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  • 1
    Online Resource
    Online Resource
    Meteorological influence on the seasonal and diurnal variability of the dispersion of volcanic emissions in Nicaragua : a numerical model study (2009)
    Associated volumes
    Details Availability
    In: Journal of volcanology and geothermal research, Amsterdam [u.a.] : Elsevier Science, 1976, 182(2009), 1/2, Seite 34-44, 0377-0273
    In: volume:182
    In: year:2009
    In: number:1/2
    In: pages:34-44
    Description / Table of Contents: Nicaragua comprises seven historically active volcanoes (Cosigüina, San Cristobal, Telica, Cerro Negro, Momotombo, Masaya, and Concepcion), five of which are in a state of continuous degassing. Published measurements of the atmospheric dispersion of continuous emissions from Nicaraguan volcanoes, the chemical and aerosol microphysical modifications of the released gases and aerosols, and related acid deposition and impacts on the environment cover only short periods of time. We applied a three-dimensional atmosphere-chemistry/aerosol numerical model over Central America focussing on Nicaraguan volcanic emissions for month long simulation periods during the dry and wet seasons of 2003. The model is able to reproduce observed monthly precipitation and wind speed throughout the year 2003. Model results for near surface SO2 concentrations and SO2 dry deposition fluxes around Masaya volcano are in very good agreement with field measurements. During the dry season, oxidation of SO2 to sulphate plays only a minor role downwind of the Nicaraguan volcanoes and over the Pacific Ocean, whereas SO2 released from Arenal and Poas in Costa Rica is oxidised to sulphate much faster and closer to the volcanoes due to higher humidity and cloud water availability. During the wet season, more variable wind conditions lead to reduced dispersion of SO2 over the Pacific Ocean and increased dispersion inland. The availability of liquid water in the atmosphere favours sulphate formation close to the Nicaraguan volcanoes via aqueous phase oxidation and represents another limitation for the dispersion of SO2. Strong precipitation removes sulphate quickly from the atmosphere by wet deposition. Atmospheric SO2 concentrations and in particular dry deposition close to the volcanoes show a pronounced diurnal cycle.
    Type of Medium: Online Resource
    Pages: graph. Darst
    ISSN: 0377-0273
    DOI: 10.1016/j.jvolgeores.2009.01.031
    Language: English
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  • 2
    Online Resource
    Online Resource
    Eruption dynamics during Plinian eruptions : insights from the stratigraphic variations of deposit structures und pumice textures of the Minoan eruption (Santorini, Greece) and the Laacher See eruption /East Eifel, Germany) (2003)
    Details Availability
    Keywords: Hochschulschrift ; Laacher See Region ; Eruption
    Description / Table of Contents: Abstract ; Zs.-Fassung
    Type of Medium: Online Resource
    Pages: Online-Ressource (95, [54] Bl. = 3.94 MB, Text) , Ill., graph. Darst., Kt
    Edition: [Electronic ed.]
    URL: http://eldiss.uni-kiel.de/macau/receive/dissertation_diss_1227
    URL: http://nbn-resolving.de/urn:nbn:de:gbv:8-diss-12275
    URN: urn:nbn:de:gbv:8-diss-12275
    Language: English
    Note: Kiel, Univ., Diss., 2004
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  • 3
    Electronic Resource
    Electronic Resource
    Widespread fluid expulsion along the seafloor of the Costa Rica convergent margin (2002)
    Oxford UK : Blackwell Science Ltd
    Terra nova 14 (2002), S. 0 
    Details
    ISSN: 1365-3121
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Geosciences
    Notes: Active fluid and gas transport were measured and observed along more than 200 km of the convergent margin of Costa Rica during cruise SO144-2 aboard RV Sonne. Ten profiles were run with the TV-sled OFOS, eight of which detected the dense occurrence of cold vent sites. This discovery shows that seafloor fluid expulsion is widely spread along the Pacific margin of Costa Rica. Surficial evidence of fluid expulsion is indicated by the appearance of chemosynthetic vent organisms such as bacterial mats, vesicomyid, solemyid and mytilid bivalves and tubeworms. Numerous active vents were indicated by elevated methane concentrations (≤ 200 nmol L–) in the bottom water. Although fluid-venting activity was known previously from a small area south of Nicoya Peninsula, the present study documents active seepage at landslides, headwall scarps related to seamount subduction, morphological intersections of faults and mid-slope mud volcanoes.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-3121.2002.00400.x
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    Paper (German National Licenses)
    Fulltext
  • 4
    Electronic Resource
    Electronic Resource
    Igneous layering through oscillatory nucleation and crystal settling in well-mixed magmas (1993)
    Springer
    Contributions to mineralogy and petrology 114 (1993), S. 425-440 
    Details
    ISSN: 1432-0967
