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  • Nicaragua  (3)
  • Caldera 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
    Eruption and emplacement of a basaltic welded ignimbrite during caldera formation on Gran Canaria (1995)
    Springer
    Bulletin of volcanology 56 (1995), S. 640-659 
    Details
    ISSN: 1432-0819
    Keywords: Key words Basaltic ignimbrite ; Lava-drop coalescence ; Welding ; Pyroclastic fountain ; Caldera collapse ; Gran Canaria
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Notes: Abstract  The 14.1 Ma old composite ignimbrite cooling unit P1 (45 km3) on Gran Canaria comprises a lower mixed rhyolite–trachyte tuff, a central rhyolite–basalt mixed tuff, and a slightly rhyolite-contaminated basaltic tuff at the top. The basaltic tuff is compositionally zoned with (a) an upward change in basalt composition to higher MgO content (4.3–5.2 wt.%), (b) variably admixed rhyolite or trachyte (commonly 〈5 wt.%), and (c) an upward increasing abundance of basaltic and plutonic lithic fragments and cognate cumulate fragments. The basaltic tuff is divided into three structural units: (I) the welded basaltic ignimbrite, which forms the thickest part (c. 95 vol.%) and is the main subject of the present paper; (II) poorly consolidated massive, bomb- and block-rich beds interpreted as phreatomagmatic pyroclastic flow deposits; and (III) various facies of reworked basaltic tuff. Tuff unit I is a basaltic ignimbrite rather than a lava flow because of the absence of top and bottom breccias, radial sheet-like distribution around the central Tejeda caldera, thickening in valleys but also covering higher ground, and local erosion of the underlying P1 ash. A gradual transition from dense rock in the interior to ash at the top of the basaltic ignimbrite reflects a decrease in welding; the shape of the welding profile is typical for emplacement temperatures well above the minimum welding temperature. A similar transition occurs at the base where the ignimbrite was emplaced on cold ground in distal sections. In proximal sections the base is dense where it was emplaced on hot felsic P1 tuff. The intensity of welding, especially at the base, and the presence of spherical particles and of mantled and composite particles formed by accretion and coalescence in a viscous state imply that the flow was a suspension of hot magma droplets. The flow most likely had to be density stratified and highly turbulent to prevent massive coalescence and collapse. Model calculations suggest eruption through low pyroclastic fountains (〈1000 m high) with limited cooling during eruption and turbulent flow from an initial temperature of 1160°  C. The large volume of 26 km3 of erupted basalt compared with only 16 km3 of the evolved P1 magmas, and the extremely high discharge rates inferred from model calculations are unusual for a basaltic eruption. It is suggested that the basaltic magma was erupted and emplaced in a fashion commonly only attributed to felsic magmas because it utilized the felsic P1 magma chamber and its ring-fissure conduits. Evolution of the entire P1 eruption was controlled by withdrawal dynamics involving magmas differing in viscosity by more than four orders of magnitude. The basaltic eruption phase was initially driven by buoyancy of the basaltic magma at chamber depth and continued degassing of felsic magma, but most of the large volume of basalt magma was driven out of the reservoir by subsidence of a c. 10 km diameter roof block, which followed a decrease in magma chamber pressure during low viscosity basaltic outflow.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00301468
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