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  • 1
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    The influence of conduit processes on changes in style of basaltic Plinian eruptions: Tarawera 1886 and Etna 122 BC (2005)
    Elsevier
    Details
    Publication Date: 2017-04-04
    Description: Basaltic volcanism is most typically thought to produce effusion of lava, with the most explosive manifestations ranging from mild Strombolian activity to more energetic fire fountain eruptions. However, some basaltic eruptions are now recognized as extremely violent, i.e., generating widespread phreatomagmatic, subplinian and Plinian fall deposits. We focus here on the influence of conduit processes, especially partial open-system degassing, in triggering abrupt changes in style and intensity that occurred during two examples of basaltic Plinian volcanism. We use the 1886 eruption of Tarawera, New Zealand, the youngest known basaltic Plinian eruption and the only one for which there are detailed written eyewitness accounts, and the well-documented 122 BC eruption of Mount Etna, Italy, and present new grain size and vesicularity data from the proximal deposits. These data show that even during extremely powerful basaltic eruptions, conduit processes play a critical role in modifying the form of the eruptions. Even with very high discharge, and presumably ascent, rates, partial open-system behaviour of basaltic melts becomes a critical factor that leads to development of domains of largely stagnant and outgassed melt that restricts the effective radius of the conduit. The exact path taken in the waning stages of the eruptions varied, in response to factors which included conduit geometry, efficiency and extent of outgassing and availability of ground water, but a relatively abrupt cessation to sustained high-intensity discharge was an inevitable consequence of the degassing processes.
    Description: Published
    Description: 1-14
    Description: partially_open
    Keywords: basaltic Plinian eruption ; Etna ; Tarawera and explosive volcanism ; 04. Solid Earth::04.08. Volcanology::04.08.06. Volcano monitoring ; 05. General::05.02. Data dissemination::05.02.03. Volcanic eruptions
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Type: article
    Format: 520 bytes
    Format: 743033 bytes
    Format: text/html
    Format: application/pdf
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  • 2
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    Eruption dynamics of the 23 February 2013 event at Mt. Etna (2020)
    Elsevier
    Details
    Publication Date: 2020-03-02
    Description: Volcanic activity atMt. Etna in the last decade hasmostly beenmanifested by sequences of short paroxysmal episodes characterised by powerful lava fountains and high eruption columns. On the 23 February 2013, an exceptionally intense episode occurred at the New South-East Crater, producing a fountain N800 m high (among the highest ever recorded at Etna) and a ~9 km eruption column that dispersed ash N400 kmfromthe vent. Textural and petrographic analyses of lapilli revealed that magma erupted during the high-intensity phase is characterised by lowmicrolite contents (b7 area%), high vesicularity (76–83%), and high vesicle number densities (6–8.2 × 106 cm−3). The short-lived initial Strombolian explosions removed viscous magma from the conduit, enabling the rapid ascent of gas-rich, microlite-poor magma and the eruption of an 800 mhigh fountain and 9 kmhigh eruption column. For the 23 February eruption, the high vesicularity and lowmicrolite content of the pyroclasts support the hypothesis that volatile-rich magma was the driver of the high intensity lava fountain. This eruptive event, along with three other recent events at Etna over the last 15 years, can be defined as subplinian based on eruption rate and column height, but also generated incandescent 800–1000 m fountains. For these reasons, we propose to term this event, and others at Etna characterised by similar eruption features and parameters, as subplinian fountaining events.
