Earth's Atmosphere

Earth's atmosphere consists of layers of many different gases that surround the Earth and eventually start to dissolve into space roughly 348 miles away from Earth's surface. Our atmosphere provides us with the air and protection that we need in order to survive.

 

 

You might be surprised to learn that oxygen is not the major component of the earth's atmosphere. The atmosphere consists of 78 percent nitrogen, followed by nearly 21 percent oxygen. The other components of the atmosphere include:

The troposphere, the layer of atmosphere in which we live and breathe, starts at the Earth's surface and extends upwards about five to nine miles. Named from the Greek word "tropein," meaning "to turn" or "change," the troposphere hosts all of our weather. In general, temperature decreases with altitude in the troposphere, starting at an average of 59ºF on the ground and ending at an average of about -71ºF at the outer edge of the troposphere.

 

Less moisture exists at the edge of the troposphere than at Earth's ground level. The amount of available oxygen and air pressure also decreases with height. The tropopause is a "thin" boundary region that separates the troposphere from the stratosphere. Together, the troposphere and the tropopause are often called the lower atmosphere.

 

The second level of Earth's atmosphere is the stratosphere.It ends about 31 miles above the surface of the Earth. Unlike the troposphere, the temperature in the stratosphere actually increases with altitude, reaching almost 27ºF at its highest point. Many jets fly in the stratosphere, as the air is much more stable there than in the troposphere.

 

The stratosphere contains almost 90 percent of the ozone in the atmosphere. The ozone layer in the stratosphere helps to protect the Earth from the Sun's harmful ultraviolet rays by absorbing them and scattering the radiation. Like the troposphere, the stratosphere has a buffer region called the stratopause, which separates the stratosphere from the mesosphere.

 

The next layer of the atmosphere is known as the mesosphere, named after the Greek word for "middle."The mesosphere, which ends about 53 miles above the Earth, also has lower temperatures, reaching -135ºF. In the mesosphere, meteorites are usually destroyed before reaching the Earth. The boundary region of the mesosphere is called the mesopause. The mesosphere and stratosphere together are called middle atmosphere.

 

The altitude of the thermosphere reaches to about 372 miles above the Earth's surface. Temperatures in the thermosphere increase with altitude and can reach over 3,000ºF. The thermosphere contains the ionosphere, where air molecules are ionized by the power of the sun's radiation, creating electrically charged particles. Auroras occur in the thermosphere. The thermosphere is also known as the upper atmosphere.

 

The exosphere is the final layer of Earth's atmosphere. Gases in the exosphere, such as atomic oxygen, carbon dioxide, helium and hydrogen, can migrate into space from this layer.

 

 

NASA (2003). Earth's Atmosphere. Retrieved January 21, 2008, from the NASA.gov Web site: http://www.nasa.gov/audience/forstudents/9-12/features/912_liftoff_atm.html.

 

University Corporation for Atmospheric Research (n.d.). Introduction to the Atmosphere. Retrieved January 21, 2008, from the UCAR Web site: http://www.ucar.edu/learn/1_1_1.htm.

University Corporation for Atmospheric Research (n.d.). Ozone in the Stratosphere. Retrieved January 21, 2008, from the UCAR Web site: http://www.windows.ucar.edu/tour/link=/earth/Atmosphere/
ozone_strato.html.

University Corporation for Atmospheric Research (n.d.). The Troposphere. Retrieved January 21, 2008, from the UCAR Web site: http://www.windows.ucar.edu/tour/link=/earth_science/
Atm_Science/Temp_structure/structure_tropo.html.