Diffuse emission of CO2 and convective heat release at Nisyros caldera (Greece)

Bini, Giulio; Chiodini, Giovanni; Cardellini, Carlo; Vougioukalakis, Georges; Bachmann, Olivier

doi:10.1016/j.jvolgeores.2019.03.017

Cited by 32 publications

(35 citation statements)

References 54 publications

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“…These explosive erupaped the present-day caldera morphology of the island, which r partly filled with rhyodacite domes ("post-caldera domes") rhyolitic explosive events and one rhyolitic effusive eruption (an obsidian flow) created the smaller island of Yali. Nowadays, intense fumarolic activity takes place on the caldera floor of Nisyros and the volcano occasionally shows signs of unrest (Chiodini et al, 2002;Bini et al, 2019).…”

Section: Discussionmentioning

confidence: 99%

A connection between magma chamber processes and eruptive styles revealed at Nisyros-Yali volcano (Greece)

Popa

Ellis

Degruyter

et al. 2019

Journal of Volcanology and Geothermal Research

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Arc volcanoes generally emit water-rich, high-viscosity silicic magmas, which are prone to erupt explosively. However, effusive behavior is a common occurrence despite the high-H 2 O, high viscosity conditions. The contrasting shift from effusive to explosive behavior (and viceversa) at any individual volcano raises the question on what controls eruptive style. Permeability development in conduits allows magma to outgas and is clearly a key factor. However, an important question is whether magma reservoir processes can also have an influence on eruptive styles. The answer could have direct impact on predicting eruptive behavior. Hence, we explore this potential connection by analyzing nine alternating effusive and explosive silicic deposits that were emplaced during distinct eruptions at the active Nisyros-Yali volcanic center. The lavas and pyroclastic deposits are compositionally similar. This indicates a negligible influence of the bulk rock composition on different eruptive styles. The crystal contents vary between units, without any clear correlation with eruptive style (from nearly aphyric to ~45 vol% crystals). Mineral textures and chemistry do show variations between effusive and explosive eruptions, with a larger proportion of resorbed plagioclase and more evolved amphiboles present in the lava flows. Mineral thermobarometry and hygrometry show that the storage zones of magmas generating effusive eruptions evolved towards colder and more water-rich conditions (710-790˚C; 5.6-6.5 wt% H 2 O) than their explosive counterparts (815-850˚C; 4.2-4.6 wt% H 2 O). At storage pressures of 1.5-2 kbar, relevant for Nisyros-Yali, the volatile saturation level is reached at > 5 wt% H 2 O. It is likely that the magmas reached water-saturation before generating effusive eruptions, and were undersaturated before explosive events. We hypothesize that the presence of exsolved gas in the subvolcanic reservoir can enhance the outgassing potential of the magma during conduit ascent. Hence, the rhyolitic effusive-explosive transitions can be influenced by the pre-eruptive exsolved versus dissolved state of the volatiles in the magma chamber. This can lead to the less explosive eruptions for the most water-rich reservoir conditions.

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Section: Discussionmentioning

confidence: 99%

A connection between magma chamber processes and eruptive styles revealed at Nisyros-Yali volcano (Greece)

Popa

Ellis

Degruyter

et al. 2019

Journal of Volcanology and Geothermal Research

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“…This coincidence is not surprising, because both the anomalies are generated by the subsurface condensation of vapors rising from the hydrothermal system located at depth in the Lakki plain (ref. 19 and refs therein). In detail, the anomalously high temperatures reflect the latent heat of condensation, while the high C CO2 are caused by the CO 2 contents of the original hydrothermal vapors.…”

Section: Resultsmentioning

confidence: 93%

“…(c) Probability map of the CO 2 flux measured during October 2018 (redrawn after ref. 19 ). The 9 diffuse degassing structures (DDS) are defined by solid line perimeters.…”

Section: Resultsmentioning

confidence: 99%

“…See the text for further explanation. 18,19,21 ). The environmental factors (e.g., air-soil temperature and humidity, rain, wind speed) can affect the biogenic soil CO 2 emission [26][27][28][29][30] by favoring soil respiration processes (i.e., roots, microbial and fauna respiration, and decomposition of organic matter 31 ).…”

Section: Resultsmentioning

confidence: 99%

“…11 , the diffuse emission of CO 2 from the soil was measured with the accumulation chamber (AC) methodology, employing an instrument developed at the Università di Perugia and described in detail in ref. 19 . The gas line from the infrared sensor (IR) to the AC, was modified by inserting a T-connector with a pierceable septum which permits direct sampling of the gas phase 2,10,49 (see Fig.…”

Section: Discussionmentioning

confidence: 99%

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Deep versus shallow sources of CO2 and Rn from a multi-parametric approach: the case of the Nisyros caldera (Aegean Arc, Greece)

