In contrast to the seismic and infrasonic energy released from quiescent and erupting volcanoes, which have long been known to manifest episodes of highly periodic behavior, the spectral properties ...of volcanic gas flux time series remain poorly constrained, due to a previous lack of high‐temporal resolution gas‐sensing techniques. Here we report on SO2 flux measurements, performed on Mount Etna with a novel UV imaging technique of unprecedented sampling frequency (0.5 Hz), which reveal, for the first time, a rapid periodic structure in degassing from this target. These gas flux modulations have considerable temporal variability in their characteristics and involve two period bands: 40–250 and 500–1200 s. A notable correlation between gas flux fluctuations in the latter band and contemporaneous seismic root‐mean‐square values suggests that this degassing behavior may be generated by periodic bursting of rising gas bubble trains at the magma‐air interface.
Key Points
Distinct periodic structure in volcanic degassingCorrelation between gas flux fluctuations and contemporaneous seismic RMS valuesPeriodic bursting of rising gas bubble trains at the magma‐air interface
Volcanoes with multiple summit vents present a methodological challenge for determining vent-specific gas emissions. Here, using a novel approach combining multiple ultraviolet cameras with ...synchronous aerial measurements, we calculate vent-specific gas compositions and fluxes for Stromboli volcano. Emissions from vent areas are spatially heterogeneous in composition and emission rate, with the central vent area dominating passive emissions, despite exhibiting the least explosive behaviour. Vents exhibiting Strombolian explosions emit low to negligible passive fluxes and are CO
-dominated, even during passive degassing. We propose a model for the conduit system based on contrasting rheological properties between vent areas. Our methodology has advantages for resolving contrasting outgassing dynamics given that measured bulk plume compositions are often intermediate between those of the distinct vent areas. We therefore emphasise the need for a vent-specific approach at multi-vent volcanoes and suggest that our approach could provide a transformative advance in volcano monitoring applications.
We report here on the first record of carbon dioxide gas emission rates from a volcano, captured at ≈1Hz. These data were acquired with a novel technique, based on the integration of UV camera ...observations (to measure SO2 emission rates) and field portable gas analyser readings of plume CO2/SO2 ratios. Our measurements were performedat the North East crater of Mount Etna, southern Italy, and the data reveal strong variability in CO2 emissions over timescales of tens to hundreds of seconds, spanning two orders of magnitude. This carries importantimplications for attempts to constrain global volcanic CO2 release to the atmosphere, and will lead to an increased insight into short term CO2 degassing trends. A common oscillation in CO2 and SO2 emission rates in addition to the CO2/SO2 ratios was observed at periods of ≈89s. Our results are furthermore suggestive of an intriguing temporal lag between oscillations in CO2 emissions and seismicity at periods of ≈300–400s, with peaks and troughs in the former series leading those in the latter by ≈150s. This work opens the way to the acquisition of further datasets with this methodology across a range of basaltic systems to better our understandingof deep magmatic processes and of degassing links to manifest geophysical signals.
•A new methodology has been developed to capture high time resolution carbon dioxide flux.•Volcanic carbon dioxide emissions vary rapidly at short timescales.•Emission of carbon dioxide and sulphur dioxide are linked by a common periodicity.•Our results demonstrate an intriguing link between gas flux and seismicity.
A microprocessor system is presented in which the supply voltage and clock frequency can be dynamically varied so that the system can deliver high throughput when required while significantly ...extending battery life during the low speed periods. The system consists of a dc-dc switching regulator, an ARM V4 microprocessor with a 16-kB cache, a bank of 64-kB SRAM ICs, and an I/O interface IC. The four custom chips were fabricated in a standard 0.6-/spl mu/m 3-metal CMOS process. The system can dynamically vary the supply voltage from 1.2 to 3.8 V in less than 70 /spl mu/s. This provides a throughput range of 6-85 MIPS with an energy consumption of 0.54-5.6 mW/MIP yielding an effective energy efficiency as high as 26200 MIPS/W.
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/SO2 ratio in the plume with coincident remote sensing measurements (ground‐ and satellite‐based) of SO2 emission rate to compute the first estimate of CO2 flux at Bagana. We report low SO2 and CO2 fluxes at Bagana from our fieldwork in September 2019, ∼320 ± 76 td−1 and ∼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.
