http://hdl.handle.net/2122/201 Search the Channel search http://www.earth-prints.org/simple-search http://hdl.handle.net/2122/4155 Title: Volumetric observations during paroxysmal eruptions at Mount Etna: pressurized drainage of a shallow chamber or pulsed supply? <br/> <br/>Authors: Harris, A. J. L.; HIGP/SOEST, University of Hawaii, 2525 Correa Road, Honolulu, HI 96822, USA; Neri, M.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Catania, Catania, Italia <br/> <br/>Abstract: The October 17 to November 5, 1999, eruption of Mount Etna’s Bocca Nuova crater emplaced a V15U106 m3 flow field. The eruption was characterized by 11 paroxysmal events during which intense Strombolian and lava fountain activity fed vigorous channelized PaPa flows at eruption rates of up to 120 m3 s31. Each paroxysm lasted between 75 and 450 min, and was separated by periods of less intense Strombolian activity and less vigorous (610 m3 s31) effusion. Ground-based, satellite- and model-derived volumetric data show that the eruption was characterized by two periods during which eruption rates and cumulative volume showed exponential decay. This is consistent with a scenario whereby the system was depressurized during the first eruptive period (October 17^23), repressurized during an October 24 pause, and then depressurized again during the second period (October 25^28). The imbalance between the erupted and supplied volumes mean that the two periods involved the collection of 1.5^5.7U106 m3 and 1.2^ 3.6U106 m3, respectively, or an increase in the time-averaged supply to 11.6^13.6 m3 s31 and 12.5^14.9 m3 s31. Two models are consistent with the observed episodic fountaining, derived volumetric trends and calculated volume imbalance: a magma collection model and a pulsed supply model. In the former case, depressurization of a shallow reservoir cause the observed volumetric trends and foam collapse at the reservoir roof powers fountaining. In the pulsing case, variations in magma flux account for pressurization^depressurization and supply the excess volume. Increases in rise rate and volatile flux, coupled with rapid exsolution during ascent, trigger fountaining. Limiting equations that define critical foam layer volumes and magma rise rates necessary for Hawaiian-style fountaining favor the latter model. http://hdl.handle.net/2122/4139 Title: Comparison between different methodologies for detecting Radon in soil along an active fault: the case of the Pernicana fault system, Mt. Etna (Italy) <br/> <br/>Authors: Giammanco, S.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Catania, Catania, Italia; Immè, G.; Dipartimento diFisicaeAstronomia,Universita` degli StudidiCatania,viaS.Sofia,64,95123Catania,Italy; Mangano, G.; Dipartimento diFisicaeAstronomia,Universita` degli StudidiCatania,viaS.Sofia,64,95123Catania,Italy; Morelli, D.; Dipartimento diFisicaeAstronomia,Universita` degli StudidiCatania,viaS.Sofia,64,95123Catania,Italy; Neri, M.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Catania, Catania, Italia <br/> <br/>Abstract: Three different methodologies were used to measure Radon (222Rn) in soil, based on both passive and active detection system. The first technique consisted of Solid State Nuclear Track Detectors (SSNTD), CR-39 type, and allowed integrated measurements. The second one consisted of a portable device for short time measurements. The last consisted of a continuous measurement device for extended monitoring, placed in selected sites. Soil 222Rn activity was measured together with soil Thoron (220Rn) and soil carbon dioxide (CO2) efflux, and it was compared with the content of radionuclides in the rocks. Two different soil gas horizontal transects were investigated across the Pernicana fault system (NE flank of Mount Etna), from November 2006 to April 2007. The results obtained with the three methodologies are in a general agreement with each other and reflect the tectonic settings of the investigated study area. The lowest 222Rn values were recorded just on the fault plane, and relatively higher values were recorded a few tens of meters from the fault axis on both of its sides. This pattern could be explained as a dilution effect resulting from high rates of soil CO2 efflux. Time variations of 222Rn activity were mostly linked to atmospheric influences, whereas no significant correlation with the volcanic activity was observed. In order to further investigate regional radon distributions, spot measurements were made to identify sites having high Rn emissions that could subsequently be monitored for temporal radon variations.. SSNTD measurements allow for extended-duration monitoring of a relatively large number of sites, although with some loss of temporal resolution due to their long integration time. Continuous monitoring probes are optimal for detailed time monitoring, but because of their expense, they can best be used to complement the information acquired with SSNTD in a network of monitored sites. http://hdl.handle.net/2122/3896 Title: The Frontier Mountain meteorite trap (Antarctica) <br/> <br/>Authors: Folco, L.; Museo Nazionale dell'Antartide, Università di Siena, via Laterina 8, I-53100 Siena, Italy; Capra, A.; DAU, Politecnico di Bari, via Orabona 4, I-70125 Bari, Italy; Chiappini, M.