First eruption since 1971 starts on 19 September; lava fountains, ash plumes, and lava flows

Multiple eruptions have occurred during the last 7,000 years at the Cumbra 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.

Figure 2. A 3D-rendering of the extent of lava flows from the Cumbra Vieja eruption on La Palma as of 15 October 2021 is shown in red with flows from earlier eruptions shown in tan. Data provided by Copernicus EMS and IGN, courtesy of INVOLCAN.

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.

Figure 3. Comparison of seismic event depth and locations at La Palma from swarms during 2017, 2018, and 24 July-2 August 2020. Courtesy of IGN (06-08-2020 16:45 UTC, Final de la actividad en La Palma).

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.

Figure 4. Seismic events at La Palma during 12-19 September 2021 showed distinct changes during those days. During 12-14 September (left) the seismicity migrated westward and was located at depths of about 7-13 km. The color scale on the left indicates the time of the events in hours before 0925 on 14 September, with red as the most recent. An abrupt increase in shallow seismicity on 19 September 2021 occurred a few hours before the eruption began, as shown by the bright orange dots in the right image. The color bar on the right represents the dates of the seismic events beginning on 11 September. Courtesy of IGN (left: 14-09-2021 09:30 UTC, right: 19-09-2021 11:00 UTC, Actualización de la información sobre la actividad volcánica en el sur de la isla de La Palma).

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).

Figure 5. INVOLCAN scientists observed seven active vents along the fissure at the start of the La Palma eruption at Cumbre Vieja on 19 September 2021. Photo by Alba, courtesy of INVOLCAN.

Figure 6. INVOLCAN scientists determined a flow rate for the new lava flows at La Palma on 19 September 2021 of 700 m/hour and a temperature of 1,075°C. Courtesy of INVOLCAN.

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 SO₂ 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).

Figure 7. Sulfur dioxide emissions from the Cumbre Vieja eruption at La Palma were measured by the TROPOMI Instrument on the Sentinel-5P satellite beginning on 19 September 2021 (left); they increased dramatically over the next several days. The plume was detected by satellite over 400 km SE over the western Sahara on the NW coast of Africa by 20 September. The plume was reported as visible at Gomera Island (80 km SE) on 21 September, having increased significantly in area and mass from the previous day. Courtesy of NASA Global Sulfur Dioxide Monitoring Page.

Figure 8. Sentinel-2 satellite images of La Palma show a sharp contrast from a cloudless sky before any signs of surface activity on 10 September 2021 (left) to dense cloud cover on the lower slopes of La Palma with a strong thermal anomaly from the new fissure vent and flows with rising steam plumes drifting NE on 20 September (right). Images use Atmospheric penetration rendering (bands 12, 11, 8a). Courtesy of Sentinel Hub Playground.

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 km² 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 km². 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).

Figure 9. The first map of the new lava flow at La Palma on 20 September 2021 was produced by the Copernicus Emergency Management Service (EMS) in partnership with IGN. It showed that the main channel of the lava flow shown in red had traveled more than 3 km W covering about 1 km2 and had destroyed an estimated 166 buildings. Courtesy of Copernicus EMS.

Figure 10. INVOLCAN scientists collected lava fragments from the Cumbre Vieja flow front at La Palma on 21 September 2021. The average flow thickness was 10-12 m. Courtesy of INVOLCAN.

Figure 11. Intense fountaining continued at the vent of the Cumbre Vieja eruption on La Palma during the night of 21 September 2021; multiple small flows descended the flanks of the growing pyroclastic cone. Courtesy of Cabildo La Palma.

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 SO₂ 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 km².

Figure 12. Ash emissions rose as high as 4.6 km altitude on 22 September 2021 at La Palma. Up to 3 cm of ashfall was reported downwind. Courtesy of El Periodico de Cataluny, S.L.U.

Figure 13. Slow moving lava flows at La Palma continued downslope from the vents on 22 and 23 September 2021. Many businesses and homes in the community of Todoque, shown here, were destroyed by the lava flows on 22 September. Photo by Bomberos de Canarias, courtesy of RTVE.

Figure 14 The original flow at La Palma as of 1913 on 20 September is shown in red. The progression of the lava flows each day from 20-23 September 2021 is shown in different colors. Lava flows covered almost 2 km2 of La Palma by the end of the day on 23 September 2021, and reports indicated 420 structures and 15.2 km of roads had been destroyed. The flow was about 3.8 km long and still 2.1 km from the coast. Courtesy of Copernicus EMS.

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.

