Active Lava Flows Research Articles

Radar signatures of active lava flows on Venus

Radar signatures of active lava flows on Venus

Analysis of Lava from the Cumbre Vieja Volcano Using Remote Sensing Data from DESIS and Sentinel-2

On 19th September 2021, a protracted eruption of the Cumbre Vieja Volcano on the Canary Island of La Palma commenced and continued for a duration of 12 weeks. Lava flows starting from the rift zone at the mid-western flank of Cumbre Vieja advanced toward the western coast of the island. The eruption was monitored by different remote sensing satellites, including the Copernicus Sentinel missions and DESIS. The Sentinel-2 Copernicus satellites acquired multispectral data from 15th September onward. On September 30th, and with a difference of ∼2 h with respect to Sentinel-2 A, the DESIS hyperspectral sensor also acquired data from the volcano and then again on 15th October 2021. Typically, mid-infrared (around 3.8 μm) data are used for the thermal analysis of active lava flows. However, neither Sentinel-2 nor DESIS possesses mid-infrared bands and the Sentinel-2 high-wavelengths bands (∼2 μm) have some limitations. Nevertheless, the hyperspectral character of DESIS enables the analysis of active erupting volcanoes in near-infrared wavelengths. The results of this analysis find fluid lava temperatures of about 1100–1200 K but there are problems associated with the high-temperature lava spectral emissivity.

A new portable field rotational viscometer for high-temperature melts.

Mounted on top of furnaces, laboratory viscometers can be used for the rheological characterization of high temperature melts, such as molten rocks (lava). However, there are no instruments capable of measuring the viscosity of large volumes of high temperature melts outside the laboratory at, for example, active lava flows on volcanoes or at industrial sites. In this article, we describe a new instrument designed to be easy to operate, highly mobile, and capable of measuring the viscosity of high temperature liquids and suspensions (<1350 °C). The device consists of a torque sensor mounted in line with a stainless-steel shear vane that is immersed in the melt and driven by a motor that rotates the shear vane. In addition, a thermocouple placed between the blades of the shear vane measures the temperature of the melt at the measurement location. An onboard microcomputer records torque, rotation rate, and temperature simultaneously and in real time, thus enabling the characterization of the rheological flow curve of the material as a function of temperature and strain rate. The instrument is calibrated using viscosity standards at low temperatures (20-60 °C) and over a wide range of stress (30-3870Pa), strain rate (0.1-27.9s-1), and viscosity (10-650Pas). High temperature tests were performed in large scale experiments within ∼25 l of lava at temperatures between 1000 and 1350 °C to validate the system's performance for future use in natural lava flows. This portable field viscometer was primarily designed to measure the viscosity of geological melts at their relevant temperatures and in their natural state on the flanks of volcanoes, but it could also be used for industrial purposes and beyond.

High-spectral-resolution Fabry-Pérot interferometers overcome fundamental limitations of present volcanic gas remote sensing techniques

Remote sensing (RS) of volcanic gases has become a central tool for studying volcanic activity. For instance, ultraviolet (UV) skylight spectroscopy with grating spectrographs (GS) enables SO2 (and, under favourable conditions, BrO) quantification in volcanic plumes from autonomous platforms at safe distances. These measurements can serve volcanic monitoring and they cover all stages of volcanic activity in long measurement time series, which substantially contributes to the refinement of theories on volcanic degassing. Infrared (IR) remote sensing techniques are able to measure further volcanic gases (e.g., HF, HCl, CO2, CO). However, the employed Fourier transform spectrometers (FTSs) are intrinsically intricate and, due to limited resolving power or light throughput, mostly rely on either lamps, direct sun, or hot lava as light source, usually limiting measurements to individual field campaigns. We show that many limitations of grating spectrographs and Fourier transform spectrometer measurements can be overcome by Fabry-Perot interferometer (FPI) based spectrograph implementations. Compared to grating spectrographs and Fourier transform spectrometers, Fabry-Perot interferometer spectrographs reach a 1-3 orders of magnitude higher spectral resolution and superior light throughput with compact and stable set-ups. This leads to 1) enhanced sensitivity and selectivity of the spectral trace gas detection, 2) enables the measurement of so far undetected volcanic plume constituents [e.g., hydroxyl (OH) or sulfanyl (SH)], and 3) extends the range of gases that can be measured continuously using the sky as light source. Here, we present measurements with a shoe-box-size Fabry-Perot interferometer spectrograph (resolving power of ca. 150000), performed in the crater of Nyiragongo volcano. By analysing the light of a ultraviolet light emitting diode that is sent through the hot gas emission of an active lava flow, we reach an OH detection limit of about 20 ppb, which is orders of magnitude lower than the mixing ratios predicted by high-temperature chemical models. Furthermore, we introduce example calculations that demonstrate the feasibility of skylight-based remote sensing of HF and HCl in the short-wave infrared with Fabry-Perot interferometer spectrographs, which opens the path to continuous monitoring and data acquisition during all stages of volcanic activity. This is only one among many further potential applications of remote sensing of volcanic gases with high spectral resolution.

