Chapter 5. Major Domains of Earth

Major parts
Lithosphere: Solid portion of earth on which we live.
Atmosphere: gaseous layers that surround Earth.
Hydrosphere: A large portion of earth’s surface is covered by water.
Biosphere: A narrow area where we find land, water & air, which consists of all forms of life.

Lithosphere
• It consists of rocks of crust and a thin layer of soil which sustains life.
• Earth surface is divided in continents and oceans.
• level of seawater remains same everywhere, therefore we measure elevation of land from sea level.
• highest mountain peak Mt. Everest is 8, 848 metres from sea level.
• greatest depth of 11,022 metres is recorded at Marianna Trench in Pacific Ocean.

Continents
Asia
(1) This is largest continent which covers one-third of total land areas of earth and lies in Eastern Hemisphere.
(2) This is separated from Europe by Ural Mountains on west. Tropic of Cancer passes through this continent.
(3) combined landmass of Asia and Europe is known as Eurasia.
Europe
(1) This is much smaller than Asia and lies in west of Asia.
(2) Arctic Circle passes through it.
(3) This is bounded by water bodies on three sides.
Africa
(1) This is second-largest continent.
(2) This is only continent through which Tropic of Cancer, Equator & Tropic of Capricorn pass.
(3) world’s largest desert, Sahara is located on this continent.
(4) This is bounded by oceans and seas on all sides.
(5) world’s longest river Nile, flows through Africa.
North America
(1) This is third-largest continent which is linked with South America by a narrow strip known as Isthmus of Panama.
(2) It completely lies in Northern and Western Hemisphere and is surrounded by three oceans.
South America
(1) It lies mostly in Southern Hemisphere.
(2) This is bounded by two oceans from east and west sides.
(3) largest Mountain range, Andes runs through its length from north to south.
Australia
(1) This is smallest continent and surrounded by ocean on all sides, therefore, known as island continent.
(2) It lies entirely in Southern Hemisphere.
Antarctica:
(1) It completely lies in Southern Hemisphere.
(2) This is permanently covered with thick ice sheets where no human settlement exists.
(3) India’s two Research Stations, Maitri & Dakshin Gangotri are stationed there.

Atmosphere
• This is a layer of gas that is an important part of planet and keeps us safe from Sun’s harmful rays. This is up to 1600 km long and is split into five layers based on their composition, temperature, and other factors.
• layers starting from earth surface are known as troposphere, stratosphere, mesosphere, thermosphere and exosphere.
• atmosphere is composed of nitrogen 78%, oxygen 21% and other gases [carbon dioxide, argon & others] 1%.
• Oxygen is used for breathing and nitrogen is important for growth of life.
• Carbon dioxide absorbs heat radiation and keeps earth warm and essential for growth of plants.

Hydrosphere
• More than 71% of Earth is covered with water and 29% with land.
• Hydrosphere consists of all forms of water. It comprises of Lakes, Ice in glacier, Ground water and Water vapour in atmosphere.
• More than 97% of earth’s water is salty and major portion of rest of water is in form of ice sheets, glacier & under ground and very small percentage is available as fresh water for human use.

Oceans
• four major oceans are:
(1) Pacific Ocean
(2) Atlantic Ocean
(3) Indian Ocean
(4) Southern Ocean
(5) Arctic Ocean
• Three chief movements of ocean’s water are wave, tide & ocean current.
Pacific Ocean
(1) This is largest ocean that spread over one-third of earth.
(2) This is almost circular in shape and bounded by Asia, Australia, North America and South America.
Atlantic Ocean:
(1) This is ‘S’ shaped and second largest ocean in world.
(2) This is bounded by North and South Americas on western side and Europe and Asia on eastern side.
(3) Its coastline is irregular and highly indented which provides ideal location for natural harbours and ports.
(4) This is busiest Ocean.
Indian Ocean:
(1) This is only ocean which is named after a country that is India.
(2) This is bounded by Asia, Africa & Australia.
(3) This is almost triangular shaped.
Southern Ocean
(1) It encircles continent of Antarctica.
(2) It extends northward to 60 degrees south latitude.
Arctic Ocean:
(1) This is located within Arctic Circle and surrounded North Pole.
(2) This is connected with Pacific Ocean by a narrow and shallow stretch of water known as Berring strait.
(3) This is bounded by northern coasts of North America and Eurasia.

Biosphere
• This is a narrow zone of contact between land, water & air and is known as zone of life.
• All organisms are linked to each other and to biosphere for survival.
• organisms in biosphere are broadly classified in Plant kingdom and Animal kingdom.
• Carbon dioxide is an important component of air but increase in its amount leads to global warming.

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