Understand the processes that occur inside quiescent volcanoes that show evidence of 'awakening', such as Campi Flegrei, in order to further intensify surveillance and scientific research activities in the sector. This is the aim of the study by a team of Italian and French researchers, coordinated by INGV. The research results were published in Nature Communications
Highlighted, for the first time, the existence of a pressure threshold during the process of ascent of magma in the crust, once reached which, a volcanic "unrest" could evolve towards a "critical" condition. This is demonstrated by the research Magmas near the critical degassing pressure drive volcanic unrest toward a critical state (http://www.nature.com/articles/ncomms13712), conducted by a group of researchers from theIstituto Nazionale di Geofisica e Vulcanologia (INGV) - Sections of Bologna, Naples, and Palermo, the Universities of Palermo and Roma Tre, and the University of Savoie. The results of the study were published in Nature Communications (Nature Publishing Group). "The aim of the study," explains Giovanni Chiodini, INGV research director and coordinator of the study, "is to understand the processes occurring within dormant volcanoes that, showing evidence of volcanic unrest, could evolve towards an eruption, as in the Campi Flegrei caldera (the term caldera refers to those volcanoes whose structure is dominated by subcircular depressions due to the subsidence of the ground following large eruptions)." The ascent of magma from deep underground is one of the causes of volcanic unrest. As it rises toward the surface, magma loses pressure and releases some of the volatile or gaseous species dissolved in the melt. Hence the idea of characterizing the release mechanisms of the main magmatic volatile species, water and carbon dioxide, during the depressurization process. "Specifically, the work demonstrates for the first time the existence of a critical pressure value around which, for each type of magma, the total amount of fluids released increases significantly (by more than an order of magnitude). Once these critical conditions are reached, the magma releases significant quantities of water, in a high-temperature vapor state, which is injected into the rocks between the magma and the surface. Heated by the large amounts of vapor, the rocks weaken, losing their mechanical strength, causing the unrest to accelerate toward critical conditions. Conversely, the loss of water makes the magma more viscous and slows its ascent, even to the point of stopping it. The subsequent evolution of the process is governed by the prevalence of the weakening of the cap, which favors the evolution toward an eruption of the volcano, or, conversely, by the increase in the magma's viscosity, which can lead to the exhaustion of the unrest," Chiodini continues. The Campi Flegrei, an active volcano in the Naples area, has been in a state of unrest for decades, and the bradyseisms that have recurred in the area since the 50s are the most evident evidence of this. Since 2005, the Campi Flegrei have been rising again, which led to a change in activity status in 2012, from green ('quiet') to yellow ('scientific attention'). During this period, signs of magma depressurization and, more recently, heating have been detected. "The possible approach of the magma to 'critical pressure' conditions," says Chiodini, "may explain the current acceleration of deformation, the recent increase in the number of earthquakes, and the increase in gaseous species most sensitive to temperature increases in the fumaroles of the Solfatara di Pozzuoli, one of the most active areas of the Phlegraean caldera."
"Given the complexity of the ongoing volcanic processes", concludes the researcher, "only a careful analysis and interpretation of the future variations of the physical and chemical signals monitored on the volcano and a further intensification of research activities, to be achieved through new projects dedicated to Campi Flegrei, could allow to establish the possible future evolution of the volcanic unrest”.
Abstract
During the reawakening of a volcano, magma migrating through the shallow crust have to pass through hydrothermal fluids and rocks. The resulting magma–hydrothermal interactions are still poorly understood, which impairs the ability to interpret volcano monitoring signals and perform hazard assessments. Here we use the results of physical and volatile saturation models to demonstrate that magmatic volatiles released by decompressing magma at a critical degassing pressure (CDP) can drive volcanic unrest toward the critical state. We show that, at the CDP, the abrupt and voluminous release of H2O-rich magmatic gases can heat hydrothermal fluids and rocks, triggering an accelerating deformation that can ultimately culminate in rock failure and eruption. We proposed that magmas could be approaching the CDP at Campi Flegrei, a volcano in the metropolitan area of Naples, one of the most densely inhabited areas in the world, and where accelerating deformation and heating are currently being observed.
The fumarolic field of Solfatara, the most active area in the volcanic complex of Campi Flegrei. On the right the city of Pozzuoli and in the background the islands of Procida and Ischia
VIDEO
Simulation of the Campi Flegrei eruption (by INGV)