Mapping lava flow from the Kilauea eruption of 2018 in the east rift zone using space-based synthetic aperture radar

ABSTRACT Lava flows from volcanoes can significantly destroy infrastructure, although they rarely threaten human life. Mapping lava flows is essential to managing the volcanic hazard during eruptions and understanding significant changes in geomorphology after eruptions. In 2018, the eruption of Kilauea, Hawaii’s youngest and most active volcano, destroyed more than 700 homes, farmlands, and roads. Active lava flow tracking is crucial for providing timely warnings to evacuate residents and protect infrastructure. We constructed a map of the lava flow in the East Rift Zone (ERZ) during the Kilauea volcanic eruption in 2018 using remotely sensed satellite synthetic aperture radar observations. We processed 23 C-band Sentinel-1 A/B interferometric wide mode acquisitions captured from May 1 to 17 September 2018 and applied a coherent change detection (CCD) technique to detect minute changes in the target structure. A time series of coherence maps provided detailed spatial information on the movement of the lava flow fields in the ERZ. The overall lava flow map had an area of approximately 33.3 km2 and was verified with a lava thickness map provided by the United States Geological Survey that was generated by two digital elevation models using airborne light detection and ranging observations. Excellent agreement (>90%) among the lava flow observations suggests that the CCD technique is effective in monitoring lava flows during a volcanic eruption.

Combining hydro-acoustic sources and bathymetric differences to track the vent evolution of the Mayotte eruption, Mozambique Channel

The majority of Earth volcanism takes place in the deep ocean. Deep-sea volcanoes are particularly complicated to study due to their remoteness. Very different methods can be used and their combination can lead to crucial information about submarine volcanoes behavior. In Mayotte, Comoros archipelago, efforts have been made to study and monitor the deep volcanic activity (∼3000 m) currently occurring east of Mayotte through various methods and campaigns on land and at sea. In October 2020, a line of 10 Ocean Bottom Seismometers was deployed during 10 days, leading to a hand-picked catalog of more than a thousand of hydro-acoustic signals, which have been associated with reactions between hot lava and deep cold ocean waters. During the same period, repeated swath bathymetry surveys were performed over an active lava flow field. We compare the time evolution of the hydro-acoustic events locations and bathymetry differences observed between each survey. While bathymetric information gives absolute location of new lava flows, hydro-acoustic events give detailed relative time variations leading to short-term spatial evolution. Bathymetric information thus provides snapshots of the eruptive area evolution at specific times, when hydro-acoustic signals show its continuous evolution. By combining both complementary analyses we are able to clearly define the detailed evolution of the lava flows pattern in the short time period of 10 days. Applied to the data already acquired on Mayotte since 2019, this method could allow us to estimate more precisely the volcano effusion rate and its evolution, giving further insights on the feeding system.

