Planet Earth Menu
10, Mar, 2010
Atmosphere
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The Earth's atmosphere has changed throughout its history. It is generally thought that shortly after the Earth's formation (about 4,500 million years ago), the atmosphere consisted mainly of carbon dioxide, with some nitrogen and hydrogen.
Initially our planet was very volcanically active and large amounts of gas (especially nitrogen) were given off by the rocks; as this activity gradually decreased, the rate of increase of nitrogen in the atmosphere also slowed down. About 3,000 million years ago the first plants developed and began to give off oxygen; as a result, the amount of oxygen increased, reaching a plateau when oxygen-breathing animals became numerous. |
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