575 research outputs found
Carbon Dioxide Diffuse Emission from the Soil at Vesuvio and Campi Flegrei (Pozzuoli): Ten Years of Observations
Carbon dioxide flux from the soil is regularly monitored
in selected areas of Vesuvio and Solfatara (Campi Flegrei,
Pozzuoli) with the main aim of investigating if the
surface phenomena could provide information about
the processes occurring at depth. Surveyed areas include
15 fixed points around the rim of Vesuvio and 71
fixed points in the floor of Solfatara crater, where soil
CO2 flux is measured since 1998, at least once a month.
In addition, two automatic permanent stations, located
at Vesuvio and Solfatara, continually measure the CO2
flux and some environmental parameters that can potentially
influence the CO2 diffuse degassing.
We analysed, with statistical procedures, the feature
of the acquired signals, evaluating the spatial and temporal
variations of the CO2 degassing process.
Series acquired by continuous stations are characterized
by an annual periodicity that is related to the
typical periodicities of some meteorological parameters
(e.g., air temperature, air humidity, etc.). Such a kind of
signal permits to define the āreferenceā level of the CO2
degassing process that diffusely affects the flanks and
the base of the volcanoes.
Conversely, series of CO2 flux data arising from periodic
measurements over the arrays of Vesuvio and
Solfatara, are less dependent on external factors such
as meteorological parameters, local soil properties (porosity,
hydraulic conductivity) and topographic effects
(high or low ground). Therefore we argue that the longterm
trend of this signal contains the ābestā possible
representation of the endogenous signal related to the
upflow of deep hydrothermal fluids. At Vesuvio and Solfatara,
the variations of these series have shown some correspondence with other physical changes of the volcanic systems
Temperature and pressure gas geoindicators at the Solfatara fumaroles (Campi Flegrei)
Long time series of fluid pressure and temperature within a hydrothermal
system feeding the Solfatara fumaroles are investigated here, on the basis
of the chemical equilibria within the CO2-H2O-H2-CO gas system. The
Pisciarelli fumarole external to Solfatara crater shows an annual cycle of
CO contents that indicates the occurrence of shallow secondary processes
that mask the deep signals. In contrast, the Bocca Grande and Bocca Nova
fumaroles located inside Solfatara crater do not show evidence of
secondary processes, and their compositional variations are linked to the
temperatureāpressure changes within the hydrothermal system. The
agreement between geochemical signals and the ground movements of the
area (bradyseismic phenomena) suggests a direct relationship between the
pressurization process and the ground uplift. Since 2007, the gas
geoindicators have indicated pressurization of the system, which is most
probably caused by the arrival of deep gases with high CO2 contents in
the shallow parts of the hydrothermal system. This pressurization process
causes critical conditions in the hydrothermal system, as highlighted by
the increase in the fumarole temperature, the opening of new vents, and
the localized seismic activity. If the pressurization process continues with
time, it is not possible to rule out the occurrence of phreatic explosions
Radon in active volcanic areas of southern Italy
The radiogenic gas radon is considered a valid precursor of events like eruptions and earthquakes. We are monitoring the variations in time of this gas in soils and in waters of many active volcanic areas of Southern Italy. The greatest differences in Rn content of the investigated volcanic areas are: Ischia and Campi Flegrei have more Rn than Vesuvio and Vulcano, both in soils and in waters. The
thermalized waters of Ischia are enriched in Rn 15 times with respect to soils, while in the other areas soils and underground waters have comparable Rn contents
Geochemical monitoring integrated in a real time hydrological network
Hydrological data relative to springs and water wells collected by the Hydrografic National Service in Naples indicate that some anomalies can be correlated with the seismic activity in Southern Apennines. In this paper we report some hydrological anomalies for the November 23, 1980 earthquake and suggest that an improvement of the hydrometeorological network of the Hydrographic National
Service can reveal geochemical and hydrological anomalies before the earthquakes
Long time-series of chemical and isotopic compositions of Vesuvius fumaroles: evidence for deep and shallow processes
Long time-series of chemical and isotopic compositions of Vesuvius
fumaroles were acquired in the framework of the volcanic surveillance in
the 1998-2010 period. These allow the identification of processes that
occur at shallow levels in the hydrothermal system, and variations that are
induced by deep changes in volcanic activity. Partial condensation
processes of fumarolic water under near-discharge conditions can explain
the annual 18O and deuterium variabilities that are observed at Vesuvius
fumaroles. Significant variations in the chemical compositions of
fumaroles occurred over the 1999-2002 period, which accompanied the
seismic crisis of autumn 1999, when Vesuvius was affected by the most
energetic earthquakes of its last quiescence period. A continuous increase
in the relative concentrations of CO2 and He and a general decrease in the
CH4 concentrations are interpreted as the consequence of an increment in
the relative amount of magmatic fluids in the hydrothermal system. Gas
equilibria support this hypothesis, showing a PCO2 peak that culminated in
2002, increasing from values of ~40 bar in 1998 to ~55-60 bar in 2001-
2002. We propose that the seismic crisis of 1999 marked the arrival of the
magmatic fluids into the hydrothermal system, which caused the observed
geochemical variations that started in 1999 and culminated in 2002
New insights into Mt. Vesuvius hydrothermal system and its dynamic based on a critical review of seismic tomography and geochemical features
The seismic velocity and attenuation tomography images, calculated inverting
respectively P-wave travel times and amplitude spectra of local
VT quakes at Mt. Vesuvius have been reviewed and graphically represented
using a new software recently developed using Mathematica8TM.
