Q20. What is precipitation?
Precipitation is any type of water that forms in the Earth's atmosphere and
then drops onto the surface of the Earth.
Q21. What is water cycle?
The process by which water continually changes its form and circulates between
oceans, atmosphere and land is known as the water cycle.
Q22. What are tides and how are they caused?
The rhythmic rise and fall of ocean water twice in a day is called a tide.
strong gravitational pull exerted by the sun and the moon on the earth’s
surface causes the tides.
Q23. Which factors affect the movement of ocean water?
Temperature, density and salinity, storm, earthquake, a volcanic eruption or
underwater landslides, gravitational pull exerted by the sun and the moon on
the earth’s surface.
Q24. Why is our earth like a terrarium?
Our earth is like a terrarium. The same water that existed centuries ago still
exists today. The water used to irrigate a field in Haryana may have flowed
down the Amazon River a hundred years ago.
Q25. Write a short note on waves?
When the water on the surface of the ocean rises and falls alternately, they
are called waves. During a storm, the winds blowing at very
high speed form huge waves. These may cause tremendous destruction.
Q26. What are the factors affecting the height of the waves?
a storm, the winds blowing at very high speed form huge waves. An earthquake, a
volcanic eruption or underwater landslides can shift large amounts of ocean
water. As a result a huge tidal wave called tsunami, that may be as high as
15m., is formed.
Q27. What are spring and neap tides?
water of the earth closer to the moon gets pulled under the influence of the
moon’s gravitational force and causes high tide. During the full moon and new moon
days, the sun, the moon and the earth are in the same line and the tides are
highest. These tides are called spring tides. But when the moon is in its first
and last quarter, the ocean waters get drawn in diagonally opposite directions
by the gravitational pull of sun and earth resulting in low tides. These tides
are called neap tides.
Q28. Why are tides important to us?
important to us because:-
High tides help in navigation.
They raise the water level close to the
shores. This helps the ships to arrive at the harbour more easily.
The high tides also help in fishing. Many
more fish come closer to the shore during the high tide. This enables fishermen
to get a plentiful catch.
The rise and fall of water due to tides is
being used to generate electricity in some places.
Q29. Three-fourth of the earth surface is covered by water. Give
the distribution of water in percentage?
The following table gives the distribution of water in percentage.