We may have another "ocean" to add to the world map -- only this one is hidden hundreds of miles beneath our planet's surface.

 

A new study suggests that a hidden "ocean" is nestled in the Earth's mantle some 400 miles beneath North America. The hidden reservoir, apparently locked in a blue crystalline mineral called ringwoodite, may hold three times as much water that exists in all the world's surface oceans.

 

This discovery may help explain where Earth's water supply came from, and how subterranean water affects the shifting of rock in the Earth's outer crust -- a phenomenon scientists call plate tectonics.

 

"Geological processes on the Earth’s surface, such as earthquakes or erupting volcanoes, are an expression of what is going on inside the Earth, out of our sight," geophysicist Dr. Steven Jacobsen, an associate professor at Northwestern University, said in a written statement. "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."

 

According to the research, the hidden "ocean" may be trapped in the transition zone between the Earth's upper and lower mantle. The researchers think that movement within the mantle spurred a reaction that led the water to merge with the ringwoodite.

 

While some scientists subscribe to the theory that Earth's early water came from comets that came our way, the discovery of the hidden reservoir suggests that the world's water emanated from deep beneath the surface.

 

"It's good evidence the Earth's water came from within," Jacobsen told New Scientist.

 

A paper describing the research was published in the journal Science on June 13, 2014.