The eruptive history of Pantelleria (Sicily channel) in the last 50 ka     

L. Civetta  Y. Cornette  P. Y. Gillot  G. Orsi 《Bulletin of Volcanology》1988,50(1):47-57

Six silicic eruptive cycles have been recognized in the last 50 ka at Pantelleria. The products of each cycle exhibit a compositional variation from pantellerite to less peralkaline rhyolite or to trachyte. The relationships between the range of chemical variation, the erupted volume and the time of eruptions, allow us to estimate an average differentiation rate of 5% crystal fractionation per 1000 years and a constant long-term rate of magma discharge of 0.1 km³ per 1000 years. Pressure increase in the magma chamber caused by the addition of new magma, accumulation of highly-differentiated, volatile-rich magma in the roof zone and a concomitant build-up of a vapour phase, is postulated as a possible triggering mechanism for eruptions.  相似文献   

Timing of magma extraction during the Campanian Ignimbrite eruption (Campi Flegrei Caldera)     

L. Pappalardo  L. Civetta  S. de Vita  M. Di Vito  G. Orsi  A. Carandente  R. V. Fisher 《Journal of Volcanology and Geothermal Research》2002,114(3-4)

A core drilled within the northern part of the city of Napoli has offered the unique opportunity to observe in one single sequence the superposition of the four pyroclastic flow units emplaced during the Campanian Ignimbrite (CI) eruption. Such a stratigraphic succession has never been encountered before in natural or in man made exposures. Therefore the CI sequence was reconstructed only on the basis of stratigraphic correlations and compositional data (in literature). The occurrence of four superposed CI flows, together with all the data available (in literature) allowed us to better constrain the chemical stratigraphy of the deposit and the compositional structure of the CI magma chamber. The CI magma chamber includes two cogenetic magma layers, separated by a compositional gap. The upper magma layer was contaminated by interaction with radiogenic fluids. The two magma layers were extruded either individually or simultaneously during the course of the eruption. In the latter case they produced a hybrid magma. But no evidence of input of new geochemically and isotopically distinct magma batches just prior or during the eruption has been found. Comparison with the exposed CI deposits has permitted reconstruction of variable eruption phases and related magma withdrawal and caldera collapse episodes. The eruption was likely to have began with phreatomagmatic explosions followed by the formation of a sustained plinian eruption column fed by the simultaneous extraction from both magma layers. Towards the end of this phase the upward migration of the fragmentation surface and the decrease in magma eruption rate and/or activation of fractures formed an unstable pulsating column that was fed only by the most-evolved magma layer. This plinian phase was followed by the collapse of the eruption column and the beginning of caldera formation. At this stage expanded pyroclastic flows fed by the upper magma layer in the chamber generated. During the following major caldera collapse episode, the maximum mass discharge rate was reached and both magma layers were tapped, generating expanded pyroclastic flows. Towards the end of the eruption, only the deeper and less differentiated magma layer was tapped producing more concentrated pyroclastic flows that traveled short distances.  相似文献   

Geographic Information Technologies and the History of a Shoreline: The Case of Chapter 91 in New Bedford,Massachusetts*     

Alberto Giordano  Richard Gelpke 《The Professional geographer》2003,55(3):329-342

This article discusses the use of geographic information technologies to assist researchers in the exploration of historical databases. The case study is a pilot project in which we used geographic information systems (GIS) and global positioning systems (GPS) to study the history of the Public Waterfront Act (the “Chapter 91” program), a policy designed to balance private property rights, public interest, and environmental protection in the Massachusetts tidelands. The issues discussed range from the role of GIS in society and its limitations as a representational tool to the ability of current GIS to deal with historical data and to manage temporal attributes.  相似文献   

Places of the Holocaust: Towards a model of GIS of place     

Alberto Giordano  Tim Cole 《Transactions in GIS》2020,24(4):842-857

Progress toward developing a GIS of place can only follow from an understanding of what place is, and this understanding draws on geographical theory. Here—following Agnew, Tuan, and others—we consider place as being made up of three components—location, locale, and sense of place—which are recognizable at multiple scales and vary historically as a product of social and political processes. Using the testimonies of two survivors of the Holocaust, we sketch the components of a model for a GIS of place that allows for this theory of place to be visualized and analyzed. The model is, crucially, both multi‐scalar and sensitive to uncertainty, as a GIS of place needs to be able to zoom in and out of the different scales at which place is experienced, as well as capture both uncertain data and uncertainty as data. We see potential in the representations proposed for scaling up from the anecdotal to the general in the sense that any narrative can be grouped and classified according to places and scales as shown here. The challenge in developing a GIS of place along the lines we propose here is to design a new set of functionalities that can do so.  相似文献   

