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James, M. R.
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James, M. R.
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- PublicationOpen AccessQuantifying Effusion Rates at Active Volcanoes through Integrated Time-Lapse Laser Scanning and Photography(2015-11-10)
; ; ; ; ; ;Slatcher, N.; Lancaster Environment Centre, Lancaster University, Lancaster LA1 4YQ, UK ;James, M.; Lancaster Environment Centre, Lancaster University, Lancaster LA1 4YQ, UK ;Calvari, S.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Catania, Catania, Italia ;Ganci, G.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Catania, Catania, Italia ;Browning, J.; Department of Earth Sciences, Royal Holloway, University of London, Egham TW20 0EX, UK; ; ; ; During volcanic eruptions, measurements of the rate at which magma is erupted underpin hazard assessments. For eruptions dominated by the effusion of lava, estimates are often made using satellite data; here, in a case study at Mount Etna (Sicily), we make the first measurements based on terrestrial laser scanning (TLS), and we also include explosive products. During the study period (17–21 July 2012), regular Strombolian explosions were occurring within the Bocca Nuova crater, producing a ~50 m-high scoria cone and a small lava flow field. TLS surveys over multi-day intervals determined a mean cone growth rate (effusive and explosive products) of ~0.24 m3·s−1. Differences between 0.3-m resolution DEMs acquired at 10-minute intervals captured the evolution of a breakout lava flow lobe advancing at 0.01–0.03 m3·s−1. Partial occlusion within the crater prevented similar measurement of the main flow, but integrating TLS data with time-lapse imagery enabled lava viscosity (7.4 × 105 Pa·s) to be derived from surface velocities and, hence, a flux of 0.11 m3·s−1 to be calculated. Total dense rock equivalent magma discharge estimates are ~0.1–0.2 m3·s−1 over the measurement period and suggest that simultaneous estimates from satellite data are somewhat overestimated. Our results support the use of integrated TLS and time-lapse photography for ground-truthing space-based measurements and highlight the value of interactive image analysis when automated approaches, such as particle image velocimetry (PIV), fail.202 153 - PublicationRestrictedThe dynamics of slug trains in volcanic conduits: Evidence for expansion driven slug coalescence(2017-12-15)
; ; ; ; ; ; ; ;; ; ; ;; Strombolian volcanism is a ubiquitous form of activity, driven by the ascent and bursting of bubbles of slug morphology. Whilst considerable attention has been devoted to understanding the behaviour of individual slugs in this regime, relatively little is known about how inter-slug interactions modify flow conditions. Recently, we reported on high temporal frequency strombolian activity on Etna, in which the larger erupted slug masses were followed by longer intervals before the following explosion than the smaller bursts (Pering et al., 2015). We hypothesised that this behaviour arose from the coalescence of ascending slugs causing a prolonged lag before arrival of the next distinct bubble. Here we consider the potential importance of inter-slug interactions for the dynamics of strombolian volcanism, by reporting on the first study into the behaviour of trains of ascending gas slugs, scaled to the expansion rates in volcanic conduits. This laboratory analogue study illustrates that slugs in trains rise faster than individual slugs, and can be associated with aspects of co-current flow. The work also highlights that coalescence and inter-slug interactions play an important role in modulating slug train behaviour. We also report, for the first time, on slug coalescence driven by vertical expansion of the trailing slug, a process which can occur, even where the leading slug base ascent velocity is greater than that of the trailing slug.151 2 - PublicationOpen AccessViscous plugging can enhance and modulate explosivity of strombolian eruptions(2015-08-01)
; ; ; ; ; ; ; ;Del Bello, E.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma1, Roma, Italia ;Lane, S. J.; Lancaster University (UK) ;James, M.; Lancaster University (UK) ;Llewellin, E. W.; University of Durham (UK) ;Taddeucci, J.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma1, Roma, Italia ;Scarlato, P.