Great Balls of Fire: Earth has Fifth Layer As Study Finds 644Km-Wide Metal Ball at Core

The inner structure of the Earth comprises four major components: the crust - which is the thin outer later of our planet, on which we live; the mantle, the super-hot outer core, and the inner core - the hottest part of the Earth. However, scientists have been suggesting that our planet actually has a fifth layer.

Our planet Earth has five major layers instead of four, a major new study has claimed. There is a ball of iron possibly 400 miles (644 kilometers) wide, lodged deep within Earth’s metallic core, according to the latest research, carried out by scientists in Australia.

In plain terms, Earth is rather like an onion, with multiple layers, which huge strides in seismology have allowed scientists to analyze. If we begin at the exterior, these layers are: the crust (where we live), the mantle, the outer core, and the inner core. Each of the layers has its specific properties, composition, and characteristics, with the latter affecting key processes taking place on Earth. There had been speculation regarding the existence of an additional layer as far back as 20 years ago, which the new study by the geoscientists claims to have confirmed.

For their research, Thanh-Son Phạm, a seismologist and postdoctoral fellow, and Hrvoje Tkalčić, of the Research School of Earth Sciences at Australian National University in Australia's capital Canberra, used new data sets collected by measuring seismic waves (vibrations from earthquakes, volcanoes, etc) as they passed through the Earth’s center. It was this that allowed them to detect the mysterious inner core, as they revealed in their paper, published in the journal Nature Communications.

“In this study, for the first time, we report observations of seismic waves originating from powerful earthquakes traveling back and forth from one side of the globe to the other up to five times like a ricochet,” study co-author Dr Thanh-Son Phạm was cited as saying by the media.

Pham went on to explain just why this layer had not been observed before, clarifying that it was very similar in composition to the structure above it, as both are composed of iron-nickel alloy, interspersed with trace amounts of other elements.

“Additionally, the transition from the innermost (solid) ball to the outer shell of the inner core (also solid shell) seems rather gradational than sharp. That is why we cannot observe it via direct reflections of seismic waves from it,” Pham said.

The researchers used instruments that detect the vibrational waves to discover that the "innermost inner" core, hidden at a depth of more than 1,600 kilometers beneath our feet, is characterized by anisotropy: a physical property which has a different value when measured in different directions, an example being wood which is stronger along the grain than across it.

The scientists studied how quickly seismic waves traveled through this layer in different directions. Their observations led them to determine that the "innermost inner" core altered the speed of those vibrations in a manner that was distinctly different from how the layer above it [the center core’s outer shell] did.

When asked what their discovery implied, Phạm said that it could offer scientists a better understanding of Earth’s magnetic field, how it has evolved, and, “gives us a glimpse of what might have happened with other planets".

“Take Mars as an example. We don’t understand yet why [Mars’ magnetic field] ceased to exist in the past,” Pham said.