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia; Frezzotti, M.; ENEA-GEM-CLIM, CR Casaccia, via Anguillarese 301, Santa Maria di Galeria, I-00060 Roma, Italy; Mellini, M.; Dipartimento di Scienze della Terra, Università di Siena, via Laterina 8, I-53100 Siena, Italy; Tabacco, I. E.; Dipartimento di Scienze della Terra, Università di Milano, via Cicognara 7, 20129 Milano, Italy <br/> <br/>Abstract: The Frontier Mountain blue ice field is an important Antarctic meteorite trap which has yielded 472 meteorite specimens since its discovery in 1984. Remote sensing analyses and field campaigns from 1993 to 1999 have furnished new glaciological data on ice flow, ice thickness, bedrock topography, ice ablation and surface mass transport by wind, along with detailed descriptions of the field situation at the trap. This solid set of data combined with an updated meteorite distribution map and terrestrial ages available from literature allows us to better describe the nature of the concentration mechanism. In particular, we observe that the meteorite trap forms in a blue ice field (1) located upstream of an absolute and a shallow sub-ice barriers; (2) characterized by compressive ice flow with horizontal velocities decreasing from 100 to <10 cm/year on approaching the obstacle; (3) undergoing mean ablation rates of 6.5 cm/year; (4) nourished by a limited snow accumulation zone extending ∼20 km upstream of the blue ice area. We also draw the following conclusions: (1) the origin of the meteorite trap can be explained according to the present-day glaciological situation; (2) the meteorite concentration develops according to the general principles of the "ice flow model"; (3) the accumulation model can be described as "stagnant ice or slow-moving ice against an absolute and submerged barriers", according to the descriptive schemes present in literature; (4) the Frontier Mountain ice field is an effective trap for meteorites weighing more than ∼200 g; for smaller masses, the combination of wind and glacial drift may remove meteorites in less than a few tens of thousands of years; (5) although the activation age of the Frontier Mountain trap is not yet constrained, we infer that one of the most important findsites may be as old as 50 ka, predating the last glacial maximum. http://hdl.handle.net/2122/2949 Title: Investigation of the active Celano–L’Aquila fault system, Abruzzi <br/> <br/>Authors: Salvi, S.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione CNT, Roma, Italia; Cinti, F. R.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma1, Roma, Italia; Colini, L.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione CNT, Roma, Italia; D’Addezio, G.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia; Doumaz, F.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione CNT, Roma, Italia; Pettinelli, E.; Dipartimento di Fisica ‘E. Amaldi’, Università degli Studi ‘Roma Tre’, Rome, Italy <br/> <br/>Abstract: We studied fault scarps along the northern sector of the Celano–L’Aquila fault system in the Abruzzi region (central Apennines). Up to ∼9.5 km long, 3 m high, fault scarp traces mark the slope foot of ridgetop valleys at Mt Ocre range. In order to provide direct evidence of the deformation history of these scarps, we initiated geomorphic, ground-penetrating radar (GPR)and trenching investigations. GPR investigations yielded subsurface stratigraphic features of the scarp zones, and determined the locations for trenching sites. A total of five trenches were excavated at two different sites. Structural and stratigraphic analysis of the trench exposures combined with historical considerations, showed three faulting events between 5620 BC and 1300 AD; the most recent of them occurred after 1690 BC. Each of these events produced an estimated minimum vertical displacement ranging between 0.3 and 0.5 m. Our interpretation is that the Mt Ocre fault branch represents the northernmost surface expression of a single 35 km long seismogenic structure associated with M ∼7 earthquakes. Any attempt to estimate the seismic hazard in the area must consider the presence of this important source.