Heat and SO2 Emission Rates at Active Volcanoes – The Case Study of Masaya, Nicaragua

The necessity of understanding volcanic phenomena, so as to assist hazard assessment and risk management, has led to development of a number of techniques for the tracking of volcanic events so as to support forecasting efforts. Since 1980s scientific community has progressively drifted research and surveillance at active volcanoes by integrated approach. Nowadays, volcano observatories over the world record and integrate real or near-real time data for monitoring and understanding volcano behaviour. Among the geophysical, geochemical, and volcanological parameters, the tracking of temperature changes at several volcanic features (e.g., open-vent systems, eruptive vents, fumaroles) and variations in sulphur dioxide flux and concentration at volcanic plumes are key factors for studying and monitoring active volcanoes. Temperature is one of the first parameters that have been considered in understanding the nature of volcanoes and their eruptions. Thermal anomalies have proved to be precursors of a number of eruptive events, and once an eruption begins, temperature plays a major role in lava flow emplacement and lava field development. At active volcanoes, temperature has been measured by direct and indirect methodologies. Direct measurements represent the traditional thermal monitoring carried out at fumaroles, hot springs, molten lava bodies, and crater lakes, using thermocouples. Indirect measurements, also known as thermal remote sensing, can be performed by satellite, ground, and airborne surveys. Owing to the danger of most kinds of eruption, and the need of monitoring inaccessible areas on volcanoes, indirect measurements are especially attractive. Among them, thermal imagery is the most widespread and results from the capability to detect the infrared radiation emitted from the surface of hot bodies, and to provide the radiometric map of heat distribution of the body’s surface. This has been of primary importance for capturing the evolution of thermal anomalies, which shed light on magma movements at shallow depths. While magma is rising, hot gases separate from the melt and escape either directly from the main conduits, or indirectly by leaking through fumaroles, fractures, and faults, or by dissolving within crater lakes and hot spring waters, resulting in variations in their temperature and chemical composition. At the surface, these phenomena are also associated with radiative heat fluxes, which can be detected by infrared thermal detectors. The application of thermal imaging to volcanology was largely performed using satellite surveys, but in the last decade there has been increasing application of compact (hand-held or tripod-mounted) thermal imagers used from the air or ground. Volcanic degassing plays a key role in magma transport and style, and timing of volcanic eruptions observed at the Earth’s surface. The assessment of volcanic gas composition and flux has become a standard procedure for volcanic monitoring and forecasting since degassing regimes are fundamentally linked to volcanic processes. Magma contains dissolved gases that are released into the atmosphere during both quiescent and eruptive stages. At high pressures, deep beneath the Earth’s surface, gases are dissolved in magma; however as soon as magma rises toward the surface, where pressures are lower, gases start to exsolve according to the solubility-pressure relationship of each species, as well as compositional and diffusional constraints. The abundance and final gas phase composition of the emitted plume depends on magma composition(s), volatile fugacities, crystallisation and on the dynamics of magma degassing, including kinetic effects. However, at the surface, the composition and flux of volcanic gases may change with time, reflecting variations in the magmatic feeding system of the volcano. Hence by studying and tracking this variability a number of parameters, such as magma residing depths and the amount of degassing magma bodies can be determined. Among the volcanic gas species, sulphur dioxide (SO2) is one of the most-well investigated in remote sensing. As for temperature, SO2 concentration and emission rates can be measured using both direct sampling and non-contact, remote sensing measurements. The latter carried out during air- and ground-based surveys and satellite platforms, are based on optical spectroscopy. Since the 1970s, SO2 flux has been remotely measured using the COrrelation SPECtrometer (COSPEC) at several volcanoes worldwide. Over the last 10 years the advent of small, commercial and low cost spectrometers offered a valuable replacement to the outdated COSPEC. In particular, the combination of UV spectrometers with the Differential Optical Absorption Spectroscopy (DOAS) analytical method improved significantly data collection offering a number of advantages such as the possibility of obtaining measurements in the challenging environments typical of volcanic areas and detection of other plume species. Our intent here is to discuss findings and implications arising from the integration of thermal imaging-derived temperature and SO2 emission rates. Calibrated temperatures from thermal imagery can provide qualitative as well as quantitative information, fundamental insights and parameters contributing to understanding and modelling of several eruptive features. Anomalies in SO2 emission rates have been often documented at several volcanoes prior to eruptive crisis. In syn-eruptive stages, anomalies in the SO2 flux pattern might indicate variations in the eruptive style and regime associated with changes in the volcano shallow feeder system. At open-vent systems, in non-eruptive phases, changes in SO2 flux emission have provided information on increases or decreases of magma supply in the shallow plumbing system suggesting likely volcanic unrests or magma migration towards peripheral areas of the volcano edifice, respectively. There is still much to explore about volcano behaviour and eruptive mechanisms, however, the combination of different types of monitoring techniques is crucial for constraining baselines for predicting phases of volcano unrests and for gaining useful insights for volcano hazard assessment

