scholarly journals The VEI 2 Christmas 2018 Etna Eruption: A Small But Intense Eruptive Event or the Starting Phase of a Larger One?

2020 ◽  
Vol 12 (6) ◽  
pp. 905 ◽  
Author(s):  
Sonia Calvari ◽  
Giuseppe Bilotta ◽  
Alessandro Bonaccorso ◽  
Tommaso Caltabiano ◽  
Annalisa Cappello ◽  
...  

The Etna flank eruption that started on 24 December 2018 lasted a few days and involved the opening of an eruptive fissure, accompanied by a seismic swarm and shallow earthquakes, significant SO2 flux release, and by large and widespread ground deformation, especially on the eastern flank of the volcano. Lava fountains and ash plumes from the uppermost eruptive fissure accompanied the opening stage, causing disruption to Catania International Airport, and were followed by a quiet lava effusion within the barren Valle del Bove depression until 27 December. This was the first flank eruption to occur at Etna in the last decade, during which eruptive activity was confined to the summit craters and resulted in lava fountains and lava flow output from the crater rims. In this paper, we used ground and satellite remote sensing techniques to describe the sequence of events, quantify the erupted volumes of lava, gas, and tephra, and assess volcanic hazards.

2020 ◽  
Author(s):  
Sonia Calvari ◽  
Giuseppe Bilotta ◽  
Alessandro Bonaccorso ◽  
Tommaso Caltabiano ◽  
Annalisa Cappello ◽  
...  

<p>The Etna flank eruption started on 24 December 2018 lasted a few days and involved the opening of an eruptive fissure, accompanied by a seismic swarm and shallow earthquakes, and by large and widespread ground deformation especially on the eastern flank of the volcano. Lava fountains and ash plume from the uppermost eruptive fissure have accompanied the opening stage causing disruption of Catania international airport, and have been followed by a quiet lava effusion within the barren Valle del Bove depression until 27 December. This is the first flank eruption occurring at Etna in the last decade, during which eruptive activity was confined to the summit craters and resulted in lava fountains and lava flow output from the crater rims. In this paper we use ground and satellite remote sensing techniques to describe the sequence of events, quantify the erupted volumes of lava, gas and tephra, and assess volcanic hazard.</p>


2021 ◽  
Vol 13 (15) ◽  
pp. 3052
Author(s):  
Sonia Calvari ◽  
Alessandro Bonaccorso ◽  
Gaetana Ganci

On 13 December 2020, Etna volcano entered a new eruptive phase, giving rise to a number of paroxysmal episodes involving increased Strombolian activity from the summit craters, lava fountains feeding several-km high eruptive columns and ash plumes, as well as lava flows. As of 2 August 2021, 57 such episodes have occurred in 2021, all of them from the New Southeast Crater (NSEC). Each paroxysmal episode lasted a few hours and was sometimes preceded (but more often followed) by lava flow output from the crater rim lasting a few hours. In this paper, we use remote sensing data from the ground and satellite, integrated with ground deformation data recorded by a high precision borehole strainmeter to characterize the 12 March 2021 eruptive episode, which was one of the most powerful (and best recorded) among that occurred since 13 December 2020. We describe the formation and growth of the lava fountains, and the way they feed the eruptive column and the ash plume, using data gathered from the INGV visible and thermal camera monitoring network, compared with satellite images. We show the growth of the lava flow field associated with the explosive phase obtained from a fixed thermal monitoring camera. We estimate the erupted volume of pyroclasts from the heights of the lava fountains measured by the cameras, and the erupted lava flow volume from the satellite-derived radiant heat flux. We compare all erupted volumes (pyroclasts plus lava flows) with the total erupted volume inferred from the volcano deflation recorded by the borehole strainmeter, obtaining a total erupted volume of ~3 × 106 m3 of magma constrained by the strainmeter. This volume comprises ~1.6 × 106 m3 of pyroclasts erupted during the lava fountain and 2.4 × 106 m3 of lava flow, with ~30% of the erupted pyroclasts being remobilized as rootless lava to feed the lava flows. The episode lasted 130 min and resulted in an eruption rate of ~385 m3 s−1 and caused the formation of an ash plume rising from the margins of the lava fountain that rose up to 12.6 km a.s.l. in ~1 h. The maximum elevation of the ash plume was well constrained by an empirical formula that can be used for prompt hazard assessment.


2020 ◽  
Author(s):  
Vincenzo De Novellis ◽  
Francesco Casu ◽  
Claudio De Luca ◽  
Mariarosaria Manzo ◽  
Fernando Monterroso ◽  
...  

