Daily updates from the Tajogaite 2021 eruption

Today, a cluster of 11 earthquakes at 9-14 km were recorded in the south of La Palma close to the Cumbre Vieja ridge, starting at 3:18 am local time. The largest event so far was a mbLg 1.5 earthquake and 11 km depth. This new seismic swarm is the first that has been detected since earthquake swarms in June and January 2021, which were largely clustered in similar areas but at depths deeper than 20 km. The swarm represents the 9th seismic swarm in southern La Palma since anomalous seismic activity began in the area in October 2017, which is thought to be related to magmatic reactivation of Cumbre Vieja. The shallow depth of these latest earthquakes, as well as the consistent locations with other swarms, are the most significant features, although the timescales nor the potential occurrence of any magmatic reactivation cannot be determined in the short-medium term.

The new earthquake swarm on the south of La Palma has continued and today significantly intensified, both in the frequency and magnitude of the earthquakes. There were 208 earthquakes from 7-18 km depths, with the vast majority between 9-12 km depth. The largest event so far was a mbLg 3.4 earthquake and 9 km depth. This new seismic swarm is the first that has been detected since earthquake swarms in June and January 2021, which were largely clustered in similar areas but at depths deeper than 20 km. The swarm represents the 9th seismic swarm in southern La Palma since anomalous seismic activity began in the area in October 2017, which is thought to be related to magmatic reactivation of Cumbre Vieja. The shallow depth of these latest earthquakes as well as the increasing intensities are the most important aspects of this swarm thus far. Although the possibility or timescales of magmatic reactivation cannot be predicted, the likelihood of changes would increase if the swarm became shallower and more intense. Nonetheless, previous eruptions in the Canary Islands, including the 2011 El Hierro eruption were preceded by lengthy periods of strong seismicity at similar depths.

Today, in the wake of the intensifying seismic swarm on La Palma that began on the 11th September, the Government of the Canary Islands have activated the Scientific Committee of the Special Plan for Civil Protection and Attention to Emergencies due to Volcanic Risk (PEVOLCA). Alongside this activation, the volcanic traffic light alert system has been raised from green to yellow in the municipalities of Fuencaliente, Los Llanos de Aridane, El Paso and Mazo. The yellow traffic light allows for an intensification of communication to the population, volcano and seismic monitoring, as well as increased surveillance.

Today, a cluster of 11 earthquakes at 9-14 km were recorded in the south of La Palma close to the Cumbre Vieja ridge, starting at 3:18 am local time. The largest event so far was a mbLg 1.5 earthquake and 11 km depth. This new seismic swarm is the first that has been detected since earthquake swarms in June and January 2021, which were largely clustered in similar areas but at depths deeper than 20 km. The swarm represents the 9th seismic swarm in southern La Palma since anomalous seismic activity began in the area in October 2017, which is thought to be related to magmatic reactivation of Cumbre Vieja. The shallow depth of these latest earthquakes, as well as the consistent locations with other swarms, are the most significant features, although the timescales nor the potential occurrence of any magmatic reactivation cannot be determined in the short-medium term.

As the seismic swarm continues to intensify, PEVOLCA maintains the yellow traffic light in the municipalities of El Paso, Los Llanos de Aridane, Mazo and Fuencaliente, although comments that there is still no evidence of an imminent eruption. Over the last couple of days, the seismicity has become displaced to the northwest relative to the focus at the beginning of the swarm, and the average depth has decreased and is now between 6-8 km. Additionally, today some lower magnitude earthquakes have been detected much nearer the surface (1-3 km).

Miguel Ángel Morcuende, head of the Environment and Emergencies service of the Government of La Palma, has been appointed technical director of PEVOLCA and will be responsible for directing and coordinating all actions carried out under the Plan itself. To meet the telecommunications demands that an emergency could bring, the government has decided to upgrade the existing Canary Islands Emergency and Security Network (RESCAN).

Today, a cluster of 11 earthquakes at 9-14 km were recorded in the south of La Palma close to the Cumbre Vieja ridge, starting at 3:18 am local time. The largest event so far was a mbLg 1.5 earthquake and 11 km depth. This new seismic swarm is the first that has been detected since earthquake swarms in June and January 2021, which were largely clustered in similar areas but at depths deeper than 20 km. The swarm represents the 9th seismic swarm in southern La Palma since anomalous seismic activity began in the area in October 2017, which is thought to be related to magmatic reactivation of Cumbre Vieja. The shallow depth of these latest earthquakes, as well as the consistent locations with other swarms, are the most significant features, although the timescales nor the potential occurrence of any magmatic reactivation cannot be determined in the short-medium term.

A PEVOLCA meeting today chaired by Justice, Security and Public Administrations Minister Julio Pérez on the evolution of the seismic activity on La Palma covered among other things advancing actions for a possible future evacuation of the population in the affected municipalities of Fuencaliente, Los Llanos de Aridane, El Paso and Villa de Mazo. The Cabildo de La Palma, who were in attendance, have activated their island-wide PEINPAL Emergency Plan as a preventative measure. Furthermore, an observation flight over La Palma has been coordinated for the monitoring of the ongoing activity. As well as the island-wide emergency plans, the town councils of the affected municipalities (Fuencaliente, Los Llanos de Aridane, El Paso and Villa de Mazo) have also activated their local emergency plans.

