Copernicus Sentinels monitor Etna's various eruptions - Sentinel Success Stories
Copernicus Sentinels monitor Etna's various eruptions
21 April 2021
With Europe's tallest active volcano of 3325 metres frequently erupting, volcanology experts are using data from the Copernicus Sentinels to monitor the situation for environmental and safety impacts, since its various recent explosions.
On 16 February 2021, one of the world's most active volcanoes, Italy's Mount Etna, erupted twice in less than 48 hours, cascading a fountain of lava and ash into the sky.
The first eruption caused large lava flows to descend eastwards into the Valle del Bove, travelling for approximately 4 km, but the second major explosion on 18 February caused the lava also to run for about 1.3 km down the volcano's southern flanks.
Ash from the eruptions covered the city of Catania, so authorities monitored developments in the nearby towns at the base of the volcano. The eruption also forced the temporary shutting of Sicily's Catania Airport, which often happens when the volcano is active.
Satellite data, like those from the Sentinels of the European Union’s Copernicus Programme can be used to detect the slight signs of change that could foretell an eruption. Once an eruption begins, optical and radar instruments can capture the various phenomena associated with it, including lava flows, mudslides, ground fissures and earthquakes. Atmospheric sensors on satellites can also identify the gases and aerosols released by the eruption, as well as quantify their wider environmental impact.
As of 25 March, there have been a total of 17 paroxysms – brief episodes of violent explosive activity including high lava fountains, eruption columns up to 10-12 km tall, and lava flows rapidly expanding on the upper slopes of the volcano. Like some of its predecessors, the latest paroxysm, during the night of 23-24 March, also produced a small pyroclastic flow, once more putting Etna’s vast repertoire of eruptive phenomena on display.
Changes in surface deformation, such as sinking, bulging and rising, are indicators of different stages of volcanic activity, which may result in eruptions. Thus, precise monitoring of a volcano’s surface deformation, or 'breathing', could lead to predictions of eruptions.
Using advanced SAR Interferometry (InSAR) techniques, like those applicable to Copernicus Sentinel-1, data users can obtain crucial information for understanding how the volcano’s surface deforms during the rise, storage and eruption of magma.
Copernicus Sentinel-1 A and -B data are routinely used by Etna's INGV Observatory, in Catania, Sicily, for monitoring the evolution of the ground deformations of Mt. Etna, together with the multiparametric monitoring INGV system (GNSS, tilt and strain stations).
In a nutshell, the dynamics of this volcano are characterised by a superimposition of effects of the magma movements within the volcanic structure (either at the summit craters or below the flanks), and the local tectonics (faults and persistent flank motion).
InSAR allows measuring and discriminating the different effects, owing to its capability of entirely covering Mt. Etna during a single pass of the radar. The current eruptive phase was anticipated by a rather continuous period of “inflation”, involving the entire volcano, which started after the end of December 2018’s eruption (Bonforte et al, 2019), briefly interrupted in 2019 (May and July) and in 2020 (May and December), in coincidence with episodes of volcanic activities at the summit craters.
The inflation was produced by the continuous arrival of new magma in the volcanic plumbing system. The time series analysis of the Copernicus Sentinel-1 A and -B data shows the inflation as well as the effects of the local tectonics.
The lava fountain episodes that started on 16 February 2021, are accompanied by a strong deflation involving the entire volcano clearly related to the erupted magma.
Optical measurements, from ultraviolet-UV to thermal infrared-TIR, can be used for monitoring of volcanic clouds. The presence of these clouds in the atmosphere affect air quality, environment, climate, human health, and can be extremely dangerous for aviation safety.
Detection and retrievals of volcanic particles and sulphur dioxide (SO2) are thus important for risk mitigation as well as to give insight into the mechanisms that cause eruptions. In particular, the thermal infrared channels of Copernicus Sentinel-3's SLSTR (Sea and Land Surface Temperature Radiometer) can be used for both day and night monitoring of volcanic ash and ice particles, while the UV channels of Copernicus Sentinel-5P’s TROPOMI are exploited for SO2 columnar abundance retrievals, as shown in the featured images.
