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Report on La Palma (Spain) — October 2021

Bulletin of the Global Volcanism Network, vol. 46, no. 10 (October 2021) Managing Editor: Edward Venzke. Edited by A. Elizabeth Crafford. La Palma (Spain) First eruption since 1971 starts on 19 September; lava fountains, ash plumes, and lava flows

Please cite this report as: Global Volcanism Program, 2021. Report on La Palma (Spain) (Crafford, A.E., and Venzke, E., eds.). Bulletin of the Global Volcanism Network , 46:10. Smithsonian Institution. https://doi.org/10.5479/si.GVP.BGVN202110-383010

28.57°N, 17.83°W; summit elev. 2426 m

All times are local (unless otherwise noted).

Multiple eruptions have occurred during the last 7,000 years at the Cumbre Vieja volcanic center on La Palma, the NW-most of the Canary Islands. The eruptions have created cinder cones and craters, and produced fissure-fed lava flows that reached the sea a number of times. Eruptions recorded since the 15th century have produced mild explosive activity and lava flows that damaged populated areas, most recently at the southern tip of the island in 1971. During the three-week eruption in October-November 1971, eruptive activity created a new cone, Teneguia, that had as many as six active vents (CSLP 90-71), and blocky lava flows that reached the sea on the SW flank.

A new eruption began at La Palma on 19 September 2021 in an area on the SW flank of the island about 20 km NW of the 1971 eruption, after a multi-year period of elevated seismicity. Two fissures opened and multiple vents produced lava fountains, ash plumes, and flows that traveled over 5 km W to the sea, destroying hundreds of properties in their path (figure 2). Activity through the end of September is covered in this report with information provided by Spain’s Instituto Geographico Nacional (IGN), the Instituto Volcanologico de Canarias (INVOLCAN), the Steering Committee of the Special Plan for Civil Protection and Attention to Emergencies due to Volcanic Risk (PEVOLCA), maps from Copernicus EMS, satellite data, and news and social media reports.

Precursor seismicity. In early July 2017 IGN enhanced their Volcanic Surveillance Network at La Palma to include four GPS antennas, five seismic stations, and four hydrochemical groundwater control points. A seismic swarm of 68 events located on the southern third of the island was recorded during 7-9 October 2017. It was the first of a series of seismic swarms recorded during 2017-2021 (table 1) located in the same general area. This first swarm was followed by a similar set of events a few days later during 13-14 October. The magnitudes of the events during October 2017 (given as MbLg, or the magnitude from the amplitude of the Lg phase, similar to the local Richter magnitude) ranged from less than 1.5 to 2.7, and they occurred over a depth range of 12-35 km. The next seismic swarm of similar characteristics occurred during February 2018, followed by a smaller swarm of seven microseismic events recorded in the same area one year later, on 12 February 2019.

Table 1. Precursor seismicity episodes at La Palma between October 2017 and late June 2021 were all located in the southern third of the island. Magnitude is reported by IGN as MbLg, or the magnitude from the amplitude of the Lg phase, similar to the local Richter magnitude. Data courtesy of IGN Noticias.

By the time the next seismic swarm began in July 2020, IGN had a network of 13 seismic stations installed around the island. There were 160 located events that occurred during 24 July-2 August 2020 with magnitudes of 1.2-2.5 and depths of 16-39 km. Reprocessing of the previous data indicated a distribution of seismicity for the three series (October 2017, February 2018, and July 2020) in a wide strip in an east-west direction, although the October 2017 series occurred at a shallower depth and with the epicenters more concentrated. IGN noted similarities between the February 2018 and July-August 2020 events in terms of location and magnitude (figure 3). Another very similar swarm of 602 detected events was recorded during 23-26 December 2020, with most events located on the western slope of Cumbre Vieja. Two swarms on 21 January and 25 June 2021 had fewer events but similar depths and magnitudes to the earlier events.

Renewed seismicity began on 11 September 2021. The number, frequency, and magnitude of the events all increased over the next several days, while the depth of the events grew shallower. On 13 September a multi-agency scientific committee raised the Alert Level to Yellow (the second lowest level on a four-color scale) for the municipalities of El Paso, Los Llanos de Aridane, Mazo, and Fuencaliente de la Palma. IGN noted a migration of the seismicity toward the W side of the island on 14 September (figure 4). The accumulated surface deformation between 12 and 14 September measured 1.5 cm from the island GNSS network. Seismic activity on 15 September continued to migrate slightly NW at depths of around 7-9 km; in addition, 20 shallow earthquakes of 1-3 km depth were recorded. The accumulated deformation had reached 6 cm by 15 September. As of 0930 on 16 September 50 shallow earthquakes between 1-5 km depth had been located and the maximum vertical deformation was around 10 cm in the area of the seismicity. During 16-18 September seismic activity decreased, but a 3.2 magnitude earthquake located at 100 m depth was felt by the local population. Intense surface seismicity (between 0-6 km) increased in the early hours of 19 September and numerous earthquakes were felt by the local population (figure 4). The maximum accumulated deformation increased to 15 cm in the area close to the seismicity by 1100 on 19 September, and the eruption began about five hours later.

Eruption begins 19 September 2021. A fissure eruption began at 1510 local time (1410 UTC) on 19 September after the intense seismic and deformation activity that began on 11 September. Observers near the eruption site in the area of Cabeza de Vaca, in the municipality of El Paso, witnessed a large explosion with ejecta that produced a gas-and-ash plume. Strombolian activity was accompanied by phreatomagmatic pulses along two 100-m-long N-S fissures about 200 m apart. INVOLCAN scientists observed seven vents along the fissures during the initial stage of the eruption (figure 5). Multiple tall lava fountains fed flows downslope to the W, igniting fires. The PEVOLCA steering committee briefly raised the Alert Level to Orange, and then to Red by 1700 for high-risk municipalities directly affected by the eruption. About 5,500 people evacuated with no injuries reported, and authorities recommended that residents stay at least 2 km from the vents. INVOLCAN scientists determined an average flow rate of 700 m/hour and lava temperatures of around 1,075°C at the start of the eruption (figure 6).

The Toulouse VAAC issued the first ash advisory for the La Palma eruption about 90 minutes after it began. They reported ongoing lava fountains and an ash plume to about 1 km altitude. The plume drifted SW at less than 1.5 km altitude, while SO 2 emissions were reported drifting ESE at 3 km altitude. Later that day, they noted continuing intense lava fountains and ashfall in the vicinity of the volcano. The next day ash emissions drifted S at 2.4 km altitude. Sulfur dioxide emissions were measured by satellite instruments beginning on 19 September; they increased dramatically and drifted hundreds of kilometers E and SE toward the NE coast of Africa over the next few days (figure 7). Ongoing ash emissions rose to 4.6 km altitude later on 20 September. The first Sentinel-2 satellite images of the eruption appeared on 20 September showing a strong point source thermal anomaly partly covered by meteoric clouds (figure 8).

The first map of the new flow on 20 September produced by IGN in partnership with Copernicus Emergency Management Service (EMS) showed that the main channel of the lava flow had traveled more than 3 km W. The flows had covered about 1 km 2 and destroyed an estimated 166 buildings (figure 9). A report of the PEVOLCA Scientific Committee indicated that activity on 20 and 21 September was concentrated at four main vents that produced parallel flows with an average flow rate of 200 m/hour; the maximum flow thickness was 10-12 m (figure 10). Strong lava fountaining continued both days and ash fell in the vicinity of the vents. By 0814 on 21 September an updated Copernicus EMS map showed that 350 homes had been covered by lava and the flow field had expanded to 1.54 km 2 . A few hundred more residents evacuated as lava advanced towards Tacande; bringing the number of evacuees to about 5,700. One lava flow branch was advancing slowly S at a rate of 2 m/hour. An ash cloud was observed later that day on the W flank of the volcano slowly drifting SW at 2.4 km altitude. Sulfur dioxide emissions were present over the SE part of the island and were visible at Gomera Island, 80 km SE. Late in the day, ash was observed in satellite imagery about 50 km W of the volcano, while intense lava fountaining continued at the source vent (figure 11).

Activity during 22-25 September 2021. Ash emissions during 22 and 23 September drifted SW and S from 0-3 km altitude, and NE and E from 3-5 km altitude (figure 12); ashfall up to 3 cm thick was reported downwind. An SO 2 plume was also noted drifting NE in satellite imagery. PEVOLCA reported on 23 September that two relatively slow-moving lava flows continued to advance downslope from the vent (figure 13). The northernmost flow was moving at 1 m/hour and was 12 m high and 500 m wide in some places. The southern flow, which surrounded Montaña Rajada, was moving at 4-5 m/hour and about 10 m high. The overall flow was 3.8 km long and 2.1 km from the coast (figure 14). By late on 23 September reports indicated 420 structures had been destroyed and the flow covered just under 2 km 2 .

Lava fountains rose hundreds of meters above the summit crater of the new cone early on 24 September 2021 (figure 15). IGN reported an increase in explosive activity on 24 September that was accompanied by a sharp increase in tremor amplitude. This was followed a short while later by the opening of two new vents on the NW flank of the cone; the fast-moving flows merged into one and produced a new flow over top of the earlier flows. Part of the upper section of the S flank of the cone collapsed on 24 September and briefly caused flow speeds to increase to 250-300 m/hour overnight before slowing to an average speed of 40 m/hour. Due to the fast-moving flow, an evacuation order was issued in the early afternoon for Tajuya, Tacande de Abajo, and part of Tacande de Arriba, affecting 300-400 people. Three airlines also suspended flights to La Palma. The Toulouse VAAC reported ash plumes throughout the day. Ash plumes drifted SW below 3 km altitude and E and SE at 3-5.2 km altitude and resulted in significant ashfall in numerous locations by the next morning (figure 16). Pilots also reported ash near Tenerife and over La Gomera.

By 25 September there were three active vents in the crater and one on the flank of the cone (figure 17), and two active lava flows. On 25 and 26 September dense ash emissions (figure 18) closed the airport and produced ashfall not only in the municipalities near the eruption, but also on the eastern slope of the island; it was reported in Villa de Mazo, Breña Alta and Breña Baja, and Santa Cruz de La Palma or Puntallana. Plumes were drifting SW at altitudes below 1.5 km and NE between 1.5 and 3.9 km altitude over a large area. Mapping by Copernicus EMS indicated that the ashfall covered an area of 13 km 2 (figure 19).

Activity during 26-28 September 2021. During the evening of 26 September jets of lava up to 1 km high were visible from La Laguna and some explosions were strong enough to be felt within 5 km of the vent (figure 20). The main, more northerly lava flow overtook the center of Todoque, in the municipality of Los llanos de Aridane, which had been evacuated several days earlier. It crossed the highway (LP-213) in the center of town and continued 150 m W. It was initially moving at about 100 m/hour, was 4-6 m high, and the front was about 600 m wide, but it slowed significantly after crossing through Todoque, and the height grew to 15 m; it was located about 1,600 m from the coast. The more southerly flow continued moving at about 30 m/hour and was about 2.5 km long.

The PEVOLCA Scientific Committee determined that the volume of erupted material from the beginning of the eruption on 19 September until 27 September was about 46.3 m 3 . By early on 27 September the front of the flow was close to the W side of Todoque Mountain (figure 21), and reports indicated that 589 buildings and 21 km of roads had been destroyed by the 2.5 km 2 of lava. A seismic swarm on the morning of 27 September was located at about 10 km depth in the same area of the previous seismicity below the vent. In addition, pulses of tremor coincided with pulses of ash emissions. A new flow appeared on the N flank of the cone during the afternoon and partly covered previous flows through the center of Todoque, reaching about 2 km from the coast (figure 22). Ash emissions were more intermittent on 27 and 28 September, drifting SW to 1.5 km altitude and NE to 4.3 km altitude in sporadic pulses associated with lava fountains.

The new flow moved through the upper outskirts of Todoque and had reached the road to El Pampillo on the border of the municipalities of Los Llanos and Tazacorte, about 1 km from the coast, early on 28 September (figure 23). A plume with moderate to high ash concentration rose to 5.2 km altitude and extended up to 25 km W. The altitude of the plume increased to 6.1 km drifting E later in the day. A significant SO 2 cloud was clearly identifiable in satellite imagery in a 75 km radius around the island. In addition, satellite instruments measured very large plumes of SO 2 drifting hundreds of kilometers E, S, and N over the next several days (figure 24).

Activity during 28-30 September 2021. Effusive activity continued with a sharp decrease in tremor during the day on 28 September. By evening, sustained fountaining was continuing at the N flank vent, while pulsating jets from three vents within the main crater produced strong effusion into both lava flows. The volume of the cone that had formed at the vent was estimated by PEVOLCA to be 10 million m 3 . Around 2300 local time on 28 September the main lava flow passed on the S side of Todoque Mountain and entered the sea in the area of Playa de Los Guirres in Tazacorte. A continuous cascading flow of lava fell over the cliff (figure 25) and began to form a lava delta. By dawn on 29 September the delta was growing out from the cliff, producing dense steam explosions where the lava entered the sea (figure 26).

