GEO 101 Lecture Notes - Lecture 4: Agnatha, Supercontinent, Geophysical Global Cooling
21 Jan 2017
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Earth separates into compositional layers in order to cool: Heavy material sink to center and lighter materials stay near surface. Volcanic activity released gas and water trapped inside planet. ~3. 8 ga: earth cool enough for water to exist as liquid at surface. Simple, single-cell organisms: cyanobacteria (blue-green algae); ~3. 5 ga. Things get stuck to the cyanobacteria and it builds up and they become stromatolites. Formed most of the continents (90%) very early in earth"s history. Large land masses that consist of nearly all existing continents. Splitting up and reassembling of supercontinents generated many geologic features. As things shift, water cannot flow properly. Simple life (single and some multi-cell organisms) This covers about 90% of earth"s history. The past 540 million years of earth"s history is split into three eras: Collision between (what is today) eastern north america and another sliver of land. Starting in paleozoic, life underwent massive diversification.