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Notes: Abstract Oscillatory or competitive nucleation about a binary (or perhaps pseudo binary) eutectic and ensuing crystal growth and settling is a commonly suggested means of producing layering in magmatic systems. A quantitative model is presented of this, outwardly, relatively simple process of crystal nucleation, growth, and settling in an otherwise initially crystal-free magma. Avrami-style kinetics of crystallization in an always wellmixed body, buried in conductive wall rock, are coupled to a Stokes-like formulation of crystal settling in magma whose viscosity depends on temperature and crystallinity. Two dimensionless numbers (Se, the settling number and Av, the Avrami or kinetic number) govern all the results. Av and Se measure the relative importance of crystallization time and settling time, respectively, relative to the overall cooling time. For any value of Av, which increases strongly with the maximum nucleation and growth rates and cooling time, layering is possible only over a range or window of values of Se. Both above and below this window a single layer (crystalline below, vitric above) forms, and within this window the number of layers increases systematically with increasing Av and Se. Grain size within any single layer generally coarsens upward. Because the characteristic settling and cooling times both depend on body thickness, the lower limit of the settling window is also dependent on sheet thickness. Within the confines of this model and for nucleation and growth rates set by those observed in natural systems, layering is unlikely in sheet-like magmas thinner than about 100 m. When the body is not always well-mixed and crystallization is within inward-propagating solidification fronts, it is expected that this minimum body thickness will increase.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00321748
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  • 5
    Electronic Resource
    Electronic Resource
    Continuous monitoring of volcanic eruption dynamics: a review of various techniques and new results from a frequency-modulated radar Doppler system (1999)
    Springer
    Bulletin of volcanology 60 (1999), S. 627-639 
    Details
    ISSN: 1432-0819
    Keywords: Key words Eruption velocity ; Stromboli ; Monitoring ; Radar ; Doppler technique
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Notes: Abstract  In situ measurement of volcanic eruption velocities is one of the great challenges left in geophysical volcanology. In this paper we report on a new radar Doppler technique for monitoring volcanic eruption velocities. In comparison with techniques employed previously (e.g., photographic methods or acoustic Doppler measurements), this method allows continuous recordings of volcanic eruptions even during poor visibility. Also, radar Doppler instruments are usually light weight and energy efficient, which makes them superior to other Doppler techniques based on laser light or sound. The proposed new technique was successfully tested at Stromboli Volcano in late 1996 during a period of low activity. The recorded data allow a clear distinction between particles rising from the vent and particles falling back towards the vent. The mean eruption velocity was approximately 10 m/s. Most of the eruptions recorded by radar were correlated to seismic recordings. The correlation between the magnitude of the volcanic shocks and the eruption force index defined in the paper may provide new insights into magma transport in the conduit.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004450050256
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  • 6
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    An adaptive semi-Lagrangian advection model for transport of volcanic emissions in the atmosphere (2018)
    Copernicus Publications (EGU)
    In:  Natural Hazards and Earth System Sciences, 18 (5). pp. 1517-1534.
    Details
    Publication Date: 2018-12-17
    Description: The dispersion of volcanic emissions in the Earth atmosphere is of interest for climate research, air traffic control and human wellbeing. Current volcanic emission dispersion models rely on fixed-grid structures that often are not able to resolve the fine filamented structure of volcanic emissions being transported in the atmosphere. Here we extend an existing adaptive semi-Lagrangian advection model for volcanic emissions including the sedimentation of volcanic ash. The advection of volcanic emissions is driven by a precalculated wind field. For evaluation of the model, the explosive eruption of Mount Pinatubo in June 1991 is chosen, which was one of the largest eruptions in the 20th century. We compare our simulations of the climactic eruption on 15 June 1991 to satellite data of the Pinatubo ash cloud and evaluate different sets of input parameters. We could reproduce the general advection of the Pinatubo ash cloud and, owing to the adaptive mesh, simulations could be performed at a high local resolution while minimizing computational cost. Differences to the observed ash cloud are attributed to uncertainties in the input parameters and the course of Typhoon Yunya, which is probably not completely resolved in the wind data used to drive the model. The best results were achieved for simulations with multiple ash particle sizes.
    Type: Article , PeerReviewed
    Format: text
    DOI: 10.5194/nhess-18-1517-2018
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    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 7
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    Meteorological influence on the seasonal and diurnal variability of the dispersion of volcanic emissions in Nicaraguan: a numerical model study (2009)
    In:  [Other] In: 69. Jahrestagung der Deutschen Geophysikalischen Gesellschaft (DGG), 23.03.-26.03.2009, Kiel . 69. Jahrestagung der Deutschen Geophysikalischen Gesellschaft in Kiel : 23.-26. März 2009 ; p. 92 .
    Details
    Publication Date: 2012-02-23
    Type: Conference or Workshop Item , NonPeerReviewed
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  • 8
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    Meteorological influence on the seasonal and diurnal variability of the dispersion of volcanic emissions in Nicaragua: a numerical model (2009)
    Elsevier
    In:  Journal of Volcanology and Geothermal Research, 182 (1/2). pp. 34-44.
