The interaction between magmas of different temperatures is believed to be behind the violent explosive eruptions of the Stromboli volcano: this is what a study conducted in collaboration with INGV just published in the journal Lithos affirms. The work represents a new step forward in knowledge of the functioning of volcanoes
Studying the magmatic minerals erupted from the Stromboli volcano, such as pyroxene, to understand how magma moves from the depths of the earth's crust and what processes occur during its ascent. This is the goal of the work Mush cannibalism and disruption recorded by clinopyroxene phenocrysts at Stromboli volcano: new insights from recent 2003-2017 activity just published in the journal Lithos and conducted by the researchers of the Laboratory for High Pressures and High Temperatures of Experimental Geophysics and Volcanology (HPHT) of the National Institute of Geophysics and Volcanology (INGV) in collaboration with the La Sapienza University of Rome, the University of Queensland (Australia) and with the Natural History Museum of London.
“Pyroxene” explains Piergiorgio Scarlato, volcanologist and head of the INGV HPHT Laboratory, “is a magmatic mineral which has the peculiarity of recording the processes that take place inside the crust and below the volcanic edifices, thus allowing us to reconstruct what occurs when magmas with different chemical compositions interact with each other and with what time scales these processes take place".
The study concerned, in particular, the products of the eruptions of Stromboli in the period from 2003 to 2017 and has important repercussions on the understanding of the mechanisms that produced the explosions of the summer of 2019.
“The analyzes on the minerals”, continues Scarlato, “show that Stromboli's magmatism is fed by a very hot magma which is found at a maximum depth of ten kilometres. This magma rises within the crust and then comes into contact with a cooler magma that is less than three kilometers deep. The interaction between these two magmas is one of the main causes that produce the violent explosive eruptions of Stromboli. Furthermore”, adds the researcher, “the pyroxenes found in the products of the explosion that took place on April 5, 2003 show that this interaction process was much faster than in the subsequent eruptions which occurred until 2017; this means that the geometry and shape of the magma chamber under the volcano started to change over time, in accordance with the fact that the pyroxenes recorded a much less evident interaction process between the two magmas".
The researchers also found that the eruptions from 2003 to 2017 are linked to a much hotter surface magma system than in the past.
“This further discovery”, explains the volcanologist, “is probably related to the explosions that occurred last summer on Stromboli. For this reason, our team is now studying the volcanic products erupted in the last year, in order to understand whether Stromboli's power system has further changed”, concludes Piergiorgio Scarlato.
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Pyroxene crystals from Stromboli seen under a microscope.
Chemical map of a pyroxene from Stromboli. The band of different composition within the crystal indicates the arrival of new magma before the April 5, 2003 explosive eruption.
Images of Stromboli in eruption (photo T. Ricci)
Images of Stromboli in eruption (photo T. Ricci)
Images of Stromboli in eruption (photo T. Ricci)