Slow-motion collisions of tectonic plates under the ocean drag about three times more water down into the deep Earth than previously estimated, according to a first-of-its-kind seismic study that spans the Mariana Trench.
The observations from the deepest ocean trench in the world have important implications for the global water cycle, according to researchers in Arts & Sciences at Washington University in St. Louis.
“People knew that subduction zones could bring down water, but they didn’t know how much water,” said Chen Cai, who recently completed his doctoral studies at Washington University. Cai is the first author of the study published in the Nov. 15 issue of the journal Nature. “This research shows that subduction zones move far more water into Earth’s deep interior — many miles below the surface — than previously thought,” said Candace Major, a program director in the National Science Foundation’s Division of Ocean Sciences, which funded the study. “The results highlight the important role of subduction zones in Earth’s water cycle.”
“Previous estimates vary widely in the amount of water that is subducted deeper than 60 miles,” said Douglas A. Wiens, the Robert S. Brookings Distinguished Professor in Earth and Planetary Sciences in Arts & Sciences and Cai’s research adviser for the study. “The main source of uncertainty in these calculations was the initial water content of the subducting uppermost mantle.”
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