The magma that has entered under the volcanic building on La Palma has raised the ground by one and a half centimeters. This movement is often used as a precursor to a possible volcanic eruption, however, according to María José Blanco, director of the National Geographic Institute (IGN) in the Canary Islands, the elevation should be much higher for it to cause an explosion in a short time. In fact, Blanco rules out that this happens for the moment on La Palma. “There will be an eruption but it will not be imminent”, says Blanco.
As Blanco explains, this circumstance occurs because the earth’s crust is an “elastic solid” that the hot magma, therefore, can mold. It is considered the precursor of an eruption because, when it can no longer deform the ground, the overpressure causes it to break it emerging and turning into lava. Apart from the deformation of the terrain and seismicity, to know if an eruption is going to occur, the emission of diffuse and dissolved gases is also measured (so far it has only emitted Helium-3) and gravimetría, that is, the variations that could occur in the gravitational field.
The swarm, however, remains constant and the data reflects that it could be growing. Hence, the surveillance of the swarm, which has led to the declaration of the pre-alert (or yellow alert) for volcanic risk in La Palma, is maintained with more intensity than ever. In fact, yesterday, the Government Delegation in the Canary Islands requested the National Center for Monitoring and Coordination of Emergencies (CENEM) to activate the Copernicus due to the seismic activity detected on the island of La Palma and at the request of the Geological and Mining Institute of Spain (IGME). One of the tools in this program is to provide emergency mapping and images.
Seismic activity on the island continues unabated for the fourth consecutive day on the southern slope of the island, from Fuencaliente to Tazacorte, passing through El Paso and Mazo. That is to say, in what is known as Cumbre Vieja, where there are several volcanic cones that “could favor the ascents of magma”, as indicated by Blanco. However, as he insists, it is unlikely that this magma that is moving under the building of the island may end up emerging through one of them, given that “the eruptions in the Canary Islands are monogenéticas“In other words, they are generated only once.” For each eruption a different building and volcano are generated “, indicates the director of the IGN, and this has been the case in all the Islands except in a very specific corner: Teide and Pico. Old.
Less times, closer
In this sense, although its periodicity decreased somewhat on Tuesday – fewer earthquakes per hour – the earthquakes were located closer to the surface, specifically between 10 and 8 kilometers deep and have been located further west. This movement, which is consistent with the location of the elevation of the land, has moved the earthquakes to El Paso where, in addition, the strongest to date has been experienced: a magnitude of 3.5 mbLg at 7:00 a.m. yesterday. This earthquake had an intensity of 3, which means that it has been felt by only a part of the population and that it has not caused any material damage. In total there have been 15 tremors with a magnitude greater than 3 since the series began and all of them have been felt by the population.
Precisely the anomalies that currently exist under the island of La Palma have caused the magnitude to be overestimated at first, in which it was conceived that it had been 3.9 mbLg. Since this seismic swarm started –The eighth of the series that the IGN began to monitor the series in 2017– 2,935 earthquakes have been detected in the southern area, of which 616 have been located.
The swarm began at 4:18 am on the 11th and yesterday they continued to occur until after noon. Most of the recent earthquakes had a magnitude greater than 2 mbLg. What can happen on La Palma in the next few days is a mystery, even for experts. For her, La Palma could be in a phase similar to that experienced by El Hierro in September 2011, a month before the Tagoro eruption occurred. However, all this activity could “stop in a few days”, as has happened on past occasions; O well “it can be prolonged and end in a superficial eruption”, White points out.
Seismic swarms are quite common in that area, in fact, they have been recorded since 2017. Specifically, on October 7, 2017, a first seismic series was recorded in the extreme south of the island of La Palma, in which some 300 earthquakes detected at about 25 km depth. The same scenario was repeated in February 2018 with about 1,000 somewhat deeper earthquakes. and of very little magnitude. The last time it happened was in July 2020 when 682 earthquakes were detected and 160 could be located. What is happening now is the most intense seismological activity that the island has experienced since the Teneguía erupted in 1971. The Teneguía erupted on October 26 and ended on November 18 of that same year.