulf Stream (warm)
the open sea during low tides and return to
g North Atlantic Drift (warm)
the coast with high tides.
g Canary current (cold)
g The energy of the tides is used to generate

Social Science-7 148