http://hdl.handle.net/2122/266 Ricerca nel canale cerca http://www.earth-prints.org/simple-search http://hdl.handle.net/2122/5939 Titolo: Introduction to Pageoph Topical Volume on 'Rock Physics and Natural Hazards'<br/><br/>Autori: Vinciguerra, S.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma1, Roma, Italia; Bernabé, Y.; Univ. of Strasbourg<br/><br/>Abstract: Natural hazards events such as Earthquakes or volcanic eruptions involve activation of coupled thermo-hydro-chemo-mechanical processes in rocks. The 7th. Euro-conference of Rock Physics and Geomechanics sponsored by the Italian Istituto Nazionale di Geofisica e Vulcanologia (INGV), the French Centre National de Recherche Scientifique (CNRS) and Exon-Mobil, was held on September 25 to 30, 2007, in Erice, Italy, to explore how rock physics experiments and models can help understand and constrain natural hazards mechanisms, and, to foster cross-disciplinary collaborations. Thu, 01 Jan 2009 00:00:00 GMT http://hdl.handle.net/2122/5937 Titolo: Understanding stress and deformation in active volcanoes<br/><br/>Autori: Gudmundsson, A.; Univ. London Royal Holloway; Acocella, V.; Univ. Roma 3; Vinciguerra, S.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma1, Roma, Italia<br/><br/>Abstract: No eruption, no caldera collapse, and no landslide can take place in a volcano unless its state of stress is suitable for the associated type of rock failure. The state of stress, in turn, results in deformation, and both stress and deformation depend on the mechanical properties of the rocks that constitute the volcano. Understanding stress and deformation in volcanoes is thus of fundamental importance for understanding unrest periods and for accurate forecasting volcano failure, such as may result in large-scale lateral and vertical collapses and eruptions. Fri, 17 Apr 2009 00:00:00 GMT http://hdl.handle.net/2122/5890 Titolo: Importance of structural history in the summit area of Stromboli during the 2002–2003 eruptive crisis inferred from temperature, soil CO2, self-potential, and electrical resistivity tomography<br/><br/>Autori: Finizola, A.; Laboratoire GéoSciences Réunion, Université de La Réunion; Aubert, M.; Laboratoire Magmas et Volcans, Clermont-Université; Revil, A.; LGIT, UMR 5559, CNRS, Equipe Volcan, Université de Savoie; Schütze, C.; Department of Geophysics and Geology, Universität Leipzig; Sortino, F.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Palermo, Palermo, Italia<br/><br/>Abstract: assess the stability of the flanks of this volcanic edifice during such a crisis. To provide a response to thisquestion, we analyzed a detailed fluid flow mapping plus the reiteration of a profile located in the vicinity ofthe active vents using the self-potential method, temperature data, soil-gas (CO2) measurements, andelectric resistivity tomography. Coupling the interpretation of these methods that are sensitive to the flowof gas and water in the ground indicates the position of areas of mechanical weakness. In addition, they canbe used to monitor the change in the discharge of fluids associated with these features before and during the2002–2003 eruptive crisis. Our results emphasize the importance of old structural boundaries, such as theLarge Fossa crater, in the development of the new set of fractures observed during the 2002–2003 eruptivecrisis. Between October 2002 and January 2003, the use of CO2 soil-gas technique evidenced an increase inthe discharge of CO2 outside the Large Fossa crater boundaries, along the failure boundary of the southernSciara del Fuoco area. Self-potential and temperature measurements made before the 2002–2003 eruptivecrisis reveal significant changes along the main structural boundaries of the Fossa area. The development ofthese anomalies is interpreted as an increase of the permeability of the structure from May 2000 to May2002. Between January 2003 and March 2003 the reiteration of self-potential, temperature, and CO2measurements shows an increase of fluid discharge along weakness planes located inside the Large Fossacrater boundary. They evidence no change outside this