The Atmosphere

The Ozone Layer

Why is there a hole in the ozone layer?

The ozone layer is not evenly distributed around the planet. It is thicker around the equator and nearby latitudes and thinner as one progresses north and south. This is true of the Earth’s atmosphere in general because the planet’s spin causes the planet to bulge slightly around the middle; the gravitational pull is consequently a little weaker and the atmosphere thickens. At the poles, the atmosphere is thinner, including the ozone layer. In addition, because ozone is dependent upon the interaction of sunlight and oxygen, there is naturally less ozone at the poles; furthermore, ozone layers fluctuate naturally over time due to numerous factors affecting climate and sunlight levels.

Since 1975, scientists believe that more than 33 percent of the ozone layer has disappeared. There is a seasonal factor to the reduction in ozone at any given time during the year, too. At different times, the ozone layer naturally declines or rises. But scientists also know that chlorofluorocarbons (CFCs), which are used for air conditioning, aerosol sprays, and halon in fire extinguishers, along with methane (CH4) and nitrous oxide (NO2), are broken down by UV radiation, freeing carbon, chlorine, and nitrogen atoms that then react with ozone molecules and destroy them. CFCs are particularly bad because they last so long in the atmosphere. One CFC molecule can destroy 100,000 molecules of ozone!


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