Thirteen institutions are currently the reference entities for operational volcano monitoring of volcanoes in Europe and its overseas territories (OT) as shown in Figure 1. Amongst those, nine are officially recognized as SVO with defined responsibilities towards the aviation community, offering a 24/7 surveillance service. These nine are listed in the updated IAVW Handbook which will be published online in 2023 (Paula Acethorp, personal communication) highlighted green in Table 2. Four institutions are in the process of defining the role through their governing State agreements and progress has been made towards the formalisation of responsibilities (light green in Table 2).
CIVISA-IVAR
The Centre for Information and Seismo-volcanic Surveillance of the Azores (CIVISA) is a private non-profit association of two partners: the Autonomous Region of the Azores and the University of the Azores. It was created in 2008 with the aim of implementing an integrated service for the permanent monitoring and assessment of geological hazards in the Azores region, following the Resolution of the Council of the Government No. 84/2008, of 12 June. At the national level, CIVISA falls under Article 66 (Public safety and civil protection) of the Portuguese Law No. 2/2009, of 12 January, which approves the Political-Administrative Statute of the Autonomous Region of the Azores.
CIVISA is the operational branch of the Research Institute for Volcanology and Risk Assessment (IVAR) of the University of the Azores, which provides technical and scientific advice to the Azores Regional Civil Protection and Fire Services (SRPCBA) and other local civil protection authorities. CIVISA comprises seven Operational Scientific Units (Hydrogeology, Hydrometeorology, Gas Geochemistry, Infrasound, Seismology and Geodesy, Volcanology, and Crisis Management and Response Mechanisms) and a Crisis Office, which is activated in response to emergency situations. CIVISA manages a multiparametric monitoring system composed of several permanent networks (seismic, gas geochemistry, GNSS, and meteorological and hydrometric) spread over the different islands of the archipelago. All data are transmitted in real- or near real-time to the Data Acquisition Centre (CAD) (Fig. 2) in CIVISA’s headquarters, located at the IVAR premises in the University of the Azores in Ponta Delgada, São Miguel Island. The information acquired by the permanent networks is complemented by regular monitoring campaigns (gas and water sampling, GNSS observations, kinematics of unstable slopes, etc.) and, if necessary, temporary stations installed during periods of increased seismic or seismo-volcanic activity. The CAD staff ensures monitoring activities 24/7 through shifts of 8 hours and is also responsible for verifying the good operation of the monitoring networks. Working side-by-side with CAD, the Emergency Operations Centre (COE; Fig. 2) is responsible for the integration of all data acquired by the multiparametric monitoring system and ensures communication with SRPCBA and local civil protection authorities, as well as national and international entities, such as Toulouse VAAC. It also maintains an integrated GIS platform that supports crisis management and emergency planning. The COE staff work 24/7 remotely in quiet periods, and 24/7 in person during periods of unrest.
CIVISA-IVAR is responsible for monitoring all islands of the Azores archipelago and the surrounding underwater area (Fig. 1 - green area). In its area of responsibility there are 50 seismogenic zones and 26 active volcanoes and volcanic systems, 18 of which are subaerial, in all islands of the Azores except in Santa Maria, where volcanism is considered extinct. The other eight volcanic systems are submarine.
The ACC system is in place at CIVISA-IVAR and has been regularly trained in joint exercises with Toulouse VAAC, Santa Maria Area Control Center and Meteorological Weather Office (Portuguese Institute for Sea and Atmosphere - IPMA). In the past 15 years, CIVISA-IVAR participated in 16 exercises at both national and international levels (VOLCAZO and VOLCEX exercises, respectively). In all exercises, VONAs were issued, gradually changing the ACC from green to red, with the aim of simulating increasing volcanic unrest that culminates in the explosive eruption of selected volcanoes. Over the years, these exercises were focused on the trachytic central volcanoes of the archipelago, because they are considered the most hazardous for air traffic: Sete Cidades (Pimentel, 2021a), Água de Pau (also known as Fogo, Pimentel, 2021b) and Furnas, on São Miguel Island; Caldeira on Faial Island; and Santa Bárbara on Terceira Island.
In real unrest situations, the change of the ACC for the different volcanoes or volcanic systems is decided by the Crisis Office of CIVISA, which comprises the President of the Board of Directors and the coordinators of the Operational Scientific Units. The Crisis Office is responsible for assessing each unrest episode, based on the analysis of all available data, and deciding on the change of alert levels.
The definition of the state of a volcano or volcanic system in the Azores region (i.e., the alert level) follows CIVISA’s scientific alert scale, which is available at www.ivar.azores.gov.pt/civisa/Paginas/alerta-sismovulcanico.aspx. This scale includes seven alert levels, ranging from V0 when the volcano is in normal, quiet state to V6 for the case of a paroxysmal eruption. The change of scientific alert level is based on the integrated analysis of the monitored parameters (geophysical, geodetic, and geochemical), as well as on the correlations between them. The increase in alert level may occur over timescales of years or months, or just a few hours, depending on the rate at which the unrest escalates. Following the scientific alert scale, the Crisis Office decides on the change of the ACC for a given volcano or volcanic system.
