Scientists discover the fifth layer of Earth

As some of you might know, the Earth comprises of four layers, crust (where we live), mantle, outer core and inner core. While the world knows more or less about all the first three layers, not much has been known about the inner core, considered as the deepest layer of the Earth. However, recently, in the aftermath of various earthquakes, scientists based at the Australian National University have discovered more about it. How? By simply measuring the velocity at which the seismic waves enter and pass through the Earth’s inner core. To put matters in perspective, the seismic waves travel directly through the centre of the Earth and come out of the opposite side where the earthquake is triggered. But they don’t stay here for more than a few seconds or minutes after which they return back to their source. For instance, the team analysed an earthquake that was born in Alaska, triggered in the south Atlantic Ocean and then reverted to Alaska. Through this extensive process, geologists have found evidence of a distinct later that they are now calling as the innermost inner core.   

Sources cite that data from over 200 earthquakes with the magnitude of 6 and above from the last decade have been used for this study. The team of researchers have defined the layer as a solid “metallic ball” that exists in the middle of the inner core.  

The findings of the research have been published in the journal Nature Communications and posits that exploring the Earth’s centre, especially the inner core is also significant when it comes to understanding planetary formation and evolution.   

What’s interesting here is that the existence of the innermost inner core was hypothesised not recently, but more than two decades ago. Now, there’s just enough evidence to support it.  

In case you have been wondering about the composition of the fifth layer, it is mainly made up of iron and nickel alloy. This in turn was studied through the process of anisotropy. Here, the speed of seismic waves, i.e. the rate at which they go up or slow down through the Earth’s inner core is measured, apart from the trajectory they take. What they discovered is that the seismic waves travel repeatedly through the innermost inner core, that too from different angles; thus making the fifth layer highly influential.  

Anisotropy also helped study the variation of time for seismic waves in case of different earthquakes. This in turn revealed that the crystallised structure of innermost inner core and that of the outer core are widely different. The team of researchers believe that this could have been a result of a significant global event that impacted the evolution of the Earth to such a scale.