Q1. What do you mean by water cycle?
Ans: The process by which water continually changes its form and circulates between oceans, atmosphere and land is known as the water cycle.
Q2. Explain the movement of ocean water.
Ans: The movements that occur in oceans can be broadly categorised as: waves, tides and currents.
When the water on the surface of the ocean rises and falls alternately, they are called waves.
The rhythmic rise and fall of ocean water twice in a day is called a tide.
Ocean currents are streams of water flowing constantly on the ocean surface in definite directions. The ocean currents may be warm or cold.
Q3. Write a short note on Tsunami.
Ans: During a storm, the winds blowing at very high speed form huge waves. These may cause tremendous destruction. An earthquake, a volcanic eruption or underwater landslides can shift large amounts of ocean water. As a result a huge tidal wave called tsunami.
The tsunami of 2004 caused wide spread damage in the coastal areas of India.
Q4. What are the main causes of tides?
Ans: The strong gravitational pull exerted by the sun and the moon on the earth’s surface causes the tides. The water of the earth closer to the moon gets pulled under the influence of the moon’s gravitational force and causes high tide.
Q5. What is spring tides and neap tides?
Ans: Spring tides: 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.
Neap tides: When the moon is in its first and last quarter, the ocean waters get drawn in diagonally opposite directions by Moon the gravitational pull of sun and earth resulting in low tides. These tides are called neap tides.
Q6. What are the main advantages of high tides?
I) This helps the ships to arrive at the harbour more easily.
II) 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.
III) The rise and fall of water due to tides is being used to generate electricity in some places.
Q7. Discuss about different types of ocean currents with example.
Ans: Ocean currents are streams of water flowing constantly on the ocean surface in definite directions. The ocean currents may be –
1) warm or
Warm:- Generally, the warm ocean currents originate near the equator and move towards the poles. For example Gulf Stream is a warm current.
The cold currents carry water from polar or higher latitudes to tropical or lower latitudes. The Labrador Ocean current is cold current.
Q8. Why the study of ocean current is more important?
I) The areas where the warm and cold currents meet provide the best fishing grounds of the world.
Seas around Japan and the eastern coast of North America are such examples.
II) The areas where a warm and cold current meet also experience foggy weather making it difficult for navigation.