“Clearly, the inner inner core is different from the outer layer,” said Tan-Sun Bam, lead author of the study. “That’s how we think atoms are [packed] It is slightly different in these two regions.“
Researchers study the inner core to better understand Earth’s magnetic field, which protects us from harmful radiation in space and helps make life possible on our home planet. Geophysicists theorize that it may have formed less than the inner core A billion years ago, which is relatively young on the geologic time scale. Research authors Explain The inner core grows outward by solidifying material from the liquid outer core, releasing heat and creating convection currents. This convection creates the Earth’s magnetic field.
The inner core, discovered by Danish seismologist Inge Lehmann in 1936, is less than 1 percent of the Earth’s volume (the Earth’s center lies 4,000 miles below the surface). The distance and small size beneath the surface, however, makes it difficult for scientists to measure with direct measurements, so instead they study shock waves triggered by earthquakes.
When a large earthquake occurs, the resulting shock waves, or seismic waves, bounce back and forth from one side of the Earth to the other like a ping-pong ball, said Baum. Seismic waves travel at different speeds through different layers of the Earth depending on its density, temperature and composition. Like a radiologist studying a patient’s internal organs, scientists around the world use instruments called seismographs to measure these oscillations and learn about our Earth’s inner workings.
Twenty years ago, researchers proposed the existence of a fifth layer using seismographic data. Since then, the evidence for the inner core has “been strengthened over time with more and more data,” Baum said. But his new study takes it further by analyzing an unprecedented seismogram.
“The breakthrough of this study is that we found a new way to model the core of Earth’s inner core,” Baum said. The team, he said, still has more evidence to prove that “the inner core actually exists.”
In the new study, the team observed multiple earthquakes across the Earth’s diameter — sometimes up to five times — something the researchers did not record in “seismic history,” noting that previous studies had documented only one bounce. They found that seismic waves travel through the inner core at different speeds than the surrounding core, depending on the direction of the wave.
In particular, waves passing through the inner core are slower when approaching the equator from an oblique angle. Meanwhile, waves passing through the outer inner core slow down as they pass through the equator.
Baum said the speed varies with wave direction due to a physical property called anisotropy, which allows a material to have different properties in different directions. We commonly see anisotropy in wood, which is easier to cut with its grain than against it.
The specificity of this inner core is subtle and not as sharp as other layers, Baum admits. For example, if you travel from the mantle to the outer core, you will most likely go from solid to liquid and experience different chemical compositions. But if you travel from inner core to inner core, you will see a change in crystal structure, but the same iron-nickel alloy.
Geophysicist John Tartuno, who was not involved in the research, proposed the idea of ​​an inner core, but this new data significantly strengthens the case that “the inner core actually has a different structure from the outer core.” “
“The existence of this intrinsic inner core makes us wonder how it could have formed,” said Tarduno, a professor of geophysics at the University of Rochester. The study authors said the formation of the inner core could be evidence of “a significant global event from the past” that triggered a change in Earth’s inner core.
Tartuno, researching how the inner core might have formed, has his own idea. His research suggests that the formation of this inner core may be linked to a shift in plate tectonics hundreds of millions of years ago. Thicker, older layers of oceanic crust sink until they accumulate at the bottom of the crust, affecting how heat escapes from the core, he says. This then changed how the inner core developed.
Tarduno said the new analysis is “exciting because it improves the case” for his plate tectonic mechanism.
“What we see in this inner core is actually a signal of a change in the regime of plate tectonics,” said Tarduno, who published his findings. Last year.
Both Tarduno and Baum hope that learning the origin of the inner core layers will help them understand more about how the magnetic field formed — and, by extension, how life can survive on Earth and other planets.
“The formation of the inner core is critical to creating a long-term habitable planet because the inner core drives the magnetic field, which drives the magnetosphere,” Tarduno said. “Without it, we would have gradually lost water from the planet.”
The inner core will help teach more about how other planets may or may not be habitable.“