At 15:12 local time, a basaltic fissure eruption began, with the coordinates of the first emission point being 28º36’N, 17º52’W. The eruption has shown phreatomagmatic pulses, especially during the first few hours, characterised by ash-and-steam-rich plumes, which reached heights of 1500-3000 m, although predominantly shows a typical strombolian mechanism. Initial estimates indicate the SO2 emissions from the activity could be between 6,000-9,000 tons per day.

The new eruption continues with strombolian activity and lava flows being produced from 4 vents along an eruptive fissure, although a principal cone has been formed. The opening of new vents cannot be ruled out, with the final active vent opening at 7:56 pm local time and showing a more effusive character. The lava flows have reached halfway to the sea, although the flow fronts have slowed markedly relative to their initial velocity. Latest estimates give a velocity of 200 metres per hour, and they are expected to reach the town of Todoque within the next couple of days. However, it is uncertain when the flows will reach the sea, although the maritime authorities have extended the oceanic exclusion zone to two nautical miles, for security as well as safety reasons. The exclusion zone has also been extended to include Tacande in the municipality of El Paso as a new eruptive vent 900 metres from the main one has opened, forcing the evacuation of more people, moving the total number of evacuees to approximately 5,500. As well as people, a priority of the authorities is to transfer livestock out of the path of the eruption, including 400 goats in addition to pigs and cattle so far.

As the eruption enters its third day, no casualties or personal injuries from the eruption continue to be reported. However, the first provisional damage assessment has been published which estimates that 185 buildings have been affected, 63 of which are homes according to the Land Registry. The lava flow now has two fronts; a northern front which is closer to Todoque, and a southern front which is largely stopped for the moment. The advance of the active flow front is slowing relative to previous days, however.

Due to cooling and the infilling of topographic lows, the lava flow fronts have slowed significantly, and now advance at around 4 metres per hour. The total area affected by the lava flow stands at 140 hectares, with the flow fronts measuring 600 metres across. The episode of increased explosiveness that began at 7pm local time on the 21st ended at 2am local time and coincided with a small collapse of a portion of the cone. Strombolian activity continues producing both ash and lava flows from multiple vents in the vicinity of a principal cone that has formed around the most active vents. In the current state, up to 9 vents along one fissure have been observed by the authorities, although on average only 4 of these are active at any one time. This activity is emitting over 12,000 tons of SO2 per day up to 3000 m, although the amount of SO2 released per day is thought to be an underestimate according to PEVOLCA, as such ground-based measurements cannot be used to observe the full extent of the plume, unlike satellite observations.

The two lava flow fronts, one to the north and one to the south, continue to advance slowly. The maximum length of the flow is now 3,800 m, with 2,100 m to go to reach the sea, and the flows now cover 220 hectares in total. The northern front moves at approximately 1 m per hour and is up to 12 m thick, whereas the southern front moves faster, at 4-5 m per hour. Current estimates of damage include about 300 homes already affected by the lava flows. The eruptive activity continues to show a strombolian mechanism, although with a more explosive and ash-rich behaviour. This more energetic activity is mirrored in the plume height, which is measured at around 4,500 m compared to 3,000 m on previous days, and the SO2 emissions, which are estimated at over 12,000 tons per day. Changes in the wind direction and increased height of the plume have led to the dispersal of ash eastwards towards Santa Cruz de La Palma and La Palma airport, causing disruption to its operations for the first time since the eruption began.

An increase in explosive activity throughout the day, to the most energetic levels seen since the eruption began, has prompted the evacuation of a further 160 people to the northwest of the volcano, in Tajuya, Tacande de Abajo and those not already evacuated in Tacande de Arriba. The decision was made because of the increased risk of volcanic materials and pressure waves reaching and causing damage in areas outside of the current exclusion zone. In particular, this related to the opening of two new effusive vents as well as a fracture in the NW flank of the main cone, which could destabilise the cone and increase the risk of a sector collapse. The two new effusive vents emit fluid lava flows, that travel faster than previous flows but flow over the top of previous flows. In total, the number of evacuees has now reached 6,000. Latest estimates of damage indicate up to 400 buildings affected by the lava flows.

Given the evolution of the eruptive activity over the last 24 hours, it was decided by PEVOLCA to maintain the latest evacuation order given on the 24th. The two effusive vents that opened on the 24th on the side of the cone showing effusive (Hawaiian) behaviour and emitting lava flows have merged into one vent, exhibiting the same behaviour. The lava flow from this merged vent is fluid but has slowed, from about 80 m per hour in the night of the 24th/25th to 40 m per hour by the afternoon of the 25th. So far, it has travelled approximately 3.6 km on top of previous flows. The older flows are still active, although the front is only advancing incrementally currently. The explosivity of the strombolian activity from the main cone has decreased slightly since the afternoon of the 24th where the highest peak in the eruptive intensity so far was recorded. The activity is concentrated in the main cone through at least three strombolian vents, in addition to a new Hawaiian vent at the base of the NW sector of the main cone. Furthermore, a small rupture in the southern side of the main cone overnight noticeably altered its summit morphology.

