Team geologists have found evidence for the first time that two age-old, ultra-hot, continent-sized structures hidden beneath the Earth have been shaping the planet’s magnetic field for the past 265 million years.
These two masses, known as gigantic low shear velocity provinces (LLSVPs), are part of the catalog of the planet’s most enormous and enigmatic features. Current estimates are that each is comparable in size to the African continent, although they remain buried at a depth of 2,900 kilometers.
Low-lying surface vertical velocity (LLVV) regions form irregular areas of the Earth’s mantle, not defined blocks of rock or metal as you might imagine. Inside them, the mantle material is hotter, denser, and chemically different from the surrounding material. They are also notable because they are surrounded by a “ring” of cooler material through which seismic waves travel faster.
Geologists had suspected these anomalies since the slow 1970s and were able to confirm them two decades later. After another 10 years of research, they now point directly to them as structures capable of modifying the Earth’s magnetic field.
LLSVPs change the behavior of the kernel
According to a study published this week in The science of nature and led by scientists at the University of Liverpool, temperature differences between the LLSVP and the surrounding mantle material change the way liquid iron flows in the core. This movement of iron is responsible for generating the Earth’s magnetic field.
In summary, frigid and ultrahot zones in the mantle accelerate or decelerate the flow of liquid iron depending on the region, creating asymmetry. This inequality causes the magnetic field to take on the irregular shape we see today.
The team analyzed available evidence about the mantle and ran simulations on supercomputers. They compared what the magnetic field should look like if the mantle were uniform with its behavior when it covers these heterogeneous regions with structures. They then compared both scenarios with real magnetic field data. Only the model including LLSVP reproduced the same irregularities, tilts, and patterns that are currently observed.
Geodynamo simulations also showed that some parts of the magnetic field have remained relatively stable for hundreds of millions of years, while others have changed significantly.
“These findings also have important implications for questions about ancient continental configurations – such as the formation and breakup of Pangea – and may help resolve long-standing uncertainties about ancient climate, paleobiology and the formation of natural resources,” Andy Biggin, first author of the study and professor of geomagnetism at the University of Liverpool, said in a press release. release.
“In these areas it was assumed that the Earth’s magnetic field, averaged over long periods, behaves like a perfect bar magnet aligned with the planet’s rotation axis. Our findings are that this may not be entirely true,“ he added.
This story originally appeared on WIRED in Spanish and was translated from Spanish.