Passive vs. active degassing modes at an open-vent volcano (Stromboli, Italy)

We report here on a UV-camera based field experiment performed on Stromboli volcano during 7 days in 2010 and 2011, aimed at obtaining the very first simultaneous assessment of all the different forms (passive and active) of SO2 release from an open-vent volcano. Using the unprecedented spatial and temporal resolution of the UV camera, we obtained a 0.8 Hz record of the total SO2 flux from Stromboli over a timeframe of 14 h, which ranged between 0.4 and 1.9 kg s 1 around a mean value of 0.7 kg s 1 and we concurrently derived SO2 masses for more than 130 Strombolian explosions and 50 gas puffs. From this, we show erupted SO2 masses have a variability of up to one order of magnitude, and range between 2 and 55 kg (average 20 kg), corresponding to a time integrated flux of 0.0570.01 kg s 1. Our experimental constraints on individual gas puff mass (0.03–0.42 kg of SO2, averaging 0.19 kg) are the first of their kind, equating to an emission rate ranging from 0.02 to 0.27 kg s 1. On this basis, we conclude that puffing is two times more efficient than Strombolian explosions in the magmatic degassing process, and that active degassing (explosionsþpuffing) accounts for 23% (ranging from 10% to 45%) of the volcano’s total SO2 flux, e.g., passive degassing between the explosions contributes the majority ( 77%) of the released gas. We furthermore integrate our UV camera gas data for the explosions and puffs, with independent geophysical data (infrared radiometer data and very long period seismicity), to offer key and novel insights into the degassing dynamics within the shallow conduit systems of this open-vent volcano

Unmanned aerial vehicle measurements of volcanic carbon dioxide fluxes

We report the first measurements of volcanic gases with an unmanned aerial vehicle (UAV). The data were collected at La Fossa crater, Vulcano, Italy, during April 2007, with a helicopter UAV of 3 kg payload, carrying an ultraviolet spectrometer for remotely sensing the SO2 flux (8.5 Mg d−1), and an infrared spectrometer, and electrochemical sensor assembly for measuring the plume CO2/SO2 ratio; by multiplying these data we compute a CO2 flux of 170 Mg d−1. Given the deeper exsolution of carbon dioxide from magma, and its lower solubility in hydrothermal systems, relative to SO2, the ability to remotely measure CO2 fluxes is significant, with promise to provide more profound geochemical insights, and earlier eruption forecasts, than possible with SO2 fluxes alone: the most ubiquitous current source of remotely sensed volcanic gas data

Protocols for UV camera volcanic SO2 measurements

Ultraviolet camera technology offers considerable promise for enabling 1 Hz timescale acquisitions of volcanic degassing phenomena, providing two orders of magnitude improvements on sampling frequencies from conventionally applied scanning spectrometer systems. This could, for instance enable unprecedented insights into rapid processes, such as strombolian explosions, and non-aliased corroboration with volcano geophysical data. The uptake of this technology has involved disparate methodological approaches, hitherto. As a means of expediting the further proliferation of such systems, we here study these diverse protocols, with the aim of suggesting those we consider optimal. In particular we cover: choice and set up of hardware, calibration for vignetting and for absolute concentrations using quartz SO2 cells, the retrieval algorithm and whether one or two filters, or indeed cameras, are necessary. This work also involves direct intercomparisons with narrowband observations obtained with a scanning spectrometer system, employing a differential optical absorption spectroscopic evaluation routine, as a means of methodological validation

Semantic segmentation of explosive volcanic plumes through deep learning

Tracking explosive volcanic phenomena can provide important information for hazard monitoring and volcano research. Perhaps the simplest forms of monitoring instruments are visible-wavelength cameras, which are routinely deployed on volcanoes around the globe. Here, we present the development of deep learning models, based on convolutional neural networks (CNNs), to perform semantic segmentation of explosive volcanic plumes on visible imagery, therefore classifying each pixel of an image as either explosive plume or not explosive plume. We have developed 3 models, each with average validation accuracies of >97% under 10-fold cross-validation; although we do highlight that, due to the limited training and validation dataset, this value is likely an overestimate of real-world performance. We then present model deployment for automated retrieval of plume height, rise speed and propagation direction, all parameters which can have great utility particularly in ash dispersion modelling and associated aviation hazard identification. The 3 trained models are freely available for download at https://doi.org/10.15131/shef.data.17061509

Ultraviolet camera measurements of passive and explosive (Strombolian) sulphur dioxide emissions at Yasur Volcano, Vanuatu

Here, we present the first ultraviolet (UV) camera measurements of sulphur dioxide (SO2) flux from Yasur volcano, Vanuatu, for the period 6–9 July 2018. These data yield the first direct gas-measurement-derived calculations of explosion gas masses at Yasur. Yasur typically exhibits persistent passive gas release interspersed with frequent Strombolian explosions. We used compact forms of the “PiCam” Raspberry Pi UV camera system powered through solar panels to collect images. Our daily median SO2 fluxes ranged from 4 to 5.1 kg s−1, with a measurement uncertainty of −12.2% to +14.7%, including errors from the gas cell calibration drift, uncertainties in plume direction and distance, and errors from the plume velocity. This work highlights the use of particle image velocimetry (PIV) for plume velocity determination, which was preferred over the typically used cross-correlation and optical flow methods because of the ability to function over a variety of plume conditions. We calculated SO2 masses for Strombolian explosions ranging 8–81 kg (mean of 32 kg), which to our knowledge is the first budget of explosive gas masses from this target. Through the use of a simple statistical measure using the moving minimum, we estimated that passive degassing is the dominant mode of gas emission at Yasur, supplying an average of ~69% of the total gas released. Our work further highlights the utility of UV camera measurements in volcanology, and particularly the benefit of the multiple camera approach in error characterisation. This work also adds to our inventory of gas-based data, which can be used to characterise the spectrum of Strombolian activity across the globe.</jats:p

