Much of our knowledge of what lies at the center of our planet comes from the study of seismic waves that arise from earthquakes. Careful analysis of these waves can reveal the composition of rocks and metals beneath the Earth's surface.
A new study of seismic waves propagating from two different earthquakes, at the same location but separated by a distance of 20 years, has revealed changes taking place in Earth's outer core, a layer of molten iron and nickel that rotates between the surface mantle and inner core. (deepest layer) Earth.
The outer core and the iron contained within it directly affect the magnetic field of our planet, which in turn provides protection from outer space and solar radiation. The Earth's core makes life on this planet possible.
Therefore, if the Earth's core changes then the best thing that humans can do is to quickly learn about the outer core of the Earth and its evolution over time is very important. Data recorded from four seismic wave monitors in both earthquakes showed that waves from subsequent events moved about one second faster when they passed through the same outer core region.
"Something has changed along the path of the wave, so it can go faster now. The material that was there 20 years ago is no longer there," said geologist Ying Zhou of Virginia Tech, quoted by IFL Science, Sunday (3/03/2011). 7/2022).
"This is a new material, and it's lighter. These lighter elements will move up and change the density in the region they are in," he continued.
The wave types analyzed here are SKS waves: they pass through the mantle as shear waves (S), then to the outer core as compressional waves (K), then exit the other side and return through the mantle again for more seconds. shear waves (second S). The timing of the passage of these waves can reveal what is really going on.
As for the two earthquakes, both were near the Kermadec Islands in the South Pacific Ocean. The first occurred in May 1997, and the second in September 2018. This provides researchers with a unique opportunity to see how the Earth's core may have changed over time.
Convection occurs in the molten iron of Earth's outer core, as it crystallizes into the inner core creating electric currents that flow, controlling the magnetic field around us. However, the relationship between the outer core and Earth's magnetic field is not fully understood - much of it is based on hypothetical modelling.
"If you look at the north geomagnetic pole, it's currently moving at about 50 kilometers per year. It's moving away from Canada and toward Siberia. The magnetic field isn't the same every day, it's changing," he said.
"Because it changes, we also speculate that convection in the outer core changes over time, but there's no direct evidence. We've never seen that."
This new study, and possible future studies like it - could provide useful insights into how the outer core and its convection change. While the changes noted here are not major, the more we know, the better.
In this regard, Zhou suggested that lighter elements such as hydrogen, carbon, and oxygen have been released in the outer core since 1997. This corresponds to a density reduction of about 2-3 percent and a convection flow velocity of about 40 kilometers per hour.
There are currently 152 Global Seismographic Network stations worldwide, which monitor seismic waves in real-time. While we cannot control the location or timing of an earthquake, we can ensure that as much data as possible is recorded about the earthquake.
"We can see it now. If we can see it from seismic waves, in the future, we can set up seismic stations and monitor the flow," he concluded.