Those who have already seen it coming always emerge after a shocking crisis: those who are already popularly known as the
captains a posteriori
. There are also those who advertise many things and it is easy for them to get one right. And then, those who had complete information and quality data to anticipate that something could happen. However, in January, a team of experts from Spanish and international scientific institutions published a study that, read now, draws attention for its success. The magma, he said, was seeping through the cracks under the southern part of the island of La Palma and a volcanic reactivation was taking place, seeking an outlet under Cumbre Vieja.
There were obvious clues for anyone.
In October 2017, there was a seismic swarm of 122 small mini-earthquakes, the first signal since the Teneguía was turned off in 1971. Then, in 2018, another 79 earthquakes.
But something strange was happening, according to José Fernández, head of the remote sensing laboratory at the Institute of Geosciences (IGEO), supported by the CSIC and the Complutense University.
"They had not detected deformation and that seemed strange to us after the swarms, and we wanted to analyze it by other means," he explains.
The strange thing was that there was seismicity and not a certain bulge, although minimal, that indicated pressure of the magma under the crust.
"We saw that the reactivation process must have been around 2009 and 2010, and after studying the evolution until 2020, we discovered that it was accelerating"
José Fernández, Institute of Geosciences
They used data from satellites, as is being done now during the crisis, to
whether the ground had swelled in recent decades.
"We saw that the reactivation process must have been around 2009 and 2010, and, after studying the evolution until 2020, we discovered that it was accelerating," he says.
Their data suggested that small amounts of magma were accumulating to a depth of 8 to 10 kilometers, interacting with aquifers and increasing pressure in the area.
But that was not enough: for there to be a reactivation, many other parameters have to be aligned.
"We wanted to see if we could link everything with geochemical anomalies, gases, which would indicate that it was a volcanic process," recalls the scientist.
Researcher José Fernández, from the Institute of Geosciences.
"It all matched", summarizes Fernández, "it matched gas anomalies, it matched geochemistry, it matched geodesy." Combining the pattern of surface deformation, they observed that this area began to move from 2008 to 2020, with a deformation in the Aridane Valley, where the 1949 eruption occurred. On that occasion, the activity originated for more than a decade before, with some tremors in 1936. On this occasion, the eruption occurred about eleven years after the start of the reactivation.
An important detail, which Fernández insists on: in the Canary Islands area, only 20% of the reactivations end in an eruption, as in 2004 and 2005 in Tenerife. "This study also allowed us to know why it is happening on La Palma and not on El Hierro or Tenerife," says the IGEO researcher. In their analysis, published in
together with researchers from Spanish, American and Italian and Canadian universities, a very detailed X-ray of the island is achieved: The northern area is the oldest, where the island was formed with volcanic activity, while the south is younger and more agitated. There was magma that took advantage of the fractures that have not closed since 1949 (yesterday, in geological terms).
The study "had no impact, it went unnoticed," recalls Fernández, in part because it was published in the middle of a tsunami of COVID infections after Christmas. But they informed the National Geographic Institute (IGN) and the Volcanological Institute of the Canary Islands (Involcan). His work “will help to know how the next reactivations may be”, believes Fernández: “It is important to measure when it seems that nothing is happening, so we can work years in advance, at least months. You need very long-term surveillance ”. And he points out a great advantage of these investigations: "For the first time we are going to be able to do a study from the beginning to the end, thus we are going to improve the knowledge of volcanism in the Canary Islands".
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