composition of the atmosphere
air shell of the Earth arose a very long time - about four billion years ago.In fact, it was formed from volcanic gases.Current live organisms could not breathe in this air.
for the existence of life on our planet a very important role played by gases such as oxygen, water vapor, ozone and carbon dioxide.They are present in the composition of the atmosphere.If we talk about oxygen, its stocks are constantly replenished by plants.Accumulation of carbon dioxide takes place as a result of respiration of living organisms combustion.Also, carbon dioxide is produced in large quantities after volcanic eruptions.For ozone, it usually occurs under influence of electric discharge from oxygen.The proportion of ozone in the atmosphere is very low.
Currently, the main share of the air represented by such gases as nitrogen and oxygen, and their percentage of all differently.The content of water vapor in the air under certain conditions can lead to the formation of clouds and fog.Incidentally it is the number of water vapor depends on the weight of the air.
Unfortunately, the air of large cities also has a significant amount of harmful impurities (carbon monoxide, methane).They cause irreparable damage to the modern biosphere.
If we talk about the structure of the atmosphere, it is characterized by heterogeneity.It can distinguish the layers that have their own characteristics.The lowest layer is considered dense and toposfera.It accounts for about 4/5 of all air.It is the formation of tropospheric clouds and the constant movement of air.Here it flows and human life.The maximum thickness of the troposphere can reach 17 kilometers.
above is a layer called the stratosphere.In the stratosphere, the air is more rarefied and virtually no water vapor.Here, at an altitude of 20 kilometers of the ozone layer is formed.Above the stratosphere is the mesosphere is characterized by even lower density of air.Next is the thermosphere.It is in this layer is formed by so-called aurora.Thermosphere also has the highest level of temperature to 1500 ° C.Finally, the top layer of the atmosphere is considered to exosphere.The shape of its borders different scattering.