[Geography Notes] on What are the Domains of the Earth Pdf for Exam

Earth is the planet in our solar system that has the capability to provide life. The surface of the earth is a zone where three main components of the environment meet, overlap as well as interact. 

There are four major domains of the Earth as follows-  lithosphere, atmosphere, hydrosphere, and the biosphere. The atmosphere is further divided into four layers based on composition, temperature, and other properties that are the troposphere, stratosphere, mesosphere, thermosphere, and exosphere. 

There are Two Main Divisions of the Surface of the Earth

1. Continents: Continents are large landmasses.

The Highest Mountain Peak on this planet is Mount Everest. 

2. Ocean Basins: Oceans are huge water bodies.

Mariana Trench is the deepest Oceanic trench on this Earth which derives its name from the nearby Mariana Islands.

The Four Major Domains of the Earth

The four major domains of the earth interact with each other as well as affect each other in some way or the other.

Lithosphere: The solid portion of this planet is called the Lithosphere. 

Atmosphere: The gaseous layers that surround the earth are called the atmosphere.

Hydrosphere: Water covers a very big area of the earth’s surface that is called the Hydrosphere.

Biosphere: Biosphere is the zone where land, water, and air together are found.

1. Lithosphere – The Domain of Land

The very outermost portion of the Earth which consists of the Upper Mantle and also the Crust of the Earth is known as the Lithosphere.

Lithosphere has very rigid mechanical properties. The uppermost part of the lithosphere is called the pedosphere. The tectonic plates are a subdivision of the Lithosphere. The major changes in these tectonic plates had created a total of seven continents on the planet earth. These continents are – Asia, America, Europe, Africa, Antarctica and Australia. Asia is the largest continent and the smallest continent is Australia.

2. Hydrosphere – The Domain of Water

The domain of water is called the hydrosphere. It comprises different sources of water and also various types of water bodies like rivers, lakes, seas, oceans, etc. Water is very essential for all living organisms in the world. 

The hydrosphere comprises water on earth in Oceans, Seas, Rivers, Lakes, and even in frozen forms where 2.5% is freshwater and in this 2.5%; approximately 69% is in snow and ice form. The other 97.5% of Earth’s water is salt water and 71% of the surface of the Earth is covered by oceans. Earth got a total of seven oceans namely – the Arctic, North Atlantic, South Atlantic, North Pacific, South Pacific, Indian, and Southern oceans

3. Atmosphere – The Domain of Air

The atmosphere is divided into five layers and they are:

1. Troposphere (0 – 12 km): It is the lowermost layer of the earth’s atmosphere, and extends to an average of 12 km from the surface of the earth. Nearly all the water vapour and moisture found in the atmosphere lie in this section – the “troposphere”.

2. Stratosphere (12 – 50 km): It is the second-lowest section of the atmosphere, just after the troposphere, and is separated by the troposphere via the tropopause. The ozone layer of the earth is also included in this layer, the Ozone layer is filled with a high concentration of Ozone gas.

3. Mesosphere (50 – 85 km): Mesosphere is in the middle of the other atmospheric layers. In the mesosphere, the temperature dropped down by the increase in the altitude, this trend will then be followed by all the layers above it. It can be said to be one of the coldest places on the planet earth, with a temperature of – 85 °C (- 120 °F; 190 K). 

4. Thermosphere (80 km to 500 – 1000 km): This layer is the second-highest in the five atmospheric layers. It expands from the mesopause (which separates it from the mesosphere) all the way above to the thermopause (which cuts it from the exosphere). This is sometimes referred to as the exobase, as it lies just under the exosphere.

5. Exosphere (700 km to ~10,000 km): It is the outermost layer of the earth. It extends to 10,000 km outside the earth’s surface, after that it disappears in the solar wind. The main composition of this layer consists of extremely low densities of hydrogen and helium, some other molecules like traces of Nitrogen gas are also present in this layer.

About 99 per cent of the atmosphere is composed of nitrogen and oxygen where Nitrogen is 78 percent, oxygen is 21 per cent, and other gases comprise 1 per cent.

4. Biosphere – The Domain of Life

The biosphere is the zone of contact between land, water, and air. It is the zone where life exists and that is what makes this planet unique.

The organisms in the biosphere are divided into:

1. Plant kingdom

2. Animal kingdom