By nightfall on 29 September vigorous Strombolian activity was continuing at the pyroclastic cone, and the main lava flow was active all the way to the sea, with a growing delta into the ocean. Ash emissions continued on 29 and 30 September, rising in pulses to 5.2 km altitude and drifting SE, changing to S, SW, and finally NW. Sentinel-2 satellite imagery comparing 25 and 30 September showed the growth of the lava flow during that interval (figure 27). Strombolian and flow activity continued at the fissure vent on 30 September with new surges of activity sending fresh pulses of lava over existing flows (figure 28). The ocean delta continued to grow and reached a thickness of 24 m by the end of 30 September. Mapping of the flow indicated that 870 buildings had been destroyed and the flow covered 3.5 km 2 by midday on 30 September (figure 29).

Late on 30 September 2021 two new vents emerged about 600 m NW of the base of the main cone. They created a new flow about 450 m away from, and parallel to, the main flow that crossed a local highway by the next morning and continued moving W (figure 30). Multiple vents also remained active within and on the flank of the main cone. As of 1 October, the front of the delta was 475 m out from the coastline and 30 m deep. IGN concluded that the volume of material erupted through the end of September was approximately 80 million m 3 .

Geological Summary. The 47-km-long wedge-shaped island of La Palma, the NW-most of the Canary Islands, is composed of two large volcanic centers. The older northern one is cut by the steep-walled Caldera Taburiente, one of several massive collapse scarps produced by edifice failure to the SW. On the south, the younger Cumbre Vieja volcano is one of the most active in the Canaries. The elongated volcano dates back to about 125,000 years ago and is oriented N-S. Eruptions during the past 7,000 years have formed abundant cinder cones and craters along the axis, producing fissure-fed lava flows that descend steeply to the sea. Eruptions recorded since the 15th century have produced mild explosive activity and lava flows that damaged populated areas. The southern tip of the island is mantled by a broad lava field emplaced during the 1677-1678 eruption. Lava flows also reached the sea in 1585, 1646, 1712, 1949, 1971, and 2021.

Information Contacts: Instituto Geographico Nacional (IGN) , C/ General Ibáñez de Íbero 3, 28003 Madrid – España, (URL: https://www.ign.es/web/ign/portal, https://www.ign.es/web/resources/volcanologia/html/CA_noticias.html); Instituto Volcanologico de Canarias (INVOLCAN) (URL: https://www.involcan.org/, https://www.facebook.com/INVOLCAN, Twitter: INVOLCAN, @involcan); Steering Committee of the Special Plan for Civil Protection and Attention to Emergencies due to Volcanic Risk (PEVOLCA) , (URL: https://www3.gobiernodecanarias.org/noticias/los-planes-de-evacuacion-del-pevolca-evitan-danos-personales-en-la-erupcion-volcanica-de-la-palma/); NASA Global Sulfur Dioxide Monitoring Page , Atmospheric Chemistry and Dynamics Laboratory, NASA Goddard Space Flight Center (NASA/GSFC), 8800 Greenbelt Road, Goddard, Maryland, USA (URL: https://so2.gsfc.nasa.gov/); Copernicus EMS (URL: https://emergency.copernicus.eu/, https://twitter.com/CopernicusEMS ); Sentinel Hub Playground (URL: https://www.sentinel-hub.com/explore/sentinel-playground); Cabildo La Palma (URL: https://www.cabildodelapalma.es/es/algunas-de-las-imagenes-de-la-erupcion-volcanica-en-la-palma); El Periodico de Cataluny, S.L.U. (URL: https://www.elperiodico.com/es/fotos/sociedad/erupcion-palma-imagenes-12093812/12103264). Corporación de Radio y Televisión Española (RTVE) (URL: https://rtve.es, https://img2.rtve.es/imagenes/casas-todoque-alcanzadas-lava-este-miercoles-22-septiembre/1632308929494.jpg); Tom Pfeiffer , Volcano Discovery (URL: http://www.volcanodiscovery.com/); Volcanes de Canarias (URL:https://twitter.com/VolcansCanarias/status/1441711738983002114); Agence France-Presse (AFP) (URL: http://www.afp.com/ ); Bristol Flight Lab , University of Bristol, England (URL: www.https://flight-lab.bristol.ac.uk, https://twitter.com/UOBFlightLab).

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When Kilauea Erupted, a New Volcanic Playbook Was Written

Scientists learned lessons from the 2018 outburst on the island of Hawaii that are changing how responders prepare for eruptions in other places.

By Robin George Andrews

Back in the summer of 2018, Wendy Stovall stood and stared into the heart of an inferno.

Hawaii’s Kilauea volcano had been continuously erupting in one form or another since 1983. But from May to August, the volcano produced its magnum opus , unleashing 320,000 Olympic-size swimming pools’ worth of molten rock from its eastern flank.

Dr. Stovall, the deputy scientist-in-charge at the U.S. Geological Survey’s Yellowstone Volcano Observatory , recalls moments of being awe-struck by the eruption’s incandescence: lava fountains roaring like jet engines, painting the inky blue sky in crimson hues. But these briefly exhilarating moments were overwhelmed by sadness. The people of Hawaii would suffer hundreds of millions of dollars in economic damage. The lava bulldozed around 700 homes. Thousands of lives were upended. Even the headquarters of the Hawaiian Volcano Observatory itself, sitting atop the volcano , was torn apart by earthquakes early in the crisis.

Like many volcanologists who were there during the eruption, Dr. Stovall is still processing the trauma she witnessed. Sadness is not quite the right word to describe what she feels, she said: “Maybe it’s an emotion that I don’t even have a word for.”

But not only trauma has resulted from the crisis: It has also produced something of a sea change in the way scientists and their emergency services partners are able to respond to volcanic emergencies.

During Kilauea’s devastating outburst, responders found novel ways to deploy drones and used social media to help those in the lava’s path. They also achieved more ineffable insights into how to keep cool in the face of hot lava. And this pandemonium of pedagogical experiences will prove valuable in times to come. The United States is home to 161 active or potentially active volcanoes — approximately 10 percent of the world’s total. When — not if — a Kilauean-esque outburst or something more explosive takes place near an American city, scientists and emergency responders will be better prepared than ever to confront and counter that volcanic conflagration.

A Patchwork of Fire

In volcano preparedness, knowing where the next socially disruptive eruption may take place is half the battle.

Not all of America’s active volcanoes are equally hazardous. Many in Alaska are situated on extremely remote islands . The Yellowstone supervolcano may sound frightening, but this cauldron does not deserve to be a boogeyman. “The odds of a supereruption happening are infinitesimally small,” said Emilie Hooft , a geophysicist at the University of Oregon.

California is home to at least seven potentially active volcanoes. Although they are “mostly where the people aren’t, a lot of California’s infrastructure crosses these volcanic zones,” said Andy Calvert , the scientist-in-charge at the Geological Survey’s California Volcano Observatory. An eruption at any of them could destroy power lines, highways, waterways and natural gas pipelines.

The volcanoes of the Pacific Northwest are not dissimilar to bombs lingering in the background of populous American ports, towns and cities. Some, like Mount St. Helens , are infamous for giant explosions and superheated, superfast exhalations of noxious gas and volcanic debris.

Others, like Washington State’s Mount Rainier, are more insidious. The volcano is known for making concrete-like slurries called lahars , in which freshly erupted ash mixes with snow or rainwater and gushes downslope, consuming everything in its path. These lahars “are a huge and real hazard,” Dr. Hooft said. Populous settlements within or at the terminus of the volcano’s many valleys, including parts of the Seattle-Tacoma metropolis, are built on ancient lahar deposits — and as the geologist’s refrain goes, the past is the key to the present.

Another major concern is America’s poorly understood volcanic fields: sprawling collections of cones, craters and fissures nestled between countless towns stretching from California to Washington State. Except for Mount St. Helens, said Dr. Stovall, “it is statistically more likely that an eruption will occur from any one of these volcanic fields than from one of the charismatic stratocones of the Cascades.”

While constantly watching Kilauea , the eyes of the Hawaiian Volcano Observatory also remain fixed on Mauna Loa, Kilauea’s colossal neighbor.

It has not erupted since 1984 — a disquietingly long pause. But in recent years, Mauna Loa has been grumbling. Several of this titan’s lava flows have come agonizingly close to obliterating the city of Hilo in the past century, and although they have serendipitously stopped short , they may one day succeed.

When Ken Hon , the scientist-in-charge at the Hawaiian Volcano Observatory, was asked if a future Mauna Loa eruption concerned him, he replied with a question of his own.

“Are you wary of a tiger when it’s sleeping?” he said. “It’s a sleeping tiger in your yard, and there’s no cage, and you’re just kind of watching it.”

A Kilauean Education

Fortunately, the lessons learned from the 2018 eruption have strengthened the armor of America’s volcanic vanguard.

Kilauea took not just the Hawaiian Volcano Observatory but the entire U.S. Geological Survey to school. During the 2018 crisis, staff from the Alaska, California, Cascades and Yellowstone observatories headed to Hawaii to assist, like white blood cells from throughout the body rushing to the site of a pathogen’s incursion. Despite some parts of America not seeing an eruption for over a century, this across-the-spectrum response allowed scientists from the Geological Survey to “keep the tools sharp,” Dr. Calvert said.

Hawaii’s lava factories are now better understood. They may sometimes be the deliverers of destructive horrors, but “volcanic eruptions are this amazing opportunity for scientists to do basic research,” said Ken Rubin , a volcanologist at the University of Hawaii at Manoa. The eruption in 2018, revealed that “there’s a lot of ways this volcano can operate,” he said.

Some key observations made during the 2018 crisis are likely to apply to countless other volcanoes, including those enigmatic volcanic fields on the West Coast. For instance, Kilauea stopped erupting despite retaining most of its magma . A change in the rhythm of its seismic soundtrack also revealed changes in the magma’s gloopiness , a key factor in an eruption’s explosive capacity. Monitoring such changes may help forecast how future eruptions will evolve, and how long they will continue once they start.

Kilauea’s outburst also changed the way scientists communicate with the public.

“It was the first big eruption we’ve had in the social media age,” said Tina Neal , director of the Geological Survey’s Volcano Science Center. During the eruption, her colleagues provided a constant stream of updates on Facebook and Twitter, debunking misconceptions and rumors. This proved to be one of the most effective ways of providing lifesaving advice to those fleeing the eruption.

“I’ll admit that I was skeptical of spending too much time delivering information via social media,” said Ms. Neal, who was the Hawaiian Volcano Observatory’s scientist-in-charge during the 2018 eruption. She was concerned that in doing so she would mainly be catering to curious but unaffected parties further afield.

But she said she was happy to be proved wrong — and added that she thinks the Geological Survey’s volcanologists now have an effective social media operation that can spring into action whenever a volcano starts twitching.

Drones and Tweets

The 2018 crisis also kick-started a nationwide technological revolution. It had long seemed strange to Angie Diefenbach , a geologist at the Cascades Volcano Observatory, that management did not appear to see the value of using drones to study erupting volcanoes in the United States, particularly as academics both inside and outside the country had been doing just that for several years.

Kilauea’s dramatic eruption was a paradigm-shifting moment. Ms. Diefenbach, who was already equipped with a pilot’s license, was sent to the effervescing volcano with a handful of keen colleagues and a small fleet of flying robots.

The pilots had a steep learning curve. The drones frequently flitted over the incandescent fury emerging from fissure eight, one of the two dozen cracks in the volcano’s flank, to film the seemingly endless flow of lava and sniff the chasm’s noxious gases.

“That fissure eight plume was intense, and the river of lava was extremely hot,” Ms. Diefenbach said. Every now and then, an upswell of heat would knock the levitating robots skyward by a couple hundred feet, threatening a loss of control that might plunge them into molten rock. Fortunately, they all survived to fly another day.

Immediately, she said, the powers that be recognized that drones “really add a fundamental piece to the story” for volcano monitoring. Bird’s-eye views of lava flows allowed scientists to study the evolution of the eruption in real time. And communities in the path of the lava could be given advance warning; at one point, a man trapped in his home at night and surrounded by lava was led by a drone through the maze of molten rock to safety.

Ms. Diefenbach, who works with uncrewed aircraft systems like drones for the Volcano Science Center, is now training more drone pilots across all five volcano observatories. While awaiting the next socially disruptive eruption, some of her drones are being used to study volcanoes that could one day reawaken, including inaccessible snowcapped peaks in Alaska.

