Chapter 5 Notes
Major Domains of the Earth
Class 6 – Social Science
|Major Domains of the Earth
|Class 6 Geography Notes
Question 1 Why life is possible on Earth ?
Question 2 What are the three major domains of the earth?
Question 3 What are the two divisions of Earth’s surface?
Question 4 Define the term lithosphere, hydrosphere, atmosphere and Biosphere.
Question 5 Name the highest peak and greatest depth on the Earth.
Question 6 Name the seven continents in increasing order of their size.
Question 7 Name the world largest and hottest desert and longest river.
Question 8 What is Eurasia and Isthmus of Panama?
Question 9 Name the world longest mountain range and largest river.
Question 10 Why Earth is called blue planet?
Question 11 What is atmosphere. Why is it important for us?
Question 12 Describe the oceans of the world.
Question 13 Give a brief description of the continents of the world.
Question 14 Discuss the organism found in biosphere.
Question 15 Explain the layers of atmosphere.
Question 16 What is global warming ? State the factors responsible for it.
Question 17 What negative impacts on nature are caused by the cutting of trees?
Question 18 Write few features of biosphere.
Question 19 Explain the composition of atmosphere.
Question 20 Name the three movements of the ocean water.
Question 21 Inspite of being called the Blue Planet, the earth experiences shortage of water. Why?
Question 22 Why do climbers often experience breathing problems?
Question 23 How does the atmosphere act as a blanket?
Question 24 What are the main gases that comprise the atmosphere?
Question 25 Why is the Atlantic ocean the world’s busiest ocean in terms of commerce?
Question 26 Define pressure, temperature and density of atmosphere.
Question 27 Where do the Equator, tropic of cancer and the tropic of capricorn pass in Africa?
Question 28 What are the major effects of water pollution?
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.
The surface of the earth is a complex zone in which three main components of the environment meet, overlap and interact. Life exists on the Earth due to the presence of three main domains – land, water and air.
The land masses which provide living space for humans, animals and plants represent the solid domain of the Earth. The solid portion of the earth on which we live is called the Lithosphere.
The gaseous layers that surround the earth, are the Atmosphere, where oxygen, nitrogen, carbon dioxide and other gases are found.
Water covers a very big area of the earth’s surface and this area is called the Hydrosphere. The Hydrosphere comprises water in all its forms, that is, ice, water and water vapour. The oceans, seas and other water bodies which fill the depressions of the Earth’s surface represent the liquid domain.
The Biosphere is the narrow zone of contact between land, water and air together, which contains all forms of life.
The solid portion of the earth is called the Lithosphere. It covers 29% of the Earth’s surface. The Greek word Lithos means rocks.
It comprises the rocks of the earth’s crust and the thin layers of soil that contain nutrient elements which sustain organisms.
There are two main divisions of the Earth’s surface :
1) The large landmasses are known as the continents
2) The huge water bodies are called the ocean basins.
The level of seawater remains the same everywhere. Elevation of land is measured from the level of the sea, which is taken as zero.
The highest mountain peak Mt. Everest is 8,848 metres above sea level.
The greatest depth of 11,022 metres is recorded at Mariana Trench in the Pacific Ocean.
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.
The greater part of the land mass lies in the Northern Hemisphere.
a) Asia is the largest continent. It covers about one-third of the total land area of the earth. The continent lies in the Eastern Hemisphere. The Tropic of Cancer passes through this continent. Asia is separated from Europe by the Ural mountains on the west.
It is surrounded by the Pacific Ocean in the east, the Arctic Ocean in the north, the Indian Ocean in the south and the Ural mountains in the west.
The Bering Strait separates Asia from North America.
The Suez Canal separates Asia from Africa.
The Himalayas are the highest mountain range in the world and Tibet is the highest plateau.
The combined landmass of Europe and Asia is called the Eurasia (Europe + Asia).
b) Europe is much smaller than Asia. It is the sixth-largest continent.
The continent lies to the west of Asia. The Arctic Circle passes through it. It lies almost entirely in the temperate zone. It is surrounded by the Arctic Ocean in the north, the Atlantic Ocean in the west and the Mediterranean Sea in the south.
c) Africa is the second largest continent after Asia. The Equator runs almost through the middle of the continent. A large part of Africa lies in the Northern Hemisphere.
It is the only continent through which the Tropic of Cancer, the Equator and the Tropic of Capricorn pass. The Sahara Desert, the world’s largest hot desert, is located in Africa.
The continent is bound on all sides by oceans and seas. You will notice that the world’s longest river the Nile, flows through Africa.
d) North America is the third largest continent of the world. It is linked to South America by a very narrow strip of land called the Isthmus of Panama. The continent lies completely in the Northern and Western Hemisphere. Three oceans surround this continent.
e) South America lies mostly in the Southern Hemisphere. The Andes, the world’s longest mountain range, runs through its length from north to south. South America has the world’s largest river, the Amazon.
f) Australia is the smallest continent that lies entirely in the Southern Hemisphere. It is surrounded by the oceans and seas. It is called an island continent.
