A team of Geologists have discovered for the first time evidence that two extremely hot, continent-sized ancient structures hidden beneath the Earth shaped the atmosphere. the planet’s magnetic field for 265 million years.
These two masses, known as the Large Low Shear Velocity Provinces (LLSVP), are part of the catalog of the largest and most enigmatic objects on the planet. Current estimates place each of them as comparable in size to the African continent, although they remain buried at a depth of 2,900 kilometers.
Regions of low surface vertical velocity (LLVV) form irregular areas of the Earth’s mantle, not defined blocks of rock or metal as one might imagine. Inside them, the mantle material is warmer, denser, and chemically different from the surrounding material. They are also notable because they are surrounded by a “ring” of colder material, where seismic waves propagate faster.
Geologists suspected the existence of these anomalies since the late 1970s and were able to confirm them two decades later. After another ten years of research, they now directly designate them as structures capable of modifying the Earth’s magnetic field.
LLSVPs modify kernel behavior
According to a study published this week in Natural geosciences and led by researchers at the University of Liverpool, temperature differences between the LLSVP and the surrounding mantle material change the way liquid iron flows into the core. This movement of iron is responsible for generating the Earth’s magnetic field.
Taken together, cold and ultrahot zones in the mantle speed up or slow down the flow of liquid iron depending on the region, creating an asymmetry. This inequality contributes to the magnetic field taking on the irregular shape we observe today.
The team analyzed the available evidence on the mantle and ran simulations on supercomputers. They compared what the magnetic field would look like if the mantle was uniform and how it behaved when it included these heterogeneous regions with structures. They then compared the two scenarios with real magnetic field data. Only the model integrating the LLSVP reproduced the same irregularities, inclinations and patterns currently observed.
Geodynamo simulations also revealed that some parts of the magnetic field have remained relatively stable for hundreds of millions of years, while others have changed remarkably.
“These findings also have important implications for questions surrounding ancient continental configurations, such as the formation and fragmentation of Pangea, and could help resolve long-standing uncertainties regarding ancient climate, paleobiology and the formation of natural resources,” said Andy Biggin, first author of the study and professor of geomagnetism at the University of Liverpool, in a press release. release.
“These areas assumed that the Earth’s magnetic field, averaged over long periods, behaved like a perfect bar magnet aligned with the planet’s axis of rotation. Our findings are that this may not be entirely true,» he added.
This story was originally published in WIRED in spanish and was translated from Spanish.
