Alessandro La Spina

Bio: Alessandro La Spina is an academic researcher from National Institute of Geophysics and Volcanology. The author has contributed to research in topics: Lava & Volcano. The author has an hindex of 3, co-authored 16 publications receiving 365 citations. Previous affiliations of Alessandro La Spina include University of Palermo & Centre national de la recherche scientifique.

Magmatic Gas Composition Reveals the Source Depth of Slug-Driven Strombolian Explosive Activity

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.

Crater Gas Emissions and the Magma Feeding System of Stromboli Volcano

Abstract: Quiescent and explosive magma degassing at Stromboli volcano sustains high-temperature crater gas venting and a permanent volcanic plume which constitute key sources of information on the magma supply and dynamics, the physical processes controlling the explosive activity and, more broadly, the volcano feeding system. The chemical composition and the mass output of these crater emissions (gases, trace metals, radioactive isotopes) were measured using different methodologies: within-plume airborne measurements, ground-based plume filtering, and/or in situ analysis, remote UV and open-path Fourier transform infrared absorption spectroscopy. The results obtained, summarized in this paper, demonstrate a primary control of the magmatic gas phase on the eruptive regime and the budget of the volcano. The large excess gas discharge, compared with the lava extrusion rate, and the source depth of slug-driven Strombolian explosions evidence extensive separate gas transfer across the volcano conduits, promoted by the high gas content (vesicularity) and then permeability of the shallow basaltic magma. Combined with data for volatiles dissolved in olivine-hosted melt inclusions, the results provide updated constraints for the magma supply rate (similar to 0.3 m(3) s(-1) average), the ratio of intrusive versus extrusive magma degassing (similar to 15), and the amount of unerupted degassed magma that should be convectively cycled back in conduits and accumulated beneath the volcano over time (similar to 0.25 km(3) in the last three decades). The results also provide insight into the possible triggering mechanism of intermittent paroxysmal explosions and the geochemical signals that might allow forecasting these events in the future.

Patterns of bubble bursting and weak explosive activity in an active lava lake—Halema‘uma‘u, Kīlauea, 2015

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Aerosol Optical Properties of Pacaya Volcano Plume Measured with a Portable Sun-Photometer

Abstract: In this paper, Sun-photometer multichannel measurements of aerosol optical depths (AODs) in the visible and near-infrared spectral ranges, and Angstrom parameters of the plume issued from the Pacaya volcano, Guatemala, are presented for the first time These observations, made during a short-term campaign carried out on 29 and 30 January 2011, indicate a diluted (AODs lower than 01) volcanic plume composed of small particles (Angstrom exponent ∼10 on 29 January and ∼14 on 30 January) Results are consistent with an ash-free plume Finally, the impact of the choice of different wavelength pairs for the calculation of the Angstrom parameters from the spectral AOD observations is tested and critically discussed

Deep Carbon Emissions from Volcanoes

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 …

Silicic magma reservoirs in the Earth's crust

Abstract: ![][1] Magma reservoirs play a key role in controlling numerous processes in planetary evolution, including igneous differentiation and degassing, crustal construction, and volcanism. For decades, scientists have tried to understand what happens in these reservoirs, using an array of techniques such as field mapping/petrology/geochemistry/geochronology on plutonic and volcanic lithologies, geophysical imaging of active magmatic provinces, and numerical/experimental modeling. This review paper tries to follow this multi-disciplinary framework while discussing past and present ideas. We specifically focus on recent claims that magma columns within the Earth’s crust are mostly kept at high crystallinity (“mush zones”), and that the dynamics within those mush columns, albeit modulated by external factors (e.g., regional stress field, rheology of the crust, pre-existing tectonic structure), play an important role in controlling how magmas evolve, degas, and ultimately erupt. More specifically, we consider how the chemical and dynamical evolution of magma in dominantly mushy reservoirs provides a framework to understand: (1) the origin of petrological gradients within deposits from large volcanic eruptions (“ignimbrites”); (2) the link between volcanic and plutonic lithologies; (3) chemical fractionation of magmas within the upper layers of our planet, including compositional gaps noticed a century ago in volcanic series (4) volatile migration and storage within mush columns; and (5) the occurrence of petrological cycles associated with caldera-forming events in long-lived magmatic provinces. The recent advances in understanding the inner workings of silicic magmatism are paving the way to exciting future discoveries, which, we argue, will come from interdisciplinary studies involving more quantitative approaches to study the crust-reservoir thermo-mechanical coupling as well as the kinetics that govern these open systems. [1]: /embed/graphic-1.gif

Excess degassing from volcanoes and its role on eruptive and intrusive activity

Abstract: [1] Volcanoes emit larger amounts of volcanic gas than can be dissolved in the volume of erupted magma during a variety of volcanic processes, including explosive and effusive eruption and noneruptive continuous degassing. Degassing of unerupted magma with a much larger volume than that of erupted magma caused such a large degassing; erupted magma represents only a small portion of the magma that drives volcanic activity. Evaluation of the magma-gas differentiation process causing the excess degassing is necessary to understand eruption processes, magma chamber evolution, and crustal growth by magma intrusion. Three mechanisms are proposed to explain various degassing modes, including eruption of bubble-accumulated magma, degassing of a convecting magma column, and permeable gas transportation from a deep magma chamber. Examples of large degassing in excess of the erupted magma are common in subduction zone volcanism but are rare in rift- and hot spot–associated volcanism.

The Sulfur Budget in Magmas: Evidence from Melt Inclusions, Submarine Glasses, and Volcanic Gas Emissions

Abstract: The major magmatic volatile components—H2O, CO2, S, Cl, and F— play an important role in the formation, evolution, and eruption of magma. Knowledge of magmatic concentrations and fluxes of these volatiles is thus important for understanding explosive eruptive behavior of volcanoes, recycling of volatiles in subduction zones, formation of magmatic-hydrothermal ore deposits, fluxes of volcanic gases to Earth’s atmosphere, and potential climatic impacts of large volcanic eruptions. Over the past 30 years, new analytical techniques for measuring volatiles in melt inclusions and glasses from volcanic rocks and new developments in remote sensing technology used for quantifying volcanic emissions have led to major advances in our understanding of volatiles in magmatic systems and their fluxes from Earth’s mantle to the crust and hydrosphere. Sulfur plays a particularly important role in many of the processes noted above because it affects partitioning of metals into sulfide phases or vapor in magmas during crustal storage, and when released to the atmosphere, it forms sulfuric acid aerosol droplets that catalyze ozone destruction, influences other aspects of atmospheric chemistry, and blocks incoming solar radiation. In addition, S may play a role in causing oxidation of the mantle wedge above subduction zones (Kelley and Cottrell 2009). In silicate melts, the solubility behavior, activity-composition relations, and vapor-melt partitioning of S are complex due to multiple valence states and species (S2−, S6+ in melt; H2S, S2, SO2, SO3 in vapor) and the occurrence of non-volatile S-rich phases (immiscible Fe-S-O liquid, pyrrhotite, monosulfide and intermediate solid solutions, anhydrite). Sulfur dioxide (SO2) is the easiest of the main magmatic volatiles to measure in volcanic plumes using ground- and satellite-based remote sensing techniques because of its relatively high concentration in volcanic plumes relative to background values. More …