Examinando por Autor "AIUPPA, Alessandro"

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Short-period volcanic gas precursors to phreatic eruptions: Insights from Poás Volcano, Costa Rica
(Elsevier, 2016-03) Kern, C.; Martínez, M.; AIUPPA, Alessandro; Pacheco, José; Avard, Geoffroy; Liuzzo, Marco; Giudice, Gaetano; Fischer, Tobias; De Moor, J. M.
Volcanic eruptions involving interaction with water are amongst the most violent and unpredictable geologic phenomena on Earth. Phreatic eruptions are exceptionally difficult to forecast by traditional geophysical techniques. Here we report on short-term precursory variations in gas emissions related to phreatic blasts at Poás volcano, Costa Rica, as measured with an in situ multiple gas analyzer that was deployed at the edge of the erupting lake. Gas emitted from this hyper-acid crater lake approaches magmatic values of SO2/CO21–6 days prior to eruption. The SO2flux derived from magmatic degassing through the lake is measureable by differential optical absorption spectrometry (sporadic campaign measurements), which allows us to constrain lake gas output and input for the major gas species during eruptive and non-eruptive periods. We can further calculate power supply to the hydrothermal system using volatile mass balance and thermodynamics, which indicates that the magmatic heat flux into the shallow hydrothermal system increases from ∼27 MW during quiescence to ∼59 MW during periods of phreatic events. These transient pulses of gas and heat from the deeper magmatic system generate both phreatic eruptions and the observed short-term changes in gas composition, because at high gas flux scrubbing of sulfur by the hydrothermal system is both kinetically and thermodynamically inhibited whereas CO2gas is always essentially inert in hyperacid conditions. Thus, the SO2/CO2of lake emissions approaches magmatic values as gas and power supply to the sub-limnic hydrothermal system increase, vaporizing fluids and priming the hydrothermal system for eruption. Our results suggest that high-frequency real-time gas monitoring could provide useful short-term eruptive precursors at volcanoes prone to phreatic explosions.
Tracking Formation of a Lava Lake From Ground and Space: Masaya Volcano (Nicaragua), 2014–2017
(American Geophysical Union, 2018-02-22) AIUPPA, Alessandro; de Moor, J. Marteen; Arellano, Santiago; Coppola, Diego; Francofonte, Vincenzo; Galle, Bo; Giudice, Gaetano; Liuzzo, Marco; Mendoza, Elvis; Saballos, Armando; Tamburello, Giancarlo; Battaglia, Angelo; Bitetto, Marcello; Gurrieri, Sergio; Laiolo, Marco; Mastrolia, Andrea; Moretti, Robertto
A vigorously degassing lava lake appeared inside the Santiago pit crater of Masaya volcano (Nicaragua) in December 2015, after years of degassing with no (or minor) incandescence. Here we present an unprecedented-long (3 years) and continuous volcanic gas record that instrumentally characterizes the (re)activation of the lava lake. Our results show that, before appearance of the lake, the volcanic gas plume composition became unusually CO2 rich, as testified by high CO2/SO2 ratios (mean: 12.2 6 6.3) and low H2O/CO2 ratios (mean: 2.3 6 1.3). The volcanic CO2 flux also peaked in November 2015 (mean: 81.3 6 40.6 kg/s; maximum: 247 kg/s). Using results of magma degassing models and budgets, we interpret this elevated CO2 degassing as sourced by degassing of a volatile-rich fast-overturning (3.6–5.2 m3 s21) magma, supplying CO2-rich gas bubbles from minimum equivalent depths of 0.36–1.4 km. We propose this elevated gas bubble supply destabilized the shallow (<1 km) Masaya magma reservoir, leading to upward migration of vesicular (buoyant) resident magma, and ultimately to (re)formation of the lava lake. At onset of lava lake activity on 11 December 2015 (constrained by satellite-based MODIS thermal observations), the gas emissions transitioned to more SO2-rich composition, and the SO2 flux increased by a factor 40% (11.4 6 5.2 kg/s) relative to background degassing (8.0 kg/s), confirming faster than normal (4.4 versus 3 m3 s21) shallow magma convection. Based on thermal energy records, we estimate that only 0.8 of the 4.4 m3 s21 of magma actually reached the surface to manifest into a convecting lava lake, suggesting inefficient transport of magma in the near-surface plumbing system.