Page 131 - SST Class 07

5. days when the earth, the moon
and the sun are in one line : (a) ______________ (b) ______________
6. types of ocean currents : (a) ______________ (b) ______________

E. Answer in one word or phrase :
1. What part of hydrosphere is available in oceans and seas?
2. What is the largest and deepest ocean?
3. Within which circle does the Arctic Ocean lie?
4. What is the name for the rise and fall of waves?
5. In what formation are the earth, the moon and the sun located on the Full Moon?

6. What is a stream of water in the ocean called?
F. Answer the questions in brief :

1. “We have much water on the earth, we can use as much as we want.” Do you support this view?
Why?

2. What makes the water in the oceans and seas saline?
3. What is the importance of tides?
4 What is the hydrosphere?
5. What is a tsunami? How is it caused?
6. What is the difference between a high tide and a spring tide?

G. Answer the questions in detail :
1. Describe the importance of ocean currents.
2. Why is it important to conserve water?
3. Describe the Atlantic Ocean.
4. What factors contribute in the movement of ocean waters?

5. What is a wave? How is it caused?
6. Describe the tsunami which occurred on 26 December, 2004.

1. How can devastation from tsunamis be prevented?
2. Why do we say that ocean currents influence navigation?

Water Cycle
Water is found in three forms—solid, liquid and gaseous. It is a renewable resource which get renewed
continuously through water cycle or hydrological cycle. The water reaches the atmosphere from the
oceans through evaporation in the form of water vapour. Then the process of condensation takes place
which includes the conversion of water vapour back to water due to cooling which leads to precipitation
in the form of rain or snow. This process repeats again and again. This never ending movement of water
is called the water cycle. The amount of water available varies from place to place and from season to
season. But the general pattern is almost the same. However, there are certain human activities which
affect the water cycle. Cutting down of trees, polluting water bodies and wasting water can affect the
water cycle. We must make efforts to conserve this precious resource.
The Hydrosphere
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