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  • 1
    Publication Date: 2021-12-13
    Description: Volcanic lake research boosted after lethal gas burst occurred at Lake Nyos (Cameroon) in 1986, a limnic rather than a volcanic event. This led to the foundation of the IAVCEI-Commission on Volcanic Lakes, which grew out into a multi-disciplinary scientific community since the 1990s. We here introduce the first data base of volcanic lakes VOLADA, containing 474 lakes, a number that, in our opinion, is surprisingly high. VOLADA could become an interactive, open-access working tool where our community can rely on in the future. Many of the compiled lakes were almost unknown, or at least unstudied to date, whereas there are acidic crater lakes topping active magmat- ic–hydrothermal systems that are continuously or discontinuously monitored, providing useful information for volcanic surveillance (e.g., Ruapehu, Yugama, Poás). Nyos-type lakes, i.e. those hosted in quiescent volcanoes and characterized by significant gas accumulation in bottom waters, are potentially hazardous. These lakes tend to remain stably stratified in tropical and sub-tropical climates (meromictic), leading to long-term build- up of gas, which can be released after a trigger. Some of the unstudied lakes are possibly in the latter situation. Acidic crater lakes are easily recognized as active, whereas Nyos-type lakes can only be recognized as potentially hazardous if bottom waters are investigated, a less obvious operation. In this review, research strategies are lined out, especially for the “active crater lakes”. We make suggestions for monitoring frequency based on the principle of the “residence time dependent monitoring time window”. A complementary, multi-disciplinary (geochemis- try, geophysics, limnology, statistics) approach is considered to provide new ideas, which can be the bases for fu- ture volcanic lake monitoring. More profound deterministic knowledge (e.g., precursory signals for phreatic eruptions, or lake roll-over events) should not only serve to enhance conceptual models of single lakes, but also serve as input parameters in probabilistic approaches. After more than 25 years of pioneering studies on rather few lakes (~20% of all), the scientific community should be challenged to study the many poorly studied volcanic lakes, in order to better constrain the related hazards.
    Description: Published
    Description: 78-97
    Description: 2V. Dinamiche di unrest e scenari pre-eruttivi
    Description: JCR Journal
    Description: restricted
    Keywords: Volcanic lakes ; Active crater lakes ; Nyos-type lakes ; Monitoring ; Residence time dependent monitoring time window ; Hazard forecasting ; VOLADA data base ; 04. Solid Earth::04.08. Volcanology::04.08.06. Volcano monitoring
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Type: article
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  • 2
    Publication Date: 2024-05-09
    Description: The genetic relationship between carbon-bearing species (CO, CO2, CH4, C2H6, C3H8, C2H4 and C3H6) was investigated in volcanic-hydrothermal gases emitted from Nisyros (Greece), Vesuvio, La Solfatara (Campi Flegrei) and Pantelleria (all Italy). Apparent carbon isotopic temperatures of the CH4-CO2 system are ~360°C at Nisyros, 420-460°C at Vesuvio, ~450°C at La Solfatara and ~540°C at Pantelleria. These temperatures are confirmed by measured propene/propane and H2/H2O concentration ratios. CH4 and CO2 equilibrate in the single liquid phase prior to the onset of boiling, whereas propene and propane attain equilibrium in the saturated water vapor phase. Boiling in these high-enthalpy hydrothermal systems might occur isothermally. Once vapor has been extracted from the parental liquid, CO/CO2 responds most sensitively to the temperature gradient encountered by the ascending gases. Our results imply that the CH4-CO2 isotopic geothermometer can provide reliable information about temperatures of deep hydrothermal liquids associated with volcanism. Propene/propane and H2/H2O concentration ratios should be measured along with the carbon isotopic composition of CO2 and CH4 to provide independent constraints on the geological significance of the apparent carbon isotopic temperatures.
    Description: Published
    Description: 66–75
    Description: 1.2. TTC - Sorveglianza geochimica delle aree vulcaniche attive
    Description: JCR Journal
    Description: restricted
    Keywords: Hydrocarbons ; Hydrothermal fluids ; Volcanoes ; Geothermometry ; 03. Hydrosphere::03.04. Chemical and biological::03.04.05. Gases ; 03. Hydrosphere::03.04. Chemical and biological::03.04.06. Hydrothermal systems
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Type: article
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  • 3
    Publication Date: 2024-05-09
    Description: We have analyzed the carbon isotopic composition of CO2, methane, ethane, propane and n-butane, the hydrogen isotopic composition of methane as well as total concentrations of gas constituents contained in theMediterranean volcanic–hydrothermal discharges of Nisyros (Greece), Vesuvio, La Solfatara, Ischia and Pantelleria (all Italy) to determine the origin of the hydrocarbons. Isotopic criteria conventionally used for hydrocarbon classification suggest thermogenic origins, except for Pantelleria, for which an abiogenic origin is indicated. These findings would imply that thermogenic sources can provide methane/(ethane + propane) concentration ratios as high as those usually observed for microbial hydrocarbons. However, additional consideration of gas concentration data challenges the suitability of conventional criteria for the classification of hydrocarbons emanating from hydrothermal environments. Methane seems to be in close equilibrium with co-occurring CO2, whereas its higher chain homologues are not. Therefore, it cannot be excluded that methane on the one hand and ethane, propane and n-butane on the other hand have distinct origins. The carbon isotopic composition of methane might be controlled by the carbon isotopic composition of co-occurring inorganic CO2 and by hydrothermal temperatures whereas the carbon isotopic composition of the higher n-alkanes could correspond to the maturity of organic matter and/or to the residence time of the gasses in the source system
    Description: Published
    Description: 152–163
    Description: 2V. Dinamiche di unrest e scenari pre-eruttivi
    Description: JCR Journal
    Description: restricted
    Keywords: Hydrocarbons ; Abiogenic ; Thermogenic ; Stable isotopes ; Fumaroles ; 04. Solid Earth::04.04. Geology::04.04.12. Fluid Geochemistry ; 04. Solid Earth::04.08. Volcanology::04.08.01. Gases
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Type: article
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