182 research outputs found
The Catania 1669 lava eruptive crisis: simulation of a new possible eruption
SCIARA (Smart Cellular Interactive Automata for modeling the Rheology of Aetnean lava flows,
to be read as âsheaârahâ), our first two-dimensional Cellular Automata model for the simulation of
lava flows, was tested and validated with success on several lava events like the 1986/87 Etnean
eruption and the last phase of the 1991/93 Etnean one. Real and simulated events are satisfying
within limits to forecast the surface covered by the lava flow. Moreover, improved versions have
been adopted in testing other real lava flows of Mount Etna and of Reunion Island (Indian Ocean).
The model has been applied with success in the determination of risk zones in the inhabited
areas of Nicolosi, Pedara, S. Alfio and Zafferana (Sicily). The main goal of the present work has
been the verification of the effects, in volcanic risk terms, in the Etnean area from Nicolosi to
Catania, of a eruptive crisis similar to the event that occurred in 1669, as if the episode would
happen nowadays.
Catania has been severely interested in some major Etnean events in history, the most famous
one being, namely, the 1669 eruption, involving 1 km3 of lava during 130 days. The simulation of
lava tubes and the usage of different histories within the experiments have been crucial in the
determination of a new risk area for Catania. In fact, simulations carried out without the introduction
of lava tubes, never involved the city, proving the fact that lava tubes, played a fundamental role in
the 1669 Catania lava crisis
Volcanic and seismic activity at Stromboli preceding the 2002-03 eruption
Regular surveys with a PM695 FLIR thermal imaging camera from both the ground and from helicopter were conducted on Stromboli from October 2001. These measurements allow us to (i) examine changes in morphology of the summit craters produced by paroxystic explosions and (ii) track the increasing level of magma within the conduits of Stromboli that preceded and led to the 2002/03 effusive eruption. Two geophysical surveys in May and September/October 2002 demonstrated a clear increasing trend in the amplitude of VLP events, consistent with the presence of a higher magma column above the VLP source region. The observed increase in magma level was probably induced by an increase in the pressure of the magma feeding system at Stromboli, controlled by regional tectonic stress. The increased magma level induced strain on the uppermost part of the crater terrace, allowing an increase in soil permeability and therefore CO2 and Radon degassing. Eventually this stress caused the northeast flank of the craters to fracture, allowing lava to flood out at high effusion rates on 28th December. Regular surveys with the thermal imaging camera, combined with geophysical monitoring, are an invaluable addition to the armory of volcanologists attempting to follow the evolution of activity on active volcanoes
The initial phases of the 2008-2009 Mt. Etna eruption: a multi-disciplinary approach for hazard assessment
Between 2007 and early 2008, the INGV monitoring networks on Etna volcano recorded a
recharging phase that climaxed with a new effusive eruption on 13 May 2008, and lasted about 14
months. A dike-forming intrusion was accompanied by a violent seismic swarm, with more than 230
events recorded in the first six hours, the largest being ML = 3.9. In the meanwhile, marked ground
deformation was recorded by the permanent tilt and GPS networks, and sudden changes in the summit
area were detected by five continuously recording magnetic stations. Poor weather conditions did not
allow direct observation of the eruptive events, but important information was provided by infrared
satellite images that detected the start of lava fountains from the eruptive fissure, feeding a lava flow.
This flow spread within the Valle del Bove depression, covering 6.4 km on the south-eastern flank of
the volcano in a few hours. The seismicity and deformation pattern indicated that the dike-forming
intrusion was propagating northwards. It produced a dry fracture field, which generated concern for the
possibility that the eruptive fissures could expand downslope towards populated areas. Monitoring and
modeling of the multi-disciplinary data, together with the simulations of ash dispersal and lava flows,
allowed us both to infer the eruptive mechanisms and provide a correct interpretation of the ongoing
phenomena, furnishing useful information for civil defense purposes. We describe how this approach of
feedback between monitoring and research provides critical support to risk evaluation
Major eruptive style changes induced by structural modifications of a shallow conduit system: the 2007â2012 Stromboli case
Stromboli is known for its mild, persistent explosive
activity from the vents located within the summit crater
depression at the uppermost part of the Sciara del Fuoco (SdF)
depression. Effusive activity (lava flows) at this volcano normally
occurs every 5â15 years, involving often the opening of
eruptive fissures along the SdF, and more rarely overflows
from the summit crater. Between the end of the 2007 effusive
eruption and December 2012, the number of lava flows inside
and outside the crater depression has increased significantly,
reaching a total of 28, with an average of 4.8 episodes per year.