<p>Piton de la Fournaise volcano forms the southeastern part of La Réunion, an oceanic basaltic island in the southernmost part of Mascarene Basin (Indian Ocean). Five eruptions occurred at Piton in 2019, accompanied by seismic activity, lava flow, and lava fountaining. Here below, we focus on the fourth eruption occurred between August 11 and 15 on the southern-southeastern flank of the volcano, inside the Enclos Fouqué caldera. This eruption was characterized by the opening of two eruptive fissures. We retrieve the surface deformations induced by the eruptive activity through space-borne Differential Synthetic Aperture Radar Interferometry (DInSAR) measurements. First, we generated the coseismic deformation maps by applying the DInSAR technique to SAR data collected along ascending and descending orbits by the Sentinel-1 constellation of the European Copernicus Programme. The DInSAR technique allows us to analyze the deformation patterns caused by the 11 August 2019 eruption. We also retrieved the pre-eruptive deformation through the Small BAseline Subset (SBAS) DInSAR approach. Then, we modelled the DInSAR displacements to constrain the geometry and characteristics of the eruptive source. The modelling results suggest that the observed deformation can be attributed to the interaction between a shallow magma reservoir located at ~1.5-2 km depth below the summit, and the intrusion of a dike feeding the eruptive fissure inside the Enclos Fouqué caldera.</p><p><em>This work is supported by: the 2019-2021 IREA-CNR and Italian Civil Protection Department agreement; the EPOS-SP project (GA 871121); and the I-AMICA (PONa3_00363) project.</em></p>


2012 ◽  
Vol 12 (12) ◽  
pp. 3683-3700 ◽  
Author(s):  
I. Galindo ◽  
A. Gudmundsson

Abstract. Most volcanic hazards depend on an injected dyke reaching the surface to form a feeder. Assessing the volcanic hazard in an area is thus related to understanding the condition for the formation of a feeder dyke in that area. For this latter, we need good field data on feeder dykes, their geometries, internal structures, and other characteristics that distinguish them from non-feeders. Unfortunately, feeder dykes are rarely observed, partly because they are commonly covered by their own products. For this reason, outcrops are scarce and usually restricted to cliffs, ravines, and man-made outcrops. Here we report the results of a study of feeder dykes in Tenerife (Canary Islands, Spain) and Iceland, focusing on their field characteristics and how their propagation is affected by existing structures. Although Holocene fissure eruptions have been common in both islands, only eleven basaltic feeder dykes have been identified: eight in Tenerife and three in Iceland. They are all well preserved and the relation with the eruptive fissure and/or the deposits is well exposed. While the eruptive fissures are generally longer in Iceland than in Tenerife, their feeders show many similarities, the main ones being that the feeder dykes (1) are generally sheet-shaped; (2) are segmented (as are the associated volcanic fissures); (3) normally contain elongated (prolate ellipsoidal) cavities in their central, topmost parts, that is, 2–3 m below the surface (with solidified magma drops on the cavity walls); (4) contain vesicles which increase in size and number close to the surface; (5) sometimes inject oblique dyke fingers into the planes of existing faults that cross the dyke paths; and (6) may reactivate, that is, trigger slip on existing faults. We analyse theoretically the feeder dyke of the 1991 Hekla eruption in Iceland. Our results indicate that during the initial peak in the effusion rate the opening (aperture) of the feeder dyke was as wide as 0.77 m, but quickly decreased to about 0.56 m. During the subsequent decline in the effusion rate to a minimum, the aperture decreased to about 0.19 m. At a later abrupt increase in the effusion rate, the feeder-dyke opening may have increased to about 0.34 m, and then decreased again as the effusion rate gradually declined during the end stages of the eruption. These thickness estimates fit well with those of many feeders in Iceland and Tenerife, and with the general dyke thickness within fossil central volcanoes in Iceland.


2020 ◽  
Author(s):  
Benoît Smets ◽  
Josué Subira ◽  
Antoine Dille ◽  
Nicolas Theys ◽  
Fran Broekmans ◽  
...  

<p>Since its last flank eruption in 2011-2012, the activity of Nyamulagira volcano (Virunga Volcanic Province, DR Congo) has been characterized by pit crater collapse, lava fountaining and intermittent lava lake activity. No more flank eruption occurred since this concentration of the eruptive activity at the summit. As Nyamulagira is located in a remote area of the Virunga National Park, field observations remain limited. As a consequence, observations of the ongoing changes at the summit of the volcano mostly rely on satellite observations. Time-series of very-high to high resolution optical and SAR amplitude images for instance provide the required information to follow the evolution of the pit crater, from the first signs of collapse to its filling by lava. Hotspot detection from the combination of MODIS and Landsat-type images (including Sentinel-2) allows detecting the first appearance of lava in the pit crater and describing the intermittence of the lava lake activity that has developed since 2014. The OMI and TROPOMI instruments allow measuring the evolution of SO<sub>2</sub> emissions. Thanks to few aerial surveys and the use of Unoccupied Aerial Systems (UAS or “drone”), the volume of lava accumulated within the pit crater since 2014 was measured. All these satellite and drone-based observations were finally compared with the known historical eruptive activity, in terms of lava and gas discharge rates and type of summit eruptive activity. The presented work shows how combining various remote sensing techniques that make use of recent generations of satellite images and UAS acquisitions allow a detailed interpretation of the evolution of the volcano, even when field access is an issue.</p><div> </div>


