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  • 1
    Electronic Resource
    Electronic Resource
    Pyroclastic flows and surges over water: an example from the 1883 Krakatau eruption (1996)
    Springer
    Bulletin of volcanology 57 (1996), S. 493-511 
    Details
    ISSN: 1432-0819
    Keywords: Krakatau ; Pyroclastic flows ; Pyroclastic surge ; Tsunamis ; Volcanic hazard ; Explosive eruption
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Notes: Abstract Pyroclastic deposits from the 1883 eruption of Krakatau are described from areas northeast of the volcano on the islands of Sebesi, Sebuku, and Lagoendi, and the southeast coast of Sumatra. Massive and poorly stratified units formed predominantly from pyroclastic flows and surges that traveled over the sea for distances up to 80 km. Granulometric and lithologic characteristics of the deposits indicate that they represent the complement of proximal subaerial and submarine pyroclastic flow deposits laid down on and close to the Krakatau islands. The distal deposits exhibit a decrease in sorting coefficient, median grain size, and thickness with increasing distance from Krakatau. Crystal fractionation is consistent with the distal facies being derived from the upper part of gravitationally segregated pyroclastic flows in which the relative amount of crystal enrichment and abundance of dense lithic clasts diminished upwards. The deposits are correlated to a major pyroclastic flow phase that occurred on the morning of 27 August at approximately 10 a.m. Energetic flows spread out away from the volcano at speeds in excess of 100 km/h and traveled up to 80 km from source. The flows retained temperatures high enough to burn victims on the SW coast of Sumatra. Historical accounts from ships in the Sunda Straits constrain the area affected by the flows to a minimum of 4x103 km2. At the distal edge of this area the flows were relatively dilute and turbulent, yet carried enough material to deposit several tens of centimeters of tephra. The great mobility of the Krakatau flows from the 10 a.m. activity may be the result of enhanced runout over the sea. It is proposed that the generation of steam at the flow/seawater interface may have led to a reduction in the sedimentation of particles and consequently a delay in the time before the flows ceased lateral motion and became buoyantly convective. The buoyant distal edge of these ash-and steam-laden clouds lifted off into the atmosphere, leading to cooling, condensation, and mud rain.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00304435
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    Source of Ash Zone 1 in the North Atlantic (1995)
    Springer
    Bulletin of volcanology 57 (1995), S. 18-32 
    Details
    ISSN: 1432-0819
    Keywords: Key words Ash Zone 1 ; Katla volcano ; Sólheimar ignimbrite ; Co-ignimbrite ash ; Volcaniclastic turbidites ; Pyroclastic flows ; Jökulhlaup
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Notes: Abstract   Geochemical evidence shows that the silicic component of the widespread Ash Zone 1 in the North Atlantic is derived from a major ignimbrite-forming eruption which occurred at the Katla caldera in southern Iceland during the transition from glacial to interglacial conditions in Younger Dryas time. Both trace and major element evidence of the rhyolitic products excludes the Öræfajökull volcano as a source. The high-Ti basaltic component in the marine ash zone can also be attributed to contemporaneous eruption in the Katla volcanic complex. Dispersal of tephra from this event is primarily attributed to the generation of co-ignimbrite ash columns in the atmosphere, with ash fallout on both sea ice and on the ocean floor north and east of Iceland. Owing to the changing ocean circulation characteristics of the glacial regime, including suppression of the Irminger Current and a stronger North Atlantic Current, tephra was rafted on sea ice south into the central North Atlantic and deposited as dispersed Ash Zone 1. Sediments south of Iceland also show evidence of the formation of ash turbidites, generated either by the entrance of pyroclastic flows into the sea, or during discharge of jökulhlaups or glacier bursts from this sub-glacial eruption.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00298704
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    Paper (German National Licenses)
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  • 3
    Electronic Resource
    Electronic Resource
    Sedimentology of the Krakatau 1883 submarine pyroclastic deposits (1996)
    Springer
    Bulletin of volcanology 57 (1996), S. 512-529 
    Details
    ISSN: 1432-0819
    Keywords: Facies ; Grain size ; Components ; Pyroclastic flows ; Subaerial ; Emplacement process
