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What Really Caused the Great Extinction?

By greenexpander ⋅ March 25, 2008 ⋅  Email This Post ⋅  Print This Post ⋅ Post a comment

A new study shows that the poisonous gases coming from the ocean may have not triggered the world’s greatest mass extinction. The world lost about 90% of the ocean species and 70% of its land species 251 million years ago, when the Permian period came to an end.

Scientists suspect that the high levels of hydrogen sulfide and methane in the atmosphere might be the ones responsible for poisoning creatures at that time.

“Toward the end of the Permian, we had a warming climate with much more carbon dioxide than today, ocean circulation was extremely sluggish, and the oceans became anoxic—essentially deprived of oxygen,” explained geobiologist and study co-author David Beerling from the University of Sheffield in England. 

A computer simulated the conditions from the Permian period, experimenting with different concentrations of hydrogen sulfide and methane to see what happened in each case.

“We found some interesting things going on with ozone chemistry, but we didn’t find any evidence that hydrogen sulfide and methane triggered a collapse of the ozone layer. These are chemicals produced mainly at the tropics that oxidize [and thus neutralize] ozone-destroying pollutants, ” Beerling said. 

source: Nature Geoscience; photo credit: palaeos.com

Tags: dinosaurs, extinction, permian