From seismic waves, scientists discovered the fifth inner layer of the Earth – it is a solid metallic ball
If we have recently received the news that the Earth’s core has changed its rotation, this time geologists have gone further by discovering that the core actually has another layer of action in its interior. The researchers analyzed data from about 200 magnitude 6 earthquakes, which produce seismic waves that travel directly through the center of the Earth.
The team from the Australian National University measured the speeds at which these seismic waves penetrate and pass through the Earth’s inner core, making it possible to deduce whether they are passing through a solid or molten layer. The team believes they have found evidence of the existence of a distinct layer within the Earth’s core, known as the inner core.
So far, four layers of Earth’s structure have been identified. These are the crust, mantle, outer core and inner core. The new findings indicate that there is a fifth layer below, and that it is a solid “metal ball” that sits at the center of the core. The conclusions of the study were published in the journal Nature Communications. The existence of an internal metallic ball inside the inner core was hypothesized about 20 years ago, but until now its existence had not been proven.
Seismic waves produced by an earthquake that travel directly through the center of the Earth and can be detected on the opposite side of the globe. The waves then recover and travel back to the source of the earthquake. For example, the team studied an earthquake that originated in Alaska. The waves bounced off somewhere in the southern Indian Ocean, before traveling back towards Alaska. When waveforms recorded by a large number of global seismic stations overlap due to these bounces, as many as five reverberations from an earthquake can be seen along the Earth’s diameter.
The researchers studied the anisotropy of the iron-nickel alloy that makes up the interior of the Earth’s core, which determines whether waves accelerate or decelerate depending on the direction in which they pass through the core material. They found that the crystalline structure of the innermost region of the inner core is probably different from that of the outer shell. The team suspects that a major global event may have occurred at some point in Earth’s evolution, causing a significant change in the crystalline structure of the inner core.
Up to five times reverberating waves through Earth’s center and sharply anisotropic inner core