The ozone layer is a layer of the stratospheric layer (20-30 km above the earth's surface) of the atmosphere that contains relatively high concentrations of the gas ozone. Ozone is a molecule that contains three atoms of oxygen. Ozone forms when oxygen molecules (composed of two oxygen atoms) and ultraviolet light interact, causing the molecule to separate into single oxygen atoms, which then combine with diatomic oxygen. http://www.umich.edu/~gs265/society/ozone.htm The ozone layer absorbs 95-99% of the high frequency ultraviolet rays that come from sunlight, thus protecting life on earth from harmful exposure. There currently is a hole in the ozone over Antarctica that is three times as large as the continental United States. http://www.rsmas.miami.edu/pressreleases/20060223-soden.html
In the 1970's and 1980's, chemicals known as CFCs, or chlorofluorocarbons, were implicated in the destruction of the stratospheric ozone layer. There was a big effort in the '70s and '80s to ban these chemicals, which were used extensively in refrigeration systems and spray can aerosols. These efforts seem to have worked, because, as of 2009, there appears to be a reduction the size of the hole in the ozone. The prediction indicates a possible closure in 30-60 years. However, recent evidence from NOAA researchers suggests that the replacement chemicals (HFCs) may be contributors in global warming. http://www.sciencedaily.com/news/earth_climate/ozone_holes/headlines/
This site features a video presentation by a NASA scientist on the function of the ozone layer and the reasons behind its causation. In this video he talks about the effects of man-made CFCs, cold atmospheric conditions, and weak sunlight as factors that work together to destroy ozone molecules. There is also a graphic illustration on this site that shows the location of the ozone in the stratosphere, the atmospheric layer above the troposphere that immediately surrounds the Earth.
NASA Scientist Explains the Ozone Layer and Mechanism of Damage
The ozone is the Earth's natural sunscreen, blocking harmful ultraviolet light from reaching the Earth's surface. The less ozone there is, the more UV light reaches the surface. There are three factors that have caused the widening of this hole. First, man-made CFCs make up about 80% of the chlorine-containing molecules in the stratosphere above the [[Anarctica|Antarctic}] region. Secondly, the extremely cold conditions in the atmosphere above the Antarctic cause the formation of exotic clouds that result in the release of chlorine from CFCs. Thirdly, the weak sunlight that occurs in September and October provides adequate energy to split a chlorine molecule away from a CFC, of which each one can destroy a thousand or more ozone molecules. It is estimated that the hole will shrink to the level observed in 1980 by the year 2070.
Location of the Ozone Layer in the Earth's outer Atmosphere
This figures illustrates the relative location of the ozone layer within the stratosphere above the Earth's surface.
References
Fast Facts
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'''Origin'''
Upper Atmosphere
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'''Chemistry of ozone'''
Three oxygen molecules, unstable, created by ultraviolet light striking oxygen molecules
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Loss of the Ozone Layer
Allows more ultraviolet rays to reach the earth's surface; also causes lower stratospheric cooling
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'''Ulraviolet light'''
High frequency ultraviolet light can cause skin and eye damage
