Lecture20_Extinctions

Why do we care about the patterns of extinction

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Unformatted text preview: kground level, straddling a geological boundary. Why do we care about the patterns of extinction? Possible causes of mass extinctions: sea level fall —> temp drop, development of ice caps Sea level change sea level rise —> high carbon shales form; anoxia Oceanic circulation change uplift decreases greenhouse effect and cause global cooling —> high weather reactions Tectonic activity absorb co2 Volcanic activity adds ash and other aerosols to stratosphere = short term cooling; adds co2 and other greenhouse gases to atmosphere = warming Extraterrestrial impact Examples: three different episodes of mass extinction: 1. end-Permian episode - severe and protracted; not very selective largest extinction in earth history 57% of families; 84% of genera; ~80-96% of species become extinct loss of cambrian fauna and decimation of Paleozoic fauna; severe at low latitudes (tropics) Cause? drop in sea level Extensive marine regression Major drop in ratio of 13C to 12C in ocean reservoirs Overturn of oceans high co2...
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This note was uploaded on 04/02/2014 for the course GEL 107 taught by Professor Motani during the Spring '08 term at UC Davis.

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