Snowball Earth Saw Dynamic Ice Sheets

The snowball Earth hypothesis suggests that at some point approximately 715 million years ago our planet’s surface was totally – or as close as can be – covered in ice. Scientists had assumed that the glaciers covering the surface of the planet were stable, acting as a like for greenhouse gases that built up from from volcanoes under the ice.

However new research has shown that the ice retreated completely through the glaciations.

Pebbly glacial deposits, about 715 million years old, in layers from northern Namibia. The pebbles were deposited as “dropstones” from floating ice

A team led by Daniel Paul Le Heron from the Department of Earth Sciences at Royal Holloway University of London have found evidence that the ice was a lot more dynamic than was ever expected for a planet supposed covered in ice.

The researchers from Royal Holloway studied sedimentary rocks in northern Namibia where a thick pile of debris was laid down by glaciers. They discovered non-glacial shale rocks sandwiched between glacial sediments above and below.

“The evidence suggests that ice retreated completely during the glaciation, melting away in a warmer interglacial period, then regrowing before finally disappearing completely,” explains Dr Le Heron. “This is a very exciting finding because it shows that these ancient glaciers behaved exactly like ice sheets today.”

Source: Royal Holloway University of London

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