structural boundary. The importance of the LargeFossa crater boundary in controlling the deformation and fluid flow from January to March 2003 hasbeen attested by the development of the fractures inside the Large Fossa crater boundary, and also with anetwork of electrooptical distance measurement stations located inside and outside this ancient crater. Thismultidisciplinary approach to fluid flow assessment before and during an eruptive crisis is complementary togeodetic measurements of the deformation of the edifice. It demonstrates for the first time the powerfulpotential of combining electrical resistivity tomography, self-potential, temperature, and soil CO2measurements in assessing the position of the planes of mechanical weakness in a volcanic edifice. Fri, 17 Apr 2009 00:00:00 GMT http://hdl.handle.net/2122/5825 Titolo: Petrologic and Geochemical Composition of the AND-2A Core, ANDRILL Southern McMurdo Sound Project, Antartica<br/><br/>Autori: Panter, K. S.; Dept. of Geology, Bowling Green State University, Bowling Green, OH, 43403 – USA; Talarico, F. M.; Dipt. di Scienze della Terra, Università di Siena, Siena – Italy; Bassett, K.; Dept. of Geological Science, University of Canterbury, Private Bag 4800, Christchurch - New Zealand; Del Carlo, P.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Pisa, Pisa, Italia; Field, B.; GNS Science, 1 Fairway Ave, Lower Hutt − New Zealand; Frank, T.; Dept. of Geosciences, University of Nebraska-Lincoln, Lincoln, NE 68588 − USA; Hoffman, S.; Dept. of Sedimentology & Environ., Geology, Geoscience Center Göttingen (GZG), Goldschmidtstr. 3, 37077 Göttingen − Germany; Kuhn, G.; Alfred Wegener Institute for Polar and Marine Research, 27568 Bremerhaven – Germany; Reichelt, L.; Dept. of Sedimentology & Environ., Geology, Geoscience Center Göttingen (GZG), Goldschmidtstr. 3, 37077 Göttingen − Germany; Sandroni, S.; Dipt. di Scienze della Terra, Università di Siena, Siena – Italy; Taviani, M.; ISMAR-CNR, Bologna −Italy; Bracciali, L.; Dipt. di Scienze della Terra, Università di Pisa, Pisa −Italy; Cornamusini, G.; Dipt. di Scienze della Terra, Università di Siena, Siena – Italy; Centro di Geotecnologie, Università di Siena, San Giovanni Val d’Arno, Arezzo – Italy; von Eynatten, H.; Dept. of Sedimentology & Environ., Geology, Geoscience Center Göttingen (GZG), Goldschmidtstr. 3, 37077 Göttingen − Germany; Rocchi, R.; Dipt. di Scienze della Terra, Università di Pisa, Pisa , Italy<br/><br/>Abstract: The compositional record of the AND-2A drillcore is examined using petrological, sedimentological, volcanological and geochemical analysis of clasts, sediments and pore waters. Preliminary investigations of basement clasts (granitoids and metasediments) indicate both local and distal sources corresponding to variable ice-volume and ice-flow directions. Low abundance of sedimentary clasts (e.g., arkose, litharenite) suggests reduced contributions from sedimentary covers while intraclasts (e.g., diamictite, conglomerate) attest to intrabasinal reworking. Volcanic material includes pyroclasts (e.g., pumice, scoria), sediments and lava. Primary and reworked tephra layers occur within the Early Miocene interval (1093 to 640 metres below sea floor). The compositions of volcanic clasts reveal a diversity of alkaline types derived from the McMurdo Volcanic Group. Finer-grained sediments (e.g., sandstone, siltstone) show increases in biogenic silica and volcanic glass from 230 to 780 mbsf and higher proportions of terrigenous material ca. 350 to 750 mbsf and below 970 mbsf. Basement clast assemblages suggest a dominant provenance from the Skelton Glacier - Darwin Glacier area and from the Ferrar Glacier - Koettlitz Glacier area. Provenance of sand grains is consistent with clast sources. Thirteen Geochemical Units are established based on compositional trends derived from continuous XRF scanning. High values of Fe and Ti indicate terrigenous and volcanic sources, whereas high Ca values signify either biogenic or diagenic sources. Highly alkaline and saline pore waters were produced by chemical exchange with glass at moderately elevated