For years, it has been observed that seismic waves travelling in the east-west part of the earth are faster than those in the other parts. And scientists may know the reason now.
According to them, the iron alloys located at the center of the earth appeared to have crystallized in a way that is easier to pass on the north-south axis than on the east-west. The study was led by Maurizio Mattesini, a geologist at the Universidad Complutense de Madrid. It was published on the journal Proceedings of the National Academy of Sciences.
“The structure of the atoms looks different in one direction than the other,” Norm Sleep, a geologist who was not part of the study, said.
In textbooks, the Earth’s inner regions looks like the mantle and core were presented as simple and homogenous regions. But in the study, it looks like the geology of the core is more complex than scientists originally thought. By using better seismographs, the seismic waves are presented clearer than before.
The outer core is composed mostly of liquid iron while the inner core is made of solid ball that is about 750 miles in diameter, which formed as the geology of the Earth cooled.
“The center of the earth is literally a crystal,” David Stephenson, a geologist at CalTech, said.
By the 1990s, geologists slowly began to notice that seismic waves are traveling comparatively faster in the north-south region by about three percent than those in the east-west regions.
According to the new data, the crystals formed enable researchers to gather a particular alignment—known as anisotropy—that makes it easier for waves to travel in one direction than the other.