Aeolian Islands Research Articles

New insights in the geodynamics of the Lipari–Vulcano area (Aeolian Archipelago, southern Italy) from geological, geodetic and seismological data

Geological, geodetic and seismological data have been analyzed in order to frame the Lipari–Vulcano complex (Aeolian archipelago, southern Italy) into the geodynamic context of the southeastern Tyrrhenian Sea. It is located at the northern end of a major NNW–SSE trending right-lateral strike-slip fault system named “Aeolian–Tindari–Letojanni” which has been interpreted as a lithospheric discontinuity extending from the Aeolian Islands to the Ionian coast of Sicily and separating two different tectonic domains: a contractional one to the west and an extensional one to the north-east. Structural field data consist of structural measurements performed on well-exposed fault planes and fractures. The mesostructures are mostly represented by NW–SE striking normal faults with a dextral-oblique component of motion. Minor structures are represented by N–S oriented joints and tension gashes widespread over the whole analyzed area and particularly along fumarolized sectors. The analyzed seismological dataset (from 1994 to 2013) is based on earthquakes with magnitude ranging between 1.0 and 4.8. The hypocenter distribution depicts two major alignments corresponding to the NNW–SSE trending Aeolian–Tindari–Letojanni fault system and to the WNW–ESE oriented Sisifo–Alicudi fault system. GPS data analysis displays ∼3.0mm/yr of active shortening between the two islands, with a maximum shortening rate of about 1.0×10−13s−1, between La Fossa Caldera and south of Vulcanello. This region is bounded to the north by an area where the maximum values of shear strain rates, of about 0.7×10−13s−1 are observed. This major change occurs in the area south of Vulcanello that is also characterized by a transition in the way of the vertical axis rotation. Moreover, both the islands show a clear subsidence process, as suggested by negative vertical velocities of all GPS stations which exhibit a decrease from about −15 to −7mm/yr from north to south. New data suggest that the current kinematics of the Lipari–Vulcano complex can be framed in the tectonic context of the eastward migrating Sisifo–Alicudi fault system. This is dominated by transpressive tectonics in which contractional and minor extensional structures can coexist with strike-slip motion.

Volcanological evolution of the Rivi–Capo Volcanic Complex at Salina, Aeolian Islands: magma storage processes and ascent dynamics

Lava flows and pyroclastic deposits from strombolian fallout related to the activity of the Rivi and Capo volcanoes, which are representative of early subaerial volcanoes on Salina (Aeolian Islands), have been investigated through a geological–petrological approach. Our geological field survey shows that Rivi and Capo volcanoes are part of a single N50°E aligned volcanic complex, here named Rivi–Capo Volcanic Complex (RCVC). Stratigraphically specific rock sampling has allowed reconstruction of the magma feeding processes through time. Whole rock major element compositions, together with core-to-rim profiles of plagioclase and clinopyroxene crystals, show a general evolution toward more basic compositions through the three formations constituting the Capo volcano and within the Rivi center. MELTS simulations and mass balance modeling suggest that the RCVC rocks are the result of fractional crystallization of plagioclase, clinopyroxene, and olivine (ca. 45 % of solid removed) from a primary magma. In addition to fractional crystallization, continuous recharge and mixing with more basic magma coming from deeper parts of the magmatic plumbing system contributed to the final volcanic rock compositions. Our textural and microanalytical data on plagioclase and clinopyroxene crystals allow the definition of a multilevel magmatic storage system with reservoirs at ~20 and ~3 km below sea level. When processes of magma differentiation, ascent, and storage are considered together with the stratigraphic position of each sample, a history of continuous modification of the RCVC plumbing system can be constructed. Volcanism may have been characterized by fissure-type eruptions during the early stages (Lower Capo, Lower Rivi, and Middle Capo Formations), gradually changing later to central-type volcanism (Upper Capo and Upper Rivi Formations).