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Notes: Abstract The majority of tephra generated during the paroxysmal 1883 eruption of Krakatau volcano, Indonesia, was deposited in the sea within a 15-km radius of the caldera. Two syneruptive pyroclastic facies have been recovered in SCUBA cores which sampled the 1883 subaqueous pyroclastic deposit. The most commonly recovered facies is a massive textured, poorly sorted mixture of pumice and lithic lapilli-to-block-sized fragments set in a silty to sandy ash matrix. This facies is indistinguishable from the 1883 subaerial pyroclastic flow deposits preserved on the Krakatau islands on the basis of grain size and component abundances. A less common facies consists of well-sorted, planarlaminated to low-angle cross-bedded, vitric-enriched silty ash. Entrance of subaerial pyroclastic flows into the sea resulted in subaqueous deposition of the massive facies primarily by deceleration and sinking of highly concentrated, deflated components of pyroclastic flows as they traveled over water. The basal component of the deposit suggests no mixing with seawater as inferred from retention of the fine ash fraction, high temperature of emplacement, and lack of traction structures, and no significant hydraulic sorting of components. The laminated facies was most likely deposited from low-concentration pyroclastic density currents generated by shear along the boundary between the submarine pyroclastic flows and seawater. The Krakatau deposits are the first well-documented example of true submarine pyroclastic flow deposition from a modern eruption, and thus constitute an important analog for the interpretation of ancient sequences where subaqueous deposition has been inferred based on the facies characteristics of encapsulating sedimentary sequences.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00304436
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    Paper (German National Licenses)
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  • 4
    Electronic Resource
    Electronic Resource
    Experimental constraints on pre-eruptive water contents and changing magma storage prior to explosive eruptions of Mount St Helens volcano (1995)
    Springer
    Bulletin of volcanology 57 (1995), S. 1-17 
    Details
    ISSN: 1432-0819
    Keywords: Mount St Helens ; Experimental petrology ; Explosive volcanism ; Magmatic water contents ; Magmatic storage region
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Notes: Abstract Compositionally diverse dacitic magmas have erupted from Mount St Helens over the last 4000 years. Phase assemblages and their compositions in these dacites provide information about the composition of the pre-eruptive melt, the phases in equilibrium with that melt and the magmatic temperature. From this information pre-eruptive pressures and water fugacities of many of the dacites have been inferred. This was done by conducting hydrothermal experiments at 850°C and a range of pressures and water fugacities and combining the results with those from experiments at temperatures of 780 and 920°C, to cover the likely range in equilibration conditions of the dacites. Natural phase assemblages and compositions were compared with the experimental results to infer the most likely conditions for the magmas prior to eruption. Water contents disolved in the melts of the dacites were then estimated from the inferred conditions. Water contents in the dacites have varied greatly, from 3.7 to 6.5 wt.%, in the last 4000 years. Between 4000 and about 3000 years ago the dacites tended to be water saturated and contained 5.5 to 6.5 wt.% water. Since then, however, the dacites have been significantly water-undersaturated and contained less than 5.0 wt.% water. These dacites have tended to be hotter and more mafic, and andesitic and basaltic magmas have erupted. These changes can be explained by variable amounts of mixing between felsic dacite and basalt, to produce hotter, drier and more mafic dacites and andesites. The magma storage region of the dacitic magmas has also varied significantly during the 4000 years, with shifts to shallower levels in the crust occurring within very short time periods, possibly even two years. These shifts may be related to fracturing of overlying roof rock as a result of magma with-drawal during larger volume eruptions.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00298703
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    Paper (German National Licenses)
    Fulltext
  • 5
    Electronic Resource
    Electronic Resource
    Source of Ash Zone 1 in the North Atlantic (1995)
    Springer
    Bulletin of volcanology 57 (1995), S. 18-32 
    Details
    ISSN: 1432-0819
    Keywords: Ash Zone 1 ; Katla volcano ; Sólheimar ignimbrite ; Co-ignimbrite ash ; Volcaniclastic turbidites ; Pyroclastic flows ; Jökulhlaup
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Notes: Abstract Geochemical evidence shows that the silicic component of the widespread Ash Zone 1 in the North Atlantic is derived from a major ignimbrite-forming eruption which occurred at the Katla caldera in southern Iceland during the transition from glacial to interglacial conditions in Younger Dryas time. Both trace and major element evidence of the rhyolitic products excludes the Öræfajökull volcano as a source. The high-Ti basaltic component in the marine ash zone can also be attributed to contemporaneous eruption in the Katla volcanic complex. Dispersal of tephra from this event is primarily attributed to the generation of co-ignimbrite ash columns in the atmosphere, with ash fallout on both sea ice and on the ocean floor north and east of Iceland. Owing to the changing ocean circulation characteristics of the glacial regime, including suppression of the Irminger Current and a stronger North Atlantic Current, tephra was rafted on sea ice south into the central North Atlantic and deposited as dispersed Ash Zone 1. Sediments south of Iceland also show evidence of the formation of ash turbidites, generated either by the entrance of pyroclastic flows into the sea, or during discharge of jökulhlaups or glacier bursts from this subglacial eruption.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00298704
