Beyond La Palma volcano: eruptions, myths and truths | Frequency, dangers, populations at risk

In the midst of a pandemic, dealing with phenomena such as volcanic eruptions makes it seem like those sci-fi movies that were enjoyed with popcorn in the living room can come true. In recent days, the news around the Cumbre Vieja volcano in La Palma (Spain) or the Kilauea (EE.UU.) they make up the informative menu of the press around the world. In this note, three vulcanologists and researchers from Conicet remove the spectacular halo of the event and agree that they are “beautiful” events, “potentially dangerous” but without “nothing extraordinary”.

“Seeing more and more eruptions is closely linked to population growth. The more the planet is inhabited, it seems that there are more eruptions, but it is nothing more than a simple human perception», He warns Ivan Petrinovic, doctor of geological sciences and conicet researcher at the Earth Science Research Center. The specialist highlights an anthropocentric flaw: in past centuries, as the Earth was less busy and intercontinental communications less frequent, eruptions were not recorded despite the fact that they occurred with the same frequency.

“Within the scientific community, this does not surprise us at all. Beyond the danger and the risk, the truth is that watching the eruptions live allows us to learn a lot, especially when most of our references are generally related to old events ”, he insists in the same direction. . Patricia sruoga, PhD in Natural Sciences and Conicet Researcher at the Institute of Geology and Mineral Resources.

In recent days, the lava from the volcano Cumbre Vieja in La Palma (Canary Islands), with its temperature of 1000 ° C, reached the sea, which was at 23 ° C and, from the thermal contrast produced waves of boiling water and evaporation of toxic clouds (may affect the eyes, skin and lungs). Although potentially dangerous, they dissipate quickly in the atmosphere. Likewise, the magma – masses of molten rock – has generated a deposit in the ocean of about 50 meters: like a pyramid in the middle of the sea. The good news is that no one has been injured or killed yet. been reported.

Mariano Augusto, doctor in geological sciences and conicet researcher at the “Don Pablo Groeber” Institute of Andean Studies, agrees with his colleagues’ position and takes the opportunity to demystify the question. “Nothing changes: we don’t live in a particular context, volcanoes erupt according to their periods of recurrence and according to geological time. What is strange, then, is not that they break out but that there are people who live nearby”. And he continues: “The lava front moves like a hot rock mass. It does not imply a risk of life, but it does imply a structural type, everything he meets on his way, he carries yes or yes ”.

Volcanic activity is also unpredictable and creates uncertainties. To the massive evacuations (more than six thousand families had to leave their homes), the confinement of towns and the isolation between the peoples of the island, is added the fact that lava has reached the sea. This will affect the marine ecosystem by causing a “heat shock” in species that cannot reach refuge quickly. Likewise, with the volcanic eruption, greater seismic activity was recorded.

When could the lava stop?

La Palma is an archipelago of volcanic islands, which began to form over 20 million years ago. In reality, the islands have developed at the expense of magmatic matter which is located on the surfaces of the ocean depths. Over the past few centuries, it has erupted more than ten times, confirming a strong recurrence. Sruoga explains, “The last eruption was 50 years ago. Perhaps in human terms it is a long time, but for the evolution of a volcano it is nothing. By looking at the satellite images, we can see that a string of mouths is forming above the large fissure that fed the lava throughout the growth of the island ”.

Despite the fact that technological artefacts are increasingly sophisticated in all scientific disciplines, researchers do not like to make projections or use determinisms. And as they do, because nature surprises. “There are methods that could help, the hardest part is knowing what is going on in depth. The duration of the eruptive crisis will depend on the volume of magma available and this is the most complex thing to assess.“Sruoga says. Seismic activity, for example, gives an idea of ​​the magnitude of the phenomenon: if earthquakes occur very regularly, this may indicate that matter is rising. and that the volcanic situation is far from being resolved.

The impact of the volcanic threat is measured by the degree of explosion of the eruption, in a Volcanic explosive index ranging from 0 (no explosion) to 8 (maximum explosion point). “La Palma is in the lowest explosive ranges, between 0 and 1. That of Krakatoa in 1883 (Indonesia) reached a 6 and it was really devastating. Mankind has few records that reach 8 because they occur every 100,000 years, ”says Petrinovic. There are more energetic volcanoes at a shorter distance: Calbuco or Puyehue in the Andes mountain range, for example, generate ash that exceeds 15 meters in height and can travel more than a thousand kilometers.

Comparison with Hawaii and other volcanoes without an agenda

To that of Spain, Wednesday the eruption of The Kilauea volcano in Hawaii (USA), one of the most active on the planet. As it occurred in an area far from dwellings, the situation seems to be controlled on the perimeter of the Volcanoes National Park. The alarm is fueled by the spectacular nature of the event: lava fountains can exceed 1,100 ° C and reach the height of a five-story building. “The two phenomena, that of the Canary Islands and that of Hawaii, are very similar, although in the latter case it is very limited to the Kilauea caldera. For this reason, the damage it could cause is less. Even if you never know: three years ago there was an eruption with similar characteristics, ”says Sruoga, referring to 2018, when an eruption destroyed 700 homes and forced the displacement of thousands of people.

At Iceland, Fagradalshraun volcano It has been erupting since March and is no longer part of the informational menu of mass media as there is no population or infrastructure nearby. At present, in fact, it constitutes a tourist attraction which, in short, generates benefits for the surrounding areas of the capital, Reykjavik. “There are volcanoes that have more press than others. La Palma is one of them, because it affects many economic assets. At this time, the Merapi in Indonesia it presents a rash with very strong explosions but does not come out from many sides. You hardly see any information about it. There must be about ten or fifteen who are active but we only lay our eyes on a few: the Europeans», Sentence Petrinovic.

The next day: land use planning

“When the eruption ends, there will be urban development depending on the volcanic threat. About lavas, there is not much that can be done; although they will surely serve the tourism promotion, as is the case today with the Timanfaya in Lanzarote (which erupted in 1730, Spain). The interesting thing will be to know who will own the new lava delta that has formed. The next door neighbor? The state? These are situations that they will review as they go, ”emphasizes Petrinovic. As the island’s population grows, the problems multiply. Thus, the emergency plans drawn up by the authorities are essential to minimize the damage that natural phenomena can cause in inhabited sites. “The big challenge is not so much knowing when a rash begins and ends, but the territorial orderReal estate pressures peak in promoting buildings in places where it should not be allowed.

The Vesuvius in Italy it erupted in 1944 for the last time. For geological times, it hardly represents a sigh and, nevertheless, it has the city of Naples, with millions of inhabitants at its feet. With 7.5 billion inhabitants – and sometimes thanks to the concentration and unequal distribution of land – on the planet there is less and less space to live and the lands surrounding volcanoes, being beautiful, are often used for tourism. Augusto makes an illustrative discrimination between the concepts of danger and risk. “The danger is linked to the characteristics inherent in the event; Therefore, if a volcano in the middle of the puna were to erupt, it would not involve a risk as it is a sparsely populated area. On the other hand, if there is one that is only 200 meters from an inhabited area, even if it is not so dangerous, with the minimum of activity, it generates a risk. This is what you see today in La Palma ”. If there are no casualties, managing the crises associated with volcanic eruptions is often considered “successful”. This is what they say in Spain.