temperatures. Thu, 01 Jan 2009 00:00:00 GMT http://hdl.handle.net/2122/5789 Titolo: Degassing, crystallization and eruption dynamics at Stromboli: trace element and lithium isotopic evidence from 2003 ashes<br/><br/>Autori: Schiavi, F.; Bayerisches Geoinstitut, Universität Bayreuth, 95440 Bayreuth, Germany; Kobayashi, K.; The Pheasant Memorial Laboratory for Geochemistry and Cosmochemistry (PML), Institute for Study of the Earth’s Interior, Okayama University at Misasa, Tottori-ken 682-0193, Japan; Moriguti, T.; The Pheasant Memorial Laboratory for Geochemistry and Cosmochemistry (PML), Institute for Study of the Earth’s Interior, Okayama University at Misasa, Tottori-ken 682-0193, Japan; Nakamura, E.; The Pheasant Memorial Laboratory for Geochemistry and Cosmochemistry (PML), Institute for Study of the Earth’s Interior, Okayama University at Misasa, Tottori-ken 682-0193, Japan; Pompilio, M.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Pisa, Pisa, Italia; Tiepolo, M.; CNR, Istituto di Geoscienze e Georisorse, Sezione di Pavia, 27100 Pavia, Italy; Vannucci, R.; CNR, Istituto di Geoscienze e Georisorse, Sezione di Pavia, 27100 Pavia, Italy; Dipartimento di Scienze della Terra, Università degli Studi di Pavia, 27100 Pavia, Italy<br/><br/>Abstract: During its 1800-year-long persistent activity the Stromboli volcano has erupted a highly porphyritic (HP) volatile-poor scoriaceous magma and a low porphyritic (LP) volatile-rich pumiceous magma. The HP magma is erupted during normal Strombolian explosions and lava effusions, while the LP one is related to more energetic paroxysms. During the March–April 2003 explosive activity, Stromboli ejected two typologies of juvenile glassy ashes, namely highly vesicular LP shards and volatile-poor HP shards. Their textural and in situ chemical characteristics are used to unravel mutual relationships between HP and LP magmas, as well as magma dynamics within the shallow plumbing system. The mantle-normalized trace element patterns of both ash types show the typical arc-lava pattern; however, HP glasses possess incompatible element concentrations higher than LP glasses, along with Sr and Eu negative anomalies. HP shards are generally characterized by higher Li contents (to ~20 ppm) and lower δ7Li values (+1.2 to −3.8‰) with respect to LP shards (Li contents of 7–14 ppm and δ7Li ranging between +4.6 and +0.9‰). Fractional crystallization models based on major and trace element compositions, combined with a degassing model based on open-system Rayleigh distillation and on the assumption that melt/fluidDLi > 1, show that abundant (~30%) plagioclase precipitation and variable degrees of degassing can lead the more primitive LP magma to evolve toward a differentiated (isotopically lighter) HP magma ponding in the upper conduit and undergoing slow continuous degassing-induced crystallization. This study also evidences that in March 2003 Stromboli volcano poured out a small early volume of LP magma that traveled slower within the conduit with respect to later and larger volumes of fast ascending LP magma erupted during the April 5 paroxysm. The different ascent rates and cooling rates of the two LP magma batches (i.e., pre- and post-paroxysm) resulted in small, but detectable, differences in their chemical signatures. Finally, this study highlights the high potential of in situ investigations of juvenile glassy ashes in petrologic and geochemical monitoring the volcanic activity and of Li isotopes as tracers of degassing processes within the shallow plumbing system. Thu, 01 Jan 2009 00:00:00 GMT http://hdl.handle.net/2122/5766 Titolo: The contribution of synchrotron X-ray computed microtomography to understanding volcanic processes<br/><br/>Autori: Polacci, M.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Pisa, Pisa, Italia; Mancini, L.; SYRMEP Group, Sincrotrone Trieste SCpA, Basovizza (Trieste), Italy; Baker, D. R.; Earth and Planetary Sciences, McGill University, GEOTOP-UQUAM-McGill Research Centre, Montreal, QC H3A2A7, Canada; Sincrotrone Trieste SCpA, Basovizza (Trieste), Italy.