Ozone Layer Depletion

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ISSUES AND CONCERNS ABOUT THE OZONE LAYER DEPLETION

INTRODUCTION
The ozone layer protects the Earth from the ultraviolet rays sent down by the sun.  If the ozone layer is depleted by human action, the effects on the planet could be catastrophic. In recent years, the ozone layer has been the subject of much discussion.  And rightly so, because the ozone layer protects both plant and animal life on the planet. The atmosphere is divided into five layers:  the troposphere, the stratosphere, the mesosphere, the thermosphere, and the exosphere.  The troposphere is the layer closest to earth and is where all weather happenings occur.  The stratosphere is located directly above the troposphere, about 10-50 kilometers above the planet, and houses the ozone layer at an altitude of 20-30 kilometers.  The mesosphere is located approximately 50-80 kilometers above the earth, while the thermosphere rests at an altitude of approximately 100-200 kilometers above the earth’s surface.  Finally, the boundary of the outermost layer, the exosphere, extends roughly to 960-1000 kilometers above the earth. 

Figure 1:  Earth's atmosphere is divided into layers, which have various characteristics. The ozone levels have decreased to a normal level. Normal meaning the levels have dropped from the levels reported in 1980. The ozone layer is an important and fragile part of earth. If we did not have an ozone layer between 10km and 50km, high ultraviolet radiation would pour through. This would create harmful living conditions for all life forms. The fact that the ozone layer was being depleted was discovered in the mid-1980s.  The main cause of this is the release of CFCs, chlorofluorocarbons. Antarctica was an early victim of ozone destruction.  A massive hole in the ozone layer right above Antarctica now threatens not only that continent, but many others that could be the victims of Antarctica's melting icecaps.  In the future, the ozone problem will have to be solved so that the protective layer can be conserved. The ozone layer:  What is it?

The ozone layer is a portion of earth’s atmosphere that contains high levels of ozone. The ozone found in our atmosphere is formed by an interaction between oxygen molecules (composed of two oxygen atoms) and ultraviolet light. When ultraviolet light hits these oxygen molecules, the reaction causes the molecules to break apart into single atoms of oxygen.  These single atoms of oxygen are very reactive, and a single atom combines with a molecule of oxygen to form ozone, which is composed of three atoms of oxygen. The ozone layer protects the Earth from the ultraviolet rays sent down by the sun.  If the ozone layer is depleted by human action, the effects on the planet could be catastrophic. The ozone layer is essential for human life.  It is able to absorb much harmful ultraviolet radiation, preventing penetration to the earth’s surface.  Ultraviolet radiation (UV) is defined as radiation with wavelengths between 290-320 nanometers, which are harmful to life because this radiation can enter cells and destroy the deoxyribonucleic acid (DNA) of many life forms on planet earth.  In a sense, the ozone layer can be thought of as a ‘UV filter’ or our planet’s ‘built in sunscreen’ (Geocities.com, 1998).  Without the ozone layer, UV radiation would not be filtered as it reached the surface of the earth.  If this happened, ‘cancer would break out and all of the living civilizations, and all species on earth would be in jeopardy’ (Geocities.com, 1998).  Thus, the ozone layer essentially allows life, as we know it, to exist.

Figure 2:  Ozone thickness over Labrador, Canada measured in Dobson Units

CAUSES OF OZONE LAYER DEPLETION
Ozone depletion:  Who is responsible?
 It is important to recognize the sources of ozone depletion before one can fully understand the problem.  There are three main contributors to the ozone problem: human activity, natural sources, and volcanic eruptions.

Figure 3:  Humans...
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