Since 2008, CIVISA-IVAR issued only two real VONAs changing the ACC for São Jorge Island in 2022 due to an ongoing seismo-volcanic crisis. Before that, the state of Azorean volcanoes or volcanic systems did not justify the change of the ACC, despite several episodes of higher seismic activity.
IGN
The Instituto Geográfico Nacional (IGN) is the centre in charge of volcano monitoring and volcanic alerts in Spain since 2004. The volcanic monitoring group is currently composed of about 35 people. IGN operates a 24/7 shift mainly dedicated to seismic monitoring, but during eruptions, also to volcano monitoring (Fig. 3). The IGN's area of responsibility in volcanology covers the entire national territory, being the Canary Islands the only area with historical volcanic activity (Fig. 1 - blue area). In the Iberian Peninsula there are two areas that according to dating could be considered active: La Garrotxa area (Girona, Zafrilla et al. 2021a) and Campos de Calatrava (Ciudad Real). In the framework of the Spanish Polar Committee, the IGN was appointed in 2020 to be responsible for volcanic monitoring and warning on Deception Island (South Shetland, Antarctica). The volcano monitoring network deployed by IGN is mainly focused on the Canary Islands archipelago and consists of a geophysical, geodetical and geochemical system plus observational cameras, magnetometers and gravimeters.
Canary Islands is an active volcanic area with a rather low eruptive frequency: about 3 eruptions per century (based on historical eruption data). This fact implies that the experience in instrumental monitoring of eruptive processes in Spain is limited to two cases: the submarine eruption of Tagoro volcano on the island of El Hierro in 2011-2012 (Lopez et al. 2012) and the recent eruption of 2021 on the island of La Palma (Del Fresno et al. 2023). Of these two cases, only in the latter one was ash emitted into the atmosphere.
IGN’s knowledge about the aviation colour code system was based on ICAO documentation and the experience transmitted by staff from other Volcanic Observatories both in VOLCEX preparatory meetings and VAAC-VO workshops organised by the EUROVOLC project. In November 2022, a Spanish volcano (Teide, Zafrilla et al. 2021b) was for the first time the target volcano within the European exercise VOLCEX22. Moreover no exercises were ever held at a national level to practise response to a volcanic unrest/eruption. Unfortunately, the exercise planned by IGN and VAAC Toulouse for 2020 had to be cancelled because of the COVID-19 pandemic. Therefore, when the 2021 eruption in La Palma started, almost no member of the team in charge of measuring the height of the eruptive column and for issuance of VONAs had previous experience or training in the use of the ACC. During the 2021 eruption, the decision to change the ACC was taken by consensus of a small group of 3-4 scientists and technicians, in which there was always at least one person present on the island of La Palma. Given the current lack of experience and training, it was not easy in some cases to decide between orange and red.
INGV
Both the Osservatorio Etneo (INGV-OE) and Osservatorio Vesuviano (INGV-OV) are part of the Istituto Nazionale di Geofisica e Vulcanologia, the institution in charge of the seismic and volcano monitoring and surveillance in Italy supporting the Italian Civil Protection Department (DPC).
INGV-OV
INGV-OV manages seismic and volcano monitoring and surveillance in the Neapolitan area which include Vesuvius (Di Vito, 2021), Campi Flegrei (Di Vito and Doronzo, 2021) and Ischia Island (Fig.1 - orange area). INGV-OV has a 24/7 Operation Room (Fig. 4), hardware and software infrastructures for the acquisition, storage systems and real time analysis, to enable management and utilisation of multi-parametric data for monitoring and surveillance purposes. The 24/7 surveillance is ensured by the presence of two shift workers and by 3 other units of highly specialised staff on call: a seismologist, a volcanologist/geochemist and a computer scientist. Although not erupting recently, the volcanoes in the Neapolitan area are considered high-risk due the possibility of high-energy eruptions and the intense urbanisation. The last eruption of Vesuvius occurred in 1944, showing both effusive and explosive eruption styles. Campi Flegrei has been in an unrest state (“Attention Level”) since 2012 because of the continuous uplift observed in the area. Ischia produces very shallow earthquakes (less than one km) with catastrophic consequences (last earthquake in 2017 caused 2 fatalities and more than 2600 persons to become homeless). In case of reactivation of one of the volcanoes, the main potentially affected airports are Capodichino in Napoli, and probably airports in Rome if the winds are blowing towards the North. INGV-OV has developed a volcanic ash forecasting system which is able, using automatic procedures, to download daily data from meteorological weather forecasts, run models of tephra dispersal for Vesuvius (three scenarios) and Campi Flegrei (one scenario), and store the ash loadings for off-line analysis of the impact on buildings and infrastructures. VONA messages have been issued since 2017 for the Aviation Exercises, VOLCITA and VOLCEX in 2017, 2018 and 2019. The volcanologist on duty is in charge of sending the VONA messages and of changing the Aviation Colour Code (ACC) on the basis of the volcanic activity. Since the Neapolitan volcanoes have been quiet for many years, no VONA have been issued outside the national or international exercises.
