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.
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.”