ESC-1000 Lecture Notes - Lecture 4: Banded Iron Formation, Plumb Bob, Continental Crust
20 Jan 2017
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Document Summary
Banded iron formation (bifs) and red beds track the evolution of oxygen in the atmosphere; o2 reached present day levels around 2. 3 bya. Pillow basalt: needs water and lava; if found, it means there was water on earth, if not, no water. Age of oceans: water is a major component of volcanic gas, evidence for liquid oceans: pillow basalts, 3. 8 bya deposits suggesting marine deposition, cooling allowed for retention of liquid water and conditions suitable for life. Early life: first appearance of life 3. 5-4 bya: cyano-bacteria and stromatolites, photosynthesis by blue-green algae provided o2 for larger and more advanced life forms, early life forms: little evidence. No hard parts (teeth, bones, etc: earliest rocks with single celled eukaryotic organisms ~2 bya, multicellular prokaryotic organisms appeared ~1 bya. Early human population: size and location of primitive human populations were limited: Accidents: population took hundreds of thousands of years to reach beyond one billion people.