Bini

Chiodini

Lai

et al. 2020

Sci Rep

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estimating the quantity of co 2 diffusively emitted from the Earth's surface has important implications for volcanic surveillance and global atmospheric co 2 budgets. However, the identification and quantification of non-hydrothermal contributions to CO 2 release can be ambiguous. Here, we describe a multi-parametric approach employed at the nisyros caldera, Aegean Arc, Greece, to assess the relative influence of deep and shallow gases released from the soil. In April 2019, we measured diffuse soil surface co 2 fluxes, together with their carbon isotope compositions, and at a depth of 80 cm, the co 2 concentration, soil temperature, and the activities of radon and thoron. the contributions of deep co 2 and biogenic co 2 fluxes were distinguished on the basis of their carbon isotope compositions. A Principal Component Analysis (PCA), performed on the measured parameters, effectively discriminates between a deep-and a shallow degassing component. the total co 2 output estimated from a relatively small testing area was two times higher with respect to that observed in a previous survey (October 2018). The difference is ascribed to variation in the soil biogenic CO 2 production, that was high in April 2019 (a wet period) and low or absent in October 2018 (a dry period). Accounting for seasonal biogenic activity is therefore critical in monitoring and quantifying co 2 emissions in volcanic areas, because they can partially-or completely overwhelm the volcanic-hydrothermal signal. The emission of volcanic-hydrothermal fluids from fumaroles and soil diffuse degassing structures (DDS) are prevalent forms of thermal energy release in quiescent volcanoes 1,2 , and their monitoring is of primary importance in understanding volcanic activity 3-6. The amount of CO 2 emitted by volcanic DDS is thought to be, globally, a relevant contributor (likely the most important) to the CO 2 budget from volcanic activity to the atmosphere 7,8. However, the uncertainties in determining the amount of the volcanic diffuse CO 2 emission are significant, as biological activity can also produce abundant CO 2. In fact, over the last 20 years, the definition and characterization of the diffuse degassing processes has been based, with a few exceptions, only on CO 2 flux measurements without differentiating between their possibly disparate deep-(i.e., volcanic-hydrothermal) or shallow (i.e., biogenic) sources. Coupling CO 2 flux measurements with other parameters collected from the surface or within the soil in volcanic areas (e.g. 2,9,10), can be crucial to better decipher the actual fraction of gas emitted from magmatichydrothermal systems. This approach is of fundamental importance in cases where the statistical partitioning 11 and subsequent removal from the total CO 2 output of non-hydrothermal CO 2 flux (of biogenic origin) is not easily applicable or ambiguous. Ultimately, a multi-parametric strategy circumvents over-interpretation in the extent and the amount of deep degassing estimated for active volcanoes worldwide. In addition to monitor...

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Quantification of volcanic degassing and analysis of uncertainties using numerical modeling: the case of Stephanos crater (Nisyros Island, Greece)

Massaro,

Tamburello,

Bini

et al. 2024

Bull Volcanol

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Nisyros Island (Greece) is affected by widespread gas emissions from fumarolic fields located at the bottom of hydrothermal craters in the southern part of its caldera. This morphology and the current low gas fluxes make Nisyros an ideal site for testing the limits of physics-based gas dispersal models in confined and low-emission conditions. Here, we focused our attention on the local scale volcanic gas dispersion from the Stephanos hydrothermal crater. In April 2023, a 1-week survey was carried out to measure weather data, CO2 and H2S gas fluxes, air concentrations from portable gas stations, and chemical composition of fumarolic gases and to acquire thermal images of the crater floor. These data were used as inputs and boundary conditions for numerical simulations using a DISGAS-2.6.0 model in order to quantify the present-day volcanic degassing and its associated uncertainties, accounting for the meteorological variability. Model results are provided in terms of H2S probabilistic exceedance and persistence maps, showing gas concentrations within the crater that fall below the thresholds indicated for the occurrence of serious respiratory problems. Since DISGAS-2.6.0 does not account for chemical reactions, this study represents a good opportunity to discuss the methodological limits of simulating the dispersion of H2S which is challenging due to its rapid degradation and dilution in the atmosphere. In this regard, we also provided an empirical law of the H2S depletion in low-emission conditions that takes into account the uncertainties related to the field measurements.

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Diffuse emission of CO2 and convective heat release at Nisyros caldera (Greece)

Cited by 32 publications

References 54 publications

A connection between magma chamber processes and eruptive styles revealed at Nisyros-Yali volcano (Greece)

A connection between magma chamber processes and eruptive styles revealed at Nisyros-Yali volcano (Greece)

Deep versus shallow sources of CO2 and Rn from a multi-parametric approach: the case of the Nisyros caldera (Aegean Arc, Greece)

Quantification of volcanic degassing and analysis of uncertainties using numerical modeling: the case of Stephanos crater (Nisyros Island, Greece)

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