Figure 15. Lava fountains several hundred meters high rose from the growing pyroclastic cone at La Palma in the early hours of 24 September 2021, seen from Tajuya. Dense ash emissions continued throughout the day. Photo by Tom Pfeiffer, courtesy of Volcano Discovery.

Figure 16. Ashfall in El Paso on La Palma covered cars and flowers on the morning of 25 September 2021. Ash emissions produced ashfall in numerous places around the island over the next several days. Courtesy of Volcanes de Canarias.

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 km² (figure 19).

Figure 17. A new vent opened on the lower W flank of the pyroclastic cone at La Palma on 25 September 2021. Courtesy of INVOLCAN.

Figure 18. Dense ash emissions on 25 September 2021 at La Palma forced closure of the island’s airport. Photo by Desiree Martin, AFT, courtesy of Corporación de Radio y Televisión Española (RTVE).

Figure 19. A large area of La Palma, shown in blue, was affected by ashfall to the W and SW of the erupting vent on 25 September 2021. The extent of the lava flow as of 1913 UTC on 20 September is shown in red, and the extent of the flow by 1206 on 25 September is shown in orange. Courtesy of Copernicus EMS.

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.

Figure 20. Jets of lava rose to nearly 1,000 m high at La Palma as seen from La Laguna on the evening of 26 September 2021. The lava flow remained active on the NW flank of the cone. Photo by Tom Pfeiffer, courtesy of Volcano Discovery.

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 m³. 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 km² 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.

Figure 21. The growth of the lava flow at La Palma during 20-27 September 2021 is shown in different colors. The flow as of 1913 on 20 September is shown in red. The extent of the flow as of 1206 on 25 September is shown in orange. The extent of the flow as of 1158 on 26 September is shown in blue, and the extent of the flow as of 0650 on 27 September is shown in green, nearly reaching Todoque Mountain by early on 27 September 2021. Reports indicated that 589 buildings and 21 km of roads had been destroyed from the 2.5 km2 of lava. Courtesy of Copernicus EMS.

Figure 22. A new flow appeared on the N flank of the cone at La Palma during the afternoon of 27 September 2021 from a reactivated vent; it traveled rapidly downslope reaching the center of Todoque. Photo by Tom Pfeiffer, courtesy of Volcano Discovery.

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 SO₂ cloud was clearly identifiable in satellite imagery in a 75 km radius around the island. In addition, satellite instruments measured very large plumes of SO₂ drifting hundreds of kilometers E, S, and N over the next several days (figure 24).

Figure 23. The new flow at La Palma moved through the upper outskirts of Todoque on 28 September 2021. Photo by Tom Pfeiffer, courtesy of Volcano Discovery.

Figure 24. The TROPOMI instrument on the Sentinel-5P satellite measured very large plumes of SO2 hundreds of kilometers E, S, and N of La Palma during 28, 29, and 30 September 2021. In addition, plumes of SO2 were visible in satellite imagery in a 75 km radius around the island. Courtesy of NASA Global Sulfur Dioxide Monitoring Page.

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 m³. 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).

Figure 25. A continuous cascade of lava fell over the cliff near El Guirre beach in Tazacorte at La Palma around midnight on 28-29 September 2021. Photo by Angel Medina/EFE, courtesy of RTVE.

Figure 26. By dawn on 29 September 2021 the delta was growing out from the cliff producing dense steam explosions where the lava entered the sea in Tazacorte, La Palma. Image taken from Tijarafe. Photo by Borja Suarez/Reuters, courtesy of RTVE.

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 km² by midday on 30 September (figure 29).

Figure 27. The lava flow at the La Palma eruption traveled downslope to the W between 25 (left) and 30 (right) September 2021. It reached the ocean and began building a delta into the sea late on 28 September. Image uses Atmospheric penetration rendering with bands 12, 11, and 8a. Courtesy of Sentinel Hub Playground.

Figure 28. Fresh pulses of lava flowed over earlier flows at La Palma on 30 September 2021. Photo by Tom Pfeiffer, courtesy of Volcano Discovery.

Figure 29. Continued mapping of the lava flow at La Palma indicated that by midday on 30 September 2021 it covered about 3.5 km2 and 870 buildings had been damaged or destroyed. The progress of the flow at different dates is shown in different colors. The status of the flow as of 1913 on 20 September is shown in red. The status as of 1206 on 26 September is shown in green. The status as of 1136 on 29 September is shown in orange, and the status as of 1217 on 30 September is shown in purple. Courtesy of Copernicus EMS.

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 m³.

Figure 30. Two new vents opened about 600 m NW of the base of the cone late on 30 September 2021. The new flows joined and headed W parallel to the main flow. Drone footage of the new vent was taken on 1 October by the Bristol Flight Lab, courtesy of INVOLCAN.

