The five keys to the eruption of the La Palma volcano: “The next few hours are critical”

After thousands of earthquakes in just seven days and a deformation of the terrain that has reached levels exceeding 15 centimeters, the Cumbre Vieja volcano, in the municipality of El Paso, erupted this Sunday. The magma, in its attempt to rise to the surface, has been opening several fissures through which it has managed to escape. The huge column of gases and the lava tongues advance slowly but unstoppably, and the authorities have asked that no one approach the area.

The next few hours are key to determine what will be the evolution of the eruption. Although at the moment not considered to be of great danger, the authorities have already activated the red alert in some municipalities of the island such as Tazacorte, El Paso, Fuencaliente, Villa de Mazo and Los Llanos de Aridane. This alert level contemplates the immediate and mandatory evacuation of the population due to the real threat of the eruption. “Eruptive dynamics can change in minutes “says Stavros Meletlidis, one of the volcanologists from the National Geographic Institute (IGN) who are following the eruption on the ground.

Why has it erupted?

The seismic swarm or the chain of earthquakes that began on Saturday, September 11, in the west of the island, could or could not end in an eruption. There was room for all the possibilities. The only weapon of the experts in volcanology was constant vigilance. The explanation is that there is no factor or fact that triggers an eruption.

David Calvo, spokesman for the Canary Islands Volcanological Institute (Involcan), points out that this episode “It is a normal operation of the island”. At the base of the Canary archipelago there is a magmatic body that rises and gradually reaches the surface, so it is a question of its “logical operation”.

In the days prior to the eruption, experts warned of the possibility of a series of chained earthquakes of greater intensity that could lead to a rash. And this is precisely what has happened. After several tremors of a magnitude greater than three, and a deformation of more than 15 centimeters, the lava has found the energy and the way to rise to the surface.

In 1971 the last eruption took place on the island of La Palma, of which there is hardly any data due to the lack of instrumentation that existed then. More recently, the Canary Island of El Hierro suffered the last eruption of the arghipiélago until today. It happened in 2011 and it was underwater. The seismic swarm that preceded the eruptive episode then lasted three months and not a week like the current one on La Palma.

What is a strombolian eruption?

The eruption that began this Sunday on La Palma is an eruption characterized by small explosions of materials in molten or pasty state and that can happen in just a few minutes or hours. Generally, these explosions are accompanied by spillage of lava flows.

As Itahiza Domínguez, a volcanologist at the IGN, explains, “it is not a violent eruption”, but rather “quiet.” The pyroclasts of the lava flows that the volcano emits are “quite viscous and does not flow as easily”. This is an important piece of information, because as the expert says, on La Palma “there are very large slopes and they can move at high speed”.

What is a fissure rash?

Stavros Meletlidis, also a volcanologist at IGN, explains that this eruption is also fissile. That is, in the first hours, the magma originally caused two fissures in the Cabeza de Vaca area, two mouths through which the lava escaped. In just a few hours, these cracks multiplied and there are already more than seven.

The emission points, therefore, are several, and as the expert explains “more can be opened in the next few hours”, because “they are unpredictable”. He assures that they are in constant vigilance because “another one can be opened at any time or several can erupt at the same time.”

What materials does the volcano expel?

There are at least a total of eight craters that are emitting lava, ash, and incandescent rocks. Calvo explains that “it is likely that a mouth will stop emitting lava or a new one will open,” so “the first hours are critical”, especially with regard to the reorganization of the deployment of teams in the field.

The eruptive column, the huge cloud of gases formed after the eruption, is key. This column is made up of ash, carbon dioxide, sulfur dioxide, and many other chemicals that can provide information to understand the operation of the volcano or know aspects such as how much magma it contains or what its evolution will be in the next hours and days.

Calvo says that analyzing in particular how much sulfur dioxide the volcano expels “is essential”, because “it indicates the degree of activity of the eruption, and especially if there is a source of magma that continues to feed” the eruption.

What to Expect

“Now what we expect is a normal evolution,” says Calvo. This means that the eruption can go on for days or weeks, a fact that will be known when the experts know what the discharge rate of the volcano is. “From there you have to wait, the volcano is the one that calls the shots,” says the Involcan spokesperson.

The expert admits that “it is not an eruption of great danger”. However, the operators deployed on the ground focus on the main threats: lava columns and volcanic gases. Although it is a lava that does not move very fast, dynamics can change in minutes, as they assure from the IGN.

At the moment, the eruption has caused several small forest fires on the island that cannot be acted upon. The danger that they generate so much the unpredictability of the eruptive mouths as the toxicity of the volcanic gas cloud it keeps authorities and the population at a safe distance. As Meletlidis explains, “the most important thing is to protect the population and the workers deployed in the area.”

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