INGV-OE
Since 2000, INGV-OE has managed seismic and volcano monitoring and surveillance in the Sicilian territory (Etna and Aeolian islands) (Fig.1 - red area) and seven years later, it was appointed to be a “State Volcano Observatory”. INGV-OE has a 24/7 Operation Room (Figure 5), comprising hardware and software infrastructures for the acquisition, storage systems and real time analysis, to enable management and utilisation of multi-parametric data for monitoring and surveillance purposes (D’Agostino et al., 2013). The 24/7 surveillance is ensured by the presence of two shift workers and by another eight units of highly specialised staff on call: two seismologists; two volcanologists (Volcanologist 1 and 2) supported by one researcher/technician who goes into the field; two technicians; one expert on computer science; one technician working at the Geophysical Observatory in Lipari. One of the volcanologists is in charge of the communications sent to the DPC regarding volcanic activity. Moreover, he/she writes the Volcano Observatory Notices for Aviation (VONA) messages that are sent to several national and international authorities (e.g. the Toulouse Volcanic Ash Advisory Centre, National and Regional Civil Protection Departments). The other volcanologist does fieldwork, takes samples and performs any volcanological observations which could be useful for drafting the INGV-OE reports.
Etna is one of the most active volcanoes in the world (Branca, 2021), with more than one hundred lava fountain events produced in the last ten years. Those events formed high plumes, rising up to 15 km, and notably affecting the population and aviation operations (Barsotti et al., 2010; Scollo et al., 2013). In fact, the International Airport of Catania is only 30 km away from the Etna summit craters. From 2006, INGV-OE has developed a volcanic ash forecasting system which is able, using automatic procedures, to download daily data from meteorological weather forecasts, run models of tephra dispersal, plot hazard maps of volcanic ash dispersal and deposition for some fixed eruptive scenarios considered as end-members of Etna volcanic activity, and sends the results to the Italian Civil Protection (Scollo et al., 2009). The system has been continually improved thanks to the extensive use of remote sensing systems ranging from radar (Freret-Lorgeril et al., 2018, Giammello et al., 2021, Mereu et al., 2022), lidar (Scollo et al., 2012) and cameras (Scollo et al., 2014). Observations of plume height with visual calibrated images and satellite data are also available in the 24/7 Operation Room (Scollo et al., 2019, Corradini et al., 2018) supporting the activities of Volcanologists 1 in drafting the reports and communications. Following the IAVW’s directives and the procedure of ENAC, the Civil Aviation National Authority of Italy,[2] Etna Volcano Observatory developed a semi-automatic system to edit in an easy way the VONA messages (paper in this special issue) which are automatically sent to a wide list of users belonging to both the aviation community and civil protection authorities. Moreover, when the 24/7 Operation Room sends the VONA message, receipt of the message needs to be confirmed by a call. The ACC changes are mainly based on the video-surveillance system, geophysical instrumental data and/or on the information given by the personnel in the field (usually Volcanologist 2). Green and Yellow ACC are issued in VONA messages when the volcano activity is normal or in a quiescent phase, respectively. Orange ACC is issued during any significant eruptive activity with no ash emission or when there is a weak ash emission and its dispersal remains within the P1 no-fly area (a circle centred on Etna summit having a radius of 1.0 NM). In the past, when a VONA with Orange ACC was issued during the long low-intensity eruptive phases of Mt. Etna, such as the summit lava flows, numerous requests for information were received from the pilots of the aircraft in transit in the Catania Control Traffic Region (CTR). In agreement with ENAC, the Orange ACC in a VONA is reiterated equal to the previous one each week, even if the previous one is still valid, or only with small variations. Therefore, it is ensured that air traffic controllers remain aware that an eruptive phenomenon that does not impact on air traffic, but can be a source of apprehension for a pilot in transit, is still ongoing. Finally, Red ACC is issued when there is a strong ash emission or a significant change of the eruptive style (Strombolian vs Lava Fountains). Afterwards, when a significant variation of the altitude of the eruption column is observed, another VONA from RED to RED is also issued. Table 3 summarises the procedure used to change the ACC at INGV-OE.
