Composition of the Atmosphere Overview

Picture of Mount Saint Helens The composition of the earth's atmosphere is gradually changing over time due to the natural processes that occur on earth, as well as the many anthropogenic processes that have been introduced by humans. Natural biological processes such as the respiration of animals, including humans, removes oxygen from the atmosphere and in turn produces carbon dioxide (CO2). The photosynthesis of plants uses the carbon dioxide to produce oxygen which is released back into the atmosphere. Other natural processes include geologic events such as volcanic eruptions. Not only do these violent eruptions eject massive amounts of particle debris into the atmosphere, but they also spew out large amounts of carbon dioxide and water vapor.

While much of the atmosphere's composition is maintained by natural processes occurring on and within the earth, how human activities interact with the atmosphere has profound implications upon the quality and continuance of life on earth. Although the percent volume of man-made substances is only a minute fraction of the total volume of the atmosphere, this amount is significant because it is this portion of the atmosphere that comprises most of what we term as pollutants.

Quick Quiz: Which of these processess is defined as the effect of humans?

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