The Earth's core is changing shape: geophysicists have discovered a phenomenon with unpredictable consequences.

A Tough Nut to Crack

Theoretically penetrating the Earth's core, geophysicists continue to be amazed by it. The core is found to be iron-rich and complex. It is liquid on the outside and solid on the inside. The diameter of this so-called inner core is 2,440 kilometers. Like a nut in a candy, this sphere, roughly the size of Pluto, floats in a sea of molten iron "syrup."

The Earth, along with everything on its surface, and the "nut" rotate in the same direction but at different speeds. The solid inner core spins slightly faster. However, recently, it has started to slow down relative to the surface and its liquid surroundings. The "nut" seems to have stopped and even moved in the opposite direction – the surface has begun to overtake it.

Many scientists, including geophysicist John Vidale and his colleagues from the University of Southern California (UCLA), have reported these changes. They have now noticed new peculiarities: the "nut" has started to change shape.

The discoveries, which the geophysicist described as incredible, were made using seismic waves.

Initially, understanding how the inner core rotates was aided by nuclear weapons tests, including those conducted by the USSR in Novaya Zemlya. The Americans monitored these tests, recording both the seismic waves themselves and how they reflected off the inner core. The recordings have been preserved, and Vidale and his colleagues analyzed them.

Subsequently, scientists studied seismic waves from nearly 200 earthquakes that literally "pierced" the Earth. The data analysis indicated that something else, aside from the rotation of the inner core, influences the nature of wave propagation – some processes at the boundary between the liquid and solid states.

The scientists concluded that the best assumption is that the shape of the "nut" is changing. However, they do not yet know how – whether the core is swelling or if protrusions are forming on it. Something is distorting the core.

The researchers are testing their hypothesis, planning new studies, and in the meantime, they are publishing the results of their current research in the journal Nature Geoscience.

It Could Be Worse

What do the processes affecting the behavior and shape of the core threaten? No one knows for sure. The uncertainty is alarming. After all, it is likely that the massive spinning iron ball of the Earth's inner core creates the geomagnetic field that protects us from cosmic and solar radiation, preventing us from being devastated by magnetic storms. And if the rotation slows down, does the field weaken as well? Signs of this are indeed present. God forbid, if the core stops, and its protective field disappears entirely – every man for himself...

If the "inner" rotation somehow affects the rotation of the Earth as a whole, it will begin to slow down – increasingly so. The days, which have already slightly lengthened, will become noticeably longer. Not scary – people will just have more time.

Such events have occurred in the history of our planet – unfortunately, there were no people around then. For instance, 530 million years ago, there were 21 hours in a day and 420 days in a year. The Earth spun so quickly but gradually slowed down.

The phenomenon of deceleration was confirmed by cyanobacteria or blue-green algae, which recorded the changes in their bodies. When light fell on them, the algae grew vertically; in the dark, they grew horizontally. By studying the deposits of these fossils from different geological eras, scientists determined the duration of those ancient days.

BY THE WAY

How do we know that the Earth's core is iron?

Until recently, there were two main arguments. First, the average specific weight of the entire Earth is much higher than that of the rocks in its outer layers. This means there is something heavier and denser inside.

Second, iron is the most suitable material by specific weight – one of the most abundant elements in the universe.

The third argument was provided two years ago by French scientists from several research organizations (CEA DAM-DIF, Université Paris-Saclay, ESRF, BP220, F-38043 Grenoble Cedex, European Synchrotron Radiation Facility). They synthesized monocrystalline iron – the very material that, according to prevailing theoretical concepts, exists in the Earth's core.

Scientists synthesized the iron of the Earth's core. Photo: University of Utah

Deep iron, or hexaferrum, was obtained from α-iron (ferrite) after its sample was subjected to a monstrous pressure of 7 GigaPascals using diamonds. This is nearly 70 kilograms per square centimeter. The pressure caused the temperature of the sample to soar by 800 degrees;

It turned out that the properties of hexaferrum depend on the spatial orientation of its crystals – vibrations in such iron propagate differently in different directions.

The discovered phenomenon explained another one that puzzled geophysicists back in the 1980s. It was again related to seismic waves. Those traveling from pole to pole penetrated the Earth faster than those spreading across the perpendicular axis – through the equator. If the inner core is made of monocrystalline iron, then everything is correct – that's how it should be.