Active hydrothermal fluids circulation triggering small-scale collapse events: the case of the 2001–2002 fissure in the Lakki Plain (Nisyros Island, Aegean Sea, Greece)

Venturi, Stefanía; Tassi, Franco; Vaselli, Orlando; Vougioukalakis, Georges; Rashed, Heba; Kanellopoulos, Christos; Caponi, Chiara; Capecchiacci, Francesco; Cabassi, Jacopo; Ricci, Andrea; Giannini, Luciano

doi:10.1007/s11069-018-3318-8

Cited by 11 publications

(6 citation statements)

References 54 publications

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“…During 1995-1998, Nisyros depicted signals of renewing activity, which included intense seismicity, ground deformations, significant variations in the geochemical parameters of fumaroles, and a progressive uplift and E-W extension of the central parts of the island and a possible magma input at greater crustal depth [76,91,92]. This progressive uplift led to a large N-S trending fracture, known as "Lakki rupture", in the Lakki plain of the caldera in early December 2001 [91,93], where a surface stress release took place in the consolidated and cemented epiclastic and hydrothermal sediments of the caldera floor [68].…”

Section: Study Areamentioning

confidence: 99%

Spectral Unmixing for Mapping a Hydrothermal Field in a Volcanic Environment Applied on ASTER, Landsat-8/OLI, and Sentinel-2 MSI Satellite Multispectral Data: The Nisyros (Greece) Case Study

et al. 2020

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The aim of this study was to propose a methodology that provides a detailed description of the argillic zone of a hydrothermal field, based on satellite multispectral data. More specifically, we developed a method based on spectral unmixing where hydroxyl-bearing alteration is represented by a single endmember (representing clays) and the three (nearly) non-altered primary volcanic lithologies, namely, two types of lava flows (basic and acidic compositions) and the loose materials (alluvial/beach deposits, scree, pyroclastic deposits, etc.), are represented by three endmembers. We also used one endmember representing elemental sulfur that is present in fumarolic vents hosted by active hydrothermal craters. The methodology was applied in the south part of Lakki plain inside the Nisyros volcano caldera (Greece), using Sentinel-2, Landsat-8/OLI, and ASTER satellite multispectral datasets. Specifically, it was applied separately to each one of the three datasets. The spectral unmixing results, combined with the relative geological map, provide quantitative estimations of the primary volcanic and loose material areas affected by alteration. In addition, pixels with high abundance values of hydroxyl-bearing alteration corresponded to mapped areas with strong hydrothermal alteration. The developed methodology is superior to conventional approaches (e.g., alteration spectral index) in terms of its ability to describe the overall pattern of the hydrothermal field. The most accurate results were taken when applied to ASTER or Sentinel-2 MSI data.

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Section: Study Areamentioning

confidence: 99%

Spectral Unmixing for Mapping a Hydrothermal Field in a Volcanic Environment Applied on ASTER, Landsat-8/OLI, and Sentinel-2 MSI Satellite Multispectral Data: The Nisyros (Greece) Case Study

et al. 2020

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“…The soils of the Lakki Plain are strongly weathered by past and present fumarolic activity. This can be recognized by the widespread presence of secondary alteration minerals, mainly sulfates [24,25]. The main drivers of the alteration process are fumarolic H 2 O and H 2 S. The former is the main carrier of thermal energy, which is reflected in soil temperatures reaching up to the boiling temperature of water.…”

Section: Mercury In the Soilmentioning

confidence: 99%

“…Nisyros Island is a quiescent volcano releasing hydrothermal gases from several fumarolic emissions and also diffusively through the soil. The hydrothermal fluids of Nisyros are rich in H 2 S [21][22][23], and their diffuse emission creates an extremely acidic environment in soils affected by the hydrothermal degassing [24,25].…”

Section: Introductionmentioning

confidence: 99%

Degassing and Cycling of Mercury at Nisyros Volcano (Greece)

et al. 2019

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Nisyros Island (Greece) is an active volcano hosting a high-enthalpy geothermal system. During June 2013, an extensive survey on Hg concentrations in different matrices (fumarolic fluids, atmosphere, soils, and plants) was carried out at the Lakki Plain, an intracaldera area affected by widespread soil and fumarolic degassing. Concentrations of gaseous elemental mercury (GEM), together with H2S and CO2, were simultaneously measured in both the fumarolic emissions and the atmosphere around them. At the same time, 130 samples of top soils and 31 samples of plants (Cistus creticus and salvifolius and Erica arborea and manipuliflora) were collected for Hg analysis. Mercury concentrations in fumarolic gases ranged from 10,500 to 46,300 ng/m3, while Hg concentrations in the air ranged from high background values in the Lakki Plain caldera (10-36 ng/m3) up to 7100 ng/m3 in the fumarolic areas. Outside the caldera, the concentrations were relatively low (2-5 ng/m3). The positive correlation with both CO2 and H2S in air highlighted the importance of hydrothermal gases as carrier for GEM. On the other hand, soil Hg concentrations (0.023-13.7 μg/g) showed no significant correlations with CO2 and H2S in the soil gases, whereas it showed a positive correlation with total S content and an inverse one with the soil pH, evidencing the complexity of the processes involving Hg carried by hydrothermal gases while passing through the soil. Total Hg concentrations in plant leaves (0.010-0.112 μg/g) had no direct correlation with soil Hg, with Cistus leaves containing higher values of Hg with respect to Erica. Even though GEM concentrations in the air within the caldera are sometimes orders of magnitude above the global background, they should not be considered dangerous to human health. Values exceeding the WHO guideline value of 1000 ng/m3 are very rare (<0.1%) and only found very close to the main fumarolic vents, where the access to tourists is prohibited.

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“…2) are mostly related to a low number of free-state radon atoms residing and accumulating within the altered soil matrix. The persistent and intense circulation of hot, acidic hydrothermal fluids led to argillic alteration and secondary mineralization in this area of the caldera 41 . Accordingly, the soil structure alternates between porous-and sealed portions.…”

Section: Resultsmentioning

confidence: 99%

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

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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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Active hydrothermal fluids circulation triggering small-scale collapse events: the case of the 2001–2002 fissure in the Lakki Plain (Nisyros Island, Aegean Sea, Greece)

Cited by 11 publications

References 54 publications

Spectral Unmixing for Mapping a Hydrothermal Field in a Volcanic Environment Applied on ASTER, Landsat-8/OLI, and Sentinel-2 MSI Satellite Multispectral Data: The Nisyros (Greece) Case Study

Spectral Unmixing for Mapping a Hydrothermal Field in a Volcanic Environment Applied on ASTER, Landsat-8/OLI, and Sentinel-2 MSI Satellite Multispectral Data: The Nisyros (Greece) Case Study

Degassing and Cycling of Mercury at Nisyros Volcano (Greece)

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

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