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  • 05. General::05.02. Data dissemination::05.02.03. Volcanic eruptions  (6)
  • 04. Solid Earth::04.01. Earth Interior::04.01.02. Geological and geophysical evidences of deep processes  (3)
  • Elsevier  (9)
  • Essen : Verl. Glückauf
  • Krefeld : Geologischer Dienst Nordhein-Westfalen
  • 2020-2024
  • 2015-2019
  • 2005-2009  (9)
  • 2005  (9)
Sammlung
Verlag/Herausgeber
Erscheinungszeitraum
  • 2020-2024
  • 2015-2019
  • 2005-2009  (9)
Jahr
  • 1
    Publikationsdatum: 2020-10-29
    Beschreibung: We have performed a parametric study on the dynamics of trachytic (alkaline) versus rhyolitic (calc-alkaline) eruptions by employing a steady, isothermal, multiphase non-equilibrium model of conduit flow and fragmentation. The employed compositions correspond to a typical rhyolite and to trachytic liquids from Phlegrean Fields eruptions, for which detailed viscosity measurements have been performed. The investigated conditions include conduit diameters in the range 30–90 m and total water contents from 2 to 6 wt%, corresponding to mass flow rates in the range 106–108 kg/s. The numerical results show that rhyolites fragment deep in the conduit and at a gas volume fraction ranging from 0.64 to 0.76, while for trachytes fragmentation is found to occur at much shallower levels and higher vesicularities (0.81–0.85). An unexpected result is that low-viscosity trachytes can be associated with lower mass flow rates with respect to more viscous rhyolites. This is due to the non-linear combined effects of viscosity and water solubility affecting the whole eruption dynamics. The lower viscosity of trachytes, together with higher water solubility, results in delayed fragmentation, or in a longer bubbly flow region within the conduit where viscous forces are dominant. Therefore, the total dissipation due to viscous forces can be higher for the less viscous trachytic magma, depending on the specific conditions and trachytic composition employed. The fragmentation conditions determined through the simulations agree with measured vesicularities in natural pumice clasts of both magma compositions. In fact, vesicularities average 0.80 in pumice from alkaline eruptions at Phlegrean Fields, while they tend to be lower in most calc-alkaline pumices. The results of numerical simulations suggest that higher vesicularities in alkaline products are related to delayed fragmentation of magmas with this composition. Despite large differences in the distribution of flow variables which occur in the deep conduit region and at fragmentation, the flow dynamics of rhyolites and trachytes in the upper conduit and at the vent can be very similar, at equal conduit size and total water content. This is consistent with similar phenomenologies of eruptions associated with the two magma types.
    Beschreibung: Published
    Beschreibung: 93-108
    Beschreibung: partially_open
    Schlagwort(e): trachytic magma ; conduit flow ; eruption dynamics and numerical simulations ; 04. Solid Earth::04.08. Volcanology::04.08.03. Magmas ; 04. Solid Earth::04.08. Volcanology::04.08.07. Instruments and techniques ; 05. General::05.02. Data dissemination::05.02.03. Volcanic eruptions
    Repository-Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
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  • 2
    Publikationsdatum: 2020-12-17
    Beschreibung: The Neapolitan Yellow Tuff (NYT) is the product of the largest known trachytic phreatoplinian eruption. It covered an area larger than 1000 km2 with an estimated volume of about 40 km3 of erupted magma. During the course of the eruption a caldera collapsed within the previously formed Campanian Ignimbrite caldera. The resulting nested structure strongly influenced the following volcanic activity in the Campi Flegrei caldera. As previous dating of the NYT does not converge toward a unique result, a new set of 40Ar/39Ar age determinations has been carried out to better constrain the age of the eruption. Two variants of the 40Ar/39Ar dating method were applied to determine the age of the NYT eruption: (1) single-crystal total fusion (SCTF), on an individual phenocryst of feldspar, and (2) laser incremental heating (LIH), on bulk aliquots of feldspar phenocrysts. The results of the SCTF analyses show that the overall sample weighted mean age, derived from the conventional age calculation, is 15.6 ;0.8 ka. A weighted mean of the isochron age is 15.3 ;1.2 ka (2c), and has been assumed as the best indicator of age to be derived from the SCTF analyses. The LIH analyses results show that plateau ages vary from 15.4; 0.5 to 14.5; 0.5 ka. The overall weighted mean age of the isochron results is 14.9;0.4 ka (2c). This result has been assumed as the reference age for the NYT eruption, and agrees with the SCTF age. The new age obtained for the NYT deposits is of great relevance for the understanding of the evolution and the present state of the Campi Flegrei caldera and collocates the NYT in a crucial stratigraphical position to date the climatic oscillations that occurred between the Late Glacial and the Holocene.