    Description: Published
    Description: 241-250
    Description: 5V. Processi eruttivi e post-eruttivi
    Description: JCR Journal
    Keywords: Eruption dynamics - 23 February 2013 - lava fountain - subplinian ; 04.08. Volcanology
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Type: article
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  • 3
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    Unknown
    Age and Eruptive Style of Volcanic Rocks Dredged from the Alpha Ridge, Arctic Ocean (2019)
    EGU
    In:  EPIC3EGU General Assembly 2019, Vienna, 2019-04-07-2019-04-12Vienna, EGU
    Details
    Publication Date: 2019-05-22
    Description: The Alpha–Mendeleev ridge complex is a prominent physiographic and geological feature of the Arctic Amerasia Basin. The Alpha and Mendeleev ridges are, respectively, the eastern and western components of a continuous seafloor high that is approximately 2000 km long and 200–400 km wide. A surge of interest in the tectonic evolution of Arctic submarine features has led to a wealth of new geophysical data collected from the Alpha Ridge. Current interpretations of its origin vary but there is compelling evidence that the Alpha Ridge may have formed as an oceanic plateau during the Late Cretaceous. Geological samples are rare but most samples recovered indicate a genetic link with the High Arctic Large Igneous Province (HALIP). In August 2016, Canada’s Extended Continental Margin-United Nations Convention on the Law of the Sea Program dredged approximately 100 kg of volcanic rocks from the Alpha Ridge. The large size and pristine state of the samples enabled the first comprehensive study of a single eruptive event in the volcanic record of the Alpha Ridge. The dredge sample is a lapilli tuff containing vitric and basaltic clasts. Textural evidence and the coexistence of juvenile and cognate clasts suggest a phreatomagmatic eruption. The vitric fragments consist of sideromelane glass with abundant plagioclase microlites. Texturally, these basaltic glass lapilli display a fresh glassy core surrounded by Fe- and Ti-rich zones and a palagonite rim. Major and trace element analyses of glassy cores indicate remarkably uniform, mildly alkaline basaltic compositions. The plagioclase-bearing glass yielded a 40Ar/39Ar plateau age of 90.40±0.26 Ma (2σ error) which included 89% of 39 Ar released. We interpret this result to represent the eruption age of the plagioclase microlites and consequently, of the host basaltic glass lapilli in the tuff. Volatile species analyses by infrared spectroscopy on the fresh basaltic glass suggests that the melt was effectively degassed to shallow level. Assuming equilibrium degassing, the homogeneous resulting values of H2O total in the range 0.1 to 0.19 wt.% (1σ error) indicate subaerial or shallow eruption (surface to 80 m). The new 40Ar/39Ar age for the sample is consistent with a 40 Ar/39Ar age of 89±1 Ma obtained for a sample of tholeiitic basalt dredged from the central part of the Alpha Ridge, and with the range of ages reported for HALIP igneous rocks exposed onshore in the Canadian Arctic Archipelago (130-80 Ma). Our new data provide evidence for local emergence of the Alpha Ridge in the Late Cretaceous. A comparison the Alpha Ridge and Kerguelen Plateau–Broken Ridge Large Igneous Province (LIP) provides new insights on the episodic nature of LIP magmatism and variations in eruptive style through time.
    Repository Name: EPIC Alfred Wegener Institut
    Type: Conference , notRev
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  • 4
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    Unknown
    Stronger or longer: Discriminating between Hawaiian and Strombolian eruption styles (2017)
    Geological Society of America
    Details
    Publication Date: 2023-01-16
    Description: The weakest explosive volcanic eruptions globally, Strombolian explosions and Hawaiian fountaining, are also the most common. Yet, despite over a hundred years of observations, no classifications have offered a convincing, quantitative way of demarcating these two styles. New observations show that the two styles are distinct in their eruptive time scale, with the duration of Hawaiian fountaining exceeding Strombolian explosions by similar to 300-10,000 s. This reflects the underlying process of whether shallow-exsolved gas remains trapped in the erupting magma or is decoupled from it. We propose here a classification scheme based on the duration of events (brief explosions versus prolonged fountains) with a cutoff at 300 s that separates transient Strombolian explosions from sustained Hawaiian fountains.
