Massive Amounts of Water Entrained Into Earth's Mantle

SD
As oceanic crustal plates grow and butt against continental plates, they subduct under the continental plates. As they dive into the Earth's mantle for "re-cycling", these ocean crusts carry large quantities of water and sediment with them. Geologists are learning more about what happens to the subducted water.

Scientists know: many volcanoes need water for their eruption. In the upper mantle, water lowers the melting temperature of the rocks. As a consequence, it melts faster and can ascend in form of magma to the Earth's surface. In areas where an oceanic plate is pushed underneath a continent by plate tectonics processes, large quantities of water reach the interior of the Earth.

Such a region, called subduction zone, can be found at the west coast of Latin and South America. Through large cracks formed during the subduction process of the oceanic plates water penetrates, is partly captured and transported in the mantle. There, high pressure and temperatures squeeze it out of the subducting plate and the water ascends back to the surface. On the way back it supports the formation of magma. Therefore all subduction zones are characterized by volcanoes at the continental margin.

"So far we knew that the entrainment of water into the Earth's mantle in the area of subductions zones is substantial and that it is released again by volcanic process. Nevertheless, the exact path of the water down to the mantle and back to the surface had so far not been shown in one unifying context," explains Tamara Worzewski, geophysicist in the Collaborative Research Centre (SFB) 574 "Fluids and Volatiles in Subduction Zones -- Climate Feedback and Trigger Mechanisms for Natural Hazards" who has investigated these processes. Together with Dr. Marion Jegen and Prof. Dr. Heidrun Kopp from the Leibniz Institute of Marine Sciences at the Christian-Albrechts-Universität (IFM-GEOMAR) in Kiel and colleagues Dr. Heinrich Brasse from the Freie Universität Berlin and Dr. Waldo Taylor from Costa Rica, she was able to show for the first time the complete water path from the seafloor down to 120 kilometre depth and back to the surface using electromagnetic methods.

The study, now published in Nature Geoscience, is also part of Worzewskis PhD Study. _SD

PBSRegular readers of Al Fin and Al Fin Energy will be aware of these blogs' interest in hydrocarbons that find themselves inside the Earth's mantle. But the fate of water in the mantle can be closely tied to the fate of much of the organic carbon which finds its way into the mantle by the same subductive process. Volcanic eruptions clear a great deal of both water and carbon from the mantle, along with other gaseous and mineral matter. It is part of the ongoing geologic cycles of the planet.

And yet, massive amounts of crustal organic carbon and mantle hydrocarbons persist long enough to migrate and transform into potentially economic reserves of "fossil fuels." Most of this resource will remain unkown to humans, despite a great deal of it settling within the growing technological and economic reach of humans.

We have barely begun to learn the basics about our planet, our climate, our solar system, our portion of the spiral arm of the Milky Way Galaxy, and so on. How absurd it is that pseudoscientific quasi-religions such as catastrophic anthropogenic global warming orthodoxy, or peak oil DOOM!, should find such large, gullible, and enthusiastic followings.