The Earth is divided into three main domains—lithosphere, atmosphere, and hydrosphere. The sphere of the Earth where all these three domains interact with each other is known as the biosphere. The blanket of air that surrounds the Earth is known as the atmosphere. The atmosphere exists in the gaseous state. Oxygen present in the atmosphere is one of the life-sustaining elements present on the Earth. The structure of the atmosphere is a combination of various layers or strata.
Structure of the Atmosphere
The structure of the Atmosphere is divided into five layers beginning from the surface of the Earth.
- It is the most important layer of the atmosphere. It extends up to 13 km from the surface of the Earth. The oxygen which we breathe exists in this layer of the Earth.
- The temperature decreases in this layer with the increase in height.
- All the weather phenomena such as rainfall, hail, and fog occur here as the clouds are formed in this layer.
- The upper limit of the troposphere is known as tropopause. The temperature may be as low as −58°C at this level.
- This layer of the atmosphere lies above the troposphere and extends up to the height of 50 km.
- Aeroplanes fly in this layer, as this layer is free from clouds and other weather phenomena. This layer is also free from water vapour and dust particles.
- The stratosphere contains a layer of ozone gas that protects us from the harmful ultraviolet rays of the Sun.
- In the higher levels of the stratosphere, the temperature increases with height because of the absorption of ultraviolet rays by ozone in the layer.
- The upper part of the stratosphere is known as the stratopause.
- This is the third layer of the atmosphere and it lies above the stratosphere up to the height of 80 km.
- It is in this layer that the meteorites burn when they enter the atmosphere from space.
- The upper layer of the mesosphere is known as mesopause.
- Thermosphere or Ionosphere
- This layer extends from 80 to 400 km.
- The temperature increases drastically in this layer and can go up to 1,480°C. It is because the molecules in this layer absorb the Sun’s ultraviolet rays.
- The thermosphere helps in the transmission of radio waves as the latter is reflected the Earth by this layer.
- The thermosphere lies above the mesosphere.
- This layer extends to a height of about 640 km.
- In this layer temperature rises dramatically, reaching up to 1480°C.
- This increase in temperature is due to the fact that the gas molecules in this layer absorb the X-rays and ultraviolet radiation of the Sun.
- This results in the break up of the gas molecules into positively and negatively charged particles or ions. Thus, this layer is also known as the ionosphere.
- The electrically charged gas molecules of the thermosphere reflect radio waves from the Earth back into space. Thus, this layer also helps in long-distance communications.
- The thermosphere also protects us from meteors and obsolete satellites, because its high temperature burns up nearly all the debris coming towards the Earth.
- It is the uppermost layer of the Earth. It has a very thin layer of air.
- Light gases such as helium and hydrogen float into space from this layer because of the lack of gravity.
- This layer extends from 480 to 960 km above the Earth.
- Temperature increases with height in this layer. The temperature may well go beyond 5,500°C
Also, Read The Atmosphere