Sulphur output and magma degassing budget of Stromboli volcano
TL;DR: In this article, air-borne measurements of the plume flux of Stromboli volcano during 1980-93 show that the volcano emits very large amounts of gas, mostly by open-conduit degassing between explosive outbursts, while exuding little basalt.
Abstract: STROMBOLI volcano in the Aeolian islands has been erupting continuously for more than 2,000 years1, and probably as many as 5,000, following a major flank collapse2,3. Here we describe air-borne measurements of the plume flux of SO2 during 1980–93, which show that the volcano emits very large amounts of gas, mostly by open-conduit degassing between explosive outbursts, while exuding little basalt. Microprobe analysis of sulphur in the K-rich (shoshonitic) basalt, along with data for primitive basalts in the region4,5, suggests that the time-averaged SO2 flux is produced by intrusive degassing of 0.01-0.02 km3 yr-1 of magma, 100-200 times more than the volume erupted. Over 5,000 years, this rate implies that 50-100 km3 of intruded basalt would have been degassed, suggesting either that the volcanic pile has grown substantially by intrusion6 or, more probably, that a large magma storage system is emplaced at a shallow level within the crustal basement. Our results indicate that Etna and Stromboli alone provide 10% of the global budget of volcanic SO2.
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TL;DR: In this article, the effect of volatile fractionation during magma degassing, investigated using new rare gas and CO2 abundances determined simultaneously for a suite of Mid-Ocean Ridge (MOR) basalt glasses, is not the major factor controlling the spread of data, which mainly result from volatile heterogeneity in the mantle source.
410 citations
TL;DR: This paper presents a comprehensive assessment of the input sources and transport pathways of polycyclic aromatic hydrocarbons found in the coastal sediments of Macao, based on measurements of 48 2-7 ring PAHs and 7 sulfur/oxygenated (S/O) PAH derivatives in 45 sediment, 13 street dust, and 68 aerosol samples.
Abstract: The coastal region off Macao is a known depositional zone for persistent organic pollutants (POPs) in the Pearl River Delta and Estuary of southern China and an important gateway for the regional c...
374 citations
TL;DR: The role of CO2 degassing from the Earth is clearly fundamental to the stability of the climate, and therefore to life on Earth as discussed by the authors, but the uncertainty in our knowledge of this critical input into the geological carbon cycle led Berner and Lagasa (1989) to state that it is the most vexing problem facing us in understanding that cycle.
Abstract: Over long periods of time (~Ma), we may consider the oceans, atmosphere and biosphere as a single exospheric reservoir for CO2. The geological carbon cycle describes the inputs to this exosphere from mantle degassing, metamorphism of subducted carbonates and outputs from weathering of aluminosilicate rocks (Walker et al. 1981). A feedback mechanism relates the weathering rate with the amount of CO2 in the atmosphere via the greenhouse effect (e.g., Wang et al. 1976). An increase in atmospheric CO2 concentrations induces higher temperatures, leading to higher rates of weathering, which draw down atmospheric CO2 concentrations (Berner 1991). Atmospheric CO2 concentrations are therefore stabilized over long timescales by this feedback mechanism (Zeebe and Caldeira 2008). This process may have played a role (Feulner et al. 2012) in stabilizing temperatures on Earth while solar radiation steadily increased due to stellar evolution (Bahcall et al. 2001). In this context the role of CO2 degassing from the Earth is clearly fundamental to the stability of the climate, and therefore to life on Earth. Notwithstanding this importance, the flux of CO2 from the Earth is poorly constrained. The uncertainty in our knowledge of this critical input into the geological carbon cycle led Berner and Lagasa (1989) to state that it is the most vexing problem facing us in understanding that cycle.
Notwithstanding the uncertainties in our understanding of CO2 degassing from Earth, it is clear that these natural emissions were recently dwarfed by anthropogenic emissions, which have rapidly increased since industrialization began on a large scale in the 18th century, leading to a rapid increase in atmospheric CO2 concentrations. While atmospheric CO2 concentrations have varied between 190–280 ppm for the last 400,000 years (Zeebe and Caldeira 2008), human activity has produced a remarkable increase …
309 citations
TL;DR: In this paper, atmospheric Pb deposition since the Industrial Revolution was studied in western, central, and southern Switzerland using five rural peat bogs, and two distinct periods of Pb enrichment relative to the natural background were found in western and central Switzerland, with enrichments ranging from 40 to 80 times, and between 1960 and 1980 with enrichment values ranging from 80 to 100 times.