    Beschreibung: Published
    Beschreibung: 157-170
    Beschreibung: partially_open
    Schlagwort(e): Neapolitan Yellow Tuff ; Campi Flegrei caldera ; 40Ar/39Ar dating method ; Geochronology ; Late Glacial ; Holocene ; 04. Solid Earth::04.04. Geology::04.04.02. Geochronology ; 04. Solid Earth::04.04. Geology::04.04.10. Stratigraphy ; 04. Solid Earth::04.08. Volcanology::04.08.05. Volcanic rocks ; 05. General::05.02. Data dissemination::05.02.03. Volcanic eruptions
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  • 3
    Publikationsdatum: 2017-04-04
    Beschreibung: While the eruptive record of Mount Etna is reasonably complete for the past 400 years, the activity of the early and late 1960s, which took place at the summit, is poorly documented in the scientific literature. From 1955 to 1971, the Central and Northeast Craters were the sites of long-lived mild Strombolian and effusive activity, and numerous brief episodes of vigorous eruptive activity, which led to repeated overflows of lava onto the external flanks of the volcano. A reconstruction of the sequence of the more important of these events based on research in largely obscure and nearly inaccessible sources permits a better understanding of the eruption dynamics and rough estimates of erupted volumes and of the changes to the morphology of the summit area. During the first half of 1964, the activity culminated in a series of highly dynamic events at the Central Crater including the opening of a fissure on the E flank of the central summit cone, lava fountains, voluminous tephra emission, prolonged strong activity with continuous lava overflows, and growth of large pyroclastic intracrater cones. Among the most notable processes during this eruption was the breaching of a section of the crater wall, which was caused by lateral pressure of lava ponding within the crater. Comparison with the apparently similar summit activity of 1999 allows us to state that (a) lava overflows from large pit craters at the summit are often accompanied by breaching of the crater walls, which represents a significant hazard to nearby observers, and that (b) eruptive activity in 1999 was much more complex and voluminous than in 1964. For 1960s standards however, the 1964 activity was the most important summit eruption in terms of intensity and output rates for about 100 years, causing profound changes to the summit morphology and obliterating definitively the former Central Crater.
    Beschreibung: Published
    Beschreibung: 203-218
    Beschreibung: partially_open
    Schlagwort(e): Mount Etna ; Summit eruption ; Crater morphology and Lava overflows ; 04. Solid Earth::04.08. Volcanology::04.08.03. Magmas ; 04. Solid Earth::04.08. Volcanology::04.08.06. Volcano monitoring ; 05. General::05.02. Data dissemination::05.02.03. Volcanic eruptions
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  • 4
    Publikationsdatum: 2017-04-04
    Beschreibung: Hydrothermal systems and related vents can exhibit dramatic changes in their physico-chemical conditions over time as a response to varying activity in the feeding magmatic systems. Massive steam condensation and gas scrubbing processes of thermal fluids during their ascent and cooling cause further compositional changes that mask information regarding the conditions evolving at depth in the hydrothermal system. Here we propose a new stability diagram based on the CO2-CH4-CO-H2 concentrations in vapor, which aims at calculating the temperatures and pressures in hydrothermal reservoirs. To filter gas scrubbing effects, we have also developed a model for selective dissolution of CO2-H2S-N2-CH4-He-Ne mixtures in fresh and/or air-saturated seawater. This methodology has been applied to the recent (November 2002) crisis that affected the geothermal field off the island of Panarea (Italy), where the fluid composition and fluxes have been monitored for the past two decades. The chemical and isotopic compositions of the gases suggest that the volatile elements originate from an active magma, which feeds a boiling saline solution having temperatures of up to 350 C and containing 12 mol CO2 in vapor. The thermal fluids undergo cooling and re-equilibration processes on account of gas-water-rock interactions during their ascent along fracture networks. Furthermore, steam condensation and removal of acidic species, partial dissolution in cold air-saturated seawater and stripping of atmospheric components, affect the composition of the geothermal gases at shallow levels. The observed geochemical variations are consistent with a new input of magmatic fluids that perturbed the geothermal system and caused the unrest event. The present-state evolution shows that this dramatic input of fluids is probably over, and that the system is now tending towards steady-state conditions on a time scale of months.