Occurrence and origin of soils with andic properties in Calabria (southern Italy)

Andic-like soils, along with Andosols, have previously been reported in non-volcanic ecosystems of the coastal and mountainous areas of the Calabria region (southern Italy), but little is known about their properties, soil formation processes and volcanic source areas. Chemical, mineralogical, microscopic, sub-microscopic and magnetic analyses were carried out on 8 soils which were selected from the major Calabrian geological sectors in order to assess relationships between parent material and bedrock. Soil chemical properties revealed an occurrence of andic or vitric properties in the studied soils as a whole, and the optical microscopy enabled to identify volcanic glass, micro-pumices and soil isotropic matrix, clearly indicating volcanic inputs. Three groups of soils, identified on the basis of the degree of andic properties, showed rather homogeneous also in terms of chemical properties, clay mineralogy and land use, as well as with regard to micromorphology and magnetic susceptibility. Part of the intra-group similarities was a consequence of similar distances between sites and volcanic source area, as suggested by the correlations found between ferrihydrite content, andic (i.e. % of ammonium oxalate extractable Al+0.5 Fe and phosphate retention) and magnetic properties vs. distances from several Sicilian districts. The elemental composition obtained by SEM/EDS analyses of soil glass fragments supported these findings and related the origin of most of the studied soils to the high potassium calc-alkaline magmatism of the southernmost Eolian Islands (mainly Lipari and Vulcano), except for soils from the marine terraces of northern Calabria (PRA) and the Aspromonte Massif (DEL), which were both linked, albeit uncertainly, to Campanian volcanism. Soil magnetic properties were significantly (0.79**) correlated to the andic properties, so confirming the high performance of magnetic susceptibility as low cost proxy for the identification of volcanic constituents.

Growth after collapse: the volcanic and magmatic history of the Neostromboli lava cone (island of Stromboli, Italy)

This study focuses on the Holocene Neostromboli lava cone which is part of the Stromboli volcano (Aeolian Islands, Italy). It represents an important example of the structure and behaviour of lava cone re-growth shortly after a large-scale volcano sector collapse. Neostromboli’s eruptive style is dominated by extrusion of sheet-like a’a lava flows and associated autoclastic breccias. The lava cone developed during five phases of activity (phases A to E) representing discrete episodes of lava effusion characterised by rapid changes in magma composition, spatial development of the feeder system and physical properties of erupted lavas through time. Although they all belong to the potassic series (KS) with SiO2 49–55 wt% and MgO 2.50–6.25 wt%, the Neostromboli lavas have distinct petrogenetic characteristics ranging from leucite-free and low-Sr shoshonitic basalts (phases A and B) to leucite-bearing shoshonitic basalts with high (phase C) and intermediate (phase D) Sr contents, and to leucite-free, biotite-bearing shoshonites (phase E). Three different batches of mantle-derived, relatively primitive basic magmas fed the activity of phases A, C and D. The evolution phases A to B is inferred to have occurred in a continuously replenished, tapped and crystallizing (RTF) magma chamber whereas phase E products were dominantly generated by fractional crystallization from phase D magmas. The Neostromboli cone shows summit, flank and satellite vents and sheet intrusions with different geometry and location through time, reflecting the interplay of regional tectonics, precursory instability processes and volcano load.

Diversity of prokaryotic community at a shallow marine hydrothermal site elucidated by Illumina sequencing technology.

To investigate the prokaryotic community structure and composition in an active hydrothermal site, named Black Point, off Panarea Island (Eolian Islands, Italy), we examined sediment and fluid samples, differing in temperature, by a massive parallel sequencing (Illumina) technique targeting the V3 region of the 16S rRNA gene. The used technique enabled us to detect a greater prokaryotic diversity than that until now observed and to reveal also microorganisms occurring at very low abundance (≤0.01%). Most of sequences were assigned to Bacteria while Archaea were a minor component of the microbial community in both low- and high-temperature samples. Proteobacteria (mainly consisting of Alpha-, Gamma-, and Epsilonproteobacteria) dominated among all samples followed by Actinobacteria and Bacteroidetes. Analyzed DNA obtained from samples taken at different temperatures indicated the presence of members of different dominant genera. The main differences were observed between sediment samples where Rhodovulum and Thiohalospira prevailed at high temperature, while Thalassomonas and Sulfurimonas at low temperature. Chlorobium, Acinetobacter, Sulfurimonas, and Brevundimonas were abundant in both low- and high-temperature fluid samples. Euryarchaeota dominated the archaeal community in all samples. Classes of Euryarchaeota embracing hyperthermophilic members (Thermococci and Thermoplasmata) and of Crenarchaeota (Thermoprotei) were more abundant in high-temperature samples. A great number of sequences referred to Bacteria and Archaea still remained unaffiliated, indicating that Black Point site represents a rich source of so-far uncharted prokaryotic diversity.

