3. Water on the Earth
49
3
THE WATER CYCLE
Water on the Earth is constantly
moving due to solar radiation
and gravity: evaporation causes
water to rise to the atmosphere
where it condenses and then
falls again in the form of
precipitation
(rain, snow, hail
1
).
Water then moves over the
Earth’s surface (rivers, streams)
or areas underground, until it
reaches lakes and the sea. This
perpetual movement, called the
water cycle,
is the key to life on
our planet.
evaporation
condensation
condensation
evaporation
precipitation
Analyse
1.
Read the text and look at the illustration above.
Answer the following questions.
a)
What is the water cycle?
b)
In what forms is fresh water found on Earth?
c)
Where does fresh water on our planet come from?
d)
What are the forms of precipitation?
e)
Write a definition of a river and a lake. Say if the water
in each is fresh water or salt water.
2.
Look at the bar charts on page 48. Answer the
questions.
a)
Is there more salt water or fresh water on Earth?
b)
What percentage of surface water is made up of
fresh water?
c)
Where is the major concentration of fresh water on
the surface of the planet?
Create
3.
Find out why sea water is salty. Write your
conclusions in your notebook.