Meandering Paths Forward

This is not to say that the scientists of the U.S. Geological Survey have been “twiddling their thumbs waiting” for a ruinous eruption like Kilauea, Ms. Neal said.

The agency’s staff are working constantly with their academic partners to improve their understanding of America’s fiery mountains. They are also continually learning from the way other countries respond to their own volcanic crises . The scientists regularly team up with emergency managers to conduct drills, including the annual evacuation exercises near Mount Rainier.

But the path to volcanic enlightenment is not a straight line. Although all of America’s active volcanoes are monitored, some considered to be high risk are not adorned with sufficient sensors. This can be a result of budgetary constraints, the difficulty of instrumenting treacherous volcanoes and, in some cases, red tape preventing the placement of sensors in wilderness areas.

“There are some volcanoes where we’re more at the starting line,” said Seth Moran , a seismologist at the Cascades Volcano Observatory, citing Washington’s Glacier Peak and Mount Baker .

Climate change and California’s increasingly intense wildfires are also aggravating the situation. A newly installed ground deformation sensor on Mount Shasta, for example, was taken out by this summer’s furious Lava fire , Dr. Calvert said.

Despite these setbacks, the Geological Survey continues to strengthen its monitoring efforts, with its network of instruments on several particularly hazardous volcanoes being upgraded and expanded . It also participates in tabletop exercises to test everyone’s mettle. One that took place over several days last November pitted scientists against a hypothetical eruption of Oregon’s Mount Hood.

Like the Kilauean eruption, this virtual volcanic gauntlet served up an underappreciated reminder: The people responding to volcanic crises may have extraordinary skill sets, but they are not superhuman.

“The general feeling afterwards was just of overwhelming exhaustion,” said Diana Roman , a geophysicist at the Carnegie Institution for Science and one of those who ran the exercise. “And that was part of the point.”

When it comes to America’s readiness for the next eruption, preparing scientists psychologically for the reality of a prolonged volcanic crisis is a necessity.

In 2004, when Mount St. Helens began to cough and splutter in a concerning manner, Dr. Moran became wrapped up in a surfeit of tasks. “It was about week three when my wife brought our kids to say good night to me,” he said. “That was my indication that I was probably doing too much. I should at least be able to get home and say good night to my kids.”

These experiences have taught Dr. Moran and his colleagues an invaluable lesson: “You can’t have people getting burned out right off the bat,” he said. Giving individuals clear roles ahead of time, and making their teams small and manageable, will hopefully prevent this sort of exhaustion in the future.

Though it’s not only scientists who can get drained during lengthy volcanic eruptions. As the weariness over the pandemic is grimly demonstrating , “it’s hard to keep people’s attention on something for a long time,” said Brian Terbush , the program coordinator for earthquakes and volcanoes at Washington State’s Emergency Management Division. “They get really tired of it. I’m tired of it.”

And protecting the public is considerably more difficult if people are not paying attention.

Fires of the Future

The location, timing and effects of America’s next volcanic disaster remain unknown. Even after a significant eruption begins, forecasting its evolution will be difficult.

“Even on the world’s best instrumented volcano,” said Dr. Hon, referring to Kilauea, “we still don’t really understand it that well.”

And yet, despite having so many dangers and complications to contend with, no one died and thousands of lives were saved during the 2018 crisis.

Those who were involved in the Kilauea response hope that the public will remember the role geoscientists played during the next volcanic emergency and see them as trustworthy protectors.

Not everyone will. “We often get told that we’re lying, and we’re hiding things, because we’re the government,” said Dr. Stovall — an uncomfortable echo of the similarly unfounded charges of conspiracy that many have directed toward public health professionals during the pandemic.

But the volcanologists and their peers say they will remain unwavering in their mission to decipher the country’s beguiling but occasionally menacing volcanoes.

“We are doing our best,” Dr. Stovall said. “And we’re in it for the greater good.”

La Palma Eruption 2021

Date: Sept. 19, 2021 Type:    Volcanoes Region :  Africa , Canary Islands Info & Resources: 

• View maps & data products for the La Palma eruption on the NASA Disasters Mapping Portal
• NASA Disasters program resources for volcanoes
• Latest updates from the Instituto Geologico y Minero de Espana (IGME)
• Latest updates from the Smithsonian Global Volcanism Program
• Latest updates from the Instituto Volcanológico de Canarias (INVOLCAN)
• Educational story map of La Palma data products & visualizations, developed by Esri

UPDATE Oct. 13, 2021

View fullscreen on the NASA Disasters Mapping Portal

Researchers working with the NASA ROSES A.37 project “ Day-Night Monitoring of Volcanic SO2 and Ash for Aviation Avoidance at Northern Polar Latitudes ” developed this animation of sulfur dioxide (SO2) clouds from the La Palma eruption using satellite data from NASA / NOAA Suomi-NPP and NOAA-20 Ozone Mapping and Profiler Suite (OMPS) spectrometers. Both satellites fly similar near-polar orbits, but are about 50 minutes apart. NOAA-20 OMPS measures with higher ground resolution. Using two satellites allows researchers to make more frequent, precise observations to identify hazardous densities of volcanic gases and aerosols.  

The above animation shows SO2 column density in Dobson Units (1 DU = 2.69 x 1016 SO2 molecules /cm2) from Sept. 19 – 30, 2021. S02 is used to indicate the presence of volcanic gases and also as a proxy for volcanic aerosols (sulfuric acid or vog and ash), which can negatively affect air quality for people living in the region, as well as potentially damage aircraft flying through the volcanic clouds. Credits: NASA  

Update Oct. 4, 2021

On Sept. 19, 2021, the Cumbre Vieja volcano on the island of La Palma in the Canary Islands started erupting after remaining dormant for 50 years. Since the initial eruption, the volcano has seen several Strombolian explosions , significant emissions of ash and gas, and multiple vents spewing molten lava down the mountain and into surrounding regions. According to the latest media reports over 800 buildings have been destroyed and about 6,000 people evacuated from the area.

The NASA Earth Applied Sciences Disasters program area has activated efforts to monitor the eruption and provide Earth-observing data and analysis in support of risk reduction and recovery for the eruption. The program is in contact with colleagues from the Instituto Geologico y Minero de Espana ( IGME ) and the Institut de Physique du Globe de Paris ( IPGP ) to share knowledge and data for situational awareness. 

These efforts are being supported by the NASA ROSES A.37 research projects “ Day-Night Monitoring of Volcanic SO2 and Ash for Aviation Avoidance at Northern Polar Latitudes ” and “ Global Rapid Damage Mapping System with Spaceborne SAR Data .”

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An ash plume rises from the active volcano on Whakaari/White Island in New Zealand on December 9, 2019.

Why the New Zealand volcano eruption caught the world by surprise

The explosive event was “the actual worst-case scenario,” geologists report.

On Monday, at 2:11 p.m. local time, an explosive eruption rocked White Island, a small volcanic isle in New Zealand’s Bay of Plenty. A series of violent blasts rang out, flinging ash 12,000 feet into the sky and showering the volcano’s floor with hot debris, before everything fell silent a handful of minutes later.

It quickly became apparent that lives were lost. A number of tourists were on the island at the time, several of whom were right next to the volcano ’s active vent. At the time of writing, five deaths have been officially recorded, with several more people still unaccounted for. Recent reconnaissance flights over the island, also known by its Māori name Whakaari, have found no signs of life .

For this sort of volcanic paroxysm, “this was probably the actual worst-case scenario,” says Shane Cronin , a volcanologist and Earth scientist at the University of Auckland.

Understandably, this explosion took many by surprise. But for this volcano, and for the type of eruption style involved, it was nothing out of the ordinary: Similar eruptions, though not everyday occurrences, have happened at many volcanoes all over the world, and they will continue to appear without much warning. ( Find out the most dangerous volcanoes in the U.S., according to geologists .)

“This is a case of people being in the wrong place at the wrong time,” Janine Krippner , a volcanologist at the Smithsonian Institution’s Global Volcanism Program. “It’s horrible when it happens, but it will continue to happen over and over again.”

So why was the eruption at Whakaari/White Island so unpredictable and deadly? Let’s look at the facts.

For Hungry Minds

Invisible warning signs.

Whakaari/White Island is the summit of a complex submarine volcano. According to the Smithsonian Institution’s Global Volcanism Program , it is highly ebullient, engaging in a variety of eruption styles. Many feature moderate explosions.

As a result of its hyperactivity, and the frequency with which tourists visit, Whakaari/White Island is heavily monitored. Scientists were keeping a close eye on it to try and spot any behaviors that could potentially indicate the volcano was gearing up for something explosive.

Volcanologists with GNS Science, a New Zealand-based consulting group, spotted some localized surface deformation a few weeks earlier, says Geoff Kilgour , a scientist with the group. Deformation can be indicative of subsurface pressure changes caused by moving superheated liquids, gases, or magma. But in this case, the activity didn’t indicate that any major build-up of pressure was happening.

Still, monitoring efforts and reports from tourist companies also picked up some geyser-like convulsions at the time, along with an uptick in gas emissions and seismic rumblings. So, authorities did raise the volcano’s alert level. Alert level rises don’t mean that an eruption is inevitable, and in many cases, no eruption is forthcoming. Unfortunately, this time was a deadly exception.

Volcanic pressure cooker

Magma happens to sit close to the surface at Whakaari/White Island, and the molten rock constantly degases and heats up the plentiful supply of groundwater.

“You’ve got a really complex witches’ brew there,” Cronin says.

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In addition, the magma’s path to the surface at this vent can get blocked, sometimes through the precipitation of minerals. That can lead to gases getting trapped underneath, where they keep accumulating and getting heated, creating a pocket of superheated elements somewhat like a pressure cooker. The sizzling water is often trying to boil off into steam, but it remains a liquid because of the immense pressure.

That means any crack in this geologic pressure cooker can produce a savage, speedy decompression event. The liquid water flashes to steam, expanding its volume 1,700 times in a heartbeat. The expansion energy is enough to shatter rocks and carve out geologic scars. When the pressure at the vent is released, a decompression wave rockets down into the volcano’s throat, where it encounters more pressurized water. Sometimes, the shockwave hits the magma, turning what is a steam-based outburst into a magma-driven eruption.

Even a steam blast is lethal if you stand too close to the vent, Cronin says. But the flying rocks, wet debris jets, and scorching air can also cause life-threatening harm.

And the cascade of events happens so fast that no one has time to react. The bulk of this eruption was a collection of impulsive bursts, each just tens of seconds long. The whole thing was pretty much over in two minutes, Kilgour says. The situation is especially dangerous on Whakaari/White Island, since the volcanic island is so small.

“There aren’t a lot of places you can be on White Island without being very close to the vent,” says Loÿc Vanderkluysen , a volcanologist at Drexel University.

Uncertain future

This eruption style—driven at least initially by steam—occurs at volcanoes all over the world. A somewhat similar steam blast happened at Japan’s Mount Ontake in 2014, killing 63 hikers . Crucially, these volcanic events don’t provide any definitive warning signs. No matter where in the world they occur, “no one has shown that they are able to forecast this kind of activity,” Kilgour says.

In this case, bad luck played a role, too. A similarly vicious eruption took place at Whakaari/White Island in 2016, but it happened at night. This one happened in the afternoon, while tourists were present. ( Here’s why people continue to live near active volcanoes .)

It’s unclear how this tragedy will affect the ability of tourists to visit this privately owned island in the long run. Scientists will continue to monitor and study the island closely, and Cronin and his colleagues are creating miniature hydrothermal explosions in a lab to try and better understand what causes them.

For now, though, there is much that remains unknown about these volcanic blasts, and it’s all the more important for everyone to understand the dangers and uncertainties involved in visiting an active volcano like Whakaari/White Island.

“It’s hard to portray uncertainty to tourists,” Kilgour says. “And there’s a lot of uncertainty about volcanic eruptions, especially these rapid-onset, or essentially unpredictable, events.”

What is grimly certain is that these types of volcanic explosions will continue to pose potentially deadly risks. “Of all the volcanoes that I’ve visited that are easily accessible to tourists,” Vanderkluysen says, “I don’t think there were any where I heard absolutely zero horror stories.”

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Volcano case study - Mount Etna (2002-2003), Italy

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Can you describe the location of Mount Etna? Could you draw a sketch map to locate Mount Etna?

Case study task

Use the resources and links that can be found on this page to produce a detailed case study of the 2002-2003 eruption of Mount Etna. You should use the 'Five W's" subheadings to give your case study structure.

What happened?

The Guardian - Sicilian city blanketed in ash [28 October 2002]

When did it happen?

Immediately before midnight on 26 October 2002 (local time=GMT+1), a new flank eruption began on Mount Etna. The eruption ended after three months and two days, on 28 January 2003.

