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  • 1
    Electronic Resource
    Electronic Resource
    The Green Tuff of Pantelleria: Rheoignimbrite or rheomorphic fall? (1984)
    Springer
    Bulletin of volcanology 47 (1984), S. 611-626 
    Details
    ISSN: 1432-0819
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Notes: Abstract Detailed stratigraphic analysis of the Green Tuff of Pantelleria shows that this formation can be divided into several members designateda throughh from base to top. These members have a coherent pattern when traced from outcrop to outcrop throughout the island shedding light on their origin. Only memberg completely mantles the entire island. The distribution of the other members is controlled by prevailing wind direction or by topography. Membera is entirely of fall origin. Membersc ande are of fall and/or surge type. Membersb,d, andh have the characteristics of thin welded ash-flow tuffs. Membersf andg are ash-flow tuffs with textural characteristics of compound cooling units. Most of the ash-flow tuffs exhibit characteristics of ignimbrites: vertical fluidization pipes, local concentrations of lithic lapilli, imbrication of clasts, and valley ponding. Memberg is unusual in that it is highly-welded, exhibits large-scale rheomorphic structures, contains huge lithic clasts, and has near-vertical foliation where it adheres to cliffs and caldera walls. Granulometric data from the members identified in the field as ignimbrites confirms this conclusion, as do density profiles through the various members.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01961230
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  • 2
    Electronic Resource
    Electronic Resource
    Reappraisal of the 1982 eruptions of El Chichón Volcano, Chiapas, Mexico: new data from proximal deposits (1997)
    Springer
    Bulletin of volcanology 58 (1997), S. 459-471 
    Details
    ISSN: 1432-0819
    Keywords: Key words Mexican Active Volcanoes ; Chichon Volcano ; Phreatomagmatic eruptions ; Wet and dry surge deposits
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Notes: Abstract  Additional data from proximal areas enable a reconstruction of the stratigraphy and the eruptive chronology of phases III and IV of the 1982 eruption of El Chichón Volcano. Phase III began on 4 April at 0135 GMT with a powerful hydromagmatic explosion that generated radially fast-moving (∼100 ms–1) pyroclastic clouds that produced a surge deposit (S1). Due to the sudden reduction in the confining pressure the process continued by tapping of magma from a deeper source, causing a new explosion. The ejected juvenile material mixed with large amounts of fragmented dome and wall rock, which were dispersed laterally in several pulses as lithic-rich block-and-ash flow (F1). Partial evacuation of juvenile material from the magmatic system prompted the entrance of external water to generate a series of hydromagmatic explosions that dispersed moisture-rich surge clouds and small-volume block-and-ash flows (IU) up to distances of 3 km from the crater. The eruption continued by further decompression of the magmatic system, with the ensuing emission of smaller amounts of gas-rich magma which, with the strong erosion of the volcanic conduit, formed a lithic-rich Plinian column that deposited fallout layer B. Associated with the widening of the vent, an increase in the effective density of the uprising column took place, causing its collapse. Block-and-ash flows arising from the column collapse traveled along valleys as a dense laminar flow (F2). In some places, flow regime changes due to topographic obstacles promoted transformation into a turbulent surge (S2) which attained minimum velocities of approximately 77 ms–1 near the volcano. The process continued with the formation of a new column on 4 April at 1135 GMT (phase IV) that emplaced fall deposit C and was followed by hydromagmatic explosions which produced pyroclastic surges (S3).
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004450050155
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  • 3
    Electronic Resource
    Electronic Resource
    A model for Plinian eruptions of Vesuvius (1981)
    [s.l.] : Nature Publishing Group
    Nature 289 (1981), S. 282-285 
    Details
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] Three representative sections from archaeological excavationsdemonstrate the principal characteristics of the entire eruptive sequence, assuming emplacement of pyroclastic flows, surges and lahars above the pumice bed, during the 30-h eruptive period. Data from more than 30 sections included in the ...
