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Study challenges 'Snowball Earth' theories

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In a May 2005 NASA image, the ocean break-off point of the Helheim Glacier is pictured in southeast Greenland. An international conference on global warming released a report April 6, 2007 warning of increases of world hunger, flooding, and species extinction unless world nations take action to adapt to climate change. (UPI Photo/NASA/Wallops) 
Published: May 28, 2009 at 1:01 PM
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SANTA BARBARA, Calif., May 28 (UPI) -- U.S. scientists are challenging the prevailing views of the effects of the so-called "Snowball Earth" glaciations on life on Earth.

Researchers from the University of California-Santa Barbara analyzed microfossils found in rocks at the bottom of the Grand Canyon to challenge current theories concerning the effects of the glaciers occurring approximately 635 million to 726 million years ago. Those glaciations are thought to have been responsible for the widespread deaths of early life on Earth.

"Snowball Earth" is the popular term for the glaciers that are hypothesized to have entombed the planet in ice, Assistant Professor Susannah Porter, a study co-author, said. It has long been noted those glaciers are associated with a big drop in fossil diversity, suggesting a mass die-off due to the severity of the glaciations.

But the authors of the study -- including former UCSB graduate student Robin Nagy, Carol Dehler of Utah State University and Yanan Shen of the University of Quebec -- found evidence suggesting the drop in diversity occurred some 16 million or more years before the glaciations.

A paper describing the research and its findings appears in the journal Nature Geoscience.

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