    Beschreibung: Published
    Beschreibung: 3045-3059
    Beschreibung: partially_open
    Schlagwort(e): Submarine degassing ; geothermal system ; gas-water interaction ; gas geothermometry ; 04. Solid Earth::04.01. Earth Interior::04.01.02. Geological and geophysical evidences of deep processes ; 04. Solid Earth::04.08. Volcanology::04.08.01. Gases ; 04. Solid Earth::04.08. Volcanology::04.08.04. Thermodynamics ; 04. Solid Earth::04.08. Volcanology::04.08.06. Volcano monitoring ; 05. General::05.02. Data dissemination::05.02.01. Geochemical data
    Repository-Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
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  • 5
    Publikationsdatum: 2017-04-04
    Beschreibung: The northwestern flank of the Colli Albani, a Quaternary volcanic complex near Rome, is characterised by high CO2 values and Rn activities in the groundwater and by the presence of zones with strong emission of gas from the soil. The most significant of these zones is Cava dei Selci where many houses are located very near to the gas emission site. The emitted gas consists mainly of CO2 (up to 98 vol) with an appreciable content of H2S (0.8). The He and C isotopic composition indicates, as for all fluids associated with the Quaternary Roman and Tuscany volcanic provinces, the presence of an upper mantle component contaminated by crustal fluids associated with subducted sediments and carbonates. An advective CO2 flux of 37 tons/day has been estimated from the gas bubbles rising to the surface in a small drainage ditch and through a stagnant water pool, present in the rainy season in a topographically low central part of the area. A CO2 soil flux survey with an accumulation chamber, carried out in February-March 2000 over a 12 000 m2 surface with 242 measurement points, gave a total (mostly conductive) flux of 61 tons/day. CO2 soil flux values vary by four orders of magnitude over a 160-m distance and by one order of magnitude over several metres. A fixed network of 114 points over 6350 m2 has been installed in order to investigate temporal flux variations. Six surveys carried out from May 2000 to June 2001 have shown large variations of the total CO2 soil flux (8/25 tons/day). The strong emission of CO2 and H2S, which are gases denser than air, produces dangerous accumulations in low areas which have caused a series of lethal accidents to animals and one to a man. The gas hazard near the houses has been assessed by continuously monitoring the CO2 and H2S concentration in the air at 75 cm from the ground by means of two automatic stations. Certain environmental parameters (wind direction and speed; atm P, T, humidity and rainfall) were also continuously recorded. At both stations, H2S and CO2 exceeded by several times the recommended concentration thresholds. The highest CO2 and H2S values were recorded always with wind speeds less than 1.5 m/s, mostly in the night hours. Our results indicate that there is a severe gas hazard for people living near the gas emission site of Cava dei Selci, and appropriate precautionary and prevention measures have been recommended both to residents and local authorities.
