Scientists Confirm Earth’s Inner Core Is Solid

Posted: Oct 21 2018, 1:38pm CDT | by , in Latest Science News


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Scientists Confirm Earth’s Inner Core is Solid
Credit: NASA/JPL

The findings could help us understand how Earth was formed.

It is widely accepted that Earth’s inner core is solid but the idea had never been conclusively proved. Now, researchers have detected shear waves in the inner core and used them to explore our planet's interior. This is the first time researchers have direct evidence that Earth’s inner core is solid.

Shear waves or "J waves" is a type of wave which can only travel through solid objects. But it has not been detected until now.

“We found the inner core is indeed solid, but we also found that it's softer than previously thought,” said Professor Hrvoje Tkalčić from Australian National University (ANU).

“It turns out - if our results are correct - the inner core shares some similar elastic properties with gold and platinum. The inner core is like a time capsule, if we understand it we'll understand how the planet was formed, and how it evolves.”

The inner core is Earth's deepest layer which is surrounded by a liquid outer core. It is among the final frontiers for understanding the history of Earth. However, the biggest challenge is high pressure and extreme temperatures.

Shear waves can also provide information on inner core’s solidity and its composition. But the waves in inner core are so small and feeble they can't be observed directly. Researchers developed a creative approach to detect J waves in the earthquake coda correlation wavefield. The method originally looks at the similarities between the signals at two receivers after a major earthquake.

“We're throwing away the first three hours of the seismogram and what we're looking at is between three and 10 hours after a large earthquake happens. We want to get rid of the big signals," said Dr Tkalčic.

"Using a global network of stations, we take every single receiver pair and every single large earthquake - that's many combinations - and we measure the similarity between the seismograms. That's called cross correlation, or the measure of similarity. From those similarities we construct a global correlogram - a sort of fingerprint of the earth."

These results can be used to determine the existence and speed of J waves in the inner core, which could eventually help answer some fundamental questions about this region.

“For instance we don't know yet what the exact temperature of the inner core is, what the age of the inner core is, or how quickly it solidifies, but with these new advances in global seismology, we are slowly getting there,” said Dr Tkalčić.

“The understanding of the Earth's inner core has direct consequences for the generation and maintenance of the geomagnetic field, and without that geomagnetic field there would be no life on the Earth's surface.”

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The Author

<a href="/latest_stories/all/all/47" rel="author">Hira Bashir</a>
The latest discoveries in science are the passion of Hira Bashir (). With years of experience, she is able to spot the most interesting new achievements of scientists around the world and cover them in easy to understand reporting.




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