Scientists discover how and when a subterranean ocean emerged

phys.org | 7/1/2019 | Staff
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"The mechanism which caused the crust that had been altered by seawater to sink into the mantle functioned over 3.3 billion years ago. This means that a global cycle of matter, which underpins modern plate tectonics, was established within the first billion years of the Earth's existence, and the excess water in the transition zone of the mantle came from the ancient ocean on the planet's surface," said project leader and co-author of the article Alexander Sobolev, a member of the Russian Academy of Sciences (RAS) and Doctor of Geological and Mineralogical Sciences who is a Professor at Vernadsky Institute for Geochemistry and Analytical Chemistry under the Russian Academy of Sciences.

The Earth's crust consists of large continuously moving blocks known as tectonic plates. Mountains are produced when these plates collide and rise up, and the shock of the collisions leads to earthquakes and tsunamis. These plates move very actively under the World Ocean: old oceanic crust, including the minerals that have absorbed seawater, sinks deep into the Earth's mantle. Some of this water is released again due to the effect of high temperatures and plays a role in volcanic eruptions, such as those that occur in Kamchatka, the Kuril islands and Japan. The water that remains in minerals of the oceanic crust at higher temperatures continues to descend into the deep mantle and accumulates at a depth of 410-660 km in the structure of the minerals wadsleyite and ringwoodite and high-pressure modifications of olivine (magnesium iron silicate), the main mineral of the mantle. Experiments have shown that these minerals can contain significant quantities of water and chlorine. This is how the greatest part of the World Ocean could be "pumped" into the planet's interior over the billions of years of its existence.

Process - Part

This process is only a part of the global...
(Excerpt) Read more at: phys.org
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