The SLSTR image shows the ash and ice particles detection and retrieval obtained from the image acquired on 7 March 2021, at 08:57 UTC. The upper plates show the Brightness Temperature Difference-BTD computed as the difference between the Brightness Temperature of the SLSTR channels centred at 10.8 and 12 µm. This procedure exploits the different spectral absorption between ash and ice that lead to a negative and positive BTD values, in case of ash and ice respectively. In the lower plates, the ash (left in image) and ice (right) columnar abundance retrieved are shown.
The other image shows Copernicus Sentinel-5P’s TROPOMI SO2 detection and retrievals obtained from several Etna events. TROPOMI’s high sensitivity increases significantly the possibility to reveal previously undetectable sulphur dioxide.
The accurate mapping of the lava flows provides an insight into the development of flow fields that may aid in predicting future flow behaviour. This 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 availability of Copernicus Sentinel-2 imagery allows to safely and comprehensively monitor these eruptive phenomena.
Dr Stefano Corradini, Atmospheric Physicist and researcher at INGV, states, "The examples shown demonstrate the ability of the Copernicus Sentinel's satellite sensors to continuously monitor volcanic activity from the source to the atmosphere, during both day and night. This capability offers a powerful tool to mitigate volcanic risks on local population and airspace, while also giving insight of volcanic processes."
About the Copernicus Sentinels
The Copernicus Sentinels are a fleet of dedicated EU-owned satellites, designed to deliver the wealth of data and imagery that are central to the European Union's Copernicus environmental programme.
The European Commission leads and coordinates this programme, to improve the management of the environment, safeguarding lives every day. ESA is in charge of the space component, responsible for developing the family of Copernicus Sentinel satellites on behalf of the European Union and ensuring the flow of data for the Copernicus services, while the operations of the Copernicus Sentinels have been entrusted to ESA and EUMETSAT.
Did you know that?
Earth observation data from the Copernicus Sentinel satellites are fed into the Copernicus Services. First launched in 2012 with the Land Monitoring and Emergency Management services, these services provide free and open support, in six different thematic areas.
For instance, the Copernicus Atmosphere Monitoring Service (CAMS) provides continuous data and information on atmospheric composition. It supports many applications in a variety of domains including health, environmental monitoring, renewable energies, meteorology and climatology.
Whilst the European Ground Motion Service (EGMS), part of the Copernicus Land Monitoring Service (CLMS), aims to provide consistent, regular, standardised, harmonised and reliable information regarding natural and anthropogenic ground motion phenomena, over Europe and across national borders, with millimetre accuracy.
Guerrieri, L.; Merucci, L.; Corradini, S.; Pugnaghi, S. Evolution of the 2011 Mt. Etna ash and SO2 lava fountain episodes using SEVIRI data and VPR retrieval approach. J. Volcanol. Geotherm. Res. 2015, 291, 63–71.
Pugnaghi, S.; Guerrieri, L.; Corradini, S.; Merucci, L.; Arvani, B. A new simplified procedure for the simultaneous SO2 and ash retrieval in a tropospheric volcanic cloud. Atmos. Meas. Tech. 2013, 6, 1315–1327.
Pugnaghi, S.; Guerrieri, L.; Corradini, S.; Merucci, L. Real time retrieval of volcanic cloud particles and SO2 by satellite using an improved simplified approach. Atmos. Meas. Tech., 2016. 9, 1–10. doi: 10.5194/amt-9-3053-2016
N. Theys, I. De Smedt, H. Yu, T. Danckaert, J. van Gent, C. Hörmann, T. Wagner, P. Hedelt, H. Bauer, F. Romahn, M. Pedergnana, D. Loyola, M. Van Roozendael : Sulfur dioxide operational retrievals from TROPOMI onboard Sentinel-5 Precursor: Algorithm Theoretical Basis, Atmos. Meas. Tech., 10, 119-153, doi:10.5194/amt-10-119-2017, 2017.
Theys, N., Hedelt, P., De Smedt, I. et al. Global monitoring of volcanic SO2 degassing with unprecedented resolution from TROPOMI onboard Sentinel-5 Precursor. Sci Rep 9, 2643 (2019). https://doi.org/10.1038/s41598-019-39279-y