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Soriano C.C.,CSIC - Institute of Earth Sciences Jaume Almera | Giordano G.,Third University of Rome | Riggs N.R.,Northern Arizona University | Porreca M.,Italian National Institute of Geophysics and Volcanology | And 7 more authors.
Italian Journal of Geosciences

The geologic map of the Neogene Cabo de Gata volcanic zone is presented together with a comprehensive volcanic stratigraphy and structure based on logging, correlation and mapping. Volcanic rocks are interbedded with sedimentary rocks throughout the Cabo de Gata volcanic zone. The volcano-sedimentary succession of Cabo de Gata has been divided into formations according to lithology, age, composition and stratigraphic position. The contacts between sedimentary units and volcanic units and between formations are unconformities. Sedimentary units were deposited during periods of volcanic repose. The depositional environment of volcanism in Cabo de Gata is characterized as shallow-water submarine to emergent based on lithofacies of volcanic rocks and on fossil content and sedimentary structures of sedimentary rocks. The eruptive style in Cabo de Gata is dominantly effusive, although small-volume explosive eruptions due to magma-water interaction processes and to explosions of lava flow and domes complexes occurred. © 2014 Societa Geologica Italiana, Roma. Source

Diano G.,University RomaTre | Bonamico A.,Parco Regionale dellAppia Antica | Giordano G.,University RomaTre
Special Publications of IAVCEI

The quiescent Colli Albani volcano is composed of overlapping edifices, with each showing changes in volcanic style over the 600-ka history of the volcanic field. The edifices and changes in eruption style through time are indicated in the field by the major unconformities, which have been identified from surface geology and borehole stratigraphies. This reconstruction of the major unconformities allows for three-dimensional geometric reconstruction of the relevant rock packages, computation of the deposit volumes, and evaluation of syn-volcanic tectonic or volcano-tectonic activity. Furthermore, some rock packages, such as the Pisolitic Tuffs, the Tufo Lionato and the Albano maar deposits, are characterized by relatively low permeability, and are therefore essential for modelling of the hydrogeological circulation and flow of volcanic gases. The reconstructions of the isopachs of the three main caldera-forming ignimbrites erupted between 460 and 355 ka have allowed the calculation of their minimum preserved extracaldera volumes at 59 km3 (Pozzolane Rosse). 20 km3 (Pozzolane Nere) and 30 km3 (Villa Senni Fm.) respectively. The total volume of volcanic deposits erupted after the last caldera collapse (<355 ka) is calculated as 34.7 km3. The preserved deposits of the most recent Albano polygenetic maar have been calculated to be 0.9 km3. The total minimum deposit volume of the Colli Albani volcano is 208.1 km3. This volume does not include the intracaldera ignimbrite volumes which may add some 80 km3 to the total volume. Source

Tallini M.,University of LAquila | Di Leo A.,Istituto Comprensivo Falcone e Borsellino | Rossetti C.,Servizio Comunicazione Ed Educazione Ambientale | Berardi F.,Parco Regionale dellAppia Antica
Water Science and Technology: Water Supply

Although the Almone River, which runs for 6 km between the Roman Via Latina and Via Appia, inside the present Appian Way Regional Park, is a short tributary of the Tiber River, it played a crucial role among the cults for protection of the ancient city of Rome: the rite of lavatio (a ritual washing) of the lithic symbol of the Great Mother-Cybele goddess from Pessinus (the present village of Ballihisar, southwest of Ankara, Turkey) in the cold and fast-flowing water of the Almone River. In later times, the Almone River lost its sacrality and its flowing water got a new useful and hydraulic meaning. So it deeply characterised the local area and human settlements, enhancing their artisanal potential, especially in the Middle Ages and the Renaissance and in part until the 20th century. The river area has records of water mills and 'valche' (from the Longobard word walkan, rolling), i.e. wool-fulling mills. One of the latter (converted into a paper mill in the early 20th century) has been restored and is now used as the headquarters and visitors' centre of the Appian Way Regional Park, of which the Almone is one of the key attractions for its tourist, natural, historical and cultural value. © IWA Publishing 2013. Source