Plain Language Summary
Bagana is a remote and highly active volcano in southeastern Papua New Guinea (PNG). Historically, it has been among the most active volcanoes in PNG, notable for its long‐lived eruptions and sustained gas emissions. Bagana has only been infrequently studied before now. We use unoccupied aerial systems (drones) along with ground‐ and satellite‐based remote sensing data to characterize the chemical composition and flux of Bagana's gas emissions and place these in the context of global volcanic emissions. Owing to low activity during the time of our fieldwork, we report lower than anticipated emissions of carbon dioxide and sulfur dioxide from Bagana. We argue that characterizing highly variable volcanic emissions is challenging without long‐term continuous observations and that, for remote volcanoes like Bagana, both drones and satellite observations are powerful tools to undertake these observations.
Key Points
We present the first measurements of volcanic gas composition at Bagana volcano
CO2 and SO2 fluxes at Bagana vary widely with levels of unrest, from ∼102 to ∼104 td−1
Unoccupied aerial systems (drones) are of great value in monitoring emissions from inaccessible volcanic summits
Instruments which are designed to measure multiple gases are widely used across several industries with a common focus on environmental gas sampling. Reliable instrumentation and gas sensors are ...therefore vital for the monitoring of air quality in cities and in more challenging scenarios, for example volcanic gas release. However, such instrumentation is commonly expensive and can be difficult to deploy, meaning that large instrument networks - needed to assess spatial air quality differences - is inhibitive. A bespoke do-it-yourself approach can therefore be beneficial. Here, we detail a new instrument, the PiGas, which is modelled on the successful “Multi-GAS” technique (Shinohara, 2005; Aiuppa et al. 2005) for the measurement of carbon dioxide (CO2), sulphur dioxide (SO2), hydrogen sulphide (H2S), and water vapour (H2O). Indeed, CO2 is a common gas of interest yet its measurement at high accuracy can be expensive. We demonstrate a cost reduction to <£500 by adapting parts used from non-air sampling specific industries and through use of a lower-cost and lower-power requirement CO2 sensor (the CozIR A-H). We demonstrate the versatility of the PiGas for monitoring indoor and outdoor air quality as a diffuse and pumped sensor. We also test the instrument in two extreme volcanic environments at the high altitude Alitar and Volcán Lastarria (Chile). Overall, the instrumentation shows potential for more widespread co-ordinated use to improve spatial sampling distributions in low concentration scenarios as a supplement to higher accuracy and higher precision instruments in volcanic environments.
•We present findings a new low-cost gas sampling instrument called the PiGas, based around the Raspberry Pi.•We demonstrate usage in air quality scenarios for carbon dioxide, sulphur dioxide, hydrogen sulphide, and water vapour.•We investigate the utility of a lower precision carbon dioxide sensor.•We test the PiGas in a hostile volcanic environment at Alitar and Lastarria, northern Chile.
Recent gas flux measurements have shown that Strombolian explosions are often followed by periods of elevated flux, or “gas codas,” with durations of order a minute. Here we present UV camera data ...from 200 events recorded at Stromboli volcano to constrain the nature of these codas for the first time, providing estimates for combined explosion plus coda SO2 masses of ≈18–225 kg. Numerical simulations of gas slug ascent show that substantial proportions of the initial gas mass can be distributed into a train of “daughter bubbles” released from the base of the slug, which we suggest, generate the codas, on bursting at the surface. This process could also cause transitioning of slugs into cap bubbles, significantly reducing explosivity. This study is the first attempt to combine high temporal resolution gas flux data with numerical simulations of conduit gas flow to investigate volcanic degassing dynamics.
Key Points
Stromboli gas flux data suggest that trains of daughter bubbles may follow gas slugs
CFD models suggest a complex relationship between daughter bubble production rate and Nf
Bubble production can result in significant mass loss from ascending slugs
Here we present a novel computational signal processing approach for comparing two signals of equal length and sampling rate, suitable for application across widely varying areas within the ...geosciences. By performing a continuous wavelet transform (CWT) followed by Spearman׳s rank correlation coefficient analysis, a graphical depiction of links between periodicities present in the two signals is generated via two or three dimensional images. In comparison with alternate approaches, e.g., wavelet coherence, this technique is simpler to implement and provides far clearer visual identification of the inter-series relationships. In particular, we report on a Matlab® code which executes this technique, and examples are given which demonstrate the programme application with artificially generated signals of known periodicity characteristics as well as with acquired geochemical and meteorological datasets.
•We present a method for comparing periodicity in two signals using wavelets.•Matlab code is provided to execute the method.•Examples are provided using artificial, geochemical and meteorological data.
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