    Details
    Publication Date: 2017-08-08
    Description: Nicaragua comprises seven historically active volcanoes (Cosigüina, San Cristobal, Telica, Cerro Negro, Momotombo, Masaya, and Concepcion), five of which are in a state of continuous degassing. Published measurements of the atmospheric dispersion of continuous emissions from Nicaraguan volcanoes, the chemical and aerosol microphysical modifications of the released gases and aerosols, and related acid deposition and impacts on the environment cover only short periods of time. We applied a three-dimensional atmosphere-chemistry/aerosol numerical model over Central America focussing on Nicaraguan volcanic emissions for month long simulation periods during the dry and wet seasons of 2003. The model is able to reproduce observed monthly precipitation and wind speed throughout the year 2003. Model results for near surface SO2 concentrations and SO2 dry deposition fluxes around Masaya volcano are in very good agreement with field measurements. During the dry season, oxidation of SO2 to sulphate plays only a minor role downwind of the Nicaraguan volcanoes and over the Pacific Ocean, whereas SO2 released from Arenal and Poas in Costa Rica is oxidised to sulphate much faster and closer to the volcanoes due to higher humidity and cloud water availability. During the wet season, more variable wind conditions lead to reduced dispersion of SO2 over the Pacific Ocean and increased dispersion inland. The availability of liquid water in the atmosphere favours sulphate formation close to the Nicaraguan volcanoes via aqueous phase oxidation and represents another limitation for the dispersion of SO2. Strong precipitation removes sulphate quickly from the atmosphere by wet deposition. Atmospheric SO2 concentrations and in particular dry deposition close to the volcanoes show a pronounced diurnal cycle.
    Type: Article , PeerReviewed
    Format: text
    DOI: 10.1016/j.jvolgeores.2009.01.031
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    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 9
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    2D and 3D numerical models on compositionally buoyant diapirs in the mantle wedge (2011)
    Elsevier
    In:  Earth and Planetary Science Letters, 311 (1-2). pp. 53-68.
    Details
    Publication Date: 2019-02-01
    Description: We present 2D and 3D numerical model calculations that focus on the physics of compositionally buoyant diapirs rising within a mantle wedge corner flow. Compositional buoyancy is assumed to arise from slab dehydration during which water-rich volatiles enter the mantle wedge and form a wet, less dense boundary layer on top of the slab. Slab dehydration is prescribed to occur in the 80–180 km deep slab interval, and the water transport is treated as a diffusion-like process. In this study, the mantle's rheology is modeled as being isoviscous for the benefit of easier-to-interpret feedbacks between water migration and buoyant viscous flow of the mantle. We use a simple subduction geometry that does not change during the numerical calculation. In a large set of 2D calculations we have identified that five different flow regimes can form, in which the position, number, and formation time of the diapirs vary as a function of four parameters: subduction angle, subduction rate, water diffusivity (mobility), and mantle viscosity. Using the same numerical method and numerical resolution we also conducted a suite of 3D calculations for 16 selected parameter combinations. Comparing the 2D and 3D results for the same model parameters reveals that the 2D models can only give limited insights into the inherently 3D problem of mantle wedge diapirism. While often correctly predicting the position and onset time of the first diapir(s), the 2D models fail to capture the dynamics of diapir ascent as well as the formation of secondary diapirs that result from boundary layer perturbations caused by previous diapirs. Of greatest importance for physically correct results is the numerical resolution in the region where diapirs nucleate, which must be high enough to accurately capture the growth of the thin wet boundary layer on top of the slab and, subsequently, the formation, morphology, and ascent of diapirs. Here 2D models can be very useful to quantify the required resolution, which we find for a 1019 Pa · s mantle wedge to be about 1 km node spacing for quadratic-order velocity elements.
    Type: Article , PeerReviewed
    Format: text
    DOI: 10.1016/j.epsl.2011.08.043
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  • 10
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    Radar Doppler velocity of volcanic eruptions: Theoretical considerations and quantitative documentation of changes in eruptive behaviour at Stromboli volcano, Italy (2003)
    Wiley
    In:  Geophysical Journal International, 154 (2). pp. 515-532.
    Details
    Publication Date: 2018-07-17
    Description: The use of radar Doppler velocimetry for the observation of volcanic activity is new. We used this method to continuously observe the activity of one vent of Stromboli volcano, Italy, from the end of 2000 April until early May. During this period we recorded 702 eruptions, 132 of which occurred before a strong rain storm passed over the island on April 29. In order to interpret the recorded Doppler data we developed a program that simulates different strombolian eruption scenarios, for which we then calculate the theoretical Doppler spectra. Comparing our theoretical data with the observed data we are able to show that most of the eruptions are nearly vertical, although we did observe only one component of the eruption vector with our Doppler radar. One of the most interesting features of the data set is a significant change in eruptive behaviour that correlates with the occurrence of the rain storm: we find that on average the eruption duration increased by a factor of 2, eruptive velocities were much higher and indirect evidence indicates that the average particle diameter of the erupted material decreased. This change may have several causes, but the coincidence with the rain storm may be evidence of magma–water interaction and feedback on the volcanic activity. If the fluid source (rain) changing the eruptive style is at the surface and in near-surface layers then the main control on final eruption dynamics at Stromboli volcano must also be in rather shallow regions.
    Type: Article , PeerReviewed
    Format: text
    DOI: 10.1046/j.1365-246X.2003.01982.x
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    OceanRep: Article in a Scientific Journal - peer-reviewed
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