Distribution and population structure of the fish Helicolenus dactylopterus dactylopterus (Delaroche, 1809) in the Central Mediterranean (Southern Tyrrhenian Sea)     

Laura Pirrera  Teresa Bottari  Barbara Busalacchi  Daniela Giordano  Larissa Modica  Anna Perdichizzi  Francesco Perdichizzi  Adriana Profeta  & Paola Rinelli 《Marine Ecology》2009,30(S1):161-174

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Viscosity of a Teide phonolite in the welding interval     

D. Giordano  D. B. Dingwell  C. Romano 《Journal of Volcanology and Geothermal Research》2000,103(1-4)

The viscosity of a natural phonolitic composition with variable amounts of H₂O has been experimentally determined. The starting materials were crystal-free phonolitic glasses from Montaña Blanca, situated within the Las Cañadas caldera of Teide. Dry phonolitic melt viscosities were determined using concentric cylinder viscometry in the low viscosity range. The glassy quench products of these runs were then hydrated by high pressure synthesis in a piston–cylinder apparatus to generate a suite of samples with water contents ranging from 0.02 to 3.75 wt%. Samples thus hydrated were quenched rapidly and prepared (cut and polished) for the determination of water contents by infrared spectroscopy before and after experimental viscometry. The viscosities of the melts (dry and hydrated) were determined at 1 bar using a micropenetration technique. Samples were stable under the measurement conditions up to 3.75 wt% H₂O. Homogeneity of water content was confirmed by infrared spectroscopy and total water contents were calculated using absorptivity coefficients for compositions extremely close to that investigated here. The variation of viscosity as a function of water content and temperature can be described in the high viscosity interval of relevance to many welding processes by the non-Arrhenian expression:whereas the high viscosity range alone is adequately described by the Arrhenian expressionwhere η is the viscosity in Pa s, H₂O is the water content in wt% and T is the temperature in K.These results are particularly useful for the scaling of conditions extant during the welding of phonolitic products of Montaña Blanca. The welding of glassy phonolitic rocks is enhanced by the lower viscosity of these melts with respect to calcalkaline rhyolites. The ratio of viscosities of phonolitic to calcalkaline rhyolitic melts is a complex function of temperature and water content and reaches up to 10^4.5 at 0.1 wt% H₂O and 500°C. Abundant evidence of welding and remobilisation of pyroclastic and spatter products of Teide system volcanism are consistent with these experimental observations.  相似文献   

Reply to the comment by J. Hergt on the paper “Enriched mantle – Dupal signature in the genesis of the Jurassic Ferrar tholeiites from Prince Albert Mountains (Victoria Land, Antarctica)” by Antonini et al. (Contributions to Mineralogy and Petrology 136: 1–19, 1999)     

P. Antonini  E. M. Piccirillo  R. Petrini  L. Civetta  M. D'Antonio  G. Orsi 《Contributions to Mineralogy and Petrology》2000,139(2):245-249

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The Averno 2 fissure eruption: a recent small-size explosive event at the Campi Flegrei Caldera (Italy)   总被引：1，自引：0，他引：1  

Mauro Antonio Di Vito  Ilenia Arienzo  Giuseppe Braia  Lucia Civetta  Massimo D’Antonio  Valeria Di Renzo  Giovanni Orsi 《Bulletin of Volcanology》2011,73(3):295-320

