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  • Nicaragua  (3)
  • Column collapse  (1)
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  • 1
    Online Resource
    Online Resource
    Volatile degassing and plinian eruption dynamics of the mafic Fontana Tephra, Nicaragua (2005)
    Details Availability
    Keywords: Hochschulschrift ; Nicaragua ; Tephra ; Jungpleistozän ; Eruption
    Description / Table of Contents: Abstract ; Zs.-Fassung
    Type of Medium: Online Resource
    Pages: Online-Ressource (X, 113 S. = 1.44 MB, Text) , Ill., graph. Darst., Kt
    Edition: [Electronic ed.]
    URL: http://eldiss.uni-kiel.de/macau/receive/dissertation_diss_1424
    URL: http://nbn-resolving.de/urn:nbn:de:gbv:8-diss-14240
    URN: urn:nbn:de:gbv:8-diss-14240
    Language: English
    Note: Enth. Zeitschriftenaufsätze , Kiel, Univ., Diss., 2005
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  • 2
    Online Resource
    Online Resource
    Basaltic Plinian and violent Surtseyan eruptions from the Masaya Caldera Complex, Nicaragua (2007)
    Kiel
    Details Availability
    Keywords: Hochschulschrift ; Nicaragua ; Vulkanismus
    Type of Medium: Online Resource
    Pages: 1 Online-Ressource ( 209Seiten = 27MB) , zahlr. Ill., graph. Darst., Kt.
    URL: https://oceanrep.geomar.de/id/eprint/3843/
    Language: English , German
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  • 3
    Online Resource
    Online Resource
    Basaltic Plinian and violent Surtseyan eruptions from the Masaya Caldera Complex, Nicaragua (2007)
    Details Availability
    Keywords: Hochschulschrift ; Nicaragua ; Vulkanismus
    Description / Table of Contents: The Masaya caldera complex in central-western Nicaragua consists of a 6x11 km, 〉150 m deep, oval caldera that hosts a cluster of intra-caldera cinder cones. Subsidence of the Masaya caldera was caused by highly explosive Plinian, Phreatoplinian and violent Surtseyan basaltic eruptions during the last 6,000 years. The first eruption at ~6 ka produced the 14 km3 San Antonio Tephra (SAT). The second eruption at 2.1 ka generated two deposit facies distinct in internal architecture and direction of distribution: La Concepción Tephra (LCT) and Masaya Triple Layer (MTL), with a combined tephra volume is 3.6 km3. The third eruption at ~1.8 ka formed the Masaya Tuff (MT) and the directly overlying Ticuantepe Lapilli (TIL), totalling 10 km3. Basaltic Plinian eruptions are generally considered as exotic events but are common at Masaya. Water contents of 〈3.4 wt% measured in melt inclusions are moderate and cannot explain this eruptive behavior which is rather discussed in terms degassing dynamics in the conduit, by access of external water. Central western Nicaragua is highly vulnerable for volcanic disasters, because it has the highest population density of the country, comprising the large cities of Managua, Granada and Masaya, and the principal lifelines. A risk analysis for the main population centers around the Masaya caldera shows that, in case of a similar eruption today, the most vulnerable communities would be Ticuantepe, Nindirí and Masaya. In addition, La Concepción southwest of the caldera, and the capital Managua, more than 15 km to the northwest, could be affected.
    Type of Medium: Online Resource
    Pages: Online-Ressource (PDF-Datei: 195 S., 26.31 MB) , zahlr. Ill., graph. Darst., Kt.
    URL: http://nbn-resolving.de/urn:nbn:de:gbv:8-diss-20637
    URL: http://eldiss.uni-kiel.de/macau/receive/dissertation_diss_2063
    URL: http://d-nb.info/1019552913/34
    URN: urn:nbn:de:gbv:8-diss-20637
    DDC: 550
    Language: English , German
    Note: Kiel, Univ., Diss., 2007
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  • 4
    Electronic Resource
    Electronic Resource
    Formation of high-grade ignimbrites Part II. A pyroclastic suspension current model with implications also for low-grade ignimbrites (1999)
    Springer
    Bulletin of volcanology 60 (1999), S. 545-567 
    Details
    ISSN: 1432-0819
    Keywords: Key words Ignimbrite ; Pyroclastic suspension current ; Column collapse ; Physical modeling ; Welding ; Particle aggregation ; Co-ignimbrite ash
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Notes: Abstract  Analogue experiments in part I led to the conclusion that pyroclastic flows depositing very high-grade ignimbrite move as dilute suspension currents. In the thermo–fluid–dynamical model developed, the degree of cooling of expanded turbulent pyroclastic flows dynamically evolves in response to entrainment of air and mass loss to sedimentation. Initial conditions of the currents are derived from column-collapse modeling for magmas with an initial H2O content of 1–3 wt.% erupting through circular vents and caldera ring-fissures. The flows spread either longitudinally or radially from source up to a runout distance that increases with higher mass flux but decreases with higher gas content, temperature, bottom slope and coarser initial grain size. Progressive dilution by entrainment and sedimentation causes pyroclastic currents to transform into buoyant ash plumes at the runout distance. The ash plumes reach stratospheric heights and distribute 30–80% of the erupted material as widespread co-ignimbrite ash. Pyroclastic suspension currents with initial mass fluxes of 107-1012 kg/s can spread for tens of kilometers with only limited cooling, although they move as supercritical, strongly entraining currents for the eruption conditions considered here. With increasing eruption mass flux, cooling during passage through the fountain diminishes while cooling during flow transport increases. The net effect is that eruption temperature exerts the prime control on emplacement temperature. Pyroclastic suspension currents can form welded ignimbrite across their entire extent if eruption temperature is To〉1.3.Tmw, the minimum welding temperature. High eruption rates, a large fraction of fine ash, and a ring-fissure vent favor the formation of extensive high-grade ignimbrite. For very hot eruptions producing sticky, partially molten pyroclasts, analysis of particle aggregation systematics shows that factors favoring longer runout also favor more efficient aggregation, which reduces runout. As a result, very high-grade ignimbrites cannot spread more than a few tens of kilometers from their source. In cooler pyroclastic currents, particles do not aggregate, and the sedimentation process may involve re-entrainment of particles, which potentially leads to more extensive cooling and longer runout; such effects, however, are only significant when net erosion of substrate occurs. Model results can be employed to estimate mass flux and duration of ignimbrite eruptions from measured ignimbrite masses and aspect ratios. The model also provides an alternative explanation of the observed decrease in H/Lratios with ignimbrite mass.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004450050251
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