466 research outputs found
Fractures and lineaments of Sicily Island: Preliminary results on analog optical techniques
There are no author-identified significant results in this report
Results of Skylab investigation over Italy
The author has identified the following significant results. Multispectral high resolution photography of S190A was successfully applied to the detection of paleoriverbeds in flat lands. Results of SL-3 mission were compared to those of LANDSAT for two regional geological surveys (linear structures) on the islands of Sicily and Sardinia. On Sicily, the seasonal conditions were unfavorable for Skylab while LANDSAT played a major role in discovering long, unknown lineaments of great interest for the geodynamics of the area. On Sardinia, owing to the vegetation type and to the geomorphic conditions, the Skylab imagery was successfully employed to describe the network of linears, both regional and local. Results can be used to study the relationship between linears, actual fracturing and the occurrence of mineral deposits
Geogenic and atmospheric sources for volatile organic compounds in fumarolic emissions from Mt. Etna and Vulcano Island (Sicily, Italy)
In this paper, fluid source(s) and processes controlling the chemical composition of volatile organic compounds (VOCs) in gas discharges from Mt. Etna and Vulcano Island(Sicily, Italy) were investigated. The main composition of the Etnean and Volcano gas emissions is produced by mixing, to various degrees, of magmatic and hydrothermal components. VOCs are dominated by alkanes, alkenes and aromatics, with minor, though significant, concentrations of O-, S- and Cl(F)-substituted compounds. The main mechanism for the production of alkanes is likely related to pyrolysis of organic-matterbearing sediments that interact with the ascending magmatic fluids. Alkanes are then converted to alkene and aromatic compounds via catalytic reactions (dehydrogenation and dehydroaromatization, respectively). Nevertheless, an abiogenic origin for the light hydrocarbons cannot be ruled out. Oxidative processes of hydrocarbons at relatively high temperatures and oxidizing conditions, typical of these volcanic-hydrothermal fluids, may explain the production of alcohols, esters, aldehydes, as well as O- and S-bearing heterocycles. By comparing the concentrations of hydrochlorofluorocarbons (HCFCs) in the fumarolic discharges with respect to those of background air, it is possible to highlight that they have a geogenic origin likely due to halogenation of both methane and alkenes. Finally, chlorofluorocarbon (CFC) abundances appear to be consistent with background air, although the strong air contamination that affects the Mt. Etna fumaroles may mask a possible geogenic contribution for these compounds. On the other hand, no CFCs were detected in the Vulcano gases, which are characterized by low air contribution. Nevertheless, a geogenic source for these compounds cannot be excluded on the basis of the present data
Limestone assimilation by basaltic magmas: an experimental re-assessment and application to Italian volcanoes
International audienceThe results of an experimental study of limestone assimilation by hydrated basaltic magmas in the range 1050-1150°C, 0.1–500 MPa are reported. Alkali basalts doped with up to 19 wt% of Ca,Mg-carbonates were equilibrated in internally heated pressure vessels and the resulting phase relationships are described. The major effects of carbonate incorporation are: 1) generation of CO2-rich fluid phases; 2) change in liquidus phase equilibria; the crystallization of Ca-rich clinopyroxene is favored and the other phases (e.g. olivine, plagioclase), present in the absence of carbonate assimilation, are consumed. As a consequence of the massive clinopyroxene crystallization, the residual melt is strongly silica-depleted and becomes nepheline-normative. Compositional and mineralogical evolutions observed in Mt.Vesuvius eruptive products match those documented in our experiments with added carbonates, suggesting the possibility that carbonate assimilation increased during the last 25ka of activity. In Central-Southern Italy, carbonate assimilation at shallow levels probably superimposes on deeper source heterogeneities
Application of differential SAR interferometry for studying eruptive event of 22July 1998 at Mt.Etna
One of the main objectives of the project
“Development and application of remote sensing
methods for the monitoring of active Italian
volcanoes” is directed to an operational use of
differential interferometry as a tool for volcano
monitoring. A first step to achieve this goal is to
test commercial software in order to evaluate
the most suitable for the project purposes. For
testing software, SAR images collected by
ERS2 from May 98 to August 98, before and
after the strong eruptive event occurred on 22
July 98 at Voragine crater of Etna, have been
selected. The explosive event was classified
sub-plinian producing a 12 km high eruptive
column and lapilli fell on land as far as 70 km
south-eastward along the dispersal axis. Pre,
post and across event image pairs have been
processed. In particular the pair 13 May 98-22
July 98, 22 July 98-26 August 98, 13 May 98-26
August 98 are used for testing respectively pre,
post and across event. In first analysis, the
fringes in the differential products show a positive
elevation trend in the summit area of the
volcano. In particular, an increased of about 1,5
fringes in the period pre-event, and a decrement
of 1 fringe in the period post-event is observed.
