Science

Nieves Sánchez, geologist: “The La Palma volcano may be reactivated”


Nieves Sánchez Jiménez, investigadora del Instituto Geológico Minero de España
Nieves Sánchez Jiménez, researcher at the Geological Mining Institute of Spain PACO PUENTES (EL PAÍS)

Nieves Sánchez has seen the terrible destruction of which a volcano is capable. In 2018 this researcher from the Geological and Mining Institute of Spain (IGME-CSIC) traveled to the area devastated by the Volcán de Fuego in Guatemala, one of the deadliest eruptions in recent years. His narration makes the hair stand on end. “The volcano hit a very poor area,” he recalls. “There was a pyroclastic flow, a cloud of gas and rock at a very high temperature that moved very quickly. The inhabitants of the area thought it was a lava eruption and they left their houses to see it arrive. The cloud took them ahead. It is not known how many people died, there are only approximate calculations based on the number of electricity meters, but there many people live without it. ”

Sánchez arrived long after all that happened. His goal was to oversee and refine a rudimentary early warning network to prevent further tragedies. It is simply a radio system so that vigilantes in the highlands can alert those who live in the valley that a new flood or eruption is coming. This same year, Sánchez traveled on an EU and UN mission to the Caribbean island of San Vicente, where the La Soufrière volcano covered everything under tons of ash. There was so much that the authorities did not know what to do with it.

For a few weeks, Sánchez has been on La Palma monitoring near the Cabeza de Vaca volcano. This Madrid geophysicist from 52 years has 10 studying volcanism in the Canaries from the IGME center in Gran Canaria, where he resides. Now he works at the makeshift forward command post at the Caldera de Taburiente National Park visitor center. Where there used to be tourists, now there are civil guards, military and scientists working shoulder to shoulder.

Sánchez represents the IGME in the scientific committee from Pevolca. In this interview, he draws the robot portrait of the volcano that scientists have drawn after the first analyzes of lava, ash and gases. “The volcano has no signs of ending tomorrow or the day after or in a week,” he warns.

In the last hours, the lava flows have become more fluid. IGME geologists have detected “erratic blocks” the size of three-story houses pouring down. “Under the top of the crater, a larger and larger lake of lava is forming, sometimes overflowing. This lava lake is breaking the upper rims of the crater and we think those blocks are proof of that. As long as the lava keeps them afloat, they will continue moving down the slope ”, highlights Sánchez.

Question.

Why do volcanoes attract you?

Answer. A volcano is the greatest visual stimulus I know of. It makes you suddenly understand that the Earth is alive. It is a real manifestation that something is moving within you. It is something great and impossible to control. You cannot turn it off or plug it. The only thing you can do is move away. It is something that does not happen often, like floods, fires and even earthquakes, which we are more used to. As quiet as it is, a volcano is shocking.

P . What did you feel the first time you saw the Cow’s Head erupting?

R. It was night. I stayed without breath. The next thing was to think: where the lava is coming down there are people, houses. And you get to work. In our case, this means giving the best possible advice to the authorities who have to manage the emergency.

Q. Do politicians ask you many unanswerable questions?

R. Yes. The usual questions are when will the lava stop coming out and when will people be able to resume their normal lives. It is logical. The problem is that volcanology is not an exact science. There are many variables that we do not control and others that we do not even know. We know more and more and have better instruments, but even so it is often impossible to know the result. We do emergency geology.

P. What robot portrait of this volcano does the IGME manage?

R. Despite the enormous damage it has done, we are facing a very normal eruption. It fits in with all the previous ones that have been on La Palma. It is a strombolian eruption with more or less violent explosive pulses, emitting lavas. Everything is very similar to what we know from the chronicles written since the fifteenth century. The big difference is that we now have a much more populated island. The vulnerability is much higher because of this.

In the Canary Islands, most people are not aware that they live on active volcanic islands

P. Do you think people are aware of this?

R. In the Canary Islands, the feeling is that people have very little historical memory of what a eruption. The vast majority are not aware that they are active volcanic islands. When I arrived in Gran Canaria they told me that there were no volcanoes, that where they were. But the whole island is volcanic. All the islands. That surprised me. The last terrestrial eruption was on La Palma in 1971 and on this island you find people who say that there are no eruptions here from recently. Only those who suffered them directly mention them. Sometimes these things have to happen for people to remember where they live. You have to be aware of the risk you take living here.

