Scientists discovered huge 'ocean' beneath Earth's surface bigger than all the seas above land

Considering the sheer size of our planet's oceans is enough to make any one of us feel overwhelmed.

Well, what if I told you that scientists have discovered a reservoir of water hidden deep beneath the Earth’s surface which is thought to be three times larger than all the water in our oceans? Scary, right?

But rather than existing in liquid form, this supply is trapped 400 miles underground within a mineral called ringwoodite, located in the Earth’s mantle.

Ringwoodite acts like a sponge, holding water within its crystal structure in a way that’s neither liquid, solid, nor gas — but something entirely different at the molecular level.

The discovery was made in 2014 by researchers at Northwestern University in Illinois, who used seismometers to study US earthquake waves traveling through the planet.

The ocean covers more than 70 percent of the surface of our planet (DrPixel/Getty Images)

These waves revealed that the water wasn’t near the surface but much deeper, embedded in specific types of rock.

Geophysicist Steve Jacobsen, part of the research team, described ringwoodite’s unique structure as being able to absorb hydrogen and trap water under intense pressure and heat, unlike anything seen before.

"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," said Jacobsen.

"This mineral can contain a lot of water under conditions of the deep mantle."

In their research, scientists found that the waves weren't limited to the Earth's surface, but moving throughout the planet's core.

A sample of ringwoodite (THIERRY ZOCCOLAN/AFP via Getty Images)

By measuring the speed and depth of those waves, researchers were able to work out what sort of rocks the water was being contained in - landing on ringwoodite in the end.

The substance can contain up to 1.5 percent water, and if the ringwoodite under the surface has just one percent water in its molecular build-up, it would mean that it holds three times more water than all of the oceans on the Earth's surface.

So why is it important?

Well, the discovery could help scientists determine how Earth was formed, furthering the theory that the Earth's water 'came from within', rather than from asteroids and comets.

Jacobsen explained at the time: "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."

Moving forward, Jacobsen and his team want to determine whether or not this layer wraps around the entire planet Earth.