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).

Information is preliminary and subject to change. All times are local (unless otherwise noted)

October 1971 (CSLP 90-71)

Eruption produces lava fountains from three vents

Card 1305 (27 October 1971) Gas and tephra emission after several days of seismicity

The following cable was received from E.M. Fournier d'Albe on 27 October. "On 26 October after several days microseismic activity fissures opened in southern extremity Isla de La Palma Canaries with emission of gases and ejection rock fragments. No lava emission yet observed. Spanish Institute Geological Research sending team to observe eruption."

Card 1307 (28 October 1971) Three vents generated lava fountains and flows that reached the sea

The following cable was received from E.M. Fournier d'Albe on 28 October. "On 26 October 1640 GMT through the opened fissure mentioned in the previous report emission of gases and tephra started. Three main vents are working simultaneously. The vents evolved to lava fountains and formed two main lava flows which reached the sea at the southern tip of the island. Prof. Fuster and teams from Research Council of spain and University of Madrid and La Languna will arrive at La Palma 27 and 28 October."

Information Contacts:
Card 1305 (27 October 1971) Jose M. Fuster-Casas, University of Madrid, Spain; E.M. Fournier d'Albe, UNESCO, Paris, France.
Card 1307 (28 October 1971) Jose M. Fuster-Casas, University of Madrid, Spain; E.M. Fournier d'Albe, UNESCO, Paris, France.

November 1971 (CSLP 90-71)

Activity from six different vents through 18 November builds Teneguia cone

Card 1309 (02 November 1971) Northern vent builds spatter cone 180 m high

"...during 28 through 30 October only three vents were active. The fracture is 300 m long, its strike being 345 degrees. The northern vent throws lapilli and large bombs to a height of 500-700 m. It has a rhythm of 45 pulses per minute. This vent has built a spatter cone 180 m high and has spread a thin cover of lapilli over the area SE of the cone. The southern vent only throws bombs and scoriae. Lava is emitted through the upper vent and through a point in the middle of the fracture of the southern end of the island 2,500 m away from the vent. The flows from the central vent reached the sea forming a new platform. The lavas are alkaline basalts with hornblende phenocrysts. Casualties have happened but there is very little damage reported by Fuster."

Card 1310 (04 November 1971) Description of lava composition

The following cable from Professor Fuster was received on 4 November. "Teneguia volcano mineralogical lava composition 10 per cent of phenocrysts, including 5 DF augite 3 of basaltic hornblende of ore. Ninety per cent matrix containing mainly ore and augite and less abundant plagioclase microlites. Some samples have the same phenocrysts in a glassy matrix with plagioclase microlites."

Card 1311-1311a (04 November 1971) Eruptions and lava flows during 31 October-4 November

The following report was received through the courtesy of the Office of Naval Research, Washington, D.C., via Carl Hartdegen, Associate Director, Palisades Geophysical Institute, Sofar Station, Bermuda Island, who telephoned the Center and gave the following report radioed from the Hydrophone Station, La Palma, Canary Islands.

31 October. The activity of the fissure is located in two vents; the northern one, Teneguia One, is the most active erupting thick blocky lava flows which reached the sea to the E of the lighthouse of Fuencaliente. The emission of scoria bombs and lapillus is practically continous. The cinder and spatter cone that has been formed reaches 150 m and changes its form very quickly. The southern vent, Teneguia Two, emits only blocky lava flows which fall from the sea cliff to the sea. An exogenous dome is forming in this area, south of Teneguia One.

1 November. The activity of hot vents increases. Teneguia One emits a less viscous lava and the dome in the area of Teneguia Two also grows. At noon a new vent, Teneguia Three, opened 300 m to the north of Teneguia One. This vent erupts intermittently bombs and scoria bombs but no lava flow. During the afternoon in the Teneguia Two dome, multiple fissures began to appear and it started to collapse, fracture, and slumping slowly to the SE.

2 November. The activity of Teneguia One is similar to the previous days. Teneguia Three increases its activity during the morning, decreases the frequency and magnitude of the explosion in the afternoon. During the night it emits only gases. The dome of Teneguia Two has changed to a huge heap of lava block with secondary lava flows.

3 November. Teneguia Two emits very viscous lava flow and continues to emit bombs and lapillus relatively slowly 1-3 m/hour in the frontal part. Teneguia Three emits only some gases. Teneguia One also less active than yesterday. " The lava of the eruption is always anchibrolic trachy basalt and changes with time to a more vesicular type reported by Fuster-Casas."

