The awakening of the La Palma volcano began years ago

The awakening of the La Palma volcano began years ago

Although not with much time, most weather phenomena can usually be predicted with some time in advance, so that in the event of a disaster the population can protect itself as much as possible. However, with the geological ones, things change. Predicting a major earthquake is tricky, since not all seismic swarms they carry one behind. And something similar happens with volcanoes. The La Palma volcano began to notify of its activity 8 days before your eruption, although no one could know when it would actually happen. But the truth is that the 8 days was only the final notice. Actually the Old Summit had begun to show signs of activity four years before.

It is not something new. However, it is the information on which the volcanologist has focused Marc-Antoine Longpré in a study just published in Science. In it he describes the warnings that the La Palma volcano in form of seismic swarms and looks at how those earthquakes and everything that followed could help improve earthquake prediction strategies.

It is a terrible catastrophe, which has become a nightmare for the palm trees, but at a scientific level it is of great interest, since both this and other Canarian volcanoes have shown to go against what is established for other basaltic volcanoes. They provide the necessary rebellion to make more precise the predictions that have been established based, above all, on those large volcanoes whose eruptions do not usually go beyond what is marked.

Why is the La Palma volcano so interesting?

Persistently active volcanoes, such as the Kilauea or the Etnaare easy to monitor, as clear patterns can usually be identified just before disturbances.

However, both the Travel Summit Like other volcanoes on La Palma, they have had reactivations after long periods of activity. This intermittence makes it practically impossible to establish its modus operandi, if they really have any.

In fact, since the 16th century it has been known for periods of rest ranging from 24 to 237 years. The last great eruption took place in 1971, a time when there was only one seismic station in Tenerife that served for the entire Canary archipelago. Of course, if there were warnings in the form of seismic swarms at that time, it would have been very difficult to detect them. But the data prior to this latest eruption can give us interesting information for the future. Now, what are those data?

The notices of the Cumbre Vieja

It all started in october 2017 with a seismic swarm that lasted 8 days, during which they gave up 128 small earthquakes. They were very mild, with a magnitude 1-2 and a depth of 20-25 kilometers. To this day, volcanologists understand that this could indicate that an intrusion of the precursor of the volcanic magma was being generated in the deep mantle.

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The 2017 seismic swarm lasted eight days

And the thing kept shaking. After that episode it did not take long for another similar one to occur in February 2018, although this time they were only 84 earthquakes. Then there was two and a half years of relative calm, with very few tremors, so those swarms did not seem to indicate anything. However, in the second half of 2020, La Palma trembled again. From the end of July of that year until February 2021 up to six seismic swarms were detected, which were from 14 to 160 earthquakes. This time they were even deeper than those of 2018, about 30-35 kilometers below the surface.

But then they came again six quiet months. Six months after which, finally, the whole hecatomb arrived. In August, seismic swarms began again, rising again to 20-25 kilometers, demonstrating the dynamics of magma pipes. The activity was increasing more and more, until on September 11 the tremors, already at less than 12 kilometers below the surface, were counted by the hundreds. There was hardly any doubt that the Cumbre Vieja would erupt. However, no one knew when it would happen.

Finally, the volcano of La Palma woke up on September 19, beginning an activity that still continues two and a half months later.

What can this eruption teach us?

In his study, Longpré relates that it was a surprising eruption, since its level of explosiveness did not seem to correspond to the historical records of La Palma. Violent strombolian explosions and vents spewing great columns of ash that rose up to 6 kilometers in height gave the starting signal for a terrible eruption.

To date, the 1,000 earthquakes in 3 days, and the activity, although sometimes it seems that it is going to give a truce, remains high. Thousands of people have been evacuated from their homes, which in many cases have ended up being engulfed by lava.

The study also cites the underwater eruption that took place on El Hierro in 2011

Right now, the priority is the palm trees. But when it’s all over, scientists have a lot to do. In the study of Science this volcanologist also quotes the underwater eruption that took place on El Hierro between 2011 and 2012. On that occasion, the notices lasted 96 days. For this reason, the Cumbre Vieja is not the only interesting one with a view to developing new predictive models. “In general terms, the Canarian volcanoes challenge the global relationships between times of preparation for rest and eruption, as they are typically shorter than in the most commonly represented basaltic volcanoes ”, points out the expert in his study. “This represents crucial information for forecasting eruptions in dormant volcanoes.”

At the moment this volcano has taught us to feel small before the greatness of nature. Then perhaps it will help us enhance the greatness of science.