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Educational Articles

Education Resource: The Structure of the Earth's Atmosphere

Earth's Atmosphere

The Earth is one of the planets in the solar system and it is surrounded by layers of gases, which is called the atmosphere of the Earth. The main function of this atmospheric layer is to protect the life forms on Earth by absorbing the harmful ultraviolet (UV) rays, infra-red rays, and gamma rays that are reflected from the sun. If there is no atmospheric layer above the Earth, then it will be easy for these harmful rays to reach the Earth and it will have destroyed all life forms on Earth. However, the greenhouse gases in the atmosphere protect the Earth from the UV and other rays, and this is called the Greenhouse Effect.

The atmospheric layer also regulates the temperature from becoming extreme. The atmosphere is comprised of distinct layers that have their own characteristics like temperature and composition. The most important part of the atmosphere is air, which is used for breathing and photosynthesis. The composition of dry air by volume is as follows: Oxygen – 20.95 percent, Nitrogen – 78.09 percent, Carbon Dioxide – 0.039 percent, Argon – 0.93 percent and also small amounts of other gases along with an average of 1 percent of water vapor.

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There are a number of layers in the atmosphere. The layers are as follows:

Troposphere

This is the layer which is just above the surface of the Earth. The troposphere extends about 9 km at the two Poles and 17 km at the Equator. The temperature of this layer is generally high because of the energy transfer that takes place from the Earth's surface. Generally, the lowest part of this layer is warmest and the temperature changes beyond this level. It is the thickest layer of the atmosphere, comprising almost 80 percent in terms of mass. The temperature averages about 15°C to -57°C in the tropopause.

  • The Earth's Atmosphere: An overview of the Earth's atmosphere with images and information about the troposphere.
  • Tropospheric Ozone: Provides information on the ground-level ozone, known as the polluter.
  • Troposphere: A look at the troposphere's structure and composition, chemistry, and more.
  • The Troposphere: Great place to learn about the troposphere with some questions at the end.

Stratosphere

This layer is the second layer above the Earth's surface and it extends up to 51 km from the troposphere. The most important layer of the stratosphere is the ozone layer, which is responsible for the absorption of the UV rays. Due to this phenomenon, the temperature of this layer increases as you go further up. The pressure of this part is 1/1000 and temperature can reach -78° C.

Mesosphere

This is the third layer of the Earth's atmosphere and it is above the stratosphere layer. This layer is about 80-85 km above the stratosphere level. The mesosphere protects the Earth from being hit by the meteors. Most of the meteors get burnt up in this layer. As you go up in this layer, you see a decrease in temperature. The mesosphere's top is regarded as Earth's coldest place, where the temperature is -85°C. This is called mesopause or the temperature minimum. At certain times, the temperature at the mesopause may drop to -100°C. This is the place where water vapor freezes to form ice clouds.

  • Mesosphere and Mesopause: A description of the mesosphere and mesopause with a graph.
  • Coupling Study: Details of a study on the mesosphere and lower thermosphere.
  • Atmosphere: An overview of the Earth's atmosphere including the mesosphere.

Thermosphere

This is the fourth layer of the Earth's atmosphere. Temperature increases as you go up in this layer. The increase of the temperature occurs from the mesopause to thermopause after which it remains constant. This layer's temperature may rise up to 1500°C. The International Space Station is orbiting the Earth in this layer.

Exosphere

This is the outermost layer of the Earth's atmosphere. The layer is mainly composed of hydrogen and helium. In this layer, the particles are far apart from each other for hundreds of kilometers. Due to the non-collision of the particles, the exosphere does not behave like a fluid. Moreover, the free-moving nature of the particles makes them follow ballistic trajectories and allow them to move in and out of the magnetosphere. The temperature in this layer can reach -90°C.

  • Atmospheric Structure: Great discussion of the atmospheric structure including the exosphere.
  • Geocorona: Describes the solar far-ultraviolet light reflected off the exosphere.
  • Heavy Atoms: The PDF reports on heavy atoms found in the exosphere.
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