Layers of Atmosphere - Definition, Composition, Diagram, FAQs

The atmosphere is the layer of air that surrounds the Earth. It protects life, controls the weather, and keeps the planet warm. It is made of gases like nitrogen, oxygen, carbon dioxide, and others. An envelope of air surrounding the earth is known as the atmosphere. The atmosphere extends up to a distance of 32,000km. It is the most important part of our environment. The atmosphere is an essential part of our biosphere as its composition is responsible for changes in weather and climate on our planet and other life-supporting systems. Let's explore the Layers of Atmosphere in detail.

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This Story also Contains

1. Layers of the Atmosphere
2. Troposphere
3. Stratosphere
4. Mesosphere
5. Thermosphere
6. Exosphere

Layers of the Atmosphere

The structure of the atmosphere consists of five layers. Each layer has its characteristics. Let's discuss each layer in detail.

1. Troposphere
2. Stratosphere
3. Mesosphere
4. Thermosphere
5. Exosphere

Troposphere

It is the lowest layer of the atmosphere having 75% of the total weight of the atmosphere. It is 10 km thick at the poles and 18km thick at the equator. There is a 1°C temperature fall with a 165m increase in altitude. This is known as the normal lapse rate.

The term “Tropo” means change. Most of the weather phenomena take place in the troposphere such as dust, storm, rainfall, snowfall, etc. In this layer, we also see twilight, sunrise, sunset, and scattering of light. The troposphere is the hottest part of the atmosphere because it absorbs the highest amount of solar energy emitted by the rocks, mountains, and water on the earth.

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Stratosphere

Stratosphere is the second layer of the atmosphere, next to the troposphere. It extends up to 3km above the surface of the earth. It is a calm and clean sphere. The absence of water vapours prevents the formation of clouds, hence providing very clear visibility. This sphere is also free of air pocket, i.e., pilots prefer to fly in this sphere, we also see the formation of mother of pearl cloud or nacreous cloud.

The ozone layer is found in the stratosphere. It is around 15-30km above the earth. There is plenty of ozone gas in this sphere, Hence it is known as the ozonosphere. Ozonesphere is very useful because it absorbs the ultraviolet radiations of the sun and protects life on the earth. We cannot live up to five minutes if the ozone layer is destroyed.

Mesosphere

It is the third layer next to the stratosphere. The mesosphere characteristics by low atmospheric pressure and low temperature. The temperature begins to drop from stratopause, goes on decreasing with the increase in height, and reaches a minimum of about -95℃ at a level of about 60km above the earth’s surface. At an 80-90 km altitude menopause separates the mesosphere from the thermosphere. But decreases in temperature in the mesosphere are due to some gas molecules present in the mesosphere that absorb the radiation of the sun hence, Mesosphere is the coldest layer of the atmosphere.

Why Mesosphere is the coldest layer of the atmosphere?

The mesosphere is the coldest layer of the atmosphere because the air is extremely high in this layer and it has little capacity for retaining heat. The heat transfers from surface to space at a much faster rate than it heats up by the Sun’s rays. Therefore, the temperatures here in this layer are normally as low as -90°C which is the lowest temperature for any atmospheric layer.

Thermosphere

It is the fourth layer next to the mesosphere. In this sphere due to the absorption of energetic ultraviolet and X-ray radiation from the sun temperature increases. The temperature of the thermosphere increases with height and it can rise as high as 1500 °C. It consists of a large part of the ionosphere. It extends about 80km above sea level. At an altitude range of 500–1000 km, thermopause separates the exosphere from the thermosphere. The thermosphere is the hottest layer of the atmosphere.

Why thermosphere is the hottest layer of the atmosphere?

This layer is the nearest to the Sun’s energy and hence it captures and absorbs heat most. As a result, most of the solar radiations that include X-ray and ultraviolet rays are present, and thus the thermosphere is the warmest layer of the atmosphere.

Ionosphere

The ionosphere is not a separate layer but a region within the thermosphere and partially in the mesosphere. It spans from about 50 km to 1,000 km above Earth's surface.

It extends from 60 to 500km. Due to the presence of ions - electrically charged particles it is called the ionosphere. It reflects radio waves back to the earth which helps in wireless communication. It also absorbs X-rays emitted from sun rays. In this sphere, temperature increases with height because of the radiation from the sun.

Exosphere

The exosphere is the outermost layer of the Earth's atmosphere. It provides space for interplanetary happenings. It ranges from 500 km to 1,000km above the earth. This part gradually merges with the outer spaces.

How to memorize seven layers of earth?

To remember all the layers of the atmosphere in ascending order from the earth’s surface to the space you can use the following mnemonic. Each word corresponds to a specific layer, starting from the lowest to the highest:

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• T - Troposphere
• S - Stratosphere
• M - Mesosphere
• T - Thermosphere
• E- Exosphere