2021 ◽  
Author(s):  
Alejandra Vásquez-Castillo ◽  
Matthias Hort

<p>Surface displacements recorded in volcanically active regions are often driven by magmatic, hydrothermal or tectonic processes. Measuring the deformation experienced by the ground as a result of these processes allows to constrain the changing volcanic conditions and to infer quantitative estimates of the subsurface magmatic storage, thus increasing the knowledge of volcanic hazards for the closest local population. Interferometric synthetic aperture radar (InSAR) has proven to be an useful tool to observe ground deformation in volcanically active areas like the Sakurajima volcano, southern Japan, one of the most active volcanoes worldwide. Its current activity is characterized by degassing and almost daily explosive eruptions. We performed an InSAR time series analysis to identify and characterize time-dependent ground deformation using Sentinel-1 data between 2015 and 2020. During this period several large explosions with plume heights of up to 6000 m occurred. We found evidence of ground deformation associated with precursory inflation connected to major explosions. In addition, we processed interferograms spanning a remarkable event that occurred on August 15 2015, in which we identified strong deformation around the Showa crater, in agreement with previous studies.</p>


Author(s):  
Grant Heiken

Between 50 and 70 volcanoes erupt each year—just a fraction of the 1,000 identified volcanoes that may erupt in the near future. When compared with the catastrophic loss of lives and property resulting from typhoons, earthquakes, and floods, losses from the more infrequent but equally devastating volcanic eruptions are often overlooked. Volcanic events are usually dramatic, but their various effects may occur almost imperceptibly or with horrendous speed and destruction. The intermittent nature of this activity makes it difficult to maintain public awareness of the risks. Assessing volcanic hazards and their risks remains a major challenge for volcanologists. Several generations ago, only a small, international fraternity of volcanologists was involved in the complex and sometimes dangerous business of studying volcanoes. To understand eruptions required extensive fieldwork and analysis of the eruption products—a painstaking process. Consequently, most of the world’s volcanoes had not been studied, and many were not yet even recognized. Volcano research was meagerly supported by some universities and a handful of government-sponsored geological surveys. Despite the threats posed by volcanoes, few volcanological observatories had been established to monitor their activity. Volcanology is now a global venture. Gone are the days when volcanologists were educated or employed chiefly by the industrial nations. Today, volcanologists and geological surveys are located in many nations with active volcanoes. Volcanological meetings, once limited to geologists, geophysicists, and a smattering of meteorologists and disaster planners, have greatly expanded. Initially, it was a hard sell to convince volcanologists that professionals from the “soft sciences” could contribute to the broad discipline of volcanology. However, it has become clear that involving decision makers such as urban planners, politicians, and public health professionals with volcanologists is a must when exploring and developing practical, effective volcanic-risk mitigation. Beginning in 1995, the “Cities on Volcanoes” meetings were organized to introduce an integrated approach that would eventually help mitigate the risks of volcanic eruptions. The first conference, held in Rome and Naples, Italy, encompassed a broad spectrum of topics from the fields of volcanology, geographic information systems, public health, remote sensing, risk analysis, civil engineering, sociology and psychology, civil defense, city management, city planning, education, the media, the insurance industry, and infrastructure management. The stated mission of that meeting was to “better evaluate volcanic crisis preparedness and emergency management in cities and densely populated areas.” Since that meeting nearly twenty years ago, Cities on Volcanoes meetings have taken place in New Zealand, Hawaii, Ecuador, Japan, Spain, and Mexico; the 2014 venue was Yogyakarta, Indonesia. The significant and rewarding result of these efforts is a growing connection between basic science and the practical applications needed to better understand the myriad risks as well as the possible hazard mitigation strategies associated with volcanic eruptions. While we pursue this integrated approach, we see advances in the technologies needed to evaluate and monitor volcanoes. It is impossible to visit all the world’s restless volcanoes, let alone establish effective monitoring stations for most of them. However, we can now scrutinize their thermal signatures and local ground deformation with instruments on earth-observing satellites. When precursory activity is detected by remote sensors in an area where a population is at risk, teams can be deployed for ground-based monitoring of that activity. In addition, by evaluating a volcano’s past eruption history, scientists can forecast both future activity and the possible risks to inhabitants. Using physics-based modeling, there is a better understanding of the types and severity of potential eruption phenomena such as pyroclastic flows, ash eruptions, gaseous discharge, and lava flows. Field observations of changes indicating an imminent eruption are now monitored with geophysical and geochemical instrumentation that is smaller, tougher, and more affordable. Volcanology has evolved into a broader, integrated scientific discipline, but there is much still to be accomplished. The new generation of volcanologists, who have the advantage of knowing the theoretical underpinnings of volcanic activity, can now turn to the allied endeavor of reducing risk—their aspiration for the 21st century.