IMO
The Icelandic Meteorological Office (IMO) was officially designated as State Volcano Observatory in 2011 by the Icelandic Transport Authority (ITA) assigning the responsibility of reporting on volcanic unrest and volcanic eruptions to the London Volcanic Ash Advisory Center (VAAC) and other VAACs if necessary. This appointment was done in the aftermath of the volcanic eruption in Eyjafjallajökull in 2010 and as soon as the Grímsvötn eruption started in 2011. IMO has responsibility for monitoring, forecasting and warning of almost all natural hazards in Iceland, including volcanic unrest and eruptions (Fig.1 - pink area). The institute monitoring room consists of four experts on duty during the day (two natural hazard specialists and two meteorologists) which reduce to two during the night-time (Fig. 6). The natural hazard specialist (NHS) monitors the real time data coming in and integrates, in a multidisciplinary way, the information to assess any impending hazards. Contingency plans exist to guarantee fast communication with key stakeholders including the local Civil Protection, the London- VAAC and ISAVIA (the Icelandic navigation service provider). As part of the procedures, the aviation colour code is operated to inform the aviation sector about potential dangers associated with volcanic activity. The work in the monitoring room is supported by a group of scientists (seismologists, geophysicists, geochemists, volcanologists, hydrologists) who help with evaluating ongoing events, by processing monitoring data and interpreting them in light of background knowledge. In most situations, for example at the beginning of a volcanic unrest phase, this group is responsible for deciding on changes of the ACC, whereas, when it is needed to react quickly, a smaller group (or just the NHS) would take the decision.
Since its implementation in 2012, in the aftermath of the Eyjafjallajökull in 2010 and Grímsvötn in 2011 eruptions, the Aviation Colour Code has been used to report about the status of eight volcanoes, including Bárðarbunga (2014-2015), Eldey (2015), Katla (2016-2017), Öræfajökull (2017-2018), Reykjanes (2020 and 2022), Grímsvötn (2020, 2021 and 2022), Krýsuvík (2021 and 2022) and Askja (2021). A simple procedure has been set up to make the issuance of VONA fast and comprehensive. A template, pre-filled in some fields, is edited by the NHS with the additional information regarding the ongoing event. As such the VONA, broadcasting the change in ACC, is sent out via email to a list of addresses, the ACC is automatically changed on the online map on IMO’s website as well as in the Catalogue of Icelandic Volcanoes (https://icelandicvolcanoes.is//), and eventually the VONA is made available on the web.
The experience gained from operating the Aviation Colour Code at IMO suggests that a separate Volcano Alert Level system should be developed and implemented to inform other stakeholders and end users about ground-based hazards associated with the changed status of a volcano. The eruption in Bárðarbunga in 2014-2015 was an eye-opening event as the hazard posed to the aviation was irrelevant, but the hazards on the ground were highly time dependent and critical to assess the safety around the eruption site (Barsotti et al. 2020).
IPGP
Since the signing of an agreement between the Institut de Physique du Globe de Paris (IPGP) and civil aviation in 2015, by a national decree (https://www.legifrance.gouv.fr/eli/arrete/2014/3/27/DEVA1405407A/jo/texte) IPGP observatories are required to send a VONA for each change in the activity of the volcanoes for which they are responsible in overseas territories (La Réunion, Guadeloupe, Martinique) (Fig.1 - yellow areas). As of recently, steps are being taken to add the Mayotte volcanic zone (France) to this protocol. An official volcano crisis response plan (Dispositif spécifique ORSEC, organisation of civil security response) and protocols for volcano crises management (volcano unrest and eruption) are in place and operational, under the responsibility of the Préfecture (the local authority representing the state of France). Along with warnings to the local authority in charge of changing the alert level for the volcano, this protocol includes the issuance of a VONA as the duty with the highest priority duty for the local VO in case of unrest and/or eruption or return to baseline activity level. VONA are still not fully public, as the French IPGP office is working on creating a webpage to store and distribute the different types of reports published by their observatories.
IPGP-OVPF (Piton de la Fournaise - La Réunion)
As of November 2022, the Piton de la Fournaise volcano observatory (IPGP-OVPF), had issued 82 VONAs since October 2015 (date of implementation of the procedure), in response to 20 eruptions and 8 intrusion phases. The VONAs were sent to Toulouse VAAC, as well as London VAAC for redundancy, and Météo-France (the reference meteorological office). The general criteria to respond to the different phases of volcano activity in La Reunion are summarised below:
- Alert level 1 (imminent eruption): a VONA is issued with a yellow aviation colour code,
- Alert level 2 (ongoing eruption): a VONA is issued either with orange or red aviation colour code, depending on confirmation of ash production (since the procedure was implemented in 2015, only VONA with orange aviation colour code have been issued),
- Safeguard level (end of the eruption): a VONA is issued to go back to green colour code.
The decision of when to declare the beginning of an eruption at Piton de la Fournaise (Peltier and Di Muro, 2021) is taken with respect to the onset of eruptive tremor signals. As soon as the tremor stops the eruption is then declared over (Peltier et al. 2020). In that instance, parallel calls immediately follow to the Toulouse VAAC, and in La Réunion to the Air Traffic Control/Flight Information Centre (ACC/FIC), the Meteorological Watch Office (MWO), and to the local Civil Protection authorities.
IPGP-OVPF occasionally rehearses with the local Civil Protection. Two exercises have been held in the last 5 years dedicated to practice response to eruptions with direct impacts on inhabited areas. However, during such exercises VONAs were not sent out as the procedures are well established and tested several times each year given the frequency of eruptive activity at Piton de la Fournaise. The high rate of eruptions also allows IPGP-OVPF to maintain very regular interactions with the Toulouse VAAC and Météo-France.