The 3-D plots of the interpolated velocity and attenuation fields obtained
through this software evidence low-velocity volumes associated with high
attenuation anomalies in the depth range from about 1 km to 3 km below
the sea level. The heterogeneity in the distribution of the velocity and attenuation
values increases in the volume centred around the crater axis
and laterally extended about 4 km, where the geochemical interpretation
of the data from fumarole emissions reveals the presence of a hydrothermal
system with temperatures as high as 400-450Ā°C roughly in the same
depth range (1.5 km to 4 km). The zone where the hydrothermal system
is space-confined possibly hosted the residual magma erupted by Mt. Vesuvius
during the recent eruptions, and is the site where most of the seismic
energy release has occurred since the last 1944 eruption
Long Time Series Of Fumarolic Compositions At Volcanoes: The Key To Understand The Activity Of Quiescent Volcanoes
Long time series of fumarolic chemical and isotopic
compositions at Campi Flegrei, Vulcano, Panarea,
Nisyros and Mammoth volcanoes highlight the occurrence
of mixing processes among magmatic and hydrothermal
fluids. At Campi Flegrei temperatures of
about 360Ā°C of the hydrothermal system are inferred by
chemical and isotopic geoindicators. These high temperatures
are representative of a deep zone where magmatic
gases mix with hydrothermal liquids forming the gas plume feeding the fumaroles. Similar mixing processes
between magmatic fluids and a hydrothermal
component of marine origin have been recognized at
Vulcano high temperature fumaroles. In both the system
a typical āandesiticā water type composition and high
CO2 contents characterizes the magmatic component.
Our hypothesis is that pulsing injections of these CO2-
rich magmatic fluids at the bottom of the hydrothermal
systems trigger the bradyseismic crises, periodically
affecting Campi Flegrei, and the periodical volcanic
unrest periods of Vulcano. At Campi Flegrei a strong
increase of the fraction of the magmatic component
marked the bradyseismic crisis (seismicity and ground
uplift) of 1982-84 and four minor episodes occurred in
1989, 1994 and 2000 and 2006. Increases of the magmatic
component in the fumaroles of Vulcano were recorded
in 1979-1981, 1985, 1988, 1996, 2004 and 2005
concurrently with anomalous seismic activity. Physicalnumerical
simulations of the injection of hot, CO2 rich
fluids at the base of a hydrothermal system, asses the
physical feasibility the process. Ground deformations,
gravitational anomalies and seismic crisis can be well
explained by the complex fluid dynamic processes
caused by magma degassing episodes. Sporadic data
on the fumaroles of other volcanoes, for example Panarea,
Nisyros (Greece), Mammoth (California), suggest
that magma degassing episodes frequently occur in
dormant volcanoes causing volcanic unrest processes
not necessarily linked to magma movement but rather
to pulsating degassing processes from deep pressurized,
possibly stationary, magma bodies
Carbon dixide emission in Italy: Shallow crustal sources or subduction related fluid recycling?
Anomalous non-volcanic CO2 release in central and
southern Italy has been highlighted by ten years of detailed
investigations on Earth degassing processes. Two regional
degassing structures are located in the Tyrrhenian sector
where more then 200 emissions of CO2 are located and has
been recently included in the first web based catalogue of
degassing sites (http://googas.ov.ingv.it). The total amount of
CO2 released by the two structures were evaluated to be >
2Ć1011 mol a-1 ( >10% of the estimated global volcanic CO2
emission). The anomalous flux of CO2 suddenly disappears in
the Apennine in correspondence of a narrow band where most
of the Italian seismicity concentrates. Here, at depth, the gas
accumulates in crustal traps generating CO2 overpressurised
reservoirs. These overpressured structures are, in our opinion,
one of the main cause of Apennine earthquake activation
processes. The results of these investigations suggested that
Earth degassing in Italy may have an active primary role in the
geodynamics of the region. What is the origin of gas? The
large extension of the degassing structures and petrologic data
suggested that the main source of gas is a mantle
metasomatised by the fluids produced in the subdacted slabs.
However, has been also hypothesised the presence of localised
crustal source of the gas. This matter will be discussed on the
base of unpublished isotopic data of the main gas emissions
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