The Great Mass Extinction - a Sudden Event or a Slow Moving Train-Wreck?

Presenter: Roger Summons, Massachusetts Institute of Technology
When: November 24, 2008 11AM PST

A great mass extinction took place 252 million years ago when approximately 90% of the existing marine taxa were lost. Both the magnitude of the extinction and the slowness of the subsequent faunal radiation are enigmatic. The event is also known for the number and diversity of theories about its cause(s) including catastrophic volcanism, sudden climate change, overturn of stagnant oceans and bolide impact. Studies of molecular fossils confirm that the oceans were stagnant (euxinic) for some considerable period of time before and after the main biological turnover. Accordingly this event appears to be the culmination of particular paleo-oceanographic circumstances that happened on a geological timescale.

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