Where did it happen?

The eruption occurred from fissures on two sides of the volcano: at about 2750 m on the southern flank and at elevations between 2500 and 1850 m on the northeastern flank.

Why did it happen?

Mount Etna is a volcano. The reasons why Mount Etna is located where it is are complex. Here are some of the theories:

• One theory envisages a hot spot or mantle-plume origin for this volcano, like those that produce the volcanoes in Hawaii.
• Another theory involves the subduction of the African plate under the Eurasian plate.
• Another group of scientists believes that rifting along the eastern coast of Sicily allows the uprise of magma.

Who was affected by it happening?

• The Italian Government declared a state of emergency in parts of Sicily, after a series of earthquakes accompanying the eruption of forced about 1,000 people flee their homes.
• A ship equipped with a medical clinic aboard was positioned off Catania - to the south of the volcano - to be ready in case of emergency.
• Emergency workers dug channels in the earth in an attempt to divert the northern flow away from the town of Linguaglossa.
• Schools in the town have been shut down, although the church has remained open for people to pray.
• Villagers also continued their tradition of parading their patron saint through the streets to the railway station, to try to ward off the lava flow.
• Civil protection officials in Catania, Sicily's second-biggest city, which sits in the shadow of Etna, surveyed the mountain by helicopter and were ready to send water-carrying planes into the skies to fight the fires.
• The tourist complex and skiing areas of Piano Provenzana were nearly completely devastated by the lava flows that issued from the NE Rift vents on the first day of the eruption.
• Heavy tephra falls caused by the activity on the southern flank occurred mostly in areas to the south of the volcano and nearly paralyzed public life in Catania and nearby towns.
• For more than two weeks the International Airport of Catania, Fontanarossa, had to be closed due to ash on the runways.
• Strong seismicity and ground deformation accompanied the eruption; a particularly strong shock (magnitude 4.4) on 29 October destroyed and damaged numerous buildings on the lower southeastern flank, in the area of Santa Venerina.
• Lava flows from the southern flank vents seriously threatened the tourist facilities around the Rifugio Sapienza between 23 and 25 November, and a few days later destroyed a section of forest on the southwestern flank.
• The eruption brought a heightened awareness of volcanic and seismic hazards to the Sicilian public, especially because it occurred only one year and three months after the previous eruption that was strongly featured in the information media.

Look at this video clip from an eruption on Mount Etna in November 2007.  What sort of eruption is it?

There is no commentary on the video - could you add your own explaining what is happening and why?

You should be able to use the knowledge and understanding you have gained about 2002-2003 eruption of Mount Etna to answer the following exam-style question:

In many parts of the world, the natural environment presents hazards to people. Choose an example of one of the following: a volcanic eruption, an earthquake, or a drought. For a named area, describe the causes of the example which you have chosen and its impacts on the people living there. [7 marks]

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• Open access
• Published: 15 July 2022

Responding to eruptive transitions during the 2020–2021 eruption of La Soufrière volcano, St. Vincent

• E. P. Joseph   ORCID: orcid.org/0000-0002-4836-8715 1 ,
• M. Camejo-Harry   ORCID: orcid.org/0000-0001-5979-7497 1 , 2 ,
• T. Christopher 1 , 3 ,
• R. Contreras-Arratia   ORCID: orcid.org/0000-0003-2713-5397 1 ,
• S. Edwards   ORCID: orcid.org/0000-0001-7536-4480 1 ,
• O. Graham   ORCID: orcid.org/0000-0002-9468-927X 1 ,
• M. Johnson 1 ,
• A. Juman 1 ,
• J. L. Latchman 1 ,
• L. Lynch 1 ,
• V. L. Miller   ORCID: orcid.org/0000-0003-1962-9223 1 , 3 ,
• I. Papadopoulos   ORCID: orcid.org/0000-0003-2923-3070 1 ,
• K. Pascal 1 , 3 ,
• R. Robertson   ORCID: orcid.org/0000-0001-5245-2787 1 ,
• G. A. Ryan   ORCID: orcid.org/0000-0002-9469-0107 1 , 3 ,
• A. Stinton 1 , 3 ,
• R. Grandin 4 ,
• I. Hamling   ORCID: orcid.org/0000-0003-4324-274X 5 ,
• M-J. Jo 6 ,
• J. Barclay   ORCID: orcid.org/0000-0002-6122-197X 7 ,
• P. Cole   ORCID: orcid.org/0000-0002-2964-311X 8 ,
• B. V. Davies   ORCID: orcid.org/0000-0001-5771-2488 7 &
• R. S. J. Sparks 9  

Nature Communications volume  13 , Article number:  4129 ( 2022 ) Cite this article

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A critical challenge during volcanic emergencies is responding to rapid changes in eruptive behaviour. Actionable advice, essential in times of rising uncertainty, demands the rapid synthesis and communication of multiple datasets with prognoses. The 2020–2021 eruption of La Soufrière volcano exemplifies these challenges: a series of explosions from 9–22 April 2021 was preceded by three months of effusive activity, which commenced with a remarkably low level of detected unrest. Here we show how the development of an evolving conceptual model, and the expression of uncertainties via both elicitation and scenarios associated with this model, were key to anticipating this transition. This not only required input from multiple monitoring datasets but contextualisation via state-of-the-art hazard assessments, and evidence-based knowledge of critical decision-making timescales and community needs. In addition, we share strategies employed as a consequence of constraints on recognising and responding to eruptive transitions in a resource-constrained setting, which may guide similarly challenged volcano observatories worldwide.

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Introduction.

A major goal of volcanology is to forecast changes in the behaviour of volcanoes, particularly the onset and conclusion of eruptions and behavioural transitions, such as between explosive and effusive activity 1 , 2 , 3 . Transitions pose challenges for decision-makers in the management of ongoing volcanic crises; >75% of recent fatalities are associated with changing eruptive behaviour, where all or some individuals were inside declared hazard zones at that point 4 . The 2020–2021 La Soufrière volcanic eruption in St. Vincent, illustrates these challenges.

Crisis science is defined as conducting scientific research during a crisis, which involves data acquisition, analysis, interpretation and archiving of scientific and technical resources, as well as organising logistics, staffing and communicating findings with stakeholders and the public 5 . Volcanic crises include unrest, eruption and any aftermath. The core goal of observatory staff during crises is to acquire, analyse interpret and communicate data in a way that assists local populations and civil protection agencies with their decision-making 6 .

La Soufrière volcano (13.33°N; 61.18°W), located in northern St. Vincent, is a 1220 m high stratovolcano with a summit crater ~1.6 km in diameter and 300–600 m deep 7 . Historical eruptions of basaltic-andesitic magmas typically last many months 8 , 9 and occur in both the absence and presence of a crater lake. Eruptions have been both explosive (1718 7 , 1812, 1902–03, 1979) and effusive (1784, 1971–72). The most recent 1979 eruption ended with a 120 m × 860 m lava dome emplaced in the crater. As in many volcanoes worldwide, fatalities are associated with rapid accelerations in explosive activity 4 exemplified by the 1812 and 1902–03 St. Vincent eruptions.

Precursory unrest was markedly low-level prior to the 1971–1972 and 1979 eruptions, which began with <24 h of instrumentally recorded precursory seismicity 9 . Since the 1800s, several episodes of unrest without eruption (crater lake temperature changes, felt seismicity) have also occurred.

Increased background seismicity at La Soufrière from 1 November into December 2020 prompted an inspection of the crater by staff of the Soufrière Monitoring Unit (SMU), of St. Vincent and the Grenadines (SVG) National Emergency Management Organisation (NEMO), on 16 November 2020. Minor changes in fumarolic activity on the dome and the small lake occupying the eastern crater floor were noted. Seismicity reduced after 23 December 2020.

Surface activity was first recognised on 27 December 2020, when the NASA Fire Information for Resource Management System (FIRMS) detected a thermal anomaly inside the summit crater. On 29 December 2020, thermal anomalies and greyish-white emissions were observed. SMU staff discovered a new dome located in the west south-west sector of the crater, adjacent to the 1979 dome. Effusive activity continued for three months, with a rapid increase in effusion rate in early April 2021 leading to the explosive phase between 9 and 22 April. Thereafter, activity was limited to moderate SO 2 outgassing and generally low-level seismicity.

Here we describe monitoring data and the evolution of scientific interpretations. We also reflect on the information most critical to the generation of actionable forecasts of eruptive transition in a ‘real world’ setting.

Results and discussion

Network strengthening.

Overall emergency management and scientific support for La Soufrière volcano were coordinated by the staff of The University of the West Indies Seismic Research Centre (UWI SRC) in Trinidad, with assistance from the Montserrat Volcano Observatory (MVO) as well as regional and international collaborating partners. Initial observations and local support were provided by the SMU.

Limited resources and the COVID pandemic resulted in a much-reduced monitoring capacity at the onset of unrest (November 2020), with one working seismic station (SVB) 9 km from the volcano, and one continuous GPS station (SVGB) (Fig.  1 ). SRC reactivated the local observatory in late December 2020 and upgraded the monitoring network (Fig.  1 ). Eight broadband seismic stations were operating by the end of February 2021 and the ground deformation network was augmented by four continuous GPS sites (SVGR, SVGS, SVGF, SVGG) in addition to re-occupation of two campaign benchmark sites (JCWL and TBRK) (Fig.  1 ). A 9-prism EDM target was installed on the southern crater rim and weekly measurements attempted from six locations. Interferometric Synthetic Aperture Radar (InSAR) processing of available ALOS-2 and Sentinel-1 images augmented ground deformation monitoring. Sentinel-2 and PlanetLabs satellite imaged both the crater and colour changes of vegetation on the volcano’s flanks. Cameras installed at the Belmont Observatory (3 January 2021) and crater rim (24 January 2021), multispectral and radar satellite imagery, oblique aerial and terrestrial photographs and UAV aerial photography and photogrammetry allowed visual observations to document dome growth. From 14 January 2021, gas emissions were measured using a Multi-component Gas Analysing System (MultiGAS) and Ultra-Violet (UV) spectroscopy.

Hazard zones illustrate the potential for ground-based volcanic impacts such as pyroclastic flows and surges, tephra fall, ash fall and lahars that may impact the defined areas 7 . The boundaries of the zones are based on the past incidence of the hazards and areas of maximum projected extent, in addition, experience of these hazards at similar volcanoes is combined with theoretical considerations of mass discharge rates of magma, wind direction and morphology. The effects of effusive eruptions have had little impact on the determination of hazard zones.

Seismic monitoring

Seismicity increased slightly on station SVB in November 2020, but remained modest until 23 December 2020, averaging two events per day, with a maximum magnitude of 3.3 Mt and no reported felt events (Fig.  2 ).

Seismicity data: daily (bars) and cumulative (teal line) seismicity observed and a marker on the first important increase (17 January). The bars in blue represent seismic events related to fluid dynamics (low-frequency and dome emplacement) and the bars in dark red represent VT events. RSAM values: calculated with 1 min windows and no overlap; they correlate with VT swarms and explosive phase. Moreover, it shows evidence of lahar signals after the explosive phase. Deformation: radial extension from the vent observed at station SVGB, 9 km away from the crater, and associated uncertainties computed with GAMIT/GLOBK 48 . It shows a total movement of 62 mm towards the crater at the end of the explosive phase. C/S tot (CO 2 /H 2 S) concentration ratios (ppm) in the plume from MultiGAS measurements: First two data points evidence only H 2 S content, the remaining are a combination of H 2 S and SO 2 . The arrow shows the onset of explosive activity. Dome extrusion data: cumulative volume extruded in black line with an extrapolation until 6 April, extrusion rate in teal dots; the arrow marks the onset of rapid dome inflation as observed by a remote camera. The lowest bar shows the corresponding alert level for each day. In addition, vertical dashed lines show the onset of the effusive phase (orange) and the red area corresponds to the explosive phase.

Although dome extrusion started on 27 December 2020, no seismicity was recorded until 6 January 2021, with an average of two events per day up to 17 January, when there was a sharp increase to 60 events per day. Subsequently, low frequency (0.5–5 Hz) 10 , 11 events were observed and interpreted as related to the dome emplacement; the events were recorded only by the closest stations indicating a shallow source. Volcano-tectonic (VT) swarms occurred during 23–24 March 2021 (226 events) with >95% located at depths shallower than 5 km; and 5–6 April 2021 (476 events) with an abrupt transition to deeper locations (Fig.  3 ), which was interpreted as a new volume of magma ascending from ~10 km depth.

a Epicentres calculated showing concentric distribution. b Temporal evolution of depths during 23–24 March, most seismicity is shallower than 5 km. c Temporal evolution of depths during 5–6 April, seismicity is shallower than 5 km until 18:00 UTC on 5 April, when locations transitioned to deeper levels.

