An ancient piece of the Pacific Ocean was buried 400 miles below China

Scientists have identified an old part of the Pacific Ocean – the ancient remnants of the ocean floor long before that – that stretches hundreds of miles below China in the transition zone of the Earth’s crust.

The rocky slab that was used to line the bottom of the Pacific is a remnant of the marine lithosphere, the outermost layer of the Earth’s surface, made up of crust and solid outer parts.

However, the lithosphere is not always determined to enjoy the views above. The upper surface layer is composed of several fragmented tectonic plates, which gradually migrate to the surface and occasionally run into each other.

During this collision, a geological process called subdivision can take place, where one plate in the subtraction zone is forced to fall below the other, and it leads deep inside the planet.

In a new study, China and the U.S. Scientists have now seen this epic event occur at a greater depth than before.

Earlier, scientists had noticed the hijacking of slabs while examining borders at a depth of about 200 kilometers (about 125 miles).

Now, due to the vast network of more than 300 seismic stations spread across northeastern China, researchers were able to see the event at a very low point, with imaging parts of the tectonic plate under the Pacific Ocean being pushed into the middle of the mantle. Level transition zone, at dep depths of 410-660 kilometers (254–410 miles) below the Earth’s surface.

Screenshot 2020 11 17 at 5.44.54 (Christoph Bergsdat / Science Photo Library)

To interpret the sinking slab, the team introduced two seismic velocity closures, areas underground where seismic waves face inconsistencies. In this case, two inconsistencies were encountered, which the team says are related to both the top and bottom of the dipping plate.

“Based on the details of seismological analysis, the upper band is perceived as a moho inconsistency of a subaired slab,” says Q-Fu Chen, a geologist at the Chinese Academy of Sciences.

“Hydros conditions in the marine part of the slab cause low closure due to partial melting of the sub-slab henosphere.”

While the subduction of the plate can be seen in the process below the china, the subduction zone itself is located farther east, the slab is angled at a relatively shallow 25-degree angle toward the bottom.

“Japan is at a point where the Pacific Plate reaches a depth of about 100 kilometers,” says Fenglin Niu, a seismologist at Rice University.

Thanks to new imaging, scientists are getting a better idea of ​​what happens to a crippled slab when it reaches this part of the transition zone, including how it deforms, and how much water is lost from its oceanic crust. .

“A lot of studies suggest that the slab actually deforms a lot in the mantle transition zone, it becomes softer, so it deforms easily,” says Niu.

“We are still debating whether this water has been completely released into that depth. There is growing evidence that a portion of the water remains inside the plate to go deeper and deeper.”

These findings are reported Nature Geoscience.