April 2, 2023

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Scientists have discovered a new core at the center of the Earth


Back in my day, there were only four layers of Earth: the crust, the mantle, the liquid outer core, and the solid inner core. Now, scientists have uncovered a new and distinct layer within our planet’s inner core, which could help inform the evolution of Earth’s magnetic field.

in a new study Released this weekA pair of seismologists at the Australian National University has documented new evidence of a 400-mile-thick solid ball of metal at the center of Earth’s inner core – like the smallest statue of a colossal planet-nesting Russian doll group. The new layer is made of an alloy of iron and nickel, like other parts of the core. The study found that it has a different crystal structure that causes shock waves from earthquakes to bounce back through the layer at different speeds than the surrounding core.

“It’s clear that the innermost inner core has something different from the outer layer,” said Than-Soon Pham, lead author of the study. We think atoms are the way [packed] In these two regions are slightly different.

Researchers are studying 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 planet. Geophysicists believe that the inner core may have formed less than a billion years ago, which is relatively young on a geological time scale. Study authors Explain The inner core grows outward by solidifying material from the liquid outer core, releasing heat and creating convection currents. This convection generates the Earth’s magnetic field.

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The Earth’s inner core appears to be slowing its rotation

Discovered in 1936 by Danish seismologist Inge Lehmann, the inner core makes up less than 1 percent of Earth’s volume (the center of the Earth is about 4,000 miles below the surface). However, the distance below the surface and its small size make it difficult for scientists to measure it with direct measurements, so instead they study the shock waves generated by earthquakes.

When a large earthquake strikes, Pham said, the resulting shock waves, or seismic waves, can bounce back and forth from one side of the Earth to the other like a ping-pong ball. Seismic waves travel at different speeds through the different layers of the earth depending on their density, temperature, and composition. Like a radiologist studying a patient’s internal organs, scientists use instruments known as seismometers around the world to measure these oscillations and learn about the inner workings of our Earth.

twenty years ago, the researchers used seismograph data and suggested the existence of a fifth layer. Since then, Pham said, the evidence for a deeper inner core has “become stronger over time with more and more data.” But his new study takes it further, analyzing unprecedented data for a seismograph.

“The breakthrough with this study is that we found a new way to sample the center of Earth’s inner core,” said Pham. He said the team has more evidence to show that “the innermost inner core does indeed exist.”

In the new study, the team observed multiple earthquakes crossing the Earth’s diameter—sometimes as many as five times—something the researchers did not record “in the history of seismology,” said Pham, who notes that previous studies have documented only one bounce. They found that the seismic waves passed through the inner inner core at different speeds than they did through the surrounding core, depending on the direction of the wave.

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Specifically, waves passing through the innermost inner core slowed down when approaching at an oblique angle to the equator. Meanwhile, waves passing through the outer inner core slowed down as they passed along the equator.

Pham said the speed likely varies based on the direction of the wave because of a physical property known as anisotropy, which allows matter to have different properties in different directions. We usually see anisotropy in wood, and it’s easier to cut along its grain than against it.

Pham admitted that the uniqueness of this innermost core is subtle and not as sharp as the other layers. For example, if you traveled from the mantle to the outer core, you would go from a mostly solid to a liquid and experience different chemical compositions. But if you travel from the inner core to the innermost core, you will see a transition in the crystal structure but the same alloy of iron and nickel.

The idea of ​​a deeper inner core has been proposed before, said geophysicist John Tarduno, who was not involved in the research, but this new data greatly strengthens the case that “there is in fact a deeper inner core with a different structure than the outer inner core.”

“The existence of this deeper inner core makes us think about how it formed,” said Tarduno, a professor of geophysics at the University of Rochester. The study authors said the formation of the deeper inner core could be evidence of a “significant global event from the past” that led to a change in Earth’s inner core.

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Tarduno, who is researching how the inner core forms, has his own idea. His research suggests that the formation of this innermost inner core could be related to a change in plate tectonics hundreds of millions of years ago. Presumably, ancient thick slabs of oceanic crust sank until they built up at the base of the mantle, affecting how heat flowed from the core. This later changed how the inner core grew.

Tarduno said this “new analysis is exciting because it supports the case” for the mechanism of its own plate tectonics.

said Tarduno, who published his findings last year.

Learning the origins of the inner layers of the core, Tarduno and Pham said, can help us understand more about how the magnetic field formed — and, in turn, how life can survive on Earth and other planets.

“The formation of the inner core was very important for establishing a long-term habitable planet because the inner core was feeding the magnetic field, which serves to provide magnetic shielding,” Tarduno said. “Otherwise, we would have been gradually losing water from the planet.”

Learning more about how the inner core can, in turn, help teach us more about how other planets may or may not be habitable.