The following report from Dr. Fuster-Casas was relayed to the Center by Leslie Schofield, Palisades Geophysical Institute, on 5 November.

4 November. The most important vent, Teneguia One, has emitted abundant lava flows that are always of block type. The flows have reached the seas to the E of the lighthouse. Aerial projections are less abundant than previous days. The other vents, Teneguia II and Teneguia III have been inactive and emitted only gases."

Card 1314-1314a (08 November 1971) Activity continues during 5-7 November; lava flows reach the sea

The following report was received through the courtesy of the Office of Naval Research, Washington, D.C.

5 November. Teneguia No. 1 has continued its activity of aerial projection and lava emission. A vertical crack has grown from the rim to the base of its cone. The cone has reached at this moment about 100 m from the surrounding plain. Teneguia No. 2 has had intermittent outbursts of aerial projection and during the night of 5-6 Nov. had enormous quantity of lava running in four lava flows from the western sea-cliff to the sea. Teneguia No. 3 has emitted only a little smoke and in an intermittent way.

6 November. During the early hours of this morning all the southern wall of the cone of the main vent, Teneguia No. 1, collapsed, and now the direction of the lava flows from this vent runs to the south towards Teneguia No. 2. At 1245 GMT all the materials of the former cones between Teneguia No. 1 and Teneguia No. 2 collapsed and a new cloud of pyrotechnic dust and gases at high temperatures ascended from this place falling over SW seaslope. This cloud ran also in NW direction along the western coast of island. During the afternoon and evening continous lava flows from Teneguia No. 1 and Teneguia No. 2 reached the sea on the SW coast.

7 November. The only change in the activity of Teneguia Volcano, that continues its aerial projections and outbursts of lava, is the apparition of fumaroles at crack in the western slopes of Teneguia No. 1 vent.

Card 1315 (10 November 1971) New vent opens on 9 November with strong bomb ejections

The following report was transmitted from Dr. Fuster-Casas.

8 November. The activity of Teneguia Volcano remains as during 7 November. Teneguia One vent emits abundant blocky lava which reaches the sea W of Fuencaliente lighthouse and projects continously lapilli and lava bombs. Teneguia Two and Three remain inactive. The fissures between Teneguia One and Three are growing steadily and new ones began to appear on the SW slope of the cone of Teneguia Three. The fissures emitt abundant white gases, rich in SO₂.

9 November. At 2200 last night a new vent, Teneguia Four, was opened in the N-S fissure located in the place where the fumaroles were stronger. The new vent consists of three openings that emit gases at great pressures and project lava bombs 100 to 150 m high. During the night the three openings have built a spatter cone 20 m high and changed into a double jet that ejects two columns of incandescent gases and pulverized lava at a great pressure. The double jet sounds like the engine of a jet plane taking off. The activity of fumarolic area is growing and Teneguia One remains as in former days. Teneguia Two and Three remain inactive."

Card 1316 (12 November 1971) Increased activity at all active centers

The following report from Dr. Fuster-Casas was telephoned to the Center by Kevin Laudadio.

10 November. Teneguia One emits more lapilli than preceding days. The lava flowing from its center is more viscous and flows very slowly, forming blocks 5 to 25 m long. The lapilli shower is more abundant in the north SW zone of the volcano.

Teneguia Four continues acting as a powerful jet engine expelling a moderate amount of lava lumps and lapilli; the spatter cone formed around the double vent coalesces with the N slope of Teneguia One cone.

At 0345Z a little vent was opened 75 m ENE of Teneguia IV vent in the fumarolic area located between Teneguia One and Teneguia Three cones. The white gases of the fumarole formed white sulfur deposits in the surrounding field.

The activity of fumarole increased until 2200 Z but afterwards production of gases was smaller.

In the last hours of the day activity of all active centers inreased: Teneguia One emits abundant fluid lava through five or more points in the N-S fissure. In the Teneguia Four NE zone, five little vents are acting in the same forrm and rhythm as Teneguia Four.

Card 1317-1317a (15 November 1971) Continued activity from six centers during 11-14 November

The following report from Dr. Fuster-Casas was received on 15 November.

11 November. Teneguia One was very active during all the day. The effusion of the fluid lava started last night changed to a more viscous lava early this morning. During all the day projected continously lava fragments up to 400 m high. Teneguia Four acted exactly like the previous day increasing its activity from 2240 Z on. The new vents opened have formed two small spatter cones in the N slope of Teneguia Five, which started with two openings ended with one. The other one, Teneguia Six, had a single opening. Both centers were very active, expelling a powerful jet of gas and fragments of lava and emitting two small lava flows in a northeasterly direction at 0700 Z. The fumarole field has the same intensity as the last hours of yesterday.

