A multi-disciplinary study of the 2002–03 Etna eruption: insights into a complex plumbing system

The 2002–03 Mt Etna flank eruption began on 26 October 2002 and finished on 28 January 2003, after three months of continuous explosive activity and discontinuous lava flow output. The eruption involved the opening of eruptive fissures on the NE and S flanks of the volcano, with lava flow output and fire fountaining until 5 November. After this date, the eruption continued exclusively on the S flank, with continuous explosive activity and lava flows active between 13 November and 28 January 2003. Multi-disciplinary data collected during the eruption (petrology, analyses of ash components, gas geochemistry, field surveys, thermal mapping and structural surveys) allowed us to analyse the dynamics of the eruption. The eruption was triggered either by (i) accumulation and eventual ascent of magma from depth or (ii) depressurisation of the edifice due to spreading of the eastern flank of the volcano. The extraordinary explosivity makes the 2002–03 eruption a unique event in the last 300 years, comparable only with La Montagnola 1763 and the 2001 Lower Vents eruptions. A notable feature of the eruption was also the simultaneous effusion of lavas with different composition and emplacement features. Magma erupted from the NE fissure represented the partially degassed magma fraction normally residing within the central conduits and the shallow plumbing system. The magma that erupted from the S fissure was the relatively undegassed, volatile-rich, buoyant fraction which drained the deep feeding system, bypassing the central conduits. This is typical of most Etnean eccentric eruptions. We believe that there is a high probability that Mount Etna has entered a new eruptive phase, with magma being supplied to a deep reservoir independent from the central conduit, that could periodically produce sufficient overpressure to propagate a dyke to the surface and generate further flank eruptions.Editorial responsibility: J. Donnelly-Nolan     

First results from the plasma composition spectrometer PROMICS-3 in the Interball project

PROMICS-3 is a plasma experiment flown in the Russian project Interball. It performs three-dimensional (3D) measurements of ions in the energy range 4 eV–70 keV with mass separation and of electrons in the energy range 12 eV–35 keV. The Interball project consists of two main satellites, the Tail Probe and the Auroral Probe, each with one subsatellite. The Interball Tail Probe was launched on 3 August 1995, into a 65° inclination orbit with apogee at about 30 R_E. Both main satellites carry identical PROMICS-3 instruments and thus direct comparisons of the particle distributions will be possible once the Auroral Probe is launched. Furthermore, PROMICS-3-Tail is the first instrument measuring the 3D ion distribution function in the magnetospheric boundary layers at high latitudes. In this paper we describe the PROMICS-3 instrument and show initial results from the Tail probe, measurements of the mag-netosheath, plasma sheet, and ring current plasmas.     

Resistant biomacromolecules in marine microalgae of the classes Eustigmatophyceae and Chlorophyceae: Geochemical implications

Non-hydrolysable macromolecular constituents (i.e. algaenans) were isolated from two out of seven marine microalgae investigated. Nannochloropsis salina and Nannochloropsis sp. from the class of Eustigmatophyceae produce highly aliphatic algaenans. Flash pyrolysis and chemical degradations with HI and RuO₄ allowed for the identification of their chemical structure, which is mainly composed of polyether-linked long-chain (up to C₃₆) n-alkyl units. The building blocks of this polymer were also recognized in lipid fractions. The green microalgae (Chlorophyceae) Chlorella spaerckii, Chlorococcum sp. and Nannochloris sp. were earlier thought to biosynthesize algaenans comprising aliphatic and/or aromatic moieties. However, a new isolation method utilizing trifluoroacetic acid (TFA) prior to the other hydrolyses revealed that the macromolecular material isolated from these three chlorophytes was either hydrolysable with TFA or artefacts from the former method. Similar to algaenans from fresh water green microalgae, the aliphatic eustigmatophyte algaenans are likely to be selectively preserved in depositional environments and might ultimately serve as source rock organic matter of marine crude oils. Furthermore, they may play an important role in the cycling of carbon.     

