La Palma's Cumbre Vieja volcano eruption of 2021
October 2
Two weeks after it first erupted on September 19th, the Cumbre Vieja volcano on La Palma continues to erupt at impressive intensity. The lava output rate remains very high and volcanic tremor is stable at high levels. Over 80 million m³ of lava have been emplaced so far, much more than originally estimated the eruption would be able to produce, likely due to the continued magma supply from a deeper source. The north-western summit vent started an impressive show of violent, near vertical fountaining reaching 300-500 m height. The new lava flow just below the north-western base of the cone make their way through untouched land north of the existing flow field, forming an impressive channel of approximately 50 m wide that is destroying additional buildings. 8 vents are producing several lava flows, some of which going directly into lava tubes, others overlapping older flows or feeding lava channels. Some of the lava still finds its way to the sea entry, where it has won 28 ha over the sea.
The quake activity is quite intense, 26 quakes of magnitudes 3.0-3.7 have been recorded in the last 48 hours, located mostly at 10-15 km depth beneath the centre of Cumbre Vieja, the same place as the seismic swarm that preceded the eruption. This is the area between the upper mantle and crust of the island, where magma from the deeper source intrudes into the volcanic edifice. The quakes seem to remain stationary in this area, possibly because the new intrusions are able to use the existing pathways of magma through the island edifice. If there is a continuous supply from the mantle source, the eruption could last for much longer than expected.
October 8
Up until October 8, the activity continued with no significant changes as the eruption approaches 3 weeks, during which it has covered more than 430 hectares of land and destroyed over 1,000 houses. The next day however, the eruption has been becoming stronger, with pressure increasing in the main cone. Strong ground vibrations from sustained, near-constant explosions can be felt in nearby areas. At the vents, ash-rich fountaining and vigorous lava spattering continues to produce lava flows on the northwest flank of the cone, and a significant ash and steam plume that forms a column rising 2-3 km and spreading along with the winds in various directions, currently including easterly currents, which unfortunately brings the ash plume to the airport area. This forced the closure of the airport since yesterday, forcing the diversion of flights to Tenerife. Near the eruption site, the air quality has been worsening again, because a strong thermal inversion at low elevations, between 600 and 700 meters of altitude, traps gas and ash from the eruption in the Aridane valley. The new lava flow arm that started yesterday from the southern margin of the main flow continued to advance between Los Guirres and El Charcón and now overlaps the lava delta (fajana) which had been created during the 1949 San Juan eruption, leaving an island of so far untouched land in between.
The intensity of the eruption remains high, with only a slow decrease, but seismic activity beneath the island has increased, both in the number of earthquakes and in their magnitude. On October 8, two earthquakes, of magnitudes 3.5 and 2.5, occurred at only 8 km and 7 km depth, respectively, near Puerto Naos. A magnitude 4.3 earthquake, the largest earthquake since the Cumbre Vieja eruption on September 19, was recorded on October 7 near Villa de Mazo at a moderately shallow depth of 35 km. The locations of the quakes remain more or less the same, mostly at 10-15 km depth beneath the center of the volcano.
October 10
The eruption continues at similar levels as during the past days. Explosions have been stronger and near constant this morning, with highly noisy, energetic and sustained explosions. Vibration of soil, vehicles and windows can be felt in the entire range of more than 5-6 km around the vents.
Suggested by ongoing elevated tremor, lava effusion rates remain high. New lava arms have advanced at the western fronts at the coast and the existing ocean entry as well as in the upper northern margin, where tongues of lava flows have reached the Calle Principal de Tajuya where industrial buildings are located.
Deformation of the ground has remained stable, with a weak trend of deflation in some points. Earthquakes continued to increase slowly in numbers and intensity, though. During the past 24 hours, there was 1 quake of magnitude 4.1, 50 quakes between 3.0 and 3.9, and 100 quakes between 2.0 and 2.9. The quakes remain clustered at 10-15 km depth beneath the central part of the volcano, with a few events at various locations at 35-40 km depth in the upper mantle beneath the island.
October 11
Volcanic lightning over La Palma's Cumbre Vieja volcano eruption, triggered by the friction of colliding pyroclasts –and sometimes water– releasing ions within the volcanic plume. It's a rare phenomenon that has occurred for the first time in La Palma.
