Layers Of Atmosphere And Its Composition

Atmosphere refers to the layer of gases that surrounds a planet or body. It is an envelope of gases that extends from a planet’s land, ocean, and ice-covered surface to the outward space. Moreover, it is the gravitational power of a body that holds the atmosphere in place.

In the solar system, the only planet with a life-sustaining atmosphere is the Earth. The atmosphere on Earth protects life on earth and is also known as air. It creates pressure on Earth, allowing liquid water to exist and also absorbs the ultraviolet solar radiation. It also provides warmth to the planet during the day and coolness at night.

Composition of the atmosphere

The atmosphere of the Earth is about 480 kilometres (300 miles) thick, while most of it lies within 16 kilometres (10 miles) of the surface. The atmosphere consists of a mixture of many different gases. The main components of the Earth’s atmosphere are oxygen, nitrogen, argon, carbon dioxide, and other gases. These are permanent gases and their percentages remain fixed in the atmosphere.

* Nitrogen: Nitrogen contributes to 78.08% of the air on Earth. It is odourless, colourless, and considered as an inert gas.
* Oxygen: The Earth’s atmosphere is made up of 20.95% of oxygen. It is generated as a result of photosynthesis by plants.
* Argon: Argon is the third noble gas and constitutes to about 0.93% of the atmosphere. It is colourless, odourless, and chemically inert.
* Carbon dioxide: Carbon dioxide consists of 0.04% of the Earth’s atmosphere. It occurs naturally and is considered a trace gas.

Neon, methane, helium, hydrogen, krypton, nitrous oxide, carbon monoxide, iodine, and ammonia are also present in the atmosphere as trace gases. Additionally, water vapour is present at lower altitudes. It is unique as its concentration varies depending on the place and time of the day. Then there are greenhouse gases with a variable percentage.

Layers of the atmosphere

The atmosphere of the earth can be divided into five major layers, namely exosphere, thermosphere, mesosphere, stratosphere, and troposphere. An imaginary line, known as the Karman line divides the atmosphere and space as there is no such distinct boundary. With each layer, the atmosphere continues to go thinner and thinner.

Troposphere

The troposphere consists of 75 % of the atmosphere. It refers to the layer closest to the surface of the Earth and forms the lowest part of the atmosphere. It consists of most of our rain, cold, and snow. In this layer of the atmosphere, the temperature decreases with the increase in the distance above the Earth.

The troposphere extends from about 7 kilometres to 20 kilometres above the Earth’s surface. All the water vapour and dust particles are present in this layer. The topmost part of the troposphere is called the tropopause, while the lowest part is known as the boundary layer.

Stratosphere

The stratosphere extends from the end of the troposphere to about 50 kilometres (31 miles) above the ground. Most of the ozone is present in this layer. The temperature increases with the increase in height as the ultraviolet rays of the sun are absorbed by the ozone gas present in this layer. Thus, the ozone in this layer protects us from numerous health damages, including skin cancer.

Chemicals such as halons, CFCs, or freons reduce the amount of ozone present in this layer. The air present in this layer is very dry & thin and creates very stable atmospheric conditions. Thus, jet aircraft and air balloons fly in this layer.

Mesosphere

Mesosphere refers to the layer above the stratosphere. In this layer, the temperature decreases with the decrease in height and reaches a minimum of minus 90-degree Celcius. The topmost layer of the mesosphere is known as the mesopause. It is the coldest part of the atmosphere.

The Mesosphere starts from 50 kilometres above the ground and extends up to 85 kilometres in height. Weather balloons and jets cannot fly in this layer. The traits of this layer cannot be measured as satellites orbit above this layer. Most of the meteors vaporize or burn in this layer.

Thermosphere

The thermosphere extends from 90 kilometres above the ground and extends up to 500 to 1000 kilometres. In this layer, the temperature can reach up to 1500 degree celsius. Most of the thermosphere is considered outer space as the air density in this layer is very low.

Space shuttles and the International Space Station orbits the Earth in this layer. Even the auroras occur in the thermosphere. In this layer, molecules and atoms collide with the charged particles present in the space. This excites them into higher state energy.

Exosphere

The exosphere refers to the highest layer of the atmosphere which gradually fades into the outer space. It is present above 500 km of the earth’s surface. The air present in the exosphere is very thin and thus makes it similar to the airless void in outer space. In most cases, the exosphere is not considered a real part of the atmosphere.

The bottom of the exosphere is known as exobase. Since it merges with outer space, there is no upper boundary in this layer. Also, there are no collisions in this layer of the atmosphere. Many satellites such as the ISS or the International Space Station orbit within or below this layer.

Conclusion

These were the five main layers of the Earth’s atmosphere along with their spread, temperature variance, and other traits. As for the secondary layers, the ozone layer is found within the stratosphere, whereas the Ionosphere stretches from the thermosphere, mesosphere, and exosphere, the planetary boundary layer is also a part of the troposphere, and the Homosphere and Heterosphere are also present in the atmosphere.