GEOGRAPHY(VII)-LESSON-5 WATER (LESSON NOTES)

    GEO (VII) LESSON-5

WATER

(LESSON NOTES)

_______________________________________________________

v INTRODUCTION

Ø Water is very important for our survival. It continuously changes its form and circulates between oceans and atmosphere.

Ø The Earth is called the blue planet because its 3/4^th part is covered by water.

Ø The major source of fresh water are the rivers, ponds, springs and glaciers. The ocean bodies and the seas contain salty water.

v WATER CYCLE

Ø The process by which water changes its form and circulates between oceans, atmosphere and land is known as the water cycle.

Ø The water is evaporated from the water bodies and change into water vapour due to heat of sun.

 

Ø When the water vapour cools down, it condenses and forms clouds.

Ø From there, it may fall on the land or sea in the different forms as rain, snow or sleet that is called as Precipitation.

Ø The Precipitation in the liquid form is called as Rainfall.

v DISTRIBUTION OF WATER ON EARTH

Ø About three-fourths of the earth’s surface is covered by water.

Ø On earth 97% of water is saline and 3% of water is fresh water.

Ø The following table gives the distribution of water in percentage:

Ø Water is absolutely essential for survival.

DO YOU THINK REALLY THERE IS WATER SCARCITY IN THE WORLD. TRY TO FIND REASON

v OCEANIC CIRCULATION

Ø Ocean water keeps moving continuously. It is never still like the water of pond and lake.

Ø The movements that occur in oceans can be broadly categorised as:

§  Waves

§  Tides

§  Oceanic Currents.

v WAVES

Ø The rises and falls of water on the surface of the ocean alternately, are called waves.

Ø Waves are formed due to wind. As the wind become strong, waves become bigger.

Ø An earthquake, a volcanic eruption or underwater landslides can shift large amounts of ocean water. As a result, huge tidal wave may be formed which is called tsunami.

Ø Tsunami in South and South-East Asian coast had caused havoc in December 2004. In 2011 Tsunami also create large destruction in Japan.

v TIDES

Ø The rhythmic rise and fall of ocean water due to gravitational force of moon and sun, twice in a day is called a tide.

Ø Tides are of two types:

§  Spring tides or High Tide- 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 or Low Tide-When the moon is in its first and last quarter, the ocean waters get drawn in diagonally opposite directions by the gravitational pull of sun and earth resulting in low tides. These tides are called neap tides

v IMPORTANCE OF TIDES

Ø During high tide water level close to sea shores which helps the ships to arrive at the harbor easily.

Ø High tides also help in navigation.

Ø During high tides fish come closer to the shore which help in fishing.

Ø The rise and fall of water due to tides also used to generate electricity in some places.

v OCEAN CURRENTS

Ø The streams of water flowing constantly on the ocean surface in different directions are called as ocean currents.

 

Ø There are of two types of ocean current-

WARM OCEAN CURRENT	COLD OCEAN CURRENT
These originate near the equator and move towards the poles.	These originate from polar or higher latitudes and move toward to tropical or lower latitudes
These increase the temperature of that area where it reaches.	These decrease the temperature of that area.
Examples-Gulf stream, Kuroshio, Brazil Agulhas are some important warm currents.	Example-Canary, California, Peru and Benguela current are some cold current.

v IMPORTANCE OF OCEAN CURRENTS

 Ø Ocean current maintain the temperature of the areas.

Ø The areas where the warm and cold currents meet provide the best fishing grounds of the world.

Ø These also help for navigation.

v IMPORTANT POINTS

Ø Evaporation: It is the process through which water turns into vapour.

Ø Condensation: The process in which water vapour turns into water droplets is called as condensation.

Ø Terrarium: It is an artificial enclosure for keeping small house plants.

Ø Precipitation: Falling of moisture in the form of rainfall, snow, sleet and hailstone.

Ø Tsunami is a Japanese word that means “Harbour waves” as the harbours get destroyed whenever there is tsunami.

Ø March 22 is celebrated as World Water Day when the need to conserve water is reinforced in different ways.

Ø Salinity is the amount of salt in grams present in 1000 grams of water. The average salinity of the oceans is 35 parts per thousand.

Ø Dead sea in Israel has salinity of 340 grams per litre of water. Swimmers can float in it because the increased salt content -makes it dense.