The Oxygen Revolution

The earth atmosphere had NO free oxygen, NO ozone layer
Early oceans were rich in dissolved iron and silica, rare today
Silica today is extracted from seawater at the same rate it is dissolved since it is used by organisms for making skeletons
Iron can ONLY be dissolved in oxygen poor water, where only bacteria can survive
BIFs from this time can be traced for hundreds of miles, laid down uniformly and continuously
Can only form by an oxidation reaction
Two models demonstrate how BIFs could form in the early ocean, but neither alone can account for the sheer volume of BIFs worldwide
The formation of BIFs and the composition of our present day atmosphere both require the appearance of free oxygen in the atmosphere
Cyanobacteria (producers of stromatolites) were also present at this time, photosynthesizing away and generating free oxygen
With the presence of free oxygen in the oceans, bacteria had a new niche that could be filled: that of iron-oxidizing bacteria
With the lack of any ozone layer, UV radiation was very high, and with free oxygen in the ocean, inorganic precipitation could also occur
With free oxygen in the ocean and atmosphere, a new ecological niche could be filled RESPIRATION
Oxygen in the atmosphere = UV producing ozone layer to block the UV

	Criado por supergoober mais de 12 anos atrás

Geology (Historical Geology) Notas sobre GEO 3200 1, criado por supergoober em 23-04-2014.