LAS PALMAS DE GRAN CANARIA – No one dares to rule out the possibility of a volcanic eruption on the Canary Island of La Palma. The likelihood seems to increase on a daily and even hourly basis. Almost 3,000 seismic movements have been recorded since Saturday.
The geological activity of the subsoil on the island has been unusually high for days. The heaviest of those quakes on Tuesday morning in the municipality of El Paso measured 3.5 on the Richter scale. Authorities have now issued a pre-alarm for a possible eruption.
Another dimension
However, the detection of small earthquakes is something common in La Palma every year. Although the situation began to take on another dimension last Saturday morning. This was when a “seismic swarm” began, consisting of hundreds of telluric movements, which continues until today.
Residents felt the strongest quake on Tuesday at 6 am. The epicentre was at a depth of nine kilometres. In addition, three other seismic movements with a magnitude of 3.1 have been recorded.
The earthquakes are observed at depths ranging between eight and eleven kilometres in the municipality of Tazacorte and also in the whole area of Cumbre Vieja, the volcano that dominates the landscape of the above-mentioned island. This includes the municipalities of Mazo, Fuencaliente, Los Llanos de Aridane and El Paso.
Significant change in activity
The Vulcanic Institute of the Canary Islands finds that the current seismic swarm recorded on La Palma represents a significant change in the activity of the Cumbre Vieja volcano. According to them, this is related to a process of magmatic intrusion into the crust of the island.
As a result of the situation, authorities have declared a pre-emergency state over a possible volcanic eruption. The Volcanological Institute of the Canary Islands (Involcan) points on social media that the Cumbre Vieja volcano has experienced 10 seismic swarms in recent years, including the one that started last Saturday. The previous ones were in 2017, 2018, five in 2020 and three so far in 2021).
Seismicity may increase in next few days
The depth of the previous seismic series varied between 20 and 30 kilometres, deeper than it is now. That is why the volcanic traffic light has also changed from green to yellow. Involcan does not rule out that seismicity will increase in the coming days.
According to Involcan, its geochemical monitoring programs for volcanic surveillance on La Palma have made it possible to detect in 2020 the highest helium-3 emission value observed on La Palma over the past thirty years.
In fact, the National Geographic Institute considers the event currently taking place to be the most significant since the Teneguía eruption on La Palma in 1971, which was also the last volcanic eruption in Spain.
According to María José Blanco, director of the National Geographic Institute in the Canary Islands, magma that has penetrated beneath the volcano has raised the ground by an inch and a half. This move is often used as a harbinger of a possible volcanic eruption, but Blanco says in El Día, la opinión de Tenerife, the elevation would have to be much higher to cause an explosion in a short time. Based on that, Blanco basically rules out that this could happen any time soon. “There will be an eruption, but it is not imminent.”
Doomsday scenario about mega tsunami
In October 2017, a seismic swarm on La Palma prompted the British press to fear a mega-tsunami following a possible eruption of the Cumbre Vieja volcano. The Daily Star based this on an existing doomsday scenario. In 2001, geologists stated that the volcanic island of La Palma is so unstable that one of its flanks could collapse into the sea in a volcanic eruption. This would create a huge wave that would continue to grow on its way. And could even reach parts of Spain, Portugal, Great Britain and even the east coast of the United States. If this happened, there would be disastrous consequences.
The probability of an eruption of the volcano Cumbre Vieja is present and can be demonstrated statistically. Since 1730, an eruption of this volcano has occurred once every eighty years. The last eruption was in the 1970s, so statistically, the now-dormant volcano will become active again in a few decades.
In 2006, however, the Dutch professor of hydraulic engineering, Jan Nieuwenhuis tempered the scenario somewhat in the September edition of Delft Outlook with the conclusion that La Palma is much more stable than is generally assumed. In addition, the volcano is simply not big enough to disintegrate. At least not yet. It will take at least another 10,000 years for the southwestern flank from the island could fall into the sea and cause a mega-tsunami. And that could only happen in an exceptional combination of circumstances. “With what we know now, so many things would need to go wrong at once. Therefore, a disaster seems very, very unlikely,” said Nieuwenhuis.