IPGP-OVSG (Soufrière - Guadeloupe) and OVSM (Montagne Pelé - Martinique)
In the protocol of the ORSEC volcano emergency response, the Observatoire Volcanologique et Sismologique de Guadeloupe (OVSG-IPGP) and the Observatoire Volcanologique et Sismologique de Martinique (OVSMG-IPGP) are responsible for the provision of up-to-date information on volcanic activity and volcanic ash clouds at volcanoes in the French Caribbean. Information are delivered to the Piarco (Trinidad and Tobago) Air Traffic Control/Flight Information Centre (ATC/FIC), the Port of Spain (Trinidad and Tobago) Meteorological Watch Office, to the Washington DC (United States) VAAC and in parallel to the local Civil Protection authorities. During a crisis the responsibility is placed at the top of the call-down list. The general criteria to respond to the different phases of volcano activity within the ORSEC response plan in the French West Indies is reported in Table 4.
IPGP-OVSG and IPGP-OVSM occasionally rehearse with the local Civil Protection. IPGP-OVSG had exercises in 2019 and 2021 dedicated to practicing the response to eruption crises with direct impacts on inhabited areas. IPGP-OVSM had its first exercise on 7 December 2022 dedicated to practicing some elements of the response to an eruption crisis (e.g. escalating unrest, preventive evacuation of two test towns, small phreatic eruption during the evacuation) with direct impacts on inhabited areas. During the exercises VONAs were only sent locally to the Civil Protection authorities but not to the VAAC.
However, on 29 June 2021, a VONA protocol exercise was carried out for the two French volcano observatories (OVSG and OVSM) together with the Washington VAAC, the Piarco (Trinidad and Tobago) Air Traffic Control/Flight Information Centre (ACC/FIC), and the Port of Spain (Trinidad and Tobago) Meteorological Watch Office (MWO). As of 10 March 2023, real-crisis VONAs have not been issued for French Caribbean volcanoes (Soufrière of Guadeloupe, Montagne Pelée of Martinique).
IPGP-REVOSIMA (Mayotte active volcanic zone)
At the time of writing, there is no official volcano crisis response plan in place for the Mayotte active volcanic zone which is operationally monitored under the mandate of the Réseau de surveillance volcanologique et sismologique de Mayotte (REVOSIMA) by the IPGP-OVPF (La Réunion). The Préfecture authorities from Mayotte are currently in the process of developing this response plan for Mayotte. The VONA procedures will be similar to those for the other French volcanological observatories but at this time the precise structure of volcanic activity alerts for Mayotte have not been entirely formalised. However, temporary operational procedures are being followed by the REVOSIMA and the IPGP-OVPF. Analogous to Piton de La Fournaise, VONA procedures for Mayotte involve parallel calls to the local Civil Protection and Toulouse VAAC. Volcanic activity in Mayotte would also be immediately reported to authorities in La Réunion, such as the Air Traffic Control/Flight Information Centre, the Meteorological Watch Office, and to the local Civil Protection.
BGS
The British Geological Survey (BGS) provides objective and authoritative geoscientific data, information, and knowledge to help society manage environmental change and be resilient to environmental hazards. BGS is part of United Kingdom Research and Innovation (UKRI) and is a research centre under the Natural Environment Research Council (NERC). UKRI is a non-departmental public body sponsored by the Department for Science, Innovation and Technology (DSIT) and NERC is the driving force of investment in environmental science in the UK. The BGS works closely with the UK Met Office (London VAAC) and other UK scientific institutions as part of the ‘Natural Hazards Partnership’. The UK (England, Scotland, Wales and Northern Ireland) has no active volcanoes. Three populated British Overseas Territories (or UK Overseas Territories) have active volcanoes (Montserrat, Ascension Island and Tristan da Cunha). BGS is not a State Volcano Observatory for the British Overseas Territories but discussions about roles and responsibilities for the populated active volcanic islands of the South Atlantic are underway.
The combined territory of ‘St Helena, Ascension Island and Tristan da Cunha’ has a UK-appointed Governor who is the head of government, and Ascension Island and Tristan da Cunha each have an Administrator advised by elected Island Councils (Fig.1 - grey area). The last eruption of Tristan da Cunha was in 1961 (Baker et al. 1964). BGS has since prepared a preliminary hazard assessment for Tristan da Cunha (Dunkley 2002), responded to the offshore eruption of a seamount near Tristan da Cunha in 2004 by deploying campaign seismic instruments (e.g. O’Monghain et al., 2007), and interdisciplinary research has been completed on the eruption history, hazards and participatory approaches to disaster risk reduction (Hicks et al., 2012; 2014). BGS staff have organised citizen science initiatives and an ongoing study of landslides will include installation of a GNSS receiver (Hicks pers. comm.). There is no dedicated volcano monitoring network but BGS staff review data from two seismometers on the island installed by the Comprehensive Nuclear Test Ban Treaty Organisation (CTBTO) and there are plans for a dedicated seismic network. Recent research on Ascension Island has established an eruption history (e.g. Preece et al. 2018) and although there is further work to do, three basaltic eruptions are thought to have occurred in the last 2000 years, a geological map is also in progress (Vye Brown pers. comm.). BGS has developed preliminary scenario-based volcanic ash fall hazards assessments and carried out campaign monitoring (seismic and CO2 soil gas). There are plans for a dedicated seismic monitoring network.