The endemic vascular flora of Peloritani Mountains (NE Sicily): Plant functional traits and phytogeographical relationships in the most isolated and fragmentary micro-plate of the Alpine orogeny

This study is aimed at (1) producing a complete and updated inventory of the endemic vascular flora of Peloritani Mountains, (2) defining the geographical limits of Peloritani, regarded here as a biogeographical district and (3) highlighting possible paleogeographic connections with other Mediterranean lands. The heterogeneity analysis of the endemic flora was performed by means of contingency tables, through the χ2 test. The endemic flora of this area consists of 129 specific and infraspecific taxa, of which 15 are restricted to the Peloritani Mountains. The analysis of habitats revealed that endemic taxa are most abundant on cliffs, rangelands, woods and garrigues. A large number of surveyed taxa are endemic to central-southern Italy and Sicily, while the number of endemic taxa in common with Calabria, Etna and Aeolian Islands turned out to be rather low, in spite of the geographical proximity. The endemic flora of Peloritani allows to emphasize palaeogeographical relationships not only with the neighbouring Mediterranean territories, but also with currently remote ones, such as southern Spain, Sardinia and Corsica. The phytogeographical framework substantiates the hypothesis that the Peloritani floristic district coincides with the limit given to Peloritani Mountains by structural geologists.

Pyroclastic density currents at Stromboli volcano (Aeolian Islands, Italy): a case study of the 1930 eruption

Pyroclastic density currents (PDC) related to paroxysmal eruptions have caused a large number of casualties in the recent history of Stromboli. We combine here a critical review of historical chronicles with detailed stratigraphic, textural, and petrographic analyses of PDC deposits emplaced at Stromboli over the last century to unravel the origin of currents, their flow mechanism and the depositional dynamics. We focus on the 1930 PDC as they are well described in historical accounts and because the 1930 eruption stands as the most voluminous and destructive paroxysm of the last 13 centuries. Stromboli PDC deposits are recognizable from their architecture and the great abundance of fresh, well-preserved juvenile material. General deposit features indicate that Stromboli PDC formed due to the syn-eruptive gravitational collapse of hot pyroclasts rapidly accumulated over steep slopes. Flow channelization within the several small valleys cut on the flanks of the volcano can enhance the mobility of PDC, as well as the production of fine particles by abrasion and comminution of hot juvenile fragments, thereby increasing the degree of fluidization. Textural analyses and historical accounts also indicate that PDC can be fast (15–20 m/s) and relatively hot (360–700 °C). PDC can thus flow right down the slopes of the volcano, representing a major hazard. For this reason, they must be adequately taken into account when compiling risk maps and evaluating volcanic hazard on the Island of Stromboli.

Evidence of active subsidence at Basiluzzo island (Aeolian islands, southern Italy) inferred from a Roman age wharf

The Aeolian Arc (Southern Tyrrhenian Sea, Italy) is one of the most active volcanic areas of the Mediterranean basin, affected by volcanic/hydrothermal and seismic activity. Ancient populations settled this region since historical times, building coastal installations which currently are valuable archaeological indicators of relative sea level changes and vertical land movements. In this study we show and discuss data on the relative sea level change estimated from a submerged wharf of Roman age dated between 50 B.C. and 50 A.D., located at Basiluzzo Island. This structure has been studied through marine surveys and archaeological interpretations and is presently located at a corrected depth of −4.10 ± 0.2 m. We explain this submergence by a cumulative effect of the relative sea level change caused by the regional glacio-hydro-isostatic signal, active since the end of the last glacial maximum, and the local volcano-tectonic land subsidence. Finally, a total subsidence rate of 2.05 ± 0.1 mm/yr−1, with a volcano-tectonic contribution of 1.43 ± 0.1 mm/yr−1 for the last 2 ka BP, is inferred from the comparison against the latest predicted sea level curve for the Southern Tyrrhenian Sea, suggesting new evaluations of the volcano-tectonic hazard for this area of the Aeolian islands.

Provenance Analyses of the Volcanic Rock Grinding Stones from the Greek Colony of Selinunte, Sicily (Italy)—Constraints and Possibilities

The petrography as well as the major and trace element compositions of the Selinunte grinding stones, made of grey vesicular lava, were analysed. By comparison with geochemical data from volcanic rocks in the Mediterranean, we were able to determine that only a minor number of the tools were extracted from the nearest volcanics of Mount Etna and the Hyblean Mountains, while the majority of the grinding stones were most probably imported from the Aeolian Islands, although an origin from the Aegean cannot be excluded entirely. The results are important in order to scrutinize trading connections, especially for the earlier times of settlement during the sixth century bc.

