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Banded Iron Formations And The Beginning of Paper 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 .... Middle of Paper .... 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 on the evolution of the atmosphere and its relation .... 1256 words | 5 pages Subscription Length Price Join 30 days membership (recurring) $19.95 90 days membership (recurring) $39.95 180 days membership (non-recurring) $69.95