The Earth's Atmosphere and Air Pollution

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The Earth's Atmosphere and Air Poll ution

Approximately 4600 million years ago the Earth formed, when hot, dense masses of gas and dust around the sun collapsed on itself - this was caused by gravity.


A mass of gas and dust got hotter and hotter as the particles were  pulled in and squashed together. It then began to cool down, solidify and break up into chunks called planets - one of which was Earth.

Around 4.5 billion years ago. The early atmosphere most likely formed from the huge volumes of gases given out by volcanoes. These gases were mainly Carbon Dioxide and Water Vapour but smaller proportions of other gases such as Ammonia and methane.

Ammonia was broken down by sunlight and by its reaction with oxygen, this formed nitrogen. Nitrogen is an unreactive gas. Once released into the atmosphere, nitrogen reacts with other substances only with difficulty. So the levels of nitrogen in the atmosphere increased until they reached today’s level.

The early atmosphere was probably mostly carbon dioxide, with little or no oxygen. There were smaller proportions of water vapour, ammonia and methane. As the Earth cooled down, most of the water vapour condensed and formed the oceans. So then the atmosphere was mainly Carbon Dioxide 

Over many millions of years the amount of carbon dioxide of the air decreased, while the amount of oxygen increased. The main reason for the increase of oxygen was due to the photosynthesis by plants.

Although Photosynthesis isn’t the only reason that carbon dioxide decreased.

Carbon Dioxide is locked away inside limestone, limestone is a sedimentary rock formed when layers of sand/mud and animal remains fall to the bottom of an ocean or lake, and slowly decompose and are crushed together by the weight of the water, forming a rock. Carbon Dioxide is locked away inside limestone, mainly as calcium carbonate. More carbon dioxide was locked away in fossil fuels, which are found in sedimentary rock.

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Due to Carbon Dioxide being a soluble gas, much of it dissolved into the oceans. The reason for this was that organisms that lived in the sea needed to form the chemical needed for their shells and skeletons

The atmospheres of Mars and Venus today, which contain mostly carbon dioxide, are similar to the early atmosphere of the Earth. (Shown in fig 1)

  • The air around us is a mixture of gases, mainly nitrogen and oxygen, (these two gases alone make up 99% of the atmosphere). However there are many other gases in the atmosphere in very small ...

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