The Averno 2 eruption (3,700 ± 50 a B.P.) was an explosive low-magnitude event characterized by magmatic and phreatomagmatic explosions, generating mainly fall and surge beds, respectively. It occurred in the Western sector of the Campi Flegrei caldera (Campanian Region, South Italy) at the intersection of two active fault systems, oriented NE and NW. The morphologically complex crater area, largely filled by the Averno lake, resulted from vent activation and migration along the NE-trending fault system. The eruption generated a complex sequence of pyroclastic deposits, including pumice fall deposits in the lower portion, and prevailing surge beds in the intermediate-upper portion. The pyroclastic sequence has been studied through stratigraphical, morphostructural and petrological investigations, and subdivided into three members named A through C. Member A was emplaced during the first phase of the eruption mainly by magmatic explosions which generated columns reaching a maximum height of 10 km. During this phase the eruption reached its climax with a mass discharge rate of 3.2 10⁶ kg/s. Intense fracturing and fault activation favored entry of a significant amount of water into the system, which produced explosions driven by variably efficient water-magma interaction. These explosions generated wet to dry surge deposits that emplaced Member B and C, respectively. Isopachs and isopleths maps, as well as areal distribution of ballistic fragments and facies variation of surge deposits allow definition of four vents that opened along a NE oriented, 2 km long fissure. The total volume of magma extruded during the eruption has been estimated at about 0.07 km³ (DRE). The erupted products range in composition from initial, weakly peralkaline alkali-trachyte, to last-emplaced alkali-trachyte. Isotopic data and modeling suggest that mixing occurred during the Averno 2 eruption between a more evolved, less radiogenic stored magma, and a less evolved, more radiogenic magma that entered the shallow reservoir to trigger the eruption. The early phases of the eruption, during which the vent migrated from SW to the center of the present lake, were fed by the more evolved, uppermost magma, while the following phases extruded the less evolved, lowermost magma. Integration of the geological and petrological results suggests that the Averno 2 complex eruption was fed from a dyke-shaped shallow reservoir intruded into the NE-SW fault system bordering to the west the La Starza resurgent block, within the caldera floor.  相似文献   

Columnar jointing in vapor-phase-altered,non-welded Cerro Galán Ignimbrite,Paycuqui, Argentina     

Heather M. N. Wright  Chiara Lesti  Raymond A. F. Cas  Massimiliano Porreca  José G. Viramonte  Chris B. Folkes  Guido Giordano 《Bulletin of Volcanology》2011,73(10):1567-1582

Columnar jointing is thought to occur primarily in lavas and welded pyroclastic flow deposits. However, the non-welded Cerro Galán Ignimbrite at Paycuqui, Argentina, contains well-developed columnar joints that are instead due to high-temperature vapor-phase alteration of the deposit, where devitrification and vapor-phase crystallization have increased the density and cohesion of the upper half of the section. Thermal remanent magnetization analyses of entrained lithic clasts indicate high emplacement temperatures, above 630°C, but the lack of welding textures indicates temperatures below the glass transition temperature. In order to remain below the glass transition at 630°C, the minimum cooling rate prior to deposition was 3.0 × 10⁻³–8.5 × 10⁻²°C/min (depending on the experimental data used for comparison). Alternatively, if the deposit was emplaced above the glass transition temperature, conductive cooling alone was insufficient to prevent welding. Crack patterns (average, 4.5 sides to each polygon) and column diameters (average, 75 cm) are consistent with relatively rapid cooling, where advective heat loss due to vapor fluxing increases cooling over simple conductive heat transfer. The presence of regularly spaced, complex radiating joint patterns is consistent with fumarolic gas rise, where volatiles originated in the valley-confined drainage system below. Joint spacing is a proxy for cooling rates and is controlled by depositional thickness/valley width. We suggest that the formation of joints in high-temperature, non-welded deposits is aided by the presence of underlying external water, where vapor transfer causes crystallization in pore spaces, densifies the deposit, and helps prevent welding.  相似文献   

Beyond water, beyond boundaries: spaces of water management in the Krishna river basin, South India     

Venot JP  Bharati L  Giordano M  Molle F 《The Geographical journal》2011,177(2):160-170

As demand and competition for water resources increase, the river basin has become the primary unit for water management and planning. While appealing in principle, practical implementation of river basin management and allocation has often been problematic. This paper examines the case of the Krishna basin in South India. It highlights that conflicts over basin water are embedded in a broad reality of planning and development where multiple scales of decisionmaking and non-water issues are at play. While this defines the river basin as a disputed "space of dependence", the river basin has yet to acquire a social reality. It is not yet a "space of engagement" in and for which multiple actors take actions. This explains the endurance of an interstate dispute over the sharing of the Krishna waters and sets limits to what can be achieved through further basin water allocation and adjudication mechanisms – tribunals – that are too narrowly defined. There is a need to extend the domain of negotiation from that of a single river basin to multiple scales and to non-water sectors. Institutional arrangements for basin management need to internalise the political spaces of the Indian polity: the states and the panchayats. This re-scaling process is more likely to shape the river basin as a space of engagement in which partial agreements can be iteratively renegotiated, and constitute a promising alternative to the current interstate stalemate.  相似文献