Relationship between the flank sliding of the South East Crater (Mt. Etna, Italy) and the paroxysmal event of November 16, 2006

Over the last 2 years, the south east crater (SEC) at Mt. Etna (Italy) has been characterised by the intermittent emission of lava flows, often accompanied by paroxysmal episodes with violent strombolian activity and/or lava fountains. One of the most intense and intriguing episodes occurred on November 16, 2006 during strombolian and effusive activity from the very top of the SEC. At the eastern base of the crater, a violent and short-lasting outburst generated a 300-m-high eruptive curtain of finely fragmented magma and steam, which collapsed in a few seconds giving rise to a small but significant pyroclastic flow. The paroxysm was preceded by progressive sliding of the eastern flank of the SEC edifice, which led to the formation of a large niche. Previously published models explain the outburst as due to rapid vaporisation of water contained in sediments on contact with hot lava flowing along the flank of the SEC or, alternatively, to gravitational collapse of a destabilised portion of the eastern flank of the crater. However, several lines of evidence suggest that these models do not adequately explain the paroxysm, which we propose was associated with the explosive emission of magma during the rapid opening of an ESE-WNW-oriented fracture at the eastern base of the SEC. Moreover, geochemical data of the products associated with this episode show that they are the most primitive and gas-rich among those erupted during the entire 2006 period. We suggest that the paroxysm of November 16, 2006, which occurred at base of the SEC, was a magma outburst due to rapid ground fracturing related to a drop in confining pressure upon the underlying dyke consequent to the sliding of the eastern flank of the SEC cone. Specifically, the unloaded shallow portion of the feeding dyke did not restrain the arrival of a new batch of gas-rich magma, which worked its way out by fracturing the base of the niche at its weakest point. This paroxysm appears significant because it reveals the potential development of syn-eruptive dynamics acting directly on the uppermost portion of the plumbing system which is able to generate pyroclastic flows even on basaltic volcanoes such as Mount Etna.     

The dyke swarm of Mount Calanna (Etna, Italy): an example of the uppermost portion of a volcanic plumbing system

A new multidisciplinary study, combining geology, petrography, and geochemistry, on the rocks of the isolated hill of Mount Calanna (Mount Etna, Italy) has provided evidence for the existence of a dyke swarm, formed by more than 200 dykes distributed over an area of ~0.7 km², with an intensity of intrusion up to 40%. All bodies are deeply altered, and the geological and mesostructural surveying of 132 dykes revealed that they intruded in E–W direction, with an average dip of 60°. The faults affecting the outcrop have in general an E–W strike and dip of ~55°: these have all normal motion and have been interpreted as coeval with the dykes. This interpretation contrasts with the previous hypothesis that considered Mount Calanna as a thrust resulting from compressive deformation resulting from the gravitational spreading of the volcanic edifice. Mount Calanna is here interpreted as the uppermost portion of a vertically extensive magmatic plexus that fed the eruptive activity of one (or more) eruptive center/s sited in the Valle del Bove area. Measurements of the apparent densities on 23 dykes and host rock samples give an average value of 2,420 kg/m³ for the entire complex, ~15% lower than the density expected for hawaiitic magma, placing an important constraint on the geophysical identification of similar structures. Considering that Mount Etna is not an old eroded edifice but an active and growing volcano, the exposure of this subvolcanic structure can be regarded as exceptional. Its geometry and physical characteristics can be thus regarded as an interesting example of the present-day shallow plumbing system of Mount Etna as well as of other basaltic volcanoes.     

A novel soil moisture‐based drought severity index (DSI) combining water deficit magnitude and frequency

