574 research outputs found
Timescales of mingling in shallow magmatic reservoirs
Arrival of magma from depth into shallow reservoirs has been documented as one of the
possible processes leading to eruption. Magma intruding and rising to the surface interacts with the
already emplaced, degassed magmas residing at shallower depths, leaving chemical signatures in
the erupted products.We performed two-dimensional numerical simulations of the arrival of gas-
rich magmas into shallow reservoirs. We solve the fluid dynamics for the two interacting magmas,
evaluating the space–time evolution of the physical properties of the mixture.
Convection and mingling develop quickly into the chamber and feeding conduit/dyke, leading
on longer timescales to a density stratification with the lighter, gas-richer magma, mixed with
different proportions of the resident magma, rising to the top of the chamber due to buoyancy.
Over timescales of hours, the magmas in the reservoir appear to have mingled throughout, and
convective patterns become harder to identify.
Our simulations have been performed changing the geometry of the shallow reservoir and
the gas content of the initial end-member magmas. Horizontally elongated magma chambers, as
well as higher density contrasts between the two magmas, cause faster ascent velocities and also
increase the mixing efficiency
The stochastic quantization method and its application to the numerical simulation of volcanic conduit dynamics under random conditions
Stochastic Quantization (SQ) is a method for the approximation of a continuous probability distribution with a discrete one. The proposal made in this paper is to apply this technique to reduce the number of numerical simulations for systems with uncertain inputs, when estimates of the output distribution are needed. This question is relevant in volcanology, where realistic simulations are very expensive and uncertainty is always present. We show the results of a benchmark test based on a one-dimensional steady model of magma flow in a volcanic conduit
Non-Newtonian rheology of crystal-bearing magmas and implications for magma ascent dynamics
The eruptive dynamics of volcanic systems are largely controlled by the viscosity of deforming magma. Here we report the results of a series of high-temperature, high-pressure experiments at conditions relevant for volcanic conduits (250 MPa confining pressure and temperature between 500 °C and 900 °C) that were undertaken to investigate the rheology of magma with crystal fractions varying between 0.5 and 0.8 (50 to 80 wt.%) at different strain-rate conditions. The experiments demonstrate that the presence of crystals increases the relative viscosity (ratio between the viscosity of the mixture and the viscosity of the melt phase) of magmas and additionally induces a decrease of the relative viscosity with increasing strain-rate (shear thinning, non-Newtonian behavior). The experimental results, combined with existing data at low crystal fractions (0–0.3), were used to develop a semi-empirical parameterization that describes the variations of relative viscosity for crystal fractions between 0 and 0.8 and accounts for the complex non-Newtonian rheology of crystal-bearing magmas.
The new parameterization, included into numerical models simulating the magma ascent dynamics, reveals that strain-rate-dependent rheology significantly modifies the dynamic behavior inside volcanic conduits, particularly affecting the magma fragmentation conditions
Early mapping of industrial tomato in Central and Southern Italy with Sentinel 2, aerial and RapidEye additional data
Timely crop information, i.e. well before harvesting time and at first stages of crop development, can benefit farmers and producer organizations. The current case study documents the procedure to deliver early data on planted tomato to users, showing the potential of Sentinel 2 to map tomato at the very beginning of the crop season, which is a challenging task. Using satellite data, integrated with ground and aerial data, an initial estimate of area planted with tomato and early tomato maps were generated in seven main production areas in Italy. Estimates of the amount of area planted with tomato provided similar results either when derived from field surveys or from remote sensing-based classification. Tomato early maps showed a producer accuracy > 80% in seven cases out of nine, and a user accuracy > 80% in five cases out of nine, with differences attributed to the varying agricultural characteristics and environmental heterogeneity of the study areas. The additional use of aerial data improved producer accuracy moderately. The ability to identify abrupt growth changes, such as those caused by natural hazards, was also analysed: Sentinel 2 detected significant changes in tomato growth between a hailstorm-affected area and a control area. The study suggests that Sentinel 2, with enhanced spectral capabilities and open data policy, represents very valuable data, allowing crop monitoring at an early development stage
International cooperation during volcanic crisis: an example from the Italy-El Salvador monitoring system installed at Chaparrastique volcano, El Salvador
On December 29th, 2013, after 12 years of inactivity, a new explosive
eruption occurred at Chaparrastique volcano (San Miguel, el Salvador)
prompting the evacuation of more than 5000 people. The new eruption
that occurred at the volcano has so far been an isolated single
explosion of vulcanian type, and was the first eruption since 2002,
when the volcano produced a small VEI 1 eruption. The explosion
produced an ash plume of considerable (5-10 km) height, generating
heavy ash fall in nearby areas downwind, such as in the towns of
Chinameca and San Jorge. Pyroclastic density currents also affected
the flanks, damaging the coffee plantations and small inhabited areas
around the volcano.