An open question is why this activity has become so frequent
during the last 6 years and was quite rare before. In this paper,
we describe this exceptional activity and propose an interpretation
based on the structural state of the volcano, changed
after the 2002â2003 and even more after the 2007 flank
effusive eruption. We use images from the Stromboli fixed
cameras network, as well as ground photos, plume SO2 and
CO2 fluxes released by the summit crater, and continuous
fumarole temperature recording, to unravel the interplay
between magma supply, structural and morphology
changes, and lava flow output. Our results might
help forecast the future behaviour and hazard at
Stromboli and might be applicable to other openconduit
volcanoes.partially supported by the Project
INGV-DPC Paroxysm V2/03, 2007â2009 funded by the Istituto
Nazionale di Geofisica e Vulcanologia and the Italian Civil ProtectionPublished8413V. Dinamiche e scenari eruttiviJCR Journalrestricte
Etna 2004â2005: An archetype for geodynamically-controlled effusive eruptions
The 2004â05 eruption of Etna was characterised by outpouring of degassed lava from two vents within Valle del Bove. After three months of eruption lava volumes were estimated to be between 18.5 and 32 Ă 106 m3, with eruption rate between 2.3 and 4.1 m3/s. Petrological analyses show that magma is resident in the shallow plumbing system, emplaced during the last South-East Crater activity. SO2 flux data show no increase at the onset of the eruption and SO2/HCl ratios in gas emitted from the eruptive fissure are consistent with a degassed magma. No seismic activity was recorded prior to eruption, unlike eruptions observed since the 1980's. The purely effusive nature of this eruption, fed by a degassed, resident magma and the fracture dynamics suggest that magmatic overpressure played a limited role in this eruption. Rather, lateral spreading of Etna's eastern flank combined with general inflation of the edifice triggered a geodynamically-controlled eruption.Published1-4partially_ope
An unloading foam model to constrain Etnaâs 11â13 January 2011 lava fountaining episode
The 11â13 January 2011 eruptive episode at Etna volcano occurred after several months
of increasing ash emissions from the summit craters, and was heralded by increasing
SO2 output, which peaked at âŒ5000 megagrams/day several hours before the start of the
eruptive activity. The eruptive episode began with a phase of Strombolian activity from a pit
crater on the eastern flank of the SEâCrater. Explosions became more intense with time
and eventually became transitional between Strombolian and fountaining, before moving
into a lava fountaining phase. Fountaining was accompanied by lava output from the lower
rim of the pit crater. Emplacement of the resulting lava flow field, as well as associated lava
fountainâ and Strombolianâphases, was tracked using a remote sensing network comprising
both thermal and visible cameras. Thermal surveys completed once the eruptive episode
had ended also allowed us to reconstruct the emplacement of the lava flow field. Using a high
temporal resolution geostationary satellite data we were also able to construct a detailed
record of the heat flux during the fountainâfed flow phase and its subsequent cooling. The
dense rock volume of erupted lava obtained from the satellite data was 1.2 Ă 106 m3; this
was emplaced over a period of about 6 h to give a mean output rate of âŒ55 m3 sâ1. By
comparison, geologic data allowed us to estimate dense rock volumes of âŒ0.85 Ă 106 m3
for the pyroclastics erupted during the lava fountain phase, and 0.84â1.7 Ă 106 m3 for
lavas erupted during the effusive phase, resulting in a total erupted dense rock volume of
1.7â2.5 Ă 106 m3 and a mean output rate of 78â117 m3 sâ1. The sequence of events and
quantitative results presented here shed light on the shallow feeding system of the volcano
Combining thermal imaging with photogrammetry of an active volcano using UAV : an example from Stromboli, Italy
The authors would like to thank the Istituto Nazionale di Geofisica e Vulcanologia â Sezione di Catania (INGVâCT) for granting permission to conduct the UAV surveys over the Stromboli volcano. This work was supported by the School for Early Career Researchers at the University of Aberdeen, UK. Dougal Jerram is partly funded through a Norwegian Research Council Centres of Excellence project (project number 223272, CEED). The team would like to thank Angelo Cristaudo for logistical help during the fieldwork efforts on Stromboli.Peer reviewedPostprin
