Earth's Core Confirmed to Be Solid After 80 Years of Study

It has long been believed that Earth has a solid iron core but no proof has ever been found and it has been heralded as the 'holy grail' of global seismology.

Earth's core confirmed to be solid. Image credit: Kelvinsong/Wikipedia (CC BY-SA 3.0)

The issue has finally been put to bed by re-purposing a technique that was first used to measure the thickness of the Antarctic ice sheet.

Researchers built a 'fingerprint' of our planet from the echoes of earthquakes and found that the innermost region of the planet is indeed solid, but not as hard as once scientists believed it to be.

Associate Professor Hrvoje Tkalcic and PhD Scholar Than-Son Pham from the Australia National University (ANU) studied shear waves, or 'J waves', in the Earth's inner core.

J waves are produced by earthquakes and only travel through solid objects.

Inner shear waves can not be directly observed as they are of such little energy so the researchers looked for a creative way to detect them. To do this they looked at the similarities between the signals received at different locations after major earthquakes.

'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,' Dr Tkalcic said.

These earthquake 'echoes' were compared to many others from different readings of the same earthquakes and this produced a 'fingerprint of the Earth'.

The theory that Earth has a solid core was first proposed in 1936 when female Danish seismologist Inge Lehmann reanalysed data from the magnitude-7.3 1929 earthquake that struck New Zealand's south island.

Detectors in Europe picked up the waves and experts realised this would be impossible if the core was liquid, as it was thought to be in the 19th and early 20th centuries.

This theory became widely accepted and is taught to schoolchildren today but it had never been conclusively proved.

'We found the inner core is indeed solid, but we also found that it's softer than previously thought,' Associate Professor Tkalčić explains.

'It turns out - if our results are correct - the inner core shares some similar elastic properties with gold and platinum. (Tasnim News Agency)

YOU MAY ALSO LIKE

New Study Shows the Amazon Makes Its Own Rainy Season

A new study gives the first observational evidence that the southern Amazon rainforest triggers its own rainy season using water vapor from plant leaves. The finding helps explain why deforestation in this region is linked with reduced rainfall.

Asteroid 2002 AJ129 to Fly Safely Past Earth February 4

Asteroid 2002 AJ129 will make a close approach to Earth on Feb. 4, 2018 at 1:30 p.m. PST (4:30 p.m. EST / 21:30 UTC). At the time of closest approach, the asteroid will be no closer than 10 times the distance between Earth and the Moon.

Ganymede may harbor 'club sandwich' of oceans and ice

The largest moon in our solar system, a companion to Jupiter named Ganymede, might have ice and oceans stacked up in several layers like a club sandwich, according to new NASA-funded research that models the moon's makeup.

Modern pollutants can reach deep fossil aquifers

Contemporary pollutants can reach deep wells that tap fossil aquifers, says a study by an international team of researchers.

Daily Handful of Nuts Reduces Disease Risk

The next time you’re hungry for a snack, you may want to grab a handful of nuts, as new research suggests they lower the risk of heart disease, cancer and other diseases.

Soil Bacterium Tapped for Penicillin Guard Duty

A common soil bacterium may hold the key to preserving the germ-killing power of penicillin. U.S. Department of Agriculture (USDA) scientists in Peoria, Illinois, helped mass produce the antibiotic during World War II to treat Allied soldiers and later civilians. But decades of widespread use has since enabled some germs to develop resistance to it.