Part 1 of Essay
Banded Iron Formations and evolution of the atmosphere The time between the formation of the earth and the beginning of the Cambrian(about 570mya) is a 4000 my long period known as the Precambrian, this includes approximately 90% of geological time of which we know very little about as pre-Cambrian rocks are poorly exposed ....

Part 2 of Essay
.... proterozoic that a critical change occurred in the atmosphere, when it changed from a trace oxygen content of the Archean atmosphere to above 15% oxygen by 1800 mya. It is widely believed that this change was brought about by the emergence of cyanobacteria which had adapted to create energy from the sun by photosynthesis(probably due to a shortage of raw materials for energy), as a result they had began to poison the earlier anaerobic bacteria or archea with their waste product; oxygen. This essay will focus o ....