New discovery: the earth drags huge amounts of sea water into the depths of the mantle

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New discovery: the earth drags huge amounts of sea water into the depths of the mantle

2018-11-16 10:26:18 54 ℃

When the tectonic plates of the Earth move toward each other at the bottom of the ocean, they drag the seawater into the interior of the planet three times as much as previously thought.

These are the conclusions of a new paper published in the November 14 issue of Nature.

Using the seismic waves of the Marianas trench earthquake-oriented subduction zone, the researchers were able to estimate how much seawater was integrated into the deep depths of the rock.

Donna Shillington, a marine geology and geophysics researcher at the Lamont-Doherty Earth Observatory at the University of Costa Rica, wrote in the article that the findings have a major impact on understanding the Earth's deep water cycle. Water beneath the surface of the earth promotes the development of magma and can lubricate faults, making earthquakes more likely to occur.

Water is stored in the crystal structure of the mineral, and when a new, hot marine plate is formed, and when the plate is bent and broken, the liquid is incorporated into the earth's crust. The latter process is called subduction and is the only way for water to go deep into the ground.

Chen Cai, head of research at Washington University in St. Louis, said: "Before we did this research, every researcher knew that water had to be taken away by the subduction block, but they just didn't know how much water there was. "

The researchers used data from a seismic sensor network located in the middle of the Mariana Trench in the Western Pacific. The deepest part of the trench is located nearly 11 kilometers below sea level. The sensor detects the echoes of earthquakes and earthquakes and rings the crust like a bell. Cai and his team tracked the speed of these earthquakes: he said that slower speeds would indicate water-filled cracks in the rock and "hydrated" minerals that lock the water in the crystal.

Cai said the researchers observed this slowdown in the depths of the crust 30 kilometers from the surface. Using the measured speed, and the known temperature and pressure found there, the team calculated that the subduction zone would pull 3 billion megagrams of water (Tergram) into the crust every million years (one megagram equals one billion kilograms).

The seawater is actually very heavy, and the 1 meter long water cube weighs 1024 kilograms. However, the amount of water pulled down by the subduction zone is unbelievable. Cai said that this is also three times the amount of subduction water that was previously estimated to be absorbed.

This raises some questions. The researchers said that the newly estimated water volume decline is greater than the estimated amount of water ejected by the volcano, which means that scientists have missed something in the estimate. Cai said there is no water shortage in the ocean. This means that the amount of water that is dragged into the earth's crust and the amount of water that is ejected should be roughly equal. In fact, this is where scientists haven't understood, and they don't know how the water deep in the ocean moves inside the earth.