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Mass Extinctions

Mass Extinctions. Evidence for Many Events over Geological History. Potential Triggers. Asteroid Impacts = sudden. Large Basalt Outflows. Large CO 2 changes which can affect atmospheric and ocean chemistry (slow). Periodic Comet Strikes.

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Mass Extinctions

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  1. Mass Extinctions Evidence for Many Events over Geological History

  2. Potential Triggers • Asteroid Impacts = sudden

  3. Large Basalt Outflows • Large CO2 changes which can affect atmospheric and ocean chemistry (slow)

  4. Periodic Comet Strikes • Fossil record shows some 26-27 million year period of some extinction event (usually small) • Nemesis Theory (likely not correct) • On the time scale of 20-30 million years (1/10 of our galactic orbit) – nearby stars could perturb our Oort cloud of Comets

  5. At least a dozen events The concept of impact induced extinction events is relatively new – first evidence came in 1980 regarding the KT event (65 million years ago – dead dinosaurs). Further research and data have no shown that such events are common.

  6. Periodic Extinctions of Varying Amplitude (percent extincted)

  7. Mass Extinctions and Evolution • ½ to 2/3 of all species are eliminated during big events • Plankton in the ocean is nuked • So both the land and water are effected • Encephelization Levels (EL) in organisms measure the amount of brain tissue in excess of that needed for basic metabolism maintenance

  8. Evolution of Intelligence? • This diagram has many features: EL Doubling time About 2 MY Unaltered EL Evolution would have produced “humans” 60 MYA Last 200 million years has constant slope Fastest Growth: 600-250 MYA; beginning of sea to land migration

  9. Implications • Evolutionary Clock gets reset • Life recovers (relatively rapidly) to fill new ecological niches  this empowers species diversification • This means that “survival of the fittest” doesn’t work on long timescales  random catastrophe important • Strangely, nature confirms that a “new world will arrive out of the ashes of the old one” • This will happen again (right after the final)

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