During the past 14 days, La Palma was shaken by 7 quakes of magnitude 4.0 or above, 287 quakes between 3.0 and 4.0, and 607 quakes between 2.0 and 3.0.
The lava forms a rather narrow front, with a fast rate of advance, at about 500-700 m per hour. It is now hoped that its channel or tube system will remain stable to direct the lava straight into the ocean instead of widening the flow or branching off, which would put the town of La Laguna at risk.
The current seismic activity shows worrying signs, pointing towards that more magma is moving upwards: several earthquakes have appeared at depths less than 7-9 km; after the 4.2 quake three days ago (October 9), there have been episodes of spasmodic tremor with many earthquakes in a row that indicate movement of magma in depth; since two days ago (October 10), the appearance of strong volcanic tremor at around 18 Hz frequency thought to be caused by depressurization of fluids at great depth around 10 km. In the best scenario, the current conduits will continue to cope with it and the magma will erupt from the existing vents. In the worst scenario, magma could open new fissures in a different area. In a scenario in between, new fissures might open near the existing vents, and new lava would erupt onto existing lava fields.
October 13
Since its origin, Cumbre Vieja volcano on the Spanish island of La Palma has expelled over 400,000 tons of SO₂, more than all active volcanoes throughout all of 2020, breaking the world record and surpassing the previous holder of the title, Miyakejima volcano.
Rivers of molten rock that were described as 'a true lava tsunami' forced the evacuation of more than 300 people late Thursday. The lava is expected to flow to advance to the northwest, beyond the boundary of the evacuated area. It has spread to 732,5 hectares, destroying 1,817 buildings and burying nearly 60 km of roads, and since the eruption started on September 19, about 7,000 people had to flee since the eruption. On the south-eastern slope of the main cone, a new vent opened around 08:30 pm. The new eruptive centre emits gas and pyroclasts.
During the past 14 days, La Palma volcano was shaken by 16 quakes of magnitude 4.0 or above, 347 quakes between 3.0 and 4.0, and 815 quakes between 2.0 and 3.0. Today (October 16) at 5:41 a.m., La Palma was hit by the largest earthquake since the eruption began. The quake rattled the island with a magnitude 4.6 and it was felt all over the island. It is one of seven quakes of magnitude 4.0 and above so far since yesterday. As the other larger quakes, it was located deep under Cumbre Vieja volcano, at 37 km depth. The interpretation of these deep and often comparably larger quakes in relationship with the ongoing eruption is still matter of debate.
Explosive activity–the lava fountain in particular–has decreased a lot and often is absent. The eruption has transformed to be dominantly effusive. This could mean that the magma richest in gas, usually at the top of a magma batch in the reservoir, has erupted first and has been exhausted by now.
October 21
On October 21, the island was rocked late at night by its most intense earthquake since the island’s volcano started to erupt a month ago. The quake, of magnitude 4.8, was felt not only across the island but also in the neighbouring island of Tenerife. It is feared that the force of the tremors will intensify; in light of the current level of seismicity, the earthquakes could register a magnitude of 6.
The current Cumbre Vieja eruption has expelled 10 million m³ of pyroclasts covering 6,800 hectares.
Regrettably, the eruption continues still with no signs that could fuel hopes it might stop any time soon. After swallowing the village of Todoque in its entirety, the lava flows have reached the centre of La Laguna, which is in the course of being completely destroyed as well. In terms of economic damage, it already ranks among the most devastating volcanic eruptions in the recent history worldwide.
October 22
The eruption continues with activity fluctuating between more and less intense phases at the vents. Near-constant fountaining form the summit vent at the cone produces dense ash emissions that rose to approx. 2,800 m today, while lava spattering and lava flow effusion can be seen from the lower vent. However, most lava is likely invisible at the vents as it is going directly into a system of underground lava tubes that have formed with time and transport it to various areas of the active flow field, which continues to advance slowly at various fronts, mostly along its northern margins.
Volcanic tremor levels remain high, suggesting that the magma rate as well continues to be very high, estimated to be around 60-70 cubic meters a second.
Volcanic earthquakes continue to increase if not in size but in numbers; during the latest 24-hour period, the National Geographic Institute (IGN) detected 135 earthquakes under the island, 14 of which were felt by people. The strongest quake was a magnitude 4.4 event at 11.54 p.m. last night, while another quake of magnitude 4.2 occurred earlier this morning. Both of these stronger ones were in the deeper layer between 35-40 km depth. Most other quakes were under the center of Cumbre Vieja at around 12 km depth “as usual”; this area is believed to be where the magma is stored before rising to the erupting vents.