Based on the evolution of the eruption, the 160 residents evacuated from Tajuya and Tacande on the 24th can return to their homes. According to Maria Jose Blanco, this has been allowed by the lack of the instability seen in the cone on the 24th, as well as the relative stability of eruption parameters such as tremor which was elevated and unstable at the time the evacuation was first ordered. The eruption continues to show both Strombolian activity from 3 or more vents in the main cone, as well as more effusive Hawaiian activity from the vent at the base of the NW sector of the main cone. The lava from this effusive vent continues to feed two active lava flows; a southern flow at travelling at approximately 30 m per hour; and a more fluid flow to the north which has sped up and is travelling at around 100 m per hour and is expected to overrun the front of the older stalled lava flow front to the north according to modelling carried out by the authorities. At 8:15pm, the latter flow reached Todoque mountain, about 1,600 m from the coast.

The eruption has seen a large variation of activity, with increases and decreases in the intensity of Strombolian activity, as well as pulses of phreatomagmatic activity (characterised by white plumes rich in water vapour) and periods of no strombolian activity from the main cone. The first period of cessation was between 4:10-4:30 am local time, and similar activity with occasional weak ash-rich explosions was seen throughout much of the day. These cessations were accompanied with greatly reduced volcanic tremor values, and have been attributed to a temporary plugging of the conduit. From approximately 6:30 pm local time, continuous strombolian activity returned to the vents in the main cone and increased in intensity throughout the evening, accompanied with a sharp increase in volcanic tremor. The lava flows continue to advance and are located between 800-1000 m from the coast, although the northern lava flow front which reached Todoque mountain on the 26th has greatly slowed. Nonetheless, due to the potential hazards from explosions and noxious clouds of vapour when the lava contacts the sea, preventative confinement measures have been put in place for 300 people in the coastal areas of Tazacorte.

The lava flow began the day approximately 1000 m from the coast, although it advanced quickly throughout the day due to the large volume of fluid lava being emitted from the effusive vent on the northwest sector of the cone. The lava flow crossed to the south of Todoque mountain and reached the sea at 11:00 pm local time after cascading down the cliffs at Playa de Los Guirres. Due to the clouds of vapour being produced by the contact of the lava with the sea, which could contain high concentrations of gases such as hydrogen chloride (HCl), the confinement order in Tazacorte remains in place. Throughout the day, there were also issues with suspended particles in the air, both directly from the volcano and from the burning of plastic and other noxious materials in greenhouses and agricultural buildings by the lava flows. This problem was exacerbated by a low temperature inversion at 600 m preventing the dispersal of these particles in the evening. This led to the exceedance of the PM10 particle air quality threshold level (50 μg/m3) in Los Llanos de Aridane.

The active lava flow continues cascade down the cliffs of Playa de Los Guirres to the sea, where a lava delta (also called by the Canarianism “fajana”) is being created. The contact of the lava and seawater are creating gases of vapour, although currently due to the prevailing winds these have not spread laterally and are concentrated in a small area around the lava delta. Nonetheless, the confinement order remains in place for neighbourhoods in Tazacorte for the moment. The rest of the lava flows remain practically inactive, and new damage estimates 476 hectares have been covered by the lava flows, and 744 buildings have been damaged or destroyed according to the Copernicus Satellite. Regarding surface activity, strombolian activity continues with pulses of increased and decreased intensity, as well as an effusive focus from the vent on the NW sector of the main cone. Ash concentrations are higher than previous days in the Aridane Valley, so the population are reminded to wear FFP2 or better facemasks when outside and take extra caution. Irrigators and evacuated residents outside the exclusion zone have been allowed in to tend to their crops and remove their belongings, and have been accompanied by UME and the Civil Guard who can monitor gas concentrations in real time.

The lava delta continues to be fed by the active lava flows, which show some stability in that they are largely confined to within previous lava flows. However, there are also localised breakouts onto previously unaffected land. The lava delta has reached a thickness of 24 m and is now beginning to spread laterally. Surface activity at the main cone continues to show a mixed mechanism with strombolian activity from multiple vents in the main cone, and more effusive Hawaiian activity from a vent at the base of the NW sector on the main cone, with occasional phreatomagmatic pulses too. Throughout the morning of the 30th, an extensive fumarole field developed on the NE flank of the main cone. The continued presence of a thermal inversion is hampering the dispersal of volcanic gases and ash, leading to a decrease in air quality in the Aridane Valley. SO2 concentrations in Tazacorte peaked at ‘very high’ levels (>500 μg/m3) at 8:00 am local time and increases in SO2 concentrations have also been observed in Los Llanos de Aridane, along with reports of a ‘rotten egg’ smell, although these values do not currently represent a health hazard.