Banded tremor 12 , of increasing magnitude, began around noon (UTC time) on 8 April 2021, recorded by the closest stations at intervals of ~2.5 h (Fig.  4a ). This change was interpreted as indicating an imminent explosive phase 13 , with a source attributed to the excitation of shallow gas and fluid pockets 14 , 15 . The spectral content up to 10 Hz suggested that the banded tremor consisted of merging VT events (Fig.  4a ). The 8 th cycle transitioned to continuous tremor with increasing amplitude and stable frequency content over time (Fig.  4 ), suggesting repetitive events at a constant rate 13 . The first explosion was recorded at 12:41 UTC on 9 April, followed by a period of sustained, but pulsing, explosive activity and tremor from 16:00 UTC on 9 April to 06:00 UTC on 10 April (Fig.  4 ).

a Vertical time series at station SVV, RSAM and spectrogram showing the main features of the signal during the first 3 days: banded tremor, continuous and discrete explosions with exponential decays. b Vertical time series at station SVV, RSAM and spectrogram showing the main features of the whole explosive phase: increasing inter-explosion time, tremor build up to the last explosion and an abrupt end of the low-frequency tremor two hours after the referenced explosion. It also shows a lahar signal around 8 h after.

The time series, RSAM and spectrograms of the explosive phase is shown in Fig.  4 . The initially rapid rate of explosions and associated tremor made individual seismic events difficult to identify. Four stations stopped transmitting data during the first 36 h of the explosion sequence. Spectrograms for the explosive phase (Fig.  4a ) show a larger amplitude but the same stable frequency as during the build-up. Each explosion lasted between 3–23 min, followed by 2–3 h of exponential decay in tremor amplitude (green arrows in Fig.  4a ). Over the following two weeks, the pattern of seismic activity included episodes of short tremor bands accompanied by enhanced venting or explosive activity. Episodes of tremor were interspersed with long-period and hybrid earthquakes, with their rates of occurrence gradually decreasing prior to a period of high-level tremor on 22 April. The last explosion on 22 April was preceded by several hours of increasing-amplitude tremor (Fig.  4b ), with an abrupt end of low-frequency tremor shortly after the explosion. Seismic activity steadily declined from 22 April to early May, from an average of 354 events/day to 24 events/day. Up to November 2021, the seismicity remained sparse, dominated by low-frequency events.

Ground deformation monitoring

Forewarning of the effusive eruption was not recognised on the existing continuously operating GPS network (Fig.  2 ). However, a <10 cm line-of-sight shortening signal was observed in the crater area using ALOS-2 and Sentinel-1 radar, sometime between 19 and 31 December 2020. The associated deformation source was modelled as a ~63,000 m 3 dike intrusion, shallower than ~500 m deep (Fig.  5 ). Subsequently, no deformation was detected from the SAR platforms. No deformation was detected on the EDM time series during the effusive phase.

These visualisations use the Grandin and Delorme (2021) DSM. a Interferograms for descending (2020/02/25–2021/01/26, path 131, frame 3350) and ascending (2020/01/15–2021/01/13, path 36, frame 250) ALOS-2 radar. One fringe represents 11.4 cm in the line of sight; b Interferograms for descending pass (2020/12/07–2020/12/31, track 156, incidence 44.5°) and ascending (2020/12/07–2020/12/31, track 164, incidence 43.9°) Sentinel-1 radar. One fringe represents 2.8 cm in the line of sight; c Synthetic deformation predicted by an Okada dislocation dipping vertically (along-strike length: 600 m, along-dip width: 700 m, upper edge depth: 15 m), opening with a potency of 63,000 m 3 .

Onset of the explosive phase was accompanied by a rapid deflation recorded on the continuous GPS network on 9 April 2021 (Fig.  2 ). Between 9 and 22 April 2021, the SVGB station (Fig.  2 ) measured an overall cumulative horizontal displacement of ~43 mm northward and ~37 mm eastward and a subsidence of ~81 mm. Using a Mogi point source 16 , the associated surface deformation was modelled by migration of ~50 × 10 6  m 3 of magma from a source at ~6 km depth. After explosive activity ended, slow deflation was observed over several months.

Gas and geochemical monitoring

Gas measurements in January 2021, using UV spectrometer and MultiGAS instruments , detected no SO 2 . The concentration ratio (ppm) of carbon to total sulphur (C/S t ) was measured by MultiGAS at the summit (Fig.  2 ). A C/S t (=CO 2 /H 2 S) ratio of 85 and 30.6 (Fig.  2 ) was obtained on 14 and 15 January, respectively. Minor SO 2 (<1 ppm) was detected in February 2021, with a C/S t (=SO 2  + H 2 S) concentration ratio of 10 measured on 1 February and 11 on 18 February, before increasing to ~20 on 23 March 2021. Plume compositions during the effusive phase were dominated by a hydrothermal signature (Fig.  6 ). On the afternoon of 8 April, a coastal traverse yielded the first detection of SO 2 in the gas plume with a mass flux of 80 tonnes/day. The TROPOMI instrument on board Sentinel-5P also detected SO 2 during an overpass on 8 April at 17:25 UTC, confirming the change in plume composition. During the explosive phase (9–22 April) only satellite (Sentinel-5P) SO 2 measurements were possible, with values ranging from 2.76 × 10 5 tonnes/day on 10 April to 331 tonnes/day on 22 April. Over the two months following the explosive phase, coastal traverse measurements of SO 2 flux decreased from ~800 to ~200 tonnes/day, and then maintained this average through to November 2021.

Ternary diagram of SO 2 *3-CO 2 /2-H 2 S*5 showing the plume compositions obtained during the extrusive phase. HD hydrothermal dominated, DHM deep hydrothermal magmatic, SHM shallow hydrothermal magmatic, DM deep magmatic, SM shallow magmatic. Boundaries were obtained from the Central American Volcanic arc.

On 16 January 2021, samples were collected from the front of the lava dome. In April 2021, scoria and clasts from pyroclastic density currents emplaced during the explosive eruptions were sampled. XRF analysis of major elements shows both have basaltic andesite bulk compositions (Fig.  7 ).

TAS classification diagram (‘Total Alkalis vs Silica’) to compare the composition of the 2020–2021 dome and other explosive products with other eruptions of La Soufrière, St. Vincent. Results were obtained by XRF at the University of Plymouth.

Preliminary petrographic analyses of the dome rocks indicated a phenocryst assemblage similar to past eruptions, consisting of plagioclase, clinopyroxene and Fe-Ti oxides with sparse olivine and abundant gabbroic clots 17 (Fig.  8 a, b ). Where present, olivine is invariably heavily altered, with symplectites intergrowth of forsterite and Fe-oxides common (Fig.  8b ). Groundmass textures show evidence of late-stage disequilibrium, including groundmass crystals with localised alteration of orthopyroxene microlites to Fe and Mg oxides (Fig.  8c ). Dome rocks are vesicular with textural evidence for fracturing and annealing of fluid pathways (Fig.  8a, d ).

Five full thin section image maps, acquired on a Zeiss Gemini 300 SEM at the University of East Anglia, UK, were generated from clasts sampled in January 2021 from the growing dome and analysed to identify common textures as displayed in a – d . a Image showing vesicular nature of the dome sample (vesicles in black) with examples of the crystal population labelled: plagioclase (fsp), clinopyroxene (cpx), Fe-Ti oxides (ox) and gabbroic clots (outlined by yellow dashed line). b Example of heavily degraded olivine (ol) (blue box) shows close-up of this texture. c Examples of localisation of degradation of orthopyroxene crystals to oxides (dashed turquoise line in c ). Higher levels of degradation observed close to larger oxides (e.g. image c and ci, x) comprises ~5% of each thin section. Elsewhere, orthopyroxenes are un-degraded (cii, y). d Example of a plagioclase phenocryst (fsp) with a fracture that has been later filled by melt and crystals, this is observed several times across the five sections analysed. Red box shows a close-up of this structure showing clinopyroxene, oxides and glass infilling the fracture.

Dome growth and other visual observations

Initially, the new dome grew uniformly in all directions, reaching 70 m in height, subsequently elongating in the NW-SE direction (Fig.  9 ). Gas vented through a small depression in the dome’s summit. The shape evolved to an elliptical lava coulee with two distinct lobes, confined within the moat between the 1979 dome and the inner wall of the Summit Crater (Fig.  9 ). Rock fall activity from the margins was very limited, while no deformation of the crater floor was observed in flow fronts. Distinct marginal levees developed with radial and linear flow patterns appearing on the lava surface. Thermal images on 16 January 2021 yielded surface temperatures of up to 600 °C.

A map of the summit crater of La Soufriere, St Vincent, showing full and partial footprints for the new lava dome that first appeared on 27 December 2020. Footprints were extracted from multispectral and radar satellite imagery, oblique aerial and terrestrial photographs and drone surveys. Background is pre-eruption imagery that shows the 1979 lava dome inside the summit crater.

Extrusion rates calculated for periods from 1 to 34 days varied between 0.95 and 2.65 m 3 /s ± 0.59 m 3 /s with a long-term average of ~1.85 ± 0.14 m 3 /s (Fig.  2 ). The cumulative volume reached ~13 × 10 6  m 3 by 19 March 2021, when the dome measured 912 m long, 243 m wide and 105 m high. Extrapolating the linear trend through to 9 April suggests a final volume of ~18 × 10 6  m 3 . On 6 April, observation via the installed camera indicated a rapid increase in dome height with incandescence becoming visible over the crater rim from the Belmont Observatory (Fig.  1 ) on the evening of 8 April. Cyclic gas emissions at the central vent occurred correlated with the banded tremor. During the explosive activity, the new lava dome and significant parts of the 1979 lava dome were destroyed, as confirmed by satellite imagery on 10 April from ICEYE (02:02 UTC) and Capella (14:03 UTC).

As explosive activity intensified close observation of discrete events became more difficult. By 12 April pyroclastic density currents (PDCs) had descended several valleys on the southern and western flanks of the volcano and reached the sea. Following that, enhanced venting or Vulcanian-style explosive activity episodically occurred until 22 April. Some explosions generated PDCs in valleys on the western flanks of the volcano.

Crisis response: warning and decision-making systems

The SRC supports local authorities for strengthening preparedness and communicating volcanic hazards through product development (e.g., integrated volcanic hazard maps). The map for St. Vincent (Fig.  1 ) is a colour-coded depiction of the expected impact of volcanic hazards across the island 7 . The volcanic alert level system (VALS, see  Supplementary Information ) translates the volcanic activity level into required actions during volcanic unrest. Operational constraints in country meant that any increased likelihood of an explosive eruption needed to be communicated 24–48 h before onset to enable successful evacuation.

Distinguishing rapid accelerations in activity after the onset of an eruption, in particular, transitions to an explosive eruption, are a globally recognised forecasting challenge 18 . It is also important to recognise when the probability of explosions decreases, to lower the alert level. Here we identify the practical challenges in recognising and communicating these changes. We highlight the importance of preparedness, diverse forms of communication, and structured approaches to the interpretation of scientific data, development of evidence-informed forecasts and assessment of risk during volcanic crises.

Short-term contribution to decision-making: assessment of risk

Current uncertainty in understanding volcanic processes contribute to a variety of opinions on causative mechanisms and prognoses, particularly during an evolving crisis. In addition, the aleatoric uncertainty associated with the complex behaviour of volcanic systems requires caution against a deterministic interpretation that over-emphasises one specific outcome 19 . SRC used the framework of a structured expert elicitation 20 , 21 around a range of scenarios, to generate both consensus (a collective ‘most likely’ prognosis) and to represent the diversity of opinions.

Weekly elicitations (January to early March 2021) favoured continuation of effusive activity (~80%) each time. The likelihood of an escalation to explosive activity in the following weeks remained at median probability of ~10%. However, following the first VT swarm (23–24 March), elicited estimates for a transition to explosive activity doubled to a median probability of ~20%. With the appearance of banded tremor (8 April), elicited probabilities of explosive activity tripled to a median value of ~60%. The authorities of SVG were alerted to this increase in volcanic activity. The alert level was raised to Red on 8 April at 18:00 UTC triggering the evacuation of ~16,000 persons from the Red and Orange Zones, prior to the start of explosive activity on 9 April at 12:41 UTC, with no reported serious injuries or loss of life.

The visual observations of declining surface activity, lowered seismic activity and declining gas output, coupled with the slow deflation signal observed since 22 April, were key drivers for the lowering of the alert level to Orange on 6 May.

