442 research outputs found
Dagli osservatóri agli Osservatòri
Quelli che hanno avuto il Vesuvio negli occhi, le loro storie di scienziati e di uomini, sono il tema di questo breve racconto. Storie di osservatóri, quindi, che hanno studiato il vulcano con passione, affascinati e sedotti da una montagna umbratile e solenne. Ma anche storie di Osservatòri, di contesti e tempi, ovvero, anch’essi mutevoli, in cui la scienza si organizza e si disorganizza per comprendere, prevedere, provvedere
Chronology of the 2007 eruption of Stromboli and the activity 1 of the Scientific Synthesis Group
On 27 February 2007, at 12.49 GMT, a new eruption of Stromboli took place with the effusion of a
15 lava flow from a fracture cutting the flank of the NE cone, which rapidly reached the sea. The eruption
16 had been heralded by an increase in the amplitude of tremor and flank movement since at least the 14th
17 of February. Short-term precursors were an increase in the rate of occurrence of small landslides within
18 the “Sciara del Fuoco” scar on the North-western flank of the volcano. A new effusive vent opened at
19 18.30 GMT on the Sciara del Fuoco at an height of 400 m asl. The new lava emission caused the
20 sudden termination of the summit flow and initiated a period of non-stationary lava outpouring which
21 ended on 2 April, 2007. The eruption has been characterized by a rapid decrease in the eruption rate
after the first days and subsequently by episodic pulse increases. On the 15th 22 of March, the increase in
23 lava outpouring, monitored by a thermal camera, heralded by 9 minutes the occurrence of a violent
24 paroxysmal explosion with the formation of an impulsive eruption column and the emission of small
25 pumices mingled with black scoriae. The pumice had a bulk composition similar to that of the lava and
26 of the black scoriae, but with a distinct lower content of phenocrysts. A similar feature has been
27 repeateadly observed during the major explosive paroxysms of Stromboli. Short term precursors of the
28 paroxysm were recorded by strainmeter and tiltmeter stations. The volcano monitoring activity has
29 been made by a joint team of researchers from the INGV sections of Catania, Napoli, Palermo and
30 Rome, along with researchers from the University of Florence, Pisa, Roma Tre, and Palermo. The
31 scientific activity was coordinated by a Synthesis Group made up by the responsibles of the different
32 monitoring techniques of INGV and Universities and by the volcanic experts of Commissione Nazionale Grandi Rischi of the Prime Minister Office (Civil Protection Department). 33 The group made a
34 daily evaluation of the state of the volcano and transmitted its recommendations to the Civil Protection
35 Department (DPC). Several prevention measures were adopted by DPC, the main of which were the
36 evacuation of the coast zone when strong acceleration of the Sciara del Fuoco slope motion (occurred
37 twice) could led to a dangerous tsunami by flank collapse (as last occurred on 30 December 2002) and
38 four days before the 15 March paroxysm when access was prohibited to the part of the volcano above
39 290m as
Geochemical Evidences that Unrest at Campi Flegrei Resurgent Caldera (Southern Italy) Is Due to Magma Emplacement and Degassing at Shallow Depth Plus Fluxing from a Deep-Seated Regional Body
Volcanic calderas are affected by unrest episodes usually
dominated by hybrid magmatic-hydrothermal system
dynamics. Unrest episodes can evolve to eruptions
of variable intensity, up to Plinian. Campi Flegrei caldera
(CFc) is a type-location for this kind of activity escalation.
CFc offers unique opportunity to join volcanological
information to a long record of geochemical parameters.
This allows understanding the role that magmatic
system plays on variations displayed by the hydrothermal
system. We model uneruptive unrest episodes as
driven by i) the shallow emplacement (~4 km depth) of
one volatile-rich magma batch ascending from a deep
(≥ 8 km) magmatic body of regional extent, ii) subsequent
gas separation with degassing driven by crystallization
and iii) fluxing from the deep magmatic body.