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1038/289282a0
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  • 4
    Electronic Resource
    Electronic Resource
    The petrogenesis of topaz rhyolites from the western United States (1983)
    Springer
    Contributions to mineralogy and petrology 83 (1983), S. 16-30 
    Details
    ISSN: 1432-0967
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Notes: Abstract High-silica topaz-bearing rhyolites of Cenozoic age are widely distributed across the western USA and Mexico. They are characteristically enriched in fluorine (〉0.2 wt.%) and incompatible lithophile elements (e.g. Li, Rb, Cs, U, Th, Be). In addition to topaz, the rhyolites contain garnet, bixbyite, pseudobrookite, hematite and fluorite in cavities or in their devitrified groundmasses. Magmatic phases include sanidine, quartz, oligoclase and Fe-rich biotite. Allanite, fluorite, zircon, apatite and magnetite occur in most; pyroxene, hornblende, ilmenite and titanite occur in some. The rhyolites crystallized over a wide temperature interval (850° to 600° C) at $$f_{0_2 } $$ that ranges from QFM to NNO. The REE patterns of most topaz rhyolites are almost flat (La/YbN=1 to 3) and have deep Eu anomalies (Eu/Eu*=0.01 to 0.02). Both parameters decrease with differentiation. Titanite-bearing rhyolites have prominent middle REE depletions. Topaz rhyolites appear to have evolved from partial melts of a residual granulitic source in the Precambrian lower crust. According to the proposed model, the passage of hot mafic magmas through the crust produced partial melts as a result of the decomposition of F-rich biotite or amphibole. An extensional tectonic setting allowed these small batches of magma to rise without substantial mixing with contemporaneous mafic magmas. Some of the compositional differences between topaz rhyolites and peralkaline rhyolites may be attributed to the accumulation of fluorine and fluorphile elements (Al, Be, Li, Rb, U, Th, HREE) in melts which give rise to topaz rhyolites and chlorine and chlorophile elements (Ti, Fe, Mn, Zn, Zr, Nb and LREE) in melts which yield peralkaline rhyolites. Hence the F/Cl ratio of the melt or its source may determine the alumina saturation of the magma series. Topaz rhyolites are distinguishable from calc-alkaline rhyolites by lower Sr, Ba, Eu and higher F, Rb, U and Th. The usually low La/Yb ratios of topaz rhyolites distinguish them from both peralkaline and calc-alkaline rhyolite suites.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00373075
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  • 5
    Electronic Resource
    Electronic Resource
    Volcanic hazards at Fossa of Vulcano: Data from the last 6,000 years (1984)
    Springer
    Bulletin of volcanology 47 (1984), S. 105-124 
    Details
    ISSN: 1432-0819
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Notes: Abstract Stratigraphic reconstruction of the complete sequence of deposits that formed the Fossa cone of Vulcano has distinguished four principal eruptive cycles: Punte Nere, Palizzi, Commenda, and Pietre Cotte. At least three additional eruptive cycles, one of which ends with the Campo Sportivo lava, occur between deposits of the Punte Nere and Palizzi cycles. However, exposure is inadequate for their characterization. The assignment of the modern deposits that follow the Pietre Cotte lava is uncertain. Deposits of each cycle follow a similar stochastic pattern that is controlled by a decrease in the effect of water/melt interaction. The normal sequence of pyroclastic products for each cycle starts with wet-surge beds, followed by dry-surge horizons, fall deposits, and finally lava flows. Absolute age determinations have been made on each cycle-ending lava flow. Wet-surge deposits normally occur near the crater rim, whereas dry-surge deposits are more widespread, reaching the surrounding caldera wall in many places. Thick fall deposits are confined to a zone extending about 800 m from the crater rim. Lava flows normally reach the base of the cone. The greatest hazard at Fossa is related to surge eruptions. The thickness of dry-surge deposits on the flanks of the cone increases away from the crater, but they pinch out toward the source near the crater rim. SEM analysis of the surface textures of juvenile glass clasts from dry-surge deposits confirms that the dominant control on the eruptive mechanism is water/melt interaction. Only slight modifications are induced on grain surfaces during transport. Particles from the Palizzi dry-surge beds lack surface textures characteristic of fall pyroclasts which suggests that ballistic fragments were not incorporated into the dense portion of the turbulent surge cloud. A quantitative analysis of the dispersal of products from the Palizzi cycle allowed creation of a computer-generated map for this eruption.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01960543
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  • 6
    Electronic Resource
    Electronic Resource
    Volcanic history of El Chichón Volcano (Chiapas, Mexico) during the Holocene, and its impact on human activity (2000)
    Springer
    Bulletin of volcanology 62 (2000), S. 90-104 
    Details
    ISSN: 1432-0819
    Keywords: Stratigraphy ; Evolution ; El Chichón ; México
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Notes: 2 abundance and depletion in MgO, CaO, TiO2, as well as trace and rare earth elements. This suggests segregation of olivine and orthopyroxene from the melt. Since human settlements in southeast Mexico and Central America can be traced as far back as approximately 2500 years BP, most of these events probably affected human activity. In fact, there are reports of pottery shards and other artifacts in deposits from the eruption of 1250 BP. Pottery fragments in deposits of an eruption that took place 2500 BP are also reported in this paper. Thus, the impact of the volcano on human activities has been frequent, with most of the repose intervals lasting between 100 to 600 years. The impact of the eruptions was probably of greater than local extent, because airfall tephra could reach distant sites and possibly even affect weather. The eruptive history of El Chichón also offers clues in the investigation of the Maya civilization. Several researchers have considered the volcano as an important factor in the answer to some intriguing questions such as the extensive use of volcanic ash in Late Classic Maya ceramics or, of greater importance, the causes of the collapse of the Classic Maya civilization.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004459900064
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