    Description: Published
    Description: 163-166
    Description: 3V. Dinamiche e scenari eruttivi
    Description: JCR Journal
    Description: restricted
    Keywords: Hawaiian and Strombolian eruption styles ; 05. General::05.02. Data dissemination::05.02.03. Volcanic eruptions
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Type: article
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  • 5
    Electronic Resource
    Electronic Resource
    Experiments towards realization of a recording medium capable of supporting near theoretical density (1999)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 85 (1999), S. 5537-5539 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A novel technique is reported for the preparation of dispersions of cobalt particles with a narrow distribution of diameters around an estimated mean of 8.5 nm. Particles of this size have blocking temperatures close to 220 °C and, dispersed to reduce mutual interaction, they constitute a near ideal ultrahigh density recording medium. Production of this medium requires a two-stage process: reactive sputtering to develop a precursor film of cobalt nitride followed by rapid thermal processing in vacuum. The precursor film disassociates leaving the required dispersion of cobalt particles. Varying thickness and density in the precursor films and the conditions attending the disassociation provides some control of the medium magnetic properties. Samples with saturation magnetisation (Ms) between 60% and 20% of bulk cobalt exhibit isotropic magnetic properties in-plane with high remanence and coercivities approaching 2 kOe. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.369886
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  • 6
    Electronic Resource
    Electronic Resource
    LABTRAN. Language and system for programming chemical experiments (1972)
    s.l. : American Chemical Society
    Analytical chemistry 44 (1972), S. 339-343 
    Details
    ISSN: 1520-6882
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1021/ac60310a003
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  • 7
    Electronic Resource
    Electronic Resource
    Asymmetric nonlinear magneto-optic effects in PtMnSb thin films : The 7th joint MMM-intermag conference on magnetism and magnetic materials (1998)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 83 (1998), S. 6739-6741 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Nonlinear magneto-optic measurements on thin films of PtMnSb exhibit asymmetric behavior in both the transverse and longitudinal Kerr configurations. Second harmonic generation under magnetization reversal is asymmetric about the state of zero magnetization with the degree of asymmetry dependent on the angle of incidence. The origin of the asymmetry arises from simultaneous detection of even (∝M2) and odd (∝M) magneto-optic effects. In principle such effects exist in both the optical linear and nonlinear regimes but in most materials even effects are very small and only observed in specific experimental arrangements where the linear effects in M vanish (such as the Voigt configuration). This is not the case with PtMnSb in which the band structure produces total polarization of the majority and minority spin carriers giving rise to unusually strong magneto-optic interactions. © 1998 American Institute of Physics. [S0021-8979(98)44411-6]
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.367786
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  • 8
    Electronic Resource
    Electronic Resource
    Nature of the electronic interactions in aryl-substituted polysilanes (1972)
    s.l. : American Chemical Society
    Journal of the American Chemical Society 94 (1972), S. 3806-3811 
    Details
    ISSN: 1520-5126
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1021/ja00766a024
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  • 9
    Electronic Resource
    Electronic Resource
    Optical and magneto-optical constants of Pr substituted TbFeCo films : 38th Annual Conference on Magnetism and Magnetic Materials (1994)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 75 (1994), S. 7087-7089 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Optimization of tri- or quadrilayer magneto-optic recording media requires knowledge of the optical and/or magneto-optical constants for all of the individual active or passive layers that together comprise the complete disk structure. The optical (n+ik) and first-order magneto-optical (Q1+iQ2) constants for two series (i) (Tb23Fe72.5Co4.5)100−xPrx, (ii) (Tb27Fe65Co8)100−xPrx of Pr substituted TbFeCo films, for which x varies between 0 and 30, have been determined by a combination of ellipsometry and Kerr polarimetry. Ellipsometry has also been used to determine independently the optical constants of the optimized SiN passivation layers developed to protect these samples. Using constants determined experimentally on thick samples, the variation of the polar Kerr rotation and ellipticity as a function of magnetic film thickness has been calculated for light incident from both the air and substrate side of a typical trilayer magneto-optic disk structure in which material from the above series, the magnetic and thermomagnetic properties of which have been previously reported [Carey et al., J. Magn. Magn. Mater. (to be published)], forms the active storage layer. The agreement obtained with measurements demonstrates the self-consistency of the modeling process and the validity of the determined constants.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.356737
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  • 10
    Electronic Resource
    Electronic Resource
    Compositional dependence of the structural and magnetic properties of PtMnSb films : 38th Annual Conference on Magnetism and Magnetic Materials (1994)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 75 (1994), S. 7081-7083 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Nonstoichiometric, Pt deficient, PtMnSb films have been investigated for evidence of the increase in coercivity suggested by the work of Marinero [Appl. Surf. Sci. 43, 117 (1989)]. Structural, magnetic, and magneto-optic properties of thin PtMnSb films of different compositions annealed in under 30 s using a rapid thermal processing (RTP) system [Carey et al., IEEE Meeting on Current Topics in Applied Magnetism, Keele University, 4 November 1992 (unpublished), Paper 15; J. Magn. Soc. Jpn. 17, 290 (1993)], have been determined. It is shown that the crystalline texture of the films can be controlled by adjustments in composition and RTP time and that Pt deficiency produces increases in coercivity. The production of coercivity does not correlate with the marked changes in texture but appears to be associated with the development of MnSb phases within the PtMnSb microstructure.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.356735
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