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma1, Roma, Italia ;Capponi, A.; Lancaster University (UK); ; ; ; ; ; Strombolian activity is common in low-viscosity volcanism. It is characterised by quasi-periodic, short-lived explosions, which, whilst typically weak, may vary greatly in magnitude. The current paradigm for a strombolian volcanic eruption postulates a large gas bubble (slug) bursting explosively after ascending a conduit filled with low-viscosity magma. However, recent studies of pyroclast textures suggest the formation of a region of cooler, degassed, more-viscous magma at the top of the conduit is a common feature of strombolian eruptions. Following the hypothesis that such a rheological impedance could act as a ‘viscous plug’, which modifies and complicates gas escape processes, we conduct the first experimental investigation of this scenario. We find that: 1) the presence of a viscous plug enhances slug burst vigour; 2) experiments that include a viscous plug reproduce, and offer an explanation for, key phenomena observed in natural strombolian eruptions; 3) the presence and extent of the plug must be considered for the interpretation of infrasonic measurements of strombolian eruptions. Our scaled analogue experiments show that, as the gas slug expands on ascent, it forces the underlying low-viscosity liquid into the plug, creating a low-viscosity channel within a high-viscosity annulus. The slug's diameter and ascent rate change as it enters the channel, generating instabilities and increasing slug overpressure. When the slug reaches the surface, a more energetic burst process is observed than would be the case for a slug rising through the low-viscosity liquid alone. Fluid-dynamic instabilities cause low and high viscosity magma analogues to intermingle, and cause the burst to become pulsatory. The observed phenomena are reproduced by numerical fluid dynamic simulations at the volcanic scale, and provide a plausible explanation for pulsations, and the ejection of mingled pyroclasts, observed at Stromboli and elsewhere.344 111 - PublicationOpen AccessUse of Forward Looking InfraRed thermal cameras at active volcanoes(Istituto Nazionale di Geofisica e Vulcanologia, 2008)
; ; ; ; ; ; ; ; ;Lodato, L.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Catania, Catania, Italia ;Spampinato, L.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Catania, Catania, Italia ;Harris, A. J. L.; HIGP/SOEST, University of Hawaii, Honolulu, Hawaii, USA ;Dehn, J.; University of Alaska Fairbanks, Alaska, USA ;James, M. R.; Environmental Science Department, Institute of Environmental and Natural Sciences, Lancaster University, Lancaster, United Kingdom ;Pecora, E.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Catania, Catania, Italia ;Biale, E.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Catania, Catania, Italia ;Curcuruto, A.; Department of Engineering, University of Catania, Catania, Italy; ; ; ;; ; ; ; ; ; ;Marzocchi, W.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Bologna, Bologna, Italia ;Zollo, A.; Dipartimento di Scienze Fisiche, Università Federico II, Napoli, Italy; Nowadays, thermal imaging has become a common remote sensing tool for monitoring active volcanoes. The study of temperature variations within openconduit systems, at eruptive fissures, active vents, domes, lava lakes, lava fields and other volcanic features has proven fundamental to better understand volcanic system behaviour over the short and long terms (Harris and Stevenson, 1997; Oppenheimer and Yirgu, 2002; Calvari et al., 2004; Wadge et al., 2006). At INGV Catania Section, thermal imaging has been applied at Mt Etna, Stromboli, Vulcano and Panarea since 2001. The instruments used are thermal cameras manufactured by FLIR (Forward Looking InfraRed) and consist in uncooled bolometers that are sensitive within 7.5 and 13 μ wavelengths. Thermal cameras are based on the capability to detect radiation emitted by bodies according to Planck’s Law. In particular, the camera we used is a FLIR thermal camera A 40 M Ethernet with a focal plane array uncooled bolometer (320 x 240 pixels), and a spectral range between 7.5 and 13 micrometers (Figure 1.). It has a standard optics 24° with spatial resolution (IFOV, instantaneous field of view) of 1.3 mrad, a horizontal view of 24° and a vertical view of 18°. This camera has also been equipped with optional filter to measure temperature values up to 1500°C with the possibility of setting up different temperature ranges. The thermal camera can record and transfer in real time via wi-fi radiometric frames in JPG format of the observed eruptive activity according to some environmental parameters, such as external temperature, air humidity and emissivity and allows the vision of volcanic activity both day and night.Temperature range varies between 0 e 500° C and the emissivity value ε = 1. To correct the temperature of all pixels from the atmospheric attenuation effects, we considered atmospheric parameters, such as air temperature and air humidity, in addition to the introduction of the path length (400 m) in the camera software. In fact, the radiations detected by the FLIR thermal cameras, that work in the spectral band between 7.5 e 13 μm, are affected by the absorption factor from the water spectrum, which is predominant in this band; particularly at La Fossa crater where the water content in the fumaroles is higher than the other gas species. Because of the necessity to correct the radiometric data from the atmospheric factors in real-time, we installed a meteorological station able to interface with the camera to provide atmospheric parameters for the auto-calibration.227 195 - PublicationOpen AccessDynamics of mild strombolian activity on Mt. Etna(2015)