2021 ◽  
Vol 13 (9) ◽  
pp. 1684
Author(s):  
Matteo Del Soldato ◽  
Pierluigi Confuorto ◽  
Silvia Bianchini ◽  
Paolo Sbarra ◽  
Nicola Casagli

The Global Navigation Satellite System (GNSS) and Synthetic Aperture Radar Interferometry (InSAR) can be combined to achieve different goals, owing to their main principles. Both enable the collection of information about ground deformation due to the differences of two consequent acquisitions. Their variable applications, even if strictly related to ground deformation and water vapor determination, have encouraged the scientific community to combine GNSS and InSAR data and their derivable products. In this work, more than 190 scientific contributions were collected spanning the whole European continent. The spatial and temporal distribution of such studies, as well as the distinction in different fields of application, were analyzed. Research in Italy, as the most represented nation, with 47 scientific contributions, has been dedicated to the spatial and temporal distribution of its studied phenomena. The state-of-the-art of the various applications of these two combined techniques can improve the knowledge of the scientific community and help in the further development of new approaches or additional applications in different fields. The demonstrated usefulness and versability of the combination of GNSS and InSAR remote sensing techniques for different purposes, as well as the availability of free data, EUREF and GMS (Ground Motion Service), and the possibility of overcoming some limitations of these techniques through their combination suggest an increasingly widespread approach.


2021 ◽  
Vol 64 (5) ◽  
pp. VO543
Author(s):  
Stefano Branca ◽  
Daniele Musumeci ◽  
Luigi Ingaliso

The 1971 eruption represents a benchmark in the recent history of Etna volcano. From a volcanological point of view, this eruption was characterised by complex intrusive dynamics associated with significant ground deformation that induced the activation of the Moscarello seismogenic fault and the formation of a new summit crater: the Southeast Crater. At the same time, the 1971 event marks an important change in the eruptive style and composition of the magma towards products richer in K. It is no coincidence that, over the next fifty years, there would be an increase in the frequency of summit and flank eruptions and associated output rate. From an historical viewpoint, the eruptive event of 1971 was the first important flank eruption studied by the International Institute of Volcanology: the analysis of the scientific articles on this activity reveals a greater multidisciplinary content in the descriptions and explanations of volcanic activity. Particularly important were the collaborations of British and French research groups that, together with their Italian colleagues, succeeded in giving a complete picture of the eruption and describing the state of knowledge on the Sicilian volcano. The multidisciplinary methodology used to study this  eruption is still valid today.


2020 ◽  
Author(s):  
Marco Aloisi ◽  
Alessandro Bonaccorso ◽  
Flavio Cannavò ◽  
Gilda Currenti ◽  
Salvatore Gambino

<p>In the previous EGU 2019 we presented the different data acquired by the multi-disciplinary deformation networks during the eruption of Etna on 24 December 2018, when the volcano was suddenly penetrated by a violent dyke intrusion. An eruptive fissure opened and continued to propagate southward for more than 10 hours. The situation created the fear of possible serious consequences of feeding a lava flow even at medium-low altitudes, therefore potentially hazardous for the villages and infrastructures located there. However, the propagation stopped and lava flows finished on 25 December.</p><p>In this updated study we present the effort made to model the complex eruptive process characterized by two attempts of intrusion. We inferred a first dyke starting from the sea level depth with an increasing of its dimension in the shallower part. Successively and until the early hours of 25 December, we revealed a second attempt of intrusion characterized by a dyke with a powerful opening with respect to the first dyke but that, fortunately, did not reach the free surface. We describe how different types of continuous deformation data provide complementary information on the ongoing process allowing us to model the fast intrusive process. In particular, the high-precision borehole instruments (strainmeters and tiltmeters) provided a robust early warning; the displacement field measured by high-rate GPS allowed obtaining an early but also reliable model of the source. Finally, the integration of all the continuous data constrained a more detailed and complete model and its time evolution able to represent the complex process leading to this flank eruption.</p><p> </p>


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