    Beschreibung: - GNV funded research project Gas Hazard of Colli Albani
    Beschreibung: Published
    Beschreibung: 81^94
    Beschreibung: partially_open
    Schlagwort(e): Colli Albani ; CO2 flux ; H2S ; gas hazard ; 01. Atmosphere::01.01. Atmosphere::01.01.07. Volcanic effects ; 04. Solid Earth::04.01. Earth Interior::04.01.02. Geological and geophysical evidences of deep processes ; 04. Solid Earth::04.03. Geodesy::04.03.06. Measurements and monitoring ; 04. Solid Earth::04.04. Geology::04.04.12. Fluid Geochemistry ; 04. Solid Earth::04.08. Volcanology::04.08.01. Gases ; 04. Solid Earth::04.08. Volcanology::04.08.02. Experimental volcanism ; 04. Solid Earth::04.08. Volcanology::04.08.06. Volcano monitoring ; 05. General::05.02. Data dissemination::05.02.01. Geochemical data ; 04. Solid Earth::04.08. Volcanology::04.08.08. Volcanic risk
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  • 6
    Publikationsdatum: 2017-04-04
    Beschreibung: Basaltic volcanism is most typically thought to produce effusion of lava, with the most explosive manifestations ranging from mild Strombolian activity to more energetic fire fountain eruptions. However, some basaltic eruptions are now recognized as extremely violent, i.e., generating widespread phreatomagmatic, subplinian and Plinian fall deposits. We focus here on the influence of conduit processes, especially partial open-system degassing, in triggering abrupt changes in style and intensity that occurred during two examples of basaltic Plinian volcanism. We use the 1886 eruption of Tarawera, New Zealand, the youngest known basaltic Plinian eruption and the only one for which there are detailed written eyewitness accounts, and the well-documented 122 BC eruption of Mount Etna, Italy, and present new grain size and vesicularity data from the proximal deposits. These data show that even during extremely powerful basaltic eruptions, conduit processes play a critical role in modifying the form of the eruptions. Even with very high discharge, and presumably ascent, rates, partial open-system behaviour of basaltic melts becomes a critical factor that leads to development of domains of largely stagnant and outgassed melt that restricts the effective radius of the conduit. The exact path taken in the waning stages of the eruptions varied, in response to factors which included conduit geometry, efficiency and extent of outgassing and availability of ground water, but a relatively abrupt cessation to sustained high-intensity discharge was an inevitable consequence of the degassing processes.
    Beschreibung: Published
    Beschreibung: 1-14
    Beschreibung: partially_open
    Schlagwort(e): basaltic Plinian eruption ; Etna ; Tarawera and explosive volcanism ; 04. Solid Earth::04.08. Volcanology::04.08.06. Volcano monitoring ; 05. General::05.02. Data dissemination::05.02.03. Volcanic eruptions
    Repository-Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
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  • 7
    Publikationsdatum: 2017-04-04
    Beschreibung: This survey proposes a new approach to identify buried caldera boundaries of a volcanic cone, combining (1) a systematic elliptic Fourier functions (EFF) analysis on the contour lines based on the external shape of the edifice with (2) self-potential (SP) measurements on volcano flanks. The methodology of this approach is to investigate the relationships between (1) vertical morphological changes inferred from EFF analysis and (2) lateral lithological transition inside the edifice inferred from SP/elevation gradients. The application of these methods on Misti volcano in southern Peru displays a very good correlation. The three main boundaries evidenced by hierarchical cluster analysis on the contour lines coincide with the two main boundaries characterised by SP signal and with a secondary SP signature related with a summit caldera. In order to explain these results showing a very good correlation between morphologic and lithologic changes as function of elevation, caldera boundaries have been suggested. The latter would be located at an average elevation of (1) 4350–4400 m, (2) 4950–5000 m, and (3) 5500– 5550 m. For the lowest boundary in elevation, the coincidence with the lateral extension of the hydrothermal system inferred from SP measurements suggests that caldera walls act as a barrier for lateral extension of hydrothermal systems. In the summit area, the highest boundary has been related with the summit caldera, inferred by a secondary SP minimum and geological evidence.
    Beschreibung: - Institut de Recherche pour le Développement (IRD) - Instituto Geofisico del Peru´ (IGP).
