The eruption continues and, worst of all, it is unknown for how long. The lava, which moves slowly and relentlessly, has already occupied 166 hectares and has destroyed more than 300 buildings. Questions about the episode that is being experienced south of La Palma are multiplying and the scientific community asks for time to be able to analyze the data. A time that the population, straddling concern and curiosity, tries to fill in answers to an enigma, for the moment, unsolvable: How much magma is left in the guts of the volcano?
So far scientists have been able to give estimates of the volume of magma that could host Cumbre Vieja. However, they are mathematical models that are based on the analysis of what can be seen: the deformation of the ground. These days the island has suffered a bulging of the ground that already reaches 20 centimeters. There is still magma pushing hard under the surface.
“The deformation is decreasing very slowly, so we can guess that there is still a lot of material left,” says Juan José Rueda, a volcanologist at the National Geographic Institute (IGN). It is precisely this organism that, in the early days of the eruption, estimated the volume at 11 million cubic meters that could contain the volcano. The problem, says Rueda, is that at the same time that it expels lava, it is unknown if the mantle will continue to feed the eruption with magma.
Also, the volume inside and outside the surface can change. Right now, the estimated amount of lava emitted at 26 million cubic meters does not explain the amount of magma that was inside the volcano. The IGN researcher states that lava, when it leaves the volcano, changes its volume due to contact with the air and after explosions. “Not all the volume that is now above the ground is the same volume that was inside the volcano”, he adds, and since there is no meter at the mouth of the volcano, it is not known how much volume has come out. “The only way to infer it is through the deformation”, that when it starts to go down, “we will be in another phase” other than the eruptive one.
For Jesús Ibáñez, seismologist at the Andalusian Institute of Geophysics, there is a clear example: “It is as if you take a sheet and put a ball inside, the surface deforms and can give us an idea of how big it is”. However, it raises another question, and that is that the same ball it can be deeper and not bulge the ground so much. With magma, he assures, the same happens, “there is some uncertainty” and “we have to find a way to illuminate what is not transparent, which corresponds to the interior of the earth.”
The origin of magma
The experts, through the explosions, the lava flows, the deformation and the roar emitted by the volcano, illustrate a kind of sketch of what may be happening under the surface. This kind of X-ray explains the reason for the enigma with the magma of Cumbre Vieja and changes the question: Where does that magma come from?
Well, the experts consulted by EL ESPAÑOL explain that under the volcano there is an accumulation of magma that can be called a magmatic bag. This bag, in the shape of a ball, can be nourished with material from the mantle through a chimney. This is an ascent channel “where the magma can be accumulating in a downward extension of 20 kilometers,” says Ibáñez, who adds: “The magma is on a waiting list to be able to ascend”.
“This is just beginning,” says Rueda. And he says it with knowledge of the facts, because the deformation of the terrain has hardly diminished. “The problem we find is that once the magma comes out, we don’t know if the bag is still feeding back from the mantle.” In geology, he says, four days of eruption is a breeze.
The La Palma volcano, unlike others like El Teide, in Tenerife, does not have a magmatic chamber. Or, at least, there is no evidence. Different analyzes led to infer that the man from Tenerife had something like a constant magma reservoir that fed the volcano. As Ibáñez explains, “on El Teide there must be a magmatic chamber because it presents different types of magma for the same volcanic building structure”, something that does not happen with the palm tree.
“The detonations are still heard”
As it is, since Tuesday night, the beautiful island he is having a more explosive episode. The volcano expels the magma with greater violence and the lava continues to gushunceasingly, by the four active mouths of the eruption. David Calvo, Involcan spokesman, assures that “the situation remains the same, in an explosive phase and throwing a lot of ash”, which in some areas reaches a thickness of about three centimeters.
“In the next few hours, it will remain the same, because the detonations continue to be heard,” says Calvo, but this falls within the general dynamics of the volcano. And it is that it works in pulses, which can be altered or not depending on “if there is still rising magma,” explains Ibáñez. Moments of reactivation that can come later and prolong the eruption in time. “We do not know, but it is a plausible model,” says the seismologist.
The lava front that has already reached the Todoque neighborhood, in the municipality of Los Llanos de Ariadne, It is about 500 meters and, at certain points, reaches a height of 12 meters. Measurable and analyzable aspects by the scientific community deployed in the area. Rheology, the study of the viscosity and density of the lava, will allow, for example, to learn more about the evolution of the eruption.
The eruptive column that forms with the eruption is another aspect that experts try to quantify and measure through different technologies. At the moment, satellites such as the Copernicus Atmospheric Monitoring Service (CAMS) of the European Union anticipate that the plume of smoke, gases and ash will reach a maximum height of 5 kilometers. A figure not too distant from that offered by the Volcanological Institute of the Canary Islands (Involcan), which places the volcanic plume at 4.2 km above the eruptive mouth. According to Calvo, since the beginning of the eruption, “some 70,000 tons of sulfur dioxide (SO2)” would have been emitted into the atmosphere, although satellites could estimate higher figures when covering the part of the ocean.
While the volcanic surveillance continues, the latest information from the scientific committee and director of Pevolca show that one of the lava flows, the one to the north, has practically stopped and the other is advancing “very slowly”, about four meters along hour. This slowdown is normal since, when they move away from the emission center, it drags the material it encounters along the way, it is more viscous, it gets colder and colder, and it has to adapt to a flatter orography.
For the moment, in the short term, a response can only be obtained from what can be perceived by the senses. As Rueda concludes, seismology, deformation and the geochemistry or control of gases are three legs that scientists are focusing on these days to learn how the volcano can evolve. The problem, Ibáñez points out, is why we do not know, but “it is a very simple question”: “The interior of the earth is not visible and scientists need time to illuminate it”.
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