Class 6 Geography Chapter 5 Notes - Major Domains of the Earth

The earth consists of 4 different types of major domains. The major domains of the earth include:

1. Lithosphere
2. Atmosphere
3. Hydrosphere
4. Biosphere

The earth is a really big place and there is no doubt that most of the major domains of the earth tend to mix together to create the environment that we live in.

• Lithosphere: The solid portion of the earth.
• Atmosphere: The gaseous layers that surround the earth.
• Hydrosphere: Water covers a very big area of the earth’s surface and this area is called the Hydrosphere.
• Biosphere: It is the narrow zone where land, water and air together are found.

Lithosphere

• The solid portion of the earth is called the lithosphere. It is composed of rocks of the earth’s crust. There is a thin layer of soil on top that contains mineral nutrients which sustain various organisms.

• The earth’s surface can be divided into two main parts, viz. the continents and the ocean basins.
  (i) Continents: The huge landmasses on the earth are called continents.
  (ii) Ocean Basins: The huge water bodies on the earth are called ocean basins.

Continents

There are seven continents and all of them are separated by large water bodies. The seven continents of the world are; Asia, Europe, Africa, North America, South America, Australia and Antarctica.

• Asia: This is the largest continent. Asia covers about one-third of the total land area of the earth. This continent lies in the eastern hemisphere.
• Europe: Europe lies to the west of Asia and is much smaller than Asia. It is bound by water bodies from three sides.
• Africa: Africa is the second-largest continent. The major portion of Africa lies in the northern hemisphere.
• North America: It is the third-largest continent. North America and South America are connected to each other by the Isthmus of Panama.
• Isthmus: A narrow strip of land which joins two landmasses is called the isthmus. North America lies in the northern hemisphere and western hemisphere.

• South America: A major portion of South America is in the southern hemisphere. This continent is surrounded by two oceans, viz. the Atlantic and Pacific oceans.
• Australia: This is the smallest continent. It lies entirely in the southern hemisphere. Since Australia is surrounded on all sides by ocean hence it is called the island continent.
• Antarctica: This is a huge continent and is present in the South Polar Region. In fact, the South Pole lies at the centre of this continent.

Hydrosphere

• The earth is called the blue planet. More than 71% of the earth is covered with water and 29% is with the land. 
• The hydrosphere consists of water in all its forms. 
• 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.

Oceans

All the oceans of the world are connected to each other. Due to this, the level of seawater is the same everywhere. The elevation of the land is measured from the sea level and the sea level is taken as zero. Waves, tides and ocean currents are the three main movements of ocean water. There are five major oceans, viz. Pacific, Atlantic, Indian, Arctic and Southern oceans.

• Pacific Ocean: This is the largest ocean. It is almost circular in shape. The Pacific Ocean is surrounded by Asia, Australia, North America and South America.
• Atlantic Ocean: This is the second-largest ocean. It is S-shaped. North America and South America are to the west of this ocean. Europe and Africa are on the east of this ocean.
• Indian Ocean:  Indian Ocean is the only ocean to be named after a country. This ocean is almost triangular in shape. Asia is towards the north, Africa is towards the west and Australia is towards the east of this ocean.
• Southern Ocean: This Ocean encircles Antarctica. It extends northwards up to 60oS latitude.
• Arctic Ocean: This Ocean is within the Arctic Circle. It surrounds the North Pole. It is bound by the northern coasts of North America and Eurasia.

Atmosphere

Atmosphere plays an important role in the environment on earth. The atmosphere is made of air which is composed of many gases, water vapour and dust particles.

• Composition of Air: Air is mainly composed of nitrogen and oxygen. 78% of the air is composed of nitrogen, 21% is composed of oxygen and the rest 1% is composed of carbon dioxide, argon and many other gases.
• Role of Nitrogen: Nitrogen is important for plants because plants make many important molecules from nitrogen.
• Role of Oxygen: Oxygen is required by living beings for respiration. Moreover, oxygen is also required for burning various fuels.
• Role of Carbon Dioxide: Carbon dioxide is utilized by plants during photosynthesis. You may recall that photosynthesis is the process by which plants make food.

Layers of Atmosphere

• The atmosphere can be divided into many layers. The troposphere is at the bottom. This is followed by stratosphere, mesosphere, thermosphere and exosphere.

Layers of Atmosphere

• The density of the atmosphere changes with height. Air is at a maximum density at the sea level and becomes rarer as we go higher.
• Humans are comfortable while breathing under normal pressure. When the atmospheric pressure becomes low, it becomes difficult to breathe.
• Atmospheric pressure is very low at high mountains. Due to this, mountaineers need to carry oxygen cylinders so that they can breathe comfortably at high altitude. The difference in pressure also plays a role in wind movements.
• Air moves from high pressure to low pressure. Moving air is called wind.

Biosphere: The Domain of Life

The narrow zone of contact between the lithosphere, hydrosphere and atmosphere is called the biosphere.

• Life exists in this zone. A variety of organisms exist on earth. There are several species of organisms that vary in size from microbes and bacteria to huge mammals. 
• All the living beings are linked to each other for their survival. They are also linked to various non-living things for their survival.
• The organisms in the biosphere are broadly divided into the plant kingdom and the animal kingdom.

Frequently Asked Questions (FAQs)

Ques: What are the four major domains of the earth?

The four main domains of the earth are Lithosphere, atmosphere, hydrosphere, and biosphere.

Ques: Which two continents lie fully in the Southern Hemisphere?

Australia and Antarctica lie completely in the Southern Hemisphere.

Ques: What are the Different Layers of the Atmosphere?

The troposphere is at the bottom and followed by stratosphere, mesosphere, thermosphere and exosphere.