After analyzing thousands of records of seismic waves, geophysicists at the University of Maryland, in the United States, detected the presence of generalized and heterogeneous structures close to the planet’s core unknown until now. They are supposedly extensive areas of dense and extremely hot rocks below the Earth’s mantle.
Although we still ignore the exact composition of the discovery, understanding the shape and extent of these elements can assist in clarifying geological processes that occur inside the Earth, as well as providing clues about the functioning of tectonic plates and the evolution of our home in the Universe .
The study was published in the journal Science and provides the first high-resolution overview of the Earth’s mantle. With a focus on the Pacific Ocean basin, the analysis brought to light something under the Marquesas Islands of French Polynesia, much larger than expected. Doyeon Kim, the researcher responsible for the publication, celebrates: “By focusing on thousands of elements, instead of a few, as usual, we get a whole new perspective.”
New approach and new tools
Earthquakes are known to generate seismic waves below the surface and that they travel thousands of kilometers. When they come into contact with rocks of different temperatures or compositions, they change their speed, bend or even disperse. These are the echoes analyzed by researchers, who measure such characteristics with seismometers, specific equipment for this purpose.
From the information collected, it is possible to create models that reveal various properties of the Earth’s interior. Doyeon Kim and his team looked at a specific type of wave, the shear wave, which is lateral, with a movement perpendicular to the direction of the force that generated it. Normally, it crosses the limits of the Earth’s mantle and is hardly identifiable. However, with a broader perspective, such as that adopted by scientists, similarities and patterns have been discovered.
Technology, of course, was fundamental in research, since an algorithm called Sequencer, developed for space studies, was applied to records covering a period from 1990 to 2018. “The use of machine learning in terrestrial science is growing rapidly, being that a method like the one we apply allows us to identify echoes of seismic waves and reach new conclusions about the base of the mantle, which is extremely enigmatic for us ”.
The Earth does not stop
With the results, the researchers found ultra-low speed zones (ULVZs) below Hawaii much larger than those identified so far. Such zones are found in volcanic areas, where hot rocks rise from the border region of the main mantle to produce islands. “This was surprising, as we expected them to be rarer, which means that these structures are much more extensive than we thought,” says Doyeon.
The scientist concludes: “It is incredible because it shows that the Sequencer can help us to contextualize data from around the world in a way that is unprecedented in history”.