Frequency-dependent modulation of cerebellar excitability during the application of non-invasive alternating current stimulation

Background: it is well-known that the cerebellum is critical for the integrity of motor and cognitive actions. Applying non-invasive brain stimulation techniques over this region results in neurophysiological and behavioural changes, which have been associated with the modulation of cerebellar-cerebral cortex connectivity. Here, we investigated whether online application of cerebellar transcranial alternating current stimulation (tACS) results in changes to this pathway. Methods: thirteen healthy individuals participated in two sessions of cerebellar tACS delivered at different frequencies (5Hz and 50Hz). We used transcranial magnetic stimulation to measure cerebellar-motor cortex (M1) inhibition (CBI), short-intracortical inhibition (SICI) and short-afferent inhibition (SAI) before, during and after the application of tACS. Results: we found that CBI was specifically strengthened during the application of 5Hz cerebellar tACS. No changes were detected immediately following the application of 5Hz stimulation, nor at any time point with 50Hz stimulation. We also found no changes to M1 intracortical circuits (i.e. SICI) or sensorimotor interaction (i.e. SAI), indicating that the effects of 5Hz tACS over the cerebellum are site-specific. Conclusions: cerebellar tACS can modulate cerebellar excitability in a time- and frequency-dependent manner. Additionally, cerebellar tACS does not appear to induce any long-lasting effects (i.e. plasticity), suggesting that stimulation enhances oscillations within the cerebellum only throughout the stimulation period. As such, cerebellar tACS may have significant implications for diseases manifesting with abnormal cerebellar oscillatory activity and also for future behavioural studies

UAV Thermal Infrared Remote Sensing of an Italian Mud Volcano

Extreme environments like active volcanoes exhibit many difficulties in being studied by in situ techniques. For exam-ple, during eruptions, summit areas are very hard to be accessed because of logistics problems and/or volcanic hazards. The use of remote sensing techniques in the last 20 years by satellite or airborne platforms has proven their capabilities in mapping and monitoring the evolution of volcanic activity. This approach has become increasingly important, as much interest is actually focused on understanding precursory signals to volcanic eruptions. In this work we verify the use of cutting-edge technology like unmanned flying system thermally equipped for volcanic applications. We present the results of a flight test performed by INGV in collaboration with the University of Bologna (Aerospace Division) by using a multi-rotor aircraft in a hexacopter configuration. The experiment was realized in radio controlled mode to overcome many regulation problems which, especially in Italy, limit the use of this system in autonomous mode. The overall goal was not only qualitative but also quantitative oriented. The system flew above an Italian mud volcano, named Le Salinelle, located on the lower South West flank of Mt. Etna volcano, which was chosen as representative site, providing not only a discrimination between hot and cold areas, but also the corresponding temperature values. The in-flight measurements have been cross-validated with contemporaneous in-situ acquisition of thermal data and from independent measurements of mud/water temperature

Opioid activity profiles of oversimplified peptides lacking in the protonable N-terminus

Recently, we described cyclopeptide opioid agonists containing the D-Trp-Phe sequence. To expand the scope of this atypical pharmacophore, we tested the activity profiles of the linear peptides Ac-Xaa-Phe-Yaa (Xaa = L/D-Trp, D-His/Lys/Arg; Yaa = H, GlyNH2). Ac-D-Trp-PheNH2 appeared to be the minimal binding sequence, while Ac-D-Trp-Phe-GlyNH 2 emerged as the first noncationizable short peptide (partial) agonist with high \u3bc-opioid receptor affinity and selectivity. Conformational analysis suggested that 5 adopts in solution a \u3b2-turn conformation. \ua9 2012 American Chemical Society

Lava effusion — A slow fuse for paroxysms at Stromboli volcano?

