El Hierro: the volcano awakens
On the island of El Hierro, they have been looking at the sea for a month. The daily earthquakes and the gas and lava flows that flow out of the water have made it clear that the El Hierro volcano is awake. Awake, yes; but it is not yet clear how much activity and how it will behave, and scientists closely follow its evolution.
Miren Mendia is a geologist and professor at the University of the Basque Country. During our conversation with him, we have clarified a number of doubts.
Jungle Palace, Elhuyar Foundation: Volcanoes are very visible phenomena and easily attract everyone’s interest, and even more when they are close to cities. This is what is happening with the El Hierro volcano, but, Miren, from a geological perspective, what is the dimension of what is happening in El Hierro right now?
Miren Mendia, Geologist UPV-EHU: We rarely have the opportunity to see geological phenomena like this in person, so, at least on the scientific side, it's a very interesting thing, you can learn a lot. Because the processes that remain within the Earth cannot be seen, and when we have the opportunity to see them directly, well... from a scientific point of view, at least, it's incredibly interesting.
According to O.J.: And in the studies that are being carried out in El Hierro, what has attracted the attention of the scientists, above all?
More places to stay in M.M: We have very little data, that’s for sure. It takes time to extract and publish the data. Instead, what we see in the materials that are coming out right now is... we also see in the images some stones floating there in the water,... it is seen by taking these samples, with a white, inner part, and a dark, black, outer part. There seem to be two types of magma, one that is light, which we call acid, and the other that is dark, which is basic. And it's a pretty strange thing. It will shed light on what processes are happening there.
According to O.J.: What is the greatest danger in El Hierro right now?
More places to stay in M.M: Danger to the people. The danger is always for the people. The danger is that an explosive eruption will occur. We all remember what happened in Iceland last year. Such an eruptive column, with ash, gas, and being explosive. It is very close to where the inhabitants are, which would be the greatest danger. The worst thing that can happen.
According to O.J.: In that case, should the island be emptied, for example?
More places to stay in M.M: Yeah, and if it was too big, the other islands too.
According to O.J.: And what damage can this explosion cause to the atmosphere and water, for example?
More places to stay in M.M: Among these gases, in this eruptive column that comes out, in this mushroom-shaped column that we all have in mind, various materials, pyroclastic material, come out. Pieces of stone, small or larger, and gases. Of these gases, two are preferred: CO2 and SO2, carbon dioxide and sulfur dioxide. It hurts us, spills pollution into the atmosphere, and that's why it's harmful. The waters would be polluted, so would the sea water. But, depending on the size of the explosion, the resulting column may have a longer or shorter period of effect. If it’s not enough, diluting things for a few weeks or a couple of months will calm you down. Now, when large explosions occur, when 15 kilometers of pillars are formed, they reach the upper part of the atmosphere, in which case they can also affect the climate.
According to O.J.: At this moment we do not know how the volcano will evolve, but, in terms of technology, what resources do scientists have to know what is happening in this depth of 20 kilometers?
More places to stay in M.M: When making the prediction, different tools are used. The seismographs are the most used, they are made non-volitional. In general, in the Canary Islands, as an active volcanic place, they already have fixed seismographs. In a crisis like this, they also use laptops all over the island. Then, with this, small earthquakes are measured, which indicate the movement of the magma that is happening underneath, and it is deduced according to the signal they give if it is magma movement, if it is gas pressure, or what is happening. And this is called volcanic tremor. It's a very small, continuous signal of magnitude.
According to O.J.: It shows the movement of the magma.
More places to stay in M.M: And this shows the depth to which it is moving, if it is rising, because the magma rises slowly, in principle. So, the information that the experts extract from it is directly related to the movement of the magma that is underneath it. Then, other instruments are used: when the outer surface increases, or if there is a concussion on the surface, this means that this magma is rising to the surface, which is also measured with the apparatus. Those who are present are able to measure differences of four or five centimeters. It is also done through GPS and satellites, in addition to measuring changes in the composition of the gases. These places are very well studied and, in principle, the existing tools are adequate to predict what may happen.
According to O.J.: Given that some predictions can be made, what is expected to happen in the next few days?
More places to stay in M.M: I can't tell you, among other things, because I'm not there and I don't do it. But from what I read, they're afraid that this magma will move north. We must think that this magmatic chamber that El Hierro has under the surface is the same but larger, so that this magma will look for a place where it can go out. Now you have looked for a solution in the south, and you can look for it in the north, in the east or anywhere, or in the middle of the island.
According to O.J.: Right on the ground, right on the island?
More places to stay in M.M: They study the seismic Focos and where they are concentrated, to deduce whether they can go from here or from there. They're not exposed, and I don't know what's going to happen, which I can't say.
According to O.J.: Thank you very much, Miren
More places to stay in M.M: To you guys.
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