'Snowball' Earth may have melted to a 'mudball'

China National News (ANI) Monday 30th November, 2009

London, November 30 : New evidence has emerged which indicates that the 'snowball' Earth 700 million years ago thawed out of its frozen stage by melting to a 'mudball'.

Evidence for 'snowball' Earth comes from the discovery of glacial rock formations around the world that date back to this time, indicating that Earth was entirely frozen over about 700 million years ago.

One proposed explanation for the subsequent thawing is that carbon dioxide (CO2) levels soared during the freeze, warming the planet.

But recent studies of oxygen isotopes suggest that the level of CO2 was only a tenth of that required to melt the ice.

Now, according to a report in New Scientist, Dorian Abbot and Raymond Pierrehumbert of the University of Chicago have used climate models to study how dust from volcanoes and the weathering of rocks would affect the thaw.

They found that in regions where the amount of snowfall was low and any snow that did settle was sublimating away, enough dust would have accumulated to change the surface albedo sufficiently so that the Earth absorbed sunlight and thawed.

"It could get you out of the snowball at an appropriate CO2 value," said Abbot.

The mudball hypothesis is testable, by searching for a "dust signal" in rock formations of the appropriate age, he added.