Abstract We report on a systematic record of SO 2 flux emissions from individual vents of Etna volcano (Sicily), which we obtained using a permanent UV camera network. Observations were carried out in summer 2014, a period encompassing two eruptive episodes of the New South East Crater (NSEC) and a fissure‐fed eruption in the upper Valle del Bove. We demonstrate that our vent‐resolved SO 2 flux time series allow capturing shifts in activity from one vent to another and contribute to our understanding of Etna's shallow plumbing system structure. We find that the fissure eruption contributed ~50,000 t of SO 2 or ~30% of the SO 2 emitted by the volcano during the 5 July to 10 August eruptive interval. Activity from this eruptive vent gradually vanished on 10 August, marking a switch of degassing toward the NSEC. Onset of degassing at the NSEC was a precursory to explosive paroxysmal activity on 11–15 August.
Improving volcanic gas monitoring techniques is central to better understanding open-vent, persistently degassing volcanoes. SO 2 cameras are increasingly used in volcanic gas studies, but observations are commonly limited to one single camera alone viewing the volcanic plume from a specific viewing direction. Here, we report on high frequency (0.5 Hz) systematic measurements of the SO 2 flux at Stromboli, covering a 1-year long observation period (June 2017-June 2018), obtained from two permanent SO 2 cameras using the same automated algorithm, but imaging the plume from two different viewing directions. Our aim is to experimentally validate the robustness of automatic SO 2 camera for volcano monitoring and to demonstrate the advantage of using two co-exposed SO 2 camera stations to better capturing degassing dynamics at open-vent volcanoes. The SO 2 flux time-series derived from the two SO 2 camera stations exhibit good match, demonstrating the robustness of the automatic SO 2 camera method. Our high-temporal resolution SO 2 records resolve individual Strombolian explosions as transient, repetitive gas bursts produced by the sudden release of over pressurized gas pockets and scoriae. Calculations show that explosive degassing activity accounts for ∼10% of the total SO 2 emission budget (dominated by passive degassing) during mild regular open-vent activity. We show that the temporal variations of the explosive SO 2 flux go in tandem with changes in total SO 2 flux and VLP seismicity, implicating some commonality in the source processes controlling passive degassing and explosive activity. We exploited the spatial resolution of SO 2 camera to discriminate degassing at two distinct regions of the crater area, and to minimize biases due by the station position respect to the target plume. We find that the SO 2 fluxes from southwest-central (SWCC) and northeast (NEC) crater areas oscillate coherently but those from the NEC are more sensitive to the changes in the volcanic intensity. We interpret this as due to preferential gas/magma channeling into the structurally weaker north-eastern portion of the crater terrace in response to increasing supply rate of buoyant, bubble-rich magma in the shallow plumbing system.
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 CO 2 /SO 2 ratio in the plume with coincident remote sensing measurements (ground‐ and satellite‐based) of SO 2 emission rate to compute the first estimate of CO 2 flux at Bagana. We report low SO 2 and CO 2 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.
Recent volcanic gas compilations have urged the need to expand in-situ plume measurements to poorly studied, remote volcanic regions. Despite being recognized as one of the main volcanic epicenters on the planet, the Vanuatu arc remains poorly characterized for its subaerial emissions and their chemical imprints. Here, we report on the first plume chemistry data for Mount Garet, on the island of Gaua, one of the few persistent volatile emitters along the Vanuatu arc. Data were collected with a multi-component gas analyzer system (multi-GAS) during a field campaign in December 2018. The average volcanic gas chemistry is characterized by mean molar CO2/SO2, H2O/SO2, H2S/SO2 and H2/SO2 ratios of 0.87, 47.2, 0.13 and 0.01, respectively. Molar proportions in the gas plume are estimated at 95.9 ± 11.6, 1.8 ± 0.5, 2.0 ± 0.01, 0.26 ± 0.02 and 0.06 ± 0.01, for H2O, CO2, SO2, H2S and H2. Using the satellite-based 10-year (2005–2015) averaged SO2 flux of ~434 t d−1 for Mt. Garet, we estimate a total volatile output of about 6482 t d−1 (CO2 ~259 t d−1; H2O ~5758 t d−1; H2S ~30 t d−1; H2 ~0.5 t d−1). This may be representative of a quiescent, yet persistent degassing period at Mt. Garet; whilst, as indicated by SO2 flux reports for the 2009–2010 unrest, emissions can be much higher during eruptive episodes. Our estimated emission rates and gas composition for Mount Garet provide insightful information on volcanic gas signatures in the northernmost part of the Vanuatu Arc Segment. The apparent CO2-poor signature of high-temperature plume degassing at Mount Garet raises questions on the nature of sediments being subducted in this region of the arc and the possible role of the slab as the source of subaerial CO2. In order to better address the dynamics of along-arc volatile recycling, more volcanic gas surveys are needed focusing on northern Vanuatu volcanoes.
The ordinarily benign activity of basaltic volcanoes is periodically interrupted by violent paroxysmal explosions ranging in size from Hawaiian to Plinian in the most extreme examples. These paroxysms often occur suddenly and with limited or no precursors, leaving their causal mechanisms still incompletely understood. Two such events took place in summer 2019 at Stromboli, a volcano otherwise known for its persistent mild open-vent activity, resulting in one fatality and damage to infrastructure. Here, we use a post hoc analysis and reinterpretation of volcanic gas compositions and fluxes acquired at Stromboli to show that the two paroxysms were preceded by detectable escalations in volcanic plume CO2 degassing weeks to months beforehand. Our results demonstrate that volcanic gas CO2 is a key driver of explosions and that the preparatory periods ahead of explosions in basaltic systems can be captured by precursory CO2 leakage from deeply stored mafic magma.
Abstract We present here the first volcanic gas compositional time‐series taken prior to a paroxysmal eruption of Villarrica volcano (Chile). Our gas plume observations were obtained using a fully autonomous Multi‐component Gas Analyser System (Multi‐GAS) in the 3 month‐long phase of escalating volcanic activity that culminated into the 3 March 2015 paroxysm, the largest since 1985. Our results demonstrate a temporal evolution of volcanic plume composition, from low CO 2 /SO 2 ratios (0.65‐2.7) during November 2014‐January 2015 to CO 2 /SO 2 ratios up to ≈ 9 then after. The H 2 O/CO 2 ratio simultaneously declined to <38 in the same temporal interval. We use results of volatile saturation models to demonstrate that this evolution toward CO 2 ‐enriched gas was likely caused by unusual supply of deeply sourced gas bubbles. We propose that separate ascent of over‐pressured gas bubbles, originating from at least 20‐35 MPa pressures, was the driver for activity escalation toward the 3 March climax.
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