The Sea Under The Surface

Research published in Science has confirmed the discovery of evidence that there could be oceans hundreds of kilometres beneath us.

This ‘sub-ocean’ would be up to three times larger in volume than all the water in our seven seas combined. However, this water is found in liquid, solid or gas form. It is dissolved and bound up in pockets of magma in an area called the ‘transition zone’ – a boundary layer located 410-660Km down which separates the Earth’s upper and lower mantle. The water was found hidden inside the crystal form of Ringwoodite, a bright blue mineral which can hold more than 1% of its weight as water.

These findings have shaken the general belief that water arrived on comets that struck the Earth. Instead, this water may be slowly rising from within, urged on by tectonic plate movements. This theory is supported by the fact that the oceans have not dissipated over the millions of years.

To make this discovery, researchers used seismometers to study the seismic waves generated by 500 earthquakes around the globe. The waves move through the Earth’s core and are detected at surface levels. By measuring the speed of these waves at different depths, the researchers were able to determine the type of rock the waves passed through. They discovered the ‘water layer’ as the waves pass slower through wet rocks than through dry rocks.

 They then conducted laboratory experiments exposing the Ringwoodite crystal to lasers creating a hot, high-pressure environment, which mimicked the conditions within the mantle. The data showed that these conditions were causing the water to be squeezed out, or ‘sweat’ out of the Ringwoodite.

So far, the mineral has only been found in North America, but the hope is to find it spanning the whole of the planet. This ground-breaking discovery indicates that the planet’s water cycle includes activity in the transition zone; it is a worldwide mechanism.

This area of science has been active for decades. This new finding will help to confirm and shape our understanding of our planet, and maybe even others out there.