On January 2014, following a request of support by the government of
El Salvador, INGV (Istituto Nazionale di Geofisica e Vulcanologia),
organized a task force, V-Emer (Volcano Emergency) to improve the
existing monitoring network at Chaparrastque volcano.
During a 10 days campaign in El Salvador a temporary network was
successfully installed, and it is now run by the volcanologists of MARN
(Ministerio de Medio Ambiente y Recursos Naturales, El Salvador).
The network is composed of five broadband seismic stations, 3
infrasonic microphones, 2 radiometers, 10 GPS stations, 1 thermal
camera, 1 DOAS and 1 multi-gas geochemical station for measurement
of SO2 and CO2 fluxes, respectively. Since 27 January, significant collaborative efforts are being done
between MARN and INGV for the processing and interpretation of the
data collected during monitoring. For facilitating communication and
exchange between the members of the cooperation, a mailing list has
been created, and weekly meetings are attended by the members for
the discussion on a number of scientific and technical aspects. This
initiative seeks to make significant advance into volcano monitoring
network and data analysis, as well as improving international
cooperation during volcanic crisis management.
V-EMER group: A. Bonforte, G. Giuffrida,A. La Spina, F. Montalvo, M.
Liuzzo, S. Rapisarda, G. Salerno, D. Andronico, E. Biale, A. Cannata, T.
Caltabiano, E. Del Bello, M. La Rocca, D. Granieri, L. Lodato, G.
Giudice, F. Murè, E. Pecora, M. Prestifilippo, L. Scuderi, L. Zuccarello,
G. De Natale, R. Favara, E. Privitera.
MARN group: M. Diaz, D. Escobar, E. Gutierrez, D. Hernandez, G.
Marroquin, C. Bolaños, L. Handal, C. PolĂo, B. Palacios, N. Galvez, R.
Torres, E. Escobar
Pyroclastic flow dynamics and hazard in a caldera setting: application to Phlegrean Fields
Numerical simulation of pyroclastic density currents has developed significantly in recent years and is
increasingly applied to volcanological research. Results from physical modeling are commonly taken into
account in volcanic hazard assessment and in the definition of hazard mitigation strategies. In this work,
we modeled pyroclastic density currents in the Phlegrean Fields caldera, where flows propagating along
the flat ground could be confined by the old crater rims that separate downtown Naples from the caldera.
The different eruptive scenarios (mass eruption rates, magma compositions, and water contents) were
based on available knowledge of this volcanic system, and appropriate vent conditions were calculated for
each scenario. Simulations were performed along different topographic profiles to evaluate the effects of
topographic barriers on flow propagation. Simulations highlighted interesting features associated with the
presence of obstacles such as the development of backflows. Complex interaction between outward
moving fronts and backflows can affect flow propagation; if backflows reach the vent, they can even
interfere with fountain dynamics and induce a more collapsing behavior. Results show that in the case of
large events ( 108 kg/s), obstacles affect flow propagation by reducing flow velocity and hence dynamic
pressure in distal regions, but they cannot stop the advancement of flows. Deadly conditions (in terms of
temperature and ash concentration) characterize the entire region invaded by pyroclastic flows. In the case
of small events (2.5 107 kg/s), flows are confined by distal topographic barriers which provide valuable
protection to the region beyond
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
Emotionotopy in the human right temporo-parietal cortex
AbstractHumans use emotions to decipher complex cascades of internal events. However, which mechanisms link descriptions of affective states to brain activity is unclear, with evidence supporting either local or distributed processing. A biologically favorable alternative is provided by the notion of gradient, which postulates the isomorphism between functional representations of stimulus features and cortical distance. Here, we use fMRI activity evoked by an emotionally charged movie and continuous ratings of the perceived emotion intensity to reveal the topographic organization of affective states. Results show that three orthogonal and spatially overlapping gradients encode the polarity, complexity and intensity of emotional experiences in right temporo-parietal territories. The spatial arrangement of these gradients allows the brain to map a variety of affective states within a single patch of cortex. As this organization resembles how sensory regions represent psychophysical properties (e.g., retinotopy), we propose emotionotopy as a principle of emotion coding
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