Did you know that the center of the earth may turn at a different speed than the surface?

Indeed, scientists think that the inner core may recently have slowed down, and may possibly spin in the opposite direction of the Earth’s surface in the near future!

This is not the plot of the next science fiction movie, but rather, a surprising finding from a study that scientists published in Nature Geoscience. Let’s get to the core of how the Earth works to better understand the scientific findings.

How is the Earth Made? What’s So Special About the Core? 

The Earth is composed of several layers:  

• the crust, which is the surface we live on; 
• the mantle, which begins below the crust and ends at the outer core;
• the outer core, which is made of hot liquid metal; and 
• the inner core, which is believed to be a solid metal ball of iron and nickel. 

Because the inner core is so deep in the Earth, it is incredibly difficult to study. Scientists have used various methods to determine how, or even if, the core spins.

Learning about the core is important though, because it may help explain how the Earth’s center affects its magnetic field, the speed of the planet’s rotation, and by extension - the length of a day. Scientists believe the difference in speed is possible because of the liquid metal layer (outer core) that surrounds the inner core. The inner core “floats” in the liquid metal, which allows it to rotate independently of the rest of Earth’s layers.  

What the Study Reveals

The study’s authors propose that the Earth's inner core may be experiencing a slowdown.

They think that this difference can be measured by observing a change in how seismic waves pass through the Earth’s center during an earthquake. Older data shows a lot of change in the wave patterns while passing through the core, but recent data shows the changes are no longer as visible.

After analyzing the patterns of seismic waves through the decades, scientists theorize that the Earth’s inner core changes its rotational speed and perhaps its direction, over time. Different studies have concluded that these changes in speed follow a pattern that may range from 20 to 70 years.

The observed changes in the inner core’s behavior are likely caused by the gravitational and magnetic forces acting on it. The gravitational pull is the result of the Earth's heavy mantle. The magnetic field is produced by the movement of liquid iron in the outer core. Although the core’s spin seems to be independent, we know that all layers of the Earth interact and experience effects from each other. 

We have much more to learn about Earth and its physical processes. Scientists say that many years of continuous recording and study of seismic data are necessary to get answers. Until then, we must be patient. The investigation of this phenomenon will definitely lead us under the surface and into the core of understanding our planet!

Sources: Nature, NY Times, Washington Post, CNN, Smithsonian, NatGeo