    Beschreibung: Published
    Beschreibung: 283– 297
    Beschreibung: partially_open
    Schlagwort(e): caldera ; elliptic Fourier functions ; geomorphology ; self-potential ; Misti volcano ; Peru ; 03. Hydrosphere::03.02. Hydrology::03.02.02. Hydrological processes: interaction, transport, dynamics ; 03. Hydrosphere::03.02. Hydrology::03.02.03. Groundwater processes ; 03. Hydrosphere::03.02. Hydrology::03.02.04. Measurements and monitoring ; 03. Hydrosphere::03.04. Chemical and biological::03.04.05. Gases ; 03. Hydrosphere::03.04. Chemical and biological::03.04.06. Hydrothermal systems ; 04. Solid Earth::04.01. Earth Interior::04.01.02. Geological and geophysical evidences of deep processes ; 04. Solid Earth::04.02. Exploration geophysics::04.02.04. Magnetic and electrical methods ; 04. Solid Earth::04.04. Geology::04.04.03. Geomorphology ; 04. Solid Earth::04.04. Geology::04.04.09. Structural geology ; 04. Solid Earth::04.04. Geology::04.04.11. Instruments and techniques ; 04. Solid Earth::04.08. Volcanology::04.08.05. Volcanic rocks ; 05. General::05.02. Data dissemination::05.02.04. Hydrogeological data ; 05. General::05.05. Mathematical geophysics::05.05.99. General or miscellaneous ; 05. General::05.08. Risk::05.08.99. General or miscellaneous ; 04. Solid Earth::04.08. Volcanology::04.08.08. Volcanic risk
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  • 8
    Publikationsdatum: 2017-04-04
    Beschreibung: Mount Etna produced two significant eruptions in 2001 and 2002–2003, which we have analysed using geological, seismic and deformation data. These eruptions showed some similarities, such as the activating of two magmatic plumbing systems (central–lateral and eccentric), but they differed in their triggering mechanisms. While the 2001 eruption was largely the result of the emplacement of a N–S eccentric dike (independent from the central conduits) consistent with E–W regional extension, the 2002–2003 eruption occurred in response to a major flank slip on the eastern and southeastern sides of the volcano. This is demonstrated by the spatial and temporal distribution of seismicity and deformation preceding and accompanying the two eruptions. During the months prior to the 2001 eruption, most epicenters were concentrated on the southern flank, at depths of 5–15 km below sea level. During the 4 days before the eruption, earthquake hypocenters migrated to shallower levels (from 5 km bsl. upward) indicating the emplacement of the eccentric dike. This is confirmed by the patterns of ground fracturing observed in the field and deformation documented by electronic distance measurements (EDM). In contrast, the months before the 2002–2003 eruption were characterised by shallower seismicity, mainly concentrated along the active faults bordering the slipping flank sector. Flank slip accelerated in September 2002 and a second, more vigorous acceleration of flank slip occurred on 26–27 October 2002, accompanying the opening of eruptive vents. The very short (2 h) seismic crisis preceding the onset of eruptive activity stands in neat contrast with the 4 days of intense seismicity before the 2001 eruption. Subsequently, flank slip-deformation extended all over the eastern and southeastern flanks of the volcano, causing serious damage in this sector. The events of 2001–2003 can be seen as a continuous chain of intimately interacting processes including regional tectonics, magma accumulation and eruption, and flank instability. In this scenario the 2001 eruption led to increased flank instability that subsequently accelerated and culminated with the massive flank slip, which in turn facilitated the 2002–2003 eruption. This sequence of events points to a long-term feedback mechanism between magmatism and flank instability at Etna.
    Beschreibung: Published
    Beschreibung: 235-255
    Beschreibung: partially_open
    Schlagwort(e): eruption triggering ; central–lateral vs. eccentric eruptions ; flank instability and slip ; volcano-tectonics ; Mt. Etna ; instrumental monitoring ; 04. Solid Earth::04.07. Tectonophysics::04.07.07. Tectonics ; 04. Solid Earth::04.08. Volcanology::04.08.06. Volcano monitoring ; 05. General::05.02. Data dissemination::05.02.03. Volcanic eruptions ; 04. Solid Earth::04.08. Volcanology::04.08.08. Volcanic risk
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  • 9
    Publikationsdatum: 2017-04-04
    Beschreibung: The evolution of scaling characteristics of the local geomagnetic field and of the seismicity at Etna volcano is studied in relation to the strong eruptive activity occurred here from 2000 to 2002. Scaling laws are found in the hourly time variability of magnetic data and in the seismicity pattern. The scaling exponents suggest the presence of persistent temporal fluctuations. Clear links between the dynamics of the measured data and the eruptive volcanic episodes are revealed. Fractal dimensions of seismicity seem to be always correlated to the beginning of main eruptive events, while strong alterations of the dynamics of the local magnetic field take place only when the eruptive fractures opened very close to the magnetic sites.
    Beschreibung: Published
    Beschreibung: 96-106
    Beschreibung: partially_open
    Schlagwort(e): scaling characteristics ; volcanic eruptions ; geomagnetic field ; seismic activity ; Mt. Etna ; 04. Solid Earth::04.05. Geomagnetism::04.05.02. Geomagnetic field variations and reversals ; 05. General::05.02. Data dissemination::05.02.03. Volcanic eruptions
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