12 November. Teneguia One, Four, and Five are sending lava lumps, scoria and lapilli continously. Teneguia One produces pyroclastic material with about 20 pulses per minute. Teneguia Four and Five alternate in periods with pulsating emissions and periods of continuous jet emission, and periods of continous jet emission, jointed by big noise. The spatter cone of Teneguia Four and Five are growing continuously reaching 50 and 25 m respectively; they coalesce with Teneguia One cone which reaches about 110 m.

Teneguia Six spatter cone is being buried by Teneguia Five. The lapilli and scoria from the vents have changed to a more vitreous black and vesiculated-type which floats on the sea; there are some fragments of white pumice, perhaps formed by fussion of phonolitic rock of the substrata.

Teneguia One keeps the emission of viscous lava which reaches the sea on the W coast. Teneguia Five has produced some short flows.

13 November. In the morning Teneguia Four emitted abundant lava which reached the W coast in the afternoon. Meanwhile, Teneguia One increases its activity emitting more lava than usual; this lava flows to the W coast by four branches. The lava is more fluid and has some olivine phenyl crystals. The aerial projections are abundant in all active vents, Teneguia Four, Five, and Six. After 2000 Z the emission of lava is less abundant.

14 November. The intensity of the eruption was less strong than yesterday. Teneguia One emits lava, lapilli and bombs. Teneguia Four, Five and Six emit only lapilli and some bombs and scoria."

Card 1318-1318a (19 November 1971) Complex cone growth and collapses during intense activity

The following report from Dr. Fuster-Casas was received on 19 November.

15 November. The activity of the volcano increased during the morning but maintained the same characteristics as the previous day. Teneguia One vents were pouring lava flows in an intermittent way. Teneguia Four and Five alternate the projection of jets of gases with the emission of clouds of lapilli. After a period of being practically inactive, at 1245 Z that lasted about half an hour, the Teneguia Five erupted a big lava flow that nearly reached the road to the lighthouse of Fuencaliente in a southeasterly direction. During the afternoon Teneguia One and Teneguia Four were increasing their activity with continuous projection of scoria and bombs that continued until midnight. The scoria and cinder cones of Teneguia One, Four, Five, and Six coalesced. The height is 125 m on the previous ground.

16 November. The activity of the several craters was intense. Teneguia One continues pouring blocky lava in six flows which increase in velocity in the scarp, adjoining the W coast where the lava is forming six blocky deposits. Teneguia Four is as active as Teneguia One, forming an elongated crater with at least four projection points--a line in a NW direction. Teneguia Six is acting in the same way with three or four projection points--a line in a NNE trend--and was pouring lava from their bases.

Teneguia Five was less active. Between Teneguia Four and Teneguia Five there are two little openings which emit continous bright flames and a few lava blocks. Teneguia One and Four send intermittently big columns of scoria and lapilli which cover the previous lava flows and the surroundings especially in the SE direction. Teneguia Six projects mainly scoria and lava lumps. The lava is changing to a more olivine type.

17 November. During the night of the 16th to the 17th the cone of Teneguia Four has grown steadily and buried the vents of Teneguia Five and Teneguia Six. A new opening was formed just under the NE rim of this crater. The whole day both Teneguia One and Four have continued emission of aerial projections with enormous amounts of lapilli and lava flows, the former one in a more intermittent and less powerful way. The lava from Teneguia Four is forming an intense platform at the foot of the W sea cliff that penetrates into the sea. During the afternoon a part of the N rim of the Teneguia Four vent collapsed under its own weight and its incandescent materials originated a big secondary flow of semi-fluid scoria and lava that filled the area between the main volcano and the little cone of Teneguia Three.

18 November. At 0130 Z Teneguia six started to produce fluid lava flows from an opening at the cone base. Teneguia Four decreased its lava emission. Teneguia One, Four and Six project simultaneously scoria, lapilli, and lava lumps; Teneguia One and Six with pulses, Teneguia Four continuously. Until noon Teneguia Six had periods of fast production of lava flows and periods of attenuated activity; until midnight only activity was emission of moderate amounts of gas from the vents. Seismic agitation stopped at the same time as the volcanic activity.

