Slow collisions of tectonic plates of the ocean floor are pulling three times more water deep into the Earth than previously thought. This conclusion was made by scientists based on the results of a seismic study of the Mariana Trench.
Scientists knew that subduction zones were capable of sucking in water, but no one knew the actual volumes. The new result means that subduction zones play a much larger role in the water cycle in nature than previously thought.
As part of this work, the researchers listened to over a year of recordings of the Earth's rumbling - from simple noises to real earthquakes. The data was collected by a network of 19 passive seismographs around an ocean day stretching near the Mariana Trench, as well as an additional network of 7 seismographs on the islands.
How are stones able to “pull” water down? Different ways. Ocean water on the surface of the plate seeps into faults up to the planet's upper mantle and “gets stuck” there. Under certain conditions (temperature and pressure), chemical reactions transform water into a non-liquid form of hydrous minerals, together with which water remains in the stones of the geological plate. At the same time, the plate continues to move deeper into the earth's mantle.
New data have shown that the Mariana Trench's water-bearing rock zone stretches nearly 32 kilometers down under the ocean floor - much deeper than previously thought.
If we assume that this is happening in all other depressions of the world, it turns out that our data on the amount of water “sucked” into the mantle, that is, to a depth of more than 100 km, should be multiplied by about three.
Given that the sea level has remained almost unchanged throughout the geological time (varying within 300 meters), it is safe to say that this water somehow returns to the surface.
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Scientists believe that most of the water that enters through faults deep into the Earth eventually escapes into the atmosphere during volcanic eruptions. But there is no exact data that could confirm or refute such a theory.
The authors of the study hope that their work will inspire other experts to tackle this issue in order to better understand the water cycle in nature familiar to us from school days.
And they themselves are going to move to the Alaska region and conduct the same study there in order to confirm the similarity of the processes taking place in the oceanic faults around the world.
The study was published in the journal Nature.