塔里木盆地原油的成因研究

对塔里木盆地原油和生油岩饱和烃进行ＧＣ－Ｃ－ＭＳ和ＧＣ－ＭＳ分析，利用单个正构烷烃碳同位素组成和三环萜烷分布特征进行油源对比，研究了塔里木盆地原油的油源问题；根据寒武—奥陶系富含菌藻有机质生油岩饱和烃色谱分析结果，对塔里木盆地海相原油含蜡较高的成因进行了探讨     

The Impact of Erosion on Soil Productivity—An Experimental Design Applied in São Paulo State, Brazil

Soil erosion is the principal threat to agricultural sustainability, affecting both the characteristics of the in situ soil and its productive potential. However, soils vary in their resilience and there are very few empirical data upon which to appreciate the degree and type of impact on the soil caused by erosion. This paper describes an experiment designed to generate such data based on soil loss and runoff plots, and it reports on nearly nine years of experience with the design at the Instituto Agronômico, Campinas, Brazil on a Latosol (Oxisol). After seven years of erosion induced by four levels of artificial cover, the effective rainfall on the most eroded soil was 20 percent less than on the control full cover. Crop yields were also found to be significantly affected: in 1995 by nearly 700 kg/ha and in 1996 by over 1000 kg/ha—a 50% decline in yield, amounting to a loss of 4 kg/ha of maize per tonne of cumulative soil loss. Losses of nutrients (organic C, P, K, Ca and Mg) in the runoff and eroded soil were also significant with far higher levels of loss associated with the eroded sediment. Changes in the in situ soil were less clear, but a test of trends showed that the decreases in organic matter and increases in acidity could unambiguously be attributed to soil erosion. Average enrichment ratios of the eroded sediment were 1.3 for organic C, 2.6 for P, 0.7 for K, 1.3 for Ca and 1.2 for Mg. Erosion has also affected the maize quality—mainly N, Ca and B nutrient content. Through these various measures, we conclude that seven years of induced erosion has had a marked effect on soil productivity, and for the first time we are now in a position to begin calculating the financial impact of the erosion process on future yields and farmer livelihoods.     

Response of neutral boundary layers to changes of roughness

When air blows across a change in surface roughness, an internal boundary layer (IBL) develops within which the wind adapts to the new surface. This process is well described for short fetches, > 1 km. However, few data exist for large fetches on how the IBL grows to become a new equilibrium boundary layer where again the drag laws can be used to estimate the surface wind.To study this problem, data have been sampled for two years from four 30-m meteorological masts placed from 0 to 30 km inland from the North Sea coast of Jutland in Denmark. The present analysis is limited to neutral stratification, and the surface roughness is the main parameter. The analysis of wind data and two simple models, a surface layer and a planetary boundary layer (PBL) model, are described.Results from both models are discussed and compared with data analysis. Model parameters have been evaluated and the model sensitivity to those parameters has been investigated. Using the model parameters, a large-scale roughness length has been estimated.Istituto Di Fisica dell' Atmosfera I.F.A. — CNR, Rome, Italy.     

Shelf to basin transition in the Cambrian-Lower ordovician of Sardinia (Italy)

In southern and central Sardinia two different Cambrian-Lower Ordovician sedimentary belts occur. The former is exposed in southwestern Sardinia (Iglesiente and Sulcis), and is characterized by shallow-marine siliciclastic and carbonate sediments settled on a continental shelf with lowangle morphology. The latter, exposed in the Nappe Zone (central and southeastern Sardinia), consists of a thick monotonous sequence of siliciclastic deposits settled in a deeper-water basin.The comparative analysis of the sequences and their palinspastic reconstruction lead to recognize an inner and outer shelf respectively in Iglesiente and in northern Sulcis, a transition to the basin in eastern and southern Sulcis and a basin in the eastern areas of Sardinia (Nappe Zone).

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Zusammenfassung In Süd- und Zentral-Sardinien gibt es zwei unterschiedliche Sedimentgürtel im Kambrium bis Unterordovizium. Der ältere ist in Südwest-Sardinien (Iglesiente und Sulcis) aufgeschlossen. Er ist aus flachmarinen siliziklastischen und karbonatischen Sedimenten eines kontinentalen Schelfes mit flachem Relief aufgebaut. Der zweite Sedimentgürtel, aufgeschlossen in der Decken-Zone (Zentral- und SE-Sardinien) besteht aus einer mächtigen einheitlichen Folge von siliziklastischen Ablagerungen eines tieferen Beckens.Die vergleichende Analyse der Folgen und die palinspastische Rekonstruktion läßt einen inneren und einen äußeren Schelf im Gebiet von Iglesiente und nördlichen Sulcis erkennen, einen Übergang zum Becken im östlichen und südlichen Sulcis sowie ein Becken im östlichen Sardinien (Decken-Zone).

