# What is Atmosphere? - Layers, Gases & Pressure

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• 0:01 Layers of the Atmosphere
• 2:39 Gases of the Atmosphere
• 2:58 Pressure of the Atmosphere
• 3:43 Lesson Summary

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Lesson Transcript
Instructor: Jeff Fennell

Jeff has a master's in engineering and has taught Earth science both domestically and internationally.

The atmosphere surrounds us wherever we go and is necessary for our survival. This lesson will cover the properties and layers of the atmosphere. After completing the lesson, test your knowledge with a short quiz.

## Layers of the Atmosphere

Our atmosphere is the layers of gases surrounding the earth. The atmosphere may just look like one vast blue thing above, but a lot happens up there. The atmosphere is broken down into five layers, each with its own characteristics and properties.

Of all the layers of the atmosphere, it's the troposphere that we experience. The air we breathe and weather we complain about: it all occurs in the troposphere, which begins at the surface and extends 5 to 10 miles up into the atmosphere. As altitude increases in the troposphere, the temperature decreases. Much of the lower layer is heated up by the heat of Earth's surface. The rising hot air can, and often does, cause turbulence throughout the troposphere. Another example of weather in the troposphere is that most of the water vapor and dust particles in the atmosphere are found in the troposphere which, as you can probably guess, causes rain.

Next we have the stratosphere. The beginning of the stratosphere varies around the earth due the difference in centripetal force from rotating. Near the poles, the stratosphere begins 5 miles above the surface, while down at the equator, it starts higher up at 10 miles (8 and 16 km). It's in the stratosphere that three oxygen atoms combine to form the ozone layer. The ozone layer absorbs most of the sun's ultraviolet rays (which are harmful to us) which heat up the stratosphere. The stratosphere is a very stable layer, and not much weather occurs in it. For this reason, most planes fly in the lower part of the stratosphere.

Next up, the mesosphere starts just above the stratosphere, 31 miles (50 km) above the surface and extends up to 53 miles (85 km). The mesosphere is the coldest layer of the atmosphere with temperatures averaging -130° F (-90° C). Most of the meteors that burn up in the atmosphere do so in the mesosphere. So if your next shooting star wish comes true, you can thank the mesosphere for helping.

Above the mesosphere is the thermosphere, which extends from 53 - 621 miles (90 - 1,000 km) up into the atmosphere. Direct heat from the sun causes the temperature of the thermosphere to rise sharply. Temperatures here can get up to 932° F (500° C), and yet, even with these temperatures, most satellites, including the International Space Station, orbit in the thermosphere.

Finally, the exosphere is the uppermost layer of the atmosphere. This is where the atoms and molecules escape Earth's gravity into space.

## Gases of the Atmosphere

While oxygen is important for most animals to survive, it is nitrogen that makes up most of the atmosphere. The composition of the atmosphere is broken down as:

• 78% nitrogen
• 21% oxygen
• 0.9% argon
• <0.1% other gases

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