; ; ; ; ; ; ; ; ; ;Pering, T. D.; University of Sheffield, Dept. of Geography ;Tamburello, G.; DiSTeM, Università di Palermo ;McGonigle, A. J. S.; University of Sheffield, Dept. of Geography ;Aiuppa, A.; DiSTeM, Università di Palermo ;James, M. R.; Lancaster Environment Centre, Lancaster University ;Lane, S. J.; Lancaster Environment Centre, Lancaster University ;Sciotto, M.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Catania, Catania, Italia ;Cannata, A.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Catania, Catania, Italia ;Patanè, D.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Catania, Catania, Italia; ; ; ; ; ; ; ; Here we report the first measurements of gas masses released during a rare period of strombolian activity at the Bocca Nuova crater, Mt. Etna, Sicily. UV camera data acquired for 195 events over an ≈27 minute period (27th July 2012) indicate erupted SO2 masses ranging from ≈0.1 to ≈14 kg per event, with corresponding total gas masses of ≈0.1 to 74 kg. Thus, the activity was characterised by more frequent and smaller events than typically associated with strombolian activity on volcanoes such as Stromboli. Events releasing larger measured gas masses were followed by relatively long repose periods before the following burst, a feature not previously reported on from gas measurement data. If we assume that gas transport within the magma can be represented by a train of rising gas pockets or slugs, then the high frequency of events indicates that these slugs must have been in close proximity. In this case the longer repose durations associated with the larger slugs would be consistent with interactions between adjacent slugs leading to coalescence, a process expedited close to the surface by rapid slug expansion. We apply basic modelling considerations to the measured gas masses in order to investigate potential slug characteristics governing the observed activity.We also cross correlated the acquired gas fluxes with contemporaneously obtained seismic data but found no relationship between the series in line with the mild form of manifest explosivity.504 339 - PublicationRestrictedMorphological complexities and hazards during the emplacement of channel-fed `a`a lava flow fields: A study of the 2001 lower flow field on Etna(2010-01)
; ; ; ; ;Applegarth, L. J.; Lancaster Environment Centre, Lancaster University, Bailrigg, Lancaste ;Pinkerton, H.; Lancaster Environment Centre, Lancaster University, Bailrigg, Lancaste ;James, M. R.; Lancaster Environment Centre, Lancaster University, Bailrigg, Lancaste ;Calvari, S.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Catania, Catania, Italia; ; ; Long-lived basaltic eruptions often produce structurally complex, compound `a`a flow fields. Here we reconstruct the development of a compound flow field emplaced during the 2001 eruption of Mt. Etna (Italy). Following an initial phase of cooling-limited advance, the reactivation of stationary flows by superposition of new units caused significant channel drainage. Later, blockages in the channel and effusion rate variations resulted in breaching events that produced two new major flow branches. We also examined small-scale, late-stage ‘squeeze-up’ extrusions that were widespread in the flow field. We classified these as ‘flows’, ‘tumuli’ or ‘spines’ on the basis of their morphology, which depended on the rheology, extrusion rate and cooling history of the lava. Squeeze-up flows were produced when the lava was fluid enough to drain away from the source bocca, but fragmented to produce blade-like features that differed markedly from `a`a clinker. As activity waned, increased cooling and degassing led to lava arriving at boccas with a higher yield strength. In many cases this was unable to flow after extrusion, and laterally extensive, near-vertical sheets of lava developed. These are considered to be exogenous forms of tumuli. In the highest yield strength cases, near-solid lava was extruded from the flow core as a result of ramping, forming spines. The morphology and location of the squeeze-ups provides insight into the flow rheology at the time of their formation. Because they represent the final stages of activity of the flow, they may also help to refine estimates of the most advanced rheological states in which lava can be considered to flow. Our observations suggest that real-time monitoring of compound flow field evolution may allow complex processes such as channel breaching and bocca formation to be forecast. In addition, documenting the occurrence and morphology of squeeze-ups may allow us to determine whether there is any risk of a stalled flow front being reactivated. This will therefore enhance our ability to track and assess hazard posed by lava flow emplacement.143 23 - PublicationRestrictedSeparating the thermal fingerprints of lava flows and simultaneous lava fountaining using ground-based thermal camera and SEVIRI measurements(2013)