Giordano G.,Third University of Rome | De Benedetti A.A.,Third University of Rome | Bonamico A.,Parco Regionale dellAppia Antica | Ramazzotti P.,Third University of Rome | Mattei M.,Third University of Rome
Earth-Science Reviews

The Quaternary Roman Volcanic Province extends for over 200km along the Tyrrhenian margin of the Italian peninsula and is composed of several caldera complexes with significant associated geothermal potential. In spite of the massive programs of explorations conducted by the then state-owned ENEL and AGIP companies between the 1970s and 1990s, and the identification of several high enthalpy fields, this resource remains so far unexploited, although it occurs right below the densely populated metropolitan area of Roma capital city. The main reason for this failure is that deep geothermal reservoirs are associated with fractured rocks, the secondary permeability of which has been difficult to predict making the identification of the most productive volumes of the reservoirs and the localisation of productive wells uncertain. As a consequence, almost half of the many exploration deep bore-holes drilled in the area reached a dry target. This work reviews available data and re-assesses the geothermal potential of caldera-related systems in Central Italy, by analysing in detail the case of the Colli Albani caldera system, the closest to Roma capital city. A GIS based approach identifies the most promising reservoir volumes for geothermal exploitation and uses an improved volume method approach for the evaluation of geothermal potential. The approach is based on a three dimensional matrix of georeferenced spatial data; the A axis accounts for the modelling of the depth of the top of the reservoirs based on geophysical and direct data; the B axis accounts for the thermal modelling of the crust (i.e. T with depth) based on measured thermal gradients. Both A and B data are necessary but not sufficient to identify rock volumes actually permeated by geothermal fluids in fractured reservoirs. We discuss the implementation of a C axis that evaluates all surface data indicating permeability in the reservoir and actual geothermal fluid circulation. We consider datasets on: i) distribution and density of tectonic lineaments; ii) temperature and iii) electric conductivity of shallow groundwaters; iv) partial pressure of dissolved CO2 in shallow groundwaters. The geothermal potential of Colli Albani and the implications for caldera-related geothermal systems in Central Italy are discussed based on the role of the geometry and structure of reservoirs in relationship with volcano-tectonic structures and deep geothermal fluid migration paths. © 2013 Elsevier B.V. Source

Giordano G.,Third University of Rome | Carapezza M.L.,Italian National Institute of Geophysics and Volcanology | Monica G.D.,Third University of Rome | Todesco M.,Italian National Institute of Geophysics and Volcanology | And 17 more authors.
Journal of Volcanology and Geothermal Research

A hazardous gas eruption from two very close shallow boreholes occurred near the Fiumicino International Airport of Roma (Italy) from August to December 2013. The erupted gas was mostly CO 2 of deep origin and gas output was high and sustained over time reaching values of nearly 20 t day•1. After 3 months, the gas flux was still above 5 t day•1 and was only stopped in December 2013 by long and expensive works of closure of the boreholes. The gas eruption was uncommon as being associated with the building of two mud volcanoes. This style of sustained deep CO 2 eruptions contrasts with the more common short-lived eruptions of shallow biogenic methane-dominated gas pockets. In this work, we present the chronology of the event, the results of geological, geochemical, and geophysical monitoring and a numerical modeling. We propose that the August-December 2013 sustained and prolonged event does not relate to the simple degassing of a shallow, isolated pocket of gas. On the contrary, it reflects very specific conditions in a shallow reservoir (hosted in a 10 m thick gravel layer at –40 m within the Tiber river delta deposits), related to the interplay between the total pressure and the fraction of free CO 2 initially present, across very narrow value ranges around 0.59 MPa and 0.18, respectively. The coexistence of short-lived and long-lived eruptions from the same reservoir suggest that these conditions are not achieved everywhere in the gas reservoir, despite its homogeneous properties. This consideration implies either a pressure compartmentalization of the reservoir, or the occurrence of a transient, possibly associated with an impulsive release of gas from greater depths. The involvement of deeper and larger gas reservoirs connected along faults is evidenced by geophysical investigations. This conceptual model bears significant implications for gas hazard studies © 2016 Elsevier B.V. Source

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