Contributors

"Dick Gibson is a geologist living in Butte, Montana.  He's worked as a mineralogist analyzing kidney stones, a geophysicist exploring the world for oil and gas, and a teacher of field geology.  He is a study leader for Smithsonian Journeys in western USA, Alaska, Iceland, and elsewhere." 

Christopher Kendall
Distinguished Visiting Scientist, Jackson School of Geological Sciences, UT Austin

Bibliography 

http://en.wikipedia.org/wiki/Geological_time#Terminology

"petrology." Britannica Concise Encyclopedia. Encyclopædia Britannica, Inc., 2006. Answers.com 12 Sep. 2006. http://www.answers.com/topic/petrology

Extinction:  How Life on Earth Nearly Ended 250 Million Years Ago Douglas H. Erwin Princeton University Press 2006

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