RBSE Class 7 Social Science Notes Geography Chapter 5 Water

These comprehensive RBSE Class 7 Social Science Notes Geography Chapter 5 Water will give a brief overview of all the concepts.

RBSE Class 7 Social Science Notes Geography Chapter 5 Water

→ Water Cycle:

• The sun’s heat causes evaporation of water into vapour. When the water vapour cools down, it condenses and forms clouds. From there it may fall on the land or sea in the form of rain, snow or sleet.
• The process by which water continually changes its form and circulates between oceans, atmosphere and land is known as the water cycle.

→ Terrarium: Our earth is like a terrarium. The same water that existed centuries ago still exists today.

→ Types of water: They are of two types

• Fresh water,
• Salty water.

→ Distribution of Water Bodies: Three-fourth of the earth surface is covered by water. The distribution of water on the earth in percentage is as follows -

• Oceans : 97.3,
• Ice-caps : 02.0,
• Ground water : 0.68,
• Fresh water lakes : 0.009,
• Inland seas and salt lakes : 0.009,
• Atmosphere : 0.0019, Rivers : 0.0001.

Water is absolutely essential for survival. So, we should not waste this precious resource carelessly.

→ Ocean Circulation: It is never still. The movements that occur in oceans can be broadly categorised as :

• Waves
• Tides, and
• Currents.

→ Waves: When the water on the surface of the ocean rises and falls alternately, they are called waves. Waves are formed when wind scrapes across the ocean surface. The stronger the wind blows the bigger the waves become. Massive waves arise in the storm, which 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, that may be as high as 15m., is formed. Harbour wave is destroyed by tsunami.

→ Tides:

• The rhythmic rise and fall of ocean water twice in a day is called a tide.
• The strong gravitational pull exerted by the sun and the moon on the earth’s surface causes the tides.
• During the full moon and new moon days, the tides are highest. These tides are called spring tides.
• When the moon is in its first and last quarter, it results in low tides. These tides are called neap tides.
• High tides help in navigation and in fishing. They are also used to generate electricity in some places.

→ Ocean Currents:

• Ocean currents.are streams of water flowing constantly on the ocean surface in definite directions.
• The ocean currents may be warm or cold.
• The warm ocean currents originate near the equator and move towards the poles.
• The cold currents carry water from polar or higher latitudes to tropical or lower latitudes.
• Warm currents bring about warm temperature over land surface. Meeting point of both the currents are known as the best fishing grounds. It experiences foggy weather making it difficult for navigation.