A Near Real-Time and Free Tool for the Preliminary Mapping of Active Lava Flows during Volcanic Crises: The Case of Hotspot Subaerial Eruptions

Monitoring the evolution of lava flows is a challenging task for volcano observatories, especially in remote volcanic areas. Here we present a near real-time (every 12 h) and free tool for producing interactive thermal maps of the advance of lava flows over time by taking advantage of the free thermal data provided by FIRMS and the open-source R software. To achieve this, we applied two filters on the FIRMS datasets, one on the satellite layout (track) and another on the fire radiative power (FRP). To determine the latter, we carried out a detailed statistical analysis of the FRP values of nine hotspot subaerial eruptions that included Cumbre Vieja-2021 (Spain), Fagradalsfjall-2021 (Iceland), LERZ Kilauea-2018 (USA), and six eruptions on the Galápagos Archipelago (Ecuador). We found that an FRP filter of 35 ± 17 MW/pixel worked well at the onset and during the first weeks of an eruption. Afterward, once the cumulative statistical parameters had stabilized, a filter that better fit the investigated case could be obtained by running our statistical code. Using the suggested filters, the thermal maps resulting from our mapping code have an accuracy higher than 75% on average when compared with the official lava flow maps of each eruption and an offset of only 3% regarding the maximum lava flow extension. Therefore, our easy-to-use codes constitute an additional, novel, and simple tool for rapid preliminary mapping of lava fields during crises, especially when regular overflights and/or unoccupied aerial vehicle campaigns are out of budget.

Kīlauea–Leilani 2018 lava flow delineation using Sentinel2 and Landsat8 images

Abstract Kīlauea is a broad shield volcano built against the southeastern slope of Mauna Loa. The summit presently has a caldera that is roughly 4 km by 3.2 km wide, and walls between 0 and 120 m high. In late April 2018, an eruption involving both the summit crater and the lower East Rift Zone occurred. In this work a quasi-real-time estimation of the evolution of radiant lava flow extension starting from May 2018 for Kīlauea–Leilani eruption using satellite image data is presented. The active lava flow evolution was obtained using Copernicus Sentinel2 (S2) and USGS-Landsat8 (L8) polar satellites acquiring medium/high-spatial-resolution images (20 × 20 m and 30 × 30 m, respectively) in the vis–SWIR–TIR (Short wave infrared-thermal infra red) spectral range. Because of the Kīlauea eruption extension and duration, a multisensor approach was used in order to improve the timing of the information derived by high-spatial-resolution remote-sensed data merging two missions with different revisit times. The 2018 eruptions at Hawaii's Kīlauea Volcano developed rapidly after the initial activity centred on the Pu‘u ‘Ō‘o crater floor on 1 May followed by draining of the lava lake at Halemáumáu Overlook Crater in the following days. During the magma extrusion from the summit, earthquake swarms and ground cracking hit the Leilani Estates neighbourhood on 2 May. With the S2 and L8 sensors we followed the lava flow from 5 May up to mid August, considering also that the activity started to decline from the beginning of August. At the end of the activity, Kīlauea Volcano had experienced its largest lower East Rift Zone eruption and caldera collapse in at least 200 years.

The 2004–2005 Mt. Etna Compound Lava Flow Field: A Retrospective Analysis by Combining Remote and Field Methods

AbstractMapping lava flows frequently during effusive eruptions provides crucial parameters to better understand their dynamics, in turn improving our ability to model lava flow behavior. New photogrammetric methods have recently been developed, shifting the paradigm of photogrammetry from pure method to a multidisciplinary approach able to reduce the cost of volcanic monitoring and widen the potential spectrum of application. In this work, we demonstrate how multi‐view and single‐view photogrammetry methods can be used effectively to extract accurate quantitative information from photographs taken during routine surveys over an active lava flow. One intriguing advantage of these methods is that they can re‐use images acquired previously to extract new data from past eruptions. In particular, we reconstructed quantitatively the evolution of the lava flow field emplaced during 2004–2005 at Mt. Etna, subdivided in five eruptive phases from the earliest simple lava flows to the final compound lava field about 6 months later. Our results show that, in the first week of eruption, lava field formation was characterized by an increasing lava length that followed a power law growth and by a decreasing front velocity that followed a power law as well. Thereafter, the length increasing became almost constant until the developed lava tube system was able to drain the lava for long distances, with the area inundated by lava that grew linearly in the first 20 days. Finally, we demonstrate the crucial role that the syn‐eruptive DEMs acquisition could have to improve our understanding of the emplacement dynamics of complex lava fields.

