Oceans of Water stored 400 Miles beneath Earth’s Surface in Ringwoodite crystals
Posted by Abby Smith on 16th June 2014

Researchers from Northwestern University and University of New Mexico have found deep pockets of magma located 400 miles beneath the Earth’s surface in North America, where lies oceans’ worth of water locked up in a type of mineral called Ringwoodite, within the Earth’s rocky mantle.

This newly found evidence of water beneath Earth’s surface could alter the understanding of the composition of the planet and how its oceans formed. Also it would help Scientists understand Earth’s water cycle, and how plate tectonics moves water between the surface of the planet and interior reservoirs.

The Earth’s mantle is the hot, rocky layer between the planet’s core and crust and water is typically cycled down beneath the surface through plate tectonics, or movements of the Earth’s crust. Researchers have suspected that this mantle, 410 to 660 kilometers below Earth’s surface, could contain water trapped in rare minerals. The pressure and high temperatures of the plates moving down causes the water to be squeezed up and the rocks to partially melt at about 640km deep in the earth. But till now there was no solid proof that supported this discovery of water.

This new study is the first direct evidence that there may be water in this area of the mantle, known as the “transition zone,” on a regional scale, provided by Jacobsen and seismologist Brandon Schmandt from University of New Mexico.

A tiny piece of blue-colored ringwoodite contained a surprising amount of water bound in solid form in the mineral which was discovered this year from inside a diamond brought up from a depth of 640km by a volcano in Brazil. “When a rock with a lot of H2O moves from the transition zone to the lower mantle it needs to get rid of the H2O somehow, so it melts a little bit,” said Schmandt in a statement. If just 1% of the weight of mantle rock located in the transition zone is H2O, it would be equivalent to nearly three times the amount of water in our oceans.

To perform the study researchers synthesized hydrous ringwoodite and recreated the temperatures and pressures it would experience in the transition zone by heating it with lasers and compressing it between hard, anvil-like diamonds. Using their infrastructure, they then slowly increased the temperature and pressure to mimic the conditions in the lower mantle. The ringwoodite transformed into another mineral called silicate perovskite, and transmission electron microscopy showed that the mineral contained silicate melt around single crystals of perovskite.

This new discovery will give a new direction to Scientists who have been looking for this missing deep water for decades.