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• Gas Composition of the Atmosphere

  • Nitrogen 78%
  • Oxygen 21%
  • Argon 0.9%
  • Carbon Dioxide 0.03%
  • Water Vapor 0.0 to 4.0%
  • Trace gases (neon, helium, krypton, xenon)
• Nitrogen


  Dilutes oxygen and prevents rapid burning at the earth's surface. Living things need it to make proteins. Nitrogen cannot be used directly from the air. The Nitrogen Cycle is nature's way of supplying the needed nitrogen for living things.
• Oxygen


  Used by all living things. Essential for respiration. It is necessary for combustion or burning.
• Argon


  Used in light bulbs.
• Carbon Dioxide


  Plants use it to make oxygen. Acts as a blanket and prevents the escape of heat and oil are adding more carbon dioxide to the atmosphere.
• Water Vapor


  Essential for life processes. Also prevents heat loss from earth.
• Trace gases


  Gases found only in very small amounts, including neon, helium, krypton, and xenon.
• Atmospheric Layers

  1. Troposphere (0-16km)

  2. Stratosphere (16-50km)

  3. Mesosphere (50-80km)

  4. Thermosphere (80-640km)

  5. Exosphere (640+km)
• Troposphere


  • First layer above the surface, contains half of the Earth's atmosphere, weather occurs in this layer, air is constantly moving, lowest at poles (5km) and highest at equator (16km)
• Stratosphere


  • Very stable, ozone layer absorbs harmful rays from the Sun
• Mesosphere


  • Meteors or rock fragments burn up in this layer
• Thermosphere


  • Layer with auroras, where the space shuttle orbits, different regions of the ionosphere (extension of thermosphere) make long distance radio communication possible
• Exosphere


  • Outermost layer of the earth's atmosphere, satellites are stationed here
• Temperature in the Atmospheric Layers

  1. Troposphere: temperature decreasing with height

  2. Stratosphere: temperature increasing with height

  3. Mesosphere: temperature decreasing with height

  4. Thermosphere: temperature increasing with height

  5. Exosphere: temperature increasing with height
• The air at the surface up to around 16km is called the troposphere. The reason it is warmer at the surface is that the air is warmed by heat given off by the earth. The farther away from the surface the air moves, the less heat there is to absorb.
• In the stratosphere from 16 to 20km the atmosphere is stable. From 20 to about 50km in this region the air actually warms with height. Ozone is concentrated in this part of the atmosphere and it absorbs ultraviolet light from the Sun. More light is absorbed at higher altitudes compared to the lower stratosphere, so the temperature increases.
• In the mesosphere, which begins at about 50km, the temperature decreases with height again, because there is very little ozone to warm up the air.
• In the thermosphere, which is the section of the atmosphere higher than 80km, the temperature increases again. This time, it is molecular oxygen (O2) that causes the temperature increases. The oxygen absorbs light from the sun, and since there is very little air in the thermosphere, just little absorption can go a long way.
• The exosphere is almost a vacuum. The "air" is very, very thin there. When air is thin, it doesn't transfer much heat to objects in the air, even if the air is very, very hot.