The eruptive activity of 28 and 29 December 2002
At 18:20 of 28 December 2002 an eruptive vent opened on the NE flank of the Sciara del Fuoco at 600 m asl, marking the onset of the 2002-2003 eruptive crisis of Stromboli volcano. The first eruptive hours were characterized by mild spattering and effusive activity from the new vent and the summit vent at crater 1. Gravitational instability processes also determined the partial collapse of NE walls of the summit cone (crater 1). Pyroclastic material partly accumulated on the NE part of the Sciara, and partly flowed down slope and reached the sea at Spiaggia dei Gabbiani forming a ~ 4m-thick, reddish avalanche, that was soon covered by a lava flow emitted in the following hours (Lodato et al., 2007). In this paper, we describe the first hours of activity trough eyewitnessesâ reports, geophysical monitoring, field and laboratory studies and of the erupted pyroclastic material and lava flows. Daily temperature measurements were carried out on the avalanche deposit formed by the flow of scoria along the Sciara, using a handheld thermal camera mainly during helicopter surveys. A fast cooling rate was typical of the deposit surface, and a slow cooling rate was representative of its inner portion
Conduit flow experiments help constraining the regime of explosive eruptions
It is currently impractical to measure what happens in a volcano during an explosive eruption,
and up to now much of our knowledge depends on theoretical models. Here we show, by means of
large-scale experiments, that the regime of explosive events can be constrained based on the
characteristics of magma at the point of fragmentation and conduit geometry. Our model, whose
results are consistent with the literature, is a simple tool for defining the conditions at conduit exit
that control the most hazardous volcanic regimes. Besides the well-known convective plume
regime, which generates pyroclastic fallout, and the vertically collapsing column regime, which
leads to pyroclastic flows, we introduce an additional regime of radially expanding columns, which
form when the eruptive gas-particle mixture exits from the vent at overpressure with respect to
atmosphere. As a consequence of the radial expansion, a dilute collapse occurs, which favours the
formation of density currents resembling natural base surges. We conclude that a quantitative
knowledge of magma fragmentation, i.e. particle size, fragmentation energy and fragmentation
speed, is critical for determining the eruption regime
Changes in the eruptive style of Stromboli Volcano before the 2019 paroxysmal phase discovered through SOM clustering of seismo-acoustic features compared with camera images and GBInSAR data
Two paroxysmal explosions occurred at Stromboli on 3 July and 28 August 2019, the first of which caused the death of a young tourist. After the first paroxysm an effusive activity began from the summit vents and affected the NW flank of the island for the entire period between the two paroxysms. We carried out an unsupervised analysis of seismic and infrasonic data of Strombolian explosions over 10 months (15 November 2018–15 September 2019) using a Self-Organizing Map (SOM) neural network to recognize changes in the eruptive patterns of Stromboli that preceded the paroxysms. We used a dataset of 14,289 events. The SOM analysis identified three main clusters that showed different occurrences with time indicating a clear change in Stromboli’s eruptive style before the paroxysm of 3 July 2019. We compared the main clusters with the recordings of the fixed monitoring cameras and with the Ground-Based Interferometric Synthetic Aperture Radar measurements, and found that the clusters are associated with different types of Strombolian explosions and different deformation patterns of the summit area. Our findings provide new insights into Strombolian eruptive mechanisms and new perspectives to improve the monitoring of Stromboli and other open conduit volcanoes
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