Therasiaite, (NH4)3KNa2Fe2+Fe3+(SO4)3Cl5, a new sulfate chloride from La Fossa Crater, Vulcano, Aeolian islands, Italy

AbstractThe new mineral therasiaite, ideally (NH4)3KNa2Fe2+Fe3+(SO4)3Cl5, was found in a mediumtemperature (∼250°C) intracrater active fumarole at La Fossa crater, Vulcano, Aeolian Islands, Sicily, Italy. It occurs on a pyroclastic breccia as brown to dark brown equant to short prismatic crystals up to 0.1 mm in length, in association with salammoniac, kremersite and adranosite. The mineral is monoclinic, space group: Cc (no. 9) with a = 18.284(4), b = 12.073(2), c = 9.535(2) Å, β = 108.10(3)°, V = 2000.6(7) Å3 and Z = 4. The six strongest reflections in the X-ray powder diffraction pattern are: [dobs in Å(I)(hkl)] 2.812(100)(23), 2.664(77)(13), 3.297(28)(33), 3.208(14)(2), 3.008(12)(040), 2.942(11)(331). The empirical formula (based on 17 anions per formula unit (p.f.u.)) is (NH4)2.68K1.32Na2.04Fe1.76Al0.12Mn0.12S2.98O11.95Cl5.05. The measured density is 2.41(1) g cm−3, dcalc = 2.395 g cm−3. The mineral is biaxial (−) with α= 1.585(3) β = 1.615(3) and γ = 1.630(3) (white light). Using single-crystal diffraction data, the structure was refined to a final R(F) = 0.0240 for 5574 independent observed reflections [I > 2σ(I)]. The structure of therasiaite displays a novel topology and contains two independent, distorted octahedral Fe sites, with the Fe atoms in oxidation state 3+ and 2+, respectively, each surrounded by three Cl atoms and three oxygens of the sulfate ions. The Fe octahedra and the three independent sulfate anions are connected to form chains running along [001]. Voids between the chains are occupied by three independent ammonium ions (partially replaced by K+), one K+ and two Na+ ions. The formula resulting from the structure refinement is [(NH4)2.25K0.75]KNa2Fe2(SO4)3Cl5.

3-D density structure and geological evolution of Stromboli volcano (Aeolian Islands, Italy) inferred from land-based and sea-surface gravity data

We present the first density model of Stromboli volcano (Aeolian Islands, Italy) obtained by simultaneously inverting land-based (543) and sea-surface (327) relative gravity data. Modern positioning technology, a 1×1m digital elevation model, and a 15×15m bathymetric model made it possible to obtain a detailed 3-D density model through an iteratively reweighted smoothness-constrained least-squares inversion that explained the land-based gravity data to 0.09mGal and the sea-surface data to 5mGal. Our inverse formulation avoids introducing any assumptions about density magnitudes. At 125m depth from the land surface, the inferred mean density of the island is 2380kgm−3, with corresponding 2.5 and 97.5 percentiles of 2200 and 2530kgm−3. This density range covers the rock densities of new and previously published samples of Paleostromboli I, Vancori, Neostromboli and San Bartolo lava flows. High-density anomalies in the central and southern part of the island can be related to two main degassing faults crossing the island (N41 and N64) that are interpreted as preferential regions of dyke intrusions. In addition, two low-density anomalies are found in the northeastern part and in the summit area of the island. These anomalies seem to be geographically related with past paroxysmal explosive phreato-magmatic events that have played important roles in the evolution of Stromboli Island by forming the Scari caldera and the Neostromboli crater, respectively.

One-Year Surveillance of the Chemical and Microbial Quality of Drinking Water Shuttled to the Eolian Islands

This work presents the chemical and biological characteristics of drinking water shuttled from the main land (Naples, Campania, Italy) to the Eolian islands (situated off the north-eastern coast of Sicily). The data obtained from a one year surveillance program, (January to December, 2012) indicate that the quality of the water delivered to the islands meets the drinking water quality standard year-round. During summer, when requests for drinking water increase with the increase of the islands population, the quality of the shipped water decreases, most likely due to the use of older vessels in addition to those used during the rest of the year. The results suggest an implementation of a monitoring program at the point-of-use in order to identify potential sources of contamination early in shipped drinking water and, therefore, to manage the potential risk of waterborne illness more effectively.