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Résumé En Sardaigne méridionale et centrale, on connaît deux ensembles sédimentaires d'âge cambro-ordovicien. Le premier, exposé dans la partie sud-occidentale de l'île (secteurs de l'Iglesiente et du Sulcis), est caractérisé par des sédiments carbonatés et terrigènes déposés sur un shelf continental morphologiquement régulier et à inclinaison faible.Le second, exposé dans la »zone des nappes« (Sardaigne orientale) est composé d'une séquence terrigène monotone déposée dans un bassin plus profond. L'analyse comparée des séquences et les reconstructions palynspastiques conduisent à reconnaître plusieurs domaines paléogéographiques: un shelf interne dans l'Iglesiente, un shelf externe dans le Sulcis septentrional, une transition vers le bassin profond dans le sud et l'est du Sulcis et ce bassin profond dans la Sardaigne orientale (»zones des nappes«).

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, . - (Iglesiente Sulcis) , , . , ( - ), , . : Iglesiente, — Sulcis, — Sulcis, — .

     

Ionospheric specification and forecasting based on observations from European ionosondes participating in DIAS project

There are two main objectives of the DIAS (European Digital Upper Atmosphere Server) project. First, it establishes a pan-European repository of raw and derived digital data describing the state of ionospheric part of the upper atmosphere, which is capable of ingesting real-time information and maintaining historical data collections provided by most operating ionospheric stations in Europe. Second, the DIAS system produces and distributes, based on the raw data collection, several operational products required by various user groups for ionospheric nowcasting, prediction and forecasting purposes. The project completed on May 2006 and the DIAS server operates since then continuously. The basic products that are delivered are real-time and historical ionograms from all DIAS-affiliated ionospheric stations, frequency plots and maps of the ionosphere over Europe based on the foF2, M(3000)F2, MUF and electron density parameters, as well as long term prediction and short term forecasting up to 24 hour ahead. The paper describes use of the ionospheric measurements in the DIAS modelling techniques for specification, predict-tion and forecasting of the ionosphere over the European region, and details the final products available to the DIAS user community.     

Secular effects of tidal friction on the planet-satellite systems of the solar system

We separate the tidal evolution of a planet-satellite system with zero eccentricity in two phases:phase 1—from the formation of the system to satellite's corotation (satellite's corotation means that its spin angular velocity equals the orbital angular velocity);phase 2—after satellite's corotation.We study the planet-satellite system during phase 1 with Darwin's graphical method and obtain an upper limit to satellite'sQ which discloses whether or not it is corotating. Moreover we obtain some qualitative information about the future evolution of the corotating satellites.The present work does not give any new result for the Earth-Moon case and for the Neptune-Triton case.     

Dynamics of greenhouse gases in the river–groundwater interface in a gaining river stretch (Triffoy catchment,Belgium)

This study investigates the occurrence of greenhouse gases (GHGs) and the role of groundwater as an indirect pathway of GHG emissions into surface waters in a gaining stretch of the Triffoy River agricultural catchment (Belgium). To this end, nitrous oxide (N₂O), methane (CH₄) and carbon dioxide (CO₂) concentrations, the stable isotopes of nitrate, and major ions were monitored in river and groundwater over 8 months. Results indicated that groundwater was strongly oversaturated in N₂O and CO₂ with respect to atmospheric equilibrium (50.1 vs. 0.55 μg L^?1 for N₂O and 14,569 vs. 400 ppm for CO₂), but only marginally for CH₄ (0.45 vs. 0.056 μg L^?1), suggesting that groundwater can be a source of these GHGs to the atmosphere. Nitrification seemed to be the main process for the accumulation of N₂O in groundwater. Oxic conditions prevailing in the aquifer were not prone for the accumulation of CH₄. In fact, the emissions of CH₄ from the river were one to two orders of magnitude higher than the inputs from groundwater, meaning that CH₄ emissions from the river were due to CH₄ in-situ production in riverbed or riparian zone sediments. For CO₂ and N₂O, average emissions from groundwater were 1.5?×?10⁵ kg CO₂ ha^?1 year^?1 and 207 kg N₂O ha^?1 year^?1, respectively. Groundwater is probably an important source of N₂O and CO₂ in gaining streams but when the measures are scaled at catchment scale, these fluxes are probably relatively modest. Nevertheless, their quantification would better constrain nitrogen and carbon budgets in natural systems.