This result is agreement whit field of deformation
expected in such kind of event, confirming
that the interferometric processing tool used id
suitable for the purpose of the project
Modelling ground deformations in volcanic areas by using SAR interferograms
The inversion problem dealt with is the
identification of the parameters of a magma-filled
dike which causes observable changes in
ground deformation data. It is supposed that
ground deformation data are measured by using
the SAR (Synthetic Aperture Radar)
Interferometry technique. The inversion
approach, which is carried out by a systematic
search technique based on the Simulated
Annealing (SA) optimization algorithm, guarantees
a high degree of accuracy. The results given
in the paper are supported by experiments carried
out using an interactive software tool developed
ad hoc, which allows both direct and
inverse modeling of SAR interferometric data
related to the opening of a crack at the beginning
and throughout a volcanic activity episode
Un test sulla percezione del rischio vulcanico
The perception of risk can provide valuable information for effective action to prevent and mitigate the effects of natural disasters and better development of educational strategies. With this goal has created a test to measure the perception of volcanic risk. What is the perception of volcanic risk by the people? How are "seen" the Italian volcanoes? These are the questions that have inspired this work
New aspects on the tectonic of the Alps and the Apennines revealed by ERTS-1 data
An analysis of the tectonic situation in the Alps and Apennine Mountains based on ERTS-1 imagery is presented. It is stated that the ERTS-1 imagery reveals connections between shearing systems of more than regional importance which could not be determined previously. The tracing of locally known fault distances by ERTS-1 imagery is discussed
A model of sulphur solubility for hydrous mafic melts: application to the determination of magmatic fluid compositions of Italian volcanoes
We present an empirical model of sulphur solubility that allows us to calculate f S2 if P, T, fO2 and the melt composition,
including H2O and S, are known. The model is calibrated against three main experimental data bases consisting
in both dry and hydrous silicate melts. Its prime goal is to calculate the f S2 of hydrous basalts that currently lack
experimental constraints of their sulphur solubility behaviour. Application of the model to Stromboli, Vesuvius, Vulcano
and Etna eruptive products shows that the primitive magmas found at these volcanoes record f S2 in the range
0.1-1 bar. In contrast, at all volcanoes the magmatic evolution is marked by dramatic variations in f S2 that spreads
over up to 9 orders of magnitude. The f S2 can either increase during differentiation or decrease during decompression
to shallow reservoirs, and seems to be related to closed versus open conduit conditions, respectively. The calculated
f S2 shows that the Italian magmas are undersaturated in a FeS melt, except during closed conduit conditions,
in which case differentiation may eventually reach conditions of sulphide melt saturation. The knowledge of f S2, fO2
and fH2O allows us to calculate the fluid phase composition coexisting with magmas at depth in the C-O-H-S system.
Calculated fluids show a wide range in composition, with CO2 mole fractions of up to 0.97. Except at shallow
levels, the fluid phase is generally dominated by CO2 and H2O species, the mole fractions of SO2 and H2S rarely exceeding
0.05 each. The comparison between calculated fluid compositions and volcanic gases shows that such an
approach should provide constraints on both the depth and mode of degassing, as well as on the amount of free fluid
in magma reservoirs. Under the assumption of a single step separation of the gas phase in a closed-system condition,
the application to Stromboli and Etna suggests that the main reservoirs feeding the eruptions and persistent volcanic
plumes at these volcanoes might contain as much as 5 wt% of a free fluid phase. Consideration of the magma
budget needed to balance the amounts of volatiles emitted in the light of these results shows that the amount of nonerupted
magma could be overestimated by as much as one order of magnitude
Total Fluxes of Sulfur Dioxide from the Italian Volcanoes Etna, Stromboli and Vulcano Measured by Differential Absorption LIDAR and Passive Differential Optical Absorption Spectroscopy
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