<br/><br/>Abstract: A series of computer microtomography experiments are reported which were performed by using a third-generation synchrotron radiation source on volcanic rocks from various active hazardous volcanoes in Italy and other volcanic areas in the world. The applied technique allowed the internal structure of the investigated material to be accurately imaged at the micrometer scale and three-dimensional views of the investigated samples to be produced as well as three-dimensional quantitative measurements of textural features. Thegeometryof thevesicle (gas-filledvoid) network in volcanic products of both basaltic and trachytic compositions were particularly focused on, as vesicle textures are directly linked to the dynamics of volcano degassing. This investigation provided novel insights into modes of gas exsolution, transport and loss in magmas that were not recognized in previous studies using solely conventional two- dimensional imaging techniques. The results of this study are important to understanding the behaviour of volcanoes and can be combined with other geosciences disciplines to forecast their future activity. Thu, 01 Jan 2009 00:00:00 GMT http://hdl.handle.net/2122/5758 Titolo: The role of syn-eruptive vesiculation on explosive basaltic activity at Mt. Etna, Italy<br/><br/>Autori: Polacci, M.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Pisa, Pisa, Italia; Burton, M. R.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Pisa, Pisa, Italia; La Spina, A.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Catania, Catania, Italia; Murè, F.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Catania, Catania, Italia; Favretto, S.; Dipartimento Materiali e Risorse Naturali, Trieste, Italy; Zanini, F.; SYRMEP Group, Sincrotrone Trieste S.C.p.A., Basovizza, Italy<br/><br/>Abstract: We investigated the dynamics of explosive activity at Mt. Etna between 31 August and 15 December 2006 by combining vesicle studies in the erupted products with measurements of the gas composition at the active, summit crater. The analysed scoria clasts present large, connected vesicles with complex shapes and smaller, isolated, spherical vesicles, the content of which increases in scoriae from the most explosive events. Gas geochemistry reports CO2/SO2 and SO2/HCl ratios supporting a deep-derived gas phase for fire-fountain activity. By integrating results from scoria vesiculation and gas analysis we find that the highest energy episodes of Mt. Etna activity in 2006 were driven by a previously accumulated CO2-rich gas phase but we highlight the lesser role of syn-eruptive vesicle nucleation driven by water exsolution during ascent. We conclude that syn-eruptive vesiculation is a common process in Etnean magmas that may promote a deeper conduit magma fragmentation and increase ash formation. Tue, 20 Jan 2009 00:00:00 GMT http://hdl.handle.net/2122/5745 Titolo: Dissolution/crystallization kinetics recorded in the 2002–2003 lavas of Stromboli (Italy)<br/><br/>Autori: Fornaciai, A.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Pisa, Pisa, Italia; Landi, P.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Pisa, Pisa, Italia; Armenti, P.; Dipartimento di Scienze della Terra, University of Pisa, Pisa, Italy<br/><br/>Abstract: On 28 December 2002, new vents opened on the flanks of Stromboli, just below the summit craters, interrupting the persistent activity of the volcano with a 7-month-long effusive eruption. We here report on the plagioclase size distribution (PlgSD) in lava samples collected following the chronology of the 2002–2003 eruption. Data reveal a linear PlgSD similar to that found in samples of normal Stromboli activity, indicating that the switch from Strombolian explosive to effusive activity is not associated with changes in texture. Nevertheless, the crystal size distribution slopes and intercepts exhibit slight sinusoidal temporal variations that are here ascribed to a magma supply mechanism able to induce “resonance” in the crystal size distribution, with an amplitude that depends on the supply rate. Sat, 01 Aug 2009 00:00:00 GMT http://hdl.handle.net/2122/5735 Titolo: Landsat 5 TM images and DEM in lithologic mapping of Payen Volcanic Field (Mendoza Province, Argentina)<br/><br/>Autori: Fornaciai, A.