The thickest layer of the atmosphere is the troposphere, which averages 11 miles high at the equator and is thinner at the poles. All the weather occurs in this layer, and the troposphere contains nearly 80 percent of the air in the Earth's atmosphere. Above the troposphere, in ascending order, is the stratosphere, mesosphere, thermosphere and exosphere.
The stratosphere is about 20 miles thick and contains 19 percent of the Earth's air. The ozone layer exists in the stratosphere. The upper part of the stratosphere is warmer than the lower part because this layer blocks ultraviolet light.
The mesosphere averages a temperature of minus 180 degrees Fahrenheit. This layer extends to about 52 miles above the surface, and this is where most meteors vaporize in the upper part of the atmosphere.
The thermosphere, or ionosphere, is very warm due to heat absorption. However, humans would feel cold in this thin layer because there is not a lot of air in the thermosphere. When ionized particles interact with the thermosphere, the Northern Lights appear. This layer goes as high as 375 miles above the surface.
The outermost layer is the exosphere, which is where gas particles escape into outer space. Depending upon solar conditions, the exosphere extends outward from 620 miles to more than 6,200 miles.