Search results for "LCA"

Along-arc, inter-arc and arc-to-arc variations in volcanic gas CO 2 /S T ratios reveal dual source of carbon in arc volcanism

2017

Abstract Some 300–600 Tg of volatiles are globally vented each year by arc volcanism. Such arc gas emissions have contributed to past and present-day evolution of the Earth atmosphere and climate by recycling mineral-bound volatiles subducted along active slabs. Carbon dioxide (CO 2 ) and total sulphur (S T ) are, after water, the major components of volcanic arc gases. Understanding their relative abundances (e.g., the CO 2 /S T ratio) in arc volcanic gases is important to constrain origin and recycling efficiency of these volatiles along the subduction factory, and to better constrain the global arc volcanic CO 2 flux. Here, we review currently available information on global variations o…

Escalating CO2 degassing at the Pisciarelli fumarolic system, and implications for the ongoing Campi Flegrei unrest

2019

Abstract This short communication aims at providing an updated report on degassing activity and ground deformation variations observed during the ongoing (2012–2019) Campi Flegrei caldera unrest, with a particular focus on Pisciarelli, currently its most active fumarolic field. We show that the CO2 flux from the main Pisciarelli fumarolic vent (referred as “Soffione”) has increased by a factor > 3 since 2012, reaching in 2018–2019 levels (>600 tons/day) that are comparable to those typical of a medium-sized erupting arc volcano. A substantial widening of the degassing vents and bubbling pools, and a further increase in CO2 concentrations in ambient air (up to 6000 ppm), have also been detec…

Terminal Strombolian activity at Etna’s central craters during summer 2012: The most CO<sub>2</sub>-rich volcanic gas ever recorded at Mo…

2016

Exploring the explosive-effusive transition using permanent ultraviolet cameras

2017

Understanding the mechanisms that cause effusive eruptions is the key to mitigating their associated hazard. Here, we combine results from permanent ultra-violet (UV) cameras, and from other geophysical observations (seismic very long period, thermal, and infrasonic activity), to characterize volcanic SO2 flux regime in the period prior, during, and after Stromboli's August-November 2014 effusive eruption. We show that, in the two months prior to effusion onset, the SO2 flux levels are two times average level. We explain this anomalously high SO2 regime as primarily determined by venting of rapidly rising, pressurized SO2-rich gas pockets, produced by strombolian explosions being more frequ…

Spatially resolved SO2 flux emissions from Mt Etna

2016

We report on a systematic record of SO2 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 SO2 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 SO2 or ~30% of the SO2 emitted by the volcano during the 5 July to 10 August eruptive interval. Acti…

Halogens in volcanic systems

2009

The transport, degassing and atmospheric release of halogens from active volcanism on Earth have been the 12 focus of increasing interest over the last few decades, and have recently been the subject of the 1st workshop 13 on “Halogens in volcanic systems and their environmental impacts” that was held in December of 2007 at 14 Yosemite Lodge in Yosemite National Park, California. As an introduction to this Chemical Geology special 15 issue, collecting contributions from many of the participants at the workshop, we review here recent 16 advances in this field, including experimental and theoretical investigations of halogen behaviour in volcanic 17 and related magmatic systems. We discuss pr…

Hydrothermal buffering of the SO2/H2S ratio in volcanic gases: Evidence from La Fossa Crater fumarolic field, Vulcano Island

2006

[1] Sulfur speciation in volcanic gases is a potentially valuable tracer of degassing processes at volcanoes. Hitherto, observations of sulfur speciation in volcanic gas plumes have however been limited both in number and quality. Here, we report on periodic measurements of SO2 to H2S proportions in the volcanic gases from La Fossa volcano (Vulcano Island) performed during 2004–2006, a period which encompasses two heating events of the fumarolic field in January–April 2005 and December 2005. Results indicate a systematic relative increase (by a factor of 2–6) of SO2 to H2S proportions in the fumaroles during the heating events, which we ascribe to a temperature increase in the mixing zone b…

Chemical mapping of a fumarolic field: La Fossa Crater, Vulcano Island (Aeolian Islands, Italy)

2005

[1] The performance of a newly-developed portable gas analyzer, capable of real-time measurement of CO2, SO2 and H2S concentrations in volcanic gases, was tested at La Fossa Crater, Vulcano Island. The gas analyzer was used to acquire about 3000 determinations over the fumarolic field, allowing the definition of its chemical structure and heterogeneity. Our high-resolution analysis reveals that, in December 2004, the La Fossa fumarolic field was characterized by an oxidized inner core (SO2/H2S ratios of ∼3), and by more reducing conditions on its northern edge (SO2/H2S ratios of ∼1; range: 0.2–3.3). CO2/(SO2+H2S) molar ratios averaged 35 ± 21, with overlapping compositions for rim and inner…

Mantle-derived fluids discharged at the Bradanic foredeep/Apulian foreland boundary: The Maschito geothermal gas emissions (southern Italy)

2014

Abstract The mephitis of Maschito, known since historical times as Lago Fetente (Smelly Lake) -although the lake is now dry-, is located 20 km from the Mt. Vulture volcanic edifice (Southern Italy). It is placed along the same regional tectonic discontinuity where some maars are located, close to the boundary between the foredeep and the Apulian foreland. About 300 m2 of surface is lacking in flora, while dead animals are frequently found all around it. The smelly exhalations are mainly composed of CO2 (∼98%), and, in lesser amounts, of H2S, N2, CH4 and other hydrocarbons. He, Ne and Ar occur in trace amounts. The CO2 isotopic composition is in the range of that of the main active Italian v…

Recent advances in ground-based ultraviolet remote sensing of volcanic SO2 fluxes

2011

Measurements of volcanic SO2 emission rates have been the mainstay of remote-sensing volcanic gas geochemistry for almost four decades, and they have contributed significantly to our understanding of volcanic systems and their impact upon the atmosphere. The last ten years have brought step-change improvements in the instrumentation applied to these observations, which began with the application of miniature ultraviolet spectrometers that were deployed in scanning and traverse configurations, with differential optical absorption spectroscopy evaluation routines. This study catalogs the more recent empirical developments, including: ultraviolet cameras; wide-angle field-of-view differential …