Amid a large number of countries suffering from severe water crisis leading to around 4 billion people — almost two-thirds of the world’s population — experiencing water scarcity for at least one month every year, the quest for finding more sources of the life-saving compound has led the researchers from Northwestern University, Illinois (the US) to discover a gigantic reservoir of water that is three times the size of Earth's oceans combined, 700 km beneath the planet's surface in a rock known as ringwoodite.
The findings were first published in the ‘Science’ magazine in 2014 titled 'Dehydration melting at the top of the lower mantle'. The study also presented the unique properties of ringwoodite.
The researchers are of the view that this hidden ocean beneath the surface, concealed within a blue rock known as ringwoodite, is probably the primary source of water on Earth’s surface. The size of this subterranean ocean is triple the volume of all the planet’s surface oceans combined.
“This is substantial evidence that water on Earth came from within,” the Science magazine quoted Steven Jacobsen, a researcher at Northwestern University in Illinois and the lead author of the study as saying.
"The ringwoodite is like a sponge, soaking up water, there is something very special about the crystal structure of ringwoodite that allows it to attract hydrogen and trap water," the geophysicist had said in the study paper.
"I think we are finally seeing evidence for a whole-Earth water cycle, which may help explain the vast amount of liquid water on the surface of our habitable planet. Scientists have been looking for this missing deep water for decades," he further said.
To uncover this underground ocean, researchers used an array of 2000 seismographs across the United States, analysing seismic waves from over 500 earthquakes. Waves which travel through Earth’s inner layers, including its core, slow down when passing through wet rock, allowing scientists to assume the presence of this vast water deposit.
"The high water storage capacity of minerals in Earth's mantle transition zone (410- to 660-kilometer depth) implies the possibility of a deep H2O reservoir, which could cause dehydration melting of vertically flowing mantle. We examined the effects of downwelling from the transition zone into the lower mantle with high-pressure laboratory experiments, numerical modelling, and seismic P-to-S conversions," said the scientists.
"These results suggest hydration of a large region of the transition zone and that dehydration melting may act to trap H2O in the transition zone, " the researchers said.
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