Noble-gas signature of magmas from a heterogeneous mantle wedge: The case of Stromboli volcano (Aeolian Islands, Italy)

We report on the variation of the elemental (He, Ne, and Ar) and isotopic (He and Ar) compositions of olivine- and clinopyroxene-hosted fluid inclusions hosted in lavas, pyroclastics, and cumulate xenoliths from the last 60ka of the eruptive history of Stromboli volcano, Italy. Samples belong to (i) the present-day activity as represented by shoshonitic (SHO) basalts, i.e., pumices with low porphyritic (LP) content and high porphyritic (HP) scoriae; (ii) the subalkaline versus alkaline products erupted at Stromboli during its subaerial history among the extreme magmatic series, i.e., calc-alkaline (CA) and potassic (KS); and (iii) the only known ultramafic cumulates (San Bartolo wehrlite xenoliths, SBX) outcropping in the island, carried to the surface by recent (ca. 2ka) basaltic lava. To interpret the results better, we also investigated trace elements in the clinopyroxenes of wehrlite xenoliths and the Sr and Nd isotopes of all of the products in which the 3He/4He ratio was measured.Wehrlite xenoliths are igneous cumulates crystallized at mantle depth that mostly consist of clinopyroxene and olivine crystals with limited compositional variation. The texture, mineral chemistry, pattern of trace elements and Sr–Nd-isotope ratios (in clinopyroxene) suggest that these cumulates were produced by the early crystallization of a primitive basaltic magma with CA or HKCA–SHO affinity.The gas contents measured in the mafic crystals decrease from the wehrlite xenoliths through LP pumice, CA and KS lavas and, finally, to the HP scoria. This observation is consistent with crystallization and fluid entrapment from mantle depths to progressively shallower crustal levels. The low gas content extracted from the HP crystals did not allow measurement of their 3He/4He ratios.Most of the investigated crystals exhibit a 3He/4He ratio in the range of 4.0–4.9 Ra, with only the KS mafic minerals exhibiting lower 3He/4He values (≤3.5 Ra). The low values of He-isotope ratios relative to those of the most-uncontaminated mantle source of the Aeolian lavas (i.e., 3He/4He ~7 Ra at Alicudi) and in common volcanic arcs suggest that the Stromboli mantle wedge is more contaminated by sediments and aqueous fluids derived by the active subduction of the Ionian slab. We also hypothesize that a process of mantle He loss that occurred during the mantle metasomatism contributed to the decrease of 3He/4He. The low 3He/4He values of the KS minerals with respect to the other Stromboli magmatic series are consistent with the higher Sr- and lower Nd-isotope ratios measured in the same samples and are attributed to source heterogeneity.Finally, data for the 3He/4He ratios from mafic minerals were compared with those of currently emitted hydrothermal fluids, which are regularly sampled for volcano surveillance. The maximum 3He/4He ratio found in the hydrothermal fluids matched the maximum ratio measured in the LP fluid inclusions (i.e., 4.6 Ra) and thus corresponds to the upper limit that should be expected for surface gases during or before high-intensity eruptive events in which a deep gas component is released from the magma. These data also represent a reference for Stromboli volcanic surveillance.

Dynamics of Strombolian explosions: Inferences from field and laboratory studies of erupted bombs from Stromboli volcano

AbstractStrombolian activity is characterized by repeated, low energy, explosions and is named after the volcano where such activity has persisted for around 2000 years, i.e., Stromboli (Aeolian Islands, Italy). Stromboli represents an excellent laboratory where measurements of such explosions can be made from safe, but close, distances. During a field campaign in 2008, two 15 cm diameter bombs were quenched and collected shortly after a normal explosion. The bombs were characterized in terms of their textural, chemical, rheological, and geophysical signatures. The vesicle and crystal size distribution of the samples, coupled with the glass chemistry, enabled us to quantify variations in the degassing history and rheology of the magma resident in the shallow (i.e., in last 250 m of conduit length). The different textural facies observed in these bombs showed that fresh magma was mingled with batches of partially to completely degassed, oxidized, high‐crystallinity, high‐viscosity, evolved magma. This magma sat at the top of the conduit and played only a passive role in the explosive process. The fresh, microlite‐poor, vesiculated batch, however, experienced a response to the explosive event, by undergoing rapid decompression. Integration of geophysical measurements with sample analyses indicates that popular bubble‐bursting models may not fit this case. We suggest that the degassed, magma forms a plug, or rheological layer, at the top of the conduit, through which the fresh magma bursts. In this model we need to consider the paradox of a slug ascending too fast through a magma of varying viscosity and yield strength.

