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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: oldest rocks 10:27am first fish 11:53pm first land plants 11:54pm first dinosaur 11:57pm ice ages 11:59.2 pm modern man 11:59.9 pm taxonomy o the process of grouping of a species into higher and higher divisions based on similar characteristics o kingdom phylum class order family genus 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 todays amount in less than 100 million years! why? unknown, but likely some large geologic event that disrupted the species sudden increase in ecological niches were rapidly filled in by the evolution of new species many of these quickly die out if theres 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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- Spring '08
- Geologic Time Scale