    Library Location Call Number Volume/Issue/Year Availability
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    Paper (German National Licenses)
    Fulltext
  • 6
    Electronic Resource
    Electronic Resource
    Experimental constraints on pre-eruptive water contents and changing magma storage prior to explosive eruptions of Mount St Helens volcano (1995)
    Springer
    Bulletin of volcanology 57 (1995), S. 1-17 
    Details
    ISSN: 1432-0819
    Keywords: Key words Mount St Helens ; Experimental petrology ; Explosive volcanism ; Magmatic water contents ; Magmatic storage region
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Notes: Abstract  Compositionally diverse dacitic magmas have erupted from Mount St Helens over the last 4000 years. Phase assemblages and their compositions in these dacites provide information about the composition of the pre-eruptive melt, the phases in equilibrium with that melt and the magmatic temperature. From this information pre-eruptive pressures and water fugacities of many of the dacites have been inferred. This was done by conducting hydrothermal experiments at 850°  C and a range of pressures and water fugacities and combining the results with those from experiments at temperatures of 780 and 920°  C, to cover the likely range in equilibration conditions of the dacites. Natural phase assemblages and compositions were compared with the experimental results to infer the most likely conditions for the magmas prior to eruption. Water contents dissolved in the melts of the dacites were then estimated from the inferred conditions. Water contents in the dacites have varied greatly, from 3.7 to 6.5 wt.%, in the last 4000 years. Between 4000 and about 3000 years ago the dacites tended to be water saturated and contained 5.5 to 6.5 wt.% water. Since then, however, the dacites have been significantly water-undersaturated and contained less than 5.0 wt.% water. These dacites have tended to be hotter and more mafic, and andesitic and basaltic magmas have erupted. These changes can be explained by variable amounts of mixing between felsic dacite and basalt, to produce hotter, drier and more mafic dacites and andesites. The magma storage region of the dacitic magmas has also varied significantly during the 4000 years, with shifts to shallower levels in the crust occurring within very short time periods, possibly even two years. These shifts may be related to fracturing of overlying roof rock as a result of magma withdrawal during larger volume eruptions.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00298703
    Library Location Call Number Volume/Issue/Year Availability
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    Paper (German National Licenses)
    Fulltext
  • 7
    Electronic Resource
    Electronic Resource
    Prospective, multicenter study of laparoscopic ventral hernioplasty (1998)
    Springer
    Surgical endoscopy and other interventional techniques 12 (1998), S. 955-959 
    Details
    ISSN: 1432-2218
    Keywords: Key words: Laparoscopic hernioplasty — Ventral — Incisional — Expanded polytetrafluoroethylene — Peritoneal onlay — Multicenter study — Tension-free repair — Human
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Background: A standard technique for laparoscopic ventral hernioplasty (peritoneal onlay using an expanded polytetrafluoroethylene [ePTFE] patch for hernias ≥4 cm2) is being used in a prospective, multicenter, long-term study. Methods: Demographic, operative, and postoperative data were collected and analyzed. Follow-up clinical evaluations were conducted 7–10 days, 4 weeks, 6 months, 1 year, and then annually after surgery in all patients. Results: In the first 2 years of the study, 144 patients were enrolled; nine were lost to follow-up. The mean operating time was 120 min. The mean follow-up was 222 days (range 5–731). Postoperative complications were five infections, three cases of prolonged ileus, one bowel obstruction, 23 seromas (15 resolved without intervention), and six hernia recurrences. Hospital discharge occurred a mean of 2.3 days after surgery and return to normal activity a mean of 15 days postoperatively. Conclusions: Laparoscopic prosthetic ventral hernioplasty avoids the large wound required in open repairs, with attendant complications and recurrences, and appears safe, especially if an ePTFE mesh is used. Compared with conventional open ventral hernioplasty, the laparoscopic technique may also allow shorter hospitalization and a quicker return to normal activities after surgery.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004649900755
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    Paper (German National Licenses)
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