CBSE Class 11 Geography Water Oceans Notes

WATER (OCEANS)

This unit deals with• Hydrological Cycle

• Oceans — submarine relief; distribution of temperature and salinity; movements of ocean water-waves, tides and currents

The earth, fortunately has an abundant supply of water on its surface. Hence, our planet is called the ‘Blue Planet’.

HYDROLOGICAL CYCLE

The hydrological cycle, is the circulation of water within the earth‘s hydrosphere in different forms i.e. the liquid, solid and the gaseous phases. It also refers to the continuous exchange of water between the oceans,

STUDY THE GIVEN TABLE SHOWING THE WATER COMPOSITION ON THE EARTH SURFACE AND ANSWER THE FOLLOWING

QUESTIONS

1. What is the % of water in the oceans?

2. Which component of the earth consists of least percentage of water content?

3. what is the main use of soil moisture? Study above table and answer the questions that fallow

1. What do you mean by evapotranspiration?

2. What are the different forms of water in the atmosphere?

The above table shows the distribution of water on the surface of the earth. About 71 per cent of the planetary water is found in the oceans. The remaining is held as freshwater in glaciers and icecaps, groundwater sources, lakes, soil moisture, atmosphere, streams and within life. Nearly 59 per cent of the water that falls on land returns to the atmosphere through evaporation from over the oceans as well as from other places. The remainder runs-off on the surface, infiltrates into the ground or a part of it becomes glacier. It is to be noted that the renewable water on the earth is constant while the demand is increasing tremendously. This leads to water crisis in different parts of he world — spatially and temporally. The pollution of river waters has further aggravated the crisis. How can you intervene in improving the water quality and augmenting the available quantity of water?

RELIEF OF THE OCEAN FLOOR

Divisions of the Ocean Floors

The ocean floors can be divided into four major divisions:

1) The Continental Shelf;

2) The Continental Slope;

3) The Deep Sea Plain;

4) The Oceanic Deeps.

Besides, these divisions

There are also major and minor relief features in the ocean floors like ridges, hills, sea mounts, guyots, trenches, canyons, etc.

Continental Shelf

1. The continental shelf is the extended margin of each continent occupied by relatively shallow seas and gulfs.

2. It is the shallowest part of the ocean showing an average gradient of 1° or even less.

3. The shelf typically ends at a very steep slope, called the shelf break.

4. The width of the continental shelves vary from one ocean to another.

5. The average width of continental shelves is about 80 km.

6. The shelves are almost absent or very narrow along some of the margins like the coasts of Chile, the west coast of Sumatra, etc.

7. On the contrary, the Siberian shelf in the Arctic Ocean, the largest in the world, stretches to 1,500 km in width.

8. The depth of the shelves also varies. It may be as shallow as 30 m in some areas while in some areas it is as deep as 600 m.

9. The continental shelves are covered with variable thicknesses of sediments brought down by rivers, glaciers, wind, from the land and distributed by waves and currents.

10.Massive sedimentary deposits received over a long time by the continental shelves, become the source of fossil fuels.

Continental Slope

1. The continental slope connects the continental shelf and the ocean basins.

2. It begins where the bottom of the continental shelf sharply drops off into a steep slope.

3. The gradient of the slope region varies between 2-5°.

Please click the link below to download pdf file for CBSE Class XI Geography Water ( Oceans) Concepts.