BGS was involved in the multi-national, multi-institutional establishment and running of the Montserrat Volcano Observatory (MVO) from 1995-2008 (e.g. Aspinall et al. 2002), investing in training, capacity building and infrastructure. The Seismic Research Centre based at the University of the West Indies in Trinidad and Tobago leads the MVO team, under contract to the Government of Montserrat.
HSGME
Santorini Volcano Observatory is the only volcano observatory institution in Greece (Fig.1 - gold area). The Institute for the Study and Monitoring of the Santorini Volcano (I.S.M.O.SA.V.) is a non-profit organisation founded in the summer of 1995, whose primary aim is to continue to maintain the operation of the Santorini Volcano Observatory and the monitoring networks, which were established under a research program funded by the E.U (1993-1995). ISMOSAVs main target is the promotion of volcanological research on the island. More specifically how to achieve the most accurate assessment possible regarding volcanic phenomena, and to increase the ability to precisely forecast future volcanic eruptions. Santorini VO runs a complete monitoring system, which is crucial for the timely prediction of a possible volcanic eruption, and its scientific committee also undertakes the responsibility of disproving any false statements or rumours regarding the state of the volcano. The Santorini VO runs on a 24/7 base, with three telemetric, real time monitoring networks: seismic (9 stations), ground deformation (4 GNSS stations), and thermal-chemical (2 stations). Periodic monitoring measurements are also performed for thermal and chemical monitoring of the hot springs and fumaroles, CO2 flux and the Radon content in soil gasses. Ground deformation is also continuously evaluated with InSAR satellite images. Scientists responsible for these activities are permanent staff of the Hellenic Survey of Geology and Mineral Exploration, the Aristotle University of Thessaloniki, and other education and research institutions from Greece and abroad.
ISMOSAV is not an officially mandated institution to respond to volcanic crises. In Greece there is no such mandated institution. There is a National Committee of experts, under the Earthquake Planning and Protection Organization (EPPO) and the Civil Protection umbrella, which is responsible for evaluating the state of the active volcanic centres in Greece, defining the colour code of each volcano and advising the Civil Protection for any anomalous event, but the committee does not have any monitoring networks. ISMOSAV scientific committee members participate in the National Committee.
The volcano alert colour code in use for Greece has been defined in the Civil Protection “TALOS” plan, which concerns the emergency planning and the actions to undertake in case of a Santorini Volcano reactivation. In this plan, the 4-colour alert code scale proposed from IAVCEI has been accepted (green, yellow, orange, red). The only case that Santorini VO has been involved in a process of a Colour Code definition or change, was during the 2011-2012 Santorini volcano unrest, proposing in the National Committee to classify the Santorini volcano at a “yellow” colour code for this period. Santorini VO has never been involved in any process of providing a VONA or any other information for the VAACs, as no volcanic event has occurred at Santorini volcano since 1950 (Vougioukalakis, 2021).
KNMI
In 2010, the Caribbean islands of Saba and St. Eustatius became special municipalities of the Netherlands. Each island hosts an active volcano, Mount Scenery on Saba and The Quill on St. Eustatius (Fig.1 - cyan area). The Royal Netherlands Meteorological Institute (KNMI) is responsible for the timely warning for geophysical phenomena, including volcanic eruptions or unrest. KNMI is not a State Volcano Observatory. No eyewitness accounts exist of the historic eruptions of Mount Scenery and The Quill. However, volcanic deposits on both islands testify to their explosive past. The most recent eruption on Mount Scenery took place around 1640 and at The Quill around 400. Since 2006 KNMI has been building a multi-sensor monitoring network (de Zeeuw-van Dalfsen & Sleeman, 2018) on the islands. This work is carried out by a team consisting of a volcanologist, a seismologist and technical support. By the end of 2022 the monitoring network consists of 10 broadband seismometers, 8 continuous GNSS instruments and 2 temperature sensors. Seismic and GNSS data are transmitted to KNMI 24/7 using i) leased lines, ii) 4G mobile technology and iii) satellite communication. At KNMI the data are processed automatically and monitored by a 24/7 duty officer (Fig. 7).
In acute potentially hazardous situations, a protocol is followed: KNMI informs i) local authorities on the islands and ii) the departmental crisis coordination centre of the Ministry of Infrastructure and Water Management as soon as possible by phone and email. Responsible agencies on the islands can take further action if needed, assisted by the crisis coordination centre. In the case of volcanic unrest, activity reports will be issued to describe the recent changes. During periods of quietness, a status report is issued 1–2 times a year giving a general overview of the monitoring activities.
