Water grade 7

Water grade 7

WATER

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

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

• The major sources of fresh water are the rivers, ponds, springs and glaciers. 

OCEAN

• The ocean bodies and the seas contain salty water.

• The water of the oceans is salty or saline as it contains large salt in it

• Most of the salt is sodium chloride or the common table salt that you eat.

• Salinity is the amount of salt in grams present in 1000 grams of water

DO YOU KNOW

• The average salinity of the oceans is 35 parts per thousand.

• Dead sea in Israel has salinity of 45 parts per thousand.

• Swimmers can float in it because the increased salt content make it dense. 

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DISTRIBUTION OF WATER BODIES

• Oceans : 97.3

• Ice-caps : 02.0

• Ground water : 0.68

• Fresh Water Fresh water lakes : 0.009

• Inland seas & Salt lakes : 0.009 A

• Atmosphere : 0.0019

• Rivers : 0.0001

OCEAN CIRCULATION

• Unlike the calm waters of ponds and lakes, ocean water keeps moving continuously. It is never still. The movements that occur in oceans can be broadly categorised as: waves, tides and currents.

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WAVES

• When the water on the surface of the ocean rises and falls alternately, they are called waves.

• 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,

Tides

• The rhythmic rise and fall of ocean water twice in a day is called a tide

• It is high tide when water covers much of the shore by rising to its highest level. It is low tide when water falls to its lowest level and recedes from the shore.

• 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

SPRING 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.

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NEAP TIDES

• 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

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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

WARM CURRENTS

• Generally, the warm ocean currents originate near the equator and move towards the poles

•  Gulf Stream is a warm current.

COLD CURRENTS

• he cold currents carry water from polar or higher latitudes to tropical or lower latitudes. The Labrador Ocean current is cold current

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THANKS!!!