In October, 50 years of the last eruption of Old Summit in La Palma will be fulfilled. Half a century later, the most active volcano of the Canaries - with the permission of El Teide- maintains in Vilo to the inhabitants of four municipalities of this small island of 85,000 inhabitants, since on Saturday, September 11, a new surge of earthquakes that has been Culminated this Sunday with a great eruption. Most of the earthquakes registered throughout the week were low magnitude, provoked by the accumulation of 11 million cubic meters of magma that was trying to go to the surface.
From dawn on Saturday to Sunday, new replicas of up to 3.8 magnitude have caused that the volcano finally enter eruption around 15:15 on Sunday. There are five municipalities on alert and people with reduced mobility have been evacuated throughout the day.
The traffic light has changed from the red yellow, the level of greatest risk that corresponds already with the maximum alert, and that it would imply, in theory, an imminent danger for the population, provided that the preventive measures are not followed and nobody approaches the volcano . Volcanic traffic light is an alert system consisting of four levels, indicated with four colors (green, yellow, orange and red). The plains of Aridane, Fuencaliente, the passage and deck are the most affected locations for this rash.
Before it produced the eruption, more than 20,000 tremors have been counted throughout the week. Those who have a very low magnitude are recorded, but they are not studied in detail, as detailed on Thursday in telephone conversation since Santa Cruz de Tenerife the Vulcanologist David Calvo, spokesman Delinological Volcanological of Canarias (Involcan). Precisely as we talked, on Thursday at noon, an earthquake of 3.1 occurred.
Last Tuesday, the earthquake of greater magnitude was recorded since the wave of earthquakes began, 3.5. According to Thursday the Scientific Committee of the Special Civil Protection Plan and Emergency Attention Plan for Volcanic Risk, was "expected that there are more earthquakes senses of greater intensity". This has happened, finally, on Sunday, with several replicas superior to 3.
As a bald review, "we are facing the tenth seismic swarm suffered by the palm since 2017". With the term seismic swarm, geologists call a large number of earthquakes that occur at the same point for a short period.
"This seismic swarm has occurred because a volume of magma is ascending from the depth, probably from the upper mantle, to the surface. In its attempt to break the terrestrial crust, it deforms the surface and generates many earthquakes," says this expert.
The earthquakes of the previous days to eruption have been quite superficial, at depths between 1-5 km. On Sunday, they have been given only one kilometer of depth, that is, practically next to the surface.
In addition, the terrain was doubled in just one day in the middle of the week, going from the six centimeters accumulated until Wednesday at 10 centimeters measured on Thursday, when the General Directorate and Emergencies of the Government of the Canary Islands decided to keep the Volcanic traffic light.
"The deformation means that the terrain is becoming on the surface part of the earth's crust as a result of the intrusion of the volcanic magma. It is as if you folded a bar of bread or a grain came out," compare Pablo Gabriel Silva, Geologist of the University of Salamanca, to explain what scientists will call volcanic. "It is one of the precursor phenomena of the eruption, it also occurred in the underwater crisis of the iron in 2011, although the deformation of the land reached 40 centimeters," he reviews.
"The soil is getting up, as if the island was growing," Calvo said last Thursday, when the deformation of the 10-centimeter terrain was already "significant".
"The normal thing is that before an eruption the rise of magma will break zones of the crust and generate earthquakes as it is happening now. So that the magmatic box is definitely broken and up to the surface should be a higher magnitude earthquake, of 4.5 or 5 approximately, or maybe it does not come to break. We have to wait, "Pablo Gabriel Silva coincided.
And if any volcano is unpredictable, the characteristics of this monster of the palm make their evolution even more uncertain. "Old summit is not a volcano to use, it is uncomfortable and by difference of the teide (in Tenerife) or Etna (in Sicily), it does not have a single crater. It is a succession of small volcanoes and in the case of eruption, the Lava can come out for any of his craters, "explains David Calvo.
The Old Summit Natural Park occupies some 7,500 hectares and covers six municipalities whose destination depends on volcanic activity. It was created in 1987 precisely to preserve them with volcanic cones and castings of the different eruptions that occurred in the area from prehistory, as well as its forests of Pinar Canario and Laurisilva.
Both the palm and the iron, which are the younger Canary Islands, are in the growth phase, have volcanoes and there must be eruptions
In the days before that last eruption of 1971, several earthquakes also made the island of La Palma tremble until on October 26, Old Summit Rugir again. The show of fire in Teneguio - as the inhabitants call that part of the volcano, which is always the same - was recorded by the cameras and although it was not destructive, it did cause a deceased by inhalation of smoke. It was one of the most intense eruptions since 1677 because there was another in 1949 that razed fields of cultivation and homes after the passage of volcanic lava.
In 2017, a new period of seismic activity began as it happens in volcanic areas, is intermittent and unpredictable. But as Calvo points out, yes they are sure that as there have been other eruptions in the past, there will be new eruptions in La Palma, although they can not find out when.
"Both the palm and the iron, which are the younger Canary Islands, are in phase of growth, have volcanoes and there must be eruptions," says Silva, who recalls that the only Canarian Island in which there has been no recent volcanism is La Gomera.
Date Of Update: 21 September 2021, 15:11
