The significance of the 1971 flank eruption of Etna from volcanological and historic viewpoints

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.

KLYUCHEVSKOY VOLCANO: NEW FLANK ERUPTION NAMED AFTER G.S. GORSHKOV, 2021 (KAMCHATKA)

February 18, 2021, a flank eruption started on the north-western slope of the Klyuchevskoy Volcano (Kamchatka, Russia). Cinder cone was formed at the altitude of 2 850 m above sea level, from which a lava flow was spreading north-west. Having moved 1.2 km downslope, the lava flow entered the Ehrmann Glacier, which resulted in the formation of huge mud-stone flows. The latter made their way further north-east along the Kruten’kaya River bed and reached the length of about 30 km. The eruption brought onto the surface high-aluminous basaltic andesites typical of the Klyuchevskoy Volcano. By March 21, the flank eruption ended. It has been named after G.S. Gorshkov, associate member of USSR Academy of Science, famous Russian volcanologist.

The cascading origin of the 2018 Kīlauea eruption and implications for future forecasting

The 2018 summit and flank eruption of Kīlauea Volcano was one of the largest volcanic events in Hawaiʻi in 200 years. Data suggest that a backup in the magma plumbing system at the long-lived Puʻu ʻŌʻō eruption site caused widespread pressurization in the volcano, driving magma into the lower flank. The eruption evolved, and its impact expanded, as a sequence of cascading events, allowing relatively minor changes at Puʻu ʻŌʻō to cause major destruction and historic changes across the volcano. Eruption forecasting is inherently challenging in cascading scenarios where magmatic systems may prime gradually and trigger on small events.

Pressure conditions in coupled magma bodies and their evolution during eruptions and caldera collapse: Piton de la Fournaise 2007

<p>Understanding the interplay between pressure evolution in magma bodies in volcano roots and caldera collapses is important to for the general understanding of volcanoes and how calderas form. We use lessons-learned regarding caldera collapse dynamics and inferred 2014-2015 pressure evolution in a magma body under the Bardarbunga caldera, Iceland, to revisit the dynamics of the 2007 caldera collapse at Piton de La Fournaise volcano, La Reunion, in a project supported by EUROVOLC trans-national access. At Piton de la Fournaise, (rising to 2632 m above sea leve) a shallow and small magma body (close to sea-level; volume less than one cubic kilometer) played a central role. The overpressure compared to lithostatic prior to collapse is inferred to have been small (< 5 MPa), based on models of driving pressure for minor eruptions that occurred on 18-19 February and 30 March prior to the caldera forming lateral flank eruption that occurred 2 April – 1 May, 2007. The site of the lateral flank eruption occurred at an elevation of 500 m, much lower than the summit.  This elevation difference is inferred to a key factor for creating high driving pressure for magma flow. We infer that rapid flow of magma led to fast drop in pressure in a shallow magma body under the caldera, triggering inflow of magma from a deeper magma body under Piton de la Fournaise, that was in important element of the 2007 eruptive activity.  This deep inflow did, however, not sustain enough the pressure in the shallow magma body during the eruption, causing development of significant under-pressure leading to the collapse.</p>

Study of the 2012-2020 pit crater evolution in the summit caldera of Nyamulagira volcano using multiple satellite sensors and UAS-based photogrammetry

<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>

The VEI 2 Christmas 2018 Etna Eruption: A small but intense eruptive event or the starting phase of a larger one?

<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>

Modeling of the Dec 24, 2018 eruptive intrusion at Etna volcano by data of multi-disciplinary continuous deformation networks (CGPS, borehole strainmeters and tiltmeters)

<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>