The Estimation of Lava Flow Temperatures Using Landsat Night-Time Images: Case Studies from Eruptions of Mt. Etna and Stromboli (Sicily, Italy), Kīlauea (Hawaii Island), and Eyjafjallajökull and Holuhraun (Iceland)

Using satellite-based remote sensing to investigate volcanic eruptions is a common approach for preliminary research, chiefly because a great amount of freely available data can be effectively accessed. Here, Landsat 4-5TM, 7ETM+, and 8OLI night-time satellite images are used to estimate lava flow temperatures and radiation heat fluxes from selected volcanic eruptions worldwide. After retrieving the spectral radiance, the pixel values were transformed into temperatures using the calculated calibration constants. Results showed that the TIR and SWIR bands were saturated and unable to detect temperatures over the active lava flows. However, temperatures were effectively detected over the active lava flows in the range ~500–1060 °C applying the NIR-, red-, green- or blue-band. Application of the panchromatic band with 15 m resolution also revealed details of lava flow morphology. The calculated radiant heat flux for the lava flows accords with increasing cooling either with slope or with distance from the vent.

Correction to: The influence of cross-sectional channel geometry on rheology and flux estimates for active lava flows

The original version of this article unfortunately contained a mistake. The text accompanying Eq. 3 in the published paper should be corrected.

Mapping the Four‐Dimensional Viscosity Field of an Experimental Lava Flow

AbstractViscosity is a critical rheological property that determines the behavior, evolution, and final morphology of lava flows. Determining the viscosity of an active lava flow, however, is nontrivial. The rheological structure of lava is complex, and during active flow conditions, viscosity can change by orders of magnitude through space and time. This makes viscosity one of the most elusive properties of flowing lava. After almost a century of research on lava viscosity, it is still common practice to reduce the viscosity of a flow to a single value, generalizing an immense field of deviations and complexities. Considering lava viscosity as a one‐dimensional variable may be sufficient for characterizing some aspects of flows, but it does not allow for solving higher‐order rheological problems, such as depth structure, spatial variability, or rates of change. This study presents, for the first time, the four‐dimensional viscosity field of an actively flowing experimental lava. Results from this experiment include time‐series thickness, surface velocity, and temperature maps that are used to solve for the 4‐D viscosity of the lava flow with a spatial resolution of 2 cm. Additionally, the approach used in this study allows for an analysis of vertical rheological structure, specifically, crust and core viscosity layers. Although this study was performed in an experimental setting with crystal‐ and bubble‐free lava, the basic data collection techniques applied are common in field volcanology and thus could be applicable in certain natural settings.

The July/August 2019 Lava Flows at the Sciara del Fuoco, Stromboli–Analysis from Multi-Sensor Infrared Satellite Imagery

On 3 July 2019 a rapid sequence of paroxysmal explosions at the summit craters of Stromboli (Aeolian-Islands, Italy) occurred, followed by a period of intense Strombolian and effusive activity in July, and continuing until the end of August 2019. We present a joint analysis of multi-sensor infrared satellite imagery to investigate this eruption episode. Data from the Spinning-Enhanced-Visible-and-InfraRed-Imager (SEVIRI) was used in combination with those from the Multispectral-Instrument (MSI), the Operational-Land-Imager (OLI), the Advanced-Very High-Resolution-Radiometer (AVHRR), and the Visible-Infrared-Imaging-Radiometer-Suite (VIIRS). The analysis of infrared SEVIRI-data allowed us to detect eruption onset and to investigate short-term variations of thermal volcanic activity, providing information in agreement with that inferred by nighttime-AVHRR-observations. By using Sentinel-2-MSI and Landsat-8-OLI imagery, we better localized the active lava-flows. The latter were quantitatively characterized using infrared VIIRS-data, estimating an erupted lava volume of 6.33 × 10 6 ± 3.17 × 10 6 m3 and a mean output rate of 1.26 ± 0.63 m3/s for the July/August 2019 eruption period. The estimated mean-output-rate was higher than the ones in the 2002–2003 and 2014 Stromboli effusive eruptions, but was lower than in the 2007-eruption. These results confirmed that a multi-sensor-approach might provide a relevant contribution to investigate, monitor and characterize thermal volcanic activity in high-risk areas.