Abstract: Atmospheric Pb deposition since the Industrial Revolution was studied in western, central, and southern Switzerland using five rural peat bogs. Similar temporal patterns were found in western and central Switzerland, with two distinct periods of Pb enrichment relative to the natural background: between 1880 and 1920 with enrichments ranging from 40 to 80 times, and between 1960 and 1980 with enrichments ranging from 80 to 100 times. The fluxes also were generally elevated in those time periods: in western Switzerland between 1.16 and 1.55 μg cm-2 y-1 during the first period, and in western and central Switzerland between 0.85 and 1.55 μg cm-2 y-1 during the second period. Between the Industrial Revolution and 1985, nonradiogenic Pb became increasingly important in all five cores because of the replacement of coal by oil after ca. 1920, the use of Australian Pb in industry, and the extensive combustion of leaded gasoline after 1950. The introduction of unleaded gasoline in 1985 had a pronounced effect on...
299 citations
TL;DR: Spectroscopic measurements performed during both quiescent degassing and explosions on Stromboli volcano are used to demonstrate that gas slugs originate from as deep as the volcano-crust interface (∼3 kilometers), where both structural discontinuities and differential bubble-rise speed can promote slug coalescence.
Abstract: Strombolian-type eruptive activity, common at many volcanoes, consists of regular explosions driven by the bursting of gas slugs that rise faster than surrounding magma. Explosion quakes associated with this activity are usually localized at shallow depth; however, where and how slugs actually form remain poorly constrained. We used spectroscopic measurements performed during both quiescent degassing and explosions on Stromboli volcano (Italy) to demonstrate that gas slugs originate from as deep as the volcano-crust interface (∼3 kilometers), where both structural discontinuities and differential bubble-rise speed can promote slug coalescence. The observed decoupling between deep slug genesis and shallow (∼250-meter) explosion quakes may be a common feature of strombolian activity, determined by the geometry of plumbing systems.
294 citations
References
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Book•
01 Jan 1982
TL;DR: The orogenic andesite association is the basalt-andesite-dacite-rhyolite association characteristic of island ares, active continental margins, and continental collision zones as discussed by the authors.
Abstract: The orogenic andesite association is the basalt-andesite-dacite-rhyolite association characteristic of island ares, active continental margins, and continental collision zones. This book is intended as a reference text for under graduate, postgraduate, and research workers who wish to gain an insight into the orogenic andesite association. It contains invited contributions covering the geology, volcanology, petrology, and geochemistry of orogenic andesites and related rocks, the role of such rocks through geological time, and the wider implications of andesite volcanism such as continental growth and the formation of economic mineral deposits. There were several reasons for producing such a volume. These include the abundance and importance of orogenic andesite volcanism in continental areas, and the important advances in our understanding of such volcanism achieved since the development of pi ate tectonics in the late 1960s. Noting the existence of several volumes devoted to the rarer alkaline rocks, it was felt that it would be valuable to produce a volume devoted entirely to the orogenic andesite association. The volume is divided into 10 sections, chosen to cover all aspects of the association. Section I is a brief introduction to the setting of orogenic andesite volcanism and how the problems posed by these volcanic rocks have evolved during the last few decades. Section II is a general account of the terminology and classification of orogenic volcanic rocks, with a review of the petrology and mineralogy. In Section III, the characteristics of each of the major orogenic volcanic provinces are reviewed and Section IV outlines the evolution of volcanism through time in relation to plate tectonic activity in contrasted provinces. The later sections of the book outline the characteristics of andesite volcanoes and their products (Section V), the relationship of andesitic volcanism to intrusive activity (Section VI), and experimental, chemical, and isotopic characteristics of andesites and related orogenic volcanic rocks (Sections VII and VIII). Some characteristics of andesite volcanism throughout geological time are explained by reference to Archaean volcanic rocks and to Upper Proterozoic volcanism in north-eastern Africa and Arabia and Lower Palaeozoic volcanism in the Caledonian orogenic belt of Britain (Section IX). In conclusion, Section X emphasizes the importance of andesitic volcanism by examining the role of such volcanism in continental growth, in large-scale geochemical cycles, in the eruption of volcanic gases, and in the formation of mineral deposits.
