Atmosphere

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.

1	Amazing Photos of Northern Lights	earthfacts.net	1365
2	Aqueous Vapor	earthfacts.net	702
3	Atmospheric Illusions	earthfacts.net	504
4	Atmospheric Weight and Heat	earthfacts.net	625
5	Carbon Dioxide	earthfacts.net	559
6	Composition of the Atmosphere	earthfacts.net	457
7	Formation of Clouds	earthfacts.net	572
8	Function of the Atmosphere	earthfacts.net	382
9	Mirages	earthfacts.net	385
10	Particles in the Atmosphere	earthfacts.net	428
11	Precipitation	earthfacts.net	483
12	The History of Earth's Atmosphere	earthfacts.net	2595
13	Thickness of Ozone Layer	earthfacts.net	2358
14	Troposphere to Outer Space	earthfacts.net	970