Taking into account how inaccessible the inner core of the Earth is, since no man or machine has been in this area (traveling to the center of the Earth is not as ‘simple’ as in the science fiction film The Core of 2003) , scientists infer minerals, heat, and density from Earth’s layers from how seismic waves travel.
As seismic waves move through various layers of the Earth, their speed changes and they can be reflected or refracted depending on the minerals, temperature, and density of that layer.
“Illuminated by earthquakes in the crust and upper mantle, and observed by seismic observatories on the Earth’s surface, seismology offers the only direct way to investigate the inner core and its processes,” explains Rhett Butler, a geophysicist at the University of Hawaii at Manoa School of Ocean and Earth Science and Technology (SOEST) and leader of the new work in the journal Physics of the Earth and Planetary Interiors.
Limits of the Earth’s core
Until now, experts believed that the inner core of our planet, which is about three-quarters the size of the Moon, was solid, in contrast to the region of liquid metal that surrounds it, the outer core. However, a new study questions this approach, stating that this mass responsible for the Earth’s magnetic field contains hard and soft iron.
The scientists used the Japanese Earth Simulator supercomputer to evaluate five pairings and broadly cover the inner core region.
The work claims that Earth’s “solid” inner core is, in fact, endowed with a range of liquid, soft and hard structures that vary throughout the upper 150 miles of the inner core. The finding of its heterogeneous structure provides important information on the dynamics at the boundary between the inner core and the outer core, which affects the generation of the Earth’s magnetic field.
The next thing will be to model the structure of the inner core in more detail using this same Japanese supercomputer to be able to compare it with certain characteristics of the Earth’s geomagnetic field.
“Knowing this boundary condition of seismology may allow a better predictive model of geomagnetism that protects and protects life on our planet,” suggests Butler.
“In stark contrast to the homogeneous soft iron alloys considered in all terrestrial models of the inner core since the 1970s, our models suggest that there are adjacent regions of hard, soft and liquid or soft iron alloys in the upper zone of the core. inner core, “Butler said.
The findings about the Earth’s inner core “impose new limitations on the composition, thermal history and evolution of the Earth,” say the scientists.
Referencia: Rhett Butler, Seiji Tsuboi. Antipodal seismic reflections upon shear wave velocity structures within Earth’s inner core. Physics of the Earth and Planetary Interiors, Volume 321, December 2021, 106802 DOI: 10.1016/j.pepi.2021.106802
