Using Drones and Miniaturized Instrumentation to Study Degassing at Turrialba and Masaya Volcanoes, Central America

Abstract

Gas measurements using unmanned aerial vehicles, or drones, were undertaken at Turrialba volcano, Costa Rica, and Masaya volcano, Nicaragua, in 2016 and 2017. These two volcanoes are the largest time‐integrated sources of gas in the Central American Volcanic Arc, and both systems are currently extremely active with potential for sudden destabilization. We employed a series of miniaturized drone‐mounted instrumentation including a mini‐DOAS, two MultiGAS instruments, and an optical particle counter, supplemented by ground‐based measurements. Payloads were typically 1–1.5 kg and flight times were 10–15 min. The measurements were both accurate and precise due to the inherent sensitivity of the instrumentation and the high gas concentrations, which the drones were able to sample. The quality of data obtained by our drones was comparable to that obtained by our ground‐based measurements. At Turrialba in April 2017, we measured an average SO2 flux of 1,380 ± 280 T/day, CO2/SO2 of 6.5, and H2O/SO2 of 27.8. Using these values, we calculated a CO2 flux of 6,170 T/day and an H2O flux of 10,790 T/day. At Masaya in May 2017, the average SO2 flux was 1,560 ± 180 T/day, with CO2/SO2 of 3.9 and H2O/SO2 of 62.3, giving a mean CO2 flux of 4,150 T/day and mean H2O flux of 27,330 T/day. The elevated carbon and water fluxes and ratios are indicative of underlying magmas that are enriched in these components, resulting in the high levels of activity observed.

Dynamics of Outgassing and Plume Transport Revealed by Proximal Unmanned Aerial System (UAS) Measurements at Volcán Villarrica, Chile

“…We find that variability in molar gas ratios is related to plume density, such that CO 2 /SO 2 ratios are both elevated and more variable in dilute plumes (<20 ppmv SO 2 , where SO 2 is taken as the “plume marker” due to the negligible content in ambient air). The effect of measurement uncertainty on CO 2 /SO 2 is amplified as the denominator approaches zero; however, we also acknowledge that diffuse CO 2 ‐rich degassing from the crater rim may contribute to more variable molar ratios at low SO 2 (Stix et al, ). In dense plume conditions (>20 ppmv SO 2 ), the CO 2 /SO 2 ratio converges and stabilizes at lower values approaching 1.69 ± 0.34 (Figure S8).…”

“…Recent developments in drone technology (in terms of both physical capability and user‐accessibility) have been matched by a drive toward increasingly lightweight and compact sensor payloads, such that the resulting Unmanned Aerial Systems (UAS) are rapidly becoming “go‐to” solutions for a wide range of volcanological applications. UAS are driving the greatest advances in those fields requiring either proximal measurements in extreme environments or large areal coverage, including lava flow mapping, constructing topographic models, and eruptive volume estimations (Darmawan et al, ; Favalli et al, ; Moussallam et al, ; Müller et al, ; Nakano et al, ; Turner et al, ), post‐eruption visual observation (Koyama et al, ), thermal imaging (Di Stefano et al, ), aeromagnetic surveys (Hashimoto et al, ; Kaneko et al, ), DOAS traverses for SO 2 flux determination, and volcanic gas measurements and sampling (Diaz et al, ; Di Stefano et al, ; McGonigle et al, ; Mori et al, ; Pieri et al, ; Rüdiger et al, ; Shinohara, ; Stix et al, ).…”

“…At Turrialba volcano, Costa Rica, SO 2 concentrations measured by UAS in the dilute distal plume (up to 3 km from the vent, measuring 0.3–20 ppm SO 2 ) were used to derive estimates of SO 2 emission rates using an inverse Bayesian modeling approach incorporating meteorological wind fields (Xi et al, ). A recent comparison of SO 2 fluxes obtained by traditional ground‐based DOAS traverses to those from drone‐mounted DOAS (DROAS) demonstrated the utility of UAS for this application, with the additional ability to constrain wind speeds at plume altitude based on passive drift speed of the UAS (Stix et al, ). Furthermore, comparison of CO 2 /SO 2 molar ratios obtained by ground‐based multi‐GAS and simultaneously by a UAS‐based gas sensor unit at Masaya, Nicaragua (Rüdiger et al, ; Stix et al, ), showed that downwind measurements using UAS in dilute plumes yield robust correlations between gas species that are comparable to those derived from proximal ground‐based measurements.…”

“…A recent comparison of SO 2 fluxes obtained by traditional ground‐based DOAS traverses to those from drone‐mounted DOAS (DROAS) demonstrated the utility of UAS for this application, with the additional ability to constrain wind speeds at plume altitude based on passive drift speed of the UAS (Stix et al, ). Furthermore, comparison of CO 2 /SO 2 molar ratios obtained by ground‐based multi‐GAS and simultaneously by a UAS‐based gas sensor unit at Masaya, Nicaragua (Rüdiger et al, ; Stix et al, ), showed that downwind measurements using UAS in dilute plumes yield robust correlations between gas species that are comparable to those derived from proximal ground‐based measurements. However, molar ratios in distal plumes (<5 ppm maximum SO 2 ) can be characterized by larger standard deviations than proximal crater rim measurements (<38 ppm SO 2 ; Rüdiger et al, ), highlighting that, although feasible, challenges still remain in acquiring high quality data from dilute plumes.…”

Remote sensing and identification of volcanic plumes using fixed‐wing UAVs over Volcán de Fuego, Guatemala

“…Jordan () presents a short summary of UAVs in geology, focusing on small multirotors, such as DJI Phantoms (DJI, Shenzhen, China) and the challenges surrounding their use in scientific fieldwork. Whereas Fuego's activity involves large ballistics, active volcanoes, such as Turrialba and Masaya in Central America, are safer to be close to, hence TakeOff/Land Points (TOLPs) can be found relatively close to the craters (Stix et al, ). As Stix et al show, with minimal altitude gain and short ranges required, multirotors are ideal platforms for sensor placement in static locations for gas measurements.…”