Recently, a study has been published in which it is said that the earth core has suffered a break and that this event has an influence on different aspects of the planet, such as the magnetic field or the climate.
As a result of this publication, some voices suggesting exaggerated and catastrophic consequences. It is important to analyze these news with a critical vision. Without minimizing the great impact of scientific discoveries on the functioning of our planet —even with so many mysteries— do not fall into simplicity or drama.
To understand this news, we must first know the internal structure of our planet, which is made up of different layers. In the center is located the inner core of the earth, a solid sphere of iron and nickel with a radius of 1,220 km. It is surrounded by a 2,260 km thick layer of similar composition, but in a molten state, the outer core.
The first thing to make clear is that the Earth’s core has not stopped. Our planet with all its layers is rotating in such a way that it takes about 24 hours to complete one revolution.
The convection movements in this fluid layer, together with the terrestrial rotation, generate the magnetic field that protects our planet from particles that arrive from the Sun and from space. Around the nucleus we find the mantoabout 2900 km thick and, above it, the Cortex terrestrial layer on which we live, only 10 to 50 km thick.
The first thing to make clear is that the kernel has not stopped. The Earth with all its layers is rotating in such a way that it takes approximately 24 hours to complete one revolution.
Until now it was thought that the inner core rotated a little faster than the mantle and crust—this is called superrotation— so that it was gaining about a tenth of a degree each year.
According to this new study, Earth’s core would have slowed down until reaching the same speed of rotation as the outermost layers or even a slightly lower speed. These relative speed differences are very small.
The example of the car on the highway
Let’s imagine, as an example, that we are going on the highway at 120 km/h and another car passes us at 121 km/h. Through the window we will see that he is overtaking us little by little. If now the other vehicle brakes and goes to 120 km/h we will see it “immobile” next to our car. It keeps moving though, just like us.
To come to the conclusion that the core now spins more slowly, the researchers selected earthquakes originated in the South Sandwich Islands, in the southern part of the Atlantic Ocean. And they studied the signal recorded at an observatory in Alaska, almost on the other side of the planet.
In the same way, the core would have slowed down and, now, rotating at the same speed as the mantle and crust, from the Earth’s surface we would see it stopped.
In this way they were able to analyze the time it took for the waves that had passed through the Earth’s core always following the same trajectories. They observed that the waves took different times to cross the core at different times.
Different areas of the nucleus can have different properties, which means that waves take longer to cross some areas than others. So they concluded that if the travel time of the waves changed over the years, it’s because the inner core was getting ahead of the crust.
In other words, if for waves emitted and recorded at the same points on the surface we obtain different results depending on the time. It means that the waves are going through different areas of the nucleus, that is, it is rotating at a different speed than the surface of the Earth.
If for seismic waves emitted and recorded at the same points on the surface we obtain different results depending on the time, it means that they go through different areas of the core, that is, it is rotating at a different speed.
This slight shift in core rotation isn’t the first time it’s happened. The data show another similar event in the 1970s. This suggests that the phenomenon repeats itself with a periodicity of about seven decades.
Association with geophysical phenomena
Curiously, this same frequency also appears in other geophysical observables, such as the geomagnetic fieldthe day length or the weather. Which suggests they may be related.
Currently, it is thought that this phenomenon of periodic variation of core rotation must be:
- To the electromagnetic interaction between the inner and outer core that tends to accelerate the inner core
- To the gravitational coupling with the mantle, which forces it to return to rhythm.
Does the study say that the Earth’s core stopped dead in its tracks in 2009 and is going to start spinning in the opposite direction? No, it’s just changed its speed relative to the crust.
This has happened before, and on several occasions
Throughout history, the magnetic field has already been reversed many times. Does this slowdown of the Earth’s core suggest a new imminent reversal of the poles or could the magnetic field disappear? No, the nucleus continues to spin and the magnetic field will continue to be generated.
Will this phenomenon have implications for the climate? The article proposes that there could be some relationship, but that the origin of the multidecadal variations in the climate is not yet fully known. Furthermore, it does not seem likely that such small changes in the rotation of the nucleus could have really appreciable effects.
As we can see, the dynamics of the Earth is a system of great complexity and there are a multitude of interconnected factors that determine the characteristics and evolution of our planet.
The long history of Earth compared to our study of it makes understanding its evolution a great challenge. Discoveries like this are a sample of the efforts of science to understand more and more how the planet where we live works.
This article was originally published on Agency WITHOUTC. Read the original.