At our feet are game processes essential to the dynamics of the earth. However, this dynamic is closely linked to the texture and composition of the coat, which is far from identical, this new study shows.
Two big speed contrasts in the deep coat
The It allows us to cross the globe and capture these inner zones more and more accurately . In particular, it made it possible to highlight two large structures at the base of the lower mantle. These massive structures, one of which is located under Africa and the other under the Pacific Ocean, are similar to the lowlands. From Cutting (LLSVP) Large low-cut-speed province) These two structures are thus identified Compared to other low coats, its speed is considerably higher due to its enormity Prevail at this depth. This velocity variation indicates that the two LLSVPs have large differences with the other mantle. However, we do not know what these differences are: composition, density, Temperature … The difficulty for scientists in understanding the origin and nature of these two major anomalies comes mainly because the properties of the entire undercoat are still very poorly controlled.Thanks
Why such strong asymmetry?
However, researchers are interestedThese two contradictions attempt to understand their dynamics and their evolution over time. The anomaly under Africa is particularly imposing: it rises 1,300 to 1,800 km above the core-mantle limit, while the anomaly under the Pacific reaches only 500 to 800 km. So the African anomaly is twice as large as the Pacific anomaly. What is this asymmetry related to? However, the two structures are surprisingly opposed, one on each side of the world.
Some studies suggest the spread of these abnormalities , And especially by sub-regions. In fact, The Layers Penetrating deep into the mantle (plowing plates) will disturb the heating system at the interface with the center and lead to cutting LLSVPs.
The anomaly under Africa is less dense than under the Pacific
In a new study, two researchers from the University of Arizona (USA) conducted , Show that the height of the contrasts is mainly controlled by the viscosity of the surrounding coat and the density of the material creating the irregularity. Their hypothesis is that the African anomaly has a different composition and a lower density than the anomaly, especially under the Pacific, thus explaining the difference in height between the two structures.To study the evolution of these paradoxes according to different parameters. Results, published
This distinction is supported by a recent study of composition . That No continent was found in the volcano above the Pacific anomaly. This distinction suggests that the two contradictions evolved differently over time, and that the exchanges with the surrounding mantle may have been different, combining elements of a continent that came to depth through African disorder and oppression.Of Located directly above the two LLSVPs, and it shows that lava flows from the sub-African mantle were concentrated in continental (not very dense) material previously subjected during the life cycle.
The vertical extension of the African anomaly brings it “relatively” closer to the surface, which explains the existence of super volcanoes on the African plate for hundreds of millions of years.