Fidest – Agenzia giornalistica/press agency

Quotidiano di informazione – Anno 33 n° 338

Explosive eruptions: this is how magma breaks down

Posted by fidest press agency su giovedì, 1 aprile 2021

Although particularly fluid, the basaltic magma of volcanoes such as Etna and Stromboli shatters like a falling drinking glass. But, precisely because it is fluid, many of the fractures are healed, reducing the amount of ash erupted and its impact on those who live around volcanoes. This is the discovery of a team of researchers from the italian National Institute of Geophysics and Volcanology (INGV), the University of Munich (Germany) and the Mexican Universidad de Ciencias y Artes de Chiapas in Tuxtla, and Universidad Nacional Autónoma de México in Mexico City. The work Fracturing and healing of basaltic magmas during explosive volcanic eruptions has just been published in ‘Nature Geoscience’.”With this study”, explains Jacopo Taddeucci, researcher at INGV and first author of the study, “we wanted to understand the modalities of formation of volcanic particles, from volcanic bombs, which can reach the size of a car and which fall around the crater, to the microscopic volcanic ash which, on the other hand, is dispersed up to thousands of kilometers away. All of these particles form when the magma causing an eruption breaks up explosively.For basaltic magmas, such as those of Etna or Stromboli, this process is not well understood and there are conflicting theories among researchers “. In every type of explosion, from the small explosions of Stromboli that attract tourists, through the dangerous paroxysms of the same volcano, to the lava fountains that are characterizing the ongoing activity of Etna, basaltic magma shows specific behaviors.“By studying the samples of a large number of basaltic eruptions”, the researcher continues, “we discovered that in all the samples there are microscopic broken crystals. To understand the origin of these crystals, we carried out laboratory experiments where we melted Etna bombs and then blew up the molten rock by injecting gas under pressure. What we have found”, adds Taddeucci, “is that the crystals have been broken by the fragmentation of magma. The characteristics of these crystals tell us that the basaltic magma, apparently fluid, has actually fragmented in a fragile way, like a falling drinking glass. But even more interesting is the discovery that, since the magma is still molten upon fragmentation, many of the fractures that are formed at fragmentation’ later heal. This healing process of the fractures reduces the amount of ash erupted by the volcano”.“The results obtained”, continues the researcher, “help us to estimate how many particles will form in future eruptions and what size they will be, an essential point for dealing with the consequences of explosive eruptions. Furthermore, this new knowledge also guides us in the reverse path, that is to reconstruct the dynamics of past eruptions starting from the study of the particles they have left. There is no doubt that this discovery opens new horizons for the study of explosive volcanism “concludes Jacopo Taddeucci.

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