A correct identification of drought events over vegetated lands can be achieved by detecting those soil moisture conditions that are both unusually dry compared with the ‘normal’ state and causing severe water stress to the vegetation. In this paper, we propose a novel drought index that accounts for the mutual occurrence of these two conditions by means of a multiplicative approach of a water deficit factor and a dryness probability factor. The former quantifies the actual level of plant water stress, whereas the latter verifies that the current water deficit condition is unusual for the specific site and period. The methodology was tested over Europe between 1995 and 2012 using soil moisture maps simulated by Lisflood, a distributed hydrological precipitation–runoff model. The proposed drought severity index (DSI) demonstrates to be able to detect the main drought events observed over Europe in the last two decades, as well as to provide a reasonable estimation of both extension and magnitude of these events. It also displays an improved adaptability to the range of possible conditions encountered in the experiment as compared with currently available indices based on the sole magnitude or frequency. The results show that, for the analyzed period, the most extended drought events observed over Europe were the ones in Central Europe in 2003 and in southern Europe in 2011/2012, while the events affecting the Iberian Peninsula in 1995 and 2005 and Eastern Europe in 2000 were among the most severe ones. © 2015 European Commission ‐ Joint Research Centre. Hydrological Processes published by John Wiley & Sons Ltd.     

A subterminal radial fissure eruption on Mt. Etna

The author describes a subterminal radial fissure eruption of Mt. Etna that took place in February 1964. A sketchmap and a chemical analysis of the lava are given.

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Zusammenfassung Der Verfasser beschreibt den subterminalen Radialspaltenausbruch des Ätnas im Februar 1964 und fügt eine chemische Analyse der geförderten Lava bei.

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Résumé L'auteur décrit une éruption subterminale de l'Etna qui a eu lieu sur une fissure radiale en février 1964. Une carte de la région sommitale de l'Etna et une analyse chimique de la lava sont ajoutées.

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Riassunto L'autore descrive l'eruzione radiale verificatasi al cono terminale dell'Etna nel Febbraio del 1964. Dà inoltre un rilevamento schematico della zona del cratere centrale ed il chimismo della roccia.

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, 1964 .

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Dedicated to Professor Dr. A.Rittmann on the occasion of his 75. birthday

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This study is a part of the researches, carried out with the funds of the National Research Council of the Italy under the direction of Prof. A.Ritmann.     

Assessment of Water Quality After 10 Years of Reclaimed Water Injection: The Nardò Fractured Aquifer (Southern Italy)

Experimental studies have been carried out in a fractured coastal aquifer of the Salento region (Nardò, Italy), which has been subjected to 12,000 m³/day of treated municipal waste water injected into a natural sinkhole since 1991. The analytical parameters of ground water sampled in 30 monitoring wells in the area down gradient from the sinkhole, taking into account the direction of ground water flow, have been compared before and after injection. The water table mound (1.5 m), the reduction of sea water extent (2 km), and the spreading of injected pollutants were evaluated by means of a mathematical model. The predicted values in the monitoring wells were adjusted to inorganic nitrogen biodegradation using transformation rates developed in laboratory tests. After 10 years, the injection has increased the volume of the available resource for agricultural and drinking water use, without any notable decrease in the preexisting ground water quality. Moreover, to preserve water resources from pollution, the mathematical model allowed the maximum constituent concentrations (standards) in waste water reclamation for recharge to be identified. A precautionary area around the sinkhole was also defined so that withdrawal prohibition could be implemented to avoid risks to human health.     

Uplift rates defined by U-series and 14C ages of serpulid-encrusted speleothems from submerged caves near Siracusa,Sicily (Italy)

We have established a plausible rate of uplift near Siracusa in southeastern Sicily (Italy) over the last glacial–interglacial cycle using U-series ages of submerged speleothem calcite and ¹⁴C ages of calcite serpulid layers that encrust the speleothems during cave submergence. The precisely determined ages of these sea level benchmarks were compared with expected relative sea level position based on glacio-hydro-isostatic modeling to assess the rate of uplift in this region. When combined with the age of various late Holocene archaeological sites that have been recently described and characterized in terms of their functional position relative to sea level these data collectively define a rate of uplift ≤0.4 mm a^?1 along this portion of the Sicilian coastline. These results are consistent with an age assignment of marine isotope stage (MIS) 5.3 or 5.5 for the Akradina terrace, which in turn places temporal constraints on paleoshorelines above and below this level.     