There are 7 active vents from which different materials emanate. Each of the 4 vents of the main cone presents its own characteristic activity, which is as following from west to east (upslope): a first Hawaiian vent which solely emits pāhoehoe lava flows; a second pulsating Hawaiian vent with gases; a third vent which emits gases and water vapor; and a fourth Strombolian vent which emits pyroclasts and gases. Due to the considerable slope of the terrain in the direction in which the fissure opened, high pressure lava fountains, pyroclastic materials and gases were emitted mostly from the higher volcanic vents, while from the lower vents only more or less degasified lava poured out with a much lower explosivity. This is because in upper vents, gas bubbles usually form a type of conduit within the magma column, causing magma to erupt as gas jets with little liquid and more ash; whereas areas at the margins of the main column might be largely degassed on the other hand, and these will form liquid, but lower fountains or entirely effusive vents.
The secondary cone, 300 m away from the main one, possesses a phreatomagmatic vent which emits water vapor, gases and ashes. External water—from the groundwater system—somtimes interacts with the magma. Depending on how much water is present and able to interact with the magma, this interaction can completely change the dynamics of the activity at some or even all vents. Water can absorb a lot of energy, but if in contact with magma, it typically transforms into steam as result, which goes with a thousand times increase of volume. If the generated steam is not easily released, it becomes over-pressured, and once this pressure overcomes the surrounding containing pressure, it will result in violent explosions known as phreatomagmatic. Phreatomagmatic activity is more likely to occur at the vents furthest away from the center, where magma rises through older rock layers that might still contain water or are in connection with aquifers.
The main cone currently stands at 200 meters tall and the dense ash emissions rise to approximately 2,800 m. Most lava is invisible as it is going directly into a system of lava tubes and transport it to various areas of the flow field, which continues to advance slowly at various fronts, mostly along its northern margins. The intense volcanic tremor suggest that the magma rate likewise continues to be very high, estimated at 60-70 m³/s.
Different colours can bee seen in the smoke emanating from the active cone. Each colour reveals its composition. The dark grey plume is composed of fresh ashes and is primarily generated by explosive activity such as lava fountains. Plumes that are brownish in colour carries older ashes, and this is produced during a collapse in the cone, lava bomb impacts, landslides, etc. When the plume is reddish, it contains old rock which has been chemically eroded and ground, and is caused by the weakening of old conduits or unclogging explosions of the main vent. The colour white, which is very common, carries no ashes and is solely composed of water vapour and is generated by effusive activity or fumaroles. A blue hue signifies sulphur dioxide, produced by strombolian eruptions, fumaroles and effusive activity.
October 25
The eruption has become more intense than ever. The volcano shows strong explosive and effusive activity. The summit vents have been producing spectacular lava fountains and an ash plume that rose to 3,800 m. Following the intense activity from at least four vents, parts of the western crater walls at the vents collapsed and gave way to short-lived floods of lava on the slopes of the cone.
The combined explosive-effusive activity paired with high amounts of magma reaching the surface has been causing changes in the morphological configuration of the growing cone, such as rapid accumulation against the forces of gravity, collapses, drag of ejected material, and formation of tubes. At least 4 or 5 active vents are aligned in a row, with different behaviour as the magma pressure varies with the height of the vents themselves and the complex interactions of the rising gasses and the fluid magma in the conduits.
Earthquakes have increased in numbers, most at around 12 km depth under the central part of Cumbre Vieja and a few deeper ones around 35 km depth. Ground deformation has no clear trend, which suggests that magma pressure from below is stable. This might be due to the progressive supply of magma from deeper sources to balance the erupting volumes, keeping the eruption at an equilibrium, which could possibly indicate that the eruption could go on for longer still and that a soon end is not in sight.
October 26
On October 26, the visible activity at the vents had slightly decreased at first. The drastic morphological reconfigurations at the vent had likely created new conditions which facilitated that the arriving magma could more easily find new ways to enter existing conduits or create new ones. Instead of slowly deflating as the magma chamber is being emptied by the eruption, the ground near the eruption site in fact rose dramatically, around 10 cm. This amount of inflation may have been caused by more magma arriving from depth into shallower reservoirs than what was erupting. Compared to the daily average, half as many earthquakes occurred that day, yet one of the strongest quakes so far was registered at magnitude 4.9 at 40 km depth.
