9. Archaean Sphere Interactions (10pts Total): The graph bel…
9. Archaean Sphere Interactions (10pts Total): The graph below shows the composition of Earth’s atmosphere through time may be useful in answering this question. A) (7pts) CO2 (carbon dioxide) content of Earth’s atmosphere decreased rapidly from 35% at 3.3 Ga to less than 5% by 2.0 Ga. Explain the multi-step process by which CO2 was removed from the atmosphere. Please include verbal descriptions of different carbon/oxygen species in the series of chemical reactions that answer this question from start to end. B) (3pts) Globally iron ore deposits are typically Late Achaean to Early Proterozoic in age. What was the source of the Fe at the Earths surface, and describe the process by which iron increased its from a few % to greater than 40% making it an economical ore deposit beginning around ~2.2 Ga (the graph may be of some assistance).