Information Contacts:
Card 1309 (02 November 1971) Jose M. Fuster-Casas, Instituto Lucas Mallada, Madrid, Spain; Sr. Firmado, special delegate of the government of the Canary Islands.
Card 1310 (04 November 1971) Jose M. Fuster-Casas, Instituto Lucas Mallada, Madrid, Spain.
Card 1311-1311a (04 November 1971) Jose M. Fuster-Casas, Instituto Lucas Mallada, Madrid, Spain; Palisades Hydrophone Station, La Palma Island, Canary Islands, Spain; Carl Hartdegen, Palisades Geophysical Institute Sofar Station, Bermuda.
Card 1314-1314a (08 November 1971) Jose M. Fuster-Casas, Instituto Lucas Mallada, Madrid, Spain; Palisades Hydrophone Station, La Palma Island, Canary Islands, Spain; Kevin Laudadio, Palisades Geophysical Institute Sofar Station, Bermuda.
Card 1315 (10 November 1971) Jose M. Fuster-Casas, Instituto Lucas Mallada, Madrid, Spain; Palisades Hydrophone Station, La Palma Island, Canary Islands, Spain; Kevin Laudadio, Palisades Geophysical Institute Sofar Station, Bermuda.
Card 1316 (12 November 1971) Jose M. Fuster-Casas, Instituto Lucas Mallada, Madrid, Spain; Palisades Hydrophone Station, La Palma Island, Canary Islands, Spain; Kevin Laudadio, Palisades Geophysical Institute Sofar Station, Bermuda.
Card 1317-1317a (15 November 1971) Jose M. Fuster-Casas, Instituto Lucas Mallada, Madrid, Spain; Palisades Hydrophone Station, La Palma Island, Canary Islands, Spain; Kevin Laudadio, Palisades Geophysical Institute Sofar Station, Bermuda.
Card 1318-1318a (19 November 1971) Jose M. Fuster-Casas, Instituto Lucas Mallada, Madrid, Spain; Palisades Hydrophone Station, La Palma Island, Canary Islands, Spain; Kevin Laudadio, Palisades Geophysical Institute Sofar Station, Bermuda.

June 1996 (BGVN 21:06) Cite this Report

No surface deformation detected

A March 1996 EDM survey of the active Cumbre Vieja rift volcano indicated no significant surface deformation since installation of the network in October 1994. The network contains 11 benchmarks (incorporating two Spanish survey triangulation pillars) and was measured using the infrared EDM method. Together with one 3-component seismic station NE of the main rift, the network provides the only current means of monitoring activity on the island.

The deformation network covers the area affected by faulting associated with the July 1949 eruption (figure 1), a zone where W-facing normal faults showed a maximum vertical displacement of ~4 m. The Cumbre Vieja ridge lies between the two 1949 eruptive centers (Duraznero and San Juan). Eyewitness accounts (Bonnelli, 1950) and detailed mapping of the eruptive products showed that during the 1949 eruption, fault displacements also had westward components with downslope movement on the volcano's flanks. La Palma is comparable in form and structure to other Canary Islands that have undergone large-scale slope failure. Steep topography, together with the prospect of a future magma intrusion, cause concern for the long-term stability of the Cumbre Vieja ridge.

Figure 1. Sketch map of the Cumbre Vieja rift volcano showing the distribution of benchmarks, vents, and faults associated with the July 1949 eruption at La Palma. Courtesy of J.L. Moss and W.J. McGuire.

The wedge-shaped island of La Palma contains two large volcanic centers. The northern one is cut by the massive Caldera Taburiente. The southern Cumbre Vieja rift volcano, oriented N-S, has been the site of historical eruptions recorded since the 15th century. An eruption from the S tip of La Palma in 1971 produced the Teneguia cinder cone. Fissure-fed eruptions from vents ~1 km S of the 1677 San Antonio cone produced lava flows that reached the SW coast.

Reference. Bonnelli, R., 1950, Contribucion al estudio de la erupcion del volcan del Nambroque o San Juan (Isla de la Palma), 24 de Junio - Agosto de 1949: Instituto Geografico y Catastral, Madrid, Spain.

Information Contacts: J.L. Moss, W.J. McGuire, and S.J. Day, Center for Volcanic Research, Cheltenham & Gloucester College, Francis Close Hall, Swindon Road, Cheltenham GL50 4AZ, United Kingdom; S.J. Saunders, Brunel University, Department of Geography & Earth Science, Borough Road, Isleworth, Middlesex TW7 5DU, United Kingdom; J-C. Carracedo, Estacion Volcanologica de las Canarias, Tigua Carretera de la Esperanza 3, Apartado de Correos 195, 38206 La Laguna, Tenerife, Canary Islands, Spain.

October 2021 (BGVN 46:10) Cite this Report

First eruption since 1971 starts on 19 September; lava fountains, ash plumes, and lava flows

Multiple eruptions have occurred during the last 7,000 years at the Cumbra 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.

