Layers of the Earth’s Atmosphere



Earth’s atmosphere is a blanket of gases made out of 78% Nitrogen, 21% Oxygen, and 1% Argon. The other trace gases present in atmosphere are Carbon Dioxide, Hydrogen, Neon, Helium, Krypton, and Xenon. Water vapor dislodges other gases and varies from almost zero to around 4% by volume. The atmosphere lays on Earth’s surface with a weight equal to a layer of water 34 ft deep. The gases stay in the proportion stated above,for around 300,000 ft upward from the surface of earth. Gravity holds the gases to Earth. The weight of the air compresses it at the base thus the greatest density of earth atmosphere is at Earth’s surface. Pressure and density decrease as height increases.


The lowest layer of the air reaching out up from the Earth’s surface around 7.5 mi is the troposphere, which contains 90% of the air. This is also where most weather phenomena occur. In troposphere the temperature drops with increase in height.


The stratosphere reaches out around 23 mi over the troposphere. In this layer, the temperature for the most part increases with the increase of height. The stratosphere contains ozone, which keeps UV radiation from reaching Earth’s surface and thus protect life on Earth. Since there is next to no convection in the stratosphere, Aeroplanes regularly fly in the lower parts of stratosphere to give a smoother ride to passengers.


The layer above stratosphere is mesosphere. Here in this layer, temperature again decreases with increase in height for another 19 miles.


Stretching out over the mesosphere to the external edges of the atmosphere is the thermosphere, a region where temperature once more increases with height to a value measured in thousands of degrees Fahrenheit. The lower portion of this region, extending from 50 to about 400 mi in altitude, is characterized by high ion density and is thus called the ionosphere. Most meteors are in the lower thermosphere or the mesosphere at the time they are observed.


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