Variations in CO2 emissions at a mud volcano at the southern base of Mt Etna: are they due to volcanic activity interference or a geyser-like mechanism?

Abstract

Mud volcanoes are often associated with large areas of CO 2 and CH 4 emission that are potentially dangerous due to sudden paroxysmal gas and mud eruptions. Despite the interest in understanding such natural environments, they have not yet been thoroughly investigated and a single interpretative framework remains to be elaborated. This lack of knowledge may be due to the difficulty in measuring in-plume CO 2 as there is very little contrast with atmospheric CO 2 , coupled with the complex organizational strategies required for long-term monitoring. This work features three different methods that were used to evaluate the CO 2 flux at the Salinelle mud volcano in the foothills of Mt Etna (Italy), carried out periodically from December 2013 to April 2018. We computed in-plume CO 2 flux indirectly using a tunable laser and a portable MultiGAS and, directly, measuring the gas volumetric flux from bubbling pools. The morphological variations of the mud field were recorded using unmanned aerial vehicle (UAV) imagery, which provided information on the migration of vents in relation to the observed variations in measured gas output. Our analysis shows that the three methods gave comparable values, indicating the feasibility of this approach. Our findings suggest a pseudo-cyclical pattern in the bulk CO 2 emitted at Salinelle, introducing a new interpretation of the processes involved in mud volcano dynamics. We theorize that the periodic variation of the gas emitted at the Salinelle may be attributed to a Bgeyser-like^mechanism that may be subject to interruption or changes in magnitude by volcanic or seismic events.

Imaging the Salinelle Mud Volcanoes (Sicily, Italy) using integrated geophysical and geochemical surveys

“…This area, laying on the volcanic formations, is more or less north west-south east elongated and is bounded to the north by clays and to the south by the Conetto dei Cappuccini. The main vents show only minor displacements over a very small surface (a few hundred meters, Figure 1) and fairly small changes in their shape [Federico et al, 2019], and they are characterized by a constant emission of gas and muddy water, though with variable intensity. Conversely, minor vents, especially outside of the main central eruptive area, are normally ephemeral and very unstable and they undergo marked changes over short time periods due to strong variations in the erupted gas flow.…”

“…The proximity of the survey to inhabited or cultivated areas prevented the extension of the survey to the south-east and north-west areas, so we could not have a regularly spaced grid of measurement points. Anyway, the profiles were chosen so as to intersect the area affected by the main emission vents, whose location can be considered fairly stable over time [Federico et al, 2019]. The method used was that of the accumulation chamber [Parkinson, 1981;Tonani and Miele, 1991;Chiodini et al, 1998].…”

UAV survey method to monitor and analyze geological hazards: the case study of the mud volcano of Villaggio Santa Barbara, Caltanissetta (Sicily)

“…The risk is proportional to the magnitude of the hazards and the vulnerability of the affected population. Among the deformation monitoring systems, the photogrammetry technique from unmanned aerial vehicles (UAVs) is becoming more widely used thanks to the high efficiency in data acquisition, the low cost compared to traditional techniques and the acquisition of high-resolution images (Harwin and Lucieer, 2012;James and Robson, 2012;Westoby et al, 2012;Fonstad et al, 2013;Javernick et al, 2014;Johnson et al, 2014;James et al, 2017aJames et al, , b, 2020. This technique is important for studying catastrophic natural events such as floods, earthquakes, landslides, etc.…”