Longer-term contribution to decision-making: risk awareness, preparedness and communication

Hazard assessments and analysis of past events have continuously been updated in response to new understanding 22 , 23 , 24 , 25 , 26 . Further, improvements in communication of improved understanding of hazards have been assessed and implemented in hazard planning by NEMO and SRC. The Volcano Ready Community Project (VRCP) led by SRC in collaboration with NEMO, launched in April 2018 and completed in April 2021, targeted twelve northernmost communities of St. Vincent in the Red and Orange hazard zones of the most recent volcanic hazard map 7 . The VRCP, enabled community plans to be drafted and integrated into the national response mechanisms prior to the 2020–2021 eruption.

Communication pathways: transition from extrusive to explosive

Communication of messaging between SRC and NEMO was harmonised. A continuous flow of near real-time information was provided to the public and stakeholders about volcanic activity, hazards, and risk reduction. These communications maintained credibility in the monitoring capability of SRC 27 , 28 . A similar communication strategy employed by the USGS, in response to the 2014–2015 Kilauea volcano lava-flow crisis, was shown to be a highly effective approach 29 and aligns with volcano observatory best practices for operations during crises 6 .

Based on best practice and evidence, risk communication products were developed to target different learning styles, media platforms and preferences 28 . These products included visual, print and audio products, and were combined with live scientific presentations during media interviews and to special interest groups. Social media schedules and posts were coordinated, while SRC scientists on island participated in daily activity updates on local television and radio stations, and provided cabinet briefings and updates to decision-makers. Scientists participated in virtual and drive-through community meetings for Red Zone residents with live online streaming and simulcast on local television and radio. An important facet of uncertainty during eruptions is dealing with misinformation and rumours. The strategy of maintaining a continuous presence on social media (Fig.  10 ) and the use of FAQs and short interviews allowed growing concerns or misapprehensions to be addressed. The frequency of these communications was influenced by changes in the ongoing activity. International scientists were also encouraged to amplify existing messages and use SRC materials in discussing the eruption with their local media.

Summary of UWI SRC communication strategy and response throughout the 2020–2021 eruption of La Soufrière, St. Vincent eruption.

Another important dimension was systematised internal communication. External contributions of data were facilitated by a team lead who was responsible for internal communication and coordinating data requests. This approach also facilitated international collaborations and engagement with academic scientists, which supported the SRC to develop conceptual models.

With the start of the explosive phase of the eruption, social media posts were still the primary tool used by SRC to communicate with the public. Scientific bulletins were shared directly on these platforms, with the addition of voice notes shared via mobile networks. Daily activity updates on local radio and television stations continued. Visual, print and audio products now also focussed on explanations of, and recommended responses to, the primary volcanic hazards (pyroclastic density currents, ash fall and lahars) being observed.

Crisis management

Volcano monitoring data enable scientists to provide short-term forecasts or advise of possible changes during an ongoing eruption 30 . However, for successful crisis management, monitoring data and interpretations need to be: (a) framed within the context of wider scientific knowledge, (b) presented in the context of decision-making (‘useful, usable and used’) 31 and (c) effectively communicated to diverse audiences 32 . The St. Vincent case provides an important demonstration of how these principles were integrated, complementing synoptic analyses of the state-of-the-art in volcano observatory crisis operations 6 , 33 . Next, we discuss the key lessons from our analysis of response to the unfolding events, particularly the eruptive transition, and assess the role data and models played in decision-making. We also reflect on the constraints on best practice imposed by finite resources, and how this can be improved.

Conceptual models and their value in forecasting eruptive transitions

Historically, La Soufrière volcano can produce both explosive and effusive eruptions over time intervals of weeks to months. However, transitions in behaviour can occur over only a few hours 6 and pose acute challenges to risk management; particularly when decisions to evacuate are exacerbated by resource or space constraints that affect the tolerability of evacuations. Analysis of previous eruptions in St. Vincent has demonstrated that compliance with long-duration evacuations will dissipate, a feature shared with crises at other volcanoes 4 .

A working conceptual model of volcanic behaviour was created and developed in real-time, which was used to inform the scientific response to emergency management and advise the authorities. Critically, during the effusive phase our evolving working model was used to anticipate explosive transition or other significant changes in activity.

In early January 2021, we interpreted onset of the eruption as the consequence of the injection of fresh gas-rich magma into a sub-volcanic reservoir, making its way to the surface 3 . However, this interpretation could not explain the comparatively low seismicity rates, lack of surface deformation and near-constant extrusion of lava (Fig.  2 ). The presence of a ductile well-connected magma ascent pathway was proposed to reconcile these early seismic observations 34 . The absence of deformation and steady extrusion could be explained by either (i) a magma source that maintains a near-constant overpressure 35 or (ii) that a large magmatic source, relative to the material extruded, resulted in pressure decay in the reservoir being too small to be detected 36 , 37 or (iii) that hot magma mush surrounding the source region, in combination with the viscous flow in the crust, maintained the high pressure 37 , or (iv) some combination of these processes. The diversity of explanations, informed by monitoring observations, was important for assessing the potential for explosive activity, and the timescale over which this might happen. At that time, there were no evacuations in place, but existing hazard assessment and outcomes from past simulations (e.g., Tradewinds Exercise 2019 38 ) demonstrated that risk to the northern population could rapidly become high, with a 24–48 h interval needed for full evacuation.

By early February, the absence of detectable SO 2 , however, led us to infer the presence of degassed magma remaining within the conduit, following the 1979 eruption, confined by a strong ‘cap’, was slowly being pushed up by a new injection of gas-rich magma. By early March, the similar composition and petrographic characteristics of the extruded dome rocks, in comparison to past eruptive products, had reinforced this model. Similar behaviour has been inferred at volcanoes such as Kilauea in Hawai’i, where in 2018 near real-time geochemical analysis of lava indicated magma characteristics consistent with progressive flushing of residual magma in the conduit 39 .

The epicentres of the intense seismic swarms before the explosions show a concentric distribution of earthquakes around the volcano (Fig.  3a ). This suggested magma ascending through the volcanic conduit. Most (>95%) of the estimated epicentres were located above 5 km until 18:00 UTC on 5 April, when seismicity migrated to deeper levels (Fig.  3a, b ). This sudden transition in depth was considered evidence of increased deviatoric stresses around the conduit, possibly related to a new intrusion of gas-rich magma.

In our evolving model, obstruction by the cap material and overlying 1979 dome prevented fresh magma from reaching the surface and limited SO 2 flux to volumes low enough to be scrubbed by the volcanic hydrothermal system, until April 2021. We speculated that the accelerated extrusion rate observed after 6 April, was after the high-viscosity magma cap was displaced by new lower viscosity gas-rich magma. Banded tremor, consisting of merging VT events, attributed to the excitation of fluids at relatively shallow levels, was observed one day prior to the onset of the explosive phase 14 , 15 . This observation suggested possible pressure oscillations within the ~6 km deep magma reservoir as the trigger of highly periodic tremor events. This strongly implied the imminent passage of gas-rich material from depth into the shallower edifice, consistent with the first detection of SO 2 flux on 8 April (Fig.  6 ). Then on 9 April, gas rich magma reached the surface and conditions for explosive fragmentation were realised, which correlated with the observation of syn-eruptive deflation (Fig.  2 ).

The working conceptual model provided a robust framework against which these rapidly emerging data could be interpreted and understood. This working model illustrates the need to interpret scientific data in real-time to inform rapid emergency decision-making and the difference between theoretical models and critical interpretations that trigger real-world, life-preserving decisions. The conceptual models, synthesised from quantitative data, were necessary for decision-making and formed a framework to create actionable evidence for responding to an acceleration in activity. Nonetheless, the conceptual model was also strongly informed by quantitative outputs from generic models for different aspects of volcanic behaviour and the input of boundary conditions obtained from new knowledge of the magma composition and observations of dynamic behaviour. Further scientific analysis with longer-term research programmes and quantitative modelling will test and improve these models. An important dimension of fully quantitative models is the recognition of generalizable insights relevant to other settings worldwide where rapid transitions in activity occur, that can be derived from empirical observations in real time.

The role of uncertainty and impact of monitoring in a resource-constrained setting

Interpretation of the monitoring data and development of a preliminary conceptual model were associated with large uncertainties when anticipating eruptive behaviour throughout the unrest episode. These uncertainties created both temporal (when) and spatial (how big) challenges. Specific uncertainties included: (i) interpreting the extent that seismic unrest patterns were similar to historical background seismic activity at La Soufrière volcano; particularly long episodes of unrest preceding >VEI4 explosions; (ii) during steady-state dome growth, distinguishing monitoring signals indicative of a potential acceleration of activity from normal behavioural fluctuations, in the absence of any significant measured deformation; and (iii) during the explosive phase anticipating the likely duration and peak intensity of explosions, given the range in size and documented intensity of the previous eruptions 8 . This contributed to uncertainties in interpreting signals that might represent the onset of an explosive phase and reduced timescales over which accelerations or decelerations in the intensity of activity could be confidently attributed to changing behaviour. Coping with uncertainties framed our conceptual model and attendant different scenarios. Our combined expert view of likelihoods captured via expert elicitation, fed into decision focussed advice (e.g., VALS for La Soufrière). This approach avoided interpretations dependent on single outcomes 19 , which inadvertently minimised aleatoric uncertainties or ignored ambiguities in datasets. The St. Vincent case demonstrates the benefits of the structured expert elicitation methodology to capture uncertainty.

An important factor in generating epistemic uncertainty was the relatively sparse monitoring network at the onset of the eruptive episode, which was a direct consequence of financial constraints on the monitoring operations. Limitations in the density of the network challenged our ability to definitively say whether the onset of the effusive eruption would have been instrumentally detected. However, as the monitoring network strengthened, observed signals were interpreted against improvements in data volume and accuracy. For example, additional GPS stations installed during the eruption greatly improved the sensitivity of the network. A sensitivity study 40 , demonstrated that the network had no significant azimuthal gaps, but suffered from a lack of near-field stations to capture shallow deformation sources. In addition, interpretation of the low amplitude banded tremor detected on 8 April, reinforced by the observation of a detectable SO 2 gas flux later that day, was the most salient information to feed into changed views on explosion likelihood. Similarly, detailed seismic analysis and near real-time satellite and deformation measurements contributed to the anticipation of waning explosive activity during the acute phase (9–11 April).

The relatively late detection of effusive eruption onset and the importance of new data during the eruptive transition, clearly demonstrate that well-resourced multi-parametric networks are of high value. The reality in settings like St. Vincent is often different and network strengthening took place during the eruption, creating important safety concerns. SRC used a fieldwork life-safety risk assessment 41 with an estimated hourly risk of fatality exceeding 10 −4 during the initial fieldwork period (see  Supplementary Information ). This procedure gave strong justification for the use of a helicopter and provided an opportunity for monitoring scientists to express any concerns and contribute recommendations on the best field practices.

The value of collaborative preparedness, awareness and communication

Identifying local needs and obtaining evidence of the efficacy and impact of the SRC’s risk communication in the vulnerable communities 42 was a persistent challenge largely due to the Education and Outreach (E&O) team’s remote operations. Harmonisation of messaging was essential 43 . Close collaborations with NEMO strengthened communication efficacy and reinforced local capacity for effective communication. In turn, this provided SRC with insight into appropriate content for its communication products. These types of relations take time and resources. The groundwork was essential to the success of managing the crisis in a rapidly changing volcanic situation with a requirement for the implementation of advice into action.

Wide acceptance of the risk information was indicated by the authorities acting decisively on advice provided by SRC, resulting in increased alert levels and the issuance of evacuation orders 24 h ahead of the first explosion. Furthermore, the public understood the increased volcanic activity and complied with evacuation orders.

Integrated approach: value in anticipating eruptive transitions

Effective crisis science and consequent volcanic risk reduction is a partnership between scientists, response agencies and the affected communities 44 , 45 , It begins with the robust gathering and interpretation of scientific data, before, during and after a crisis. Our analysis provides an excellent case study of the principles outlined in recent synoptic analyses 6 , 33 .

However, important challenges arise in the acute crisis phase where decision-making timescale appropriate to the lifetime of the eruption (typically weeks to months) contract into minutes and hours with the growing prospect of a change in behaviour. As a transition threatens, uncertainty rises and demands dynamic interpretation of emergent datasets. Thus, our analysis here particularly reflects on the important drivers of risk in this moment.

An important dimension was the capacity to interpret data against a flexible conceptual model that expresses and formalises uncertainty. Further, the understanding from previous research 7 , 8 , 9 , 13 , 22 and agency-to-agency interactions that framed social context and societal constraints were important. Monitoring agencies need to be responsible for interpreting datasets and anticipating changes on societally relevant timescales. This responsibility also underpinned our communication strategies and timescales. The long-term relationship we described here increased the chances that advice given during an eruptive transition was more readily translated into actions by local emergency managers, and in turn, the populace at risk.