Constraining in situ cosmogenic nuclide paleo-production rates using sequential lava flows during a paleomagnetic field strength low

The geomagnetic field prevents a portion of incoming cosmic rays from reaching Earth’s atmosphere. During magnetic reversals and excursions, the field strength can decrease by up to 90% relative to the modern-day value. During such anomalies, cosmic ray bombardment to Earth’s atmosphere increases as evident from atmospheric 10Be anomalies recorded in sediment and ice cores. However, how the flux of cosmic rays to Earth’s surface varies during such geomagnetic anomalies is not well constrained. We measured fossil cosmogenic 3He in olivine from the tops of two pairs of 40Ar/39Ar age-dated Tahitian lava flows that erupted during the Matuyama-Brunhes reversal precursor event. We corrected these raw values for the diffusive loss of helium caused by heating from the overlying flow with a diffusion model using cooling rates and maximum temperature conditions based on field measurements of active lava flows from Kilauea, Hawaii. We assume the maximum temperature suggested by field measurements and thus present a limiting case for the highest diffusive loss corrections and thus the highest paleo-production rates. Based on paleomagnetic field strength reconstructions and scaling factor models, the upper limits of the corrected in situ3He paleo-production rates (100 ± 23, 144 ± 35 atoms g−1 a−1) are in agreement with those expected during the period of a geomagnetic field strength low when these flow tops were exposed. However, the more plausible contact temperatures (<700°C maximum temperature in diffusion model) are associated with diffusion corrected paleo-production rates lower than those predicted by scalar models. This potential underestimation is likely a function of changes in local non-dipole field components, atmospheric density and/or an overestimation of the dipole field strength reduction during the M-B precursor event.

Mapping Recent Lava Flows at Mount Etna Using Multispectral Sentinel-2 Images and Machine Learning Techniques

Accurate mapping of recent lava flows can provide significant insight into the development of flow fields that may aid in predicting future flow behavior. The task is challenging, due to both intrinsic properties of the phenomenon (e.g., lava flow resurfacing processes) and technical issues (e.g., the difficulty to survey a spatially extended lava flow with either aerial or ground instruments while avoiding hazardous locations). The huge amount of moderate to high resolution multispectral satellite data currently provides new opportunities for monitoring of extreme thermal events, such as eruptive phenomena. While retrieving boundaries of an active lava flow is relatively straightforward, problems arise when discriminating a recently cooled lava flow from older lava flow fields. Here, we present a new supervised classifier based on machine learning techniques to discriminate recent lava imaged in the MultiSpectral Imager (MSI) onboard Sentinel-2 satellite. Automated classification evaluates each pixel in a scene and then groups the pixels with similar values (e.g., digital number, reflectance, radiance) into a specified number of classes. Bands at the spatial resolution of 10 m (bands 2, 3, 4, 8) are used as input to the classifier. The training phase is performed on a small number of pixels manually labeled as covered by fresh lava, while the testing characterizes the entire lava flow field. Compared with ground-based measurements and actual lava flows of Mount Etna emplaced in 2017 and 2018, our automatic procedure provides excellent results in terms of accuracy, precision, and sensitivity.

