evolution of the atmosphere

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The Evolution of the Atmosphere

The present composition of the atmosphere is 78% nitrogen, 21% oxygen and the remaining 1% is made up of Nobel gases and also 0.04 carbon dioxide. As well as these there is also lots of water vapour. Here is how the atmosphere evolved:

  • About 4.5 billion years ago the earth was just evolving and the volcanoes gave out four things: steam, carbon dioxide, ammonia and methane. There was no oxygen around at this time.

  • Two billion years on from this oxygen was produced due to the green plants, which were evolving. The covered most of the earth and removed the carbon dioxide and produced oxygen. Also much of the carbon dioxide dissolved in to the oceans. More nitrogen was also produced from the methane and ammonia reacting with oxygen.

  • During the last billion years or so a lot has changed. The build up of oxygen has taken place and more complex organisms are around to make use of the oxygen the ozone layer has been created which blocks the suns harmful raise. The most important change would be how the amount of carbon dioxide has decrease and there is virtually none left.
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Today’s Atmosphere

The atmosphere today is perfect for us. However there is a worry that we maybe changing it for the worst by releasing various gases from industrial activity. The two main worries are acid rain and The Greenhouse Effect.

   Acid rain is mainly sulphur dioxide and nitrogen oxides. The nitrogen oxides created from reactions between the nitrogen and oxygen in the air also the heat from burning. These gases then mix with clouds and from two substances: nitric acid and sulphuric acid and the acid rain is produce. ...

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Minor grammatical errors seen in some places. Otherwise, spelling, grammar and punctuation to a good level. Format of the essay is good but large paragraph spaces between paragraphs should be removed as they are un-necessary.

The candidate starts with a good introduction in the composition of the atmosphere. The candidate outlines the different stages of the evolution of the atmosphere well with the early atmosphere. To improve they should have improved concentrations or possible concentrations of the gases at this time, and diagrams. They explain the concepts of how gases are changing now only to a limited degree, and expansion is needed in places. I'm not sure why the earths structure as been discussed as this is not related to the question at all.

The candidate answers the question to a limited degree. They include good information about the way the early atmosphere formed, but only limited information of the effects of the different rising gas levels today and the reasons for it.