544 citations
TL;DR: In this article, a broad band of viscous fluid, uniform in depth across a slope, released so as to flow down a constant slope is considered, and an expression for the wavelength of the front is determined by surface tension and is independent of the coefficient of viscosity.
Abstract: If viscous fluid is released on a horizontal surface it rapidly takes up a circular plan form as it spreads. This form is observed1,2 to be stable to any small disturbances which are initiated on the front due, for example, to irregularities in the horizontal surface or to chance perturbations. Alternatively, if some fluid is released onto a sloping surface—for example, some liquid detergent on a slanted plate—a quite different plan form occurs. One, two or more extended regions of fluid develop downslope, as shown in Fig. 1a, b. A situation intermediate between these two is now discussed. Consider a broad band of viscous fluid, uniform in depth across a slope, released so as to flow down a constant slope. By following the motion, which is initially independent of the cross-slope coordinate, the speed of advance and the depth of the flow before it breaks up into a series of waves of ever increasing amplitude can be determined. I present an expression for the wavelength of the front, which is determined by surface tension and is independent of the coefficient of viscosity.
529 citations
TL;DR: In this article, the authors used data collected from 1975 to 1987 to estimate carbon dioxide emissions from the summit craters and the upper flanks of the volcano and found that the average output of CO2 from summit crater degassing is 13±3 Tg yr−1, an order of magnitude higher than the annual CO2 output from Kilauea, Hawaii, and representative arc volcanoes.
Abstract: MOUNT Etna, in Sicily, is one of the world's most actively degassing volcanoes1. Here we use data collected from 1975 to 1987 to estimate carbon dioxide emissions from the summit craters and the upper flanks of the volcano. By combining measurements of the SO2 flux in the plume (refs 1–6 and this paper) with measurements of the CO2/SO2 ratio of the plume gases, we find that the average output of CO2 from summit crater degassing is 13±3 Tg yr−1. This is an order of magnitude higher than the annual CO2 output from Kilauea7,8, Hawaii, and representative arc volcanoes9,10. Furthermore, we find that diffuse emissions of CO2 from the upper flanks of Etna are magma-derived and are of a similar magnitude to those emitted from the crater plume. This observation, as well as others11–14, verifies the idea15 that extensive diffuse release of magmatic CO2 may occur in volcanically active regions—a process that needs to be taken into account when evaluating the volatile budget of subaerial volcanism. Such degassing may be of use for monitoring volcanic activity, could provide a means for radiocarbon dating of eruptions, and may be a mechanism by which CO2 is injected into crater lakes.
474 citations
TL;DR: In this article, the immiscible Fe-S-O liquid saturation surface for basaltic liquids in T-X-ƒ o 2 -ƒ s 2 space is made through consideration of the heterogeneous equilibrium 1 2 S 2 (gas) + FeO (silicate melt) = FeS (sulfide melt) + 1 2 O 2(gas), using standard state thermodynamic data.
412 citations
TL;DR: In this article, a model of the gas thrust process is developed and values are deduced for the gas/solid mass ratio in the ejected material, and a model in which large bursting gas bubbles are responsible for the explosions is shown to be compatible with the observations.
Abstract: Strombolian explosions at Heimaey and Stromboli are described. Two main components of activity within a typical strombolian explosion are distinguished: an initial, high velocity, gas thrust part due to gas decompression and a subsequent convective part. Initial gas velocities at Heimaey averaged 157 m/s (standard deviation 28 m/s from 15 observations) and at Stromboli 31 m/s (standard deviation 12 m/s from 8 observations) for one vent and 56 m/s for a second vent. Velocities decreased approximately exponentially with height, and decelerations of up to 50 gravities were observed during the gas thrust events. A model of the gas thrust process is developed and values are deduced for the gas/solid mass ratio in the ejected material. Evidence is resented for the several-foId concentration of gas into that part f the magma expelled explosively, and a model in which large bursting gas bubbles are responsible for the explosions is shown to be compatible with the observations. Excess pressure within such bubbles is found to be of order 2.5 × 10 4 N/m (0.25 atmospheres) at Heimaey and 600N/m 2 (0.006 atmospheres) at Stromboli. Pressures inside bubbles of a few metres diameter are found to be of comparable magnitudes. Average gas release rates of 3 to 6 × 10 3 kgm/s at Heimaey and at least 0.13 kgm/s at Stromboli are indicated.
315 citations