Geography(Chap-5) Cl-7 Water

Geography(Chap-5)                                     Water

Ø  The sun’s heat causes evaporation of water into vapour.

Ø  When the water vapour cools down, it condenses & forms clouds and from there it falls down on earth in the form of rain, snow or sleet..

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

Ø  ‘Terrarium’ is an artificial enclosure for keeping small house plants.

Ø  Our earth is like a terrarium. The same water that existed centuries ago still exists today. So, next time you drink a glass of water think that the hydrogen molecules in water are 14 billion years old, they were created at the same time as Universe.

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

Ø  The ocean  bodies and the seas contain the salty water or saline as it contains large amount of dissolved salts. Most of the salt is sodium chloride/the common salt.

Ø   Salinity is the amount of salt in grams present in thousand grams in water.

Ø  The average salinity of the ocean is 35 parts per thousand.

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

·         Ocean Circulation:

Ø  The movement of that occur in oceans can broadly categorized as Waves, Tides and Currents.

Ø  Each year March 22 is observed as World Water Day( the need to conserve water is reinforced in different ways).

Ø  When the water in the surface of the ocean rises and falls alternately, they are called Waves.

Ø  Waves are formed when the winds scrape the ocean surface. The stronger the wind blows, the bigger the wave becomes.

Ø  ‘Tsunami’ is a Japanese word that means “Harbour waves”.

Ø  A huge tidal wave called Tsunami is formed because of an earthquake, a volcano or under water  

land slides.

Ø  The ’Indira Point’ in the Andaman and Nicobar islands got submerged after  the Tsunami in 2004.

Ø  Tide is the rhythmic rise and fall of ocean water twice in a day.

Ø  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.

Ø  The strong gravitational pull exerted by the sun and the moon on the earth’s surface causes Tides.

Ø  The water of the earth closer to the moon gets pulled under the influence of the moon’s gravitational force and causes high tide.

Ø  During the Full Moon and New Moon days, the Sun, the Moon and the Earth are on the a same line and tides are the highest. These tides are called Spring tides.

Ø  When the moon is in its first and last quarter, the ocean water get drawn- law tides/ neap tides.

Ø  High tides help in navigation. They raise the water level close to the chores.

Ø  The high tides also help in fishing as many more fish come closer to the shore during high tide. This enables the fisher man to get a plentiful catch.

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

Ø  Ocean currents are streams of water flowing constantly on the ocean surface in definite directions. It may be warm or cold.

Ø  Generally, the warm water currents originate near the Equator and move towards the Poles.

Ø  The cold currents carry water from polar /higher latitudes to tropical or lower latitudes.

Ø  The Labrador ocean current is cold current while the Gulf stream is a warm current.

Ø  The ocean current influence the temperature conditions of the area. Where currents bring about warm temperature over land surface.

Ø  The areas where the warm and cold currents meet provide the best fishing grounds of the world. For example, seas around Japan and eastern coast of North America.

Ø  The areas where a warm and cold water meet also experience foggy weather making it difficult for navigation.