The geologist José Mangas, on La Palma: "Carbon gas emissions are high in Puerto de Naos and La Bombilla, they can cause death"

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September 19, 2021. Three in the afternoon. After more than 25,000 minor earthquakes, a strong tremor with a magnitude of 4.5 shakes the island of La Palma, in the Canary Islands archipelago. There, at that moment, what is the most recent volcanic eruption in Spanish territory began. In an area known as Cumbre Vieja, in the south of the island, magma, gases, and pyroclasts begin to come out. When the eruption ends, three months later, the volcano will end up being called Tajogaite.

More than a year later, the lava has stopped coming out of the nine craters that make up the Tajogaite volcanic complex, but the research teams continue working. Not at the same level as during the emergency, but time cannot be wasted: "Carbon gas emissions are high in the coastal area of ​​Puerto de Naos and La Bombilla, it is forbidden to enter there, it can cause death," he explains. José Mangas, professor at the Institute of Oceanography and Global Change and the University of Las Palmas de Gran Canaria.

The geologist has opened the annual cycle Colloquia that celebrates the Institute of Science of Materials of Madrid (ICMM), CSIC. An event in which experts from different areas come to the center to tell about the latest advances in research in their field. In this way, this Wednesday, September 26, dozens of people have had the opportunity to listen to the geologist explain what happened in La Palma before, during, and after the volcanic eruption.

Because, effectively, a seismic swarm (a set of earthquakes very close together) was already warning that something was happening under the canary island. During the eruption, the expert did not tire of explaining to everyone who listened to him that nothing could be done to stop the advance of the lava: “With a liquid of 1,200 degrees, nothing can be done. In one second, 10 cubic meters of lava came out”, he recalls. Now, with the perspective of time, there are things that have not changed. Research remains more necessary than ever.

"Now we are in the posteruptive process," explains the expert, who indicates that hundreds of millions of cubic meters of magma remain under the island. In fact, it estimates the amount of lava that came out in 2021 at 10%. The rest remains inside, but without so much pressure in the gases that force it out. "When the eruption occurs it is because there is too much volume of gas and liquid, that puts pressure and, as it wants to come out, the structures of the insular building break and the eruptive fissure is generated, the material begins to come out and loses pressure." He gives a very graphic example with a pressure cooker: when the valve is removed, gases come out, but inside the cooking continues.

So can there be a volcanic eruption in the same area again? The short answer is yes, but always with nuances: “This can happen at any time, five years from now or 40 years from now. That is going to be there for a long time. In human life, it is normal to see two volcanic eruptions in the Canary Islands”, he indicates. That is why, he insists, it is so essential to have the southern area of ​​the island under control, with a much greater volcanological risk than the north.

In fact, there is still a significant exclusion zone around the magma, already almost cold compared to the temperature it reached last fall. The Geological and Mining Institute of Spain (IGME), Involcán, and the island government make daily measurements at fixed and portable points and have been able to see how there are still many fissures from which gases come out and how in some points temperatures exceed 300 degrees, reaching 900 in the crater. However, many of these gases are colorless and odorless, an unseen threat. And that, together with the time that has passed, makes the residents of the area desperate.

"There are still more than 300 people in hotels," acknowledges Mangas, who says that the most dangerous area is Puerto de Naos and La Bombilla, a tourist focus on the island before all this happened. People want to return to their lives before the eruption, and it's normal, but approaching that area puts them at risk of death. The professor regrets that there are people who have skipped the controls: "There were no deaths in the eruption, that there will not be now," he says. The problem, again, is that it is not possible to know how long this situation will last: in Teneguía, the La Palma volcano that erupted in 1971, there are still toxic gas releases.

Learnings

Mangas insists a lot that when a volcano begins to spew lava there is not much to do, but other things are very clear to him. “The process has not died”, he comments on Tajogaite, to immediately add: “it may have been active for decades, but as long as the public bodies are there we can rest easy”. In this regard, he celebrates how well PEVOLCA (Canary Islands Volcanic Emergency Plan) worked: "We are in good hands," he stresses.

The emergency experience has allowed us to learn a lot in scientific matters and is also a unique opportunity to spread geology and volcanology: “Science has shown its usefulness to people. This has served us as experience, if another [eruption] comes, we know what to do. Material losses will continue to exist, but there have been no human losses,” he reiterates.

"From a scientific point of view we have never talked so much about geology in the media," he comments during the talk, when he acknowledges that experiencing this eruption live was almost a gift: "It is a paradise for geology and volcanology." Now scientists from practically all areas of knowledge are working hard to study what happened at La Palma at all levels. For example, under the sea, there are almost three hectares of solidified magma, and it is already being observed how the flora and fauna are returning. Minerals are also studied, although with the risk that temperatures remain extremely high.

The human drama, however, will not have such a quick solution. Neighbors cannot return to houses that no longer exist, and the solution is not clear. The scientist regrets that next year there will be up to four electoral appointments, which will influence the decisions made by the administrations. He talks about the 'sorriba', a Canarian word: "You bring the soil from the mountain, you put it on the malpaís, and you start planting banana trees," he describes. “It has been done a lifetime, but is it worth it? Do we want to go back to what we had before?” he asks, recalling that the banana plantations “survive thanks to European aid”. In the end, a reflection: “There are so many problems, they are going to last so long… and you can never give everyone everything they ask for”.

You can watch the seminar (in Spanish) here:

-- Ángela R. Bonachera (text) andd Carlos Arroyo/Morgan (photo) - ICMM Comunication.