A four-tier system corresponding to Volcanic Alert Level and Aviation Colour Code is in place consisting of the following tiers: NORMAL – green, ADVISORY – yellow, WATCH – orange and WARNING – red. So far KNMI has never needed to change the ACC. A change in ACC would be based on the evaluation of available parameters such as seismic data, GNSS data, satellite observations, local observations and hot spring temperature measurements. A team from KNMI, led by the KNMI volcanologist, would make the decision to change the colour code if deemed necessary. Clear criteria for a change do not exist due to the fact that very little, to nothing, is known about the eruption behaviour of these volcanoes. The tasks of KNMI can be divided into data acquisition, data analysis and interpretation, and communication of findings to stakeholders. The communication line is in place for volcanic unrest but also functions for regional earthquake and tsunami warnings. A regional annual exercise, CARIBE WAVE is in place to validate and advance tsunami preparedness efforts in the Caribbean. During this yearly exercise the protocol is tested and updated when applicable. In 2019, during the EU exercise Caribbean Coast a volcanic eruption scenario was followed on Saba, including ACC changes.
University of Bergen
Beerenberg is the active volcano on the Norwegian island Jan Mayen that is situated about 600 km northwest of Iceland (Gjerløw, 2021) (Fig.1 - brown area). It is located along the Jan Mayen fracture zone that connects the Kolbeinsey and Mohns ridges and regularly produces large earthquakes (Rodríguez-Pérez and Ottemöller, 2014). Most recently, flank-eruptions occurred on Beerenberg in 1970 (Gjelsvik, 1970; Siggerud, 1970) and 1985 (Imsland, 1986; Havskov and Atakan, 1991) releasing clouds of steam and ash in both cases. Both eruptions were accompanied by earthquake activity, and for 1985 it was reported that earthquakes preceded the onset of eruption (Havskov and Atakan, 1991). The northern part of Jan Mayen is not visible from the settlement Olonkinbyen as Beerenberg is towering in between preventing early visual detection of an eruption. But shaking from frequent earthquakes felt at the settlement, if different from large earthquakes in the Jan Mayen fracture zone, is quite likely an indication of an eruption.
Jan Mayen has been seismically monitored in collaboration between the Norwegian Armed Forces and University of Bergen (UiB) since 1962. Initially, the monitoring was done with a single station that sadly missed the 1970 eruption as it was down due to maintenance. However, the eruption made it clear that seismic monitoring is required, and a three-station network became operational in 1972. This network recorded the 1985 eruption and remained in place today. Central recording equipment has changed several times, but a major upgrade of the seismic and data transmission equipment was only done in 2018 with infrastructure funding through the EPOS-Norway project. Today, the network has three high quality broadband seismometers and data is digitally transmitted to the base in Olonkinbyen. The data are received in real-time at UiB and processed as part of the Norwegian National Seismic Network (NNSN) operations (Ottemöller et al., 2018). GNSS receivers are installed at two of the sites and data are processed by the Norwegian Mapping Authority as daily chunks.
Near real-time monitoring of Beerenberg currently relies on the seismic data and the processing at UiB during working hours. However, the data are also available to the residents on Jan Mayen who can contact UiB staff at any time. Improvements to the monitoring system are possible by implementing automated warning and utilising the GNSS data. Satellite data are monitored by the Norwegian Meteorological Institute (MET Norway), which has the mandate to alert the Icelandic Meteorological Office in case of a suspected ash cloud caused by a Beerenberg eruption. IMO has the responsibility to issue Sigmet (SIGnificant METeorological information) message for the region including Jan Mayen Island (Titos et al. 2022).
Experiences in operating the Aviation Colour Code
The frequency of usage of the ACC and the accessibility to VONA messages varies significantly among VOs. Some already publish VONAs on their websites (see Table 2), whereas others are still working on making them easily accessible. When the number of VONAs issued by each VO is compared, a huge discrepancy appears to be evident. Figure 8 shows the number of times a decisional process has been undertaken for changing the ACC (both during increasing and decreasing activity trends) at each VO in the past five years. The figure shows the activations which required issuance of a VONA during real cases of unrest or volcanic eruption (in blue) as well as exercises (in red). INGV-OE and IPGP-OVPF are the VOs releasing the largest number of VONAs for real cases, due to the high frequency of volcanic eruptions at Mt. Etna (452) and Piton de la Fournaise (82), respectively. IMO issued a total of 39 VONAs, but for eight different Icelandic volcanoes. IMO also regularly rehearses on a monthly basis, resulting in a large number of VONAs issued for exercise purposes (52). CIVISA-IVAR has also been practising often, with 16 VONAs issued during exercises and IGN issued a total of 29 VONAs for real instances and 5 in one exercise. IPGP-OVSG practised over 3 exercises. Several VOs did not practise issuing VONAs very often in the past 5 years, neither for real cases, nor for exercises (HSGME and KNMI). University of Bergen never had the chance to practise the procedures for operating the ACC and issuing VONAs in recent years, the same applies to BGS.