Figure 2. A 3D-rendering of the extent of lava flows from the Cumbra Vieja eruption on La Palma as of 15 October 2021 is shown in red with flows from earlier eruptions shown in tan. Data provided by Copernicus EMS and IGN, courtesy of INVOLCAN.

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.

Figure 3. Comparison of seismic event depth and locations at La Palma from swarms during 2017, 2018, and 24 July-2 August 2020. Courtesy of IGN (06-08-2020 16:45 UTC, Final de la actividad en La Palma).

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.

Figure 4. Seismic events at La Palma during 12-19 September 2021 showed distinct changes during those days. During 12-14 September (left) the seismicity migrated westward and was located at depths of about 7-13 km. The color scale on the left indicates the time of the events in hours before 0925 on 14 September, with red as the most recent. An abrupt increase in shallow seismicity on 19 September 2021 occurred a few hours before the eruption began, as shown by the bright orange dots in the right image. The color bar on the right represents the dates of the seismic events beginning on 11 September. Courtesy of IGN (left: 14-09-2021 09:30 UTC, right: 19-09-2021 11:00 UTC, Actualización de la información sobre la actividad volcánica en el sur de la isla de La Palma).

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).

Figure 5. INVOLCAN scientists observed seven active vents along the fissure at the start of the La Palma eruption at Cumbre Vieja on 19 September 2021. Photo by Alba, courtesy of INVOLCAN.

Figure 6. INVOLCAN scientists determined a flow rate for the new lava flows at La Palma on 19 September 2021 of 700 m/hour and a temperature of 1,075°C. Courtesy of INVOLCAN.

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 SO₂ 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).

Figure 7. Sulfur dioxide emissions from the Cumbre Vieja eruption at La Palma were measured by the TROPOMI Instrument on the Sentinel-5P satellite beginning on 19 September 2021 (left); they increased dramatically over the next several days. The plume was detected by satellite over 400 km SE over the western Sahara on the NW coast of Africa by 20 September. The plume was reported as visible at Gomera Island (80 km SE) on 21 September, having increased significantly in area and mass from the previous day. Courtesy of NASA Global Sulfur Dioxide Monitoring Page.

Figure 8. Sentinel-2 satellite images of La Palma show a sharp contrast from a cloudless sky before any signs of surface activity on 10 September 2021 (left) to dense cloud cover on the lower slopes of La Palma with a strong thermal anomaly from the new fissure vent and flows with rising steam plumes drifting NE on 20 September (right). Images use Atmospheric penetration rendering (bands 12, 11, 8a). Courtesy of Sentinel Hub Playground.

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 km² 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 km². 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).

Figure 9. The first map of the new lava flow at La Palma on 20 September 2021 was produced by the Copernicus Emergency Management Service (EMS) in partnership with IGN. It showed that the main channel of the lava flow shown in red had traveled more than 3 km W covering about 1 km2 and had destroyed an estimated 166 buildings. Courtesy of Copernicus EMS.

Figure 10. INVOLCAN scientists collected lava fragments from the Cumbre Vieja flow front at La Palma on 21 September 2021. The average flow thickness was 10-12 m. Courtesy of INVOLCAN.

Figure 11. Intense fountaining continued at the vent of the Cumbre Vieja eruption on La Palma during the night of 21 September 2021; multiple small flows descended the flanks of the growing pyroclastic cone. Courtesy of Cabildo La Palma.

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 SO₂ 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 km².

Figure 12. Ash emissions rose as high as 4.6 km altitude on 22 September 2021 at La Palma. Up to 3 cm of ashfall was reported downwind. Courtesy of El Periodico de Cataluny, S.L.U.

Figure 13. Slow moving lava flows at La Palma continued downslope from the vents on 22 and 23 September 2021. Many businesses and homes in the community of Todoque, shown here, were destroyed by the lava flows on 22 September. Photo by Bomberos de Canarias, courtesy of RTVE.

Figure 14 The original flow at La Palma as of 1913 on 20 September is shown in red. The progression of the lava flows each day from 20-23 September 2021 is shown in different colors. Lava flows covered almost 2 km2 of La Palma by the end of the day on 23 September 2021, and reports indicated 420 structures and 15.2 km of roads had been destroyed. The flow was about 3.8 km long and still 2.1 km from the coast. Courtesy of Copernicus EMS.

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.

Figure 15. Lava fountains several hundred meters high rose from the growing pyroclastic cone at La Palma in the early hours of 24 September 2021, seen from Tajuya. Dense ash emissions continued throughout the day. Photo by Tom Pfeiffer, courtesy of Volcano Discovery.