The explosive activity greatly increased in the evening, producing a tall lava fountain at the main vent which reached up to 600 m in height, while other vents produced dense ash.
This day marks the 50th anniversary of the forelast eruption of Cumbre Vieja, the Teneguía, which lasted 24 days, from October 26 to November 18, 1971. It is called the "Friendly Volcano" by locals, as it did not cause much damage, highly contrasting with the ongoing eruption.
October 27
On October 27, the explosive activity remains very high since it increased the day before. Tall lava fountains, reaching up to 600 m in height, rise from the vents, while others produce dense ash and lava spattering. Lava can also be seen flowing on the surface away from the cone. This seems to be in accordance with an increase in the number of earthquakes. On this day, there were 4 quakes between magnitudes 4.0-4.7 alone, as well as about 130 quakes of around 2.5-3.9. One magnitude 4 quake occurred at the shallow depth of 13 km, which is suspected to be the main reservoir of the magma before it rises to the vents. Apparently, peaks in earthquake activity precede phases with increased lava supply several hours later. At first, magma pressure at depth increases either by surges from newly arriving magma or from temporary blockages in the conduits above, preventing a sufficient release at the eruption; then, the pressure on the surrounding rocks create new fissures, resulting in earthquakes; finally, the magma then rises through the new and existing conduits until it reaches the surface hours later.
October 30
The island was shaken by an intense magnitude 5.1 earthquake at 39 km depth underneath the centre of Cumbre Vieja at 07:24 am local time. This is the strongest quake to date since the start of the eruption in September as well as the seismic crisis.
The volcanic tremor is very high, and the bright glow from the lava fountain indicates the elevated activity. The quake may mean there is yet another pulse of magma from a deeper source on its way to the surface, in which case, the activity might increase in the course of the day.
The VAAC (Volcanic Ash Advisory Centre) of Toulouse has warned about a volcanic ash plume that reached about 3000 m in height and is moving at 18.5 km/h in a westerly direction.
October 31 — November 3
Due to an inversion, the Aridane Valley was covered in thick vog (volcanic fog), which mixed with an incoming dense Saharan dust surge, severely decreasing the visibility and air quality. Vog from the eruption of Cumbre Vieja has been seen in satellite imagery, streaming towards Europe and across the Atlantic Ocean.
Vog, also known as smog, is a form of air pollution that results when sulphur dioxide (SO₂) and other gases and particles emitted by an erupting volcano react with oxygen and moisture in the presence of sunlight. Typically, in a dense Saharan dust surge, the sky can appear dull or tan. In contrast, sulphur oxides are colorless, and vog looks grey. Once the vog layer dissipates, grey spots of vog in the sky may, for a time, remain trapped in the inversion layer. SO₂ is a colorless, irritating gas that has an acrid odor like fireworks or a burning match. It is also emitted from sources such as fossil fuel power plants and motor vehicles. Fine particles consist of particulate matter less than 2.5 micrometers in diameter and are referred to as 'PM2.5'. These particles are smaller than the width of human hair. PM2.5 in vog is mainly composed of acid and neutral sulfate particles. Other sources of PM2.5 include vehicle exhaust and smoke from fires. Vog contains mostly SO₂ and acid particles, in contrast to urban, industrial, and other pollution sources, containing additional toxic contaminants, such as ozone and hydrocarbons.
The amount of SO₂ emanating from the volcano has been decreasing over the last few days. Even though the SO₂ levels remain very high, it has been decreasing for the last 7 days and it is already below 5,000 tons per day.
The magnitude 5.1 event of November 3 is likely the strongest-so-far tremor under the volcano since the seismic crisis followed by the ongoing eruption began in September. It was felt all over the island, and if the depth is correct of only 26 km it deviates significantly from the depth layer around 35-40 km, which has been where other stronger quakes in the range of magnitudes 4.5-5 that have occurred so far. This could be due to new magma intrusion into intermediate layers at this depth. It will be important to see whether it will be followed by an increase of lava activity in the near future (several hours from now possibly).