The Ozone Layer and the Atmosphere

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The Ozone Layer and the Atmosphere
By Alastair McNair
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The Structure of the Atmosphere

• There are four layers of the atmosphere
• The Thermosphere, is the highest above the
  ground.
• The Mesosphere is below the the Thermosphere.
• The Stratosphere is below the Mesosphere.
• And the Troposphere is the closest to the earths
  crust.

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What the atmosphere is made of
The atmosphere is primarily composed of Nitrogen
(N2, 78), Oxygen (O2, 21), and Argon (Ar, 1).
A myriad of other very influential components are
also present which include the water (H2O, 0 -
7), "greenhouse" gases or Ozone (OltSUB3lt SUBgt, 0
- 0.01), Carbon Dioxide (CO2, 0.01-0.1),
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The Thermosphere

• The thermosphere starts just above the
  mesosphere and extends to 600 kilometres (372
  miles) high. The temperatures go up as you
  increase in altitude due to the Sun's energy.
  Temperatures in this region can go as high as
  1,727 degrees Celsius. Chemical reactions occur
  much faster here than on the surface of the
  Earth. This layer is known as the upper
  atmosphere.

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The Mesosphere
The mesosphere starts just above the stratosphere
and extends to 85 kilometres (53 miles) high. In
this region, the temperatures again fall as low
as -93 degrees Celsius as you increase in
altitude. The chemicals are in an excited state,
as they absorb energy from the Sun. The mesopause
separates the stratosphere from the next
layer. The regions of the stratosphere and the
mesosphere, along with the stratopause and
mesopause, are called the middle atmosphere by
scientists.
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The Stratosphere
The stratosphere starts just above the
troposphere and extends to 50 kilometres (31
miles) high. Compared to the troposphere, this
part of the atmosphere is dry and less dense. The
temperature in this region increases gradually to
-3 degrees Celsius, due to the absorption of
ultraviolet radiation. The ozone layer, which
absorbs and scatters the solar ultraviolet
radiation, is in this layer. Ninety-nine percent
of "air" is located in the troposphere and
stratosphere. The stratopause separates the
stratosphere from the next layer.
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The Troposphere
The troposphere starts at the Earth's surface and
extends 8 to 14.5 kilometres high (5 to 9 miles).
This part of the atmosphere is the most dense. As
you climb higher in this layer, the temperature
drops from about 17 to -52 degrees Celsius.
Almost all weather is in this region. The
tropopause separates the troposphere from the
next layer. The tropopause and the troposphere
are known as the lower atmosphere.
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Forming of the Ozone Layer
The ozone layer region of the stratosphere
containing relatively high concentrations of
ozone, located at altitudes of 12-30 miles (19-48
km) above the earth's surface. Ozone in the ozone
layer is formed by the action of solar
ultraviolet light on oxygen which provides the
energy for oxygen atoms to react with dioxygen
molecules. O O2 O3
(ozone)
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Where the Ozone Is Found
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How the Ozone Helps Us
Even the small amount of ozone plays a key role
in the atmosphere. The ozone layer absorbs a
portion of the radiation from the sun, preventing
it from reaching the planet's surface. Most
importantly, it absorbs the portion of
ultraviolet light called UVB. UVB has been linked
to many harmful effects, including various types
of skin cancer, cataracts, and harm to some
crops, certain materials, and some forms of
marine life. Meaning that the ozone is vital for
the survival of life on earth.
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Ozone Depletion
For over 50 years, chlorofluorocarbons (CFCs)
were thought of as miracle substances. They are
stable, non-flammable, low in toxicity, and
inexpensive to produce. Over time, CFCs found
uses as refrigerants, solvents, foam blowing
agents, and in other smaller applications. Other
chlorine-containing compounds include methyl
chloroform, a solvent, and carbon tetrachloride,
an industrial chemical. Halons, extremely
effective fire extinguishing agents, and methyl
bromide, an effective produce and soil fumigant,
contain bromine. All of these compounds have
atmospheric lifetimes long enough to allow them
to be transported by winds into the stratosphere.
Because they release chlorine or bromine when
they break down, they damage the protective ozone
layer. The discussion of the ozone depletion
process below focuses on CFCs, but the basic
concepts apply to all of the ozone-depleting
substances (ODS).
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Why It Happens
The CFCs are so stable that only exposure to
strong UV radiation breaks them down. When that
happens, the CFC molecule releases atomic
chlorine. One chlorine atom can destroy over
100,000 ozone molecules. The net effect is to
destroy ozone faster than it is naturally
created. To return to the analogy comparing ozone
levels to a stream's depth, CFCs act as a siphon,
removing water faster than normal and reducing
the depth of the stream. Large fires and certain
types of marine life produce one stable form of
chlorine that does reach the stratosphere.
However, numerous experiments have shown that
CFCs and other widely-used chemicals produce
roughly 85 of the chlorine in the stratosphere,
while natural sources contribute only 15.
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In conclusion.
The ozone layer is vital to life on earth and if
we keep destroying it as we are now the polar
ice caps will melt and the earth will flood and
even if any land does survive the heat will be
unbearable and the UVB will cause people to get
life threatening diseases. The earth will no
longer be a planet that human life can live on.