Using unsteady-state water level data to estimate channel roughness and discharge hydrograph

A novel methodology for simultaneous discharge and channel roughness estimation is developed and applied to data sets available at three experimental sites. The methodology is based on the synchronous measurement of water level data in two river sections far some kilometers from each other, as well as on the use of a diffusive flow routing solver and does not require any direct velocity measurement. The methodology is first analyzed for the simplest case of a channel with a large slope, where the kinematic assumption holds. A sensitivity and a model error analysis are carried out in this hypothesis in order to show the stability of the results with respect to the error in the input parameters in the case of homogeneous roughness and to analyze the effect of unknown roughness heterogeneity on the estimated discharges. The methodology is then extended to the more general case of channels with mild slope and validated using field data previously collected in three Italian rivers: the Arno (in Tuscany), the Tiber (in Latium) and the Vallo di Diana, a small tributary of the Tanagro river (in Southern Italy). The performance of the proposed algorithm has been investigated according to three performance criteria estimating the quality of the match between the measured and the computed stage and discharge hydrographs. Results of the field tests can be considered good, despite the uncertainties of the field data and of the measured values.     

Field investigation on rilling in the experimental Sparacia area,South Italy

In this paper the results of a field investigation on rilling carried out in the experimental Sparacia area are reported. The measurements were made on a plot 6 m wide and 22 m long subjected to natural rainfalls. For ten rainfalls the total soil loss (interrill and rill erosion) was collected in a storage system consisting of two tanks arranged in series at the base of the plot. Rill morphology (rill length and cross‐sections) was measured for five rainfall events, while the rill profile was surveyed for three events. First the contribution of each component (rill and interrill erosion) to total soil loss was established. Then the analysis allowed establishment of a power relationship between the rill length and the rill volume. Finally, for three events detailed information on rill erosion and rill morphology allowed verification of the applicability of WEPP and estimation of the rill erodibility constant. Copyright © 2007 John Wiley & Sons, Ltd.     

Transport of suspended sediments under the influence of bank macro‐roughness

River restoration works often include measures to promote morphological diversity and enhance habitat suitability. One of these measures is the creation of macro‐roughness elements, such as lateral cavities and embayments, in the banks of channelized rivers. However, in flows that are heavily charged with fine sediments in suspension, such as glacier‐fed streams and very low‐gradient reaches of large catchment rivers, these lateral cavities may trap these sediments. Consequently, the morphological changes may be affected, and the functionality of the restoration interventions may be compromised. Herein, we analyse the influence of these macro‐roughness elements on the transport of fine sediments in the main channel. Laboratory tests with uniform flow charged with sediments in a channel with banks equipped with large‐scale rectangular roughness elements were carried out. The laboratory experiments covered a wide range of rectangular cavity geometrical configurations and shallowness ratios. The influence of key parameters such as flow shallowness, geometric ratios of the cavities and initial sediment concentration was tested. Surface particle image velocimetry, sediment samples and temporal turbidity records were collected during the experiments. The amount of sediments captured by the cavities, the temporal evolution of the concentration of sediments in suspension and the flow hydrodynamics are cross‐analysed and discussed. It is shown that the trapping efficiency of the macro‐roughness elements is a clear function of the channel geometry and the shallowness of the flow. Copyright © 2017 John Wiley & Sons, Ltd.     

Estimation of PM<Subscript>10</Subscript> concentration from air quality data in the vicinity of a major steelworks site in the metropolitan area of Avilés (Northern Spain) using machine learning techniques

Atmospheric particulate matter (PM) is one of the pollutants that may have a significant impact on human health. Data collected over 7 years from the air quality monitoring station at the LD-III steelworks, belonging to the Arcelor-Mittal Steel Company, located in the metropolitan area of Avilés (Principality of Asturias, Northern Spain), is analyzed using four different mathematical models: vector autoregressive moving-average, autoregressive integrated moving-average (ARIMA), multilayer perceptron neural networks and support vector machines with regression. Measured monthly, the average concentration of pollutants (SO₂, NO and NO₂) and PM₁₀ (particles with a diameter less than ?10 μm) is used as input to forecast the monthly average concentration of PM₁₀ from one to 7 months ahead. Simulations showed that the ARIMA model performs better than the other models when forecasting 1 month ahead, while in the forecast from one to 9 months ahead the best performance is given by the support vector regression.