The Evolution of the Atmosphere
Evolution of The Atmosphere
1 - Earth's surface was molten, so any atmosphere boiled away. Then it cooled and a crust formed, but volanoes kept erupting, giving out gases e.g. carbon dioxide and water vapour, which condensed and formed oceans.
2 - Carbon dioxide dissoved into the oceans and was used to develop marine organisms. Green plants evolved, and removed carbon dioxide and produced oxygen.
3 - The build up of oxygen created the ozone layer, which blocks harmful rays from the Sun, and killed early organisms who couldn't tolerate it.