; ; ; ; ;Ganci, G.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Catania, Catania, Italia ;James, M. R. ;Calvari, S.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Catania, Catania, Italia ;Del Negro, C.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Catania, Catania, Italia; ;; During effusive eruptions, thermal satellite monitoring has proved well suited to map the thermal flux from lava flows. However, during lava fountaining events, thermal contributions from active flows and from the fountain itself cannot be separated in low resolution satellite data. Here using photogrammetry and atmospheric modeling techniques, we compare radiance estimates from long-range ground-based thermal camera data (from which the fountain can be excluded) with those from SEVIRI satellite images for a fountaining event at Mount Etna (12 August 2011). The radiant heat flux determined from the ground-based camera showed similar behavior to values retrieved from Spinning Enhanced Visible and Infrared Imager (SEVIRI); thus the SEVIRI signal is interpreted to be dominated by the lava flows, with minimal contribution from the fountain. Furthermore, by modeling the cooling phase of each pixel inundated by lava, the mean thickness and lava volume (~2.4 × 106 m3) derived from camera images are comparable with those calculated from SEVIRI (~2.8 × 106 m3).130 26 - PublicationOpen AccessLava flow superposition: The reactivation of flow units in compound ’a’a flows(2010-05-10)
; ; ; ; ;Applegarth, L. J.; Lancaster Environment Centre, Lancaster University, Bailrigg, Lancaster ;Pinkerton, H.; Lancaster Environment Centre, Lancaster University, Bailrigg, Lancaster ;James, M. R.; Lancaster Environment Centre, Lancaster University, Bailrigg, Lancaster ;Calvari, S.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Catania, Catania, Italia; ; ; Basaltic 'a'ā lava flows often demonstrate compound morphology, consisting of many juxtaposed and superposed flow units. Following observations made during the 2001 eruption of Mt. Etna, Sicily, we examine the processes that can result from the superposition of flow units, when the underlying units are sufficiently young to have immature crusts and deformable cores. During this eruption, we observed that the emplacement of new surface flow units may reactivate older, underlying units by squeezing the still-hot flow core away from the site of loading. Here, we illustrate three different styles of reactivation that depend on the time elapsed between the emplacement of the two flow units, hence the rheological contrast between them. For relatively long time intervals (2 to 15 days), and consequently significant rheological contrasts, superposition can pressurise the underlying flow unit, leading to crustal rupture and the subsequent extrusion of a small volume of high yield strength lava. Following shorter intervals (1 to 2 days), the increased pressure caused by superposition can result in renewed, slow advance of the underlying immature flow unit front. On timescales of < 1 day, where there is little rheological contrast between the two units, the thin intervening crust can be disrupted during superposition, allowing mixing of the flow cores, large-scale reactivation of both units, and widespread channel drainage. This mechanism may explain the presence of drained channels in flows that are known to have been cooling-limited, contrary to the usual interpretation of drainage as an indicator of volume-limited behaviour. Because the remobilisation of previously stagnant lava can occur swiftly and unexpectedly, it may pose a significant hazard during the emplacement of compound flows. Constant monitoring of flow development to identify areas where superposition is occurring is therefore recommended, as this may allow potentially hazardous rapid drainage events to be forecast. Reactivation processes should also be borne in mind when reconstructing the emplacement of old lava flow fields, as failure to recognise their effects may result in the misinterpretation of features such as drained channels.145 201