Is there a lost world under the Pacific Ocean?

Jan. 7 () –

With the help of a new high-resolution model, a team of geophysicists have discovered deep inside the Earth new areas that look like remains of submerged plates.

One is located under the western Pacific. However, according to current theories and knowledge of plate tectonics, there is no there should be subducted plate material therebecause it is impossible that there have been subduction zones nearby in recent geological history. The researchers They don’t know for sure what material it is instead and what that would mean for the internal dynamics of the Earth.

“That’s our dilemma. With the new high-resolution model we can see these types of anomalies everywhere in the Earth’s mantle, but we don’t know exactly what they are or what material creates the patterns we have discovered,” he explains. in a statement ETH Zurich professor Andreas Fichtner, author of the study. “It’s as if a doctor has been examining blood circulation with ultrasound for decades and finds arteries exactly where he expects them. If we give him a new and better scanning instrument, suddenly sees an artery in the buttock that really shouldn’t be there. “This is exactly how we feel about the new findings,” explains the wave physicist, who developed the model in his group and wrote the code.

So far, researchers can only speculate. “We believe that anomalies in the lower mantle have a variety of origins,” says Thomas Schouten, first author and PhD student at the Geological Institute of ETH Zurich.

He believes it may not simply be cold plate material that has been subducted over the past 200 million years, as previously assumed. “It could be ancient silica-rich material that has been there since the formation of the mantle about 4 billion years ago and has survived despite convective movements in the mantle, or areas where iron-rich rocks accumulate. as a consequence of these movements of the mantle over billions of years,” points out.

For the doctoral student, this means above all that more research with even better models is needed to see more details of the Earth’s interior. “The waves we use for the model essentially only represent one property, namely the speed at which they travel through the Earth’s interior,” says the geoscientist. However, this does not do justice to the complex interior of the Earth. “We have to calculate the different material parameters that could generate the observed speeds of the different types of waves. “Basically, we have to delve into the material properties behind wave speed”says Schouten.

The study has been published in the journal Scientific Reports by a team of geophysicists from ETH Zurich and the California Institute of Technology.

These scientists not only used one type of seismic wave to study the structure of the Earth’s interior, but all of them. Experts call this procedure full waveform inversion. This makes the model very computationally intensive, so The researchers used the Piz Daint supercomputer at the CSCS in Lugano.