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Unformatted text preview: GEOL 0820 Ramsey Natural Disasters Spring, 2011 LECTURE #24: Mega Disasters - Mass Extinctions, Meteorite Impacts, ... Date: 21 April 2011 I. Mass Extinctions • geologic time scale o divided into named eons, eras, periods, … o “deep time” ¡ very hard concept to grasp ¡ if the history of the earth was compressed into a 24 hour clock: ¾ oldest rocks Æ 10:27am ¾ first fish Æ 11:53pm ¾ first land plants Æ 11:54pm ¾ first dinosaur Æ 11:57pm ¾ ice ages Æ 11:59.2 pm ¾ modern man Æ 11:59.9 pm • taxonomy o the process of grouping of a species into higher and higher divisions based on similar characteristics o kingdom Æ phylum Æ class Æ order Æ family Æ genus Æ species • Cambrian Period o name given to a particular time in geologic history o 545 million years ago o an “explosion” of diversity in marine phyla ¡ from almost none to near today’s amount ¡ in less than 100 million years! ¡ why? ¾ unknown, but likely some large geologic event that disrupted the species ¾ sudden increase in ecological niches were rapidly filled in by the evolution of new species ¾ many of these quickly die out ¾ if there’s a loss of more than 25% of the families in a kingdom could lead to mass extinction Page 1/5 II. Biodiversity II....
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- Geologic Time Scale, sea floor spreading, Extinction event, Permian–Triassic extinction event