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Composition of Earth’s Atmosphere

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  • Last Updated : 01 Jun, 2022
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The word atmosphere comes from the Ancient Greek word “atmos”, which means vapor or steam, and sphaira which means sphere. It can be called as the layer of gases surrounding any planet and it is held together by the Gravity of the planet. Around the planet, it is a mixture of gases. It is one of the reasons why we are able to survive on this planet. The earth’s atmosphere also helps us prevent the large difference in temperature during day and night.

The high gravity and low temperature of planets like Jupiter, Saturn, and Neptune help this planet retain molecules with low molecular mass to be stable in the atmosphere.

Composition of the atmosphere 

The composition of the earth’s atmosphere is due to the by-product of the life it holds. As the activities of humans have a great impact on the composition of  Earth’s atmosphere which goes up to 10,000 kilometers above the ground beyond which it, merges into space. Oxygen is one of the most important gas for the survival of humans but it is a very small part of the gases present in the atmosphere as it is only 21 percent of the total gases present. It is a very common misconception that trees or forests are the main sources of oxygen but oceans are the main source of oxygen. 

Nitrogen is the gas that is found mostly in the atmosphere covering up to 78 percent. The rest of the gases together make up to  1 percent of the atmosphere which includes 0.93 percent argon and 0.04 percent carbon dioxide and many other gases. The percentage of carbon dioxide has been increasing throughout the years due to the activities of humans. Though the composition of Carbon Dioxide may seem very low from the figures it is on a constant rise and it is of huge danger to humans as it has been the reason for the constant increase in the earth’s temperature and causing a greenhouse effect. The increase in the level of carbon dioxide is due to the increased emissions of vehicles and industries. The 1 percent also contains water vapors, helium, and other noble gases. 

The amount of water present in the atmosphere is very less and is dependent on a number of factors. It is mostly absent in the atmosphere but the concentration is high where the climate is humid. Though it is very less in quantity it is the most important part of the atmosphere other than oxygen. While a lot of gases are present in the atmosphere the number of suspended particles can’t be neglected. The suspended particles are called Aerosols .it may include soil from desert salt particles due to the evaporation of salt water, plant pollens, and a lot more particles. When a volcano eruption takes place the fine particles of lava or magma are suspended in the air . They have a huge impact on the atmospheric heat balance, cloud formation, and many more properties.

Based on the temperature and the gases present in the atmosphere it is divided into 5 layers namely, Troposphere, Stratosphere, Mesosphere, Thermosphere, and exosphere.

Troposphere 

It is the lowest layer in the earth’s atmosphere. and closest to the ground. It reaches 15 kilometers from the earth’s surface. Almost 75 percent of the mass of the atmosphere is from this part due to the heavy gases. The troposphere is found to be thick at the equator and thin at the north and south poles due to the difference in Gravity at the poles and the equator. The clouds are found in the area and so does all the activities of weather. Air is warmer at the bottom and as the height increases the temperature decreases this is true not only for the Troposphere but also for most of the other layers. 

Stratosphere 

It is the layer directly above the Troposphere. It reaches from the top of the troposphere to  50 kilometers above the ground. It has the highest concentration of oxygen and even the ozone layer is present in the stratosphere. The ozone layer is very important for the survival of humans as it protects us from the harmful UV rays emitted by the sun and prevents various health diseases like skin cancer etc.

Mesosphere 

It is the layer above the stratosphere and is about 83 kilometers above the Stratosphere. The concentration of oxygen and nitrogen is high in this layer and the concentration of water vapor is almost null. The Temperature decreases with the increase in altitude till this point in the atmosphere, the coldest point in the earth’s atmosphere is at the top of the Mesosphere. The reason it increases after this point is that the gases above it absorbed solar radiation It is also the place where most meteors burn up before reaching the ground.

Thermosphere

It is the layer above the Mesosphere and reaches from the top of the Mesosphere to 600 kilometers above the earth’s surface. The temperature of this region is generally very high due to the absorption of solar radiation emitted by the sun, which can go up to 2,000 degrees. Atomic oxygen takes up most of the area at this level and is present in its lone form as an atom.

Exosphere

It is the layer above the Thermosphere. It is the uppermost layer in the earth’s atmosphere. Due to very low gravity, the gas molecule escapes into outer space. The air in this layer is extremely thin and it merges with the space in the end.

Sample Questions 

Question 1: What is the composition of the atmosphere?

Answer:

The atmosphere is about 78 % nitrogen, 21 % oxygen, and 1% other gases which include carbon dioxide, and water vapor, While a lot of gases are present in the atmosphere the number of suspended particles can’t be neglected. 

Question 2: In which layer is the Ozone found and what is its function?

Answer:

It is present in the stratosphere. The ozone layer protects us from the harmful UV rays emitted by the sun and prevents various health diseases.

Question 3: In what ways do Aerosols affect the atmosphere?

Answer:

 It includes soil from deserts salt particles due to the evaporation of salt water, plant pollens, and a lot more particles. They have a huge impact on the atmospheric heat balance, cloud formation, and many more properties.

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