Evolution of the Earth's atmosphere and its geological impact

Current problems with the ozone layer and rising carbon dioxide levels have highlighted the importance of the atmosphere, with its delicate balance of gases. In fact, the atmosphere has been changing since the Earth formed. From anoxic beginnings to its current oxygenated state, it has influenced depositional processes on the Earth's surface and helped the development of active, oxygen-breathing life forms that culminated in ourselves. Evidence for changes in the atmosphere is found in the sediments accumulated on the Earth's surface, where fossils are also preserved. In this article the major geological aspects of the atmosphere's evolution are considered; in particular, the role of oxygen is aired.