Ash Features from Ordinary Activity at Stromboli Volcano

In this work we focus our attention on micro-scale textural observations and chemical analysis of the surface of ash particles erupted from ordinary activity at Stromboli volcano (Aeolian Islands, Italy). Ashes are related to three vent systems: NE1, NE2 and SW showing different eruptive styles. Samples were collected during three campaigns: 1-5 September 2008; 20, 22 September 2008 and 18 June 2009, with two different methods: collection on a clean surface downwind and use of remotely controlled, electrically propelled aeromodels, which penetrate directly in the eruptive plume and collect ash samples that are less affected by transport-related sorting processes. A micro-textural approach has been conducted working at step: from preliminary observations under binocular microscope on a medium number of 700 particles, to thin sections and sub-micron investigations, using high resolution instruments. Micro-texture and morphology of ash particles were observed under FE-SEM, at high magnification (30,000/50,000×) measuring the main shape parameters (area, perimeter, max length, compactness, Feret’s diameter, Heywood’s diameter and elongation). Ashes are made up by a wide spectrum of fragments whose end-members are represented by two main textural types with different colour, shape, internal textures and vesicularity named “Type a” and “Type b”. “Type a” shows great similarities with fragments called “tachilite” while “Type b” fragments are very similar to the named “sideromelane” fragments. Fragments with intermediate textural features are present and named as “Type a1” and “Type b1”, respectively. The relative abundances of each type of fragments greatly vary in samples collected from different groups of vents. Chemical analysis of the external surfaces indicates that all the different grain types underwent alteration phenomena and precipitation of neo-formation minerals on their surfaces. The alteration is dependent from the atmospheric conditions around the vent and not from the type of fragments. During the periods of sampling, ash erupted from individual explosions of different vents, does not show big differences in morphology and chemistry of surface features, but mainly in terms of relative proportion of fragments. “Type b” fragments predominate in the ash erupted from typical strombolian activity whereas “Type a” fragments are ubiquitous.

Tephrochronology of the astronomically-tuned KC01B deep-sea core, Ionian Sea: insights into the explosive activity of the Central Mediterranean area during the last 200 ka

We present a major, trace and rare earth element characterization of single glass shards from fifteen tephra layers found in the astronomically-tuned KC01B deep-sea core (Ionian Sea, Central Mediterranean-36°15.25′N, 17°34.44′E, 3642 m water depth). KC01B is considered a reference core for the Mediterranean area since it provides a new reliable astronomical tuned timescale for the last 1.112 My (Lourens, 2004). The studied deposits punctuate the marine record in a time span ranging from ca 16 ka to ca 191 ka B.P. encompassing the climatic zones Y, X, W and V. They are related to volcanic activity of the Campania Plain, Aeolian Islands, Mt. Etna and Pantelleria Island. Along with major main markers of the Central Mediterranean area such as Y-1, Y-5, and X-6, astronomically dated at 16.7 ka, 39.1 ka, and 110.5 ka, respectively, the succession contains a number of well preserved deposits which can represent useful inter-archive instruments of correlation. The Campania Plain, in particular, sourced at least nine compositionally homogeneous tephra layers prior to the Campanian Ignimbrite event. The data obtained in this work provide a new detailed analytical reference database for Ionian Sea tephrochronology and for proximal-distal correlation studies. They may help to unravel from the marine record the history of poorly known or unknown explosive activity on land since the middle Pleistocene along with chemical composition, size and dispersal of the products.

Shallow-water gaseohydrothermal plume studies after massive eruption at Panarea, Aeolian Islands, Italy

Marine water dynamics in the near field of a massive gas eruption near Panarea (Aeolian Islands volcanic arc, SE Tyrrhenian Sea) is described. ADCP current-meters were deployed during the paroxysmal phase in 2002 and 2003 a few meters from the degassing vent, recording day-long time series. Datasets were sorted to remove errors and select good quality ensembles over the entire water column. Standard deviation of error velocity was considered a proxy for inhomogeneous velocity fields over beams. Time series intervals had been selected when the basic ADCP assumptions were fulfilled and random errors minimized. Backscatter data were also processed to identify bubbles in the water column with the aim of locating bubble-free ensembles. Reliable time series are selected combining these data. Two possible scenarios have been described: firstly, a highly dynamic situation with visible surface diverging rings of waves, entrainment on the lower part of the gas column, detrainment in the upper part and a stagnation line (SL) at mid depth where currents were close to zero and most of the gas bubbles spread laterally; secondly, a less dynamic situation with water entraining into the gas plume at all depths and no surface rings of diverging waves. Reasons for these different dynamics may be ascribed to changes in gas fluxes (one order of magnitude higher in 2002). Description of SL is important to quantify its position in the water column and timing for entrainment–detrainment, and it can be measured by ADCP and calculated from models.