Research that accounts for the realities of managing crises could further improve effective decision-making. In volcanology, counterfactual analysis is a powerful way to understand what might have transpired 46 . A counterfactual analysis to include the range of possible scenarios and outcomes using the ‘real time’ evolving knowledge gathered, would assess whether the decision-making strategy here was robust to all eruptive outcomes. For example, considering situations where explosive activity happened at an earlier stage or explosions that generated larger pyroclastic density currents. Similarly, a focus on emerging petrological techniques that allow rapid forensic examination of timescales of disruption, degassing and ingress prior to other eruptive episodes would have significantly helped with the interpretation of changing monitored signals at the acute crisis point.

Finally, it is important to acknowledge the implicit risk to monitoring scientists during the intra-eruptive network strengthening. Our analysis demonstrates the value of the strengthened network, as well as remotely observed data, to data interpretation despite the risk in this particular case. Research that improves understanding of the effectiveness of monitoring networks would help identify strategies that best minimise risk, while maximising data benefit.

Operating in a resource-constrained setting influenced scientific response and emergency management. The steady global growth of disaster risk, volcanic or otherwise, compels disaster response agencies to fortify disaster preparedness capabilities and to ensure that institutional capacities are in place to optimize effective planning, response, and mitigation. Our assessment of the 2020–2021 La Soufrière eruption demonstrates the critical controls, produced over longer timescales, of an effective response during an acute crisis at the moment of eruptive transition.

Confidence in our conceptual models of reactivation via a gas-rich magma at depth was improved through the strengthening of the seismic network, real-time deformation and dome monitoring, changes in gas composition and petrological sampling. Nonetheless, as monitored signals shifted and the likelihood of transition increased, longer-term preparedness measures allowed us to disseminate rapidly changing information effectively on short timescales and contextualise our advice on timescales appropriate for actions to prevent loss of life, while minimising impacts on livelihoods.

The seismicity routinely used to assess the status of La Soufrière volcano derives from an eight-station network on and around the volcano. Daily event counts are used to recognise changes within the system. The rapid densification of the network in early January 2021 (Fig.  1 ) facilitated the recording of micro-seismic signals generated by the dome emplacement process, as well as the detection and location of VT earthquakes. The location inversion was performed using a generic volcanic velocity structure 47 , although this velocity model is not a result of 1D tomography, it provides consistent and clustered results when no shallow velocity structures are identified. The size of the remaining volcano earthquake types that could not be located was assessed by tracking the number and distance of stations recording those events along with the duration of the events as recorded by the crater rim station, SSVA and then by SVV. The recorded events were identified and processed by a team of seismology technicians at SRC and cross-checked with the seismologist on duty at the Belmont Observatory. An automatic event detection system was introduced after several weeks to support the analysis. Routine RSAM and spectral analysis calculations were also used in assessing the status of the system.

GPS data were collected using Trimble NetRS and NetR9, and Septentrio PolaRX5 dual-frequency receivers and processed using GAMIT/GLOBK software (version 10.71) 48 . EDM were captured from six base locations (Fig.  1 ) in collaboration with the Lands and Surveys Department, SVG using a Leica Flexline TS06 total station. Radar imagery was acquired from Sentinel-1 satellites of the European Space Agency (ESA) and the ALOS-2 satellite of the Japan Aerospace Exploration Agency (JAXA). The ALOS-2 images were originally made available under an ALOS-2 6th Research call project 49 and were then also made available through an emergency collaboration with NASA. Formal requests were made to ESA and JAXA for additional collections, which were subsequently granted. Sentinel-1 repeat times were increased from 12–18 days to 6 days and ALOS-2 repeat times were increased from approximately annual to every 14 days. ALOS-2 data were processed using the GAMMA software 50 and topographic corrections were made using the 30 m ASTER GDEM. Sentinel-1 data were processed with the NSBAS processing chain 51 , 52 which relies on the legacy software ROI_PAC 53 . Topographic corrections were made using the 1 Arc-second SRTM DEM, and atmospheric corrections were performed using ECMWF’s ERA-5 meteorological reanalysis 54 .

A portable Multi-component Gas Analysing System (MultiGAS) instrument composed of an infrared spectrometer and electrochemical sensors (plus air temperature, atmospheric pressure, and relative humidity sensors) allowed detection of the in-plume concentrations (ppm) of H 2 O, CO 2 , SO 2 and H 2 S 55 . The instrument consists of a Gascard IR spectrometer for CO 2 determination (calibration range: 0–3000 ppmv; accuracy: ±2%; resolution: 0.8 ppmv) and of City Technology electrochemical sensors for SO 2 (sensor type 3ST/F; calibration range: 0–200 ppm, accuracy: ±2%, resolution: 0.1 ppmv), H 2 S (sensor type 2E; range: 0–100 ppm, accuracy: ±5%, resolution: 0.7 ppmv) and H 2 S (sensor type EZT3HYT; range: 0–200 ppm, accuracy: ±2%, resolution: 0.5 ppmv), all connected to a Campbell Scientific CR6 datalogger. The acquired data were post processed using the Ratiocalc software 56 with CO 2 /S t ratios expressed in molar ratios,

Rock samples were collected directly from an active lobe of the dome on 16 January 2021, using a bucket. These were crushed and analysed from bulk composition using XRF. Subsequently, samples of scoria (erupted 9 April) and blocks from PDCs (emplaced 13 April) were also analysed. The dome samples were thin sectioned by Jesús Montes Rueda at the University of Granada and by Ian Chaplin at Durham University, and carbon coated. Scanning Electron Microscopy (SEM) imaging with Energy Dispersive Spectroscopy (EDS) analyses were conducted at the University of East Anglia (Zeiss Gemini 300 field emission SEM with Oxford Instruments Ultim Max 170 EDS). Imaging and analysis were conducted at 10 kV (UEA) with a working distance of 8.5 mm.

Dome volume monitoring

Growth of the new lava dome was monitored primarily through the application of photogrammetry, using images acquired from the summit crater rim or aerial images from observation flights using fixed-wing aircraft, helicopters or consumer grade unmanned aerial vehicles (UAVs). Images were processed using either ImageJ or the photogrammetry software package AgiSoft Metashape, the later used to generate 3D models of the lava dome from which volume and extrusion rates were determined. Due to the lack of a quality pre-eruption DEM, it was assumed that the dome had a purely flat base and exhibited either a pure hemispherical or half ellipsoidal shape. In reality, where the new lava dome reached the 1979 lava dome and the inner slopes of the Summit Crater wall, the dome had a slightly trapezoidal cross-section. Consequently, the volume data presented in Fig.  2 is overestimated by as much as 20%. The photogrammetry surveys were conducted at intervals of up to 34 days due to access and safety concerns (they were conducted from locations along the rim of the Summit Crater). Between surveys, radar and multispectral imagery from the Sentinel-1 and -2 satellite constellations and from Planet.com were used to track the extent of the footprint of the new lava dome.

Hazard and risk evaluation

Two complementary activities were undertaken to quantify anticipated risk from the La Soufrière and provide an evidence base for internal decision-making during the eruption. The first, a fieldwork life-safety risk assessment provided estimates of the chance of fatality from an unheralded explosive event, which was a concern during the initial stages of the eruption when network strengthening fieldwork had to be conducted. The second, a formal approach to eliciting expert judgement, provided quantitative estimates of the likelihood for anticipated eruption scenarios that could inform both the fieldwork life-safety risk assessment and the provision of advice for emergency response and public safety throughout the eruptive sequence. This was undertaken on a regular basis to quantitatively assess the evolution of volcanic activity and possible future scenarios.

The fieldwork life-safety risk assessment was conducted following the VoLREst methodology 37 . The two-step procedure involved: (1) establishing the volcano-specific parameters, e.g., vent location, sites of interest, hazards of concern, eruption size categories, probability of exposure, probability of fatality and threshold of acceptable risk and (2) estimating eruption probabilities. Ideally the first step is undertaken in advance of any activity, in this instance parameters were identified after the extrusive eruption commenced, including elicited probabilities of exposure and fatality. Probabilities for step two were taken from the expert-elicitation for anticipated eruption scenarios. These values are combined in VoLREst to calculate hourly risk of fatality with increasing distance from the volcano (see Supplementary Fig.  4 ).

A structured elicitation process was initiated on 7 January 2021 to provide a framework for estimating quantitative probabilities of different eruption scenarios, particularly the likelihood of escalated eruptive (explosive) activity. Given that the eruption had already commenced, with extrusion at the surface in the form of a dome, three possible outcomes for the next stage of volcanic activity were considered: (i) effusive activity continues; (ii) eruption ends; and (iii) escalation to explosive activity. These scenarios formed the core of the questions during the elicitation, with probabilities elicited on a biweekly basis, with flexibility in adjusting the timing and content to address changing volcanic conditions, additional monitoring data, and/or questions that arose (both internally and externally) regarding possible scenarios.

The elicitation process included a briefing that was held approximately every two weeks to provide updates on the status of the volcano and monitoring operations. Previous elicitation results were discussed in depth during each meeting, together with a review of the scientific working model of the volcano and its ongoing eruptive state, and finally any possible changes to the elicitation questions. The group was then elicited immediately following the meeting, such that the estimated probabilities were based on consistent information available to all participants. Participants were asked to provide estimates of the median likelihood of a given event in a set time period, as well as estimates of 5 and 95% quantiles, to provide uncertainty ranges on their values. The Excalibur software package 19 , which implements Cooke’s “Classical Model” 18 , was used to undertake the calculations. Estimates for the following one-week period and one-month period were elicited.

Early warning and preparedness

The Volcano-Ready Communities in St. Vincent Project (VRCP) was a grant funded community-based capacity-building programme that aimed to reduce vulnerability to the multi-hazard environment of the La Soufrière volcano across twelve (12) communities in St. Vincent. It was executed during the period April 2018 to November 2021 through collaborations involving the SRC, NEMO, the Red Cross Society and the Community Development Division of St. Vincent and the Grenadines.

Project activities were designed to enhance community early warning procedures; increase adaptive capacities; strengthen awareness; and enhance response capacities to enable community residents to effectively plan, prepare for and respond to the impacts of volcanic and other hazards. Activities included the production of a variety of print and digital public awareness and education materials (posters and brochures, film, photographs and public exhibits) disseminated through a series of multi hazard, gender-sensitive community sessions that facilitated public engagement. Community awareness and education materials included documentaries on best practices and lessons learnt from the 1979 eruption, were also captured through story telling in film, animation and photography. A total of four one-week educational sessions were conducted between the months of April 2018 and October 2019, involving both secondary school students and volunteers (32–45 participants per session). Other public awareness education activities included a crisis management scenario workshop, attended by 120 Fourth Form geography students, where students also participated in practical experiments that demonstrated the science of volcanic eruptions. In addition, a group of 80 Fourth Form students took part in a guided field visit to the volcano’s summit, where they were introduced to SRC’s volcano monitoring mechanism for La Soufrière volcano and its evolution since the 1979 eruption.

In addition, training and Workshops were conducted with community volunteers to develop community level volcano emergency plans for the citizens in the high-risk Red Zone of the Soufrière Volcano. Two workshops: (1) Initial Damage Assessments (IDA) and (2) Vulnerability and Capacity Assessments (VCA), were held with fifteen persons from seven communities located in the Red Zone participating in both workshops. The group consisted of four males and eleven females, with eight participants comprising of young adults (15–24 years). This facilitated incorporation of community hazard maps and databases identifying and mapping vulnerable persons, human and transportation resources for each community to be integrated into the national response mechanisms.

Community Emergency Response Teams (CERTS) certification training was also conducted for each community, with a total of 72 community volunteers being trained under this program. Participants were instructed on disaster preparedness for volcanic and other hazards that may impact their community and trained in basic disaster response skills, such as fire safety, light search and rescue, team organisation, and disaster medical operations. In addition, participants also received information on: Introduction to Disaster Management, Mass Care, Damage Assessment and Shelters and Shelter Operations. In addition, CERT teams were provided with personal and community emergency response tools and equipment upon completion of the training. Stakeholders (government, civil society, private sector) were engaged to assist four communities with the development and identification of resources for the implementation of the community response plans and provide support to test the National Volcanic Emergency Response Plan during Tradewinds 2019 38 .

Risk communication

One of the key functions of the SRC is to provide information and scientific advice to governments, as well as to a large body of disaster management stakeholders and the general public. This was achieved through regular updates on volcanic activity as well as monitoring plans and techniques. At the onset of the eruption, the main objectives identified to guide the risk communication strategy were (i) to reinforce capacity of local authorities to communicate effectively; (ii) to promote public recognition of primary sources of information and (iii) to facilitate public understanding of science related to ongoing volcano monitoring techniques, volcanic activity, potential hazards and hazard mitigation measures.