International audienceThe 2007 effusive eruption of Stromboli followed a similar pattern to the previous 2002–2003 episode. In both cases, magma ascent led to breaching of the uppermost part of the conduit forming an eruptive fissure that discharged lava down the Sciara del Fuoco depression. Both eruptions also displayed a ‘paroxysmal' explosive event during lava flow output. From daily effusion rate measurements retrieved from helicopter- and satellite-based infrared imaging, we deduce that the cumulative volume of lava erupted before each of the two paroxysms was similar. Based on this finding, we propose a conceptual model to explain why both paroxysms occurred after this ‘threshold' cumulative volume of magma was erupted. The gradual decompression of the deep plumbing system induced by magma withdrawal and eruption, drew deeper volatile-rich magma into the conduit, leading to the paroxysms. The proposed model might provide a basis for forecasting paroxysmal explosions during future effusive eruptions of Stromboli

The 2007 Stromboli eruption: event chronology and effusion rates using thermal infrared data

Using thermal infrared images recorded by a permanent thermal camera network maintained on Stromboli volcano (Italy), together with satellite and helicopter-based thermal image surveys, we have compiled a chronology of the events and processes occurring before and during Stromboli’s 2007 effusive eruption. These digital data also allow us to calculate the effusion rates and lava volumes erupted during the effusive episode. At the onset of the 2007 eruption, two parallel eruptive fissures developed within the North East crater, eventually breaching the NE flank of the summit cone and extending along the eastern margin of the Sciara del Fuoco. These fed a main effusive vent at 400 m a.s.l. to feed lava flows that extended to the sea. The effusive eruption was punctuated, on 15 March, by a paroxysm with features similar to the 5 April paroxysm that occurred during the 2002-03 effusive eruption. A total of between 3.2 x 106 m3 and 11 x 106 m3 of lava was erupted during the 2007 eruption over 34 days of effusive activity. More than half of this volume was emplaced during the first 5.5 days of the eruption. Although the 2007 effusive eruption had a comparable erupted volume to the previous (2002-03) effusive eruption, it had a shorter duration and thus a mean output rate (= total volume divided by eruption duration) that was one order of magnitude greater than the 2002-03 event (~2.4 m3 s-1 compared with 0.32±0.28 m3 s-1). In this paper, we discuss similarities and differences between these two effusive events, and interpret the processes occurring in 2007 in terms of the recent dynamics witnessed at Stromboli

The 2007 Stromboli eruption: Event chronology and effusion rates using thermal infrared data

Using thermal infrared images recorded by a permanent thermal camera network maintained on Stromboli volcano (Italy), together with satellite and helicopter‐based thermal image surveys, we have compiled a chronology of the events and processes occurring before and during Stromboli’s 2007 effusive eruption. These digital data also allow us to calculate the effusion rates and lava volumes erupted during the effusive episode. At the onset of the 2007 eruption, two parallel eruptive fissures developed within the northeast crater, eventually breaching the NE flank of the summit cone and extending along the easternmargin of the Sciara del Fuoco. These fed amain effusive vent at 400m above sea level to feed lava flows that extended to the sea. The effusive eruption was punctuated,on 15 March, by a paroxysm with features similar to those of the 5 April paroxysm that occurred during the 2002–2003 effusive eruption. A total of between 3.2 × 106 and 11 × 106 m3 of lava was erupted during the 2007 eruption, over 34 days of effusive activity. More than half of this volume was emplaced during the first 5.5 days of the eruption. Although the 2007 effusive eruption had an erupted volume comparable to that of the previous (2002–2003) effusive eruption, it had a shorter duration and thus a mean output rate (=total volume divided by eruption duration) that was 1 order of magnitude higher than that of the 2002– 2003 event (∼2.4 versus 0.32 ± 0.28 m3 s−1). In this paper, we discuss similarities and differences between these two effusive events and interpret the processes occurring in 2007 in terms of the recent dynamics witnessed at Stromboli