The influence of emissivity on the thermo-rheological modeling of the channelized lava flows at Tolbachik volcano

The application of thermo-rheological models to forecast active lava flow emplacement and quantify the eruptive parameters of older flow-producing eruptions has become a somewhat common tool over the last decade. With the modification and adaption of these models to modular computing languages, they are now easier, quicker, and being incorporated into studies of both terrestrial and planetary volcanism. These models, such as FLOWGO, rely on numerous assumptions and input parameters, some of which such as radiant emissivity are not well understood for molten materials. Without a well-grounded knowledge of how this parameter governs radiant cooling, physics-based estimates of temperature and models such as FLOWGO that track cooling with time will be in error. Here, we perform a detailed FLOWGO-based modeling study of lava flows emplaced at Tolbachik volcano during the 2012-2013 and the 1975-1976 eruptions. Specifically, we have modified the FLOWGO model to incorporate a two-component emissivity model linked to the fraction of molten lava and cooled crust. We focus first on the large Leningradskoye Flow emplaced at the start of the 2012 eruption, relying on data from numerous other orbital sensors including MODIS, ASTER and ALI to constrain some of the model input parameters. The two-component emissivity adaption produced better fits to the final flow length and was found to be most significant for flows with lower percentages of initial crust cover. We then applied these results and model constraints to the large Cone II flow formed in 1975, for which no satellite-based constraining data are available. By knowing the final flow dimensions coupled with the constraints determined from the previous modeling, we were able to estimate an effusion rate (700 m 3 /s), initial velocity (1.5 to 2 m/s) and final viscosity (10 8 Pa·s). Interestingly, a nearly identical model fit was achieved with a higher effusion rate (1250 m 3 /s) and correspondingly lower crust cover. In this scenario, modeling the two-component emissivity was critical for accurate model results. This represents the first study to implement two-component emissivity into thermo-rheological modeling of lava flows. The results show that this is an important factor for model accuracy and critical for large, higher effusion rate flows as well as for our understanding of older, “data-limited” flows on Earth and other planets.

Space-Based Imaging Radar Studies of U.S. Volcanoes

The arrival of space-based imaging radar as a revolutionary land-surface mapping and monitoring tool little more than a quarter century ago enabled a spate of innovative volcano research worldwide. Soon after launch of European Space Agency’s ERS-1 spacecraft in 1991, the U.S. Geological Survey began SAR and InSAR studies of volcanoes in the Aleutian and Cascades arcs, in Hawaiʻi, and elsewhere in the western U.S. including the Yellowstone and Long Valley calderas. This paper summarizes results of that effort and presents new findings concerning: (1) prevalence of volcano deformation in the Aleutian and Cascade arcs; (2) surface-change detection and hazard assessment during eruptions at Aleutian and Hawaiian volcanoes; (3) geodetic imaging of magma storage and transport systems in Hawaiʻi; and (4) deformation sources and processes at the Yellowstone and Long Valley calderas. Surface deformation caused by a variety of processes is common in arc settings and could easily escape detection without systematic InSAR surveillance. Space-based SAR imaging of active lava flows and domes in remote or heavily vegetated settings, including during periods of bad weather and darkness, extends land-based monitoring capabilities and improves hazards assessments. At Kīlauea Volcano, comprehensive SAR and InSAR observations identify multiple magma storage zones beneath the summit area and along the East Rift Zone, and illuminate magma transport pathways. The same approach at Yellowstone tracks the ascent of magmatic volatiles from a mid-crustal intrusion to shallow depth and relates that process to increased hydrothermal activity at the surface. Together with recent and planned launches of highly capable imaging-radar satellites, these findings support an optimistic outlook for near-real time surveillance of volcanoes at global scale in the coming decade.

UAVs for volcano monitoring: A new approach applied on an active lava flow on Mt. Etna (Italy), during the 27 February–02 March 2017 eruption

