Hidden Oceans Inside the Earth

Oceans inside the Earth

We know more about the surface of Mars than we do the mantle of the planet we live on. As little as 19 miles below the surface the continental crust turns into the Earth’s mantle, a layer some 1,800 miles thick that surrounds the Earth’s molten outer core. We know very little about this vital component of our planet.

Professor Steven Jacobsen of Northwestern University, think that the rocks in the Earth’s mantle might have had a part in creating the Earth’s oceans specifically a magnesium-rich silicate called ringwoodite.

Ringwoodite Photo by Joe Smith
Ringwoodite Photo by Joe Smith

Ringwoodite is made by mixture of silicon, oxygen, iron, and magnesium. Samples of ringwoodite had been made in the lab or found in meteorites. In March of 2014 a research group discovered an unusual diamond in the gravel along a shallow riverbed in Brazil. The battle-scarred diamond looked like it has been to hell and back. Tests of this diamond revealed that it contained a speck of ringwoodite that had formed under extremely high pressure.

Credit: University of Alberta
Credit: University of Alberta

They discovered that about 1.5% of ringwoodite’s weight is water. The water isn’t present as liquid, ice or vapor, instead, it is trapped in the ringwoodite’s molecular structure as hydroxide ions.

One of the reasons the Earth is such a dynamic planet is because of the presence of some water in its interior.  Water changes everything about the way a planet works. Professor Jacobsen comments, 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.  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. Ringwoodite here is key.  Its crystal-like structure makes it act like a sponge and draw in hydrogen and trap water.

So there could be oceans of water still sitting in the mantle rocks beneath us. New findings will help scientists better understand the Earth’s water cycle.


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