Our model matches three decades of geochemical constraints
from fumarole discharges, as well as data from melt inclusions of past CFc eruptions. Besides, magma
physical properties demanded for modeled degassing
conditions are in good agreement with existing geophysical
data. Our results open new perspectives to the
definition of unrest scenarios at highly-populated CFc,
as well as other resurgent calderas (e.g., Orsi et al., This
Assembly)
Magma dynamics during the 2007 Stromboli eruption (Aeolian Islands. Italy): mineralogical, geochemical and isotopic data
After the 6 month-long effusive event of 2002-2003, a new lava effusion occurred at Stromboli between 27
February and 2 April 2007. Despite the different durations, approximately the same volume of magma was
emitted in both eruptions, in the order of 107
m3
. A paroxysmal eruption occurred at the summit craters in
both the 2002–2003 and 2007 episodes, during which a significant amount of low porphyritic (LP), volatile-
rich magma was erupted. In both cases, the paroxysm did not interrupt the lava emission. Here, we present
compositional data, including texture, mineralogy, chemistry and Sr and Nd isotope ratios of bulk-rock,
groundmass and separated minerals of lavas erupted in 2007, together with chemistry and Sr and Nd isotope
composition of the pumices emitted during the 15 March paroxysm. As a whole, the lavas have the same
texture and chemistry that characterize the highly porphyritic (HP) products usually erupted at Stromboli
during normal Strombolian activity and effusive events. Compared to the previous HP products, the 2007
lavas show minor but systematic mineralogical and isotopic variations which are consistent with a modest
increase of the magma supply rate of the volcano. Compositional variations during the entire duration of the
event are very modest. Glass chemistry changes in lavas erupted in the second half of March can be explained
by theminormixing between the volatile-rich LPmagma rising through the shallowmagmatic systemduring the
15 March paroxysm and the degassed residing HP magma. A first conclusion of this study is that there is no
compositional evidence supporting major changes in the magma dynamics of the volcano accompanying the
effusive activity, as also suggested for the 2002–2003 event. The activity of Stromboli is controlled by a steady
state feeding system in which refilling, mixing, degassing and crystallization at shallow level continuously
operate,withmodest oscillations in themagma supply rate. Switching between normal Strombolian and effusive
activity is related to periods of relatively more vigorous refilling of the shallow system, leading to progressive
pressure increase in the upper conduits associated with only minor compositional variations in the erupted
products
The deep and magmatic degassing source of unrest episodes at Campi Flegrei caldera (southern Italy)
Volcanic calderas are affected by unrest episodes usually dominated by hybrid magmatic-hydrothermal system
dynamics. Unrest episodes can evolve to eruptions of variable intensity, up to Plinian. Campi Flegrei caldera
(CFc) is a type-location for this kind of activity escalation. CFc provides unique opportunity to build-up a volcanological
model in which geochemical, geological and geophysical data are interpreted together to understand
how degassing following magma emplacement drives the caldera resurgence. Uneruptive unrest episodes reflect
i) a sudden increase of the CO2 magmatic fraction following the shallow emplacement of one single volatile-rich
magma batch, ii) voluminous gas separation in a nearly single-step process, and iii), on longer times scales of 10-20
years, degassing driven by crystallization and deep gas fluxing. Our volcanological model matches three decades
of geochemical constraints from fumarole discharges, as well as data from melt inclusions of past CFc eruptions.
Besides, magma physical properties demanded for modeled degassing conditions are in good agreement with existing
geophysical data. Our results open new perspectives to the definition of unrest scenarios at highly-populated
CFc
Slab disruption, mantle circulation, and the opening of the Tyrrhenian basins
Plate tectonic history, geological, geochemical (element and isotope ratios), and
seismological (P-wave tomography and SKS splitting) data are combined with laboratory
modeling to present a three-dimensional reconstruction of the subduction history
of the central Mediterranean subduction. We fi nd that the dynamic evolution
of the Calabrian slab is characterized by a strong episodicity revealed also by the
discrete opening of the Tyrrhenian Sea. The Calabrian slab has been progressively
disrupted by means of mechanical and thermal erosion leading to the formation of
large windows, both in the southern Tyrrhenian Sea and in the southern Apennines.
