by OPINION | Don Lincoln is a scientist at Fermi National Accelerator Laboratory, a research laboratory for the US Department of Energy. He is the author of several scientific books and most recently “Einstein’s Unfinished Dream”. It also produces science education videos. The opinions expressed in this article are your own.
If a person is said to be grounded, it means they are logical and balanced – stable people who can be trusted to give a careful and considered opinion. The very meaning of the term comes from the solidity and stability of the ground we walk on. However, recent media reports have painted a different picture of what’s going on underground—one in which the Earth’s core is doing some pretty amazing and unexpected things.
A study published in the journal Nature Geoscience describes a change in the movement of the Earth’s core – and with this news, headlines have multiplied, with some claiming that the Earth’s core has stopped spinning.
But this interpretation is actually misleading. The Earth’s core literally does not stop. however it is changing.
The Earth is not a solid ball. It consists of many layers. There is the innermost core, which is a solid sphere about the same size as the planet Mars. Surrounding it is the outer core, which is liquid rock. The next layer is the mantle, which has a caramel-like texture. Finally there is the cortex, which is the outermost layer – where we live.
If the Earth were a solid ball, each layer would rotate synchronously once a day. However, due to the layered structure, it is possible that the Earth’s core rotates at a slightly different rate than the surface and other layers. And in the 1990s, researchers used geological data collected in previous decades to show that the Earth’s core was rotating slightly faster than the rest of the Earth. The difference is small – about 1º per year faster than the Earth’s surface.
This latest study found that the rotation of the core slows down. It does not stop, but is now rotating at the same speed as the Earth. Also, it appears that the core may be slowing down, so it will end up spinning a little slower than Earth. This is scientifically interesting, but far less dramatic than some headlines would suggest.
Researchers have seen this periodic change in the speed of Earth’s core rotation before, and they still debate the rate at which it happens, with some suggesting a 70-year cycle while others suggest a much faster cycle.
For geologists, this is exciting. The Earth’s radius is only 6437 kilometers and the deepest hole it has ever dug is just over 12 kilometers deep. The crust beneath Earth’s continents can be up to 40 miles (64 km) deep, although the crust beneath the oceans can be much thinner. Understanding the Earth’s structure requires indirect methods, including studying the speed at which seismic waves travel through the Earth or studying the rich trove of data on how the sound of nuclear explosions travels through the Earth. With few exceptions, nuclear testing ceased in the mid-1990s.
Headlines aside, this recent study confirms previous results showing that the rotation of the inner core changes over time and helps geologists try to understand the mechanism by which these changes occur. What geologists are interested in is the interplay between the gravitational and magnetic forces inside the Earth that speed up and slow down the rotation of the core.
However, there is a far more important lesson to be learned here, and that is that scientists are able to make extremely precise measurements of what is going on beneath the Earth’s surface. This is very important – after all, it is the only planet we have. What’s happening beneath the Earth could have huge consequences for humanity.
Consider the supervolcano lying dormant beneath Yellowstone National Park. [nos Estados Unidos]. Every half million years or so (sometimes more), Yellowstone erupts in a volcano that spews hundreds or thousands of times more ash into the atmosphere than the 1980 eruption of Mount St. [St. Helens]. While some fear that the Yellowstone supervolcano may be destined to erupt again, recent studies have eased concerns that the danger is imminent. However, given the magnitude of damage such an eruption could cause, it is imperative that geologists continue to monitor what is happening.
And there is much more going on beneath the surface of the Earth. Earth’s magnetic field guides ships at sea and lost travelers. It is easy to believe that this compass it will always work, however geologists have shown that the Earth’s magnetic field is not constant. In fact, every few hundred thousand years, the field reverses, with magnetic south becoming north and vice versa.
And while a reversal is probably not imminent, the position of magnetic north changes even on human time scales. At the beginning of the 19th century it was found in northern Canada, however, it has moved to the Arctic Ocean and is now approaching Siberia.
By understanding more about Earth’s inner workings, scientists can help humanity prepare for major changes in Earth’s magnetic field. If this were the case, we would have to change all compass-based instruments for navigation.
We only have one planet and what happens on it can affect us all. It’s imperative that geologists continue to study what’s going on inside our globe—and this recent measurement of changes in the rotation of Earth’s core gives us some comfort that we’re keeping up.
And, let’s face it, that’s pretty cool.
