May 28, 2009

Study challenges ‘Snowball Earth’ theories

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.