Chemical Composition and Free Radical Scavenging Activity of the Essential Oil of Achillea ligustica Growing Wild in Lipari (Aeolian Islands, Sicily)

In the present study the chemical composition of the essential oils from aerial parts and flowers of Achillea ligustica All., collected in Lipari (Aeolian Islands) was evaluated by GC and GC-MS. (Z)-Chrysanthenyl acetate was the most abundant component of both oils (29.6% in A1 and 27.8% in F1), followed by viridiflorol (16.8% in A1 and 21.6% in F1), bornyl acetate (8.7% in A1 and 11.6% in F1) and 1,8-cineole (7.4% in A1 and 9.3% in F1). A comparison was made of the composition of the different populations studied so far. Futhermore, the free radical scavenging activity of the oil was determined by DPPH and ABTS methods.

New insights on volcanic and tectonic structures of the southern Tyrrhenian (Italy) from marine and land seismic data

We present results from the first crustal seismic tomography for the southern Tyrrhenian area, which includes ocean bottom seismometer (OBS) data and a bathymetry correction. This area comprises Mt. Etna, the Aeolian Islands, and many volcanic seamounts, including the Marsili Seamount. The seismicity distribution in the area depends on the complex interaction between tectonics and volcanism. The 3‐D velocity model presented in this study is obtained by the inversion of P wave arrival times from crustal earthquakes. We integrate travel time data recorded by an OBS network (Tyrrhenian Deep Sea Experiment), the SN‐1 seafloor observatory, and the land network. Our model shows a high correlation between the P wave anomaly distribution and seismic and volcanic structures. Two main low‐velocity anomalies underlie the central Aeolian Islands and Mt. Etna. The two volumes, which are related to the well‐known active volcanism, are separated and located at different depths. This finding, in agreement with structural, petrography, and GPS data from literature, confirms the independence of the two systems. The strongest negative anomaly is found below Mt. Etna at the base of the crust, and we associate it with the deep feeding system of the volcano. We infer that most of the seismicity is generated in brittle rock volumes that are affected by the action of hot fluids under high pressure due to the active volcanism in the area. Lateral changes of velocity are related to a transition from the western to the central Aeolian Islands and to the passage from continental crust to the Tyrrhenian oceanic uppermost mantle.

Seismic potential in Italy from integration and comparison of seismic and geodetic strain rates

Abstract Seismological and geodetic data provide key information about the kinematics and active tectonics of plate margins. Focal solutions enable the determining of the directions in which the current tectonic stress acts when fault rupturing occurs; GPS measurements provide information on the crustal velocity field and on current interseismic strain rates. The comparison of the strain rates resulting from the two datasets provides further insight into how large an area is affected by aseismic deformation, which is a valuable indicator for seismic hazard mitigation and estimation of the seismic potential. In this work, we investigate both seismic and geodetic strain rates and the combined field resulting from the joint inversion of the geodetic and seismic datasets, providing a picture of the overall deformation field and its variation during the last decades. In this way, we try to give an overview of the seismic potential distribution across the Apennines and southern Italy, as a qualitative analysis of space-time variations in the released seismic strain rate, compared to the space-time distribution of the cumulated geodetic strain rate. The results show a variable distribution of the seismic efficiency over Italy. The Southern Apennines shows the greatest seismic potential, highlighting a significantly lower seismicity in the last two decades over an area affected by the highest total strain rates. The Messina Straits and eastern Sicily have a significant seismic potential, together with the Calabrian arc (from the Tindari–Letojanni and central Aeolian islands to the Mt. Pollino area), as a result of seismic gaps with respect to the combined strain rates in the investigated period. This long gap highlights the longer recurrence periods for the strongest earthquakes on this area. The central–northern Apennines and off-shore northern Sicily, show a lower seismic potential than central–southern Apennines, probably due to the more recent seismicity affecting these areas.