Kamal Ghorui
The Earth’s magnetic field protects our planet from the harmful effects of solar radiation, thus allowing the development of life on Earth. It is known that the magnetosphere of our planet is generated due to the movement of molten metals in the liquid outer layer of the Earth’s core, resulting in electric currents through the geodynamo effect. However, based on new research, there might be something else about Earth’s magnetic field.Giant structures hidden beneath the mantle of Earth seem to have a very significant influence on the features of the Earth’s magnetosphere throughout long periods of time. The hidden structures affect the transfer of heat energy out of the core and consequently, the motion of molten metals that produce Earth’s magnetosphere. The research results are based on numerous geodynamic models, paleomagnetic data and seismic images of the inner part of Earth.Formation of Earth’s Magnetic FieldEarth’s magnetic field is formed inside the fluid outer core that exists at an average depth of 1,800 miles beneath the Earth’s surface, according to NASA. The heat escapes from the core, resulting in convection taking place in the layer of liquid metal in the core. The rotational movements result in the formation of electric currents that maintain the magnetic field of the Earth. This invisible force even stretches outside the Earth and protects the planet from the dangerous effects of charged particles from the Sun.Scientists were interested in studying only the core of the Earth until now, but new studies suggest that the mantle covering the core can also be a contributing factor.Giant mantles under the EarthThere are giant mantles called large low-shear velocity provinces (LLSVPs). They exist in the lower mantle of the Earth and were discovered using seismological waves due to the Earth’s quakes. In general, scientists claim that the features of such giant mantles are rather different compared to other mantle regions because of the higher temperatures, densities, and compositions.According to one article published in Nature Geoscience on persistent mantle domains beneath Africa and the Pacific Ocean, this issue can refer to old tectonic cycles that are necessary as they take part in the process of heat release from the core.
Earth’s magnetic field may be influenced by massive hidden “mantle giants”. Image credit – Wikimedia
Heat flow impact on the magnetic fieldIt is important to note that the aim of the current scientific research is connected with the core-mantle boundary that shows how the heat escapes the core. Scientists have concluded that it does not happen evenly; some regions of the mantle are better penetrated by heat from the core than others depending on temperature and composition. There is a notion that the non-uniform heat flow affects convection in the outer core.It was discovered through computer modeling that differences in the heat flow could cause asymmetry in the magnetic field, which would persist for some time. To put it differently, there are variations in the magnetic field according to the regions where the mantle affects the cooling process of the core.According to another study published in Nature Geoscience, non-uniform lateral heat flows lead to stable magnetic fields due to specific mantle heterogeneities. However, another study showed that the magnetic field properties during past geological eras were connected with mantle heterogeneity and different heat flows.What led scientists to think that the effect lasted millions of years?One of the reasons that scientists believe this theory has gained credibility is that the mantle structures look strikingly stable. According to scientists, dense and iron-rich mantle rocks may contribute to the long-standing nature of these large-scale formations. Over the course of hundreds of millions of years, the structures might continuously affect heat flow from the planet’s core.In addition, USGS scientists note that the amount of heat transfer across the core-mantle boundary is enormous and has been continuous throughout most of Earth’s history.A new approach towards understanding Earth’s interiorIt is important to state that the mantle itself does not produce the magnetic field, which is formed by motions within the liquid outer core. Nevertheless, more and more researchers are inclined to view the planet’s interior as an interconnected system.In this way, the mantle can behave as a control layer, which affects the heat loss from the core and its internal flow. In the long term, it may determine the magnetic field observed at the Earth’s surface.According to the researchers, their findings revolutionise the current understanding of Earth’s magnetic evolution. Rather than considering the magnetic process to be solely dependent on the core, the new model implies that deep Earth processes may affect the geomagnetic field.
