THE ATMOSPHERE (chapter 24.1)

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THE ATMOSPHERE(chapter 24.1)
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• ATMOSPHERE - the layer of gases that surrounds
  the Earth. The atmosphere forms a protective
  boundary between the Earth and space which
  provides conditions suitable for life...
• protects Earths surface from meteorites and
  space debris as well as high energy radiation
• holds in heat and moderates Earths temperature
• provides gases essential for life (oxygen,
  nitrogen, carbon dioxide)

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• AIR PRESSURE - the force exerted by the weight of
  a column of air on a surface
• air pressure changes with altitude - as the
  altitude increases, the depth of the column of
  air above decreases, so the pressure decreases
• As the altitude increases, air pressure and
  density decrease
• air pressure is measured with a barometer

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• Scientists use variations in temperature to
  divide the atmosphere into four vertical
  layers...
• 1. TROPOSPHERE (0-12 km)- lowest layer of the
  Earths atmosphere - contains almost all of the
  atmospheres water vapor which are important in
  the formation of clouds and precipitation
• weather - the condition of the atmosphere in a
  particular place at a particular time
• temperature decreases as altitude increases

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• 2. STRATOSPHERE (12-50 km)- layer above the
  troposphere
• temperature fairly constant up to 20 km -
  temperature increases with altitude (-57 - 0C)
• the upper stratosphere is warmer than the lower
  due to the ozone layer - a region of high ozone
  concentration - ozone in a highly reactive gas
  composed of three oxygen atoms

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• 3. MESOSPHERE (50-80 km)- layer above the
  stratosphere
• temperature decreases as altitude increases
• meteoroids that enter the atmosphere burn up in
  the mesosphere

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• 4. THERMOSPHERE (gt80 km)- outermost layer of
  the atmosphere
• temperature increases rapidly with altitude (gas
  molecules in the thermosphere absorb solar
  radiation and move very fast, the temp is very
  high)
• ionosphere - not a distinct layer of the
  atmosphere - region of charged particles / ions
  that overlaps the lower thermosphere

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• The aurora occurs in the ionosphere
• a colorful display of light produced when charged
  particles from the sun are attracted to the
  Earths magnetic poles
• the particles cause ions in the ionosphere to
  glow