Scientists: Earth's Inner Core Has Slowed Its Rotation

Perhaps someone decided to stop the Earth and step down.

The dense inner core of the Earth, primarily composed of iron and nickel, may rotate faster or slower than other parts of the planet. Theoretically, this possibility has been considered since it is surrounded by a liquid outer core and mantle, meaning the Earth is not a solid rigid structure. However, the rotation parameters of all its layers largely coincide.

A recent study conducted by a group of scientists led by representatives from the University of Southern California showed that the inner core has begun to lag in rotation compared to other parts of the planet. Studying the inner core located about 4,800 kilometers deep is not straightforward. Seismic waves caused by earthquakes are examined for this purpose. Sensitive instruments can track them over great distances, and depending on the medium through which the waves propagate, they change their characteristics, refracting, reflecting, and slowing down differently.

The idea behind studying the rotation parameters of the inner core was to gather a large dataset from the same locations where repeated earthquakes occur. This would allow for a better understanding of the Earth's interior structure and its shifts over time. The authors of the study set out to analyze the profile of 121 earthquakes. All of them occurred between 1991 and 2023 in the South Sandwich Islands region, with signals recorded by stations in North America.

The analysis of the observed seismic waves and their characteristics led to the conclusion that from 2003 to 2008, the inner core was rotating slightly faster than the mantle and the Earth's crust. Then, a slowdown occurred. It began to lag in rotation compared to the crust. The discrepancy is only a fraction of a degree per year. But even such a minimal change requires a tremendous force.

The authors of the study suggest that certain processes in the liquid outer core, which caused gravitational disturbances, led to the slowdown of the inner core. Part of this slowdown will also be transmitted to the Earth's surface. Technically, this will result in an increase in the length of days. However, this will be very difficult to notice, as the amount will be up to a thousandth of a second per day. Moreover, it is possible that the inner core may accelerate again.

Making accurate predictions about its behavior is challenging, as the interaction of the Earth's internal structures is not fully understood. It is also difficult to predict the consequences of changes in the rotation speed of the planet's core. However, there is no need to expect an apocalypse. The authors of the study believe that this variable speed may be linked to the movement of the Earth's magnetic field poles, which are known to migrate over time.