The Education & Outreach (E&O) section of the SRC set out to reinforce NEMO’s capacity by supporting the implementation of its communications plan. This was executed through regular consultations between the two agencies to share communication expertise and collaborative hosting of key public education activities. The SRC developed communication products to address specific areas of need.

As part of intensified efforts to reinforce public recognition of primary sources of information, SRC spokespersons were identified for the eruption, visibility and responsiveness on social and traditional media were increased and published communication products were branded with SRC logo. A standardized statement identifying SRC and NEMO as official information sources were integrated as a consistent message across products, including interviews.

Where possible, communication products contained jargon-free language and alternatively, simple explanations for technical terms were provided where the scientific language was unavoidable. A customised communications approach to address different learning styles was adopted and information was disseminated through multimedia to targeted audiences. Eruption-related questions trending on SRC social media platforms provided the basis for these user-informed products.

Data availability

The raw datasets that informed the analyses presented in this study are available from the corresponding author on request. Sentinel products were freely downloaded from the Copernicus Open Access Hub ( https://scihub.copernicus.eu/ ).

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Acknowledgements

For their support to the monitoring of the eruption of La Soufrière, the staff of the SRC and MVO are thanked. Roderick Stewart is thanked for his service as a Scientific Team Lead in St. Vincent. We thank the Director and staff of NEMO, the SMU, Lands and Surveys Department of St. Vincent and volunteers assisting with field work for campaign EDM and GPS occupations. Willy Aspinall is thanked for sharing his insights and expertise throughout the unrest and eruption episode. We thank the ESA and JAXA for tasking systematic Sentinel-1 and ALOS-2 acquisitions over La Soufrière. We thank the Capella Space and ICEYE companies for providing high-resolution SAR images of the volcano during the explosive phase. ALOS-2 SAR data were made available by the Japanese Aerospace Exploration Agency (JAXA) for the sixth RA proposal (PI no. 3153). Collaborating agencies such as NASA, IPGP, LOA, AERIS/ICARE, CSIC, USGS VDAP, USAID, CIMH, KNMI, CEOS Volcano Demonstrator all provided support for remote sensing data analysis. We thank the MOUNTS platform for their automated analyses of Sentinel data for La Soufrière, SVG. Fieldwork for JB and PC and petrological analysis was supported by NERC Urgency Grant NE/W000725/1 and Royal Society Apex Award APX\R1\180094. We thank David Pyle, Gregor Weber and Jon Blundy for assisting with geochemical analysis of dome samples. Funding for the VRCP project was granted to RR (Grant No. GA 43/STV) through CDB’s Community Disaster Risk Reduction Fund (CDRRF) and is supported by the Government of Canada and the European Union. We also thank the Executive Director and staff of CDEMA for logistical support and resource mobilisation efforts.

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E. P. Joseph, M. Camejo-Harry, T. Christopher, R. Contreras-Arratia, S. Edwards, O. Graham, M. Johnson, A. Juman, J. L. Latchman, L. Lynch, V. L. Miller, I. Papadopoulos, K. Pascal, R. Robertson, G. A. Ryan & A. Stinton

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Montserrat Volcano Observatory, Flemmings, Montserrat

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Contributions

E.P.J. took the lead in writing the manuscript and oversaw the overall management of the UWI SRC during the volcanic crisis. M.C-.H., T.C., A.S., R.R., J.B., L.L. and P.C. conducted fieldwork, collected data, performed analysis and contributed to the interpretation of results. V.L.M. collected data, performed analysis and contributed to the interpretation of the results. K.P., G.R., J.L.L., R.C-.A., M.J. and I.P. analysed data and contributed to the interpretation of the results. S.E., O.G. and A.J. contributed to the design and implementation of the outreach research. R.G., I.H. and M-.J.J. analysed data and contributed to the interpretation of the results. J.B., P.C. and B.V.D. analysed the dome rock and eruptive products and contributed to the interpretation of the results. R.S.J.S. contributed to the development of a working conceptual model of the volcano. All authors provided feedback and helped shape the research, analysis and manuscript.

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Joseph, E.P., Camejo-Harry, M., Christopher, T. et al. Responding to eruptive transitions during the 2020–2021 eruption of La Soufrière volcano, St. Vincent. Nat Commun 13 , 4129 (2022). https://doi.org/10.1038/s41467-022-31901-4

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DOI : https://doi.org/10.1038/s41467-022-31901-4

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Left:  Mt. Pinatubo eruption plume, July 1991, from Clark Air Base control tower.  Photo by J.N. Marso, U.S. Geological Survey.

The effects of several historic eruptions have been observed and the impacts of larger, prehistoric eruptions can be estimated.

Estimates of the fraction of sunlight transmitted through stratigraphic aerosols after major eruptions. Roza refers to a flood basalt eruption in the northwestern United States. Graph from Rampino and others (1988).

The pages in this section explore the following case studies for their impact on global climate

Impact of some major historic eruptions.

Data from Rampino and Self, 1984.

• Mt. Pinatubo, Philippines - 1991
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Case studies of past impacts and mitigation strategies for specific eruptions are given here. Sector specific information from these case studies also appear under their relevant topic headings (topics on the left).

Each case study begins with a brief overview discussing the size and volume of ash dispersed where known or approximated. Specific impact & mitigation information is organized into the following categories (where it is reported):

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Soufrière Hills Volcano, Montserrat, West Indies.

Soufrière Hills Volcano , Montserrat, West Indies. Synopsis of events by former Montserrat resident, photographer and Author Lally Brown. 

Where is Montserrat? Montserrat is a small tropical island of approximately 40 sq. miles in the Caribbean, fifteen minutes flying time from Antigua. It is a British Overseas Territory and relies on UK Government aid money to survive. It is of volcanic origin with the Soufrière Hills above the capital of Plymouth the highest point of the island.

How and when did the volcano erupt? Prior to 1995 the volcano in the Soufrière Hills had been dormant for 350 years but on the morning of 18th July 1995 steam and fine ash could be seen coming from the flanks of the Soufrière Hills accompanied by a roaring sound, described as being like a jet engine. In the capital of Plymouth there was a strong smell of ‘bad eggs’ the hydrogen sulphide being emitted by the awakening volcano.

Montserrat was totally unprepared. No-one had ever imagined the dormant volcano would erupt. The Soufrière Hills was the breadbasket of the island where farmers worked the fertile agricultural land, while the busy capital and island port of Plymouth nestled at the foot of the hills.

Scientists arrived from the University of the West Indies to assess the situation. They said the volcano was producing ‘acoustic energy explosions’ at approximately half-hour intervals sending ash and vapour three to four hundred metres into the air.

What happened next? Before July 1995 Montserrat was a thriving tourist destination with a population of 10,000 people but over several weeks there was a mass exodus from the island and a run on the banks with people withdrawing cash.

Several areas near the vent that had opened up in the hillside were declared exclusion zones and residents were evacuated to the safe north of the island into schools and churches.

It was evident the volcano was becoming more active when a series of small earthquakes shook the island. Heavy rain from passing hurricanes brought mudflows down the hillsides into Plymouth. Sulphide dioxide emissions increased, a sure sign of heightened activity.

The scientists hoped to be able to give a six hour warning of any eruptive activity but when they discovered the magma was less than 1 km below the dome they said this could not be guaranteed, saying there was a 50% chance of an imminent eruption. An emergency order was signed by the Governor and new exclusion zones were drawn with people evacuated north.

The years 1995 to 1997 The Soufrière Hills volcano became increasingly active and more dangerous.

Montserrat Volcano Observatory (MVO) was established to monitor activity and advise the Government.

December 1995 saw the first pyroclastic flow from the volcano.

The capital of Plymouth was evacuated for the last time in April 1996.

Acid rain damaged plants.

Two-thirds of Montserrat became the new exclusion zone , including the fertile agricultural land.

Population dropped to 4,000 with residents leaving for UK or other Caribbean islands.

Frequent heavy ashfalls covered the island with blankets of thick ash.

On the seismic drums at the MVO swarms of small hybrid earthquakes frequently registered. Also volcano-tectonic earthquakes (indicating fracture or slippage of rock) and ‘Broadband’ tremors (indicating movement of magma).

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MVO Seismograph printout Dec 1997

‘Spines’ grew rapidly out of the lava dome to heights of up to 15 metres before collapsing back.

Rainfall caused dangerous mudflows down the flanks of the Soufrière Hills.

Temporary accommodation was built to house evacuees living in churches and schools.

25th June 1997 Black Wednesday For a period of twenty minutes at 12.59 pm the volcano erupted without warning with devastating consequences. A massive pyroclastic flow swept across the landscape and boulders up to 4 metres in diameter were thrown out of the volcano. Over 4 sq.km was destroyed including nine villages and two churches. The top 300ft had been blown off the lava dome. Tragically nineteen people were caught in the pyroclastic flow and died.

Post Office and War Memorial 1997

Lateral blast December 1997 Midnight on Christmas Day 1997 the MVO reported that hybrid earthquakes had merged into a near-continuous signal clipping the sides of the seismic drum. At 3am on Boxing Day there was a massive collapse of the dome. Approximately 55 million cubic metres of dome material shot down the flanks of the volcano into the sea. Travelling at speeds of 250-300 km per hour it took less than a minute to slice a 7 km wide arc of devastation across southern Montserrat. The evacuated villages of Patrick’s and O’Garros were blasted out of existence. A delta 2 km wide spilled into the sea causing a small tsunami .

Police checkpoint Montserrat

March 1999 After a year of apparent inactivity at the volcano the Scientists declared the risk to populated areas had fallen to levels of other Caribbean islands with dormant volcanoes. Arrangements were made to encourage overseas residents to return. Plans were put in place to reopen the abandoned airport.

2000 to 2003 One year after the volcano had been declared dormant there was a massive collapse of the dome, blamed on heavy rainfall.

In July 2001 another massive collapse of the dome described as ‘a significant eruption’ caused airports on neighbouring Caribbean islands to close temporarily due to the heavy ashfall they experienced. A Maritime Exclusion Zone was introduced around Montserrat and access to Plymouth and the airport prohibited.

Soufrière Hills volcano was now described as a ‘persistently active volcano’ that could continue for 10, 20 or 30 years. (ie possibly to 2032).

In July 2003 ‘the worst eruption to date’ took place, starting at 8 pm 12th July and continuing without pause until 4 am morning of 13th July. Over 100 metres in height disappeared from the mountain overnight. It was the largest historical dome collapse since activity began in July 1995.

A period of relative quiet followed.

2006 The second largest dome collapse took place with an ash cloud reaching a record 55,000 metres into the air. Mudflows down the flanks of the Soufrière Hills was extensive and tsunamis were reported on the islands of Guadeloupe and Antigua.

Another period of relative quiet followed.

Soufriere Hills volcano 2007

2010 Another partial dome collapse with pyroclastic flows reaching 400 metres into the sea and burying the old abandoned airport. There was extensive ashfall on neighbouring islands.

Again followed by a period of relative quiet.

2018 Although the Soufrière Hills volcano is described as ‘active’ it is currently relatively quiet. It is closely monitored by a team at the Montserrat Volcano Observatory (MVO). They advise the Government and residents on the state of the volcano.

Negative effects of the volcano:

·       Approximately two-thirds of Montserrat now inaccessible (exclusion zone);

·       Capital of Plymouth including hospital, government buildings, businesses, schools etc. buried under ash;

·       Fertile farming land in the south in exclusion zone and buried under ash;

·       Population reduced from 10,000 to 4,000;

·       Businesses left Montserrat;

·       Tourism badly affected;

·       Concern over long term health problems due to ash;

·       Volcano Stress Syndrome diagnosed;

·       Huge financial cost to British Tax Payer (£400 million in aid);

·       Loss of houses, often not insured;

·       Relocation to the north of Montserrat by residents from the south.

Positive effects:

·       Tourists visiting Montserrat to see the volcano, MVO and Plymouth, now described as ‘Caribbean Pompeii’;

·       Geothermal energy being investigated;

·       Sand mining for export;

·       Plans for a new town and port in north;

·       New housing for displaced residents built;

·       New airport built (but can only accommodate small planes);

·       New Government Headquarters built;

·       Businesses opening up in the north of the island;

·       Ferry to Antigua operating.

Lally Brown

You can follow Lally Brown on Twitter.

If you are interested in reading a dramatic eyewitness account of life with this unpredictable and dangerous volcano then the book ‘THE VOLCANO , MONTSERRAT AND ME’ by Lally Brown is highly recommended. You can order a paper back or Kindle version on Amazon .

“As time moves on and memories fade, this unique, compelling book will serve as an important and accurate first-hand record of traumatic events, faithfully and sensitively recounted by Lally Brown.”

Prof. Willy Aspinall Cabot Professor in Natural Hazards and Risk Science, Bristol University.

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