Q. In recent days there have been strong earthquakes, how do you interpret them?

R. The volcano has no signs of ending tomorrow or the day after or in one week. The activity changes a lot from day to day, the cone is built first and then destroyed. In the last few days we are seeing deeper seismicity again. This can mean a new influx of magma into the system. It could be reactivating, although we have to wait to confirm it with observation from the outside. My opinion is that it will continue to erupt for a while, we do not know how much nor will we be able to tell until the earthquake and ground deformation patterns change. In some GPS we have observed a stabilization of the deformation, but not a clear decrease. We depend on whether that new magma inflow continues or stops.

We believe that the volcano has three magma reservoirs

P. Where does the magma from the volcano come from?

R. With the data we have, it seems that there are three reservoirs. The deepest would be about 30 miles underground. This is where material may be melting and is the main deposit. There is another intermediate about 10 kilometers and the most superficial would be about four kilometers. Magma can go from one to another or come directly from the deepest to the surface. This is what we think based on the thousands of earthquakes recorded at different depths from 2017 until now and the type of lava that is coming out .

P. Until the reservoirs are emptied, won’t the eruption end?

R. It is not a question of being emptied, but of the magma having enough strength to keep coming out. This depends on the gases. Magma has minerals, rocks, and gases. The gas is dissolved in the magma. As it ascends, it separates. It is like a bottle of Coca-Cola. If it is closed, it is just a liquid. But if you shake it and open it, it becomes an explosion, because the gas bubble has separated from the liquid. If they have a lot of gas, the bubble makes the lava more explosive. When the magma can no longer rise, it will stay there.

P. One of the most surprising things about the volcano is its roar. Why is this happening?

R. It’s like the volcano is choking. The gas exits through the main cone duct at the top. The lava comes out through lower mouths, very fluid. The sound we hear is the degassing of magma. Every time this happens, pyroclasts come out with great violence. Some fall within a kilometer or two of the crater, but others rush back into the crater and obstruct it. Every time gas comes out again, it must push the cap and in doing so, tremendous explosions and pyroclastic rain are produced. When the volcano sounds like a bellows, it is due to degassing.

Q. What would happen to us if we were on the edge of the volcano’s crater?

R. You would volatilize. It’s like a car bomb. Does the explosion, the shrapnel, the blow kill you? It is impossible to know. Here it is the same with poisonous gases, extremely high temperatures and the constant bombardment of pyroclasts. If you’re there, it’s over.

P. Volcanoes can cause tremendous destruction, but they are also engines of life.

R. A volcano is a catastrophe, but also an opportunity. It can cause many losses of human and material life, but over the years they become an opportunity because the ashes of the volcanoes make the fields very fertile. In fact, they are used as agricultural fertilizer. It is also a first-rate tourist resource, yes, in a long time. Volcanic terrains are like this: catastrophic in the short term and, over time, promising.

P. How long will it take to climb the crater when the eruption ends?

R. It could be years. If you go down to the crater of Teneguía and put your hand on the ground, it is still warm, and 50 years have passed . The priority now is not to climb the volcano, but to recover what was destroyed and the people who have lost their homes.

We must analyze in which areas should not be built based on past eruptions and avoid them

P.

How long can it take to remove the laundry?

R. It depends on the material that comes out, how many casts are accumulated and its thickness. The interior of the laundry is very hot, especially in the area near the crater. It also depends on the volcanic tubes that form inside. It will be necessary to analyze it and decide which areas can be accessed and which are not. Which roads are recoverable and which must be made new. The interior of the casting maintains a lot of heat, especially in the area near the crater.

P. Is it a mistake to build as it has been built on La Palma?

R. The past bull is easy to talk about. What we should do is take volcanic processes into account in territorial planning. Now it’s done, but 50 years ago, no. Not here or anywhere. Because, where should we have prohibited building? In the entire southern part of the island, which is the active zone? It’s very complicated. We should not think so much about whether it was a mistake. There was probably no other option. The important thing is what is done from now on. Analyze in which areas should not be built based on past eruptions and avoid those areas. You have to start over and take the risk of living on a volcanic island. This is not like a river that has a zone flood. We don’t know where the next volcano will come out.

P. Is anything positive going to come out of this eruption?

R. Now it is very difficult to see. Affected people just want to go home. A flood passes and you can return to your house, clean it, recover it. But when a wash runs over you, you don’t have land or a house or a place to return to. People who have lost everything cannot be told that anything good will come of it. What good is a farm covered in lava? The houses have been blown up. They burn and disappear. The only good thing that can happen now is that the eruption ends. The only important thing is that you do not forget the risk of living on a volcanic island. May we all learn to live with volcanoes. We cannot do without them and we cannot leave. You have to take the risk. And eventually good things will come out of all this.

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