CLASS- VI GEO. CHAPTER-5
MAJOR DOMAINS OF THE EARTH
The earth is the only planet which has life.
Human beings can live here because the life sustaining elements of land, water and air are present on the earth.
·
Earth
has three main components they are:-lithosphere,Atmosphere,Hydrosphere
·
Lithosphere:- i.The solid portion of the earth on which we live is called the
Lithosphere.
ii. It comprises the rocks of the earth’s crust and the thin layers
of soil that contain nutrient elements which sustain organisms.
·
Atmosphere:- The gaseous layers that surround the earth, is the Atmosphere, where oxygen,
nitrogen, carbondioxide and other gases are found.
·
Hydrosphere:-
i.Water
covers a very big area of the earth’s surface and this area is called the Hydrosphere.
ii. More
than 71 per cent of the earth is covered with water and 29 per cent is with
land.So earth is called ‘blue planet’.
iii. Hydrosphere
consists of water in all its forms. As running water in oceans and rivers and
in lakes, ice in glaciers, underground water and the water vapour in
atmosphere, . all
comprise the hydrosphere.
iv. More than 97% of the Earth’s water is
found in the oceans and is too salty for human use. A large proportion of the
rest of the water is in the form of icesheets and glaciers .
or under the ground and a very small
percentage is available as fresh water for human use. Hence, despite
being a ‘blue planet’ we face a shortage of water!!
Biosphere :-The Biosphere is the narrow zone
where we find land, water and air together, which contains all forms of life.
·
There are two main divisions of the earth’s surface. The large
landmasses are known as the continents and the huge water bodies are called the ocean basins.
·
i.The level of seawater remains the same everywhere. Elevation
of land is measured from the level of the sea,which is taken as zero.
·
ii. The highest mountain peak Mt. Everest is 8,848 metres above
the sea level. The greatest depth of 11,022 metres is recorded at Mariana
Trench in the Pacific Ocean.
Continents
·
There are seven major continents. These are separated by large
water bodies. These continents are – Asia, Europe, Africa, North America, South
America, Australia and Antarctica.
·
Asia
i.Asia is the largest
continent. It covers about onethird of the total land area of the earth.
ii.The
continent lies in the Eastern Hemisphere.
iii.The
Tropic of Cancer passes through this continent. Asia is separated from Europe
by the Ural mountains on the west.The combined landmass of Europe and Asia is called the Eurasia (Europe + Asia).
·
Europe
i.Europe is much smaller than
Asia. The continent lies to the west of Asia.
ii. The
Arctic Circle passes through
it. It is bound by water bodies on three sides.
·
Africa
i.Africa is the second largest
continent after Asia. The Equator or 00 latitude runs almost through the middle of the continent. A
large part of Africa lies in the Northern Hemisphere.
ii. it is the only continent
through which the Tropic of Cancer, the Equator and the Tropic of Capricorn
pass.
iii. The Sahara Desert, the
world’s largest hot desert, is located in Africa. The continent is bound on all
sides by oceans and seas.
iv. the world’s longest
river the Nile, flows through Africa.
·
North America
i.North
America is
the third largest continent of the world.
ii.It is linked to South
America by a very narrow strip of land called the Isthmus of Panama.
iii.The continent lies
completely in the Northern and Western Hemisphere. Three oceans surround this
continent.
·
South America
i.South
America lies
mostly in the Southern Hemisphere.
ii. The
Andes, world’s longest mountain range, runs through its length from north to
south.
iii.South America has the world’s largest river, the Amazon.
·
Australia
i.Australia is the smallest
continent that lies entirely in the Southern Hemisphere.
ii.It is surrounded on all sides by the oceans and seas. It is called an island continent.
·
Antarctica
i. Antarctica, completely in the
Southern Hemisphere, is a huge continent.
ii.The
South Pole lies almost at the centre of this continent. As it is located in the
South
Polar Region, it is permanently covered with thick ice sheets.
iii.There
are no permanent human settlements. Many countries have research stations in
Antarctica. India also has research stations there. These are named as Maitri and Dakshin Gangotri.
Oceans
i.Oceans
are the major part of hydrosphere. They are all interconnected.
ii.The ocean waters are always moving. The three chief movements of ocean
waters are the waves, the tides and the ocean currents.
iii. The
five major oceans are the Pacific Ocean, the Atlantic Ocean, the Indian Ocean, the
Southern Ocean and the Arctic Ocean.
Pacific
Ocean
i.The Pacific
Ocean is the largest ocean. It is spread over one-third of the earth.
ii.Mariana
Trench, the deepest part of the earth, lies in the Pacific Ocean.
iii.The Pacific Ocean is almost circular in
shape. Asia, Australia, North and South Americas surround it.
The
Atlantic Ocean
i.The
Atlantic Ocean is the second largest Ocean in the world. It is ‘S’ shaped. It
is flanked by the North and South Americas on the western side, and Europe and
Africa on the eastern side. ii.The coastline of Atlantic Ocean is highly indented. This irregular and
indented coastline provides ideal location for natural harbours and ports. From
the point of view of commerce, it is the busiest Ocean.
The
Indian Ocean
i.The
Indian Ocean is the only ocean named after a country, that is, India.
ii.The shape of ocean is almost triangular. In
the north, it is bound by Asia, in the west by Africa and in the east by
Australia.
The
Southern Ocean
i.The
Southern Ocean encircles the continent of Antarctica and extends northward to
60 degrees south latitude.
The
Arctic Ocean
The Arctic
Ocean is located within the Arctic Circle and surrounds the North Pole. It is
connected with the Pacific Ocean by a narrow stretch of shallow water known as Berring
strait. It is bound by northern coasts of North America and Eurasia.
i.The earth
is surrounded by a layer of gas called the atmosphere. This thin blanket of air is an integral and
important aspect of the planet. It provides us with the air we breathe and
protects us from the harmful effects of sun’s rays.
ii. The
atmosphere extends up to a height of about 1,600 kilometres which is further
divided into five layers based on composition, temperature and other properties
such as:- troposphere, the stratosphere, the mesosphere, the thermosphere and
the exosphere.
iii. The
atmosphere is composed mainly of Nitrogen 78 per cent, oxygen 21 per cent and
other gases like carbondioxide, argon and others comprise 1 per cent by volume.
iv. Oxygen
is the breath of life while nitrogen helps in the growth of living organisms.
Carbon dioxide, though present in minute amount, is important as it absorbs
heat radiated by the earth, thereby keeping the planet warm.
·
The density of the atmosphere varies with height. It is maximum
at the sea level and decreases rapidly as we go up. You know, the climbers
experience problems in breathing due to this decrease in the density of air.
They have to carry with them oxygen cylinders to be able to breathe at high
altitudes.
·
Air moves from high pressure to low pressure. Moving air is
known as wind.
BIOSPHERE – THE DOMAIN OF LIFE
i.The biosphere is the narrow zone of
contact between the land, water and air. It is in this zone that life.
ii. All the
living organisms including humans are linked to each other and to the biosphere
for survival.
·
Discharge of waste material into lakes and rivers makes the water
unsuitable for human use. It also damages other forms of life.
·
Emission from industries, thermal power plants and vehicles,
pollute the air. Carbon dioxide (CO2) is an important
constituent of air. But increase in the amount of CO2 leads to increase in global temperatures.This is termed as
global warming.
·
ISTHMUS
A narrow strip of land
joining two landmasses.
STRAIT
A strait is a narrow
passage of water connecting two large waterbodies like seas and ocean.
No comments:
Post a Comment