In the following we report on three recent key events which raised some aspects to consider for a wider discussion, they are: 1) La Palma eruption in Canary Islands in 2021, 2) São Jorge seismo-volcanic unrest in the Azores in 2022, and 3) Fagradalsfjall eruption in Iceland in 2021.
La Palma eruption in 2021, Canary Islands (IGN)
During the La Palma volcanic event, 29 VONAs were issued, 7 of which involved a change in the aviation colour code (see Table 6). During that period the height of the eruptive column/ash cloud varied from 0 to 8500 m asl (being the height of the emission centre 1080 m asl at the beginning of the eruption, and the height when the new volcanic cone was fully developed about 1130 m asl). The first VONA issued during the event was on 16 September, 3 days before the start of the eruption, with ACC changing from green to yellow. On 19 September the eruption started, and the ACC changed from yellow to orange as the emission of ash was not very significant and no clear eruptive columns had developed. The first red ACC was issued on 23 September, when a sustained eruptive column of 5000 m asl height developed and with a high concentration of volcanic ash. Five days later, on 27 September, the magma emission stopped for about 7 hours (probably due to a collapse in the volcanic conduit), and the ACC was lowered to orange. The next day, with the magma emission restored, the explosive activity reached a maximum height at 7000 m asl, with a large amount of ash, so the ACC was raised to red again, and remained there until the end of the eruption during the night of 13 December. On 15 December the ACC was lowered to yellow due to 24 hours without ash emission. On 25 December, the eruption was declared officially over, and the ACC was finally lowered to green.
São Jorge seismo-volcanic unrest in 2022, Azores (CIVISA-IVAR)
The unrest episode at São Jorge started abruptly on 19 March 2022 at 16:05 (local time, UTC-1), with a sharp increase in seismic activity in the central part of the island, namely in the Manadas Fissure Volcanic System, where the historical eruptions of 1580 and 1808 took place. The seismic swarm quickly escalated on 20 March, leading CIVISA-IVAR to raise the scientific alert level from V0 (volcano in normal, quiet state) to V3 (signs of elevated activity, confirmation of reactivation of the system) in less than 12 hours. In the following days, seismic activity continued at very high levels and InSAR data confirmed ground deformation in the central part of the island compatible with a dyke intrusion at depth. This prompted CIVISA-IVAR to increase the alert level to V4 (signs of pre-eruptive activity, threat of a volcanic eruption) on 23 March, which was followed by the issuing of a VONA to change the ACC from green to yellow. Seismic activity continued at elevated levels during the following months, with low magnitude earthquakes (up to M3.8) extending for approximately 20 km along a WNW-ESE-trending strip, from the central part of the island (Norte Pequeno - Silveira area) to the western tip (Ponta dos Rosais). At the end of May and early June 2022, seismic activity showed a decreasing trend, although sometimes interrupted by short periods of higher hourly frequency and/or release of energy. The decrease in seismic activity, together with the absence of other anomalous indicators, related to ground deformation, gases or waters, led CIVISA-IVAR to lower the scientific alert level from V4 to V3 on 9 June. Accordingly a new VONA was issued changingthe ACC for São Jorge from yellow to green. Nearly ten months after the onset of the unrest, at the time of writing of this document, the seismic swarm was still ongoing. Until 12 January 2023, more than 56,000 earthquakes were recorded, of which at least 343 were felt by the population.
Fagradalsfjall eruption in 2021, Iceland (IMO)
A small effusive eruption commenced at Fagradalsfjall on the Reykjanes peninsula on 19 March 2021 and lasted for 6 months (Barsotti et al. 2023). The eruption was preceded by long precursors dated back to December 2019. However, it was not until 24 February 2021, when an earthquake of magnitude M5.7 struck in the unrest area, that the aviation colour code for the Krýsuvík volcanic system was elevated to yellow. After a few days, InSAR images and GNSS data revealed evidence of deformation caused by a likely magmatic intrusion in the area (Sigmunddson et al. 2022). The aviation colour code was elevated further to orange on 3 March when seismic tremor was detected at several stations on the peninsula, suggesting that magma was travelling at depth. On the evening of 19 March, the eruption started at Fagradalsfjall and the aviation colour code was changed to red. The red colour was maintained for eleven hours until a lack of ash was confirmed by a surveillance flight and monitoring observations, causing the aviation colour code to be moved back to orange. This level remained unchanged until 18 October, one month after the seismic tremor dropped and no fresh lava was detected at the crater. The eruption was eventually declared over in December 2021, however the aviation colour code remained yellow as the seismic activity and the deformation level in the peninsula never went back to normal conditions. The Krýsuvík volcanic system was moved back to ACC green (i.e. normal status) when there was confirmation of no further deformation occurring in the area for several months. As soon as the activity started escalating again in July 2022, the ACC was changed to yellow (30 July) and red when the eruption started again on 3 August. The ACC was moved back to orange after 1,5 hours when observations confirmed the lack of release of ash into the atmosphere.
[2] GEN 04A 19/12/2013 updated to GEN 04C 15/04/2020 (www.enac.gov.it/la-normativa/normativa-enac/circolari/serie-gen/gen-04b)