Windows at lateral slab edges have caused a dramatic reorganization of mantle convection,
permitting infl ow of subslab mantle material and causing a complicated pattern
of magmatism in the Tyrrhenian region, with coexisting K- and Na-alkaline igneous
rocks. Rapid, intermittent avalanches of large amounts of lithospheric material at
slab edges progressively reduced the lateral length of the Calabrian slab to a narrow
(200 km) slab plunging down into the mantle and enhancing the end of the subduction
process
Sperm death and dumping in Drosophila
Mating with more than one male is the norm for females of many species. In addition to generating competition between the ejaculates of different males, multiple mating may allow females to bias sperm use. In Drosophila melanogaster, the last male to inseminate a female sires approximately 80% of subsequent progeny. Both sperm displacement, where resident sperm are removed from storage by the incoming ejaculate of the copulating male, and sperm incapacitation, where incoming seminal fluids supposedly interfere with resident sperm, have been implicated in this pattern of sperm use. But the idea of incapacitation is problematic because there are no known mechanisms by which an individual could damage rival sperm and not their own. Females also influence the process of sperm use, but exactly how is unclear. Here we show that seminal fluids do not kill rival sperm and that any 'incapacitation' is probably due to sperm ageing during sperm storage. We also show that females release stored sperm from the reproductive tract (sperm dumping) after copulation with a second male and that this requires neither incoming sperm nor seminal fluids. Instead, males may cause stored sperm to be dumped or females may differentially eject sperm from the previous mating
Chlorine as a geobarometer for alkaline magmas: Evidence from a systematic study of the eruptions of Mount Somma-Vesuvius
International audienceDefining the magma storage conditions of a volcanic system is a major goal in modern volcanology due to its direct implications for the style of a possible eruption, and thus on the associated risk of any crisis and the necessary management and mitigation strategies. Below 200 MPa and at equivalent depths, the strongly non-ideal behaviour of the H-CO -S-Cl-F system in the silicate melt causes unmixing of the fluid phase to form an H 2 O-rich vapour and a hydrosaline phase in equilibrium with the silicate melt, both responsible for buffering the chlorine (Cl) concentration. Following this equilibrium, the Cl concentration in melts may be used as a geobarometer for alkaline magmas. Systematic application of this method to the main explosive eruptions of Mount Somma-Vesuvius highlights two main magma ponding zones, at ~180–200 and ~100 MPa. At these pressures, the maximum pre-eruptive H 2 O contents for the different magma compositions can be estimated; the results obtained, largely in agreement with the current literature, therefore confirm the validity of the method. The Cl geobarometer may help scientists to define the variation of the magmatic reservoir location through time and thus provide strong constraints on pre-eruptive conditions, which are of utmost importance for volcanic crisis management
Geochemical and isotopic insights into the assembly, evolution and disruption of a magmatic plumbing system before and after a cataclysmic caldera-collapse eruption at Ischia volcano (Italy)
New geochemical and isotopic data on volcanic rocks spanning the period ~75–50 ka BP on Ischia volcano, Italy, shed light on the evolution of the magmatic system before and after the catastrophic, caldera-forming Monte Epomeo Green Tuff (MEGT) eruption. Volcanic activity during this period was influenced by a large, composite and differentiating magmatic system, replenished several times with isotopically distinct magmas of deep provenance. Chemical and isotopic variations highlight that the pre-MEGT eruptions were fed by trachytic/phonolitic magmas from an isotopically zoned reservoir that were poorly enriched in radiogenic Sr and became progressively less radiogenic with time. Just prior to the MEGT eruption, the magmatic system was recharged by an isotopically distinct magma, relatively more enriched in radiogenic Sr with respect to the previously erupted magmas. This second magma initially fed several SubPlinian explosive eruptions and later supplied the climactic, phonolitic-to-trachytic MEGT eruption(s). Isotopic data, together with erupted volume estimations obtained for MEGT eruption(s), indicate that >5–10 km3 of this relatively enriched magma had accumulated in the Ischia plumbing system. Geochemical modelling indicates that it accumulated at shallow depths (4–6 km), over a period of ca. 20 ka. After the MEGT eruption, volcanic activity was fed by a new batch of less differentiated (trachyte-latite) magma that was slightly less enriched in radiogenic Sr. The geochemical and Sr–Nd-isotopic variations through time reflect the upward flux of isotopically distinct magma batches, variably contaminated by Hercynian crust at 8–12 km depth. The deep-sourced latitic to trachytic magmas stalled at shallow depths (4–6 km depth), differentiated to phonolite through crystal fractionation and assimilation of a feldspar-rich mush, or ascended directly to the surface and erupted
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