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Pisa, Pisa, Italia; Bisson, M.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Pisa, Pisa, Italia; Mazzarini, F.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Pisa, Pisa, Italia; Del Carlo, P.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Pisa, Pisa, Italia; Pasquarè, G.; Dipartimento di Scienze della Terra, Università degli Studi di Milano, Milano, Italy<br/><br/>Abstract: Satellite image such as Landsat 5 TM scene provides excellent representation of Earth and synoptic view of large geographic areas in different band combination. Landsat TM images allow automatic and semi-automatic classification of land cover, nevertheless the software frequently may have some difficulties in distinguishing between similar radiometric surfaces. In this case, the use of Digital Elevation Model (DEM) can be an important tool to identifydifferent surface covers. In this study, several False Color Composite (FCC) of Landsat 5 TM Image, DEM and the respective draped image of them, were used to delineate lithological boundaries and tectonic features of regional significance of the Payen Volcanic Field (PVF). PVF is a Quaternary fissural structure belonging to the back-arc extensional area of the Andes in the Mendoza Province (Argentina) characterized by many composite basaltic lava flow fields. The necessityto identify different lava flows with the same composition, and then with same spectral features, allows to highlight the improvement of synergic use of TM images and shaded DEM in the visual interpretation. Information obtained from Satellite data and DEM have been compared with previous geological maps and transferred into a topographical base map. Based on these data a new lithological map at 1:100.000 scale has been presented. Thu, 01 Jan 2009 00:00:00 GMT http://hdl.handle.net/2122/5734 Titolo: The distal segment of Etna’s 2001 basaltic lava flow<br/><br/>Autori: Favalli, M.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Pisa, Pisa, Italia; Harris, A. J. L.; HIGP/SOEST, University of Hawaii, Honolulu, Hawaii, USA; Laboratoire Magmas et Volcans, Université Blaise Pascal, Clermont-Ferrand, France; Fornaciai, A.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Pisa, Pisa, Italia; Pareschi, M. T.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Pisa, Pisa, Italia; Mazzarini, F.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Pisa, Pisa, Italia<br/><br/>Abstract: Etna’s 2001 basaltic lava flow provided a good example of the distal flow segment between the flow front and stable channel, across which the flow evolves from channel-contained to dispersed. This zone was mapped with meter precision using LIDAR data collected during 2004 and 2005. These data, supported by field mapping, show that the flow front comprised eight lobes each 10 to 20 m high. The flow front appears to have advanced not as a single unit, but as a series of lobes moving forward one lobe at a time. Primary lobes were centered on the channel axis and marginal lobes were off-axis. The lobes advanced as breakouts of low-yield-strength lava from the flow core of the stalled flow front. Marginal lobes were abandoned and contributed to marginal levees flanking the transitional channel. For Etna’s 2001 flow, the transitional channel is 140 m wide, 700 m long and fed a 240-m-long zone of dispersed flow; the change from stable to transitional channel occurred at a major reduction in slope. Above this, the stable channel is 5.2 km long, 55 to 105 m wide and bounded by 15- to 25-m-high levees, and the stable channel is located over a previous channel. In a final stage of activity, lava ponding at the break-in-slope that marks the terminus of the stable channel put pressure on the eastern levee, causing it to fail. Liberated lava then fed a final break-out to the east. Similar flow front-features occur at other volcanoes, indicating that similar processes are characteristic of dispersed flow zones. Thu, 01 Jan 2009 00:00:00 GMT