Earth’s Inner Core Falling Behind Planet’s Rotation 

Earth’s inner core appears to be slowing down relative the speed of our planet’s rotation on its axis. Find out how this affects our magnetic field and shortens the length of a day on our world.

Living as a travelling consultant for a couple of decades  had both advantages and disadvantages. One of the advantages was the opportunity to take in local attractions wherever I found myself.

Whenever I had a layover in Edmonton, Alberta, I’d stop by the TELUS World of Science. It houses the Zeidler Zone, one of North America’s best planetariums, as well as a state-of-the-art IMAX theatre.

One memorable IMAX film I saw there was Ring of Fire. It explained the fascinating geology of the region around the Pacific Rim where plate tectonics cause about 75% of Earth’s active volcanoes and over 90% of our planet’s earthquakes.

Eath’s Inner Core Can Rotate at Different Speeds

Professor Xiaodong Song has been studying the Ring of Fire and Earth’s inner core for over thirty years. Working at Columbia University back in 1996, he co-authored a study suggesting that Earth’s inner core can rotate at different speeds relative to our planet’s outer mantle and crust.

The Earth’s inner core is solid, floating inside a layer of molten metal about 5,000 kilometres below the planet surface. According to Professor Song’s findings, the core was rotating as much as one degree faster per annum than the rest of our planet, although some of his peers measured smaller variances.

Professor Song continues to study this phenomenon at Peking University, often collaborating with his colleague, Professor Yi Yang. Last month, they published a new paper in the journal Nature Geoscience.

Earthquakes Send Shock Waves Through Earth’s Centre

The two geophysicists reviewed an earthquake database going back to 1964 for clues about the workings of Earth’s inner core. Earthquakes send shock waves to the centre of the earth and back. Seismometers all over the world measure and record these waves.

The scientists compared data from earthquakes of the same magnitude that arose in the same place, but at different times. Since the quakes were practically identical, the shock waves they sent through the planet should have looked pretty much the same.

That’s assuming that the Earth’s inner core is stable. If the core was spinning differently at different times, the waves from two earthquakes would hit the core in different spots.

Analyzed Seismic Wave Records for Fluctuations

The different locations would create two different seismic wave patterns. The goal of the study was to analyze wave records in the database to look for fluctuations like this.

The researchers found that between the 1970s and the early 2000s, Earth’s inner core was spinning steadily and just a bit faster than our planet’s overall spin. By 2009, the interior spin matched Earth’s planetary spin, and now Earth’s inner core spins more slowly than the rest of our planet.

Based on the patterns the geophysicists observed, they predict that this trend may by cyclical. They’ve estimated that there could be another shift around the year 2040.

“Slowed Rotation Will Continue in the Coming Years”

We are hypothesizing that this [slowed rotation] will continue in the coming years and decades, and we should be able to see that in [our] relatively short human time frame,” Professor Song told Scientific American.

Don’t panic! We’e gotten so used to scientific findings leading to dire predictions that we tend to assume every new discovery is cataclysmic. However, scientists have been noticing volatility in Earth’s magnetic field and this spin variability may account for it.

The research may also explain why our planet’s rotation on its axis has been speeding up. Although the daily difference is less than the blink of an eye, the length of a day on Earth is getting very slightly shorter.

Magnetic Field and Length of Day Vital to Life on Earth

Both our magnetic field and the length of day are vital to life on Earth. For example, one of the main reasons the planet Mars appears lifeless is that it lost almost all of its magnetic field.

As a result, there was nothing to shield the red planet from the solar wind. Over time, charged particles from the sun stripped away the Martian atmosphere and water supply.

Similarly, Earth’s stable rotation prevents extreme temperatures, creating the optimal conditions for life to evolve, especially plant life. So, it’s fortunate that the variances we’re discussing are barely perceptible.

Reminds Us of Miraculous Nature of Pale Blue Dot

I’m not raising these points to dismay readers. However, this study reminds us of the miraculous nature of our “pale blue dot”.

Our home world has countless features working in harmony to provide the conditions to support life. Our dynamic geology, stable rotation and magnetic field are just three factors.

And Another Thing…

Our stable sun, our moon, our neighbouring planets, our atmosphere and even our solar system’s position in the galaxy are only a few of the other reasons behind our planet’s extraordinary capacity to support life. The more we discover about our planet, the more we appreciate its interrelatedness and its uncanny balance of living and non-living processes.

The researchers wound up an interview with Agence France-Press by saying, “We hope our study can motivate some researchers to build and test models which treat the whole Earth as an integrated dynamic system.”

We always have more to learn if we dare to know.

Learn more:

Why Earth’s Inner Core May Be Slowing Down
Earth’s inner core rotating slower than surface, study suggests
Multidecadal variation of the Earth’s inner-core rotation
Buried Tree May Explain Earth’s Magnetic Field
Magnetic Fields Attract Scientific Attention
Origin of Life Before Origin of Species – 4 Theories


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