Innermost inner core the ‘bone of the earth’
Australian research has unveiled an iron ball with a radius of about 65km could lie at the centre of our planet.
Large-magnitude earthquakes have helped seismologists unveil what could be at the heart of our planet’s core: a ball of iron.
Researchers at the Australian National University have studied the seismic waves from 200 earthquakes between 2010 to 2019, and results indicate the potential presence of another component in Earth’s makeup, an innermost inner core with a radius of about 650km.
Debated and hypothesised since 2002, the existence of an innermost inner core is supported by Thanh-Son Pham and Hrvoje Tkalcic’s latest findings, discovered through seismic stacking, a technique that uses multiple seismometers to capture parts of energy.
“We are afraid of large earthquakes because of the damage they can cause and the victims, but at the same time, they help us to illuminate the Earth,” Professor Tkalcic said. The iron-nickel alloy comprising the inner core is suggested to be anisotropic, causing seismic waves to differ in speed and direction when it passes through.
“The outer shell, it’s well established that the waves move slowly in the equatorial direction … In the innermost inner core that slowest direction is not equatorial, but it’s forming an oblique angle with something between equatorial and the rotation axis of the Earth, like a spin axis,” Professor Tkalcic said.
The speed and direction at which seismic waves travel is important, with the timing and measurement of wave arrival times revealing the properties of the innermost inner core.
The ANU researchers found a seismic wave from an earthquake reverberated along the entire Earth’s diameter up to five times.
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