Figure 16. Ashfall in El Paso on La Palma covered cars and flowers on the morning of 25 September 2021. Ash emissions produced ashfall in numerous places around the island over the next several days. Courtesy of Volcanes de Canarias.

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 km² (figure 19).

Figure 17. A new vent opened on the lower W flank of the pyroclastic cone at La Palma on 25 September 2021. Courtesy of INVOLCAN.

Figure 18. Dense ash emissions on 25 September 2021 at La Palma forced closure of the island’s airport. Photo by Desiree Martin, AFT, courtesy of Corporación de Radio y Televisión Española (RTVE).

Figure 19. A large area of La Palma, shown in blue, was affected by ashfall to the W and SW of the erupting vent on 25 September 2021. The extent of the lava flow as of 1913 UTC on 20 September is shown in red, and the extent of the flow by 1206 on 25 September is shown in orange. Courtesy of Copernicus EMS.

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.

Figure 20. Jets of lava rose to nearly 1,000 m high at La Palma as seen from La Laguna on the evening of 26 September 2021. The lava flow remained active on the NW flank of the cone. Photo by Tom Pfeiffer, courtesy of Volcano Discovery.

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 m³. 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 km² 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.

Figure 21. The growth of the lava flow at La Palma during 20-27 September 2021 is shown in different colors. The flow as of 1913 on 20 September is shown in red. The extent of the flow as of 1206 on 25 September is shown in orange. The extent of the flow as of 1158 on 26 September is shown in blue, and the extent of the flow as of 0650 on 27 September is shown in green, nearly reaching Todoque Mountain by early on 27 September 2021. Reports indicated that 589 buildings and 21 km of roads had been destroyed from the 2.5 km2 of lava. Courtesy of Copernicus EMS.

Figure 22. A new flow appeared on the N flank of the cone at La Palma during the afternoon of 27 September 2021 from a reactivated vent; it traveled rapidly downslope reaching the center of Todoque. Photo by Tom Pfeiffer, courtesy of Volcano Discovery.

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 SO₂ cloud was clearly identifiable in satellite imagery in a 75 km radius around the island. In addition, satellite instruments measured very large plumes of SO₂ drifting hundreds of kilometers E, S, and N over the next several days (figure 24).

Figure 23. The new flow at La Palma moved through the upper outskirts of Todoque on 28 September 2021. Photo by Tom Pfeiffer, courtesy of Volcano Discovery.

Figure 24. The TROPOMI instrument on the Sentinel-5P satellite measured very large plumes of SO2 hundreds of kilometers E, S, and N of La Palma during 28, 29, and 30 September 2021. In addition, plumes of SO2 were visible in satellite imagery in a 75 km radius around the island. Courtesy of NASA Global Sulfur Dioxide Monitoring Page.

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 m³. 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).

Figure 25. A continuous cascade of lava fell over the cliff near El Guirre beach in Tazacorte at La Palma around midnight on 28-29 September 2021. Photo by Angel Medina/EFE, courtesy of RTVE.

Figure 26. By dawn on 29 September 2021 the delta was growing out from the cliff producing dense steam explosions where the lava entered the sea in Tazacorte, La Palma. Image taken from Tijarafe. Photo by Borja Suarez/Reuters, courtesy of RTVE.

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 km² by midday on 30 September (figure 29).

Figure 27. The lava flow at the La Palma eruption traveled downslope to the W between 25 (left) and 30 (right) September 2021. It reached the ocean and began building a delta into the sea late on 28 September. Image uses Atmospheric penetration rendering with bands 12, 11, and 8a. Courtesy of Sentinel Hub Playground.

Figure 28. Fresh pulses of lava flowed over earlier flows at La Palma on 30 September 2021. Photo by Tom Pfeiffer, courtesy of Volcano Discovery.

Figure 29. Continued mapping of the lava flow at La Palma indicated that by midday on 30 September 2021 it covered about 3.5 km2 and 870 buildings had been damaged or destroyed. The progress of the flow at different dates is shown in different colors. The status of the flow as of 1913 on 20 September is shown in red. The status as of 1206 on 26 September is shown in green. The status as of 1136 on 29 September is shown in orange, and the status as of 1217 on 30 September is shown in purple. Courtesy of Copernicus EMS.

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 m³.

Figure 30. Two new vents opened about 600 m NW of the base of the cone late on 30 September 2021. The new flows joined and headed W parallel to the main flow. Drone footage of the new vent was taken on 1 October by the Bristol Flight Lab, courtesy of INVOLCAN.

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).