Two large super blooms in the Earth’s mantle confuse scientists with astonishing properties

propriétés superpanaches manteau terrestre

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The Earth’s mantle contains two large superplums, the “Large Low Cut-Speed ​​Provinces” (or LLSVP). Large low-cut-speed province), Discovered during seismic tomography studies. One is under Africa and the other is under the Pacific Ocean. Researchers have recently compared the morphology of these two rocks: their analysis reveals that the two contradictions have different compounds, dynamics, and evolutions.

A super bloom is a dense mass of rock that is characterized by the propagation of shear waves (or S waves) at low speeds. This revealed the presence of two large dense “bubbles” in the deeper layers of the mantle; These structures stretch for thousands of kilometers and can reach a thickness of 1000 km from the core-mantle interface. They are generally considered to be thermochemical layers, which directly affect the mantle and core processes. However, some of their characteristics, including their height difference and stability, have not been clarified.

Global Shear Wave tomography actually shows that the African anomaly is 1000 km higher than the Pacific anomaly. So the researchers tried to determine the origin of this difference. Through continuous simulations, they discovered that the maximum height at which a thermochemical pile can be reached is controlled by its density and the viscosity of the surrounding coat. This suggests that the African Super Bloom is less dense than its echoes on the other side of the Earth.

Low standard sub-African system

To conduct their research, Qian Yuan and Mingming Li of the School of Earth and Space Exploration at Arizona State University designed and operated hundreds of thermodynamic model simulations of the line. They tested various factors that could affect the height of LLSVPs, including differences in their size and density and viscosity between these super blooms and their direct environment. ” Our calculations revealed that the initial size of the bubbles did not affect their height Said Qian Yuan In a press release.

According to their analysis, the enormous difference in elevation between the two structures can only be explained by one reason: the LLSVP located under the African continent is much denser than it is under the Pacific Ocean – indicating that it may be less stable. The latter. By extension, the two evolved differently and today have different chemical compounds.

Two experts believe that the African Super Bloom may have been elevated in recent geological times, which explains the elevation of the surface landscape and the intense volcanoes found in East Africa. Note that the East African rift, which stretches from Eritrea to Mozambique, is actually well known for its volcanic activity – with more than 180 active volcanoes on the continent to date, including 77 in Ethiopia, 31 in Kenya and 23 in Tanzania. According to Volcano Discovery. Nyaragongo and its neighbor Nimuragra, located in the eastern part of the Democratic Republic of Congo, are the most active (and most threatening): they cause about one in five explosions.

Remnants of Thea’s gown?

Yuan and Li’s study challenges our understanding of deep mantle processes and, most importantly, how they can affect the Earth’s surface. For example, the instability of the Super Bloom beneath the African continent may be linked to continental changes in terrain, gravity, surface volcanism, and plate motion.

These results shed light on the evolution of the structure of the deep mantle, as well as the nature of mantle convection. ” The combination of analyzes of seismic results and geodynamic modeling provides new insights into the nature of the Earth’s largest structures in the deep interior and their relationship with the surrounding crust. Juan summarizes.

If both experts succeed in better classifying these internal contradictions, their origin should be further clarified. Several hypotheses have been suggested to illustrate the formation of these giant structures; Some believe that they may be the result of the crystallization of Adi Magma in the depths of the ocean. In A study published last year, Qian Yuan and his collaborators have argued that it may be the remains of the source planet Thea, which collided with Earth 4.5 billion years ago. If an object ejected during the impact accumulates and forms the moon, fragments of this planet may be buried deep in the Earth’s crust.

From Evidence from Iceland and Samoa Suggest that LLSVPs have been around since the time of the Moon’s impact, and the hypothesis is valid. According to recent work, Thea may have been larger, but may be 2-3% denser than Earth; Conflict simulations performed by Yuan show that under these conditions, Thea’s core will soon merge with Earth and its dense mantle will eventually accumulate near the center. However, more research is needed to confirm this situation.

Source: K. Yuan and M.L., Nature Geoscience

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