Along with New Zealand and other nearby islands, it is called Australasia. The Great Barrier Reef is a unique feature along the north-eastern coast of Australia. It is built by corals.
g) Antarctica, completely in the Southern Hemisphere, is a huge continent. 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.
Due to the thick ice cover, it is known as the white continent. It is surrounded by the Pacific, Atlantic and Indian oceans.
There are no permanent human settlements. Many countries have research stations in Antarctica. India also has research stations there. These are named Maitri and Bharati.
The earth is called the blue planet. More than 71 per cent of the earth is covered with water and 29 per cent is with land.
The hydrosphere consists of water in all its forms. Running water in oceans and rivers and lakes, ice in glaciers, underground water and water vapour in the atmosphere, all comprise the hydrosphere.
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 ice sheets 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!!
Oceans are a major part of the hydrosphere. They are all interconnected. Thus, the level of water in the oceans and seas is the same throughout. This is called mean sea level. The ocean waters are always moving.
The average depth of the ocean water is about 3800 m below the mean sea level while the average height of land is only about 850 m above the mean sea level. The greatest depth is at Mariana Trench on the Eastern side of the Pacific Ocean.
The three chief movements of ocean waters are the waves, the tides and the ocean currents.
The five major oceans are the Pacific Ocean, the Atlantic Ocean, the Indian Ocean, the Southern Ocean and the Arctic Ocean, in order of their size.
1) The Pacific Ocean is the largest and deepest ocean.
It is spread over one-third of the earth.
Mariana Trench, the deepest part of the earth, lies in the Pacific Ocean.
The Pacific Ocean is almost circular. It is bounded by Asia and Australia in the west and North America and South America in the East.
In 1520, A European sailor, Ferdinand Magellan was the first to sail across this ocean.
2) 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.
The coastline of the Atlantic Ocean is highly indented. This irregular and indented coastline provides an ideal location for natural harbours and ports.
From the point of view of commerce, it is the busiest Ocean.
3) The Indian Ocean is the only ocean named after a country, that is, India. The shape of the ocean is almost triangular.
In the north, it is bound by Asia, in the west by Africa and the east by Australia.
4) The Southern Ocean encircles the continent of Antarctica and extends northward to 60 degrees south latitude.
5) 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 the Berring Strait.
It is bound by the northern coasts of North America and Eurasia.
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 the sun’s rays.
The atmosphere extends up to a height of about 1,600 kilometres.
The atmosphere is divided into five layers based on composition, temperature and other properties.
These layers starting from the earth’s surface are called the troposphere, the stratosphere, the mesosphere, the thermosphere and the exosphere.
The atmosphere is composed mainly of nitrogen and oxygen, which make up about 99 per cent of clean, dry air. Nitrogen is 78 per cent, oxygen is 21 per cent and other gases like carbon dioxide, argon and others comprise 1 per cent by volume.
1) Oxygen is the breath of life.
2) Nitrogen helps in the growth of living organisms.
3) Carbon dioxide, though present in minute amounts, is important as it absorbs heat radiated by the earth, thereby keeping the planet warm. It is also essential for the growth of plants.
The density of the atmosphere varies with height. It is maximum at the sea level and decreases rapidly as we go up.
The climbers experience problems 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.
The temperature also decreases as we go upwards. The atmosphere exerts pressure on the earth. This varies from place to place. Some areas experience high pressure and some areas low pressure. Air moves from high pressure to low pressure. Moving air is known as wind.
The biosphere is the narrow zone of contact between the land, water and air.
It is in this zone that life, which is unique to this planet, exists.
There are several species of organisms that vary in size from microbes and bacteria to huge mammals.
All living organisms including humans are linked to each other and the biosphere for survival.
The organisms in the biosphere may broadly be divided into the plant kingdom and the animal kingdom.
The three domains of the earth interact with each other and affect each other in some way or the other.
For example: Cutting off forests to fulfil our wood needs, or clearing land for agriculture may lead to the fast removal of soil from slopes.
Earth’s surface may be changed due to natural calamities like earthquakes. For example, there could be submergence of land, as happened in the case of Tsunami recently. Parts of Andaman & Nicobar Islands were submerged underwater.
The discharge of waste material into lakes and rivers makes the water unsuitable for human use. It also damages other forms of life.
Emissions from industries, thermal power plants and vehicles, pollute the air. Carbon dioxide
(CO2 ) is an important constituent of air. However, an increase in the amount of CO2 leads to an increase in global temperatures. This is termed as global warming. There is thus, a need to limit the use of resources of the earth to maintain the balance of nature between the domains of the lithosphere, the atmosphere and the hydrosphere.