Les ondes sismiques nous permettent d'imager la structure du manteau profond. © 3D motion, Adobe Stock

We now have a better understanding of what lies beneath the earth’s mantle

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By spinning liquid sodium around a 23-ton sphere, geophysicists at the University of Maryland are simulating conditions at our planet’s core. Aim of the game: to understand why Earth is the only telluric planet in the solar system that has a strong magnetic field that protects us from the wrath of the sun. Here is this amazing experience on video.

The depths of the structure of the globe…” data-image=”https://cdn.futura-sciences.com/buildsv6/images/midioriginal/8/4/f/84ff7edce5_123534_earth-apollo8.jpg” data-url = ” https://news.google.com/planete/definitions/structure-earth-earth-4725/” data-more=”Read more”>Earth still hold many secrets. The difficulty of imaging the innermost layers of our planet means that many questions remain unanswered to this day, particularly about its composition, but also about what animates the Earth’s deep mantle. For some time, however, certain enigmatic structures have attracted the particular attention of scientists.

At the interface between the outer core and the cladding seismic waves indeed show the presence of large structures characterized by very low seismic velocities. These areas contrast with the rest of the deep mantle, which in turn is associated with high wave velocities that are tremendous Print that reigns in these depths. The hypotheses to explain this ULVZ (e.g Extremely low speed zones, areas with very low speeds) are running well. However, their study encounters the difficulty of obtaining high-quality data that allow for accurate characterization.

More accurate imaging of ULVZs

Thanks to the analysis of certain They occur when a starting impulse sets particles in motion, which in turn cause matter in contact with them to move before …” data-image=”https://cdn.futura-sciences. com /buildsv6/images/midioriginal/6/f/b/6fb435d98c_45125_sismometer-heroesbed-flickr.jpg” data-url=”https://news.google.com/planete/definitions/structure-terre-onde -seismic-13869 / ” data-more=”Read more”>seismic waves diffracted at the core-mantle interface, researchers from the Universities of Cambridge and Oxford have managed to obtain new ‘images’ of these structures, which lie some 2,800 kilometers below our feet. Images much more accurate than those obtained so far, allowing to emit new assumptions about their composition and operation.

The studied area is at the base of the Hawaiian mantle cloud, well below the island of the same name. This cloud is a column of hot mantle that rises from the base of the mantle to the surface, producing intense volcanism hotspot. However, it appears that this cloud has its origins at the level of an ULVZ, which comes in the form of a 1988 sci-fi film, The Blob, depicting the invasion of Earth by an alien creature with such a morphology (bigger and bigger ) describes sour).” data-url=”https://news.google.com/planete/definitions/zoologie-blob-5469/” data-more=”Read the definition”>blob about twenty kilometers high. Until now, this type of “small” structure (compared to Earth’s scale) was almost invisible because it was underground resolution Boundary of tomographic models that define the structure of the earth using seismic waves generated by large earthquakes.

The method Digital developed by the researchers in the article published in the journal nature communication enabled the analysis of a high-frequency seismic signal. A means of mapping, with an accuracy of the order of a kilometer, the low-velocity area with one direction and one intensity is represented by a vector, the velocity vector. Relative velocity is the velocity of one body relative to another or relative to a frame.” data-image=”https://cdn.futura-sciences.com/buildsv6/images/midioriginal/3/1/9/319daf63f4_77541_leibniz-dp . jpg” data-url=”https://news.google.com/sciences/definitions/physics-velocity-324/” data-more=”Read definition”>speed at the base of the Hawaiian Plume.

Iron-rich areas

Their results suggest that the internal architecture of these ULVZ is very complex, with certainly a heterogeneous composition. High-frequency signal analysis and numerical modeling
Numerical modeling consists of building a set of functions…” data-image=”https://cdn.futura-sciences.com/buildsv6/images/midioriginal/a/0/8/a0817e96b9_50037926_soleil-simulation-vibrations- sismology . jpg” data-url=”https://news.google.com/sciences/definitions/matiere-modelisation-11321/” data-more=”Read more”>modelling of the internal structure indicate in particular that the ULVZ would be enriched ironan element normally characteristic of the Earth’s core, which is divided into two layers
Liquid in nature, the outer core (density 10) is…” data-image=”https://cdn.futura-sciences.com/buildsv6/images/midioriginal/7/4/6/7466fb8049_50004180_terre-270907. jpg” data-url=”https://news.google.com/planet/definitions/structure-earth-earth-core-13836/” data-more=”Read more”>earth core underlying. The amount of iron would also be variable, since the base of the ULVZ would be richer in it than its top. This compositional anomaly, with the presence of a certain proportion of fluid Magma, would explain the nearly 40% reduction in seismic wave speeds compared to the rest of the deep mantle.

This iron accumulation could be explained by several hypotheses. It has already been suggested that ULVZs represent the remains of the ancient magma ocean, which preceded the formation of the continental crust, as the name suggests, forms the continents. It’s essentially a…” data-image=”https://cdn.futura-sciences.com/buildsv6/images/midioriginal/7/d/1/7d1ca441ac_44707_def-epaisseur-croute-terrestre-usgs.jpg” data-url=”https://news.google.com/planete/definitions/structure-terre-terrestrial-crust-2491/” data-more=”Read more”>crust at the very beginning of the earth’s history. In this case layering observed in the distribution of iron would be an index of the fractionation of iron during the various stages of crystallization of this “ocean” of molten rock.

Another hypothesis is that this composition is related to the meteorite impacts that Earth has experienced throughout its history. The iron it contains asteroids hitting Earth would have mixed with the silicates of the mantle and accumulated at the interface with the core.

A final hypothesis is that the iron comes directly from the outer core. While this would have the ability to dissolve certain copper (Cu) and the copper ion, for example…” data-image=”https://cdn.futura-sciences.com/buildsv6/images/midioriginal/7 /4/d /74d6f5bda2_92001_element-chimie.jpg” data-url=”https://news.google.com/sciences/definitions/chimie-element-chimie-15852/” data-more=”Read more”>chemical elements, this process is suspected to be particularly involved in the geodynamo effect that underlies the Earth’s magnetic field.

Leaving aside these hypotheses yet to be tested, it appears that these particularly hot zones contribute to significant variations in heat flux. Physicists classify heat as thermal energy. In the international system, it is therefore measured in joules (J). Heat more closely corresponds to a transfer…” data-image=”https://cdn.futura-sciences.com/buildsv6/images/midioriginal/7/3/5/735709801b_92578_chaleur.jpg” data-url=” https :/ /news.google.com/sciences/definitions/physics-heat-15898/” data-more=”Read more”>warmth recorded at the core-mantle interface. In this sense, ULVZ could play an important role in the convection of the mantle and thus involved in the formation of hotspots, but also of the geodynamo.

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