Earth has a secret water reservoir

Scientists have discovered a vast reservoir of water under the Earth's mantle they say could be larger than all the oceans combined.
Canadian researchers say analysis of a rare mineral points to the huge store of water deep in Earth's mantle, 400-600 kilometres beneath our feet.
The evidence comes from a water-loving mineral called ringwoodite that came from the so-called transition zone sandwiched between the upper and lower layers of Earth's mantle, they said in the journal Nature.
Analysis shows that 1.5% of the rock comprises molecules of water. "This sample really provides extremely strong confirmation that there are local wet spots deep in the Earth in this area," said Graham Pearson of Canada's University of Alberta, who led the research.
"That particular zone in the Earth, the transition zone, might have as much water as all the world's oceans put together."

Ringwoodite is named after Australian geologist Ted Ringwood, who theorised that a special mineral was bound to be created in the transition zone because of the ultra-high pressures and temperatures there.
A piece of this mineral has been a long-sought goal. It would resolve a long-running debate about whether the poorly-understood transition zone is bone-dry or water-rich.
In 2008, amateur gem-hunters digging in shallow river gravel in the Juina area of Mato Grasso, Brazil, came across a tiny, grubby stone called a brown diamond.
In its interior, they found a microscopic trace of ringwoodite -- the very first terrestrial evidence of the ultra-rare rock. "It was a bit of a piece of luck, this discovery, as are many scientific discoveries," Pearson said in a press release.