Layers of the Atmosphere

1
Layers of the Atmosphere

• What are the parts of Earths atmosphere?
• The atmosphere has several layers. These layers
  differ in temperature, in density, and in the
  relative amounts of the different gases that are
  present.
• troposphere
• stratosphere
• mesosphere
• thermosphere
• The two main gases in the atmosphere are nitrogen
  and oxygen.

2
Layers of the Atmosphere, continued
3
Layers of the Atmosphere, continued

• Almost all weather occurs in the troposphere.
• The troposphere is the atmospheric layer closest
  to Earths surface.
• The troposphere is the densest layer.
• Troposphere the lowest layer of the atmosphere,
  in which temperature drops at a constant rate as
  altitude increases

4
Layers of the Atmosphere, continued

• The troposphere gets cooler with increasing
  altitude.
• The temperature decreases by 6 C for every
  kilometer of altitude.
• At the top of the troposphere the temperature
  stops decreasing.
• The boundary where this occurs is called the
  tropopause.
• The temperature at the tropopause is -55 C.
• The low temperature keeps water vapor in the
  troposphere.

5
Layers of the Atmosphere, continued

• The stratosphere gets warmer with increasing
  altitude.
• stratosphere the layer of the atmosphere that
  lies between the troposphere and the mesosphere
  and in which temperature increases as altitude
  increases contains the ozone layer
• At about 25 km, the temperature begins to
  increase with altitude until it reaches about 0
  C.
• The stratosphere contains few clouds and no
  storms.
• The ozone layer shields living things on Earths
  surface from ultraviolet-radiation damage.

6
Layers of the Atmosphere, continued

• The mesosphere and thermosphere exhibit extremes
  of temperature.
• mesosphere the coldest layer of the atmosphere,
  between the stratosphere and the thermosphere, in
  which temperature decreases as altitude decreases
• Temperatures in the mesosphere decrease to about
  -80º C.
• thermosphere the uppermost layer of the
  atmosphere, in which temperature increases as
  altitude increases
• Temperatures average about 980 C (1,796 F)
  because the small amount of oxygen absorbs
  intense solar radiation.

7
Layers of the Atmosphere, continued

• The ionosphere is important to radio
  communication.
• When solar energy is absorbed in the lower
  thermosphere and upper mesosphere, charged ions
  are formed.
• This layer is often called the ionosphere.
• Radio waves are reflected in the ionosphere.
• Auroras take place in the ionosphere.

8
Changes in Earths Atmosphere

• Where did Earths atmosphere come from?
• When Earth began to solidify, about 4.4 billion
  years ago, volcanic eruptions released a variety
  of gases.
• The process of releasing gases during volcanic
  eruptions is called outgassing.
• The gases released by volcanoes did not include
  oxygen.

9
Changes in Earths Atmosphere, continued

• Photosynthetic plants contribute oxygen to the
  atmosphere.
• Organisms evolved photosynthesis, a method of
  capturing energy from the sun.
• Photosynthesis produces oxygen as a waste
  product.
• Gradually the oxygen content increased to what it
  is today.

10
Changes in Earths Atmosphere, continued

• Animals produce carbon dioxide necessary for
  photosynthesis.
• Oxygen breathing organisms evolved and released
  carbon dioxide as a waste product.
• The oxygen-carbon dioxide cycle maintains a
  balance of atmospheric gases on Earth.

11
Changes in Earths Atmosphere, continued

• Human-made chemicals can deplete the ozone layer.
• Ozone forms when the suns ultraviolet rays
  strike molecules of O2.
• Ozone absorbs much of the suns ultraviolet
  radiation.
• Without the ozone layer, ultraviolet radiation
  would damage living cells.
• Chlorofluorocarbons, CFCs, are chemicals that
  destroy the ozone layer, but are now banned in
  most countries.

12
Changes in Earths Atmosphere, continued

• The greenhouse effect keeps Earth warm.
• greenhouse effect the warming of the surface and
  lower atmosphere of Earth that occurs when carbon
  dioxide, water vapor, and other gases in the air
  absorb and reradiate infrared radiation
• Greenhouse gases trap the suns heat and keep
  Earths surface warm.

13
Greenhouse Effect
14
Changes in Earths Atmosphere, continued

• Too much carbon dioxide may cause global warming.
• If too much energy is absorbed by the atmosphere,
  global temperatures will rise.
• Global warming could cause problems, such as
  rising ocean levels, because of melting polar
  icecaps, and droughts.
• Combustion of coal, oil, and gas has added more
  carbon dioxide to the air.

15
Changes in Earths Atmosphere, continued