Scientists delve deeper into the secret of supereruptions

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Comment fonctionnent les super-éruptions ? © Wead, Adobe Stock

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[EN VIDÉO] 8 things you need to know about volcanoes Objects of fascination and terror, volcanoes are among nature’s most irreducibly indomitable forces. From the mythological origin of their name to the eruptions that have marked history, here are 8 things you need to know about them. Volcanic eruptions are frequent on Earth and represent one of the main manifestations of the intense geological activity of our Planet. Currently, there are more than 1,000 active volcanoes in the world, and between 50 and 70 erupt each year. The intensity, type or duration of each eruption is extremely variable and depends mainly on the tectonic context, therefore, during its history, the Earth has experienced an incalculable number of volcanic eruptions, some of which are particularly significant. Supereruptions are characterized by their violence, an extremely long activity of the volcanic system (of the order of several tens of millions of years) and by the enormous volume of magma involved, but the generation of this type of volcanism as as the Associated mechanisms are still poorly understood Magma on the surface but also in depth If super-eruptions are characterized on the surface by enormous volumes of volcanic deposits, they are also associated with the establishment of large plutons. Plutons result from the crystallization of magma deep in the Earth’s crust. Therefore, plutonic (or intrusive) rocks differ from volcanic (or effusive) rocks, which crystallize at the surface. Plutonic and volcanic rocks can have the same mineralogical composition since they come from the same magma, but they differ in their appearance and in particular in the size of the crystals, which vary according to the time the magma takes to cool. If the study of volcanic rocks allows us to understand the evolution of the magmatic system over time, the analysis of plutonic rocks allows us to better understand the formation of the magmatic chamber and the global dynamics of the system responsible for the eruption. depth, the formation of a pluton will depend on many parameters: fractional crystallization, differentiation of magmatic liquid, injection of new magma… Based on the study of certain volcanic rocks in northern Chile associated with a series of four supereruptions, Thus, a team of scientists was able to trace the beginning of this type of eruption in order to better understand the associated magmatic dynamics, they show that if the placement of plutons within the crust is staged during several million years, testifying to a continuous supply of magma over very long periods of time, the final ascent of magma in the shallow magma chambers and the initiation of an eruption occurs very quickly, within a few decades, the very short time it takes to fill the magma chambers in the upper crust just before an eruption. In fact, the study shows that certain crystals remain at temperatures of about 470 °C (that is, the temperature that allows the maintenance of liquid magma) for very long periods before being incorporated into the effusive magma. Therefore, magma would be stored long-term in a hot zone of the middle crust, before being ejected episodically and rapidly to give rise to supereruptions. Within this magmatic “incubator”, certain minerals will begin to crystallize to form and grow plutons. The researchers think that the magma at the origin of the eruptions would come from an unstable pocket located at the top of this incubator. These data provide a better understanding of the generation of supereruptions and could help identify volcanoes likely to produce such eruptions, but supereruptions remain rare. Although they only occur every 20,000 years on average, they are still extremely destructive phenomena, capable of significantly influencing the climate and the environment.Are you interested in what you just read?
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