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  • 1
    Publication Date: 2017-04-04
    Description: The 200203 Mt Etna flank eruption began on 26 October 2002 and finished on 28 January 2003, after three months of continuous explosive activity and discontinuous lava flow output. The eruption involved the opening of eruptive fissures on the NE and S flanks of the volcano, with lava flow output and fire fountaining until 5 November. After this date, the eruption continued exclusively on the S flank, with continuous explosive activity and lava flows active between 13 November and 28 January 2003. Multi-disciplinary data collected during the eruption (petrology, analyses of ash components, gas geochemistry, field surveys, thermal mapping and structural surveys) allowed us to analyse the dynamics of the eruption. The eruption was triggered either by (i) accumulation and eventual ascent of magma from depth or (ii) depressurisation of the edifice due to spreading of the eastern flank of the volcano. The extraordinary explosivity makes the 200203 eruption a unique event in the last 300 years, comparable only with La Montagnola 1763 and the 2001 Lower Vents eruptions. A notable feature of the eruption was also the simultaneous effusion of lavas with different composition and emplacement features. Magma erupted from the NE fissure represented the partially degassed magma fraction normally residing within the central conduits and the shallow plumbing system. The magma that erupted from the S fissure was the relatively undegassed, volatile-rich, buoyant fraction which drained the deep feeding system, bypassing the central conduits. This is typical of most Etnean eccentric eruptions. We believe that there is a high probability that Mount Etna has entered a new eruptive phase, with magma being supplied to a deep reservoir independent from the central conduit, that could periodically produce sufficient overpressure to propagate a dyke to the surface and generate further flank eruptions.
    Description: Published
    Description: 314-330
    Description: partially_open
    Keywords: Multi-disciplinary study ; Mount Etna ; 2002–03 eruption ; Eccentric eruptions ; Flank activity ; Etna feeding system ; Volcanic processes ; 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: 523 bytes
    Format: 846913 bytes
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  • 2
    Publication Date: 2017-04-04
    Description: We have characterized pumice products belonging to the climactic phase of the 800-year-b.p. Quilotoa eruption. Bulk rock compositions, petrography, mineral, and glass chemistry and textural investigations were performed on the three end-member pumice types, namely white, gray, and mingled pumices. All the investigated pumice clasts are dacites characterized by the same bulk rock composition and mineralogical assemblage, but glass compositions and bulk textures change according to different pumice types. White pumice has higher crystallinity (~48 wt%), abundant euhedral pheno/microphenocrysts, no groundmass microlites, the most evolved glass compositions (7478 wt% SiO2), and heterogeneous vesicle populations marked by deformed and highly coalesced vesicles with thin walls. Gray pumice exhibits lower crystallinity (2936 wt%), abundant broken and/or resorbed crystals, ubiquitous groundmass phenocryst fragments and microlites, the widest range of glass compositions (6978 wt% SiO2), and quite homogeneous poorly deformed and coalesced vesicles with thicker walls. Mingled pumices are characterized by the alternation of bands or patches with white and gray pumice compositional and textural characteristics. We attribute heterogeneities in glass compositions and crystal and vesicle textures to processes occurring within volcanic conduits as magma is ascending to the surface. In particular, the above observations and results are consistent with an origin of a gray magma by heating of the original white magma in a strongly sheared region of the conduit because of a mechanism of viscous dissipation and crystal grinding and resorption at the conduit walls. The less viscous gray magma, therefore, would enable the onset and preservation of a high mass flux of the eruption otherwise difficult to explain for highly viscous crystal-rich dacitic magmas.
    Description: Published
    Description: 307-321
    Description: partially_open
    Keywords: Plinian eruption ; Crystal-rich magma ; Crystal grinding ; Pumice types ; Viscous dissipation ; 04. Solid Earth::04.08. Volcanology::04.08.03. Magmas ; 05. General::05.02. Data dissemination::05.02.03. Volcanic eruptions
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Type: article
    Format: 523 bytes
    Format: 909117 bytes
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