Mt. Etna (Italy) with 55 effusive events in the last six years is one of the most active volcanoes in the world, with a million people living on its flank and thousands of tourists who visit it every summer.For this reason, the lava flow monitoring for risk mitigation and Civil Protection purposes is one of the fundamental tasks of the Cartographic Laboratory of the Istituto Nazionale di Geofisica e Vulcanologia, Osservatorio Etneo. This activity was traditionally performed using data collected from the field (with terrestrial GPS surveys) and from helicopter taking visible and thermal images. During the 27 February–02 March 2017 eruption the FlyEye Team, applied Unmanned Aerial Vehicles to monitor the active lava flow. Two high-resolution UAV surveys were performed on the lava flow field on the south flank of Mt. Etna, between 3050 and 2600 m a.s.l., obtaining almost 1170 images. Structure-from-Motion techniques were applied to create orthophotos and Digital Elevation Models (DEM) of the lava flow field and surroundings. The obtained DEM has a resolution of 14.2, and 20.7 cm/px for the main lava flow and the west branch, respectively. On the wall, the 96% of the lava flow field was mapped using aerial images by UAV covering an area of 0.3 × 106 m2. Lava flow volume was calculated with the topographic approach: difference between post- and pre-eruption surface, DEM 2017 and DEM 2014, respectively. The impossibility of spreading the GCPs homogenously distorted the resulting DEM; for this reason, it was necessary to align the lava flow point clouds, obtained from the photogrammetry software, to the basal 2014 DEM. Subtracting the two DEMs a lava flow thickness grid resulted leading to a total volume of 1.4 × 106 m3 and an error estimation of about 20%. Finally, dividing the total volume for the effusion duration (63 h) a mean output rate of 6.2 m3/s resulted. The calculated volcanological parameters have the same order of magnitude of the previous activity of Mt. Etna, between 2011 and 2016. This research demonstrates that UAV photogrammetry was successfully exploited during an eruptive crisis, allowing a first fast processing, to obtain an orthophoto of the lava flow field, useful for “decision makers” and a further slower processing for the realization of a high-resolution DEM. The latter makes it possible to update the topography, another important argument for Civil Protection purpose. This paper describes a methodology that could be applied during other natural events in extreme environmental conditions.

Assessment of Dual-Band method with Indoor Analog Experiment

The evaluation of infrared satellite images over active lava flows assists the identification of potentially threatened areas and thereby the overall lava inundation hazard assessment. The estimation of the lava flow's size and temperature is not trivial as the lava occupies only a small fraction (< 1 %) of a typically resolved target pixel (e. g. from Landsat 7, MODIS). Conventionally, this is solved by processing observations in at least two separate infrared spectral wavebands. We investigate the resolution limits of the Dual- Band method by means of a uniquely designed indoor analog experiment. A volcanic hotspot is simulated by an electrical heating alloy of 0.5 mm diameter installed on a plywood panel. Satellite observations are simulated by two thermographic cameras with wavebands comparable to those available from satellite data. These range from the short-wave infrared over the mid-wave infrared to the thermal infrared. In the conducted experiment, the hotspot’s pixel fraction was successively reduced by increasing the camera-to-target distance from 2 m to 38 m. We carried out three experiments with three different wire temperatures: 700 K, 920 K, and 1050 K. The estimated relative deviation between the observed and theoretical hotspot's pixel fraction is within 20 % for most distances. The estimated temperature of anomaly has stronger fluctuations.

3D Lava flow mapping of the 17–25 May 2016 Etna eruption using tri-stereo optical satellite data

During basaltic eruptions, the average rate at which lava is erupted (effusion rate) is one of the most important factor controlling the evolution, growth and extent of the flow field. This has implication both for forecasting purposes as input parameter into physics-based numerical models, and for advancing knowledge on the shallow feeder system by constraining the mass supplied. Satellite remote sensing provides a means to estimate the average effusion rate by applying a direct conversion from the measured radiant heat loss by an active lava flow. This conversion relies on a set of parameters of lava (e.g. rock density, heat capacity, vesicularity, emissivity, etc.) and suffers of multiple sources of uncertainties and measurements errors, whose quantification is still an open problem. Here we constrain the lava volume emitted at Mt Etna on 17-25 May 2016, by using pre-eruptive and post eruptive digital elevation models (DEMs) obtained processing satellite images acquired by the Pleiades constellation, which provides images at 50 cm resolution in stereo and tri-stereo mode. The 3D processing of the tri-stereo Pleiades imagery (acquired on 24 December 2015 and 18 July 2016), performed using the free and open source MicMac photogrammetric library provides estimations of the distribution of thickness and the bulk volume emitted. The integration of multi-platform remote sensing products represents a new potential of merging capabilities to enable a more comprehensive response to effusive crises.