Temporal Variability in Gas Emissions at Bagana Volcano Revealed by Aerial, Ground, and Satellite Observations

Abstract Bagana is a remote, highly active volcano, located on Bougainville Island in southeastern Papua New Guinea. The volcano has exhibited sustained and prodigious sulfur dioxide gas emissions in recent decades, accompanied by frequent episodes of lava extrusion. The remote location of Bagana and its persistent activity have made it a valuable case study for satellite observations of active volcanism. This remoteness has also left many features of Bagana relatively unexplored. Here, we present the first measurements of volcanic gas composition, achieved by unoccupied aerial system (UAS) flights through the volcano's summit plume, and a payload comprising a miniaturized MultiGAS. We combine our measurements of the molar CO2/SO2ratio in the plume with coincident remote sensing measurements (ground‐ and satellite‐based) of SO2emission rate to compute the first estimate of CO2flux at Bagana. We report low SO2and CO2fluxes at Bagana from our fieldwork in September 2019, ∼320 ± 76 td−1and ∼320 ± 84 td−1, respectively, which we attribute to the volcano's low level of activity at the time of our visit. We use satellite observations to demonstrate that Bagana's activity and emissions behavior are highly variable and advance the argument that such variability is likely an inherent feature of many volcanoes worldwide and yet is inadequately captured by our extant volcanic gas inventories, which are often biased to sporadic measurements. We argue that there is great value in the use of UAS combined with MultiGAS‐type instruments for remote monitoring of gas emissions from other inaccessible volcanoes

Non-stationary nature of SO2 degassing at Etna’s North-east crater (Italy).

Investigating Etna’s long-term SO2 flux behaviour has led to important conclusions on the structure of the volcano’s magma feeding system, magma production (and degassing) rates, and causes for the excess degassing behaviour. Nonetheless, our knowledge of the short-term (timescales of seconds to a few hours) behaviour of magmatic volatiles (e.g., bubble coalescence, separate ascent and surface bursting of gas-rich bubbles) in the volcano’s upper feeding conduit system is still fragmentary, and based on indirect evidences (petrologic-textural data, observation of geophysical signals , physical modelling and laboratory experiments). In the past, direct gas flux measurements at Etna have been taken with insufficient temporal resolution for fast conduit processes to be investigated. UV cameras now allow imaging of gas flux emissions, and exploration of underlying volcanic degassing processes, with an improved temporal resolution. In this work we show that UV cameras can valuably assist in capturing the rapid (timescale of seconds) SO2 flux variations occurring during the quiescent activity of a basaltic volcano. We have, in particular, investigated the non-stationary nature of degassing activity at Etna’s North-east crater, which is shown here to exhibit a somewhat periodic degassing behaviour (characteristic periods ranging 40-250 s). A similar degassing behaviour has recently been observed at other volcanoes (Stromboli, Erebus, San Cristobal, Gorely), and probably represents a common feature of all basaltic volcanoes. We finally present a preliminary model, which results suggest that the periodic degassing pattern may reflect inhomogeneous distribution of gas bubbles in a magmatic conduit, and their clustering to form trains of variably spaced gas bubble layers

Aerosol chemistry of emissions from three contrasting volcanoes in Italy

Volcanoes constitute an important source of aerosol. Here we report the size-resolved compositions of major water-soluble ions in particles collected in near-source emissions from three contrasting volcanoes (Solfatara, Vulcano and Stromboli, in Italy). Concentrations of soluble SO 42-, Cl -, F -, NO 3-, H +, K +, Na +, NH 4+, Ca 2+ and Mg 2+ were determined in 11 particle size bins from 0.069 to >25.5 μm in diameter. Soluble ions were most concentrated in the emissions from Solfatara and Stromboli. At Solfatara the major ions were NH 4+ and Cl -, tightly correlated in ∼0.8-1.5 μm diameter particles, strongly suggesting speciation as NH 4Cl. At Stromboli enhanced levels of SO 42-, H +, Na +, K + and NH 4+ were present in ∼0.5-1.5 μm diameter particles. Near-source soluble sulphate was observed in the plumes from Stromboli and Vulcano, with that from Stromboli in much higher concentration (0.94-2.14 compared with 0.07-0.13 μmol m -3). Comparing SO 42- measurements from Vulcano to those from other volcanic systems suggests that near-source sulphate aerosol emissions scale with SO 2 and contribute ∼0.03-0.05 Tg yr -1 of sulphur to the atmosphere. Simple calculations suggest that all the particles containing these soluble ions will act as cloud condensation nuclei at typical atmospheric supersaturations. © 2004 Elsevier Ltd. All rights reserved